HomeMy WebLinkAboutResolution 2022-10 East WWTP Conceptual Design RESOLUTION NUMBER 2022-10
A RESOLUTION OF TILE CITY COMMISSION OF THE CITY OF WINTER
SPRINGS, FLORIDA, RELATING TO THE FLORIDA DEPARTMENT OF
ENVIRONMENTAL PROTECTION (I+DEP) STATE REVOLVING FUND
(SRF), ADOPTING THE CONCEPTUAL DESIGN REPORT FOR THE
IMPLEMENTATION OF THE EAST WATER RECLAMATION FACILITY j
IMPROVEMENTS; PROVIDING FOR THE REPEAL OF PRIOR INCONSISTENT
RESOLUTIONS,SEVERABILITY,AND AN EFFECTIVE DATE.
WHEREAS, Florida Statutes provide for loans to local government agencies to
finance the design, and construction of wastewater facilities; and the Florida
Administrative Code requires the City Commission to formally adopt a facilities plan
outlining necessary wastewater facility improvements to comply with State of Florida
fiinding requirements;
WHEREAS, the City of Winter Springs intends to adopt a more specific Facility
Plan for the East Water Reclamation Facility to apply for such financing; and
WHEREAS, the formal adoption of the proposed Conceptual Design Report for
the East Water Reclamation Facility is intended to guide the creation and preparation of
the Facility Plan required for the City of Winter Springs to participate in the State
Revolving Loan Fund Program and shall be the conceptual basis for the design and
construction of the East Water Reclamation Facility; and
WHEREAS, the City Commission of the City of Winter Springs, Florida agrees
with the findings and summary of necessary improvements as outlined in the Conceptual
Design Report for the purpose of designing and constructing a Water Reclamation Facility
to replace the existing East Water Reclamation Facility; and
NOW, THEREFORE,BE IT RESOLVED by the City Commission of the City
of Winter Springs, Florida as follows;
SECTION 1. FINDINGS
The foregoing findings are incorporated herein by reference and made a part hereof,
SECTION 2. ADOPTION OF THE CONCEPTUAL DESIGN REPORT.
The City of Winter Springs Florida, is authorized to and does hereby adopt the proposed
Conceptual Design Report for the Cast Water Reclamation Facility, attached hereto as
Exhibit A.
The City Manager is hereby designated as the authorized representative to provide the
assurances and commitments that will be required by the Conceptual Design Report,
The City Manager is hereby designated as the authorized representative to execute the
Conceptual Design Report, which, in conjunction with the Wastewater Master Plan
adopted via Resolution 2022-08, will become the foundation of all activities related to the
wastewater facility improvements. The City Manager is further authorized to represent the
City in carrying out the Conceptual Design Report. The City Manager is authorized to
delegate responsibility to appropriate City Staff to carry out technical, financial, and
administrative activities associated with the Conceptual Design Report.
The legal authority for adoption of this Conceptual Design Report is pursuant to the City
Charter, City Code of Ordinances, and the Laws of the State of Florida.
SECTION 3, REPEAL OF PRIOR INCONSISTENT RESOLUTIONS.
All Resolutions or part of Resolutions in conflict with any of the provisions of this
Resolution are hereby repealed.
SECTION 4. SEVERABILITY,
If any section or portion of a section of this Resolution proves to be invalid., unlawful, or
unconstitutional, it shall not be held to invalidated or impair the validity, force, or effect or
any other section or part of this Resolution.
SECTION 5. EFFECTIVE DATE
This Resolution shall tape effect upon its approval and adoption by the City Commission.
APPROVED AND ADOPTION THIS 2nd DAY OF MAY,2022.
CITY COMMISSION.
CITY OF WINTER SPRINGS,FLORIDA
N� t/
(7,3 Y ce KEVIN MC ANN,MAYOR (SEAL)
ATTEST: APPROVED AS TO FORM:
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CHRISTIAN GOWAN,CITY CLERK ANTHONY A. ARGANESE,CITY ATTORNEY
City of Winter Springs
East Water Reclamation Facility
CONCEPTUAL DESIGN REPORT
April 2022
337
City of Winter Springs
East Water Reclamation Facility
CONCEPTUAL DESIGN REPORT
April 2022
This document is released for the
purpose of information exchange review
and planning only under the authority of
Brian J. Graham, April 2022,
State of FL PE No. 44683.
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Contents
1.0 Introduction, Summary of Existing Facilities, and Wastewater Flow and
Load Projections 1
1.1 Introduction 1
1.2 Basis for Conceptual Design 1
1.3 Summary of Existing Facility 3
1.3.1 Existing Treatment Process and Effluent Disposal 3
1.3.2 Condition Assessment 5
1.3.3 Site Boundary and Contour Survey 5
1.3.4 Environmental Review 6
1.3.5 Odor Survey 8
1.3.6 Geotechnical Investigation 10
1.3.7 Wastewater Characterization and Population Flow Projections 10
1.3.8 Wastewater Flow and Loading Characterization 10
1.3.9 Population Projections 13
1.3.10 Proposed East WRF Design Capacity 14
2.0 Liquid Stream Alternatives Evaluation 15
2.1 Evaluation Overview 15
2.2 Selection of Liquid Stream Treatment Alternatives 15
2.2.1 Preliminary List of Potential Process Alternatives 16
2.2.2 Biological Nutrient Removal to Achieve AWT 18
2.2.3 Potential AWT Treatment Alternatives 19
2.3 Descriptions of Proposed AWT-Capable Treatment Alternatives 21
2.3.1 Five-Stage Activated Sludge BNR (5-Stage BNR) 21
2.3.2 Membrane Bioreactor 22
2.3.3 Sequencing Batch Reactor (SBR) 25
2.3.4 Aerobic Granular Sludge – AquaNereda® 27
2.3.5 Ballasted Activated Sludge – NuvodaTM 29
2.3.6 Integrated Fixed-Film Activated Sludge 31
2.4 Structured Decision Analysis 33
2.4.1 Process Evaluation Criteria and Sub-Criteria 33
2.4.2 Paired Comparison Results 35
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3.0 Shortlisted Alternatives Evaluation 37
3.1 Objectives 37
3.2 Conceptual Design Criteria 37
3.2.1 Influent Flows and Loads 37
3.2.2 Regulatory Requirements 40
3.3 5-Stage BNR Alternative (“Buildout” Scenario: 2.1 mgd with AWT) 40
3.3.1 Process Design 40
3.3.2 Conceptual Site Layout 45
3.3.3 Hydraulic Considerations 47
3.4 MBR Alternative (“Buildout” Scenario: 2.1 mgd with AWT) 49
3.4.1 Process Design 49
3.4.2 Site Layout 54
3.4.3 Hydraulic Considerations 56
3.5 Common Processes and Shared Facilities 56
3.5.1 Odor Control Technology 56
3.5.2 Chemical Systems 56
3.5.3 Reclaimed Water Storage and Reject Storage 59
3.5.4 Solids Handling 60
3.5.5 Potential Industrial Load Influences 61
3.6 Conceptual Level Cost Estimates (“Buildout” Scenario) 61
3.6.1 Cost Estimating Accuracy 61
3.6.2 No Action Alternative 61
3.6.3 BNR and MBR Capital Conceptual Cost Estimates 62
3.6.4 Annual O&M Conceptual Cost Estimates 62
4.0 Final Recommendation 66
4.1 Recommended Alternative 66
4.2 Recommended Plant Capacity and Treatment Standard 66
4.3 Recommended Conceptual Site Layout and Cost Estimate 67
4.4 Funding Considerations 70
4.4.1 SRF Funding 70
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Appendices
Appendix A Existing WRF PFD
Appendix B East WRF Survey
Appendix C Ecological Assessment and FNAI Tracking List
Appendix D Odor Control Assessment
Appendix E CWSRF Planning Document Requirements Checklist
Tables
Table 1 East Permit Renewal Effluent Disposal Site/Water Quality Requirements
Request 4
Table 2 East WRF Hydrogen Sulfide Monitoring Summary 9
Table 3 East WRF Historical Monthly and Annual Average Daily Flows 10
Table 4 East WRF Influent cBOD5 and TSS Concentrations and Loads 12
Table 5 Winter Springs Population and Flow Growth Factors 13
Table 6 5-Stage BNR Fact Sheet 22
Table 7 Membrane Bioreactor (MBR) Fact Sheet 23
Table 8 Sequencing Batch Reactor (SBR) Fact Sheet 26
Table 9 Aerobic Granular Sludge (AGS) Fact Sheet 28
Table 10 Ballasted Activated Sludge (BAS) Fact Sheet 30
Table 11 Integrated Fixed-Film Activated Sludge (IFAS) Fact Sheet 32
Table 12 Major Evaluation Criteria and Corresponding Sub-Criteria 34
Table 13 Major Evaluation Criteria and their Relative Importance 35
Table 14 East WRF Influent Design Flow and Mass Load Peaking Factors 38
Table 15 Conceptual Influent Design Wastewater Flows and Loads 39
Table 16 Headworks Design Criteria for 5-Stage BNR 41
Table 17 Secondary Treatment Design Criteria for 5-Stage BNR 42
Table 18 Filter Design Criteria for 5-Stage BNR 43
Table 19 Chlorine Contact Chamber Design Criteria for 5-Stage BNR 44
Table 20 Headworks Design Criteria for MBR 49
Table 21 Secondary Treatment Design Criteria for MBR 50
Table 22 Chlorine Contact Chamber Design Criteria for MBR 52
Table 23 MBR Chemical Cleaning System 53
Table 24 Supplemental Carbon Storage and Feed Design Criteria 58
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Table 25 Alum System Design Criteria 58
Table 26 Solids Handling Design Criteria 60
Table 27 AACE International Guidelines for Cost Estimating Accuracy 61
Table 28 5-Stage BNR Conceptual Capital Cost 63
Table 29 MBR Conceptual Capital Cost 64
Table 30 Conceptual Annual O&M Cost Comparison 65
Table 31 1.5 mgd BNR Conceptual Capital Cost 69
Figures
Figure 1 Existing East WRF Process Flow Diagram 3
Figure 2 East WRF Site and Contour Survey 6
Figure 3 East WRF Environmental Survey Area 8
Figure 4 OdaLog Installation Locations at East WRF 9
Figure 5 East WRF Annual Average Daily Flows 11
Figure 6 East WRF Historic Monthly cBOD5 and TSS Loading 12
Figure 7 East WRF Flow Projections 14
Figure 8 Overview of Biological Treatment Technologies for Nitrogen and
Phosphorus Removal from Municipal Wastewater 17
Figure 9 Biological Treatment Technologies for Achieving AWT in Municipal
Wastewater 20
Figure 10 5-Stage BNR Process Flow Diagram 21
Figure 11 Membrane Bioreactor (MBR) Flow Diagram 23
Figure 12 Sequencing Batch Reactor (SBR) Process Flow Diagram 25
Figure 13 Aerobic Granular Sludge (AGS) Process Flow Diagram 27
Figure 14 Ballasted Activated Sludge (BAS) Flow Diagram 29
Figure 15 Integrated Fixed-Film Activated Sludge (IFAS) Flow Diagram 31
Figure 16 Process Alternative Ranking Using Weighted Criteria 36
Figure 17 5-Stage BNR Conceptual Site Layout (2.1 mgd with AWT) 46
Figure 18 Hydraulic Profile for the 5-Stage BNR Alternative 48
Figure 19 MBR Conceptual Site Layout (2.1 mgd with AWT) 55
Figure 20 1.5 mgd Conceptual BNR Site Layout (1.5 mgd) 68
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Abbreviations
AADF annual average daily flow
AC acre
AGS aerobic granular sludge
alum aluminum sulfate
AWT advanced wastewater treatment
BAS ballasted activated sludge
BNR biological nutrient-removal
BOD biochemical oxygen demand
Carollo Carollo Engineers, Inc.
CAS conventional activated sludge
CBOD5 5 day carbonaceous biochemical oxygen demand
City City of Winter Springs
cf cubic feet
cfm cubic feet per minute
cfs cubic feet per second
EBPR enhanced biological phosphorus removal
EPA Environmental Protection Agency
EQ equalization
F.A.C Florida Administrative Code
FDEP
FOG
Florida Department of Environmental Protection
fats, oils, and grease
ft feet
gpm/ft2 gallons per minute per square foot
HLD high level disinfection
HRT hydraulic retention time
IBC intermediate bulk container
IFAS integrated fixed-film activated sludge
IMLR internal mixed liquor recycle
lb/d pounds per day
MBR membrane bioreactor
MDF maximum daily flow
MG million gallons
mg/L milligrams per liter
mgd million gallons per day
MLSS mixed liquor suspended solids
MMADF maximum month average daily flow
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O&M operations and maintenance
PHF peak hour flow
psig pounds per square inch, gauge
RAS
RFI
return activated sludge
request for inclusion
rbCOD readily biodegradable chemical oxygen demand
SBR sequencing batch reactor
SCADA supervisory control and data acquisition
scfm standard cubic feet per minute
SFAS step feed activated sludge
SHT sludge holding tank
SRT sludge retention time
SWD side water depth
TDH total dynamic head
TMP transmembrane pressure
TN total nitrogen
TP total phosphorus
TRC total residual chlorine
TS total solids
TSS total suspended solids
WAS waste activated sludge
WRF water reclamation facility
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EXECUTIVE SUMMARY
The City of Winter Springs owns and operates the East Water Reclamation Facility (WRF). The
facility is permitted for 2.012 mgd AADF by the Florida Department of Environmental Protection
but currently experiences flows at approximately half this capacity. The East WRF was originally
constructed in the mid-1970s and has consequently reached the end of its useful life, requiring
both replacement and modernization.
Carollo and Wekiva Engineering conducted assessments of the East WRF as part of this project
and the priority repairs projects over the past year and concluded that no major component has
permanent value worth restoring. While some existing infrastructure and minor components
may be rehabilitated and reused, they generally only serve temporary purposes and have no
permanent value.
Based on the condition of the current facility, this CDR focuses on the construction of new
replacement of the East WRF. Specifically, the goal is to conceptualize a new facility which can
meet current and future water quality requirements while planning for growth over decades to
come. This facility should also be built for resiliency and reliability, such that the City does not
experience the current facility challenges again.
To conceptualize the future facility, a boundary survey, ecological assessment, and odor study
were completed as part of this CDR. Carollo then performed an analysis of all liquid treatment
technologies to determine which treatment alternative best suits the City. As part of this
evaluation, Carollo performed the following:
• Prepared a working list of liquid-stream technologies proven to meet Advanced
Wastewater Treatment (AWT) standards,
• Performed a conceptual-level review of the selected liquid-stream process alternatives,
• Developed evaluation criteria to rank each of the process alternatives in terms of their
ability to meet the City’s values,
• Hosted a paired comparison exercise with a City-appointed selection committee for City
to apply a value (or weight) to each evaluation criterion, and
• Shortlisted two alternatives from the working list for further development and in-depth
analysis (i.e., conceptual site layout and capital/operational cost estimate).
The working list of liquid-stream technologies proven to meet AWT included:
• Five-stage activated sludge BNR (5-stage BNR).
• Membrane bioreactor (MBR).
• Ballasted activated sludge (BAS).
• Aerobic granular sludge (AGS).
• Sequencing batch reactor (SBR).
• Integrated fixed-film activated sludge (IFAS).
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The paired comparison exercise with the City-appointed selection committee, as well as the
decision analysis, resulted in the list of treatment alternatives below. The alternatives are ranked
from highest to lowest based on the City’s applied values:
1. Five-stage activated sludge BNR (5-stage BNR).
2. Membrane bioreactor (MBR).
3. Sequencing batch reactor (SBR).
4. Ballasted activated sludge (BAS).
5. Integrated fixed-film activated sludge (IFAS).
6. Aerobic granular sludge (AGS).
Conceptual designs, site layouts, and capital/O&M cost estimates were developed for the top
two scoring technologies: 5-stage BNR and MBR. The design flows and loads used to compare
the BNR and MBR conceptual designs and costs to provide a final recommendation correspond
to a true “buildout” scenario. This scenario represents what the City may require in the far-term
future, i.e., post-2045, in terms of quantity and quality. These far-term future needs include a
flow of 2.1 mgd AADF, and a production of AWT-quality effluent. However, a final
recommendation for a conceptual East WRF, sized for today’s needs, is later provided.
The conceptual capital cost estimates for the 5-stage BNR and MBR alternatives at “buildout”
(2.1 mgd with AWT) are approximately $48,082,000 and $53,922,000, respectively. The MBR
alternative proved slightly more costly than the BNR (as the MBR alternative requires additional
fine screening, flow equalization, increased chemical storage, etc.). An annual O&M comparison
shows that the MBR alternative is also more costly to operate and maintain, costing
approximately $150,000 more than the 5-stage BNR alternative on an annual basis. Class 5
accuracies were used to determine the conceptual cost estimates and have a 20 percent
contingency applied due to the conceptual level of design.
Both BNR and MBR are established technologies in the United States, with a track record of
successfully meeting stringent nutrient discharge limits. However, 5-stage BNR is known as the
“Gold Standard” of CAS technologies and is more highly implemented in Florida, creating a
large, local resource pool for operators to turn to when in-need of support. Additionally, the
5-stage BNR process is similar to current operations and does not require a high degree of
additional operator training. On the other hand, while MBR has a smaller footprint in comparison
to the 5-stage BNR, it requires a higher pumping/energy and chemical use, and more mechanical
equipment, which ultimately creates more required maintenance. Based on these non-economic
factors, as well as the conceptual capital cost estimates, it is recommended that the City select
the 5-stage BNR alternative as the proposed treatment process for the East WRF.
Limited growth is expected within the City of Winter Springs over the next 20 years. Results from
the population analysis indicated that 2045 flows may range anywhere from 1.04 to 1.43 mgd
AADF. Additionally, the “City of Winter Springs 2022 Wastewater and Reclaimed Water Master
Plan” prepared by Kimley-Horn projects that population growth within available parcels and
potential septic to sewer conversions may result in flows up to 1.49 mgd over the next 20 years.
Both projections are far less than the current permitted capacity of 2.012 mgd.
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Rather than designing, constructing, and paying for an oversized facility today, and
consequently having to operate and maintain the oversized facility, Carollo recommends that
the City “build for today but plan for tomorrow” (i.e., right-size the WRF for near-term growth).
To elaborate, since flows are not expected to surpass 1.49 mgd AADF in the next 20 years,
Carollo recommends that the proposed East WRF be designed for a capacity 1.5 mgd AADF,
while also allocating space onsite such that the capacity can be readily expanded to meet future
needs. Additionally, because AWT is not required today, it is recommended to phase the
construction process to ensure current treatment standards are being met but allow AWT
build-out to meet future requirements.
A proposed conceptual site layout for this 1.5 mgd scenario (to meet today’s treatment
standards) was developed. It is recommended that the City initially construct a facility based off
of this conceptual design and modify as needed to meet future quantity and quality needs,
ultimately to the full buildout scenario of 2.1 mgd with AWT (if required).
The conceptual capital cost estimate for the recommended 1.5 mgd East WRF is approximately
$34,792,000. By right sizing the East WRF for today’s needs, the City would save approximately
$13 million dollars, today, on capital costs, with additional savings on annual O&M costs. The
City would also have the flexibility, reliability, and redundancy to take basins offline, while still
operating efficiently and meeting effluent requirements.
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1.0 Introduction, Summary of Existing Facilities, and
Wastewater Flow and Load Projections
1.1 Introduction
The City of Winter Springs (City) owns and operates two Water Reclamation Facilities (WRF): the
East (FLA011068) and West (FLA011067) WRF. The East WRF consists of two separate package
wastewater treatment plants (WWTPs), known as WWTP No. 1 and No. 2. These plants were
constructed in the mid-1970s and early 1990s, respectively, and have a total combined capacity
slightly above 2 mgd. These plants, and the entire east facility, have reached the end of their
useful life and require replacement. Carollo Engineers, Inc. (Carollo) has been tasked with
assessing and summarizing the current facility, and further recommending two treatment
process alternatives for the City to incorporate in the design of their new WRF.
Rather than replacing the East WRF in-kind, the proposed plant process will be planned for the
future ability to meet more stringent treatment requirements and effluent criteria, which will
inevitably be required with future environmental regulations. The purpose of this Conceptual
Design Report (CDR) is to provide the City with two proposed treatment process alternatives for
the new East WRF, and a final recommendation with an associated conceptual design, site
layout, and cost estimate. This CDR will form the basis for the subsequent detailed design,
permitting, bidding, and construction phases of the new facility construction. Overall goals of
this project are to provide a new wastewater facility that is reliable, meets current regulations
with the ability to achieve future regulations, aligns with the City’s growth and associated
treatment needs, and emphasizes City values.
1.2 Basis for Conceptual Design
The East WRF currently operates as a secondary wastewater treatment facility under the Florida
Department of Environmental Protection’s (FDEP) domestic wastewater facility permit
No. FLA011068. The facility is permitted to treat annual average daily flows (AADF) of up to
2.012 mgd but experiences flows at approximately half of this capacity.
The existing treatment processes at the East facility provide the level of treatment required for
its effluent to meet the following water quality requirements under the current permit:
• A 5-day carbonaceous biochemical oxygen demand (cBOD5) concentration of less than
or equal to 20 milligrams per liter (mg/L), when calculated as an annual average.
• A total suspended solids (TSS) concentration of less than or equal to 5 mg/L for any
single sample.
• A total residual chlorine (TRC) concentration of 1 mg/L, minimum, for any single sample.
• A total nitrate, as nitrogen (NO3- – N) concentration of less than or equal to 12 mg/L for
any single sample.
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The FDEP sets forth the regulatory requirements for effluent discharges from wastewater
treatment facilities and addresses end-use effluent water quality standards. Effluent disposed via
public access reuse (PAR) has higher disinfection requirements compared to non-beneficially
discharged effluent. Furthermore, effluent that is discharged for groundwater recharge and
surface water discharges in protected watersheds typically require the achievement of the
highest level of wastewater treatment, known as Advanced Wastewater Treatment (AWT). AWT
is defined in F.S. 403.086 (4)(a) and requires that wastewater be treated beyond the secondary
state, providing an effluent that has annual average values, including:
• A 5-day cBOD5 concentration of less than or equal to 5 mg/L,
• A TSS concentration of less than or equal to 5 mg/L,
• A total nitrogen (TN) concentration, expressed as nitrogen, of less than or equal to
3 mg/L,
• A total phosphorus (TP) concentration, expressed as phosphorus, of less than or equal to
1 mg/L, and
• Received high-level disinfection (HLD) as stated in 62-600.440 Florida Administrative
Code (F.A.C.). HLD requires an effluent which meets the following criteria:
- Any single sample shall not exceed 5 mg/L TSS prior to application of a disinfectant.
- Any single sample shall not exceed 25 fecal coliform values per 100 mL of sample.
- On a monthly basis, 75 percent of the fecal coliform values shall be below the
detection limits.
- When chlorine is used for disinfection, a TRC of at least 1 mg/L shall be maintained
at all times and the minimum acceptable contact time shall be 15 minutes at the
peak hourly flow (PHF).
The current East WRF operations do not include disposal of treated effluent via any methods
that require AWT. However, there are strong indications that state regulatory agencies will enact
future regulations that will require the City to treat its effluent to achieve AWT standards. For
example, the City of Winter Springs is surrounded by protected watersheds defined by the
St. John’s River Water Management District (SJRWMD). Any treated effluent applied to these
protected watersheds must be treated to a higher standard, with stricter nutrient limits. Over
time as these protected watershed basins are expanded, it is logical to assume that in the
future, the City may be located within a protected watershed and will be required to treat any
site-applied effluent to the higher standard. Additionally, more stringent treatment standards
are required for Surface Water and Backup Discharges, which are application methods not
currently used by the City but may be in the future.
To summarize, while AWT is not required today, there are strong indications that it will be in the
future. It is recommended that when designing the new East WRF, the City plan for a facility that
does not necessarily meet AWT today, but has the foundation in-place to allow for future
modifications to do so. Consequently, the proposed conceptual designs outlined in this report
are intended to meet current effluent requirements with the ability to be readily modified to
achieve AWT, if required in the future.
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1.3 Summary of Existing Facility
A condition assessment, as well as various surveys and studies, were conducted to gather an
overall understanding of the facility and the condition of the existing components. The following
subsections summarizes the findings of these assessments and the current condition of the East
WRF.
