Practical OBG PRESENTS: Aspects of Implementing a 5-MGD Treatment System to Remove PFOA and PFOS from a Public Drinking Water Supply

Transcription

1 OBG PRESENTS: Practical OBG PRESENTS: Aspects of Implementing a 5-MGD Treatment System to Remove PFOA and PFOS from a Public Drinking Water Supply PJ Crow, P.E. WaterJAM 2018, September 12 th, 2018

2 OUTLINE Background Treatment Options Alternative Evaluation Implementation Strategy Project Schedule System Performance Conclusions 2

3 Service Area Source Capacity 6,000 customers Groundwater under the influence with >400 mg/l hardness Kilmer Springs 4 MGD Big Springs 5 MGD Treatment Distribution Direct filtration (anthracite/sand) 2 to 24 mains 2 pressure zones 4.0-MG storage 3

4 Problem Statement Perfluorooctanoic acid (PFOA) and Perfluorooctane sulfonate (PFOS) discovered at levels twice the lifetime health advisory of 70 ng/l in Big Springs well May 19, 2016 City s 5 MGD water treatment system shut down by West Virginia Bureau of Public Health City needed Big Springs supply solution required on an EXPEDITED schedule 4

5 Poly- and Perfluoroalkyl Substances (PFAS) What are PFAS? Large class of compounds (1000s) Polyfluorinated one or more C in tail not bonded with F Perfluorinated all C in tail bonded with F Used for many years Wide range of consumer products Sources Class B Firefighting Foam Fume Suppressants Landfills and Landfill Leachate Industrial Coatings and Etchings Food Packaging Water/Oil/Stain Resistant Textiles and Clothing Personal Care Products 5

6 Perfluoroalkyl Acids (PFAAs) The Current Focus PFSAs Perfluorosulfonic acids Long chain PFHxS (6 carbons) Includes PFOS PFCAs Perfluorocarboxylic acids Long chain PFOA (8 carbons) Long-chain PFAAs more toxic and bioaccumulative C4 Butane C5 Pentane C6 Hexane C7 Heptane C8 Octane C9 Nonane C10 Decane C11 Unodecane C12 Dodecane C13 Tridecane C14 Tetradecane 6

7 Highly Soluble in Water Low Volatility Extremely Stable Compounds Properties of PFOA and PFOS Migrates rapidly in groundwater Forms long, dilute plumes Difficult to extract from groundwater Resistant to degradation Persistent Bioaccumulates Half lives in human serum 3 to 5 years 7

8 No EPA enforceable standards Certain PFAAs on Contaminant Candidate List (CCL) since 1999 Regulatory Framework EPA Method 537 promulgated in 2009 Provisional health advisories issued in ng/l for PFOS, 400 ng/l for PFOA Six PFAAs included in UCMR3 monitoring Lifetime health advisories issued May ng/l PFOS and PFOA (individually and combined) 8

9 Treatment Options Reverse Osmosis/ Nanofiltration Activated Carbon Ion Exchange Advanced Oxidation Processes 9

10 Treatment Options Reverse Osmosis/ Nanofiltration Activated Carbon Ion Exchange Advanced Oxidation Processes Good removal rates Susceptible fouling Pretreatment may be required High cost 10

11 Treatment Options Reverse Osmosis/ Nanofiltration Activated Carbon Ion Exchange Advanced Oxidation Processes Good removal rates Regenerate GAC Moderate cost 11

12 Treatment Options Reverse Osmosis/ Nanofiltration Activated Carbon Ion Exchange Advanced Oxidation Processes Good removal PFOS Pretreatment may be required Brine waste Competitive cost if regenerated onsite 12

13 Treatment Options Reverse Osmosis/ Nanofiltration Activated Carbon Ion Exchange Advanced Oxidation Processes Low removal rates Significant energy required High cost 13

14 Benchscale Testing PAC >80% removal at 1.0 MGD Full scale required impacts to filter PAC Adsorption Kinetics GAC 10 min EBCT ng/l after a year GAC Rapid Small Scale Column Test 14

15 Activated Carbon Treatment Option Incorporating into existing treatment process Consider removal effectiveness, capacity limitations and O&M costs Evaluate existing water quality for process optimization 15

16 PAC Addition Alternative Evaluation GAC Contactors Replacement of Anthracite w/ GAC Combination of Option 1 and 3 16

17 GAC Contactors Operate at WFP rated capacity Operate in series (lead/lag) Sampling taps and flow meter to track PFAA breakthrough Minimal impacts to existing process 17

18 Treatment System Schematic 18

19 Water Treatment Plant Layout Filtration Building Flocculation Basin New GAC Building Clearwell Pump House Backwash Tank 19

20 Fast Track Approach to Expedite Project Contract No. 1 Pre-Purchase of GAC Contactors (TIGG, LLC.) Alternate bids Contactor size 10 dia. vs. 12 dia. Weighted bid evaluation price and schedule Contract No. 2 Big Springs WFP GAC Upgrades (Snyder Environmental Services) 2.5 MGD vs 5 MGD alternates 20

21 May 2016 Big Spring WFP Shut Down June to December 2016 Bench Tests and City Approvals Expedited Schedule Within Rules of Public Bidding January to April 2017 Design April 2017 Pre-Purchase GAC Contactors May 2017 GAC Upgrades Contract Awarded December 2017 Partial Startup March 2018 New Plant Fully Operational 21

22 Next Steps Effectiveness of coconut shell carbon, in term in bed volumes treated before exhaustion Equipment manufacturer and City are co-funding a sampling program to monitor breakthrough at four ports in the GAC contactor Monitor frequency of backwashing, to confirm whether any pre-gac treatment may be beneficial 22

23 Plant Performance to Date Treated 165 MG since startup in December 2017 One filter backwash to date (April 2018) Sampling data taken June 27 th, 2018 (77 MG treated): Raw Water Lead Vessel Effluent PFOA (ng/l) ND PFOS (ng/l) ND Lag Vessel Effluent Appx. 8,000 bed volumes treated to date 23

24 Conclusions Expedited project schedule successful through a collaborative Team approach among the City, Contractors, and OBG Meets treatment expectations PFOA/PFOS non-detect in effluent Installation of GAC treatment units has not complicated operation at the conventional WTP 24

25 Acknowledgements City of Martinsburg, Mark Baldwin & Steve Knipe TIGG, LLC Snyder Environmental Services OBG, George Rest, PE & Narayan Venkatesan, PE 25

26 OBG PRESENTS: THERE S A WAY Thank you! pj.crow@obg.com