2-RWQS Update Final.pdf

Tampa Bay Water Regional Water Quality Study Update

Regional Water Quality Study Update January 2026 / FINAL

Tampa Bay Water Regional Water Quality Study Update

Regional Water Quality Study Update January 2026 / FINAL

This item has been digitally signed and sealed by Erica Stone on the date adjacent to the seal.

Signature must be verified on any electronic copies.

Carollo Engineers, Inc.

200 E Robinson Street, Suite 1400 Orlando, Florida 32801 407.478.4642 407.377.4343

RWQS UPDATE

JANUARY 2026 / FINAL / CAROLLO

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TAMPA BAY WATER RWQS UPDATE i pw://Carollo/FL/Tampa Bay Water/203429-000000/03 Reports and Studies/02 Deliverables/TBW PFAS Treatability Study

Contents

EXECUTIVE SUMMARY 1

INTRODUCTION 5

Background 5 Regulatory Overview 5

Objectives 6

WATER QUALITY REVIEW 6

Historical PFAS Data 6 Regional Surface Water Treatment Plant 7 BUD Wells 10

PFAS Water Quality Goals 13

TREATMENT PROCESS ALTERNATIVES 14

RSWTP 14

BUD Wells 16

BENCH SCALE TESTING 16

Bench Scale Testing Objectives 17 Rapid Small-Scale Column Tests (RSSCT) 17 SIX Jar Testing 19

Bench-Scale Testing Results 20 Sample Baseline Water Quality 20 RSSCT Results 23 SIX Jar Test Results 27 Overall Conclusions from Bench-Testing 33

CONCEPTUAL DESIGN 34

BUD Wells 34 Nitrate Removal 34 PFAS Removal 35

RSWTP 36

SIX Design Criteria 36 Existing Filter GAC Design Criteria 37 GAC Post-Filter Adsorber Design Criteria 37

Cost Analysis 37 Assumptions 37 Nitrate Removal 38 PFAS Removal 39

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Process Flow Diagrams and Site Plans 40

RSWTP 40

Site Assessments 49 Permitting 49

IMPLEMENTATION PLAN 51

Overview of Recommended Treatment Process Improvements 51 Implementation Plan 52

Phase 1 52 Phase 2 54 Phase 3 55

Implementation Schedule for Recommended Improvements 55 Impact on PFAS Compliance Schedule 56 Cost Estimates 56

Appendices

APPENDIX A UCMR5 SAMPLING RESULTS

APPENDIX B LAB RESULTS – SOURCE WATER QUALITY

APPENDIX C LAB RESULTS – SIX JAR TESTING

APPENDIX D LAB RESULTS – RSSCTS

Tables Table ES.1 Recommended Implementation Phasing and Associated Capital Costs 2 Table ES.2 Phase 1 Implementation Plan and Capital Cost Updates 3 Table ES.3 Phase 2 Implementation Plan and Capital Cost Updates 3 Table ES.4 Phase 3 Capital Cost Updates 4 Table 1 PFAS NPDWR Limits 6 Table 2 RSWTP Source Water During Sampling Events 10 Table 3 PFAS Drinking Water Quality Goals 13 Table 4 RSSCT Design Overview 18 Table 5 Analytical Methods Tested for RSSCTs 18 Table 6 Summary of SIX Jar Test on RSWTP Raw Water 19 Table 7 Analytes Tested During SIX Jar Testing 19 Table 8 RSWTP Raw Water Quality 21 Table 9 RSWTP Sample PFAS (PFAS method EPA 533 by Pace Analytical) 21 Table 10 BUD Well Sample Results 22 Table 11 BUD-5 WTP Flow Distribution During Sampling Event 23 Table 12 PFAS MCL Exceedances in Samples Collected 8/20/24 23 Table 13 Bench-Scale FBIX RSSCT Performance 25 Table 14 Bench GAC RSSCT Performance 27 Table 15 PFOA Percent Removal by SIX 28 Table 16 PFOS Percent Removal by SIX 28

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Table 17 Nitrate-FBIX Design Criteria 35 Table 18 PFAS-FBIX Design Criteria 36 Table 19 SIX Design Criteria 36 Table 20 GAC Post-Filter Adsorber Design Criteria 37 Table 21 Cost Comparison of Nitrate Removal Alternatives 38 Table 22 Cost Comparison of PFAS Removal Alternatives at the BUD Sites 39 Table 23 Cost Comparison of PFAS Removal Alternatives at the RSWTP 39 Table 24 Available Property 49 Table 25 Permitting Summary for Tampa Bay Water Treatment Sites 50 Table 26 Recommended Project by Supply Source 51 Table 27 Phase 1 Capital Costs 56 Table 28 Phase 2 Capital Costs 57 Table 29 Phase 3 Capital Costs 58

Figures Figure 1 301REGHILLS POC Regional Supply (Finished Water) 7 Figure 2 RSWTP Regulated PFAS (Sampled 8/20/24) 8 Figure 3 RSWTP Flow with Source Breakdown (July 2023-April 2024, UCMR5 sampling) 9 Figure 4 RSWTP Flow with Source Breakdown (April 2024-December 2024, ongoing supplemental sampling) 9 Figure 5 BUD-2 PFAS Detection 11 Figure 6 BUD-4 PFAS Detection 11 Figure 7 BUD-5R PFAS Detection 12 Figure 8 BUD-6 PFAS Detection 12 Figure 9 BUD-7 PFAS Detection 13 Figure 10 Locations Evaluated for PFAS Treatment at RSWTP 15 Figure 11 RSWTP Raw Water Sample (8/20/2024, TOC of 25.7 mg/L) 20 Figure 12 RSWTP Filtered Effluent Sample (8/20/2024) 22 Figure 13 PFOA, PFOS, TOC, and Nitrate Breakthrough Curves from FBIX RSSCT Column at BUD-5 WTP 24 Figure 14 PFOA, PFOS, TOC and Nitrate Breakthrough Curves from FBIX RSSCT Column at BUD-7 WTP 25 Figure 15 PFOA, PFOS, and TOC Breakthrough Curves from GAC RSSCT Column

Simulating Existing Filter GAC at the RSWTP 26 Figure 16 PFOA, PFOS, and TOC Breakthrough Curves from GAC RSSCT Column

Simulating GAC Post-Filter Adsorber at the RSWTP 27 Figure 17 PFOA Removal by SIX 28 Figure 18 PFOS Removal by SIX 29 Figure 19 TOC Removal by SIX 30 Figure 20 Apparent Color Removal by SIX 30 Figure 21 Alkalinity Removal by SIX 31 Figure 22 Bromide Removal by SIX 31 Figure 23 Chloride Addition by SIX 32 Figure 24 Sulfate Removal by SIX 32