1.3.1 Existing Treatment Process and Effluent Disposal
The East WRF is comprised of two separate package treatment plants (circular field-erected steel
tanks) originally designed to use an activated sludge process, known as contact stabilization, and
a third concrete tank dedicated to sludge thickening and holding (Digester No. 3). The treatment
units consist of a surge tank, influent screening, concentric aeration basins (made up of
reaeration and contact tanks), and a clarifier in the center. RAS is also part of the aeration
process and is provided using air lifts. The clarified effluent then flows from the treatment tanks
to the tertiary moving-bed filters (DynaSand® filters), and finally to the chlorine contact
chamber. A 0.18 million-gallon (MG) concrete sludge digester/holding tank, 3 MG covered
reclaimed water (RW) storage tank and combined 5.61 MG combined wet weather and reject
storage pond are all onsite components of the East WRF, as well. Solid residuals are stored in a
sludge holding tank (SHT) that is aerated for mixing and preventing septic conditions prior to
dewatering. Stored solids are dewatered using a mobile belt filter press and then hauled offsite
for processing. A process flow diagram (PFD) of the existing East WRF is included in Appendix A,
with a snapshot shown in Figure 1.
Figure 1 Existing East WRF Process Flow Diagram
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The East WRF supplies PAR-quality effluent to the City’s reuse service area for irrigation
purposes. To be considered PAR-quality, reclaimed water must have experienced secondary
treatment, contain no more than 5 mg/L total suspended solids (TSS), and achieve HLD. Effluent
that meets PAR quality but is generated in excess of customer demand (e.g., during heavy rain
events) is stored onsite at the facility in the GST, and combined wet weather / reject storage
pond. The City also has alternate disposal sites, including the Oak Forest Spray Field land
application site and Owasco rapid infiltration basin (RIB) which can accept 0.201 mgd and
0.61 mgd AADF, respectively. However, these alternate disposal sites are permitted under the
same reuse system, ultimately requiring the same effluent requirements as their primary PAR
disposal method (R-001). Therefore, any effluent that does not meet PAR quality is diverted to
the onsite reject pond – of which 2 MG of the total 5.61 MG is dedicated reject storage.
The current East WRF permit (No. FLA011068) expires in March 2022, and Carollo recently
supported the City on the completion and submission of the facility permit renewal. With the
renewal, the City requested the State to designate the Owasco RIB as a R-003 discharge location
and change the water quality/effluent requirements for discharge to this location. In doing so,
this site (R-003) would be permitted under a separate reuse system and used for disposal of
non-spec effluent which does not meet PAR standards. The East Permit would then match the
permit conditions for non-PAR discharges in the City’s West WRF Permit (FLA011067). These
non-par discharge quality requirements are shown below in Table 1.
Table 1 East Permit Renewal Effluent Disposal Site/Water Quality Requirements Request
Site ID Location Effluent Quality Requirement
R-001 PAR System
[cBOD5] < 30 mg/L(1)
[TSS] < 5 mg/L(2)
[TN] – Report
[TP] – Report
Fecal Coliform < 25 #/100 mL(3)
R-002 N/A(5)
[cBOD5] < 30 mg/L(1)
[TSS] < 5 mg/L(2)
Fecal Coliform < 200 #/100 mL(4)
R-003 Owasco RIBs
[cBOD5] < 30 mg/L(1)
[TSS] < 30 mg/L(2)
[NO3- - N] < 12 mg/L(2)
Fecal Coliform < 200 #/100 mL(4)
Notes:
(1) Monthly Average.
(2) Single Sample Maximum.
(3) Single Sample Maximum (Samples Collected 7 days/week).
(4) Monthly Geometric Mean (Samples Collected Weekly).
(5) The Oak Forest Spray Field has potable wells located within a 500-foot buffer surrounding the site, and consequently,
cannot accept non-PAR quality effluent (FDEP Rule 62-610.421 F.A.C.).
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1.3.2 Condition Assessment
Over the past year, Carollo has visited the East WRF numerous times, through which a condition
assessment of the existing unit processes was completed. Part of this assessment has also
included priority repairs to the current facility in order to maintain operation until the facilities
are permanently replaced. Since the facility was originally constructed in the mid-1970s (with an
expansion in the early-1990s), a majority of its components have reached the end of their useful
life and are visibly degraded/corroded. As a subconsultant to Carollo, Wekiva Engineering also
performed a structural assessment of the primary assets at the East WRF in December 2021 and
concluded that no major component at this facility has permanent value worth restoring. While
some existing infrastructure and minor components may be rehabilitated and reused, they may
only serve temporary purposes and have no permanent value. One exception to this is the
existing chlorine contact chamber. Structurally, the chlorine contact chamber is in acceptable
condition and could be rehabilitated to lower construction costs, including new repumping
equipment costs. Some components still require replacement, such as the effluent gates.
However, the existing chlorine contact chamber may not fit into the hydraulic profile of the new
East WRF. This must be further analyzed during subsequent design stages.
The existing electrical equipment is also outdated and does not meet current National
Electric Code (NEC). As such, for conceptual design purposes, no unit process equipment
(e.g., mechanical, structural, or electrical assets) will be preserved for the new East WRF.
There are, however, some non-unit process items which have the possibility of being maintained
for storage purposes, including the reuse GST, onsite storage/reject pond, and one of the
three circular steel structures. The GST and storage/reject pond are in good condition overall and
can continue to store treated effluent for the new WRF. One of the three steel structures may
also be repaired or rehabilitated and temporarily used to store solid residuals from the new
treatment scheme, allowing the City time to plan and design for a permanent solids handling
facility. Like the chlorine contact chamber, the feasibility of reusing these existing assets must
be further assessed during later design stages.
1.3.3 Site Boundary and Contour Survey
L&S Diversified (L&S) completed a conceptual-level boundary and topographic survey to
facilitate the planning stages of the project. The established boundary of the East WRF totals
approximately 50.6 acres, although this includes a number of trees and wetlands which have
been preliminarily identified. Figure 2 shows the limits of the site boundary and contour survey.
In addition to displaying boundary lines, easement information, and contour lines, the attached
survey (included in Appendix B), also displays existing buried mains, as well as the elevations of
key hydraulic infrastructure.
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Figure 2 East WRF Site and Contour Survey
1.3.4 Environmental Review
An environmental review was completed of the site based on the planned concept facilities.
Environmental Science Associates (ESA) completed an environmental constraints review within
the review area shown in Figure 3. Appendix C includes the ESA environmental constraints
review and the Florida Natural Area Inventory (FNAI) tracking list. In general, and as further
described below, there are minor site constraints which will need to be addressed in design,
primarily including wetland impacts in some areas of construction.
The following items are addressed to meet state, federal and potential funding requirements:
• List threatened, endangered, proposed, and candidate species and designated
critical habitats that may be present in the project area (may be obtained from
U.S. Fish and Wildlife Service). A list of potential threatened, endangered, proposed,
and candidate species and designated critical habitats that may be present within the
general area of the proposed Project is attached as Appendix C, Florida Natural Areas
Inventory. Habitat does not exist within the Project review area for a majority of these
species, with the exception of the Bald eagle (Haliaeetus leucocephalus) and gopher
tortoise (Gopherus polyphemus), as identified in the General Environmental Constraints
Review (Appendix C). The Audubon Florida EagleWatch Nest Locator database was
reviewed, and no nest trees were identified within 600-feet (protective nest buffer zone)
of the Project review area, therefore impacts to the bald eagle are not anticipated.
Additionally, during the environmental review, no gopher tortoise burrows were
observed within or directly adjacent to the Project area. However, a 100-percent gopher
tortoise burrow survey will need to be performed within the upland limits of proposed
Project footprint, at least 90 days from construction initiation in accordance with the
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Florida Fish and Wildlife Conservation Commission gopher tortoise survey and
permitting guidelines (reference in Rule 68A-27.003, Florida Administrative Code).
No other listed species, or critical habitat was observed or identified within the property
limits.
• Discuss any significant adverse effects upon flora, fauna, threatened or endangered
plant or animal species, surface waterbodies, prime agricultural lands, wetlands, or
undisturbed natural areas. No listed flora or faunal species were identified within the
attached Environmental Constraints Review (Appendix C). The proposed Protect is
anticipated to impact approximately up to 2 acres of forested wetlands that were
identified as medium quality and jurisdictional to the state and federal agencies. Other
areas that may be impacted from the Project activities include highly disturbed,
maintained upland areas that are inclusive of the treatment facility. No other
undisturbed natural areas exist within the footprint of the proposed Project. The facility
is located within the City of Winter Springs Planned Unit Development (PUD) Zone;
therefore, no prime or unique agricultural lands exist within the proposed Project
footprint.
• List any significant adverse environmental effects and what project features will
mitigate such effects. It is anticipated that the Project activities will impact
approximately up to 2 acres of medium quality forested wetlands. During the final
design phase of the Project, all impacts will be minimized, where feasible, to further
reduce the footprint and the Project impacts. All construction activities will obtain and
comply with National Pollutant Discharge Elimination Systems (NPDES) permits and
employ Best Management Practices to assure no impacts to water resources during
construction. The site development associated with the Project will follow state water
quality and quantity regulations to avoid alteration in drainage patterns or soil erosion or
runoff. The Project will obtain construction and operation phase permits from the
required state and federal agencies and will operate in accordance with all relevant
regulations. In addition, appropriate state and federal permits will be obtained and
mitigation will occur to off-set those impacts. Mitigation options for this area include:
- Utilization of an approved mitigation site within the Lake Jesup Basin,
- Construction of a wetland mitigation site within the Lake Jesup Basin, either
utilizing land owned or purchased by the City of Winter Springs, or
- Investigations with FDEP to utilize an out-of-basin, regionally significant mitigation
bank (within the same watershed – St. Johns River Watershed) with a Cumulative
Impact Analysis.
• Discuss any significant adverse human health or environmental effects on minority
or low-income communities. The East WRF is located in the eastern area of Winter
Springs, primarily surrounding by residential community. Recent data from the
EJSCREEN Census Summary Report (Accessed April 2022) indicates an overall City
population demographic index of 26 percent with low income being 19 percent. For the
immediate area around the East WRF, the demographic index is 16 percent, with low
income being 3 percent. All values are under the state and national averages.
Furthermore, this project considers the replacement of an existing WRF with a new
facility. An improved and modernized WRF will benefit the entire community with
improved reliability in wastewater treatment and effluent water quality which meets or
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exceeds regulatory requirements. Therefore, disproportionate high or adverse
environmental effects to a minority population is not anticipated.
Figure 3 East WRF Environmental Survey Area
1.3.5 Odor Survey
Webster Environmental Associates, Inc. (Webster) completed an odor survey at the East WRF in
November 2021. This study was done to assess the Hydrogen sulfide (H2S) gas odor impact on
the local area, for consideration with the design and construction of a new treatment facility.
Hydrogen sulfide occurs naturally in sewers, manure pits, well water, oil and gas wells, and
volcanoes. The health effects of hydrogen sulfide depend on how much H2S a worker breathes
and for how long. The odor threshold for hydrogen sulfide gas falls in the 0.01 to 1.5 ppm range
and some will begin to notice the “rotten egg smell” at these concentrations. The odor becomes
more offensive at 3 to 5 ppm. Prolonged exposure in confined areas at these concentrations may
cause nausea, tearing of the eyes, headaches, or loss of sleep. However, because wastewater
facilities are mainly open to the atmosphere, operators and visitors are generally not at risk for
negative health effects from H2S during routine operation.
Six OdaLog™ units were installed around the facility and recorded Hydrogen sulfide (H2S) gas
concentrations for nine days. These OdaLog™ units measure H2S in the range of +/-300 ppb and
were installed at the following locations: flow splitter box/headworks, surge tanks, SHT,
digester, and belt filter press. The sixth OdaLog™ unit was installed on a tree outside of the WRF
property, near the public park entrance, to understand how odors may disperse from the
treatment site and migrate to the park area. The locations of each logger are shown graphically
in Figure 4.
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Figure 4 OdaLog Installation Locations at East WRF
The OdaLog™ data from the nine-day monitoring period is included in Table 2. All locations
were found to have low to moderate concentrations of H2S (with an average of 0 to 3 ppm),
apart from the surge tank which had very high, brief spikes each day. These spikes then quickly
dispersed, only lasting approximately 5 minutes. They would occur daily between 11am and 2pm
and range from 100 to 1,200 ppm. While it is not confirmed, one potential cause of these brief
spikes could be attributed to the master lift stations experiencing peak flows. A number of
wastewater lift stations discharge directly into the surge tank at the East WRF and because they
likely turn on at the same time during peak flows, high loads will be discharged into the surge
tank at these times. Webster noted that these concentrations are likely to also cause offsite odor
detections.
The park entrance instrument surprisingly recorded two brief spikes of 0.1 ppm, also lasting
approximately 5 minutes, which may be the result of the high H2S coming from the surge tank. A
full copy of the Odor Study report can be found in Appendix D.
Table 2 East WRF Hydrogen Sulfide Monitoring Summary
Instrument Location Instrument
Range (ppm) Logging Duration H2S Average
(ppm)
H2S Peak
(ppm)
Influent Splitter Box 0-1,000 11/10/21 to 11/19/21 0.12 2
Surge Tank 0-1,000 11/10/21 to 11/19/21 3 1201
Thickener Tank 0-1,000 11/10/21 to 11/19/21 0 0
Aerobic Digester Tank 0-1,000 11/10/21 to 11/19/21 0 1
Belt Press 0-200 11/10/21 to 11/19/21 0 7
Park Entrance 0-50 11/10/21 to 11/19/21 0 0.1
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1.3.6 Geotechnical Investigation
At the time of this report, no geotechnical investigation has been conducted at the East WRF.
This information will be needed prior to the design stages but is not necessary within conceptual
design. A complete geotechnical survey and determination of structure locations should
therefore be performed as part of the final design.
1.3.7 Wastewater Characterization and Population Flow Projections
Based on the identified service area, population growth, and historical facility flows, a projected
flow was developed for the East WRF to use when sizing the new facility. The following
subsections summarize the existing historical water quality and quantity data, as well as
population projections, to develop design criteria for the future facility, including flows, loads,
and peaking factors.
1.3.8 Wastewater Flow and Loading Characterization
Historical flow data was gathered and analyzed as part of the recently completed East WRF
permit renewal. Table 3 provides historical monthly flows observed at the facility over the past
10 years, as well as minimum, maximum and annual average flows. All data was obtained from
Discharge Monitoring Reports (DMR) submitted by the City to FDEP.
Table 3 East WRF Historical Monthly and Annual Average Daily Flows(1)
Month/Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021
January 0.99 0.80 1.03 1.10 1.03 0.99 1.02 1.00 1.04 0.97 1.03
February 0.95 0.85 1.00 0.98 0.98 1.03 0.95 0.96 1.10 1.00 1.00
March 0.95 1.03 1.07 1.01 1.05 1.01 0.91 0.96 1.05 1.04 0.97
April 0.91 1.02 1.04 1.00 1.02 1.11 0.98 0.96 1.10 1.05 1.04
May 0.84 0.99 1.08 1.00 1.01 1.05 0.96 0.96 0.99 1.02 0.95
June 0.83 1.05 1.05 0.98 0.92 1.07 0.95 1.06 1.04 0.96 0.94
July 0.90 1.12 1.21 1.01 0.98 0.96 1.10 1.07 1.07 0.90 0.97
August 0.91 1.08 1.17 1.03 1.04 0.96 1.07 1.07 1.05 0.98 1.11
September 0.84 1.17 1.06 1.07 1.13 1.05 1.35 1.04 0.97 1.09 1.13
October 0.96 1.21 1.03 1.12 1.02 1.13 1.16 0.88 1.00 1.03 1.01
November 0.88 1.06 1.10 1.03 1.08 0.99 0.94 1.03 1.00 1.06 -
December 0.88 1.13 0.98 1.06 1.02 0.99 1.16 1.07 1.00 1.01 -
Minimum 0.83 0.80 0.98 0.98 0.92 0.96 0.91 0.88 0.97 0.90 0.94
Maximum 0.99 1.21 1.21 1.12 1.13 1.13 1.35 1.07 1.10 1.09 1.13
AADF(2) 0.90 1.04 1.07 1.03 1.02 1.03 1.05 1.01 1.03 1.01 1.01
Notes:
(1) All units of flow are in mgd.
(2) AADF for 2021 is the average from January to October.
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Figure 5 is a plot of AADF, long-term average flow, and the permitted capacity at the East WRF.
This figure shows that the yearly AADF never exceeded the permitted capacity of 2.012 mgd
between 2011 and 2021. Additionally, the long-term average flow was 1.02 mgd AADF and the
maximum monthly flow observed was 1.35 mgd over this 10-year period, indicating that East
WRF has operated at roughly half of its permitted capacity.
Figure 5 East WRF Annual Average Daily Flows
In addition to flows, historical loading information over the past year was compiled for the East
WRF. Table 4 and Figure 6 present average monthly influent cBOD5 and TSS concentrations and
loadings observed at East WRF between October 2020 and October 2021. No influent TN and TP
data was available as these parameters are not required to be monitored in the facility’s influent
under its current permit. Consequently, industry standard ratios of 1:5 and 1:11 were used for
TKN:cBOD5 and TP:cBOD5, respectively. It should be emphasized that these factors should be
refined during later design stages following a detailed influent sampling campaign.
Influent TSS and cBOD5 both exhibited similar trends, with maximum loads observed in
February 2021 and average annual loads of 1,970 and 1,980 lb/d, respectively. Minimum loads
were observed in October 2020 and May 2021. Additionally, a statistical analysis was performed
to remove data outliers prior to calculating the relevant design peaking factors – results of this
analysis are presented in Section 3.2.1 Influent Wastewater Flows and Loads.
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Table 4 East WRF Influent cBOD5 and TSS Concentrations and Loads
Month/Year
Influent cBOD5
Concentration
mg/L
Influent cBOD5
Loading
lb/day
Influent TSS
Concentration
mg/L
Influent TSS
Loading
lb/day
Oct-20 122 1,043 130 1,111
Nov-20 126 1,110 180 1,585
Dec-20 182 1,538 296 2,501
Jan-21 212 1,821 292 2,508
Feb-21 341 2,838 452 3,762
Mar-21 341 2,753 254 2,051
Apr-21 275 2,374 220 1,899
May-21 213 1,682 125 987
Jun-21 322 2,522 260 2,036
Jul-21 276 2,224 266 2,143
Aug-21 228 2,118 266 2,471
Sep-21 188 1,693 61 549
Oct-21 201 1,695 135 1,138
Average 230 1,960 230 1,900
Minimum 122 1,043 61 573
Maximum 341 2,838 452 3,762
Figure 6 East WRF Historic Monthly cBOD5 and TSS Loading
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1.3.9 Population Projections
Population data and projections for Winter Springs were obtained from a combination of reports
prepared by the U.S. Census Bureau and the Bureau of Economic and Business Research (BEBR).
Because the U.S. Census reports current populations on a city-basis, while the BEBR report lists
population projections on a county-basis, a number of assumptions were applied for this analysis
to draw meaningful conclusions from the data available. However, these assumptions were
verified with the analyzed data made by Kimley-Horn in the “City of Winter Springs 2022
Wastewater and Reclaimed Water Master Plan” for consistency and accuracy. Additionally,
internal meetings were held with the City Planner to gain an understanding of future potential
growth or other wastewater contributors that may impact the East WRF’s future wastewater
flows.
One assumption made is that the City of Winter Springs will experience the same growth
projected for Seminole county through 2045, and that wastewater flows would increase
proportional to this population growth. Another assumption was that all of the citizens reported
by the U.S. Census were connected to the City’s sewer system, and that the City’s wastewater
service area exhibits an even split between East and West WRFs. This even-split assumption is
consistent with the analyzed data within the “City of Winter Springs 2022 Wastewater and
Reclaimed Water Master Plan” prepared by Kimley-Horn.
Based on these assumptions, the growth factors listed in Table 5 were developed and used to
project wastewater flows through 2045. Discussions with the City Planner revealed that
generally limited growth is expected in the near future since no large, new developments within
the City’s wastewater service area are currently planned. Additionally, a majority of City property
has been developed and the City does not plan to acquire any considerable portion of additional
land.
Table 5 Winter Springs Population and Flow Growth Factors
Projection Type(1)(2) 2025 2030 2035 2040 2045
Low Series -1.2% 0.8% 2.3% 3.1% 3.2%
Medium Series 6.0% 10.9% 15.0% 18.5% 21.5%
High Series 12.8% 21.3% 28.9% 35.9% 42.3%
Notes:
(1) All factors shown in the table above correspond to population growth relative to the current Winter Springs population.
(2) Sources: U.S. Census Bureau (2020), Winter Springs population estimates base and BEBR (2020), Projections of Florida
Population by County, 2025-2045.
In addition to the factors provided above, an average 2020 wastewater generation rate of
65 gallons per capita per day (gpcd) was calculated for Winter Springs, based on the ‘even split’
assumption between the East and West WRF. The 65 gpcd is also consistent with the per capita
rates used within the “City of Winter Springs 2022 Wastewater and Reclaimed Water Master
Plan” prepared by Kimley-Horn. The calculated per capita wastewater generation rate is slightly
less than the typical industry standard range of 70 to 80 gpcd for residential communities but
aligns with the City’s development projections.
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1.3.10 Proposed East WRF Design Capacity
Figure 7 displays the resulting flow projections for East WRF after synthesizing population data
for Winter Springs from the 2020 BEBR and U.S. Census reports (i.e., Table 5). Results from this
analysis indicate that 2045 flows may range anywhere from 1.04 to 1.43 mgd AADF, which are
less than the current permitted capacity of 2.012 mgd. Additionally, the “City of Winter Springs
2022 Wastewater and Reclaimed Water Master Plan” prepared by Kimley-Horn projects that if
growth were to occur with available parcels, along with potential septic to sewer conversions,
flow may reach 1.49 mgd over the next 20 years. This CDR considers replacement of the facility
at its current capacity, evaluating a WRF at 2.1 mgd AADF. However, right-sizing the facility to
account for near-term growth will be evaluated in Section 4, the Final Recommendation section.
Figure 7 East WRF Flow Projections
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2.0 Liquid Stream Alternatives Evaluation
2.1 Evaluation Overview
The conversion of the East WRF to an AWT-capable facility requires modernization all of its
existing liquid treatment processes. To determine which treatment alternative best suits the
City, an analysis of all available liquid treatment technologies was completed by the project
team, as well as a thorough and well-vetted selection process based on City values. As part of
this evaluation, Carollo performed the following:
• Prepared a working list of liquid-stream technologies proven to meet AWT standards,
• Performed a conceptual-level review of the selected liquid-stream process alternatives,
• Developed evaluation criteria to rank each of the process alternatives in terms of their
ability to meet the City’s values,
• Hosted a paired comparison exercise with a City-appointed selection committee for City
to apply a value (or weight) to each evaluation criterion, and
• Shortlisted two alternatives from the working list for further development and in-depth
analysis (i.e., conceptual site layout and capital/operational cost estimate).
It is important to note that the removal of key constituents from domestic wastewater
(i.e., BOD, TSS, TN, and TP) is achieved primarily during a wastewater treatment facility’s
secondary treatment process. While an overall, conceptual-level recommendation is provided
within this CDR for the entire East WRF, the paired comparison exercise focused only on the
alternatives for secondary treatment processes and did not compare alternatives for preliminary
treatment, secondary clarification, biosolids handling, odor control, and pumping requirements.
These processes have been analyzed by Carollo and subconsultants, with recommendations
provided in Sections 3 and 4.
2.2 Selection of Liquid Stream Treatment Alternatives
Municipal wastewater treatment plants in Florida rely on a relatively low number of treatment
processes to remove nutrients (e.g., nitrogen and phosphorus). Most of these processes are
variations of the conventional activated sludge (CAS) process, often incorporating different
sequencing and configurations of process tanks with anaerobic, anoxic, and aerobic zones.
However, from a global perspective, a larger number of process configurations for nutrient
removal have been developed and many of these configurations are currently in-service at
municipal wastewater treatment facilities abroad.
When compared to physical or chemical processes, biological processes have generally been
proven to be more economically efficient in removing nitrogen and phosphorus from municipal
wastewater. Additionally, land-based technologies, such as natural or constructed wetlands and
algae scrubbers, are not typically used to remove nutrients from municipal wastewater due to
their very large land requirements and limited operating capacity. Consequently, only biological
treatment-based technologies have been considered in these evaluations.
