Maintaining Stage 2 DBP
Compliance at Three
Small Systems in Orange
County, NY
Bob Raczko, P.E.
United Water
2015 NJAWWA Annual Conference
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Overview of Presentation
 Background on UWNY South County Systems
 Water Treatment Plants:
– Blue Lake (BL)
– Indian Kill (IK)
– Sterling Lake (SL)
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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
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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
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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
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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
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DBP Issues
 Stage 2 DBP Regulations:
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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:
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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)
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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
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Blue Lake WTP - TOC, UV254
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Indian Kill WTP - TOC, UV254
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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
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BLWTP SDS THMs - Jar Tests 2/20/13
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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
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Sterling Lake WTP
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Sterling Lake Jar Test - SDS Free Chlorine Residual
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Sterling Lake Jar Test - SDS THMs
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Sterling Lake Jar Test - SDS HAAs
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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:
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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:
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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)
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Contact Information
Bob Raczko
[email protected]
201-986-4990
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Thank You!
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