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Figure 25 Process Flow Diagram for the Proposed SIX Treatment in the RSWTP 41 Figure 26 Site Plan for the RSWTP with the Proposed SIX 42 Figure 27 PFD for the Proposed FBIX in the BUD-5 WTP 44 Figure 28 PFD for the Proposed FBIX in the BUD-7 WTP 45 Figure 29 Site Plan for BUD-5 WTP with the Proposed FBIX Treatment 46 Figure 30 Site Plan for BUD-7 WTP with the Proposed FBIX Treatment 47 Figure 31 Packaged Nitrate-FBIX System (Envirogen Technologies, Inc.) 48

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Abbreviations µg/L micrograms per liter µS/cm microsiemens per centimeter AACE Association for the Advancement of Cost Engineering abs cm-1 absorbance per centimeter BAC biologically activated carbon BAT best available technology BUD Brandon Urbanized Wellfield BV bed volume C.U. color unit CaCO3 calcium carbonate Carollo Carollo Engineers CIP Capital Improvements Program cm centimeter CRWQMP Comprehensive Regional Water Quality Monitoring Plan CSMR chloride-to-sulfate-mass DBP disinfection byproduct DF diffusivity factor EBCT empty bed contact time ENR CCI Engineering News-Record Construction Cost Index EPA Environmental Protection Agency FBIX fixed bed ion exchange FDA forced draft aeration g/L grams per liter GAC granular activated carbon gpm/ft2 gallons per minute per square foot HFPO-DA hexafluoropropylene oxide dimer acid HI Hazard Index HLR hydraulic loading rate IX ion exchange M million M/yr million per year MCL maximum contaminant level MCLG maximum contaminant level goal MDL method detection limit mg/L milligrams per liter mgd million gallons per day mL/L milliliters per liter mL/min milliliters per minute

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TAMPA BAY WATER RWQS UPDATE vi mm millimeters mV millivolts NaCl sodium chloride NF nanofiltration ng/L nanograms per liter nitrate-FBIX FBIX for nitrate removal NOI Notice of Intent NPDES National Pollutant Discharge Elimination System NPDWR National Primary Drinking Water Regulation NTU nephelometric turbidity unit O&M operations and maintenance PAC powdered activated carbon PFAS per- and polyfluoroalkyl substances PFAS-FBIX FBIX for PFAS adsorption PFBS perfluorobutanesulfonic acid PFHxS perfluorohexane sulfonic acid PFNA perfluorononanoic acid PFOA perfluorooctanoic acid PFOS perfluorooctane sulfonic acid POC point of connection ppb parts per billion ppt parts per trillion RAA running annual average RO reverse osmosis ROW right-of-way RSSCT rapid small-scale column test RSWTP Regional Surface Water Treatment Plant RWQS Regional Water Quality Study S.U. standard units SCHREG POC Hillsborough County’s Lithia WTP SIX suspended ion exchange TBC Tampa Bypass Canal TOC total organic carbon UCMR5 Unregulated Contaminant Monitoring Rule UVT ultraviolet transmittance Water ARC® Carollo’s Water Applied Research Center WF water facility WTP water treatment plant WUP Water Use Permit

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EXECUTIVE SUMMARY

Tampa Bay Water completed a Regional Water Quality Study (RWQS) in April 2023. The RWQS defined optimized solutions for reduction of primarily total organic carbon (TOC), among other parameters, as requested by the Member Governments at that time, and included an implementation plan to guide Tampa Bay Water and the Member Governments in the process of achieving enhanced water quality. In April 2024, the Environmental Protection Agency (EPA) promulgated the final National Primary Drinking Water Regulation (NPDWR) for per- and polyfluoroalkyl substances (PFAS). This study provides an update to the RWQS recommendations with inclusion of EPA’s PFAS maximum contaminant levels (MCL) to the water quality goals.

Upon review of the available PFAS data, two source waters were identified as requiring a PFAS treatability study – surface water feeding the Regional Surface Water Treatment Plant (RSWTP) and groundwater feeding the Brandon Urban Dispersed (BUD) Wells. The EPA’s three best available treatment technologies for PFAS treatment in drinking water were evaluated for each of these sites: granular activated carbon (GAC), ion exchange, and high-pressure membranes. Bench testing was conducted to evaluate short-listed treatment approaches including fixed bed ion exchange (FBIX) for the BUD Water Treatment Plants (WTPs) to reduce PFAS in these relatively low TOC waters as well as Suspended Ion Exchange (SIX) and GAC for the RSWTP to reduce PFAS and TOC in these relatively high TOC waters. TOC reduction using SIX, which also reduces PFAS, improves performance of downstream GAC to further reduce PFAS and consistently achieve EPA’s MCLs.

Results from the bench testing informed updates to the recommended treatment approaches and associated planning-level study costs. The overall recommendations include adding treatment to the existing RSWTP and BUD-5 and BUD-7 WTP sites. Specifically for the BUD WTPs, it is recommended to install fixed bed ion exchange (FBIX) vessels for PFAS removal. With FBIX for PFAS treatment at these sites, it is recommended to also use FBIX for nitrate treatment to maintain like systems. A nitrate goal of

0.4 mg/L NO3-N is listed in the 2023 RWQS and carried through in this RWQS Update. Nitrate concentrations at the BUD-5 and BUD-7 WTP sites are elevated above the goal, which is less than the NPDWR standard of 10 mg/L. To achieve the nitrate goal of less than 0.4 mg/L, it is recommended to install FBIX for nitrate treatment at the BUD WTP sites, but at a later time as a lower-priority, long-term project. In this way, Tampa Bay Water and the Member Governments have time to determine if nitrate treatment is desired at this level.

Of the treatment approaches bench tested for the RSWTP, SIX is the most cost-effective treatment option due to the downstream benefits of chemical and energy cost savings, reduced filter backwashing, and potentially increased water production resulting from lower TOC. SIX also significantly reduces the high operational cost associated with GAC media replacement for PFAS reduction in the presence of high TOC concentrations. Additionally, treatment at the RSWTP provides a reduction of PFAS concentrations to most of the Regional System. It is recommended to continue to prioritize a SIX and GAC demonstration at the RSWTP to collect design criteria data and refine operational parameters and costs for PFAS treatment under typically highly variable TOC and other source water quality conditions.