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Biological treatment uses either suspended- or attached-growth processes to maintain biological
activity. These are defined as:
• Suspended-growth: Processes that use biomass suspended in wastewater (activated
sludge) to perform the required biochemical transformations. Examples are sequencing
batch reactors using in-basin clarification and continuous-flow reactors using separate
clarifiers or membranes for solids separation.
• Attached-growth: Processes that use biomass that attaches to, and forms a film on,
media (i.e., biofilm). Examples are trickling filters, rotating biological contactors, and
packed bed reactors.
Biological processes typically operate in a continuous-flow mode of operation but can also be
operated in a batch-process mode. A recycle stream is typically used to maintain the
microorganism population within the treatment process. The solids retention time (SRT) and
hydraulic retention time (HRT) of the biological processes are critical to achieving the required
secondary treatment.
It should be highlighted that not all biological treatment processes can remove nutrients from
domestic wastewater. To do so, a biological treatment process must foster the growth of certain
microorganism communities. These microorganisms help remove nitrogen through the two-step
process of nitrification and subsequent denitrification:
1. Nitrification: Oxidation of ammonia (NH3) to nitrite (NO2) and then to nitrate (NO3).
2. Denitrification: Reduction of nitrate to nitrite and then to nitrogen gas (N2).
Biological phosphorus removal, on the other hand, is accomplished through an enhanced
biological process that encourages certain microorganisms to uptake phosphorus in greater
(stoichiometric) quantities than required for their normal growth. When these microorganisms
are wasted from the system, phosphorus removal is achieved, and the overall process is termed
enhanced biological phosphorus removal (EBPR).
2.2.1 Preliminary List of Potential Process Alternatives
To begin, Carollo created an extensive list of biological wastewater treatment technologies
capable of achieving some degree of nutrient removal. This list is referred to as “The Universe of
Alternatives”, and includes a broad spectrum of proven technologies that can be grouped
according to the following physical characteristics:
• The use of microorganism communities (i.e., suspended growth or attached growth),
• The physical configurations of the treatment processes (i.e., land-based, aquatic, or
mechanical facilities),
• The location of the solids-separation/clarification unit process, which further categorizes
suspended-growth processes into single-sludge and multiple-sludge systems,
• The physical configuration of single-sludge systems distinguished as processes with
multiple stages or phases, and Concentrations of nutrients in sidestreams with separate
sidestream treatment processes required for facilities with significantly elevated
concentrations of nitrogen and phosphorus in their sidestreams.
Figure 8 shows a graphical representation of these groupings.
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Figure 8 Overview of Biological Treatment Technologies for Nitrogen and Phosphorus Removal from Municipal Wastewater
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2.2.2 Biological Nutrient Removal to Achieve AWT
To achieve an AWT-quality effluent, a biological nutrient removal (BNR) process must be
configured with different sequencing and configurations of process tanks with anaerobic (no free
oxygen or nitrate), anoxic (no free oxygen), and aerobic (oxygen rich) zones. These zones create
various degrees of oxidation and reduction potential which favor the growth of specific bacteria
with different capabilities of metabolizing cBOD5, nitrogen, and phosphorus. The primary
purpose of each zone is briefly summarized below:
• Anaerobic Zone: Wastewater enters this zone and is depleted of oxygen or oxidized
nitrogen (i.e., nitrate), which allows both the uptake of readily biodegradable organic
material and the release of soluble orthophosphate from by certain microorganisms into
the wastewater. This zone significantly reduces cBOD5 and, in terms of nutrient
removal, mainly serves the purpose of increasing enhanced biological phosphorus
removal (EBPR) efficiency in O2.
• Pre-Anoxic Zone: This zone consists of internal mixing to maintain anoxic conditions
and not introduce dissolved oxygen. Mixed liquor from the anaerobic reactor and recycle
flows from the aerobic zone enter this zone while heterotrophic bacteria use the cBOD5
in the wastewater to reduce nitrates recycled back from the aerobic zone to nitrogen
gas. The lack of dissolved oxygen in this zone encourages the biomass to use
chemically-bound oxygen in nitrate for growth, thus removing nitrogen from the system
(i.e., denitrification).
• Aerobic Zone: Following the pre-anoxic zone, the mixed liquor enters the third zone,
which uses supplemental aeration to provide dissolved oxygen to organisms that oxidize
nitrogen in the wastewater from ammonia to nitrites and nitrates (i.e., nitrification). An
internal recycle pump sends a portion of the flow, rich in nitrates and nitrites, to the
pre-anoxic zone for denitrification. This zone also oxidizes any remaining cBOD5 and
removes phosphorus by absorbing orthophosphate in the biomass in excess which is
later wasted as sludge.
• Post-Anoxic Zone: This zone further reduces nitrogen in the effluent. Any unreduced
nitrate that was not recycled to the pre-anoxic zone is reduced to nitrogen gas here.
Compared to the first anoxic zone, the denitrification reaction rate within this second
anoxic zone is generally endogenous and slower because of a lower ‘driving force’ due to
the reduced cBOD5 concentration compared to pre-anoxic zones (most cBOD5 is
removed in the aeration zone). However, the size of the second anoxic zone can be
reduced by adding an external carbon source such as glycerol or other forms of
supplemental carbon.
• Reaeration Zone: This final zone is a small aeration step that strips nitrogen gas and
inhibits phosphorus release. To remove phosphorus, sludge must be wasted from the
process, typically from the clarifier underflow (i.e., from the RAS) or in the membrane
tank when membranes are used for solids separation.
As discussed above, the process basins for a BNR configuration have anaerobic zones to
facilitate phosphorus removal, anoxic zones to achieve denitrification, and aerobic zones to
achieve nitrification, phosphorus, and cBOD5 removal. The effluent from the process basins
consists of treated wastewater and suspended solids, which are composed of microorganisms,
biodegradable, and non-biodegradable (inert) matter. These microorganisms consume organics
in the wastewater during their growth process and need to be periodically wasted from the
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system to maintain a stable biological community in the BNR process. To accomplish this
wasting, effluent is transferred to a subsequent solids separation system (e.g., secondary
clarifiers or membrane bioreactors) to separate the suspended material from the treated
wastewater. Most of the separated suspended solids are then recycled back to the BNR process
to maintain the desired concentration of microorganisms in the treatment process, while the
remaining suspended solids are wasted from the system via a sludge stream for subsequent
treatment.
There are many process variations to achieve an AWT-quality effluent, each with slight changes
to the arrangement of the process basin zones and the type of solids-liquid separation
employed. However, not all variations can meet the strict effluent limits required for AWT. The
following subsections detail a number of technologies that have proven success with
consistently achieving AWT.
2.2.3 Potential AWT Treatment Alternatives
To prepare a working list of technologies for further evaluations, Carollo refined the initial list of
all available nutrient removal processes shown in Figure 8. As noted in this figure, not all
processes shown are capable of achieving both nitrogen and phosphorus removal. Hence, this
extensive list was shortened to Figure 9 to produce a refined list of technologies that can
consistently meet AWT standards using BNR.
The 5-stage BNR process configuration is the most commonly used technology for achieving
AWT, and was thus selected as the first, baseline alternative for further review. The remaining
alternatives were then selected on the following basis:
• National experience and use of the process.
• Record of performance for full scale installations.
• Representation of viable forms of emerging treatment processes or technologies.
In addition to the 5-stage activated sludge BNR process, Carollo selected viable candidate
processes from Figure 9 that represented processes from the following categories:
• Single Sludge: Multiple Stages.
• Single Sludge: Multiple Phases.
• Ballasted Activated Sludge: Aerobic Granular Sludge.
• Ballasted Activated Sludge: Ballasted Activated Sludge.
• Attached Growth: Moving Bed.
According to this selection process, Carollo chose the following technologies for further analysis:
• Five-stage activated sludge BNR (5-stage BNR).
• Membrane bioreactor (MBR).
• Ballasted activated sludge (BAS).
• Aerobic granular sludge (AGS).
• Sequencing batch reactor (SBR).
• Integrated fixed-film activated sludge (IFAS).
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Figure 9 Biological Treatment Technologies for Achieving AWT in Municipal Wastewater
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2.3 Descriptions of Proposed AWT-Capable Treatment Alternatives
This section presents technology fact sheets for each of the six process configurations on
Carollo’s working list. Each fact sheet includes the following information:
• A brief description of the process.
• A simplified process flow schematic that shows the general arrangement of various
secondary- and tertiary-treatment unit processes including recycle streams.
• A table of basic facts about the technology, i.e., perceived process reliability, major
advantages and disadvantages, operational considerations, relative energy usage,
footprint, sludge production, chemicals used, and impact on neighbors.
Because it is the most common process for achieving AWT effluent quality and because of the
large number of installations of the 5-stage BNR process, it will be used as a baseline process
that the other process configurations will be compared against.
2.3.1 Five-Stage Activated Sludge BNR (5-Stage BNR)
The 5-stage BNR process is a conventional activated sludge BNR process which is configured
with the five zones as described in Section 2.2.2 and has proven to achieve the strict AWT
effluent requirements. Figure 10 shows the 5-stage BNR process flow configuration while Table 6
outlines additional considerations and information concerning this technology.
Figure 10 5-Stage BNR Process Flow Diagram
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Table 6 5-Stage BNR Fact Sheet
Parameters Description
Proprietary Process/Equipment None known. No sole-sourced or proprietary equipment
required.
National Experience/Success Successfully used at many plants in Florida and elsewhere.
Process Reliability Reliable and well-proven in the U.S.
Major Advantages
• Consistently meets AWT effluent quality.
• Operational familiarity that does not require additional
training.
• Large local and national peer communities available for
operations to reach out to for troubleshooting.
Major Drawbacks Requires a larger footprint than the other alternatives.
Pre-Treatment Requirements Single-stage screening and grit-removal.
Operational Considerations Similar to current operations.
Chemical Requirements
• Possible use of alum or ferric chloride for phosphorus
removal during process upsets.
• Possible use of supplemental carbon depending on
carbon to nitrogen ratio in the influent wastewater.
Footprint Larger footprint than those of other alternative
configurations.
Residuals Management
Increased WAS production due to nitrogen and phosphorus
removal. This increase is comparable to other treatment
configurations.
Energy Use Moderate energy use compared to other technologies.
Ease of Expansion/Upgrade Expansion requires additional parallel trains.
Impact on Neighbors Noise and odor comparable to those of other configurations.
2.3.2 Membrane Bioreactor
Membrane Bioreactor (MBR) is a variation of BNR in which MBR tanks and equipment replace
secondary clarifiers and tertiary filters. Compared to what is achieved in conventional
clarification processes, an MBR provides a high degree of solids separation and can operate with
much higher MLSS concentrations while also producing effluent with low suspended solids (TSS
<1 mg/L). Unlike activated sludge processes which rely on secondary clarifiers for suspended
solids separation, MBR process basins can operate at significantly higher MLSS concentrations
(6,500 to 7,500 mg/L compared to 2,000 to 4,000 mg/L for CAS systems) and are therefore much
smaller.
Plants operating MBR processes require two-stage screening typically using coarse screens
followed by 2 mm perforated secondary screens to protect the membranes. The membrane
causes a significant head-loss on the forward flows, which requires an additional set of permeate
pumps to convey flows from the membrane tank to the downstream disinfection process.
Figure 11 shows the MBR process flow configuration.
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Figure 11 Membrane Bioreactor (MBR) Flow Diagram
Table 7 outlines additional considerations and information concerning MBR.
Table 7 Membrane Bioreactor (MBR) Fact Sheet
Parameters Description
Proprietary
Process/Equipment
• Each membrane system is unique and proprietary. Over recent years, competition has
increased with multiple manufacturers entering the field, which has driven innovation,
changed perceptions, and closed gaps in costs with conventional technologies.
• Hollow-fiber and flat-plate configurations available.
• Early selection and procurement are recommended.
National
Experience/Success
• Well-established and largely successful technology with approximately 500
installations nationally and thousands of installations worldwide.
Process Reliability • Very reliable.
Major Advantages
• Consistently produces effluent of very high quality meeting AWT requirements.
• Smallest footprint of all the alternatives.
• Volume of the process basins is relatively small since they can be operated at higher
MLSS concentrations.
• Eliminates secondary clarifiers and filtration processes.
• Highly automated process.
• Helps pre-position future potable reuse options.
• Membrane systems have a positive public perception since they are state-of-the-art
technologies.
• Improves disinfection efficiency, because of the very low TSS and turbidity in the
effluent.
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Parameters Description
Major Drawbacks
• More mechanical equipment and maintenance than required for five-stage BNR.
• Higher energy use than what’s required the five-stage BNR process since the aeration
basins operate with higher MLSS concentrations and have a higher aeration demand.
• Chemical and scouring equipment required to maintain membranes increases energy
costs.
• Higher chemical usage to keep membranes clean.
• Higher pumping than required for five-stage BNR process.
• Flow equalization required to attenuate flow and minimize membrane cost.
• Physical-hydraulic barrier at the membranes can cause hydraulic bottlenecks during
wet weather flows, making flow equalization or membrane redundancy critical.
• Shifts in operational strategies (e.g., towards automation, analyzers, sensors) can
challenge operations staff.
• Fine screenings may result in cBOD5 loss in primary treatment while also requiring
additional screenings-material handling.
Pre-Treatment
Requirements
Two-staged screenings with perforated fine screens (≤2 mm) to remove fine solids such as
hair and fibers.
Operational
Considerations
• More mechanical equipment to maintain.
• Automated membrane process.
• Periodic membrane cleaning required.
• Reliable access to the membranes is key.
Chemical
Requirements
• Higher chemical use than five-stage BNR process since sodium hypochlorite and citric
acid are needed to chemically clean membranes.
• As-needed use of alum or ferric chloride to trim phosphorus.
Footprint Smallest footprint of the configurations or any other proven full-scale biological treatment
technology.
Residuals
Management
• WAS produced comparable to that of five-stage BNR process.
• Total quantity of solids produced is moderately higher than that of BNR since
additional screenings material is produced from fine screenings.
Energy Use Higher energy consumption than the five-stage BNR process.
Ease of
Expansion/Upgrade
• Expansion requires constructing additional process trains and membrane units.
• Depending on the initial design of process trains, upgrade, and expansion of the MBRs
can be modular and may only consist of adding additional membrane units or
cassettes.
Impact on
Neighbors
• Noise and odor comparable to those of the five-stage BNR process.
• Smaller footprint can allow MBRs to be enclosed.
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2.3.3 Sequencing Batch Reactor (SBR)
SBR is another variation of BNR that accomplishes the 5-stage BNR process through a series of
time steps in a single reactor. Typically, a single cycle for each SBR reactor consists of five steps:
• Step 1, Fill: Influent raw wastewater is added to the reactor, and anoxic and anaerobic
conditions are created.
• Step 2, React: Influent flow is continuous with aeration applied continuously or
intermittently.
• Step 3, Settle: Aeration is stopped, and solids/liquids separation occurs.
• Step 4, Draw/Decant: Clarified effluent is withdrawn from the top of the reactor via a
decanting mechanism.
• Step 5, Idle: Sludge is wasted.
Figure 12 shows SBR’s process flow configuration. Activated sludge aeration and liquid solids
separation occur in the same tank, thus RAS or secondary clarifiers and their associated pumps
are not required. Under SBR, flexibility is allowed in the duration of aerobic and anaerobic phases
to encourage optimum nitrogen and phosphorus removal rates.
Figure 12 Sequencing Batch Reactor (SBR) Process Flow Diagram
Table 8 outlines additional considerations and information concerning SBR.
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Table 8 Sequencing Batch Reactor (SBR) Fact Sheet
Parameters Description
Proprietary
Process/Equipment
Several SBR equipment manufacturers exist. Process tanks are customizable,
although some configurations are proprietary.
National
Experience/Success More than 1,300 facilities in the U.S., Canada, and Europe employ SBRs.
Process Reliability Handful of plants in Florida use SBRs and successfully produce effluent
meeting AWT quality.
Major Advantages
• Biological treatment and secondary clarification can be achieved in a
single reactor vessel.
• SBR processes can handle large seasonal variations in flow and loads.
• Process modification is flexible.
• No internal MLSS or RAS recycle required so less pumping energy
required than what BNR uses.
Major Drawbacks
• SBR processes are more commonly used at facilities with flowrates of
5 mgd or less in the U.S.
• Requires larger-sized blowers than what’s used for the five-stage BNR
process.
• Requires flow equalization downstream of the process tanks and
upstream of filters. Without equalization before tertiary filtration, the
filters must be “oversized” to accommodate extremely high peak flows.
• Sludge settleability can create adverse process conditions.
• Greater operator involvement than what’s required for the five-stage
BNR process.
• Some SBR equipment and control systems are proprietary making
repair, replacement, and troubleshooting of control systems difficult
without involving the equipment manufacturer.
• Equipment failure (e.g., decanter, mixer, aeration systems, etc.) requires
taking the entire SBR process-train offline, affecting redundancy and
available capacity.
Pre-Treatment
Requirements Traditional screening and grit-removal.
Operational
Considerations
Requires a sophisticated system of units and controls, as well as a higher level
of maintenance for controls, switches, and valves, compared to what’s
required for BNR.
Chemical
Requirements
Similar to BNR with as-needed use of alum or ferric chloride for phosphorus
removal.
Footprint Slightly smaller compared to the five-stage BNR process. Secondary clarifiers
can be removed but footprint is still required for multiple SBR basins.
Residuals
Management WAS produced similar to that of five-stage BNR process.
Energy Use Low to moderate energy use compared to five-stage BNR process.
Ease of
Expansion/Upgrade Fairly modular construction is possible.
Impact on Neighbors Noise and odor comparable to those of five-stage BNR process.
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2.3.4 Aerobic Granular Sludge – AquaNereda®
Aerobic Granular Sludge (AGS) is a novel method to remove carbon, nitrogen, and phosphorus in
a single bioreactor. Aerobic granular sludge itself consists of dense granules of mixed microbial
communities that do not coagulate and, therefore, settle much faster than activated sludge
flocs.
The AGS treatment process is similar to that of SBR but operates in three steps: 1) fill and draw,
2) react, and 3) settle. Similar to SBR, separate secondary clarifiers or recycling of RAS is not
required.
Compared to the 5-stage BNR process activated sludge, AGS granules settle very rapidly so
process basins can be much smaller. The granules’ high settling velocities allow bioreactor
operation at very high MLSS concentrations (8,000 to 12,000 mg/L), thereby reducing the overall
footprint of the process tanks.
The outer layers of the granule are aerobic and support nitrifier growth, while anoxic and
anaerobic zones occur in the center or the granule. As such, AGS can perform carbon removal,
nitrification, denitrification, and phosphorus removal all in one bioreactor. There is currently only
one operating AGS facility in the United States, but there are several operating throughout the
world.
Figure 13 shows the AGS process flow configuration.
Figure 13 Aerobic Granular Sludge (AGS) Process Flow Diagram
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Table 9 outlines additional considerations and information concerning AGS.
Table 9 Aerobic Granular Sludge (AGS) Fact Sheet
Parameters Description
Proprietary Process/Equipment Limited providers of AGS systems for municipal wastewater
treatment in North America.
National Experience/Success In the U.S, one full-scale AGS facility is in in operation. As of
January 2020, there were over 75 installations worldwide.
Process Reliability
Largely unknown. At the time this report was written, there
were no full-scale operating plants in the U.S. that were
treating to AWT standards.
Major Advantages
• AGS granules settle faster than five-stage BNR process
sludge, thus requires less reactor volume.
• Process train can be operated at a higher MLSS
concentration than what can be done with five-stage
BNR process without affecting performance.
• Requires no internal MLSS or RAS recycle so demands
less pumping energy than what five-stage BNR process
uses.
Major Drawbacks
• Local and national peer communities not available for
operations to reach out to for troubleshooting.
• Proprietary dependence to operate and troubleshoot
equipment.
• Limited national presence.
• Largely unknown process.
• Multiple means for a single point of failure with higher
consequences of failure.
• Process failure requires taking the entire AGS process-
train offline, affecting redundancy and available
capacity.
Pre-Treatment Requirements Single-stage screening and grit-removal.
Operational Considerations Largely unknown process. Operational requirements were
unknown when this report was written.
Chemical Requirements Similar to those of BNR with as-needed use of alum or ferric
chloride for phosphorus removal.
Footprint Slightly smaller compared to that of five-stage BNR Modified
Bardenpho™ process.
Residuals Management WAS produced similar to that of five-stage BNR process.
Energy Use Slightly less energy use compared to what five-stage BNR
process uses due to reduced pumping requirements.
Ease of Expansion/Upgrade Fairly modular construction is possible.
Impact on Neighbors Similar to those of five-stage BNR process.
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2.3.5 Ballasted Activated Sludge – NuvodaTM
Ballasted Activated Sludge (BAS) is based on BNR with one variation: the addition of ballasting
material to the process tanks. The ballast material supplements BNR by significantly improving
the settleability of MLSS in the secondary clarifiers, which allows for higher operational MLSS
concentrations in the process tanks without stressing the secondary clarifiers.
There are several types of ballast material, ranging from the traditional material Magnetite to
more novel organic media like Kenaf. Magnetite is an inert, fully-oxidized, and very fine
magnetic iron material that requires intense mechanical equipment to separate the ballast
media from the waste stream. Kenaf, on the other hand, is a naturally occurring lignocellulosic
material harvested from the rapid-growing Kenaf plant (Hibiscus Cannabinus) that is recycled
with less energy-intensive equipment from the waste stream compared to Magnetite. New
ballast is introduced to the system via a ballast-mixing tank and is recovered from the WAS
streams using recovery drums, which then feed the recovered material back into the
ballast-mixing tank. New ballast is reintroduced to the process stream with the RAS flow to
compensate for any ballast lost through the wasting process since the ballast recovery is not
100 percent efficient. Because BAS can improve the capacity of existing process tanks without
modifying its footprint, it is highly suited as a retrofit process.
Figure 14 shows BAS’s process flow configuration.
Figure 14 Ballasted Activated Sludge (BAS) Flow Diagram
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Table 10 outlines additional considerations and information concerning BAS.
Table 10 Ballasted Activated Sludge (BAS) Fact Sheet
Parameters Description
Proprietary
Process/Equipment
BAS sidestream includes the ballast-mixing tank, dispersion mills, and recovery
drums, which are proprietary equipment. Some examples of ballast material are
magnetite and kenaf.
National Experience/Success No BAS plants in Florida but there are several successful BAS plants across the US.
Process Reliability Comparable to the five-stage BNR process.
Major Advantages
• BAS process can meet AWT effluent water quality goals.
• Volume of the process basins is reduced when compared to that of BNR since
the basins can be operated at higher MLSS concentrations.
Major Drawbacks
• Local and national peer communities not available for operations to reach out
to for troubleshooting.
• Shift in operational strategies and additional operations training required to
operate the ballast-recovery equipment.
• Proprietary dependence to operate and troubleshoot equipment.
• Limited national presence.
• Ballast recovery rates are not 100 percent, so new ballasts are required on an
on-going basis to replenish the wasted amounts. Depending on recovery rates,
sizing of the system, and shipment availability, ballast replenishment can be
an expensive O&M item.
• More mechanical equipment and maintenance needed than what’s required
for BNR.
• More pumping than what’s required for the five-stage BNR process.
Pre-Treatment
Requirements
Single-stage screening and grit-removal. Second stage (fine screening) is
preferred. In the absence of fine screening upstream of the WAS, dedicated WAS
screening may be required.
Operational Considerations
• Proprietary dependence to operate and troubleshoot equipment.
• Ballast and MLSS concentrations must be monitored to schedule ballast
shipments.
Chemical Requirements Similar to the five-stage BNR process.
Footprint
Comparable to BNR. Process basins are smaller than what’s used for BNR, but the
reduced footprint is offset by the space needed for ballast-recovery equipment
and ballast-storage areas.
Residuals Management WAS contains irrecoverable ballasts, which may help with thickening. However,
total solids produced will be higher compared to what’s produced in BNR.
Energy Use Higher energy consumption than what’s consumed for the five-stage BNR process
due to the ballast-recovery equipment.
Ease of Expansion/Upgrade
• Expansion requires additional parallel trains.
• Compared to the five-stage BNR process, additional considerations are
required due to the use of ballast-recovery equipment (shear mills, larger and
additional magnetic drums, larger and additional ballast tanks, and additional
pumps).
Impact on Neighbors
• Noise and odor comparable to those of the five-stage BNR process.
• Ballast system equipment can be contained in a building but will result in
additional truck traffic to the facility.
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2.3.6 Integrated Fixed-Film Activated Sludge
Attached-growth processes, when coupled with suspended-growth processes, provide enhanced
nutrient removal. Integrated fixed-film activated sludge (IFAS) is one such process in which
attached- and suspended-growth biomass is combined within the same reactor.
