Maintaining Stage 2 DBP Compliance at Three Small Systems in
Maintaining Stage 2 DBP Compliance at Three Small Systems in Orange County, NY Bob Raczko, P.E. United Water 2015 NJAWWA Annual Conference 1 Overview of Presentation Background on UWNY South County Systems Water Treatment Plants: – Blue Lake (BL) – Indian Kill (IK) – Sterling Lake (SL) Distribution Systems DBP Issues Optimize WTPs for Organics Removal/DBP Control Blue Lake and Indian Kill WTPs Sterling Lake WTP Stage 2 DBP Results Conclusions/Future Work 2015 NJAWWA Annual Conference 2 Background UWNY acquired South County water and wastewater systems in 2004 Systems are not interconnected Systems are in Orange County, west of Rockland County (UWNY main service area) Until late 1990’s area slated for major development (Sterling Forest) NY/NJ intervened and acquired land for preservation by PIPC Watersheds for the WTPs are fairly well protected 2015 NJAWWA Annual Conference 3 2015 NJAWWA Annual Conference 4 South County Service Areas Water Treatment Plants Blue Lake and Indian Kill: – 50 years old, 450 gpm conventional WTPs: PACl coagulation, flocculation, sedimentation, filtration, hypochlorite, soda ash, corrosion inhibitor – Raw water quality: – Low alkalinity (BL~10 mg/L, IK~30 mg/L) – Low turbidity (<1 – 3 ntu) – Moderate TOC (3-6 mg/L), UV254 (0.09-0.19 cm-1) – Originally used alum and soda ash for coagulation; switched to PACl when UWNY acquired systems Sterling Lake: – Unfiltered supply until 2006 – Lost filtration waiver based on raw water quality (turbidity) – In 2006 installed 75 gpm Zenon membrane system (3 @ 25 gpm) All three WTPs operate about 6-8 hr/day, to fill distribution storage tanks. During low demand, may operate every other day 2015 NJAWWA Annual Conference 5 Distribution Systems Large storage tanks (100,000 – 250,000 gallons) in system; originally designed for larger Sterling Forest development Many dead ends Long detention time, high water age Difficulty maintaining chlorine residual Practice flushing to help maintain chlorine residual and address water quality complaints 2015 NJAWWA Annual Conference 6 DBP Issues Stage 2 DBP Regulations: – – – – Based on Locational Running Annual Average (LRAA): THM/HAA: 80/60 Each site must meet the 80/60 LRAA New Stage 2 DBP sampling sites – “worst case” for THM and HAA Stage 2 DBPs in effect for SC WTPs starting October 2013 Based on Stage 1 DBP results, appeared SC WTPs would have difficulties meeting Stage 2 DBP regs: – – – – Haworth Lab tracked LRAA using Stage 1 DBP data (since 2008) Blue Lake had a Stage 1 DBP violation (Nov 2012 THMs unusually high and suspect) Sterling Lake MRT THMs ranged from 76 - 110 ug/L in August 2011 – 2013 Sterling Lake is a very small system; Stage 2 DBP compliance would be determined based on one annual sample event starting in August 2014 BL and IK meet TOC removal requirements (35-45% based on raw water TOC) SL WTP does not remove TOC (not required) 2015 NJAWWA Annual Conference 7 Optimize WTPs for Organics Removal/DBP Control Track raw and filter effluent TOC, UV254 over time: – Identify seasonal variations – Track plant performance Conduct jar tests to evaluate TOC, UV254 and SDS DBP formation: – Coagulant dosage – Alternate coagulants – Powdered Activated Carbon (PAC) addition UV254 is a useful surrogate for DBP formation: – Subset of TOC – Measure organics that have C=C bonds (double