It is also recommended to continue to prioritize the three Phase 1 projects (RSWTP, BUD-5 WTP, and BUD-7 WTP) to comply with EPA’s PFAS MCL requirements.

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The remaining two Phase 1 projects (Eldridge Wilde ozone-GAC and South Pasco FBIX), while not required to satisfy a regulatory requirement, would achieve TOC reduction, as requested by Member Governments to achieve more stable chloramine residuals, particularly during summer months. These two locations are included in Phase 1 because these sites will be undergoing near-term design and construction improvements as existing Capital Improvements Program (CIP) projects, which would result in cost savings as part of ongoing activities (versus later and separate design and construction). By advancing these two sites, which use the two different technologies recommended for TOC reduction, FBIX and ozone-GAC, this would provide full-scale groundwater treatment operational data to better inform the five Phase 2 TOC reduction projects and the up to ten Phase 3 TOC reduction projects. In this way, Tampa Bay Water and the Member Governments have time and performance data to determine the full benefits of region-wide TOC treatment benefits.

The implementation plan has been updated since the RWQS to prioritize meeting PFAS compliance. For example, implementing SIX at the RSWTP was previously in Phase 2 and has been moved to Phase 1. BUD PFAS treatment is recommended for Phase 1 while nitrate treatment at the BUD sites remains in Phase 2.

Capital costs for each recommended implementation phase and associated updates are provided in Table ES.1 through Table ES.4. In addition to the cost impacts due to re-prioritization of the implementation plan, other cost updates include changes to the recommended treatment (i.e., nitrate FBIX instead of Biottta and PFAS FBIX for BUD WTPs), as well as direct cost updates (i.e., $2022 to $2024 and updates to SIX costs based on information from the Tippin SIX demonstration). Note that costs presented are planning-level study costs that will be scheduled and programmed into the Tampa Bay Water CIP with appropriate escalations due to timing. These CIP costs, which will include potential changes to the Uniform Rate, are currently being developed and refined by Tampa Bay Water, and will be discussed with Member Governments in 2026, prior to the agency seeking Board action. In this way, Tampa Bay Water and the Member Governments have time for further discussion in the future on increases to the Uniform Rate versus overall system benefit of TOC reduction. Additional details on planning-level study costs are discussed in the Cost Analysis Assumptions section of this report.

Table ES.1 Recommended Implementation Phasing and Associated Capital Costs(1)

Phase RWQS Update 2023 RWQS(2) Years Phase 1 $229.2M $140.4M 1-6 Phase 2 $239.6M $260.9M 7-12 Phase 3 $126.8M $120.0M 13-15

TOTAL $595.6M(3) $521.3M(4)

Notes:

(1) Cost estimates are provided in $2024 without escalation to mid-point of construction as planning-level estimates. CIP costs will be programmed and escalated accordingly.

(2) Breakdown of the numbers are found in the 2023 RWQS and not in this report because of recommended changes in treatment location priorities and processes.

(3) Total is the sum of the subtotals in Tables ES.2, ES.3, and ES.4.

(4) Total from the 2023 RWQS and not the sum of the subtotals in Tables ES.2, ES.3, and ES.4.

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Table ES.2 Phase 1 Implementation Plan and Capital Cost Updates(1)

Project Description RWQS Update Capital Cost ($M)

2023 RWQS

Capital Cost ($M)

2023 RWQS Phase

Phase 1A RSWTP SIX Demonstration $2.3 $2.2 1C Subtotal $2.3 $2.2 Phase 1B

BUD-5 WTP PFAS-FBIX $5.1 N/A N/A

BUD-7 WTP PFAS-FBIX $1.9 N/A N/A

RSWTP SIX $128.6 $74 2C

Subtotal $135.6 $74 Phase 1C Eldridge Wilde Ozone-GAC $77.6 $73.4 1A South Pasco FBIX $13.7 $13 1A Subtotal $91.3 $86.4

TOTAL $229.23 $162.6

Notes:

(1) Cost estimates are provided in $2024 without escalation to mid-point of construction as planning-level estimates. CIP costs will be programmed and escalated accordingly.

Table ES.3 Phase 2 Implementation Plan and Capital Cost Updates(1)

Project Description RWQS Update Capital Cost ($M)

2023 RWQS

Capital Cost ($M)

2023 RWQS Phase

Phase 2A Cypress Creek FBIX $15.7 $14.9 1B Cross Bar Ranch FBIX and Greensand

$39.0 $36.9 1B

Subtotal $54.7 $51.8 Phase 2B Cosme Odessa Ozone-GAC $58.0 $54.9 2A Starkey Ozone-GAC $41.1 $38.9 2A Section 21 FBIX $13.4 $12.7 2A Northwest Hillsborough Ozone-GAC

$46.3 $43.8 2A

Morris Bridge FBIX $13.1 $12.4 2A Subtotal $171.9 $162.7 Phase 2C BUD 5 WTP Nitrate-FBIX $8.3 $16.1 (Biottta) 2B BUD 7 WTP Nitrate-FBIX $4.6 $8.1 (Biottta) 2B Subtotal $12.9 $24.2

TOTAL $239.6 $238.7

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Notes:

(1) Cost estimates are provided in $2024 without escalation to mid-point of construction as planning-level estimates. CIP costs will be programmed and escalated accordingly.

Table ES.4 Phase 3 Capital Cost Updates(1)(2)

Project Description RWQS Update Capital Cost ($M) 2023 RWQS Capital Cost ($M) Option A – 1.5 mg/L TOC Target Cypress Bridge FBIX $14.0 $13.2 South Pasco FBIX $2.9 $2.7 Cypress Creek FBIX $4.4 $4.2 Cross Bar Ranch FBIX $12.7 $12.0 Section 21 FBIX $2.4 $2.3 Northwest Hillsborough Ozone-GAC $2.7 $2.6 Morris Bridge FBIX $0.8 $0.8

TOTAL $39.9 $37.8

Option B – 1.25 mg/L TOC Target South-Central Hillsborough GAC $38.5 $44.5 Cypress Bridge FBIX $16.7 $18.2 Eldridge Wilde Ozone-GAC $0.2 $0.2 South Pasco FBIX $5.3 $5.0 Cypress Creek FBIX $4.4 $4.2 Cross Bar Ranch FBIX $13.5 $12.8 Cosme Odessa Ozone-GAC $0.2 $0.2 Section 21 FBIX $3.2 $3.0 Northwest Hillsborough Ozone-GAC $6.1 $5.8 Morris Bridge FBIX $3.7 $3.5

TOTAL $91.8 $97.4

Option C – 1 mg/L TOC Target South-Central Hillsborough GAC $47.0 $44.5 Cypress Bridge FBIX $19.2 $18.2 Eldridge Wilde Ozone-GAC $0.2 $0.2 South Pasco FBIX $11.9 $11.3 Cypress Creek FBIX $9.7 $9.2 Cross Bar Ranch FBIX $20.5 $19.4 Cosme Odessa Ozone-GAC $0.2 $0.2 Section 21 FBIX $6.4 $6.1 Northwest Hillsborough Ozone-GAC $7.8 $7.4 Morris Bridge FBIX $3.7 $3.5

TOTAL $126.8 $120

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Notes:

(1) Phase 3 implementation prioritization is unchanged from the 2023 RWQS.