In IFAS, floating or fixed media is introduced inside the aeration tanks. The combination of
suspended and attached biomass results in a concentration of biomass that is significantly higher
than what can be expected in a suspended-growth process alone. This provides two important
benefits. First, the required volume of the aeration tank is substantially reduced. Second, the
attached biomass places no additional load on the final clarifiers, so the solids loading to the
clarifiers is substantially reduced when compared to what’s imposed by a suspended-growth
process with the same SRT.
Figure 15 shows the IFAS process flow configuration.
Figure 15 Integrated Fixed-Film Activated Sludge (IFAS) Flow Diagram
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Table 11 outlines additional considerations and information concerning IFAS.
Table 11 Integrated Fixed-Film Activated Sludge (IFAS) Fact Sheet
Parameters Description
Proprietary
Process/Equipment
There are several IFAS media and equipment manufacturers, but most are
unique and proprietary. Available types of media include rope, sponge carriers,
hard plastic carriers, trickling filter media, kenaf, and flat sheets.
National
Experience/Success Many installations in the US with more widespread use in Europe.
Process Reliability Comparable to that of five-stage BNR process.
Major Advantages
• Reduced solids loading to clarifiers due to retained biomass in aeration
basins.
• Volume of process basins is reduced compared to that of five-stage BNR
process since the basins can be operated at higher MLSS concentrations.
Major Drawbacks
• Higher dissolved-oxygen concentrations are required in the aerobic tanks
resulting in higher energy usage than what five-stage BNR uses.
• Additional screens are required in the process tanks to retain media in the
tanks. Additional pumping within the process tanks may be required to
move any media clogged on the screens.
• Forward flow velocity through the process tanks is critical to prevent
unequal distribution of media within the tanks.
• Proprietary dependence to replace the media and troubleshoot.
• Taking basins offline for maintenance is problematic since media must be
removed.
Pre-Treatment
Requirements
Single-stage screening and grit-removal is adequate. Screening size depends on
the type of media used. Fine screening may be necessary to prevent blinding of
media-retaining screens.
Operational Considerations
• Normal life-expectancy of the media is 10 to 30 years depending on the
media.
• Proprietary dependence to replace the media and troubleshoot.
• Media retaining screens affect additional hydraulic losses.
• Potential for plugging and media-clogging in the media-retaining screens
thus requiring more maintenance.
• Maintaining the aeration system requires media to be removed and
displaced.
Chemical Requirements Similar to those of five-stage BNR process.
Footprint Smaller than that of the five-stage BNR process but larger than that of MBR.
Residuals Management Similar to that of five-stage BNR process.
Energy Use
Higher energy consumption than that of the five-stage BNR process. The
attached biomass requires higher dissolved-oxygen concentrations, thus
lowering the field-oxygen transfer efficiency. Additional pumping inside the
process basins may result in higher energy demand.
Ease of Expansion/Upgrade Expansion requires additional parallel trains. The capacity of the existing
tankage could be increased to a certain point by introducing additional media.
Impact on Neighbors Similar to those of five-stage BNR process.
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2.4 Structured Decision Analysis
A structured decision analysis was used to characterize the AWT-capable treatment process
alternatives and rank them according to their ability to meet a prioritized set of evaluation
criteria established by the City and Carollo. These five evaluation criteria include:
1. Established Technology,
2. Treatment Effectiveness,
3. Operability,
4. Constructability and Sequencing (Implementability), and
5. Footprint and Flexibility for Future Upgrade.
The City selected a committee to participate in a paired comparison exercise where values (or
weights) were applied to each of the evaluation criterion. These weights ultimately established
the relative importance of each criterion to use in evaluating and comparing the liquid stream
process alternatives. The weighted scores developed by the selection committee were combined
with technical criteria developed by Carollo (representing each alternative’s ability to satisfy the
criteria/sub-criteria) in a decision model. The decision model calculated a unitless “decision
score” and the alternative that best satisfies the most valued criteria (according to the City’s
selection committee) received the highest score. The top two alternatives are further evaluated
in Section 3 of this CDR and include conceptual site layouts and cost estimates (including present
worth).
The evaluation criteria set did not include any economic factors such as capital and operating
costs. Although these costs will be evaluated for the two shortlisted technologies (in Section 3 of
the report), it was intentional to exclude these from the evaluation criteria. Doing so eliminated
any financial bias or appeal for the City to select the “cheapest” alternative.
2.4.1 Process Evaluation Criteria and Sub-Criteria
To effectively measure the performance of each alternative against the five established criteria,
additional sub-criteria were developed to provide a further breakdown for evaluation. The
importance of each sub-criterion was assigned a numerical value by a team of senior wastewater
process specialists within Carollo according to understanding of key project drivers and industry
standards. The sub-criteria were presented to the City’s appointed scoring committee and
given as a rubric to follow when the committee completed the paired comparison exercise in
January 2022. Table 12 lists the five major evaluation criteria, along with their corresponding
sub-criteria.
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Table 12 Major Evaluation Criteria and Corresponding Sub-Criteria
Major Criteria Sub-Criteria
1. Established
Technology
a. Number of installations in the U.S. of similar capacity.
b. Number of installations in Florida of similar capacity.
c. Maturity of process technology.
2. Treatment
Effectiveness
a. Proven processes and technologies for meeting Florida’s AWT
limits.
b. Robustness of treatment (e.g., ability to handle a range of influent
conditions; ease of recovery from upset).
c. Redundancy and reliability.
3. Operability
a. Safe work environment, operational flexibility, complexity of
operation, staffing requirements (e.g., special skills or training),
residuals/process additives production.
b. Process monitoring and control effectiveness (including
industry-recognized process control methods, accessible peers to
discuss process control options, and effective troubleshooting
methods established).
c. Chemical requirements.
d. Maintenance requirements (number and complexity of process
equipment components and required frequency of maintenance,
storage requirements (e.g., for media), special maintenance
equipment).
4. Constructability and
Sequencing
(Implementability)
a. Safe construction.
b. Maintained plant operations, minimize shutdowns
(phasing/sequencing).
c. Potential schedule impacts (e.g., equipment manufacturing and
delivery timeframes).
d. Space requirements for construction.
e. Permitting.
f. OSHA/NFPA requirements.
5. Footprint and
Flexibility for Future
Upgrades
a. Footprint required.
b. Expandability.
c. Adaptability for potential future regulations or effluent uses.
d. Truck traffic impacts.
e. Sustainability (energy use, solids handling).
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2.4.2 Paired Comparison Results
The City formed a selection committee (made up of four City employees of various departments)
to participate in a paired comparison exercise in January 2022. During this exercise, the criteria
were weighted against one another using a paired comparison method. Members of the
selection committee individually and privately scored each of the five criteria against each other
in terms of highest value/prioritization. This ultimately developed the average weight for each
criterion. Results of this exercise are presented in Table 13.
Table 13 Major Evaluation Criteria and their Relative Importance
Major Criteria Average Weight (Percent)
1: Established Technology 18
2: Treatment Effectiveness 23
3: Operability 30
4: Constructability & Sequencing (Implementability) 17
5: Footprint & Flexibility for Future Upgrades 12
The City placed the highest value on Operability, followed by Treatment Effectiveness,
Established Technology, Constructability and Sequencing (Implementability), and lastly
Footprint and Flexibility for Future Upgrade. Footprint and size of the plant is not a concern for
the City since the new WRF will be built on the existing plant site and sufficient area is available,
explaining why that criterion has a lower average weight. By placing the highest average weight
on Operability, the City is emphasizing their value in constructing a WRF that is easy and safe for
operators to operate with minimal additional training.
The unweighted scores from Carollo’s alternative scoring matrix were then combined with the
weights established by the selection committee and inputted into a decision model. The decision
model calculated a unitless “decision score” and the alternative that best met the most valued
criteria (according to the City’s selection committee) received the highest score.
Figure 16 shows the results of the structured decision analysis. Based on the City’s applied values
established by the selection committee, 5-stage BNR and MBR were the top two scoring
technologies. Both of these processes are mature, with a track record of successfully meeting
stringent nutrient discharge limits. BNR was considered to be preferable to MBR in terms of
Operability, which is the most important criterion to the City (average weight of 30 percent).
This is partly attributed to the number and complexity of process equipment components
associated with MBR. On the other hand, MBR scored better than BNR in terms of Footprint and
Flexibility for Future Upgrades. AGS (Nereda) and BAS (Nuvoda) were ranked lower than the
other processes, largely because they did not score well relative to Treatment Effectiveness and
Established Technology.
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Figure 16 Process Alternative Ranking Using Weighted Criteria
These results were discussed and agreed upon with the City at a Process Selection Scoring
workshop held in January 2022. These top two alternatives are further evaluated in Section 3 of
this CDR and include conceptual site layouts and life-cycle cost estimates.
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3.0 Shortlisted Alternatives Evaluation
3.1 Objectives
The decision analysis discussed in Section ͮ resulted in the list of treatment alternatives below,
which are ranked from highest to lowest based on the City’s applied values:
ͭ. ͱ‐stage activated sludge BNR (ͱ‐stage BNR).
ͮ. Membrane bioreactor (MBR).
ͯ. Sequencing batch reactor (SBR).
Ͱ. Ballasted activated sludge (BAS).
ͱ. Integrated fixed‐film activated sludge (IFAS).
Ͳ. Aerobic granular sludge (AGS).
This section of the CDR evaluates the conceptual process modeling, sizing, site layouts, and life
cycle cost estimates for the East WRF’s top two scoring treatment process alternatives: ͱ‐stage
BNR and MBR. A final treatment alternative recommendation will be provided in Section Ͱ to
support the City in making the informed decision of which AWT‐capable process to select for the
upgraded East WRF. An associated conceptual site layout and cost estimate are also provided for
the final recommendation within Section Ͱ.
The design criteria presented in this report are conceptual level and must be further refined
during the Project’s subsequent design stages.
3.2 Conceptual Design Criteria
The following subsection evaluates the design criteria used to conceptually size, layout, and cost
the ͱ‐stage BNR and MBR alternatives. It should be noted that the criteria used to compare the
conceptual designs of the two shortlisted treatment alternatives within this section are not the
final design recommendation for the East WRF at this time. As is explained further below, the
design flows and loads used to compare the BNR and MBR conceptual designs and costs
correspond to a true “buildout” scenario. This scenario represents what the City may require in
the far‐term future, i.e., post‐ͮͬͰͱ, in terms of quantity (population growth) and quality (AWT
requirements). The conceptual designs and costs included within this section are used to
compare/evaluate the two shortlisted treatment alternatives to later make an ultimate design
recommendation. The conceptual design and cost estimate for the final recommended
treatment process – sized for current quantity/quality requirements – is included within Section Ͱ
of this report.
3.2.1 Influent Flows and Loads
The East WRF’s historic wastewater flow and loads were previously analyzed in Section ͭ.ͱ. To
further characterize the facility’s influent wastewater, Carollo relied on historical monthly data
obtained from DMRs over the past three years to identify representative flow and loading
peaking factors, which are key in the design and operation of a WRF. Factors were determined
for a range of conditions including annual average, maximum month, maximum day, and peak
hour.
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Although it is common practice for the capacity of a WRF to be described in terms of the annual
average daily flow (AADF), this value is not used to directly size any unit process or operation.
Rather, sizing is based on the parameters which directly impact the performance of each unit
process or operation. For example, aeration MDL and process volume requirements for BNR
systems are designed around a maximum month average daily mass load (MMADL), while
hydraulic elements such as pipes, pumps, and filters are designed around maximum day (MDF)
or peak hourly flows (PHF), depending on if flow equalization (EQ) is provided.
Appropriate peaking factors for the proposed East WRF were determined based on a
combination of historic data and Carollo’s experience in designing facilities of similar capacity
here in Florida. Maximum month peaking factors and annual average flows and loads were
calculated from historic East WRF influent data over the past three years. Accurate daily and
hourly influent data was unavailable during the conceptual phase of the Project, and thus
standard industry estimating methods were used where applicable for max day and peak hour
factors. References used include the Recommended Standards for Wastewater Facilities (2014)
prepared by the Great Lakes – Upper Mississippi River Board of State and Provincial Public
Health and Environmental Managers (also referred to as the 10-State Standards), and
Munksgaard and Young’s Flow and Load Variations at Wastewater Treatment Plants (1980).
Table 14 lists the East WRF’s proposed design flow and loading peaking factors for the CDR,
determined from the methods described above.
Table 14 East WRF Influent Design Flow and Mass Load Peaking Factors
Peaking Factor(1) Value
Hydraulic Peaking Factors
Maximum Month Average Day Flow (MMADF)(2) 1.1
Maximum Day Flow (MDF)(3) 2.0
Peak Hour Flow (PHF)(4) 3.0
Loading Peaking Factors
Maximum Month Average Day (MMAD) – TSS(2) 1.9
Maximum Month Average Day (MMAD) – cBOD5(2) 1.5
Maximum Day (MD) – TSS(3) 3.5
Maximum Day (MD) – cBOD5(3) 2.4
Notes:
(1) All peaking factors are relative to the long-term annual average day conditions experienced between Jan 2018 and
Oct 2021.
(2) Calculated using East WRF historic influent data from Jan 2018 through Sep 2021.
(3) D.G. Munksgaard and J.C. Young, "Flow and Load Variations at Wastewater Treatment Plants," JWPCF. 52 (8) 1980:
2131-2144.
(4) Fair, G.M. and Geyer, J.C. “Water Supply and Wastewater Disposal” 1st Ed., John Wiley & Sons, Inc., New York (1954),
p. 136.
Carollo recommends that the City perform a detailed influent load and flow analysis during the
subsequent design phase to refine the factors provided in Table 14 to provide the most accurate
design for the East WRF. As they stand, these factors – primarily MMAD TSS and cBOD5 – are
greater than those of typical medium-strength domestic wastewater facilities, which may result
in the oversizing of process basins or mechanical equipment. For example, the historic organic
(i.e., cBOD5) maximum month loading factor was calculated to be 1.5, which is greater than the
typical range of 1.2 to 1.3. A higher loading factor correlates to a greater process volume
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requiring larger basins and greater calculated air demand and consequently, more blowers or
larger blowers to provide the required process air. Due to the cost and process efficiency
implications associated with under or oversizing unit processes, these factors require verification
via a detailed influent sampling campaign.
Table 15 provides the resulting design flows and loads used within the conceptual design for the
two shortlisted technologies based on the factors in Table 14. For the comparison of the
conceptual designs for the BNR and MBR alternatives, a design AAD of 2.1 mgd and PHF of
6.3 mgd was used. A 2.1 mgd design flow evaluates replacement of the East WRF to meet its
existing capacity and avoids de-rating the plant’s capacity. The conceptual design for 2.1 mgd
ultimately represents a true “buildout” scenario, demonstrating what the City may require in the
far-term future, i.e., post-2045, in terms of quantity (population growth) and quality (AWT). A
conceptual design and cost estimate for the final recommended treatment alternative – sized for
today’s needs – is included within Section 4 of this report.
Table 15 Conceptual Influent Design Wastewater Flows and Loads
Parameter Unit Minimum Day AAD(1) MMAD MD PHF(2)
Influent Flow mgd 1.9 2.1 2.3 4.2 6.3
Concentrations
cBOD5 mg/L 150 220 300 260 -
TSS mg/L 120 260 450 450 -
TKN(3) mg/L 30 44 60 50 -
TP(4) mg/L 13 20 28 24 -
Loads
cBOD5 lb/d 2,300 3,800 5,700 9,100 -
TSS lb/d 1,840 4,600 8,700 15,600 -
TKN lb/d 460 770 1,200 1,800 -
TP lb/d 210 350 530 840 -
Notes:
(1) Based on historic East WRF influent from Jan 2018 through Sep 2021.
(2) PHF provided only for the design of hydraulic elements.
(3) Influent TKN: cBOD5 assumed to be 1:5 due to lack of absence of influent nutrient monitoring.
(4) Influent TP: cBOD5 assumed to be 1:11 due to lack of absence of influent nutrient monitoring.
Unit processes for the new East WRF will be sized to handle the targeted design flows and loads
after the applicable peaking factors are applied. The process and hydraulic design of unit
processes will include multiple treatment units, which builds reliability and ensures each
treatment process can be maintained with any one parallel unit removed from service for
inspection or maintenance. The upgraded East WRF will not only meet the minimum Class 1
reliability and redundancy criteria established by the EPA and enforced by FDEP [U.S.
Environmental Protection Agency, Design Criteria for Mechanical, Electric, and Fluid Systems and
Component Reliability (1974, EPA 430-99-74-001)], but also provide operators with unit processes
that can be readily taken offline for maintenance or repair without disrupting the overall
treatment process.
It should be noted that although no low-flow or low-load analysis was performed as part of this
CDR effort, they will be required during the later design phase to ensure mechanical equipment
is properly sized for such scenarios.
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3.2.2 Regulatory Requirements
The treatment goals for the new East WRF were previously established in Section 1.2, Basis for
Conceptual Design. From a process design perspective, one key goal is to ensure that the facility
is capable of meeting AWT requirements in the future (when required).
As mentioned previously, FDEP regulates the discharge of effluent from wastewater treatment
facilities and sets the water quality requirements that reclaimed water must fulfill to comply with
regulations. These regulations may become more stringent in the future, and thus the facility
should be planned for potential future regulations.
For the comparison of the conceptual designs for the BNR and MBR alternatives, the facilities
were designed to meet all AWT requirements. Doing so ultimately represents a true “buildout”
scenario, demonstrating what the City may require in the far-term future, i.e., post-2045, in
terms of quality (meeting AWT). A conceptual design and cost estimate for the final
recommended treatment alternative – designed to meet current effluent requirements – is
included within Section 4 of this report.
3.3 5-Stage BNR Alternative (“Buildout” Scenario: 2.1 mgd with AWT)
The 5-stage BNR process is a conventional activated sludge BNR process that is configured with
the five zones. Ranked as the City’s top AWT-capable alternative, the 5-stage BNR is compared
below to evaluate process design and hydraulic considerations, and ultimately determine a
conceptual site layout for the East WRF. As explained in Section 3.2, this conceptual design for
the 5-stage BNR alternative corresponds to a buildout scenario: 2.1 mgd with AWT-quality
effluent.
The conceptual life cycle cost estimate for this alternative is provided in Section 3.6.
3.3.1 Process Design
The following subsections present the conceptual design criteria for processes associated with
the 5-stage BNR (2.1 mgd with AWT) alternative. The conceptual designs suggested in this
report will meet the minimum Class 1 reliability requirements as established in the Design Criteria
for Mechanical, Electric, and Fluid System and Component Reliability, EPA 1974, and will provide
operators with the flexibility to properly take unit processes out of service for maintenance or
repair without impeding the overall process performance.
3.3.1.1 Headworks
It was determined through a condition assessment that no existing unit process components at
the East WRF have permanent value to be restored. The headworks structure was further
deemed unsuitable for retrofit at the new East WRF due to structural and capacity concerns and
will consequently be demolished with the new design.
The proposed headworks facility will be located just North of the process basins, and will consist
of a common influent channel, a coarse-screening channel with space for two mechanical
screens in parallel, and two equally sized grit-removal units. The screening and grit-removal units
will be hydraulically designed to handle peak hour flows, and all channels will be interconnected
to allow the transfer of flow to either screen, thus reducing potential points of failure within the
headworks facility. To reduce the potential for overflows, the headworks will have an
emergency, passive bypass with an in-line manual bar rack that directs flow to the onsite reject
pond.
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Conceptual screening evaluations determined that each coarse screen must handle a minimum
of 6.3 mgd at PHF, with a proposed screen opening of 6 mm. Several screening technologies can
meet this requirement, such as center flow, multi-rake, and step screens. Further discussions will
be necessary during the design phase to determine which screening technology will best suit the
upgraded East WRF.
Screened material will be washed with facility water and compacted before transfer to a
dumpster for removal and ultimate disposal. Washing the screenings reduces odors and
reintroduces organics into the wastewater stream which are required in the biological process to
reduce the need for supplemental carbon sources, particularly in the second anoxic basins.
However, even if the screenings are washed and organic material is reintroduced, supplemental
carbon may still be required (this is discussed further in Section 3.5.3.1).
Grit-removal will be provided downstream of preliminary screening; however, the exact removal
technology and relevant design criteria will be determined during the design phase. Although
hydraulically designed around PHF to ensure throughput of flow, the grit-removal system
performance will be based around MDF conditions. The system will thus be able to handle flows
up to the PHF, but with slightly reduced removal efficiency (i.e., grit capture efficiency will be
slightly degraded at the PHF). Grit debris removed from the wastewater stream will be washed
to return organics to the biological process, dewatered, and compacted to reduce its weight and
volume before being disposed into the screenings dumpster. Table 16 outlines the proposed
headworks equipment for the 5-stage BNR alternative.
Table 16 Headworks Design Criteria for 5-Stage BNR
Parameter Unit Value
Coarse Screening
Number of Screens # 2
Size of Opening mm 6
Flow Capacity (each) mgd 6.3
Grit System
Number of Units # 2
Design Flow Capacity (each) mgd 4.2
Peak Flow Capacity mgd 6.3
Grit Capture Size μm 105
3.3.1.2 Biological and Secondary Process
Mass balance calculations were performed to determine the BNR process basin sizes, and results
for the 2.1 mgd AADF buildout condition are summarized in Table 17. This table lists the
conceptual design criteria used for the aeration, mixed liquor recycle, secondary clarification,
return activated sludge, and sludge wasting processes.
Mechanical equipment (e.g., chemical feed and blowers) for the BNR system were conservatively
designed around max day loads. Non-aerated zones will be thoroughly mixed to prevent settling
within the BNR basins, but the exact mixing technology and associated design criteria will be
established during the design phase.
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Table 17 Secondary Treatment Design Criteria for 5-Stage BNR
Parameter Unit Value
Plant Influent MDF mgd 4.2
Number of Trains # 4
Liquid Volume
Anaerobic Zone per Train MG 0.03
Anoxic Zone per Train MG 0.13
Aeration Zone per Train MG 0.33
Post Anoxic Zone per Train MG 0.13
Reaeration Basin per Train MG 0.01
Total – All Zones per Train MG 0.63
Total – All Trains MG 2.50
Operating Parameters @ MDF
MLSS in Process Basins mg/L 2,500
Aerobic SRT days 8.2
Total SRT days 16.0
Process Air Required
Actual Oxygen Requirement (AOR) lb/d 10,500
Standard Oxygen Requirement (SOR) lb/d 26,600
Standard Oxygen Transfer Efficiency (SOTE) % 28
Air Requirement scfm 3,900
Number of Blowers # 3 (2 duty, 1 standby)
Blower Size (each) hp 125
RAS
Total Flow mgd 4.2
Number of Pumps # 3 (2 duty, 1 standby)
WAS
Total Flow gpd 67,300
Number of Pumps # 5 (4 duty, 1 shelf spare)
Internal Recycle
Total Flow mgd 12.6
Number of Pumps # 3 (2 duty, 1 standby)
Clarification
Number of Clarifiers # 3
Diameter ft 70
Surface Area (each) ft2 3,850
Sludge Volume Index (SVI) mL/g 150
RAS Return Ratio - 1.0
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3.3.1.3 Filtration
Tertiary filters for the 5-stage BNR alternative were sized based on modern cloth media disk
filter design criteria. Average and maximum hydraulic loading rates of 5.1 and 6.5 gallons
per minute per square foot (gpm/ft2), respectively, were assumed with a peak influent hydraulic
flow of 6.3 mgd. The proposed filter system design criteria is summarized in Table 18.
For the East WRF conceptual design, three new filters will be constructed to remove suspended
solids from the waste stream and will be equipped with 5 disks per unit. Each filter will have a
peak capacity of 3 mgd, thus achieving Class 1 reliability which requires adequate filtration
capacity to treat 75 percent of the PHF with the largest unit out of service.
Table 18 Filter Design Criteria for 5-Stage BNR
Parameter Unit Value
Plant Influent AADF mgd 2.1
Plant Influent Peak Hour Flow mgd 6.3
Number of Filters # 3
Number of Disks per Filter # 5
Surface Area per Disk ft2 53.8
Total Surface Area ft2 807
Hydraulic Loading Rate (Average) gpm/ft2 1.8
Hydraulic Loading Rate (Peak)(1) gpm/ft2 5.4
Peak Capacity per Filter mgd 2.5
Total Maximum Capacity (All Filters Online) mgd 7.5
Firm Capacity (One Filter Out of Service) mgd 5.0
Notes:
(1) Maximum hydraulic loading rate of 6.45 gpm/ ft2 used based on a recent design of a WRF of similar capacity to that of
East WRF.
