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DBP Control Strategies: Source Water, Treatment, and Distribution System

DBP Control Strategies: Source Water, Treatment, and Distribution System. Philip A. Tangorra NYC WATERSHED / TIFFT SYMPOSIUM September 17, 2013 West Point, NY. Source water characteristics Traditional Treatment Disinfection Distribution. Spatial/Temporal levels of TTHM that are “high”.

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DBP Control Strategies: Source Water, Treatment, and Distribution System

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  1. DBP Control Strategies: Source Water, Treatment, and Distribution System Philip A. Tangorra NYC WATERSHED / TIFFT SYMPOSIUM September 17, 2013 West Point, NY

  2. Source water characteristics Traditional Treatment Disinfection Distribution Spatial/Temporal levels of TTHM that are “high”. Long Term exposures - Large dataset on carcinogenicity of THM. Stage 2 Compliance TOC & DBPs

  3. TTHM REGULATIONS • 1979 - Total Trihalomethanes Rule • 0.100 mg/L MCL • 1998 - Stage 1 D/DBP Rule • 0.080 mg/L RAA MCL for TTHM • 0.060 mg/L RAA MCL for HAA5 • 2006 - Stage 2 D/DBP Rule • 0.080 mg/L LRAA MCL for TTHM • 0.060 mg/L LRAA MCL for HAA5

  4. History of Recent MVWA Studies NitrificationControl Study Cl-NH3 Conversion & Pipe Loop GAC Pilot and Full Scale Demos DBPControl Study TANCS Project 1999 2001 2002 2003 2004 2005 2006 2007 2008 2010 2012 Promulgation of Stage 2 D/DBP and LT2ESWTR Stage 2 D/DBP Rule Proposed Stage 1 D/DBP Compliance Stage 2 D/DBP Compliance

  5. MVWA Studies for Stage 2 D/DBP Rule Compliance • DBP Control Options Study – 2001 • TANCS study – 2003 • Nitrification Control Study – 2004 • Chloramines System Pre-Design – 2005 • Chloramines Conversion Master Plan – 2005 • Corrosion Pipe Loop Testing – 2006 • GAC Pilot scale testing – 2007 • GAC Demonstration Scale Testing – 2008 • Ongoing • Alternative coagulants • DS corrosion chemistry modifications • GAC Pilot Scale Testing

  6. GAC Implementation • Complete media change out (63”) • Timing • Operational Issues • Flow/Demand • Raw Water Quality • Backwash frequency • Staffing • Logistics • Facilities • Deliveries • Noise • 2011 – Full scale comparison of 8*30 GAC • Wood • Virgin Bituminous • Reactivated Bituminous • 2012 - 8*20 Lignite • 2013 - 8*20 Lignite + Underdrain Rehab ANNUAL BUDGET $1,000,000

  7. MVWA Studies for Stage 2 D/DBP Rule Compliance • DBP Control Options Study – 2001 • TANCS study – 2003 • Nitrification Control Study – 2004 • Chloramines System Pre-Design – 2005 • Chloramines Conversion Master Plan – 2005 • Corrosion Pipe Loop Testing – 2006 • GAC Pilot scale testing – 2007 • GAC Demonstration Scale Testing – 2008 • Ongoing • Alternative coagulants • DS corrosion chemistry modifications • GAC Pilot Scale Testing

  8. Ongoing • Alternative coagulants • DS corrosion chemistry modifications • GAC Pilot Scale Testing

  9. Alternative Coagulants

  10. Distribution System • Recent DS Conditions • pH 9.4 • Alkalinity ~40mg CaCO3/L • PO4 0mg/L • Optimized Corrosion • UFWR offline • Experimental (CDM Smith) • pH 7.8 • Alkalinity ~40mg CaCO3/L • PO4 0.8 mg/L • Cost Savings? • TTHM Reduction?

  11. Distribution Considerations • Unidirectional Flush • Timeframe • Lime / Soda Ash / Bicarb • Pb/Cu compliance • TTHM reductions

  12. GAC Options • Siemens Coconut shell • CalgonCarbsorb 820 • Factors • Cost • RSSCT and pilot scale testing • EBCT at 20MGD • 63” GAC = 14.5 min • 55” GAC = 12.7 min • Regeneration??

  13. In Situ GAC Regeneration • Dr. Paul Westerhoff at Arizona State University has developed a technique that may allow for in situ GAC regeneration • Iron nanoparticles (<100 nm) are combined with H2O2 to form hydroxyl radicals, which can oxidize adsorbed organic compounds, converting them to CO2 and H2O

  14. Objectives • Determine if the in situ regeneration technique is suitable for recovering TOC adsorption capacity • Evaluate the effectiveness of the method under “more realistic” conditions • Commercially available GAC • Full size GAC grains • Typical (full scale) GAC bed depth

  15. Iron Nanoparticle Production • Commercial grade FeCl3 resulted in larger NPs than those produced from reagent grade FeCl3 (200 nm vs. 80-90 nm) • Methylene blue dye oxidation tests were used to gauge NP reactivity • Multiple batches of NPs appeared non-reactive • It was discovered that dye oxidation only occurred in a pH range of 2.6-2.8

  16. Methylene Blue Oxidation Tests

  17. Pilot Scale Filter Columns

  18. Pilot Scale Recirculation System

  19. Regeneration Results • Wood-based GAC - • Three 1-hour regeneration cycles • No measureable change in effluent TOC • Lignite-based GAC • One 1-hour regeneration cycle • No measureable change in effluent TOC

  20. Regeneration Results • Coconut-based GAC • Three 1-hour regeneration cycles • Effluent TOC reduced after each cycle • First round: 1.25 mg/L →0.85 mg/L • Second round: 0.65 mg/L • Third round: 0.55 mg/L

  21. Effluent TOC Profile – Coconut GAC

  22. Regeneration Considerations • Reagent v. Commercial FeCl3 • pH control • Peroxide measurement • Biofilm?

  23. Summary • In situ regeneration using Fe NPs and peroxide has been shown to be effective for recovering phenol adsorption capacity in bench scale tests • Pilot scale testing has demonstrated that recovering NOM adsorption capacity in full size GAC grains is possible • Achieving greater recovery may require further modifications, or simply more time

  24. THE LAST SLIDE • Thanks • Connie Schreppel, PhD • MVWA Director of Water Quality • Kim Hoffman • CDM Smith • Kirk Nowack, PhD - Arcadis • Questions?

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