(2) Cost estimates are provided in $2024 without escalation to mid-point of construction as planning-level estimates. CIP costs will be programmed and escalated accordingly.

INTRODUCTION

Background Since its inception, Tampa Bay Water has continued to provide high quality water, meeting or exceeding federal and state standards to its Member Governments. Tampa Bay Water completed a Regional Water Quality Study (RWQS) in April 2023. The RWQS defined optimized solutions for reduction of primarily total organic carbon (TOC) and included an implementation plan that will guide Tampa Bay Water and the Member Governments in the process of achieving enhanced water quality. Reduction of TOC was a priority in the RWQS, along with other water quality parameters that included color, sulfide, iron, and nitrate.

Desktop, bench scale, and pilot testing were completed as part of the RWQS, along with regional system water quality blend modeling and a comparison of cost and non-cost considerations for individual treatment options to identify the recommended treatment technologies for each of the Tampa Bay Water treatment facilities.

Regulatory Overview In April 2024, the Environmental Protection Agency (EPA) promulgated the final National Primary Drinking Water Regulation (NPDWR) for per- and polyfluoroalkyl substances (PFAS). The NPDWR identifies maximum contaminant levels (MCLs) and maximum contaminant level goals (MCLGs) for five individual PFAS and one PFAS mixture (PFAS HI) as listed in Table 1. These MCLG are non-enforceable public-health goals. For PFOS and PFOA the MCLG is 0. The MCL is enforceable and set as close to the MCLG as feasible, using best available treatment technology and considering costs.

The Hazard Index (HI) is calculated as a sum of the measured concentration of each of the four PFAS divided by its corresponding health reference value, as shown in the following equation. The rule requires compliance by April 26, 2029. On this date, the four-quarter running annual average (RAA) will be calculated using the previous four quarters’ data; this implies that treatment must be in place by April 2028 to ensure the RAA is below the MCL by the compliance date.

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2000 𝑛𝑛𝑛𝑛/𝐿𝐿

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10 𝑛𝑛𝑛𝑛/𝐿𝐿

In a May 2025 press release, the EPA indicated intent to rescind all but PFOS and PFOA MCLs and to extend the compliance deadline to 2031. While revised draft regulations are still pending as of the writing of this report, the extended deadline would provide some schedule flexibility but treatment would still be required to meet the updated compliance requirements.

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Table 1 PFAS NPDWR Limits

Parameter MCL (enforceable levels)

MCLG

(health based, non-enforceable)

PFOA 4.0 ng/L zero PFOS 4.0 ng/L zero PFHxS 10 ng/L 10 ng/L PFNA 10 ng/L 10 ng/L HFPO-DA (GenX) 10 ng/L 10 ng/L PFAS HI (mixture MCL) 1.0 (unitless) 1.0 (unitless)

General Notes:

Running annual average (RAA) from quarterly sampling.

This study provides an update to the RWQS recommendations with addition of PFAS to the water quality goals.

Objectives The goal of this RWQS Update is to review the PFAS characterization and treatability study data, evaluate PFAS management strategies, and incorporate PFAS treatment, if needed, in the RWQS’ previously identified treatment solutions. The specific objectives of the RWQS Update are to:

Revisit and revise the previously defined treatment system design criteria for TOC to meet PFAS treatment goals (where needed, based on the available PFAS data).

Provide an estimate of capital and operation and maintenance (O&M) costs for the treatment system refinement/ revision.

WATER QUALITY REVIEW

Historical PFAS Data A robust review of all water quality data was undertaken for the RWQS. As water quality has aligned with historical trends, only water quality relevant to PFAS treatment performance is discussed herein. Of all active Tampa Bay Water regional water delivery locations or points of connection (POC), those associated with the Regional Surface Water Treatment Plant (RSWTP) sources and the Brandon Urban Dispersed (BUD) Wells were found to require a PFAS treatability study. Note that all PFAS data shown in this report have been analyzed by the Tampa Bay Water laboratory unless otherwise noted. Specifically, the August 2024 bench test results presented were analyzed by Pace Analytical Laboratory.

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Regional Surface Water Treatment Plant The RSWTP, which currently has a maximum day design capacity of 120 million gallons per day (mgd) and typically operates at an average 90 mgd, provides enhanced coagulation, intermediate ozone and biological activated carbon (BAC) filtration. The RSWTP receives raw water from three sources (Alafia River, Tampa Bypass Canal [TBC], and the C.W. Bill Young Regional Reservoir), and the finished water blends with the desalination product water when operational. The relative amount of each source impacts water quality at the plant, with significant seasonal variability. The RSWTP is currently undergoing expansion to meet growing demands.

PFAS was monitored in RSWTP finished water delivered to Member Governments at POCs by Tampa Bay Water, and at subsequent downstream point of entry locations by individual Member Governments during the Fifth Round Unregulated Contaminant Monitoring Rule (UCMR5) program. This sampling began in July 2023 and continued quarterly through April 2024, with a total of four sampling events. The UCMR5 data collected by Tampa Bay Water and the Member Governments are provided in Appendix A.

In July 2024, supplemental monthly sampling by Tampa Bay Water commenced. Of the 29 measured PFAS, the regulated PFAS levels from the sampling through December 2024 are summarized in Figure 1.

Of the regulated PFAS, PFOS and PFOA were the only compounds observed to be above the respective MCL of 4 ng/L. PFNA has been detected in the finished water three times above a detection limit of

0.6 ng/L by the Tampa Bay Water lab. PFHxS was detected below the MCL of 10 ng/L. PFBS does not have an MCL, and levels were found to be well below the health-based reference level (2,000 ng/L).

Note: Bars with hatching designate non-detect values.