3.3.1.4 Chlorine Contact Chamber
The existing East WRF uses liquid sodium hypochlorite for disinfection. The existing chlorine
contact basin was assessed to determine if it can be repurposed for the new facility. Structurally,
the chlorine contact chamber is in acceptable condition and could be rehabilitated to lower
construction costs, including new repumping equipment costs. Some components still require
replacement, such as the effluent gates. Additionally, a new chlorine contact chamber may still
be required if the existing does not fit into the hydraulic profile of the new plant. This should be
further evaluated during later design stages.
Consequently, for conceptual design purposes, a new chlorine contact basin will be constructed.
The design is based on Class 1 reliability and HLD disinfection requirements. Class 1 reliability
requires a design flow capacity of at least 50 percent of the total design flow with the largest unit
out of service. The HLD requirements outlined in 62-600.440 F.A.C requires: 1) a minimum
chlorine residual of 1.0 mg/L is maintained at all times and 2) the minimum acceptable contact
time is at least 15 minutes at PHF. HLD also requires a specific CT (i.e., Concentration x Time) for
treated wastewater based on the observed fecal coliform concentration, before disinfection.
Because the new East WRF is designed to treat to AWT, it is assumed that the 1,000 fecal
coliforms per 100 mL limit applies, and thus a CT of 25 mg-min/L will be required.
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For the new East WRF, disinfection will be provided by dosing 12.5 trade percent liquid sodium
hypochlorite into two equally sized chlorine contact chambers sized for PHF. The total chlorine
contact volume provided for the 5-stage BNR alternative will be 65,600 gallons. The contact
time at the peak hourly flow of 6.3 mgd would be 15 minutes, thus meeting the minimum
requirements established by 62-600.440 F.A.C. For a CT of 25 mg/L-min, the minimum chlorine
residual would be 1.67 mg/L. New sodium hypochlorite storage and feed systems would be
required at the East WRF due to the condition of the existing system. Preliminary calculations
revealed that, for a conservative sodium hypochlorite dose of 8 mg/L, a 30-day storage volume
equates to 8,000 gallons of 12.5 percent sodium hypochlorite solution at MDF conditions. Thus,
two 4,000-gallon storage tanks with two chemical feed pumps will be provided.
Table 19 provides a summary of the proposed 5-stage BNR disinfection capacity.
Table 19 Chlorine Contact Chamber Design Criteria for 5-Stage BNR
Parameter Unit Value
Plant Influent AADF mgd 2.1
Plant Influent Peak Hour Flow mgd 6.3
Disinfectant Type - Sodium Hypochlorite (NaOCl)
Concentration % 12.5
Number of Trains # 2
Volume per Train gal 32,800
Total Volume gal 65,600
Contact Time (AADF) min 45
Contact Time (PHF) min 15
Design CT mg/L-min 25
Min Chlorine Residual (AADF) mg/L 1.0(1)
Min Chlorine Residual (PHF) mg/L 1.67
Number of Chemical Storage Tanks # 2
Tank Capacity (each) gal 4,000
Number of Feed Pumps # 2 (1 duty, 1 shelf spare)
Feed Pump Capacity (each) gph 12
Notes:
(1) The actual required chlorine residual is 0.55 mg/L, but a minimum of 1.0 mg/L will be provided as required for HLD.
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3.3.2 Conceptual Site Layout
Figure 17 presents a conceptual site layout for an AWT-capable, 5-stage BNR facility at 2.1 mgd.
The facility will be constructed at the existing East WRF site (1560 Winter Springs Boulevard,
Winter Springs, FL 32708) with a primary flow path from north to south. The conceptual BNR
layout includes a new headworks facility located at the north-end of the facility, consisting of
two 6-mm coarse screens and two grit-removal systems upstream of secondary treatment. The
secondary treatment is comprised of five basins in a Modified BardenphoTM configuration,
comprised of an anaerobic zone followed by an anoxic and aeration zone, a post-anoxic zone,
and a reaeration zone. These five zones provide a total secondary treatment basin volume of
2.5 MG. Flow is then directed to a new MLSS splitter box and three 70-foot-diameter clarifiers,
which are designed such that one whole unit can be taken out of service without interrupting the
plant process or its efficiency. The effluent from the clarifiers then flows through three new cloth
media disk filters for tertiary filtration, and finally to the chlorine contact basin. From there, the
transfer pump station can divert flow to either PAR, the onsite 3-MG RW storage tank, reject
pond, or alternate disposal method (i.e., RIB or spray field). These proposed site plan also
includes a new odor control facility, blower/electrical building, RAS/WAS pump station, chemical
storage and pumping, and a reject return/backwash return pump station.
This conceptual site layout for the 5-stage BNR alternative represents a buildout scenario of
2.1 mgd with AWT-quality effluent. A proposed conceptual site layout for the ultimate treatment
recommendation at the East WRF is included in Section 4 of this CDR.
392
FIGURE 1SITE LAYOUT2.1 MGD BNREAST WRF®SCALE80'40'0Aerial Photography Source: FDOT APLUS March, 2019NOTES:LEGEND:BUILD-OUT - 2.1 MGD AADF WITH AWTWWTP No. 2OPERATIONSBUILDINGBLOWERROOMELECTRICALROOMGENERATORROOMWWTP No. 1NEWCLARIFIERNo.1NEW BLOWER BUILDING/ELECTRICAL BUILDING #1CHLORINE CONTACT BASINREJECT PUMP STATIONTRANSFER PUMP STATIONDIGESTERNo. 3PLANTENTRANCEGATE5.61 MGREJECT AND WETWEATHER LINEDSTORAGE POND3.0 MGRECLAIMED WATERSTORAGE TANKFUTURERECLAIMED WATERSTORAGE TANKELECTRICALBUILDINGRECLAIMED WATER DISTRIBUTIONPUMP STATIONDEMOLITION AREA(SEE NOTE 1)NEWCLARIFIERNo.2FUTURECLARIFIERNo.3NEW RAS/WASPUMP STATIONPADNEW MLSSSPLITTER BOXNEW DISK FILTERS(SEE NOTE 5)NEW REJECT RETURN/BACKWASH RETURN AND IN-PLANTRECYCLE PUMP STATIONSODIUM HYPOCHLORITESTORAGE AND PUMPINGNEW CHLORINE CONTACT BASINNEW TRANSFERPUMP STATION2.5 MGBNRTRAIN
N
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.
1
TRAIN
N
o
.
2
TRAIN
N
o
.
3 NEW HEADWORKS INCLUDINGSCREENING AND GRIT REMOVALELECTRICAL BUILDING No. 2TERTIARY FILTERSNEW ODOR CONTROLFACILITYCONNECT TO EXISTINGCOLLECTION SYSTEM(SEE NOTE 2)CONNECT TO EXISTINGRECLAIMED WATER SYSTEM(SEE NOTE 2)TRAIN
N
o
.
4
1.AFTER NEW PROCESS EQUIPMENT IS IN SERVICE,STRUCTURES AND EQUIPMENT WITHIN THIS AREACAN BE DEMOLISHED AS NEEDED. THIS AREA CAN BEUSED FOR NEW OPERATION BUILDING AND PARKING,SLUDGE STORAGE AND HANDLING, ETC.2.CONCEPTUAL YARD PIPING LAYOUT SHOWS JUST THEPRIMARY FLOW PATH THROUGH THE PLANT.Figure 17393
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3.3.3 Hydraulic Considerations
As described in Section 1.4, the condition assessment of existing processes revealed that there is
too much risk associated with preserving existing unit processes in the new East WRF design due
to structural concerns and hydraulic limitations. With this in mind, the hydraulic profile for the
5-stage BNR alternative was developed by selecting the existing reject pond elevation to serve as
the key hydraulic control point. From this setpoint, calculations were performed to set the
required elevations upstream of the reject pond and transfer pump station to ensure gravity flow
throughout the facility.
Once the hydraulic profile was generated, the final water surface elevations were predicted for
each of the key treatment process areas. It should be noted that calculations were performed at
the 2.1 mgd flow rate with one treatment train offline for each key process area. This includes
one screen at the headworks, one biological treatment train, one secondary clarifier, and
one tertiary filter. This conservative approach accounts for the hydraulic capacity when unit
processes are out of service, thus ensuring redundancy and reliability are maintained for
‘worst-case’ conditions. The resulting water surface elevations for each process area are
presented in the hydraulic profile of the 5-stage BNR alternative (Figure 18).
394
FIGURE 4CONCEPT HYDRAULIC PROFILE2.1 MGD BNREAST WRF®NOTE:LAST TWO DIGITS ONLY OF ELEVATIONS ARE SHOWN FOR CLARITY4035302520151051.THIS HYDRAULIC PROFILE IS A CONCEPT TO SHOW THAT THE PROFILE WILL FIT WITHIN EXISTING CONDITIONS.2.RAS RECYCLE FLOWS: 100% INFLUENT FOR AVERAGE ANNUAL DAY FLOW OF 2.1MGDWATER SURFACE ELEVATION AT 2.1 MGD (ANNUAL AVERAGE DAILY FLOW)T/WALLEL 37.59T/WEIRGATEEL 35.20T/WALL EL35.91WEIR EL 30.6020" FE PIPE28.2130.11DISK FILTERS(3 UNITS)NEW MLSPLITTER BOX20" ML PIPECLARIFIER NO. 3SCREENMECHANICAL(2 UNITS)38.78T/WALLEL 42.4320" RWW PIPENEW GRITCHAMBER(2 UNITS)T/WALL EL 39.93T/WEIR EL 37.00NEW BNR BASINANAEROBICANOXICAEROBICANOXICAEROBIC24" ML PIPENEW35.5934.7020" ML PIPETO NEW CLARIFIER NO. 120" ML PIPE20" ML PIPENEW CLARIFIERNO.2NEW CLARIFIERNO.133.91V-NOTCHWEIR 33.833.31DISKFILTERS20" ML PIPETO CLARIFIER NO. 3TO CHLORINECONTACT TANK39.184550120.64121.30WATER SURFACE ELEVATION AT 6.3 MGD (PEAK HOUR FLOW)38.2337.8335.4534.0733.8732.43403530252015105455036.4935.6837.9337.7437.5337.34V-NOTCHWEIR 33.8V-NOTCHWEIR 33.833.9133.3133.8732.4333.9133.3133.8732.43FROMCLARIFIERNO. 1DISKFILTERSDISKFILTERS32.6132.3530.8531.11FROMCLARIFIERNO. 2 AND 340.4339.4820"20"PUMPING TO GSTT/WEIR EL 27.7528.25CCT TRANSFERPUMP STATION28.00CHLORINECONTACT TANK3025201560553527.2427.01M12"EXISTING WEATHERSTORAGE/REJECTPOND24"24"FROM TRANSFERPUMP STATIONEXISTING RECLAIMEDWATER GROUNDSTORAGE TANK20"RECLAIMED WATERGROUND STORAGETANK (FUTURE)58.42FROM TRANSFERPUMP STATIONTO RECLAIMED WATERPUMP STATION58.42TO RECLAIMED WATERPUMP STATIONHWL EL 24.15REJECT PONDDISCHARGE EL 25.3430252015605535FROMFILTERS20" ML PIPETO CLARIFIER NO. 2Figure 18395
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3.4 MBR Alternative (“Buildout” Scenario: 2.1 mgd with AWT)
MBR is a variation of 5-stage BNR in which membrane tanks and equipment replace secondary
clarifiers and tertiary filters. Ranked as the City’s second highest scoring AWT-capable
alternative, the MBR process is compared below to evaluate process design and hydraulic
considerations, and ultimately determine a conceptual site layout for the East WRF. As explained
in Section 3.2, this conceptual design for the MBR alternative corresponds to a buildout scenario:
2.1 mgd with AWT-quality effluent.
The conceptual life cycle cost estimate for this alternative is provided in Section 3.6.
3.4.1 Process Design
This section presents the conceptual design criteria for several processes associated with the
MBR treatment alternative at 2.1 mgd with AWT.
3.4.1.1 Headworks
The proposed MBR layout will have the same preliminary treatment processes as those of the
5-stage BNR, including two coarse-screening channels, a bypass channel with a manual bar rack,
and a grit-removal system. However, the layout for these processes is different for the MBR
alternative due to the addition of flow EQ and fine-screening. The coarse screens, grit removal
units, and fine screens will all be hydraulically designed to handle 100 percent of the PHF with
one unit out of service. Flow EQ will be provided downstream of the fine screens to attenuate
flow to the membranes such that peak flows are of similar magnitude to max day events (i.e., EQ
reduces peak flows from 6.3 to 4.2 mgd).
Coarsely screened, degritted flow will pass through two fine screens with 2-mm perforated
openings to remove fine particles that may damage the membranes. The fine-screenings will
require washing and compaction equipment similar to the coarse screens, and each component
of the MBR headworks will have the ability to be bypassed to the onsite reject pond in case of
high-flow or maintenance events. However, all flow must pass through the fine screens prior to
secondary treatment to protect the membrane filters. Table 20 outlines the proposed design
criteria for the MBR headworks.
Table 20 Headworks Design Criteria for MBR
Parameter Unit Value
Coarse Screening
Number of Screens # 2
Size of Opening mm 6
Flow Capacity (each) mgd 6.3
Flow Equalization
Number of Units # 1
Basin Size MG 0.53
Grit System
Number of Units # 2
Flow Capacity mgd 6.3
Grit Capture Size μm 105
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Parameter Unit Value
Fine Screening
Number of Screens # 2
Size of Opening, Perforated mm 2
Flow Capacity of (each) mgd 6.3
3.4.1.2 Biological and Secondary Process
A process mass balance was performed to identify the required basin sizes to treat East WRF’s
predicted maximum day flow and loads for the MBR alternative. The layout for MBR is similar to
5-stage BNR in the sense that both have the same five key BNR process basins. One key benefit
of MBR compared to 5-stage BNR and other CAS alternatives is that the MBR process basins are
approximately half of the volume. This has some tradeoffs, as the thicker mixed liquor in MBR
systems requires greater blower capacity to meet the required oxygen demand compared to
CAS systems. MBR also distinguishes itself from 5-stage BNR because the membrane systems
perform liquid-solids separation and filtration, thus no clarifiers or tertiary filters are required.
Effluent from the four BNR trains will flow to a common influent channel to be distributed to
four MBR trains. A fifth MBR train will also be constructed to provide 100 percent reliability in
case one train needs to be taken offline for maintenance, and the basic infrastructure for a
sixth future train can be constructed since costs would be negligible.
Each MBR train will have space for five membrane modules, but only three will be required to
achieve target effluent limits. Additionally, each module can house a total of 48 membrane
cassettes but the City may choose to install fewer initially to retain space for future cassette
installations. If the influent flow at East WRF increases in the future, then additional treatment
capacity can be readily added by either constructing additional MBR trains or installing more
modules or cassettes in the existing trains. Thus, this alternative provides great flexibility for
increasing treatment capacity if needed in the future.
WAS and RAS will be pumped from a common influent and effluent channel in the membrane
basins to the SHT and the aeration basin, respectively. MBR also has two internal recycle
streams to help balance the biomass inventory and prevent the overloading or fouling of the
membrane filters. On a final note, small blowers will be required to provide air scouring to
further mitigate membrane fouling. Table 21 details the equipment and operating parameters
required for the MBR system design, including basin volumes, MLSS, SRT, and process air
requirements.
Table 21 Secondary Treatment Design Criteria for MBR
Parameter Unit(1) Value
Plant Influent AADF mgd 2.1
Plant Influent MDF mgd 4.2
BNR Process Basin Liquid Volumes
Number of Trains # 4
Anaerobic Zone per Train MG 0.01
Anoxic Zone per Train MG 0.07
Aeration Zone per Train MG 0.17
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Parameter Unit(1) Value
Post Anoxic Zone per Train MG 0.06
Reaeration Zone per Train MG 0.01
Total - All Zones per Train MG 0.32
Total-All Trains MG 1.27
Operating Parameters @ MDF
MLSS in Process Basins mg/L 3,750
Aerobic SRT days 8.4
Total SRT days 16
Process Air Required
Actual Oxygen Requirement (AOR) lb/d 10,500
Standard Oxygen Requirement (SOR) lb/d 33,300
Standard Oxygen Transfer Efficiency (SOTE) % 28
Air Requirement scfm 4,900
Number of Blowers # 3 (2 duty, 1 standby)
Blower Size (each) hp 150
Internal Recycle (Aeration to Anoxic)
Total Flow mgd 12.6
Number of Pumps # 3 (2 duty, 1 standby)
Internal Recycle (Anoxic to Anaerobic)
Total Flow mgd 8.4
Number of Pumps # 3 (2 duty, 1 standby)
Membrane Basins
Number of Trains # 5 (4 duty, 1 standby)
Number of Membrane Modules per Train # 3
Membrane Cassettes per Module # 48
Air Scour Blowers
Total Aeration Rate scfm Variable 300 to 600
Number of Blowers # 5 (4 duty, 1 standby)
Max Blower Discharge Pressure psig 7.0
Blower Size (each) hp 30
RAS
Total Flow mgd 16.8
Number of Pumps # 3 (2 duty, 1 standby)
WAS
Total Flow gpd 45,800
Number of Pumps # 2 (1 duty, 1 standby)
Notes:
(1) MDF equals PHF for the MBR alternative because influent flow is attenuated by flow EQ.
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3.4.1.3 Chlorine Contact Chamber
The existing chlorine contact basin was assessed to determine if it can be repurposed for the new
facility. Structurally, the chlorine contact chamber is in acceptable condition and could be
rehabilitated to lower construction costs, including new repumping equipment costs. Some
components still require replacement, such as the effluent gates. Additionally, a new chlorine
contact chamber may still be required if the existing does not fit into the hydraulic profile of the
new plant. This should be further evaluated during later design stages. For the conceptual
design, a new chlorine contact chamber is proposed.
Disinfection will be provided by dosing 12.5 trade percent sodium hypochlorite solution into
two equally sized chlorine contact chambers sized for the attenuated PHF of 4.2 mgd. The total
chlorine contact chamber volume for MBR is lower than that provided for the 5-stage BNR
alternative because of the addition of flow EQ. Conceptual evaluations calculated a chlorine
contact volume of 43,800 gallons. The resulting contact time at the peak hourly flow of 4.2 mgd
would be 15 minutes, thus meeting the minimum requirements established by 62-600.440 F.A.C.
For a CT of 25 mg/L-min, the minimum chlorine residual would be 1.67 mg/L. The same design
criteria used for the 5-stage BNR alternative would be required for the MBR system because the
same chlorine dose of 8 mg/L is proposed for MDF conditions, however slightly more sodium
hypochlorite is required for MBR systems due to the need for maintenance and recovery cleans
(discussed in Section 3.5.1.3). Thus, two 4,500 gallon storage tanks with two sodium
hypochlorite feed pumps are provided in this conceptual design to meet the suggested 30-day
storage volume.
Table 22 provides a summary of the proposed MBR system disinfection capacity.
Table 22 Chlorine Contact Chamber Design Criteria for MBR
Parameter Unit Value
Plant Influent AADF mgd 2.1
Attenuated Influent Peak Flow(1) mgd 4.2
Disinfectant Type - Sodium Hypochlorite (NaOCl)
Concentration % 12.5
Number of Trains # 2
Volume per Train gal 21,900
Total Volume gal 43,800
Contact Time (AADF) min 30
Contact Time (PHF) min 15
Design CT mg/L-min 25
Min Chlorine Residual (AADF) mg/L 1.0(2)
Min Chlorine Residual (PHF) mg/L 1.67
Number of Tanks # 2
Tank Capacity (each) gal 4,500
Number of Feed Pumps # 2
Feed Pump Capacity (each) gph 12.5
Notes:
(1) Influent PHF will be attenuated by the EQ basin.
(2) The actual required chlorine residual is 0.83 mg/L, but a minimum of 1.0 mg/L will be provided as required for HLD.
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3.4.1.4 MBR Cleaning Chemicals
To achieve the desired degree of treatment, the MBR system must be maintained via two
cleaning methods: 1) maintenance cleans, and 2) recovery cleans, which require specific cleaning
chemicals depending on the type of membrane foulant present.
Maintenance cleans both sustain the system’s desired transmembrane pressure and increase the
time between recovery cleans. Under this cleaning type, sodium hypochlorite is applied to
remove organic foulants while citric acid is applied to remove inorganic foulants. One membrane
train is cleaned at a time, while the remaining trains continue to treat the plant’s flow.
Maintenance cleans are generally performed without removing the membrane cassettes from
the membrane tank. The membranes temporarily stop filtering the flow and are back-pulsed
with the appropriate chemicals, which pass through the membranes and are consumed by the
mixed liquor present in the membrane tank.
Recovery cleans are an intensive cleaning operation performed when the membranes’
permeability is less than 50 percent of the initial stable permeability. The same two chemicals —
sodium hypochlorite and citric acid — are used and, compared to maintenance cleans, recovery
cleans generally consume more chemicals.
Storage volume for the cleaning chemicals must be sufficient to accommodate several recovery
and maintenance cleans. The proposed cleaning system will use IBC totes citric acid, while
sodium hypochlorite will be stored in a shared storage tank used for MBR cleaning and primary
disinfection. Both chemical storage facilities will have sufficient storage capacity to handle
30-days’ worth of maintenance and recovery cleans. Two chemical dosing pumps will be
provided for sodium hypochlorite as discussed above, and a single pump will be sufficient to dose
citric acid. Because the required storage for citric acid is minimal, a small holding pad capable of
storing 3 IBC totes is suggested. Then, when recovery cleans are needed, operators can transport
a single IBC to the citric acid pump station for cleaning. Table 23 details the proposed MBR
chemical cleaning storage and feed systems.
Table 23 MBR Chemical Cleaning System
Parameter Unit Quantity
Sodium Hypochlorite
Concentration % 12.5
Required Storage gal 1,900
Number of IBC Totes # 7
Number of Sodium Hypochlorite Pumps # 2
Citric Acid
Concentration % 50
Required Storage gal 700
Number of IBC Totes # 3
Number of Citric Acid Pumps # 1
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3.4.2 Site Layout
Figure 19 presents the conceptual site layout for an AWT-capable MBR facility with a design flow
of 2.1 mgd. The conceptual facility will be constructed at the existing East WRF site (1560 Winter
Springs Boulevard, Winter Springs, FL 32708) with a primary flow path going north to south. The
conceptual MBR headworks facility will be located at the north-end of the facility. Raw
wastewater will first flow through 6-mm coarse screens, grit removal, 2-mm fine screens, and
finally through an off-line equalization (EQ) basin to protect the MBR system from sharp
fluctuations in influent flow. Screened, degritted, equalized flow will be collected in a common
effluent channel prior to flowing to secondary treatment.
MBR uses suspended microbial growth in the process basins and membrane filters for
solids-liquids separation. The membrane filters also achieve tertiary filtration prior to
disinfection, thus removing the need for both secondary clarifiers and filters. In contrast to
5-stage BNR, the MLSS concentrations in the aeration basins within an MBR process are neither
limited by the solids-loading capacity of secondary clarifiers, nor influenced by the settling
characteristics of activated sludge. Hence, MBR configurations are referred to as ‘intensification
processes’ because they can handle significantly higher MLSS concentrations in a much smaller
footprint compared to CAS processes, while still achieving the effluent limits required by AWT.
The conceptual MBR configuration consists of four BNR trains in a Modified BardenphoTM
configuration for a total volume of 1.27 MG. This is then followed by five MBR trains with
three membrane modules each, as well as the associated aeration and RAS/WAS systems.
Following membrane filtration, permeate pumps will distribute treated effluent to the chlorine
contact chamber for final disinfection. From there, the transfer pump station can divert flow to
either PAR, the onsite 3-MG RW storage tank, reject pond, or alternate disposal method (i.e., RIB
or spray field). The conceptual site plan also includes a new odor control facility, blower/electrical
building, chemical storage and pumping, and a reject return/backwash return pump station.
This conceptual site layout for the MBR alternative represents a buildout scenario of 2.1 mgd
with AWT-quality effluent. A proposed conceptual site layout for the ultimate treatment
recommendation at the East WRF is included in Section 4 of this CDR.