bonds) – Represents fraction of organic matter that tends to form DBPs (chlorine breaks double bonds and forms DBPs) – Easy to measure: – Filter through 0.45um filter – Measure using spectrophotometer that has UV lamp 2015 NJAWWA Annual Conference 8 Blue Lake WTP - TOC, UV254 2015 NJAWWA Annual Conference 9 Indian Kill WTP - TOC, UV254 2015 NJAWWA Annual Conference 10 Jar Testing – Blue Lake WTP Evaluated: – Existing PACl (Coyne 900s – 11% aluminum) @ 35 – 65mg/L (plant @ 35 mg/L) – Letchworth WTP PACl (Coyne 950s – 12.5% aluminum) @ 30 - 50 mg/L: – Excellent organics removal – Faster floc formation; settles and filters well – PAC addition (10 mg/L) Results: – Improved performance with 950s: – Need 65 mg/L 900s vs 40-50 mg/L 950s for same UV254 – Up to 40% SDS THM reduction with 950s @ 50 mg/L vs 900s at 35 mg/L – PAC had slight improvement in UV254 and SDS THM; not worth additional cost and operational requirements 2015 NJAWWA Annual Conference 11 BLWTP SDS THMs - Jar Tests 2/20/13 2015 NJAWWA Annual Conference 12 Sterling Lake WTP Need to remove organics (TOC, UV254) GAC – too expensive (capex, opex) PAC – concerned about impact on backwash discharge (to stream) PACl – could add ahead of former chlorine contact tanks and settle out Conducted jar tests using 950s: – Optimum ~ 15 mg/L for settling – Organics removal: – TOC: 25% vs 14% in existing plant – UV254: 50% vs 0% in existing plant – SDS DBP Testing: – Significantly lower chlorine demand with 15 mg/L PACl – Up to 40% reduction in THMs – Up to 60% reduction in HAAs Sampled “shadow” DBP sites (near Stage 2 sites) to monitor DBPs 2015 NJAWWA Annual Conference 13 Sterling Lake WTP 2015 NJAWWA Annual Conference 14 Sterling Lake Jar Test - SDS Free Chlorine Residual 2015 NJAWWA Annual Conference 15 Sterling Lake Jar Test - SDS THMs 2015 NJAWWA Annual Conference 16 Sterling Lake Jar Test - SDS HAAs 2015 NJAWWA Annual Conference 17 Stage 2 DBP Results Switched from 900s to 950s at BL and IK WTPS Began adding 950s at SL WTP Blue Lake: – August (2011 – 2013) THMs: – August 2014 THMs: – August 2014 HAAs: 87 – 129 ug/L 51 ug/L 47 ug/L LRAA: LRAA: 47 ug/L 36 ug/L Indian Kill: – – – – August (2011 – 2013) THMs: 73 – 125 ug/L August 2014 THMs: 66 ug/L LRAA: 62 ug/L August 2014 HAAs 64 ug/L LRAA: 52 ug/L August 2014 HAA higher than expected (higher TOC, UV254?) – may need to increase PACl dosage Sterling Lake: – August (2011-2013) THMs: – August 2014 THMs: – August 2014 HAAs: 2015 NJAWWA Annual Conference 18 76 – 110 ug/L 44 ug/L = LRAA 23 ug/L = LRAA Conclusions/Future Work UV254 can be a good surrogate for evaluating strategies for reducing DBPs; need to measure before oxidant addition (e.g., chlorine) Jar testing is a useful tool for evaluating treatment strategies: coagulant dosage, type, PAC addition and pH of coagulation For the South County WTPs: Continue to track raw and filtered TOC and UV254 Conduct jar tests to evaluate coagulant dosage and/or type, especially when water quality changes Continue to look at ways to improve turnover in the distribution system (flushing, exercising tanks) and look at tank cleaning Continue to monitor “shadow” DBP sites for SL (near Stage 2 sites) 2015 NJAWWA Annual Conference 19 Contact Information Bob Raczko [email protected] 201-986-4990 2015 NJAWWA Annual Conference 20 Thank You! 2015 NJAWWA Annual Conference 21
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