Figure 1 301REGHILLS POC Regional Supply (Finished Water)

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During the collection of bulk water (August 20, 2024) for PFAS benchtop treatability testing (described in a subsequent section of this RWQS Update report), samples were collected to capture PFAS concentrations in the raw water and fate through the treatment plant. These data were analyzed by a third-party laboratory (lab) (Pace Analytical) and shown in Figure 2.

The data are consistent with the finished water sampling to date with PFOS and PFOA being the only compounds detected near or in exceedance of the respective MCL in both the raw and ozonated effluent water. These data indicate that there is some removal of regulated PFAS through the existing treatment processes; however, this observation is limited to a single sample. It is recommended collect additional in-plant samples to better characterize the fate of PFAS through the plant, including waste streams, especially those recycled to the head of the plant. PFNA was not detected by the Pace lab during the in-plant sampling event (August 20, 2024, method detection limit [MDL] of 1 ng/L). HFPO-DA was found to be non-detect with an MDL max of 1.58 ng/L. PFBS was again found to be well below the health-based reference level.

Figure 2 RSWTP Regulated PFAS (Sampled 8/20/24)

The RSWTP flow is driven by a variety of factors including short- and mid-term environmental climate conditions, surface water availability, and adherence with groundwater water use permit (WUP) compliance. UCMR5 sampling followed an unusually dry rainy season with corresponding RSWTP flow data (July 2023 through April 2024) suggesting an average plant flow of 87 mgd with the predominant source varying throughout the year (Figure 3). Supplemental monthly sampling beginning in July 2024 followed a more typical rainy season (Figure 4). The source water breakdown for the PFAS monitoring sampling events to date is summarized in Table 2. This data indicates slightly elevated PFOS and PFOA concentrations following a more typical rainy season when compared to the earlier UCMR5 data. It is important to continue to monitor PFAS in the source water(s) to better understand the impact of the sources on PFAS occurrence and trends at the RSWTP.

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Figure 3 RSWTP Flow with Source Breakdown (July 2023-April 2024, UCMR5 sampling)

Figure 4 RSWTP Flow with Source Breakdown (April 2024-December 2024, ongoing supplemental sampling)

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Table 2 RSWTP Source Water During Sampling Events

Sample Date(2) Alafia River Reservoir TBC FW PFOS(1) FW PFOA

7/17/2023 (UCMR5) 0% 0% 100% 4.3 2.7

10/9/2023 (UCMR5) 23% 34% 43% 3.2 2.4

1/8/2024 (UCMR5) 6% 0% 94% 3.1 2.8

4/15/2024 (UCMR5) 29% 19% 52% 3.9 2.6

7/8/2024 78% 22% 0% 5.2 3.9 8/8/2024 0% 0% 100% 4.4 2.6 8/20/2024 0% 0% 100% 3.9(3) 3.1(3) 9/4/2024 0% 0% 100% 3.2 2.2 10/22/2024 44% 0% 55% 4.4 3.3 11/20/2024 48% 0% 52% 5.6 3.5

Abbreviations: FW – finished water.

Notes:

(1) Bolded values exceed MCL.

(2) All samples collected at 301REGHILLS POC during UCMR5 sampling unless otherwise noted.

(3) 8/20/2024 sample collected for PFAS Treatability Study. PFOS/PFOA from post-filtration, rather than FW.

BUD Wells The BUD wells consist of a series of five wells being treated at two sites, the BUD-7 water treatment plant (WTP) and the BUD-5 WTP. BUD-7 WTP treats the flow from BUD-7. BUD-5 WTP treats the combined flow from BUD-2, 4, 5R, and 6. BUD-5R was offline for more than 1 year undergoing rehabilitation and maintenance during most of this study and was returned to service in December 2024.

The actively pumping BUD wells were individually sampled for PFAS and analyzed at the Tampa Bay Water laboratory on March 20, 2024 and April 15, 2024. Subsequently, monthly supplemental monitoring of the BUD wells commenced in July 2024 by Tampa Bay Water. The regulated PFAS results are shown in Figure 5 through Figure 9. PFOS and PFOA are in exceedance or near the MCL reference point of 4 ng/L for BUD-4, 6, and 7. Little detection of PFAS was observed at BUD-2. HFPO-DA and PFNA have not been detected at any BUD wells. PFBS has been detected, but well below the health-based reference level (2,000 ng/L). BUD-5R was offline for much of the sampling due to ongoing maintenance but was sampled December 17, 2024 when it was returned to service. Based on that single sample, BUD-5R has an exceedance of PFOS and lower PFOA than BUD-4, 6, and 7. Note that BUD-7 was not sampled April 15, 2024. BUD-4 and BUD-7 have the highest regulated PFAS detection from the data collected to date.

Continued sampling of the BUD wells is recommended due to the variability observed.

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Figure 5 BUD-2 PFAS Detection

Figure 6 BUD-4 PFAS Detection

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Figure 7 BUD-5R PFAS Detection

Figure 8 BUD-6 PFAS Detection

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Figure 9 BUD-7 PFAS Detection

PFAS Water Quality Goals The goal of this RWQS Update is to identify an implementation plan to achieve MCL compliance for PFAS at all Tampa Bay Water POCs. As such, water quality goals are outlined in Table 3 to match the MCLs. This work updates the RWQS that previously established TOC targets of 1.0 to 2.0 milligrams per liter (mg/L) and a nitrate goal of 0.4 mg/L as N.

Table 3 PFAS Drinking Water Quality Goals

Parameter Goal PFOA < 4.0 ng/L (MCL) PFOS < 4.0 ng/L (MCL) PFHxS < 10 ng/L (MCL) PFNA < 10 ng/L (MCL) HFPO-DA (GenX) < 10 ng/L (MCL)

PFAS HI < 1.0 (MCL)

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TREATMENT PROCESS ALTERNATIVES

PFAS treatment technologies have been evaluated for PFAS removal with considerations for both cost and efficacy. The EPA’s identified best available technologies (BATs) that have been robustly tested for full-scale applications of PFAS treatment include the following:

1. Granular activated carbon (GAC).

2. Ion exchange (IX).

3. High pressure membranes, such as nanofiltration (NF) or reverse osmosis (RO).

High pressure membranes were eliminated as an option for these Tampa Bay Water sources identified to required PFAS treatment due to higher energy cost and volume of waste residuals (concentrate) combined with the low levels of PFAS detected (when compared to other utilities that are considering NF/RO). Novel adsorbent medias are also available for full-scale use, but limited full-scale implementation presents uncertainty regarding long-term reliability. Co-contaminant competition, namely organics, limits the applicability of IX resin for PFAS adsorption, which is typically applied for source water where TOC is less than approximately 2 mg/L. Furthermore, PFAS-IX resin is single-use and manufacturers also do not recommend that this resin be backwashed to avoid disturbing the mass transfer zone. Organic or TOC fouling of the media still occurs with the use of GAC, but the impact on PFAS treatment performance is lesser than IX resin. With elevated TOC concentration, GAC usage rates to achieve PFAS compliance will increase. Unlike PFAS-IX resin, GAC can be reactivated offsite and reused. While each of the three BATs have their benefits and tradeoffs, site-specific requirements and anticipated costs dictate which are best for Tampa Bay Water.