401
FIGURE 3
SITE LAYOUT
2.1 MGD MBR
EAST WRF
®
SCALE
80'40'0
Aerial Photography Source: FDOT APLUS March, 2019
1.AFTER NEW PROCESS EQUIPMENT IS IN SERVICE,
STRUCTURES AND EQUIPMENT WITHIN THIS AREA
CAN BE DEMOLISHED AS NEEDED. THIS AREA CAN BE
USED FOR NEW OPERATION BUILDING AND PARKING,
SLUDGE STORAGE AND HANDLING, ETC.
2.CONCEPTUAL YARD PIPING LAYOUT SHOWS JUST THE
PRIMARY FLOW PATH THROUGH THE PLANT.
NOTES:
LEGEND:
BUILD-OUT - 2.1 MGD AADF MBRWWTP No. 2
OPERATIONS
BUILDING
BLOWER
ROOM
ELECTRICAL
ROOM
GENERATOR
ROOM
WWTP No. 1
NEW BLOWER BUILDING/
ELECTRICAL BUILDING #2
CHLORINE CONTACT BASIN
REJECT PUMP STATION
TRANSFER PUMP STATION
DIGESTER
No. 3
PLANT
ENTRANCE
GATE
5.61 MG
REJECT AND WET
WEATHER LINED
STORAGE POND
3.0 MG
RECLAIMED WATER
STORAGE TANK
FUTURE
RECLAIMED WATER
STORAGE TANK
ELECTRICAL
BUILDING
RECLAIMED WATER DISTRIBUTION
PUMP STATION
DEMOLITION AREA
(SEE NOTE 1)
NEW RAS/WAS
PUMP STATION
PAD
IN-PLANT RECYCLE/DRAIN PUMP STATION
SODIUM HYPOCHLORITE
STORAGE AND PUMPING
NEW CHLORINE CONTACT BASIN
NEW TRANSFER
PUMP STATION
BNR
TRAIN No. 1NEW HEADWORKS STRUCTURE4INCLUDING
COURSE SCREENING, GRIT REMOVAL AND FINE SCREENING
TERTIARY FILTERS
NEW ODOR CONTROL
FACILITY
CONNECT TO EXISTING
COLLECTION SYSTEM
(SEE NOTE 2)
CONNECT TO EXISTING
RECLAIMED WATER SYSTEM
(SEE NOTE 2)TRAIN No. 2TRAIN No. 3TRAIN No. 40.53 MG
EQUALIZATION
TANK
MBR
BASIN
MBR BLOWERS
REJECT RETURN
PUMP STATION
NEW ELECTRICAL
BUILDING #1
Figure 19
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3.4.3 Hydraulic Considerations
MBR systems produce treated water, referred to as permeate, that is typically pulled through the
membrane system via pumps. Because this permeate is repumped, the plant’s flow is not as
restricted by elevation compared to the 5-stage BNR alternative, which relies on gravity flow. In
general, MBR hydraulics are more flexible than for 5-stage BNR because there are fewer
constraints (e.g., no secondary clarifier weirs). Additionally, the flow EQ provided in the
headworks allows for downstream processes to be sized around a smaller peak flow.
Permeate pumps will be sized to transfer flow to the chlorine contact tanks, and RAS and WAS
will be collected via common effluent and influent channels in the MBR tank, respectively.
3.5 Common Processes and Shared Facilities
The 5-stage BNR and MBR alternatives share several common process components, all of which
have minimal effects on their evaluation and comparison. Regardless of the selected treatment
alternative, these common processes are essential to their treatment performance and any
minor differences between the two alternatives are discussed in the respective subsections
below.
3.5.1 Odor Control Technology
As discussed in Section 1.3.5, Webster completed an odor survey at the existing East WRF in
November 2021. This study was done to assess the existing H2S odor impact on the local area
and provide a general, high-level discussion of potential order control technologies that may be
appropriate with the design of the new WRF.
Webster noted in their Hydrogen Sulfide Monitoring Report (which can be found in Appendix D),
that a number of odor control technologies may be considered for the proposed East WRF,
including bioscrubbers (also known as biotrickling filters), engineering media biofilters, wood
media biofilters, carbon adsorbers, chemical scrubbers, photoionization, ozone, thermal
oxidizers, and others. Based on Webster’s experience at similar facilities in Florida, three of the
mentioned technologies were further evaluated within their report:
• Bioscrubbers – suitable for applications with moderate-to-high H2S,
• Biofilters – suitable for applications with low-to-moderate H2S and other larger-reduced
sulfur compounds (RSCs), and
• Carbon Adsorbers – suitable for applications with low H2S and can act as a polishing
stage downstream of a biological system (2nd stage of a two-stage system).
All three of these technologies have known odor-removal mechanisms with proven performance
and can be recommended as the odor control technology for the proposed East WRF. Exact
technology selection and sizing are beyond the scope of conceptual design and should be
evaluated within later design stages.
3.5.2 Chemical Systems
In addition to sodium hypochlorite for disinfection, facilities for the following bulk chemical
storage and feed systems will be required at the new East WRF:
• Supplemental carbon,
• Chemicals for phosphorus precipitation, and
• Cleaning chemicals (for MBR).
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The following subsections provide background regarding the need and purpose for each of the
chemicals listed above. Although conceptual estimates for chemical storage and feed systems
are provided below, these values should be further refined during the Project’s design phase. For
this conceptual design, between 7- and 30-days of chemical storage are suggested to protect
against emergency weather events and supply chain uncertainties. Additionally, storage tanks
will be adequately sized to accept full-load quantities in order to prevent the increased delivery
costs associated with chemical short-loads. All chemical storage and feed systems will be
equipped with the appropriate safety protection devices, including 150 percent chemical
containment, eyewash stations, alarm beacons, etc. Sun protection will also be provided for all
chemicals to prevent ultraviolet degradation.
3.5.2.1 Supplemental Carbon
The East WRF’s ability to efficiently denitrify and meet stringent effluent nitrogen limits
(a requirement of AWT) partially depends on the availability of carbon in the system.
Supplemental carbon is used when there is insufficient endogenous organic carbon in the
process basins to achieve denitrification and meet permitted effluent nitrogen requirements.
Supplemental carbon not only enhances the denitrification capacity by removing the biological
process’s organic carbon bottleneck, but also aids in biological phosphorous removal.
Numerous sources of supplemental carbon exist including methanol, ethanol, glycerin products,
and alternative products such as whey or corn syrup. Methanol and ethanol, although used in
wastewater treatment facilities, are highly flammable and present significant explosion hazards.
Hence, their storage and feed systems have to be carefully designed with special systems in
place to ensure that the risk of fires and explosions are mitigated. Glycerin-based products are
colorless, odorless, viscous liquids produced as byproducts of biodiesel production and are
environmentally friendly, sustainable supplies of supplemental carbon. Additionally, several
biodiesel and chemical-production companies offer proprietary carbon-based products.
Manufactured by EOSi, MicroC 2000 is a glycerin-based proprietary product that is commonly
used in wastewater treatment facilities. It has readily biodegradable COD (rbCOD)
concentrations of over 1,000,000 mg/L. MicroC 2000 is non-toxic, non-flammable and, unlike
other carbon sources such as methanol, does not require special handling methods. It is typically
shipped as 70 to 74 percent glycerol and 26 to 30 percent water in quantities that range from as
low as 5 gallons up to large bulk shipments of 4,600 gallons. Chemical facilities for MicroC are
simple and neither require special construction or materials to store or pump, nor does it readily
degrade or off-gas like sodium hypochlorite.
Preliminary calculations revealed that a MicroC dose of 115 gpd would be required at max month
conditions to aid in achieving the effluent nitrogen limit of 3 mg/L required for AWT. Thirty days
of supplemental carbon storage is suggested, resulting in 3,500 gallons of storage. However, to
help prevent against the increased rates associated with short loads, a 5,000-gallon storage tank
is suggested with two chemical feed pumps. Table 24 outlines the design criteria for the
proposed supplemental carbon storage and feed facility.
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Table 24 Supplemental Carbon Storage and Feed Design Criteria
Parameter Unit Quantity
Carbon Source - MicroC 2000
Required Dose gpd 115
Number of Tanks # 1
Tank Capacity gal 5,000
Number of Feed Pumps # 2
Feed Pump Capacity (each) gph 5
3.5.2.2 Chemicals for Phosphorus Precipitation
To further remove phosphorus from wastewater, many utilities use metal salts to promote the
chemical precipitation of phosphorus, followed by sedimentation and filtration. When metal
salts react with soluble phosphate, insoluble solids (i.e., precipitates) are formed that can be
removed from the system via waste sludge. Chemicals such as aluminum sulfate (alum) are
typically added near the end of the BNR process basins where they form a precipitate, such as
aluminum phosphate.
Alum is a metal salt commonly used for coagulation and flocculation and chemical phosphorus
removal and can be shipped in a liquid form in intermediate bulk container (IBC) totes, roughly
1,000 L in size, or in bulk shipments. It forms a corrosive, low-pH solution which is typically
diluted in water as 48 percent alum by weight. Alum is a non-flammable liquid which, without a
flashpoint, does not show oxidizing properties and is not reactive with water. This conceptual
design will provide operators with the flexibility to dose alum at the following locations:
1. Head of the BNR trains,
2. Influent stream to the secondary clarifiers (for the 5-stage BNR alternative), and
3. Influent stream to the tertiary filters (for the 5-stage BNR alternative).
Because alum is not critical to consistently meeting effluent limits, only seven days of alum
chemical storage are suggested for the upgraded East WRF. Preliminary calculations revealed
that 2,500 gallons of 48 percent alum solution would be sufficient to meet this storage, and a
holding pad capable of storing 10 IBC containers with an associated chemical metering station
are suggested. However, because of the infrequent use of alum during typical operations, East
WRF staff could simply store 3 IBC containers on-site and request additional alum deliveries on
an as-needed basis.
Table 25 details the conceptual design criteria for the proposed alum storage and feed facility.
Table 25 Alum System Design Criteria
Parameter Unit Quantity
Concentration % 48
Required Storage gal 2,500
Number of IBC Totes(1) # 10
Number of Alum Pumps # 2
Feed Pump Capacity (each) gph 15
Notes:
(1) IBC totes have a storage capacity of 1,000L.
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3.5.2.3 Sodium Hypochlorite
Bulk sodium hypochlorite, also known as bleach, is an effective disinfectant that has been widely
used for years in the wastewater treatment industry, including at East WRF and numerous other
local plants. Bulk sodium hypochlorite is considered hazardous and is commonly delivered as a
12.5 percent available chlorine solution. The associated chemical system has simple components
— mainly bulk chemical storage tanks and chemical metering pumps — and the feed process is
relatively easy to operate and maintain. Although the storage and feed systems are inexpensive
to construct, the chemical costs associated with bulk deliveries are relatively higher than those of
other chlorination processes such as generating sodium hypochlorite on-site.
Sodium hypochlorite solutions degrade rapidly under elevated temperature and exposure to
sunlight, both of which reduce the concentration of effective chlorine content. Therefore,
storage tanks are commonly installed under canopies or in buildings to protect against
ultraviolet light and temperature degradation. This chemical also has operational challenges
such as the potential for air binding (due to off-gassing), plugging, and mechanical malfunctions.
As discussed in Section 3.5.1.3, sodium hypochlorite is also used for maintenance and recovery
cleans for MBR systems and required doses may vary for each cleaning type depending on the
membrane supplier. The required sodium hypochlorite bulk storage facilities were detailed in
Section 3.3.2.4 and Section 3.4.3.2 for 5-stage BNR and MBR alternatives, respectively.
3.5.3 Reclaimed Water Storage and Reject Storage
Design criteria for effluent storage is based on F.A.C. Chapters 62-600 Domestic Wastewater
Facilities and 62-610 Reuse of Reclaimed Water and Land Application. These regulations require
storage facilities with sufficient capacity to ensure the retention of reclaimed water under
adverse weather conditions. At a minimum, system storage capacity shall be equal in volume to
three times the AADF (i.e., 6.3-MG of wet weather storage shall be provided). Regulations also
require reject storage with sufficient capacity to ensure the retention of reclaimed water of
unacceptable quality equal to one day’s flow at AADF conditions (i.e., 2.1-MG of reject storage
shall be provided).
The facility currently has one 3-MG GST and one 5.61-MG combined wet weather and reject
storage pond to store treated effluent – it should be noted that 2-MG of this 5.61-MG capacity is
dedicated to reject storage. For the upgraded East WRF, an additional 0.1-MG of the existing
storage pond will need to be dedicated to reject storage to meet the minimum requirement.
Neglecting this dedicated reject volume, the existing wet weather storage (6.51-MG) exceeds
the minimum wet weather storage requirements. Aside from the dedicated on-site GST and wet
weather/reject storage pond, the City’s reuse system has two additional GSTs, which have
shared access with the City’s West WRF. These are the Oak Forest (3-MG) and Lake Jesup
(0.25-MG) storage and re-pumping facilities.
Although the existing storage facilities at East WRF meet the minimum requirements listed
above, a second 3-MG GST is suggested to provide the City with increased flexibility and storage
to meet their reclaimed water demand. This additional storage will provide additional benefit by
alleviating the need to store AWT-quality effluent in the combined storage pond.
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3.5.4 Solids Handling
Although the East WRF solids handling design was outside the scope of this Project, a general
recommendation for WAS storage and treatment is provided here. The East WRF historically
stored solids for thickening in an aerated SHT and was subsequently dewatered using a mobile
belt filter press before being hauled offsite by a contractor for ultimate disposal. It is assumed
that the new WRF will continue this operation and as discussed in Section 1.4.1 Condition
Assessment, that one of the existing circular structures (most likely Digester No. 3) will be
temporarily rehabilitated to serve as an interim aerated SHT until a permanent solids handling
facility is installed at East WRF.
The level of biosolids treatment provided is dependent on the nature of final disposal or
beneficial reuse (i.e., landfilling, incineration, or land application). For example, treating to
Class B will allow the City to land-apply biosolids at select sites across the State of Florida,
providing greater flexibility with ultimate solids disposal in comparison to conventional
incineration or landfilling. To achieve Class B, it is proposed that 15-days of solids storage be
provided. For the 5-stage BNR alternative, with an assumed solids content of 2 percent TS after
thickening, conceptual evaluations estimated that 15-days of storage equates to roughly
0.28-MG. While Digester No. 3 provides only 0.18 MG, or 9.5 days of storage, it can be used
temporarily utilized and provide the City with some time to determine a long-term plan for the
East WRF’s solids handling. It is not recommended to permanently use Digester No. 3 for sludge
holding. The exact SHT and dewatering system design will be determined during the further
design stages. Table 26 outlines the conceptual design criteria for solids handling at the East
WRF.
Table 26 Solids Handling Design Criteria
Parameter Units Value
Design Plant Influent Flow, AADF mgd 2.1
WAS Flow Rate(1) gpd 64,800
Design Solids Content Post-Thickening % 2
Dewatering Type - Belt Filter Press
Sludge Holding Tanks
Number of Tanks # 1 (rehab existing)
Type - Circular Steel
Volume gal 323,000
Days of Storage Provided days 17.2
Notes:
(1) WAS rate assumed to be diverted from the clarifier underflow for the 5-stage BNR alternative, at an assumed TS of
0.58%.
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3.5.5 Potential Industrial Load Influences
Future City development may introduce industrial loads to the East WRF’s influent stream
(e.g., the incorporation of a FOG-processing facility). It is recommended that the City
contractually require the processing facility to pre-treat their effluent to industrial standards.
This industrial pre-treatment facility would be subject to inspection by the City. Additionally, the
third-party should be required to pay a monthly fee to the City to account for the influent flows
they are adding at the East WRF. In theory, they would “rent” a percentage of capacity at the
WRF to account for the monthly operating/processing fee placed on the City for the additional
load placed on the plant.
3.6 Conceptual Level Cost Estimates (“Buildout” Scenario)
High-level conceptual costs have been developed for the top two shortlisted treatment
alternatives at the “buildout” scenario: 2.1 mgd with AWT. A proposed conceptual cost estimate
for the final conceptual design recommendation is included in Section 4 of this report.
3.6.1 Cost Estimating Accuracy
The level of accuracy for cost estimates depends on the level of detail to which the project is
defined. Planning level cost estimates usually represent a Class 4 or Class 5 level of accuracy,
while final plans and specifications present the highest level of accuracy (i.e., Class 1 estimates).
The Association for the Advancement of Cost Engineering (AACE) International guidelines for
anticipated cost estimate accuracy, based on type of cost estimated are provided in Table 27. For
this conceptual cost estimate, Class 5 accuracies were used to determine the cost estimates
provided in the following subsections.
Table 27 AACE International Guidelines for Cost Estimating Accuracy
Type of Cost Estimate Anticipated Accuracy
Class 5 (Conceptual) +100% to -50%
Class 4 (Planning Level) +50% to -30%
Class 3 (Preliminary Design) +30% to -15%
Class 2 (50 to 70% Design Completion) +20% to -10%
Class 1 (Pre-Bid) +15% to -5%
3.6.2 No Action Alternative
In addition to cost comparisons for the two shortlisted treatment alternatives, analysis of a
“no action” alternative is also included herein. Under this alternative, the City would take no
action to address rehabilitation or replacement of the existing East WRF. This alternative would
prevent modernization of the facility, and ultimately force the City to continue to operate and
maintain a facility that is outdated. Because a majority of the East WRF’s assets have met the
end of their useful life, they prove more costly to operate and maintain. Ultimately, under this
alternative, the facility would continue to operate as-is until one single asset (or multiple assets)
becomes the point of failure. This would further put the City at risk in its ability to meet
environmental and regulatory requirements, and will ultimately lead to the facilities failure to
perform and treat wastewater.
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The “no action” alternative also prevents modernization of the facility to meet AWT standards in
the future. If this alternative were selected, the City would only delay their need to upgrade the
facility to meet future environmental regulations. This alternative is consequently uneconomical
and unviable and was rejected.
3.6.3 BNR and MBR Capital Conceptual Cost Estimates
The conceptual capital cost estimates for the 5-stage BNR and MBR alternatives at “buildout”
are approximately $48,082,000 and $53,922,000, respectively. These detailed costs were
developed for the buildout scenario of 2.1 mgd with AWT and are included in Table 28 and
Table 29. The MBR alternative proved slightly more costly than the BNR (as the MBR alternative
requires additional fine screening, flow equalization, increased chemical storage, etc.). The
estimated conceptual costs were obtained from a combination of recent bid tabs and schedules
of values for similarly sized facilities in Central Florida, as well as recent equipment costs
obtained from local vendors. All costs have been escalated to 2022 dollars and have a 20 percent
contingency applied due to the conceptual-level of design. This contingency factor will be
reduced within the subsequent project stages as the proposed facility design is further refined.
However, it should be noted that current market conditions pose a challenge in cost-estimating
as prices continue to escalate. The City should closely track economic conditions and prices
during the final design phase to confirm market conditions and cost estimates.
3.6.4 Annual O&M Conceptual Cost Estimates
Annual operations & maintenance (O&M) conceptual costs have been developed for the
two alternatives at 2.1 mgd with AWT and are included in Table 30. These O&M costs were
evaluated for three main categories: power, chemical costs, and maintenance requirements.
Power requirements were determined by identifying all key process mechanical equipment for
each alternative and applying a power utilization factor based on the estimated frequency of use.
Chemical costs were developed by comparing the significant differences in chemical
requirements between the two alternatives and applying current chemical costs to those
volumes. Maintenance costs were developed by assuming 3 percent of the capital cost assets
would be maintained each year. The comparison table shows that the MBR alternative is more
costly to operate and maintain, costing approximately $150,000 more than the 5-stage BNR
alternative on an annual basis. All conceptual costs are shown in 2022 dollars.
409
1 Pretreatment 1 LS -- $ 3,200,000
2 Secondary Treatment 1 LS -- $ 12,970,000
3 Tertiary Treatment 1 LS -- $ 2,100,000
4 Pumping & Chemical Systems 1 LS -- $ 1,935,000
5 Facilities / Buildings 1 LS -- $ 1,729,000
$ 21,934,000
6 15% $ 3,291,000
7 25% $ 5,484,000
$ 30,709,000
8 10% $ 3,071,000
9 7% $ 2,150,000
10 6.5% $ 999,000
$ 36,929,000
11 20% $ 7,386,000
$ 44,315,000
12 8.5% $ 3,767,000
$ 48,082,000 ENGINEER'S OPINION OF PROBABLE PROJECT COST
Contractor's General Conditions
Contractor Fees, Overhead/Profit, and Risk
Sales Tax (% cost of equipment)
Subtotal C (items 1-10)
Project Contingency
Subtotal D (items 1-11)
Subtotal A (Items 1-5)
Site/Civil Development (Excavation, Dewatering, Site Preparation,
Paving/Grading, Stormwater Management, Yard Piping)
Electrical, Instrumentation and Controls
General Administration, Legal, Engineering Fee
Subtotal B (items 1-7)
City of Winter Springs
East WRF 5-Stage BNR Alternative (2.1 MGD with AWT - Buildout Scenario)
Conceptual Capital Cost
ITEM NO. ITEM DESCRIPTION
EST'D.
QTY.UNIT % of
Subtotal TOTAL PRICE
Table 28
410
1 Pretreatment 1 LS -- 6,108,000$
2 Secondary Treatment 1 LS -- $ 13,106,000
3 Tertiary Treatment 1 LS -- 600,000$
4 Pumping & Chemical Systems 1 LS -- 2,008,000$
5 Facilities / Buildings 1 LS -- 1,929,000$
$ 23,751,000
6 15% $ 3,563,000
7 30% $ 7,126,000
$ 34,440,000
8 10% $ 3,444,000
9 7% $ 2,411,000
10 6.5% $ 1,120,000
$ 41,415,000
11 20% $ 8,283,000
$ 49,698,000
12 8.50% $ 4,224,000
$ 53,922,000
TOTAL PRICE
General Administration, Legal, Engineering Fee
ENGINEER'S OPINION OF PROBABLE PROJECT COST
Contractor Fees, Overhead/Profit, and Risk
Sales Tax (% cost of equipment)
Project Contingency
Subtotal D (items 1-11)
Subtotal B (items 1-7)
City of Winter Springs
East WRF MBR Alternative (2.1 MGD with AWT - Buildout Scenario)
Conceptual Capital Cost
Subtotal C (items 1-10)
Subtotal A (Items 1-5)
Site/Civil Development (Excavation, Dewatering, Site Preparation,
Paving/Grading, Stormwater Management, Yard Piping)
Electrical, Instrumentation and Controls
Contractor's General Conditions
ITEM NO. ITEM DESCRIPTION
EST'D.
QTY.UNIT % of
Subtotal
Table 29
411
Item No. Item Description 5-Stage BNR ($/year) MBR ($/year)
1 Pretreatment 19,000$ 28,000$
2 Process Basins 164,000$ 193,000$
3 Clarifiers 14,000$ -$
4 Filters 1,000$ -$
5 Membrane Tanks -$ 44,000$
6 Chlorine Contact and Effluent Transfer 37,000$ 37,000$
7 Reclaimed Water Pump Station 104,000$ 104,000$
8 Sodium Hypochlorite - MBR Cleaning -$ 4,000$
9 Citric Acid - MBR Cleaning -$ 31,000$
10 Annual R&R 1,053,000$ 1,101,000$
1,392,000$ 1,542,000$
Chemical Requirements
Maintenance Requirements
Annual O&M Conceptual Cost Comparison
East WRF
City of Winter Springs
Power Requirements
Grand Total ($)
Table 30
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4.0 Final Recommendation
Based on the City’s applied values established by their selection committee, 5-stage BNR and
MBR were the top two scoring treatment technologies. A final treatment alternative
recommendation is proposed below based on the process design, site layouts, and life-cycle cost
outlined in Section 3. This recommendation is intended to support the City in making the
informed decision of which AWT-capable process to select for the upgraded East WRF.
4.1 Recommended Alternative
Both BNR and MBR are established technologies in the United States, with a track record of
successfully meeting stringent nutrient discharge limits. However, 5-stage BNR is known as the
“Gold Standard” of CAS technologies and is more highly implemented in Florida, creating a
large, local resource pool for operators to turn to when in-need of support. Additionally, the
5-stage BNR process is similar to current operations and does not require a high degree of
additional operator training. On the other hand, while MBR has a smaller footprint in comparison
to the 5-stage BNR, it requires a higher pumping/energy and chemical use, and more mechanical
equipment, which ultimately creates more required maintenance. Additionally, MBR technology
is dissimilar to the current treatment process at the East WRF, which requires a shift in operation
strategies and can potentially pose challenges for operations staff. Based on both these
non-economic factors, as well as the conceptual capital cost estimates outlined in Section 3,
Carollo recommends that the City select the 5-stage BNR alternative as the proposed treatment
process for the East WRF.