RSWTP

Due to the high level of organics present in the Tampa Bay Water surface water sources, fixed bed ion exchange (FBIX) is not suitable for PFAS adsorption at the RSWTP following the BAC process. However, TOC pretreatment in the form of suspended ion exchange (SIX) can provide TOC removal, among other water quality benefits previously discussed in the RWQS, and some PFAS removal. Although SIX is not a PFAS removal technology, the low PFAS occurrence in the surface water, the ability to meet the PFAS MCL, and the additional treatment plant benefits make SIX a viable alternative for PFAS treatment at the RSWTP. For the City of Tampa’s Tippin Water Treatment Facility with similar source water quality and treatment train, benefits included a 70 percent reduction in coagulant demand, 30 percent reduction in ozone demand, at least 50 percent improvement in filter run volume, and the elimination of sulfuric acid at the plant as well as reduction in capital projects required for capacity expansion. Reduced coagulant results in less solids production, which means less solids handling required but also less product available for resale. Historically, the conventional regenerable IX process has not been seen as a PFAS removal technology, but it is theorized that SIX has such a higher regeneration frequency that PFAS removal occurs. Carollo Engineers (Carollo) has helped optimize conventional FBIX processes and increased the resin regeneration frequency at a full-scale water treatment plant in South Florida and similar PFAS removals to SIX were observed.

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Alternatively, post-filter GAC adsorbers could be implemented to remove PFAS from the filtered water prior to disinfection. This GAC would be replaced once effluent or finished water PFAS treatment targets are exceeded. An even more robust approach to treat PFAS at the RSWTP would be to add both SIX pretreatment and GAC post-filter adsorbers. With the pretreatment of TOC, PFOS, and PFOA removal provided by SIX, the GAC is expected to last much longer. This scenario is not able to be evaluated reliably at the bench scale due to inability to produce representative process samples. A pilot would be required to fully test this scenario and quantify the impacts from seasonal variability in water quality and long-term O&M cost savings by pretreating TOC via the SIX process.

A potential short-term approach (or long-term addition to SIX) is to utilize the existing GAC filters for both filtration and adsorption. This is likely not a long-term solution alone due to the expected high GAC changeout rates induced by backwashing the media and disturbing the PFAS mass transfer zone, along with the larger GAC media (compared to adsorbers). However, some PFAS removal is possible without needing to build new infrastructure at full plant capacity (120 mgd). Although this approach will result in relatively shorter GAC service life during full-scale operation, there are other operational approaches to help mitigate the challenge regarding mass transfer zone disturbance, for example, minimizing backwash flowrates, and/ or reducing air scour. These operational approaches, however, could in turn adversely impact filter performance in terms of turbidity and and/ or TOC reduction. Piloting is therefore required to fully understand the implications of this approach. Depending on the piloting results, this approach could perhaps provide an interim solution, before a permanent PFAS treatment process is implemented at the RSWTP. Alternatively, it would serve as a secondary PFAS treatment barrier when combined with SIX.

In summary, the short-listed technologies for RSWTP include the following:

1. SIX for raw water PFAS treatment and additional plant benefits.

a. TOC reduction.

b. Other anion removal (i.e., sulfate, bromide, bicarbonate).

c. Overall plant O&M savings and capital expansion reduction.

2. GAC post-filtration adsorbers for PFAS polishing.

3. Existing filter GAC adsorption for ozonated effluent PFAS treatment within the existing filters. This potential option requires further validation with pilot testing and is likely more viable when SIX pretreatment is installed.

RSWTP PFAS treatment solutions tested are summarized in Figure 10.

Figure 10 Locations Evaluated for PFAS Treatment at RSWTP

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BUD Wells Given there is lower TOC concentration in the groundwater source from the BUD wells (less than

2.0 mg/L) than the surface water sources, FBIX for PFAS adsorption (PFAS-FBIX) is the most suitable treatment approach for this application. The small site footprint at the BUD-7 WTP, previously identified in the RWQS, will pose a challenge. The BUD-5 WTP site has ample footprint to accommodate a PFAS treatment process if needed. Both the BUD-7 WTP and BUD-5 WTP sites were evaluated for PFAS-FBIX treatment.

All BUD well water is blended at the Regional Supply to Hillsborough County’s Lithia WTP (SCHREG POC).

As such, the regulatory RAA will be determined at the SCHREG POC and at the current BUD WTPs POEs.

With non-steady state adsorptive technologies applied, treated concentrations will increase over time requiring a monitoring plan. Tracking spreadsheets can be developed to understand allowable PFAS concentration leaving respective BUD treatment sites given the respective flow blends at the SCHREG POC. Although blending does not allow for the avoidance of PFAS treatment of the BUD wells all together, tracking the concentrations can allow for optimizing resin replacement frequencies. This study has assumed treatment technologies will be operated to maintain PFAS compliance at each POE;, according to the Comprehensive Regional Water Quality Monitoring Plan (CRWQMP Revision 22, regulatory compliance must be met at both the POEs and POCs.

In the RWQS, the BUD WTPs were low in priority for treatment due to nitrate being the only contaminant needing to be addressed to meet water quality goals. However, given the PFAS detection, these sites rise in priority for treatment due to the need to meet the upcoming PFAS regulatory requirements. BUD well water nitrate exceeds the RWQS finished water goal of 0.4 mg/L as N at BUD-7 (2.4 mg/L), BUD-4 (1.8 mg/L), and BUD-6 (1.3 mg/L), but is below the NPDWR MCL of 10 mg/L. Although biottta® was recommended for nitrate reduction at the BUD WTPs in the RWQS, the incorporation of PFAS along with the required nitrate removal revises the feasible and recommended technology at the BUD sites to FBIX for nitrate removal (nitrate-FBIX). Nitrate-FBIX remains a low priority and can be sequenced after installing PFAS-FBIX, if still requested by the Member Governments. The PFAS-FBIX treatment at the BUD WTPs is a high priority project. However, given the PFAS detection, these sites rise in priority for treatment due to the need to meet the upcoming PFAS regulatory requirements.