4.2 Recommended Plant Capacity and Treatment Standard
As discussed in Section 1.4.2, limited growth is expected within the City of Winter Springs over
the next 20 years. Results from the population analysis indicated that 2045 flows may range
anywhere from 1.04 to 1.43 mgd AADF. Additionally, the “City of Winter Springs 2022
Wastewater and Reclaimed Water Master Plan” prepared by Kimley-Horn projects that
population growth within available parcels and potential septic to sewer conversions may result
in flows up to 1.49 mgd over the next 20 years. Both projections are far less than the current
permitted capacity of 2.012 mgd.
Rather than designing, constructing, and paying for an oversized facility today, and
consequently having to operate and maintain the oversized facility, Carollo recommends that
the City “build for today but plan for tomorrow” (i.e., right-size the WRF for near-term growth).
To elaborate, since flows are not expected to surpass 1.49 mgd AADF in the next 20 years,
Carollo recommends that the proposed East WRF be designed for a capacity 1.5 mgd AADF,
while also allocating space onsite such that the capacity can be readily expanded to meet future
needs. Additionally, because AWT is not required today, it is recommended to phase the
construction process to ensure current treatment standards are being met but allow AWT
build-out to meet future requirements.
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EAST WRF CONCEPTUAL DESIGN REPORT | CITY OF WINTER SPRINGS
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This initial proposed BNR facility would be constructed with only one screen and grit removal
unit online, while still accounting for additional space for the future units when increased
capacity is required. Additionally, only three total BNR trains and two secondary clarifiers would
be constructed but again, leaving the footprint and basic infrastructure in-place to allow for the
future buildout of 2.1 mgd AADF. As wastewater flows increase over the years, the City could
then install the remaining BNR train and clarifier as needed to provide the required capacity. A
similar approach can be used for the tertiary filtration system, where the three disk filter units
could be initially constructed with four disks per filter and as flows increase the additional disks
could be installed in the existing filter units.
Construction could also be phased from an effluent quality perspective (i.e., to achieve AWT).
For example, if the East WRF’s current effluent requirements are still in place, then the BNR
system could be initially constructed with anoxic and aeration basins in a configuration referred
to as the Modified Ludzack-Ettinger (MLE) process, while also allocating footprint for future
basins. An anaerobic basin could also be constructed initially to promote settling in the
secondary clarifiers (improving overall treatment) but would not be required to meet current
effluent requirements. When AWT is then required in the future as part of new regulations, the
remaining post-anoxic and reaeration basins could be constructed.
4.3 Recommended Conceptual Site Layout and Cost Estimate
A proposed conceptual site layout for this 1.5 mgd scenario (meeting today’s treatment
standards) is included in Figure 20. It is recommended that the City initially construct a facility
based of the conceptual design shown in Figure 20, but modify as needed to meet future
quantity and quality needs. A full buildout of this 5-stage BNR facility to meet a capacity of
2.1 mgd and produce AWT-quality effluent, was shown previously in Figure 17.
Additionally, a revised cost estimate for the 1.5 mgd scenario is provided in Table 31. The
conceptual capital cost estimate for the recommended 1.5 mgd East WRF is approximately
$34,792,000. By right sizing the East WRF for today’s needs, the City would save approximately
$13 million dollars, today, on capital costs, with additional savings on annual O&M costs. The
City would also have the flexibility, reliability, and redundancy to take basins offline, while still
operating efficiently and meeting effluent requirements.
414
FIGURE 2SITE LAYOUT1.5 MGD BNREAST WRF®SCALE80'40'0Aerial Photography Source: FDOT APLUS March, 2019NOTES:LEGEND:1.5 MGD AADFWWTP No. 2OPERATIONSBUILDINGBLOWERROOMELECTRICALROOMGENERATORROOMWWTP No. 1NEWCLARIFIERNo.1NEW BLOWER BUILDING/ELECTRICAL BUILDING #1CHLORINE CONTACT BASINREJECT PUMP STATIONTRANSFER PUMP STATIONDIGESTERNo. 3PLANTENTRANCEGATE5.61 MGREJECT AND WETWEATHER LINEDSTORAGE POND3.0 MGRECLAIMED WATERSTORAGE TANKELECTRICALBUILDINGRECLAIMED WATER DISTRIBUTIONPUMP STATIONDEMOLITION AREA(SEE NOTE 1)NEWCLARIFIERNo.2NEW RAS/WASPUMP STATIONPADNEW MLSSSPLITTER BOXNEW DISK FILTERSNEW REJECT RETURN/BACKWASH RETURN AND IN-PLANTRECYCLE PUMP STATIONSODIUM HYPOCHLORITESTORAGE AND PUMPINGNEW CHLORINE CONTACT BASINNEW TRANSFERPUMP STATION1.5 MGBNRTRAIN
N
o
.
1
TRAIN
N
o
.
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TRAIN
N
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.
3 NEW HEADWORKS INCLUDINGSCREENING AND GRIT REMOVALELECTRICAL BUILDING No. 2TERTIARY FILTERSNEW ODOR CONTROLFACILITYSUBMERSIBLE INTERNALRECYCLE PUMP (TYP)CONNECT TO EXISTINGCOLLECTION SYSTEM(SEE NOTE 2)CONNECT TO EXISTINGRECLAIMED WATER SYSTEM(SEE NOTE 2)1.AFTER NEW PROCESS EQUIPMENT IS IN SERVICE,STRUCTURES AND EQUIPMENT WITHIN THIS AREACAN BE DEMOLISHED AS NEEDED. THIS AREA CAN BEUSED FOR NEW OPERATION BUILDING AND PARKING,SLUDGE STORAGE AND HANDLING, ETC.2.CONCEPTUAL YARD PIPING LAYOUT SHOWS JUST THEPRIMARY FLOW PATH THROUGH THE PLANT.Figure 20415
1 Pretreatment 1 LS -- $ 2,950,000
2 Secondary Treatment 1 LS -- $ 8,146,000
3 Tertiary Treatment 1 LS -- $ 1,600,000
4 Pumping & Chemical Systems 1 LS -- $ 1,646,000
5 Facilities / Buildings 1 LS -- $ 1,529,000
$ 15,871,000
6 15% $ 2,381,000
7 25% $ 3,968,000
$ 22,220,000
8 10% $ 2,222,000
9 7% $ 1,556,000
10 6.5% $ 723,000
$ 26,721,000
11 20% $ 5,345,000
$ 32,066,000
12 8.5% $ 2,726,000
$ 34,792,000
Table 31
ENGINEER'S OPINION OF PROBABLE PROJECT COST
City of Winter Springs
East WRF 5-Stage BNR Alternative (1.5 MGD)
Conceptual Capital Cost
Contractor Fees, Overhead/Profit, and Risk
Sales Tax (% cost of equipment)
Subtotal C (items 1-10)
Project Contingency
Subtotal D (items 1-11)
General Administration, Legal, Engineering Fee
TOTAL PRICE
Subtotal A (Items 1-5)
Site/Civil Development (Excavation, Dewatering, Site Preparation,
Paving/Grading, Stormwater Management, Yard Piping)
Electrical, Instrumentation and Controls
Subtotal B (items 1-7)
% of
Subtotal
Contractor's General Conditions
ITEM
NO.ITEM DESCRIPTION EST'D.
QTY.UNIT
416
EAST WRF CONCEPTUAL DESIGN REPORT | CITY OF WINTER SPRINGS
APRIL 2022 | 70
4.4 Funding Considerations
4.4.1 SRF Funding
The Clean Water State Revolving Fund (CWSRF) Program provides low-interest loans to local
governments to plan, design, and build or upgrade wastewater, stormwater, and nonpoint
source pollution prevention projects. This CDR, as well as the “City of Winter Springs 2022
Wastewater and Reclaimed Water Master Plan” prepared by Kimley-Horn, were prepared with
the intent to meet a majority of the requirements of the FDEP’s CWSRF program for the funding
of the proposed East WRF. Should the City desire to pursue funding for design and/or
construction of the proposed East WRF, they may apply for a Request for Inclusion (RFI), using
this document as an appendix. A copy of the CWSRF Planning Document Requirements
Checklist is included in Appendix E.
The City should also monitor other potential funding sources which may arise from recent and
upcoming federal and state programs.
417
EAST WRF CONCEPTUAL DESIGN REPORT | CITY OF WINTER SPRINGS
APRIL 2022
Appendix A
EXISTING WRF PFD
418
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Attachment No. 2
PROCESS FLOW DIAGRAM
CITY OF WINTER SPRINGS EAST WRF
419
EAST WRF CONCEPTUAL DESIGN REPORT | CITY OF WINTER SPRINGS
APRIL 2022
Appendix B
EAST WRF SURVEY
420
489 STATE ROAD 436 | SUITE 117 | CASSELBERRY, FL | 32707PHONE 407.681.3836 | FAX 407.681.6541WWW.LSSURVEYOR.COM | INFO@LSSURVEYOR.COMPROFESSIONAL SURVEYOR & MAPPER BUSINESS LICENSE | LB#7829DiversifiedL & SProfessional Surveyors and MappersWINTER SPRINGS EAST PLANTBOUNDARY ANDTOPOGRAPHIC SURVEYCAROLLOLOCATED INSECTION 08, TOWNSHIP 21 SOUTH, RANGE 31 EASTCITY OF WINTER SPRINGSSEMINOLE COUNTY, FLORIDADESCRIPTIONBYDATEREVISIONSNo.BRAD ALEXANDER, PSM - LS# 6885THIS SURVEY MAP AND/OR REPORT IS NOT VALID WITHOUT THESIGNATURE AND THE ORIGINAL RAISED SEAL OF THE ABOVE.SURVEY BYDRAWING No.SHEETOF7PROJECT No.N.WILKE210120SURVEY DATE 2021.OCT.08DRAWN BY C.HENNDRAWN DATEREVIEWED BY B.ALEXANDERAPPROVED BY S.MANOR2021.OCT.15SURVEYOR'S CERTIFICATIONI HEREBY CERTIFY THAT THIS SURVEY REPRESENTED HEREON IS TRUE AND CORRECT TO THE BEST OF MY KNOWLEDGE,INFORMATION, AND BELIEF. IT HAS BEEN PREPARED IN ACCORDANCE WITH THE STANDARDS SET FORTH IN CHAPTER 5J-17OF THE FLORIDA ADMINISTRATIVE CODE PURSUANT TO TO CHAPTERS 177 AND 472 OF THE FLORIDA STATUES.V1001V203V205V202V204V201421
489 STATE ROAD 436 | SUITE 117 | CASSELBERRY, FL | 32707PHONE 407.681.3836 | FAX 407.681.6541WWW.LSSURVEYOR.COM | INFO@LSSURVEYOR.COMPROFESSIONAL SURVEYOR & MAPPER BUSINESS LICENSE | LB#7829DiversifiedL & SProfessional Surveyors and MappersWINTER SPRINGS EAST PLANTBOUNDARY ANDTOPOGRAPHIC SURVEYCAROLLOLOCATED INSECTION 08, TOWNSHIP 21 SOUTH, RANGE 31 EASTCITY OF WINTER SPRINGSSEMINOLE COUNTY, FLORIDADESCRIPTIONBYDATEREVISIONSNo.BRAD ALEXANDER, PSM - LS# 6885THIS SURVEY MAP AND/OR REPORT IS NOT VALID WITHOUT THESIGNATURE AND THE ORIGINAL RAISED SEAL OF THE ABOVE.SURVEY BYDRAWING No.SHEETOF7PROJECT No.N.WILKE210120SURVEY DATE 2021.OCT.08DRAWN BY C.HENNDRAWN DATEREVIEWED BY B.ALEXANDERAPPROVED BY S.MANOR2021.OCT.15SURVEYOR'S CERTIFICATIONI HEREBY CERTIFY THAT THIS SURVEY REPRESENTED HEREON IS TRUE AND CORRECT TO THE BEST OF MY KNOWLEDGE,INFORMATION, AND BELIEF. IT HAS BEEN PREPARED IN ACCORDANCE WITH THE STANDARDS SET FORTH IN CHAPTER 5J-17OF THE FLORIDA ADMINISTRATIVE CODE PURSUANT TO TO CHAPTERS 177 AND 472 OF THE FLORIDA STATUES.V20020GRAPHIC SCALE200'100'50'100'1 INCH = 100 FEET422
489 STATE ROAD 436 | SUITE 117 | CASSELBERRY, FL | 32707PHONE 407.681.3836 | FAX 407.681.6541WWW.LSSURVEYOR.COM | INFO@LSSURVEYOR.COMPROFESSIONAL SURVEYOR & MAPPER BUSINESS LICENSE | LB#7829DiversifiedL & SProfessional Surveyors and MappersWINTER SPRINGS EAST PLANTBOUNDARY ANDTOPOGRAPHIC SURVEYCAROLLOLOCATED INSECTION 08, TOWNSHIP 21 SOUTH, RANGE 31 EASTCITY OF WINTER SPRINGSSEMINOLE COUNTY, FLORIDADESCRIPTIONBYDATEREVISIONSNo.BRAD ALEXANDER, PSM - LS# 6885THIS SURVEY MAP AND/OR REPORT IS NOT VALID WITHOUT THESIGNATURE AND THE ORIGINAL RAISED SEAL OF THE ABOVE.SURVEY BYDRAWING No.SHEETOF7PROJECT No.N.WILKE210120SURVEY DATE 2021.OCT.08DRAWN BY C.HENNDRAWN DATEREVIEWED BY B.ALEXANDERAPPROVED BY S.MANOR2021.OCT.15SURVEYOR'S CERTIFICATIONI HEREBY CERTIFY THAT THIS SURVEY REPRESENTED HEREON IS TRUE AND CORRECT TO THE BEST OF MY KNOWLEDGE,INFORMATION, AND BELIEF. IT HAS BEEN PREPARED IN ACCORDANCE WITH THE STANDARDS SET FORTH IN CHAPTER 5J-17OF THE FLORIDA ADMINISTRATIVE CODE PURSUANT TO TO CHAPTERS 177 AND 472 OF THE FLORIDA STATUES.V2013MATCHLINE: A-A SEE SHEET V202MATCHLINE: C-C SEE SHEET V2040GRAPHIC SCALE40'20'10'20'1 INCH = 20 FEET423
489 STATE ROAD 436 | SUITE 117 | CASSELBERRY, FL | 32707PHONE 407.681.3836 | FAX 407.681.6541WWW.LSSURVEYOR.COM | INFO@LSSURVEYOR.COMPROFESSIONAL SURVEYOR & MAPPER BUSINESS LICENSE | LB#7829DiversifiedL & SProfessional Surveyors and MappersWINTER SPRINGS EAST PLANTBOUNDARY ANDTOPOGRAPHIC SURVEYCAROLLOLOCATED INSECTION 08, TOWNSHIP 21 SOUTH, RANGE 31 EASTCITY OF WINTER SPRINGSSEMINOLE COUNTY, FLORIDADESCRIPTIONBYDATEREVISIONSNo.BRAD ALEXANDER, PSM - LS# 6885THIS SURVEY MAP AND/OR REPORT IS NOT VALID WITHOUT THESIGNATURE AND THE ORIGINAL RAISED SEAL OF THE ABOVE.SURVEY BYDRAWING No.SHEETOF7PROJECT No.N.WILKE210120SURVEY DATE 2021.OCT.08DRAWN BY C.HENNDRAWN DATEREVIEWED BY B.ALEXANDERAPPROVED BY S.MANOR2021.OCT.15SURVEYOR'S CERTIFICATIONI HEREBY CERTIFY THAT THIS SURVEY REPRESENTED HEREON IS TRUE AND CORRECT TO THE BEST OF MY KNOWLEDGE,INFORMATION, AND BELIEF. IT HAS BEEN PREPARED IN ACCORDANCE WITH THE STANDARDS SET FORTH IN CHAPTER 5J-17OF THE FLORIDA ADMINISTRATIVE CODE PURSUANT TO TO CHAPTERS 177 AND 472 OF THE FLORIDA STATUES.V2024MATCHLINE: B-B SEE SHEET V203MATCHLINE: C-C SEE SHEET V204MATCHLINE: A-A SEE SHEET V201MATCHLINE: C-C SEE SHEET V2040GRAPHIC SCALE40'20'10'20'1 INCH = 20 FEET424
489 STATE ROAD 436 | SUITE 117 | CASSELBERRY, FL | 32707PHONE 407.681.3836 | FAX 407.681.6541WWW.LSSURVEYOR.COM | INFO@LSSURVEYOR.COMPROFESSIONAL SURVEYOR & MAPPER BUSINESS LICENSE | LB#7829DiversifiedL & SProfessional Surveyors and MappersWINTER SPRINGS EAST PLANTBOUNDARY ANDTOPOGRAPHIC SURVEYCAROLLOLOCATED INSECTION 08, TOWNSHIP 21 SOUTH, RANGE 31 EASTCITY OF WINTER SPRINGSSEMINOLE COUNTY, FLORIDADESCRIPTIONBYDATEREVISIONSNo.BRAD ALEXANDER, PSM - LS# 6885THIS SURVEY MAP AND/OR REPORT IS NOT VALID WITHOUT THESIGNATURE AND THE ORIGINAL RAISED SEAL OF THE ABOVE.SURVEY BYDRAWING No.SHEETOF7PROJECT No.N.WILKE210120SURVEY DATE 2021.OCT.08DRAWN BY C.HENNDRAWN DATEREVIEWED BY B.ALEXANDERAPPROVED BY S.MANOR2021.OCT.15SURVEYOR'S CERTIFICATIONI HEREBY CERTIFY THAT THIS SURVEY REPRESENTED HEREON IS TRUE AND CORRECT TO THE BEST OF MY KNOWLEDGE,INFORMATION, AND BELIEF. IT HAS BEEN PREPARED IN ACCORDANCE WITH THE STANDARDS SET FORTH IN CHAPTER 5J-17OF THE FLORIDA ADMINISTRATIVE CODE PURSUANT TO TO CHAPTERS 177 AND 472 OF THE FLORIDA STATUES.V20350GRAPHIC SCALE40'20'10'20'1 INCH = 20 FEETMATCHLINE: B-B SEE SHEET V203MATCHLINE: D-D SEE SHEET V205MATCHLINE: D-D SEE SHEET V205
425
489 STATE ROAD 436 | SUITE 117 | CASSELBERRY, FL | 32707PHONE 407.681.3836 | FAX 407.681.6541WWW.LSSURVEYOR.COM | INFO@LSSURVEYOR.COMPROFESSIONAL SURVEYOR & MAPPER BUSINESS LICENSE | LB#7829DiversifiedL & SProfessional Surveyors and MappersWINTER SPRINGS EAST PLANTBOUNDARY ANDTOPOGRAPHIC SURVEYCAROLLOLOCATED INSECTION 08, TOWNSHIP 21 SOUTH, RANGE 31 EASTCITY OF WINTER SPRINGSSEMINOLE COUNTY, FLORIDADESCRIPTIONBYDATEREVISIONSNo.BRAD ALEXANDER, PSM - LS# 6885THIS SURVEY MAP AND/OR REPORT IS NOT VALID WITHOUT THESIGNATURE AND THE ORIGINAL RAISED SEAL OF THE ABOVE.SURVEY BYDRAWING No.SHEETOF7PROJECT No.N.WILKE210120SURVEY DATE 2021.OCT.08DRAWN BY C.HENNDRAWN DATEREVIEWED BY B.ALEXANDERAPPROVED BY S.MANOR2021.OCT.15SURVEYOR'S CERTIFICATIONI HEREBY CERTIFY THAT THIS SURVEY REPRESENTED HEREON IS TRUE AND CORRECT TO THE BEST OF MY KNOWLEDGE,INFORMATION, AND BELIEF. IT HAS BEEN PREPARED IN ACCORDANCE WITH THE STANDARDS SET FORTH IN CHAPTER 5J-17OF THE FLORIDA ADMINISTRATIVE CODE PURSUANT TO TO CHAPTERS 177 AND 472 OF THE FLORIDA STATUES.V2046MATCHLINE: E-E SEE SHEET V205MATCHLINE: C-C SEE SHEET V202MATCHLINE: C-C SEE SHEET V2010GRAPHIC SCALE40'20'10'20'1 INCH = 20 FEET426
489 STATE ROAD 436 | SUITE 117 | CASSELBERRY, FL | 32707PHONE 407.681.3836 | FAX 407.681.6541WWW.LSSURVEYOR.COM | INFO@LSSURVEYOR.COMPROFESSIONAL SURVEYOR & MAPPER BUSINESS LICENSE | LB#7829DiversifiedL & SProfessional Surveyors and MappersWINTER SPRINGS EAST PLANTBOUNDARY ANDTOPOGRAPHIC SURVEYCAROLLOLOCATED INSECTION 08, TOWNSHIP 21 SOUTH, RANGE 31 EASTCITY OF WINTER SPRINGSSEMINOLE COUNTY, FLORIDADESCRIPTIONBYDATEREVISIONSNo.BRAD ALEXANDER, PSM - LS# 6885THIS SURVEY MAP AND/OR REPORT IS NOT VALID WITHOUT THESIGNATURE AND THE ORIGINAL RAISED SEAL OF THE ABOVE.SURVEY BYDRAWING No.SHEETOF7PROJECT No.N.WILKE210120SURVEY DATE 2021.OCT.08DRAWN BY C.HENNDRAWN DATEREVIEWED BY B.ALEXANDERAPPROVED BY S.MANOR2021.OCT.15SURVEYOR'S CERTIFICATIONI HEREBY CERTIFY THAT THIS SURVEY REPRESENTED HEREON IS TRUE AND CORRECT TO THE BEST OF MY KNOWLEDGE,INFORMATION, AND BELIEF. IT HAS BEEN PREPARED IN ACCORDANCE WITH THE STANDARDS SET FORTH IN CHAPTER 5J-17OF THE FLORIDA ADMINISTRATIVE CODE PURSUANT TO TO CHAPTERS 177 AND 472 OF THE FLORIDA STATUES.V2057MATCHLINE: E-E SEE SHEET V204 MATCHLINE: D-D SEE SHEET V203MATCHLINE: D-D SEE SHEET V2030GRAPHIC SCALE40'20'10'20'1 INCH = 20 FEET427
EAST WRF CONCEPTUAL DESIGN REPORT | CITY OF WINTER SPRINGS
APRIL 2022
Appendix C
ECOLOGICAL ASSESSMENT AND FNAI
TRACKING LIST
428
5401 South Kirkman Road
Suite 475
Orlando, FL 32819
407.403.6300 phone
407.403.6301 fax
esassoc.com
September 2, 2021
Meera A. Joshi, E.I.
Carollo Engineers, Inc.
200 E. Robinson Street, Suite #1400
Orlando, FL 32801
Subject: City of Winter Springs East Water Reclamation Facility
General Environmental Constraints Review
On August 10, 2021, Environmental Science Associates (ESA) completed a general Environmental Constraints
Review for Carollo Engineers (Carollo), for the City of Winter Springs East Facility Conceptual Design Report
(Project) in Seminole County, Florida. The Area of review for the Project was identified by Carollo (Exhibit 1A).
Both wetlands and listed species habitat were assessed within the area of review, described below.
Field Assessment
ESA field biologist completed a wetland delineation utilizing a sub-foot Trimble GPS unit, within the review area
as depicted on Exhibit 1A. The remaining wetland features within the parcel boundary were aerial interpreted and
the approximate limits were confirmed during the site review. The delineated forested wetland system within the
review area is extensive and contains the following vegetative species: laurel oak (Quercus laurifolia), sweetgum
(Liquidambar styraciflua), red maple (Acer rubrum), swamp bay (Persea palustris), American elm (Ulmus
americana), cabbage palm (Sabal palmetto), musclewood (Carpinus caroliniana), dogwood (Cornus foemina),
shield fern (Thelypteris kunthii), and Virginia chain fern (Woodwardia virginica). Vegetation observed is indicative
of a typical hydric hammock community type. The wetland system is jurisdictional to both the state and federal
agencies. Therefore, under the new state regulations (December 2020) the federal 404 permitting was delegated to
the Florida Department of Environmental Protection (FDEP) for waters not retained by the United States Core of
Engineers (USACOE). Under the new state guidelines, the FDEP will be the coordinating agency for both the state
and federal 404 permitting process. Overall, the wetland feature is anticipated to be assessed as a medium quality
system and appears to support an appropriate hydroperiod.