BENCH SCALE TESTING

The objective of bench testing was to test the most promising treatment technologies for PFAS at the sites identified. Bench scale testing was completed for the three sites identified for PFAS treatment: BUD-5 WTP (BUD-2, 4, 6 online during sampling), BUD-7 WTP, and the RSWTP.

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Bench Scale Testing Objectives Water samples for the bench-testing were collected from the three sites discussed above: BUD-5 WTP, BUD-7 WTP, and the RSWTP. Bench-scale treatability testing for PFAS was conducted at Carollo’s Water Applied Research Center (Water ARC®). The PFAS samples were analyzed at an external laboratory (Pace Analytical), as well as selected duplicate samples for PFAS analysis at Tampa Bay Water’s in-house laboratory. Other pertinent and selected water quality analyses were performed at Water ARC® and at an external certified laboratory.

Rapid small-scale column tests (RSSCT) and SIX bench-testing were performed to provide an expedited evaluation of the GAC and IX technologies being considered as alternatives for meeting Tampa Bay Water’s PFAS treatment goals. The key objectives of bench scale tests were to:

1. Inform PFAS treatment technology selection.

2. Determine critical design criteria.

3. Evaluate media use rates to estimate O&M costs associated with media changeout.

Appendices A through C contain additional bench-testing data.

Rapid Small-Scale Column Tests (RSSCT) RSSCTs are used to simulate breakthrough curves of adsorptive media. By scaling down the media size, breakthroughs can be observed in the order of days rather than months. This testing analyzed four RSSCT designs summarized in Table 4. RSSCTs are designed to indicate full-scale conditions as best as possible, but actual full-scale media service life will differ from RSSCT results due to blending of treated effluent from various adsorbers and lower flow rate or longer empty bed contact times (EBCT) (i.e., operational flowrate is lower than design capacity).

RSSCT 1 and 2: For groundwater, FBIX vessel treatment was simulated. Two RSSCT columns with Purolite PFA694E IX media (designed and targeted for PFAS treatment) were tested at bench scale for BUD-7 WTP and BUD-5 WTP. The Purolite PFA694E media is a standard for PFAS treatment and has a good track record in terms of PFAS treatment performance in groundwater sources with similar water quality. Designs targeted 2 to 3 min EBCT and loading rates of 10 to 12 gallons per minute per square foot (gpm/ft2), as are typical for PFAS adsorption.

RSSCT 3: Due to the low PFAS concentrations observed at the RSWTP to date, this surface water RSSCT used GAC media to test/ simulate a ‘GAC cap’ scenario whereby existing filter GAC media can be kept in an adsorptive state under normal filter operation and replaced at breakthrough. Media, loading rate, and EBCT were designed to match existing plant filters. It should be noted that this alternate used water from the existing WTP, and this alternative does not reflect SIX pretreatment.

RSSCT 4: A surface water RSSCT simulating, post-filter GAC adsorber for PFAS adsorption at the end of the treatment train (post-filtration and pre-chlorination) at the RSWTP. Calgon F400 GAC is a standard GAC media for PFAS treatment and has a good track record in PFAS treatment applications.

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Table 4 RSSCT Design Overview

Parameter Units RSSCT 1 RSSCT 2 RSSCT 3 RSSCT 4 Source Feed Water BUD-5 WTP

(Well 2/4/6 online)

BUD-7 WTP RSWTP

Post-Ozonation Water(1)

RSWTP

Post-Filtration Water(2)

Media -- Purolite PFA694E Purolite

PFA694E

Calgon F816 Calgon F400

Type -- IX IX Existing GAC GAC Diffusivity Factor, X(3) -- 1 1 0.25 0.25 Full-Scale IX or GAC Adsorber Design Empty Bed Contact Time minutes 2.8 2.3 8.2 10 Hydraulic Loading Rate gpm/ft2 10 12.2 3.65 6 RSSCT Column Design Upper Sieve Size (Large Scale) mesh 100 100 100 100 Lower Sieve Size (Large Scale) mesh 200 200 200 200 Column ID inches 3/16 3/16 3/16 3/16 Column Diameter mm 4.76 4.76 4.76 4.76 Hydraulic Loading Rate gpm/ft2 10 12.2 3.65 6 Volumetric Flow Rate mL/min 7.3 8.9 2.6 4.4 Scaling Factor(4) -- 6.12 6.12 15.89 8.48 Empty Bed Contact Time minutes 0.07 0.06 0.06 0.24 Duration BVs 300,000 350,000 100,000 80,000 Simulated Service Life at Full Scale days 583 559 569 556

Abbreviations: BV – bed volume; mL/min – milliliters per minute; mm – millimeters Notes:

(1) GAC design to match existing filter design.

(2) Finished water pre-chlorination.

(3) Diffusivity factor (DF) of 0.25 is used for GAC RSSCT, DF of 1 is used for IX.

(4) Ratio between unground and ground media sizes used in RSSCT.

Table 5 Analytical Methods Tested for RSSCTs

Analyte Unit Method PFAS ng/L EPA 533 TOC mg/L EPA 415.3 UVT254nm abs cm-1 Spectrophotometer Nitrate mg/L Method 10206 Dimethylphenol

Abbreviations: abs cm-1 - absorbance per centimeter; UVT - ultraviolet transmittance

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SIX Jar Testing The SIX process was identified as one of the treatment alternatives to address high TOC in the raw surface water supply at the RSWTP in the RWQS. Previous testing with similar surface water sources has demonstrated some PFAS removal with the SIX process, with performance highly dependent on the water quality. As such, SIX jar testing was conducted on the RSWTP raw water to understand the SIX treatment performance in TOC and PFAS removal.

Three series of jar tests were conducted following the details outlined in Table 6. Two different regenerant concentrations were tested; generally, higher regenerant concentrations yield higher removals, but come at higher O&M costs associated with chemical use and might also result in design parameters outside of the normal ranges of the SIX process. The resin tested was Lanxess S5128 strong base anion (SBA) resin;

this resin has typically been used in all full-scale SIX installations to date. Two resin doses were tested:

20 milliliters per liter (mL/L) and 30 mL/L. The resin used was ‘seasoned resin’ from a previous pilot study testing surface water of very similar water quality. Virgin resin was avoided for bench scale testing as it often yields unrealistic, overinflated results. Bench-scale tests were run with a 30-minute SIX contact time.

Multiple SIX treatment/ regeneration cycles were performed to simulate steady state performance. In addition to PFAS and TOC, additional anions were measured to better understand the impact on downstream processes (Table 7).