The wetland system is located within the Lake Jesup Drainage Basin, which is considered impacted by the
permitting agencies. In addition, there are no mitigation banks located within the basin to address potential Project
impacts to the wetland system. Therefore, there are a couple of options provided below that may be available to
offset unavoidable impacts to the wetland system.
1. Utilization of an approved mitigation site within the Lake Jesup Basin. There is one agency approved
mitigation site that has limited forested credits available at this time. Based on the current pricing index
for this site, credits start at $400,000.00.
2. Construction of a wetland mitigation site within the Lake Jesup Basin, either utilizing land owned or
purchased by the City of Winter Springs. It is important to note that land utilized for this purpose should
not be encumbered by conservation or other restrictions.
429
September 2, 2021
Page 2
3. Investigations with FDEP to utilize an out-of-basin Mitigation Bank (but within the same watershed – St
Johns River Watershed) with a Cumulative Impact Analysis. At this time, there has been NO approved
Cumulative Impact Analysis provided for any of the out-of-basin mitigation banks within the watershed.
A review of state and federally listed species habitat was also provided within the facility property boundary. Bald
eagle (Haliaeetus leucocephalus) nests were not identified within or near the subject parcel. Although no gopher
tortoise (Gopherus polyphemus) burrows were observed during the site assessment, a Florida Fish and wildlife
Conservation Commission (FWC) approved 100-percent burrow survey should be performed within the upland
limits of the area of review, at least 90 days from construction initiation. No other listed species habitat was
observed within the property limits.
Should you have any questions regarding the site review, please do not hesitate to contact me at 407-709-9615 or
by email at SSHAW@ESASSOC.COM.
Sincerely,
Susan Shaw
ESA Program Manager, Orlando
430
Source: Esri, HERE, DeLorme, USGS, Intermap, INCREMENT P, NRCan, 2020; Seminole County 2021, Carollo 2021, ESA, 2021Date: 9/2/2021CITY OF WINTER SPRINGS EAST AND WEST WRF CONCEPTUAL DESIGN REPORTSEXHIBIT 1A
WETLAND AND OSW FEATURES
LEGEND
Review AreaGPS LocationsDelineated Wetland/OSW LimitsWetland FeaturesOSW FeaturesEast WRF Property Boundary
U:\GIS\GIS\Projects\2021xxx\D202100879.00_City of Winter Springs Parcel Review\03_MXDs_Projects\Memo\East WWTP Wetland Features.mxd0 300
Feet
N
431
FNAI Tracking List
Seminole County, Florida
January 2022
Vertebrates
Group Scientific Name Common
Name
Global
Rank
State
Rank
Federal
Status
Stat
e
Stat
us
Fishes Ameiurus
brunneus
Snail
Bullhead G4 S4? N
Fishes Pteronotropis
welaka
Bluenose
Shiner G3G4 S3S4 ST
Amphibians Lithobates
capito
Gopher Frog G2G3 S3 N
Reptiles Alligator
mississippiensis
American
Alligator G5 S4 SAT FT(S
/A)
Reptiles Drymarchon
couperi
Eastern
Indigo Snake G3 S2? T FT
Reptiles Gopherus
polyphemus
Gopher
Tortoise G3 S3 C ST
432
Reptiles Graptemys
ernsti
Escambia
Map Turtle G2 S2 N
Reptiles Lampropeltis
floridana
Florida
Kingsnake G2 S2 N
Reptiles Pituophis
melanoleucus
Pine Snake G4 S3 ST
Birds
Antigone
canadensis
pratensis
Florida
Sandhill
Crane
G5T2 S2 ST
Birds Aphelocoma
coerulescens
Florida
Scrub-Jay G1G2 S1S2 T FT
Birds Aramus
guarauna
Limpkin G5 S3 N
Birds Buteo
brachyurus
Short-tailed
Hawk G4G5 S1 N
Birds Haliaeetus
leucocephalus
Bald Eagle G5 S3 N
Birds Mycteria
americana
Wood Stork G4 S2 T FT
Birds Pandion
haliaetus
Osprey G5 S3S4 N
Mammals Mustela frenata
peninsulae
Florida Long-
tailed
Weasel
G5T3? S3? N
433
Mammals Podomys
floridanus
Florida
Mouse G3 S3 N
Mammals Puma concolor
coryi
Florida
Panther G5T1 S1 E FE
Mammals Sciurus niger
niger
Southeastern
Fox Squirrel G5T5 S3 N
Mammals
Trichechus
manatus
latirostris
Florida
Manatee G2G3T2 S2S3 T N
Mammals Ursus americanus
floridanus
Florida Black
Bear G5T4 S4 N
Plants & Lichens
Group Scientific Name Common
Name
Global
Rank
State
Rank
Federal
Status
State
Status
Plants
and
Lichens
Calopogon
multiflorus
many-
flowered
grass-pink
G2G3 S2S3 T
Plants
and
Lichens
Campyloneurum
angustifolium
narrow-
leaved strap
fern
G4G5 S1 E
Plants
and
Lichens
Carex
chapmannii
Chapman's
sedge G3 S3 T
Plants
and
Lichens
Centrosema
arenicola
sand butterfly
pea G2Q S2 E
434
Plants
and
Lichens
Chionanthus
pygmaeus
pygmy fringe
tree G2G3 S2S3 E E
Plants
and
Lichens
Coelorachis
tuberculosa
Piedmont
jointgrass G3 S3 T
Plants
and
Lichens
Ctenitis
submarginalis
brown-hair
comb fern G5 S1 E
Plants
and
Lichens
Cucurbita
okeechobeensis
Okeechobee
gourd G1 S1 E E
Plants
and
Lichens
Dennstaedtia
bipinnata
hay scented
fern G4 S1 E
Plants
and
Lichens
Eriogonum
longifolium var.
gnaphalifolium
scrub
buckwheat G4T3 S3 T E
Plants
and
Lichens
Gymnopogon
chapmanianus
Chapman's
skeletongrass G3 S3 N
Plants
and
Lichens
Illicium
parviflorum
star anise G2 S2 E
Plants
and
Lichens
Lechea cernua
nodding
pinweed G3 S3 T
Plants
and
Lichens
Nemastylis
floridana
celestial lily G2 S2 E
435
Plants
and
Lichens
Nolina
atopocarpa
Florida
beargrass G3 S3 T
Plants
and
Lichens
Ophioglossum
palmatum
hand fern G4 S2 E
Plants
and
Lichens
Pecluma
plumula
plume
polypody G5 S2 E
Plants
and
Lichens
Pecluma ptilota
var.
bourgeauana
comb
polypody G5?TNR S2 E
Plants
and
Lichens
Pteroglossaspis
ecristata
giant orchid G2G3 S2 T
Plants
and
Lichens
Pycnanthemum
floridanum
Florida
mountain-
mint
G3 S3 T
Plants
and
Lichens
Rhipsalis
baccifera
mistletoe
cactus G4 S1 E
Plants
and
Lichens
Salix floridana
Florida willow G2G3 S2S3 E
Plants
and
Lichens
Zephyranthes
simpsonii
redmargin
zephyrlily G2G3 S2S3 T
436
EAST WRF CONCEPTUAL DESIGN REPORT | CITY OF WINTER SPRINGS
APRIL 2022
Appendix D
ODOR CONTROL ASSESSMENT
437
Winter Springs East and West WRF
Hydrogen Sulfide Monitoring Report
12/21/2021
Prepared for
City of Winter Springs
Prepared by In Association With
Webster Environmental Associates, Inc. Carollo Engineers
13121 Eastpoint Park Blvd, Suite E 200 East Robinson Street, Ste 1400
Louisville, KY 40223 Orlando, FL 32801
438
Winter Springs East and West WRF
Hydrogen Sulfide Monitoring Report
Table of Contents
1.0 Introduction.......................................................................................................... 1
2.0 Site Tours and Weather Conditions ................................................................1
3.0 East WRF Hydrogen Sulfide Monitoring .....................................................3
4.0 West WRF Hydrogen Sulfide Monitoring... .................................................3
5.0 Odor Control Technology Discussion... ........................................................5
Index of Tables
Table 1 East WRF Hydrogen Sulfide Monitoring Summary...........................................3
Table 2 West WRF Hydrogen Sulfide Monitoring Summary .........................................3
Index of Figures
Figure 1 East WRF Hydrogen Sulfide Monitoring Locations .........................................2
Figure 2 West WRF Hydrogen Sulfide Monitoring Locations ........................................4
Appendices
Appendix A East WRF Hydrogen Sulfide Monitoring Charts
Appendix B West WRF Hydrogen Sulfide Monitoring Charts
439
Page | 1
1.0 Introduction
The City of Winter Springs owns and operates the East and West Water Reclamation
Facilities (WRFs). These facilities have both reached the end of their useful life and will
be replaced with new facilities currently being designed by Carollo Engineers (Carollo).
The existing facilities do not currently utilize any type of odor control equipment.
Carollo contracted Webster Environmental Associates (WEA) to monitor hydrogen sulfide
(H2S) emissions at both facilities. The primary objective of this project is to provide Carollo
with baseline H2S data for the existing WRFs as well as to present potential odor control
technology alternatives for the new facilities. The findings and recommendations in this
evaluation are considered preliminary as this evaluation does not include any laboratory
analysis or modeling.
This project includes the following tasks:
• Review relevant background information
• Conduct H2S monitoring for a period of one week
• Analyze H2S monitoring results
• Discussion of potential odor control technologies
• Prepare draft and final reports
2.0 Site Tours and Weather Conditions
Site tours were conducted on November 10, 2021, by WEA and Carollo to become familiar
with each facility and to identify the specific H2S monitoring locations. The loggers were
deployed on the same visit and were left in place for a period of nine days (November 10-
19, 2021). Carollo retrieved the instruments at the end of the monitoring period and shipped
them back to WEA to download the data. The weather was mild during the monitoring
period, with highs in the 70s and 80s and very little rain.
3.0 East WRF Hydrogen Sulfide Monitoring
H2S monitoring was conducted at six locations at the East WRF. The results of the
monitoring are provided as follows:
Figure 1- East WRF Hydrogen Sulfide Monitoring Locations
Table 1- East WRF Hydrogen Sulfide Monitoring Summary
Appendix A- East WRF Hydrogen Sulfide Monitoring Charts
440
Page | 2
Influent Splitter Box
FIGURE 1
EAST WRF HYDROGEN SULFIDE MONITORING LOCATIONS
Surge Tank
Thickener Tank Aerobic Digester Tank
Belt Press Park Entrance
441
Page | 3
All locations were found to have low to moderate concentrations of H2S except for the
surge tank which had very high, brief spikes each day, lasting ~5 minutes, occurring
between 11 am and 2 pm. These concentrations are likely to cause offsite odor detections.
The park entrance instrument recorded two brief spikes, also lasting ~5 minutes that may
be the result of the high H2S coming from the surge tank.
4.0 West WRF Hydrogen Sulfide Monitoring
H2S monitoring was conducted at four locations at the West WRF. The results of the
monitoring are included as follows:
Table 2- West WRF Hydrogen Sulfide Monitoring Summary
Figure 2- West WRF Hydrogen Sulfide Monitoring Locations
Appendix B- West WRF Hydrogen Sulfide Monitoring Charts
All locations were found to have low to moderate concentrations of H2S except for the
influent screen which had a regular diurnal pattern of high H2S each day. These
concentrations are high and have the potential to cause offsite odor detections.
Instrument
Location
Instrument
Range
Logging
Duration
H2S
Average
H2S
Peak
Influent Splitter Box 0-1000 ppm 11/10/21 to 11/19/21 0.12 ppm 2 ppm
SurgeTank 0-1000 ppm 11/10/21 to 11/19/21 3.00 ppm 1201 ppm
Thickener Tank 0-1000 ppm 11/10/21 to 11/19/21 0.00 ppm 0 ppm
Aerobic Digester Tank 0-1000 ppm 11/10/21 to 11/19/21 0.00 ppm 1 ppm
Belt Press 0-200 ppm 11/10/21 to 11/19/21 0.00 ppm 7 ppm
Park Entrance 0-50 ppm 11/10/21 to 11/19/21 0.00 ppm 0.1 ppm
TABLE 1- EAST WRF HYDROGEN SULFIDE MONITORING SUMMARY
Instrument
Location
Instrument
Range
Logging
Duration
H2S
Average
H2S
Peak
Influent Screen 0-1000 ppm 11/10/21 to 11/19/21 20.00 ppm 204 ppm
Aeration Basin Tank 0-1000 ppm 11/10/21 to 11/19/21 0.02 ppm 2 ppm
Aerobic Digester Tank 0-1000 ppm 11/10/21 to 11/19/21 0.28 ppm 3 ppm
Belt Press 0-1000 ppm 11/10/21 to 11/19/21 0.00 ppm 0 ppm
TABLE 2- WEST WRF HYDROGEN SULFIDE MONITORING SUMMARY
442
Page | 4
Influent Screen
FIGURE 2
WEST WRF HYDROGEN SULFIDE MONITORING LOCATIONS
Aeration Basin Tank
Aerobic Digester Tank
Belt Press
443
Page | 5
5.0 Odor Control Technology Discussion
The purpose of this section is to provide a general, high-level discussion of potential odor
control technologies that may be appropriate for the new WRFs that will replace the
existing facilities. Technology selection, sizing, and estimated costs are beyond the scope
of this project.
There are many technologies that could be considered, including bioscrubbers (also known
as biotrickling filters), engineered media biofilters, wood media biofilters, carbon
adsorbers, chemical scrubbers, photoionization, ozone, thermal oxidizers, and others.
Based on WEA’s experience at similar facilities in Florida, the following three
technologies will be discussed:
• Bioscrubbers- applications with moderate to high H2S
• Biofilters- applications with low to moderate H2S and other larger reduced sulfur
compounds (RSCs)
• Carbon Adsorbers- applications with low H2S and can act as a polishing stage
downstream of a biological system (2nd stage of a 2-stage system)
All three of these technologies have known odor removal mechanisms and proven
performance. A general description of each technology is included below.
Bioscrubbers
Bioscrubbing is a biological process with synthetic media contained inside an FRP vessel,
with water circulated over the media. It is excellent for high H2S concentrations and is a
well proven odor control technology for that purpose. No chemicals are required, except
that nutrient may be required if potable water is used in the system. Plant water can be
used, and the media comes with a 10-year warranty (or longer). Pictures of a typical
bioscrubber and media are included below.
444
Page | 6
Biofilters
Biofilters also utilize a biological process, where air flows up through a bed of shredded
wood or engineered media. The engineered media can typically provide a higher efficiency
of odor removal with less media than wood fiber and also comes with a 10-year warranty.
A biofilter is excellent treatment for H2S and other odorous compounds. No chemicals are
required, but a relatively long contact time is required. Biofilters can be open bed or
covered. Pictures of a typical covered biofilter and engineered media are included below.
Carbon Adsorbers
Activated Carbon is a dry adsorption process. The carbon has a very high surface area to
volume ratio and the contaminants are captured within the pore spaces. It is excellent for
low H2S concentrations. No water or chemicals are required, and it is a simple proven
technology. Moisture removal traps would be required on the inlet for more effective air
treatment. Carbon can be installed in different types of vessels, such as single bed, dual
bed or radial flow. Pictures of a typical carbon adsorber and carbon media are included
below.
445
Page | 7
Two-Stage Systems
In an application with high H2S and odor, a carbon system can be connected in series
downstream of a bioscrubber or biofilter to provide an additional level of treatment. The
concept is to utilize the biological stage to remove the majority of the H2S and other
odorous compounds, and then utilize the carbon to polish the air, thus extending the carbon
life. The pictures below illustrate typical 2-stage configurations (the left picture is a
bioscrubber followed by carbon and the right picture is a biofilter followed by carbon).
446
Appendix A
East WRF
Hydrogen Sulfide Monitoring Charts
447
No H2S recorded after this
reading. Sensor may have
become fouled.
448
449
450
451
452
453
Appendix B
West WRF
Hydrogen Sulfide Monitoring Charts
454
No H2S recorded after this
reading. Sensor may have
become fouled.
455
456
457
458
EAST WRF CONCEPTUAL DESIGN REPORT | CITY OF WINTER SPRINGS
APRIL 2022
Appendix E
CWSRF PLANNING DOCUMENT REQUIREMENTS
CHECKLIST
459
PLANNING DOCUMENT REVIEW CHECKLIST WW-02a
1
Revised 8/3/15
This checklist is in accordance with subsection 62-503.700(2), F.A.C. and Rule 62-
503.751, F.A.C. The questions below are used to verify that the planning requirements
of the rule have been met. Complete the questions by checking the appropriate
response or providing the requested information.
SECTION I. GENERAL
1)Project Number and Sponsor
2) List below the title, date and author of all major reports, sources of information,
documents, and correspondence that comprise the complete planning document. These
documents may be referenced by section or page number on the “source” line in
subsequent questions.
3) Briefly describe the major components of the proposed project.
4) Is there sufficient illustrative detail of the local area to identify where the project or
activity is located? [62-503.700(2)(a), F.A.C.] Yes
Sources/Comments
5) Does the planning document include a description of the existing and recommended
facilities, estimated capital costs, estimated operation and maintenance costs, and repair
and replacement costs, if applicable? [62-503.700(2)(b), F.A.C.] Yes
Sources/Comments
460
PLANNING DOCUMENT REVIEW CHECKLIST WW-02a
2
Revised 8/3/15
6) What is the need or justification for the project and what are the environmental and
economic impacts and benefits of the project? [62-503.700(2)(c), F.A.C.]
7) For projects that include new collection areas, is the number of existing septic tanks to be
eliminated documented? Yes N/A .
If so, how many?
8) For reuse projects, is the quantity of water to be conserved provided? Yes N/A
If so, how much annually?
SECTION II. COST COMPARISON AND SELECTED ALTERNATIVE
1) Is a cost comparison of at least three alternatives documented? [62-503.700(2)(d), F.A.C.]
Yes
Sources/Comments
2) Does the planning document discuss the various factors that affected the decision-
making process that lead to the “selected alternative” and was a rationale for selecting
that alternative given? Yes
Sources/Comments
3) Is a project cost breakdown given and does the total cost reflect the data used in the cost
comparison? Yes
Sources/Comments
SECTION III. COST AND EFFECTIVENESS ANALYSIS {33 USC section 1382(b)(13)}
1) Did the planning document include a cost and effectiveness analysis of the processes,
materials, techniques, and technologies for carryout the proposed project?
Yes No
2) Does the selected alternative maximize the potential for water and energy efficiency
considering the cost of constructing, operating and maintaining, and replacing the
project or activity, as necessary? Yes No
461
PLANNING DOCUMENT REVIEW CHECKLIST WW-02a
3
Revised 8/3/15
3)If not, is therH certification that a cost and effectiveness analysis has been conducted?
Yes No
SECTION IV. ENVIRONMENTAL REVIEW
An environmental review is required for each project to be funded. This review includes the
preparation and publication of an Environmental Information Document (EID) by DEP staff.
1) What type EID was issued and on what was the date of publication? [62-503.751(1)(a), F.A.C.]
FFONSI FCEN FEIS/FROD FRAN Date:
2) If a FCEN was issued, what categorical exclusion(s) criteria have been met? N/A
Rehabilitation of existing water pollution control system components or replacement
of structures, materials or equipment.
Water pollution control systems that do not change the existing discharge point or
permitted pollutant concentration limits and that do not involve acquisition of
undisturbed land.
Water pollution control systems that serve less than 10,000 people in unsewered
communities that involve self-contained individual or cluster systems providing both
treatment and disposal of wastewater that will take place near the buildings from which
the wastewater is to be discharged.
Water pollution control systems in areas where streets have been established,
underground utilities installed, or building sites excavated.
Treatment plant upgrades that are solely to enable public access reuse.
3)Does the planning document include a list (obtained from U.S. Fish &Wildlife Service) of
threatened, endangered, proposed, and candidate species and designated critical
habitats that may be present in the project area? Yes N/A
Sources/Comments
4) Will the proposed project have any significant adverse effects upon flora, fauna,
threatened or endangered plant or animal species, surface water bodies, prime
agricultural lands, wetlands, or undisturbed natural areas? No Yes
Sources/Comments
5) Will the proposed project have any significant adverse human health or environmental
effects on minority or low-income communities? No Yes
Sources/Comments
462
PLANNING DOCUMENT REVIEW CHECKLIST WW-02a
4
Revised 8/3/15
6) List any significant adverse environmental effects and what project features will
mitigate such effects? N/A
Sources/Comment
7) Does the project require U.S. Fish &Wildlife Service review and comments?
Yes No
8) If yes, has the U.S. Fish & Wildlife Service issued comments? Yes N/A
Source & Date/Comments
SECTION V. PUBLIC PARTICIPATION [62-503.700(2)(g), F.A.C.]
1) Was a public meeting held to explain the proposed project, the capital cost and the long
term financial impact on the customers; and was the public able to participate in evaluating
project alternatives? Yes
Sources/Comments
2) Date of Public Meeting Date of adopting resolution
3) Have copies of the Notice and minutes of the public meeting been provided and was the
notice in accordance with the local requirements, or 14 days, whichever is greater? Yes
Sources/Comments
SECTION VI. FINANCIAL FEASIBILITY
1) Does the financial information demonstrate the ability to repay the loan including the
coverage factor? [62-503.700(2)(h)1., F.A.C.] Yes
Sources/Comments
2) Does the planning document include completed capital financing plan worksheets
signed by the chief financial officer or the authorized representative? [62-503.700(2)(h)2.,
F.A.C.] Yes
Sources/Comments
3) Does the planning document include the proposed system of charges, rates, fees, and
other collections that will generate the revenues to be dedicated to loan repayment (e.g.
user charge rates)? [62-503.700(2)(h)3., F.A.C.] Yes
Sources/Comments
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4) Has a Fiscal Sustainability Plan or Asset Management Plan been developed?
[33 U.S.C. section 1383(d)(1)(E)]
FSP AMP No
5) If not, is their certification that a fiscal sustainability plan was developed and is being
implemented and will be provided for review before the final disbursement?
Yes No
SECTION VII. UPDATED REQUEST FOR INCLUSION [62-503.700(2)(i), F.A.C.]
1) Does the planning document include an updated request for inclusion that includes an
updated schedule? Yes
Sources/Comments
2) Is there sufficient illustrative detail of the local area to confirm the service area census
tracts? Yes
Sources/Comments
SECTION VIII. PROJECT AUTHORIZATION
1) Has the project received state clearinghouse review and approval or has a DEP permit,
or permits, been issued for the entire project? [62-503.700(2)(f), F.A.C. and 62-503.751(6), F.A.C.]
Yes
2) Does the planning document include an adopting resolution or other action establishing
a commitment to implement the planning recommendations? [62-503.700(2)(j), F.A.C.]
Yes
Sources & Date/Comments
SECTION IX. PROJECT IMPLEMENTATION
1) Is there anything about the proposed project that appears questionable from an
engineering, environmental or financial perspective and therefore requires resolution?
No
Sources/Comments
2) List any proposed service agreements or local contracts necessary to implement the
selected alternative. Also describe the status of each agreement or contract. N/A
Sources/Comments
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3) List any DEP permits (other than a construction permit) needed to implement the
selected plan. N/A
Sources/Comments
SECTION X. INNOVATIVE/ALTERNATIVE PROJECT DESIGNATION
[62-503.700(2)(k), F.A.C.]
1) Is this project to be listed as an Innovative/Alternative (I/A) project? Yes No
2) If yes, does the planning document include documentation of how the project is
categorically I/A or a business case detailing how the project or its components meet the
federal requirements for IA projects in Attachment 2 of EPA’s “Procedures for
Implementing Certain Provisions of EPA’s Fiscal Year 2012 Appropriation Affecting the
Clean Water and Drinking Water State Revolving Fund Programs”, March 2012? Yes
SECTION XI. PLANNING DOCUMENT COMPLETION
1) Is the planning document signed and sealed by a professional engineer? Yes
2) Has the FEID been mailed to the appropriate parties? Yes
3) Have all of the planning related approval dates been entered into the database?
Clearinghouse Approval Yes
U. S. Fish & Wildlife Acceptance Yes
Capital Financing Plan Acceptance Yes
Date of Public Meeting Yes
Date of Adopting Resolution Yes
EID Publication Date Yes
Facilities Plan Acceptance Date Yes
4) Is the planning document approval letter included with this checklist? Yes
ACCEPTANCE
Project Manager________________________________ ___________________
Effective Date
Program Administrator__________________________________
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