Table 6 Summary of SIX Jar Test on RSWTP Raw Water

Series Resin Dose (mL/L) Regenerant Concentration (g/L NaCl)

# of Regeneration Cycles Data Collected

1 20 20 25 Every 5 cycles; 5 total 2 20 30 25 Every 5 cycles; 5 total 3 30 30 25 Every 5 cycles; 5 total

Table 7 Analytes Tested During SIX Jar Testing

Analyte Unit Method PFAS ng/L EPA 533 TOC mg/L EPA 415.3 UVT254nm cm-1 Spectrophotometer Color C.U. Platinum-Cobalt 8025 Bromide µg/L EPA 300.0 Alkalinity mg/L as CaCO₃ Colorimetric 10280 Sulfate mg/L Turbidimetric 10227 Chloride mg/L Mercuric Thiocyanate 10291

Abbreviations: µg/L – micrograms per liter; CaCO₃ – calcium carbonate; cm – centimeter; C.U. – color unit; g/L – grams per liter;

NaCl – sodium chloride

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Bench-Scale Testing Results

Sample Baseline Water Quality Water for bench testing was collected by Tampa Bay Water and Carollo on August 20, 2024. Sample locations included RSWTP raw water, ozonated effluent, filtered effluent, BUD-7 WTP raw water, and BUD-5 WTP raw water.

Samples were collected and shipped to Water ARC® for testing. Baseline water quality was characterized, and results are summarized in Table 8 through Table 11. As anticipated, the raw surface water contains a high concentration of TOC (25.7 mg/L) (Figure 11). Note that these samples were collected during flood conditions following Hurricane Debby and consisted of 100 percent TBC lower pool. Of the samples collected, not all were in exceedance of the PFAS MCL. PFAS exceedances of the samples collected are summarized in Table 12.

Figure 11 RSWTP Raw Water Sample (8/20/2024, TOC of 25.7 mg/L)

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Table 8 RSWTP Raw Water Quality

Parameter Units Result pH S.U. 7.24 Conductivity µS/cm 145 Turbidity NTU 3.4 UV254 abs cm-1 1.2 True Color C.U. 224 Apparent Color C.U. 417 Zeta potential mV -11.5 Total Hardness mg/L as CaCO₃ 65 Total Dissolved Solids mg/L 180 Alkalinity mg/L as CaCO₃ 61 TOC mg/L 25.7 Phosphate mg/L 0.2 Chloride mg/L 17.4 Sulfate mg/L 28 Bromide µg/L 54 Fluoride mg/L 0.2 Nitrate mg/L - NO3-N 1.1

Abbreviations: µS/cm – microsiemens per centimeter; mV – millivolts; NTU – nephelometric turbidity units; S.U. – standard units;

C.U. – color units

Table 9 RSWTP Sample PFAS (PFAS method EPA 533 by Pace Analytical)

Parameter Units Raw Water Ozonated Effluent Filtered Effluent MCL PFOS ng/L 6.6 4.8 3.9 4.0 PFOA ng/L 4.5 4.4 3.1 4.0 PFBS ng/L 4.8 4.2 4.2 n/a HFPO-DA ng/L <1.0 <1.0 <1.0 10 PFHxS ng/L 3.1 2.2 1.7 10 PFNA ng/L < 1.0 <1.0 <1.0 10 TOC mg/L 25.7 4.6 3 n/a

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Figure 12 RSWTP Filtered Effluent Sample (8/20/2024)

Table 10 BUD Well Sample Results

Parameter Units BUD-7 WTP BUD-5 WTP MCL PFOS ng/L 12.0 6.4 4.0 PFOA ng/L 7.7 2.4 4.0 PFBS ng/L 9.8 4.8 n/a HFPO-DA ng/L <1.0 <1.0 10 PFHxS ng/L 4.0 3.3 10 PFNA ng/L <1.0 <1.0 10 TOC mg/L 0.45 1.0 n/a Nitrate mg/L as N 2.9 1.1 10

When BUD-5 WTP was sampled, relative individual well flows were as described in Table 11. Note that BUD-5R was not online at the time of sampling. Recent flow data from July 1, 2023, through August 1, 2024, indicate that this sample was relatively representative of the past year. However, BUD-4 flow was slightly underrepresented, and from the data collected to date, has the highest PFAS concentrations.

Bringing BUD-5R online will change the blended flow water quality, especially if PFAS concentrations are significantly different from the BUD-2, 4, and 6.

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Table 11 BUD-5 WTP Flow Distribution During Sampling Event

BUD Well No. Sampled Flowrate (mgd)

Fraction of Blend 2023-2024 Average Flow (mgd)

2023-2024 Average Fraction of Blend

2 1.0 38% 1.97 47% 4 1.0 38% 1.40 33% 6 0.65 24% 0.86 20%

5R OFFLINE 0% OFFLINE 0%

Given the water quality data collected, Tampa Bay Water does not need to remove significant fractions of the PFAS detected to meet the regulatory limits.

Table 12 PFAS MCL Exceedances in Samples Collected 8/20/24

Location PFOS PFOA RSWTP Raw Water X X RSWTP Ozonated Water X X RSWTP Filtered Water

BUD-5 WTP X

BUD-7 WTP X X

RSSCT Results

BUD-5 WTP

Treated PFOS remained non-detect in the RSSCT column effluent throughout the test (Figure 13). At the final data point (588 days), PFOA broke through, reaching 71 percent of the influent concentration (2.4 ng/L). In contrast, TOC broke through much earlier than PFOA, with a 100 percent breakthrough achieved between approximately 80 and 130 days of operation. It is clear from this data that PFOA breaks through faster than PFOS will therefore drive resin changeout but is also below the MCL in the feed. From this data, it is reasonable to expect this resin to last at least 588 days, or 1.6 years before needing to be replaced. No nitrate removal was observed in either of the BUD WTP RSSCTs, as expected. Nitrate control will require additional treatment to meet the current goal of 0.4 mg/L as N.

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Note: Open circles indicate non-detect results and correspond to Lab MDLs.

Figure 13 PFOA, PFOS, TOC, and Nitrate Breakthrough Curves from FBIX RSSCT Column at BUD-5 WTP

BUD-7 WTP

BUD-7 WTP water quality is different from BUD-5 WTP in that it has higher PFAS but lower TOC (0.45 mg/L at BUD-7 WTP). The lower TOC allowed for more removal of PFAS mass over time, likely due to the lack of shielding or fouling of the resin sites; PFOA and PFOS remained non-detect until the last data point observed some…