ACHIEVING STAGE 2 DBPR COMPLIANCE THROUGH SYSTEM OPTIMIZATION AND EFFICIENT USE OF POST-FILTRATION GAC: A 5 YEAR CASE STUDY

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1 ACHIEVING STAGE 2 DBPR COMPLIANCE THROUGH SYSTEM OPTIMIZATION AND EFFICIENT USE OF POST-FILTRATION GAC: A 5 YEAR CASE STUDY AMANDA WILLIAMS (CO-WRITER: PETER THOMPSON JR.) WATER QUALITY SUPERVISOR PALMDALE WATER DISTRICT PALMDALE, CA 93550

2 DISTRICT BACKGROUND Located within the Antelope Valley in Los Angeles County, CA 60 miles north of the City of Los Angeles >25,000 active connections (Population >100,000) 413 miles of pipelines 17 reservoir sites 15 booster stations 7 pressure zones Distribution system storage >50 MG

3 DISTRICT BACKGROUND On average PWD produces ~6.825 billion gallons/year The District relies on ground water and treated surface water: Ground water 22 Active Wells Approximately 40% of the water produced Surface water Palmdale Lake California Aqueduct Littlerock Reservoir Treated by Leslie O. Carter Water Treatment Plant Typically MGD

4 PRELUDE Violated Stage 1 Disinfectants and Disinfection Byproducts Rule (Stage 1 DBPR) in 2 nd and 3 rd Quarters of 2003: Distribution System RAA = 85 ppb and 84 ppb respectively Tier 2 Notification Required Stage 1 DBPR compliance was regained through: Chlorine residual reduction Blending more ground water with treated surface water. Reducing detention time within the distribution system Since the 4 th Quarter of 2003, the District has maintained regulatory compliance

5 HISTORICAL DISTRIBUTION SYSTEM TTHM RAA 90 Distribution System - TTHM Running Annual Average (RAA) Total Trihalomethanes (ug/l)

6 HISTORICAL DISTRIBUTION SYSTEM TTHM RAA Distribution System - TTHM Running Annual Average (RAA) Stage 1 TTHM Violation Stage 1 DBPR: nd Quarter RAA = 85 ppb rd Quarter RAA = 84 ppb Total Trihalomethanes (ug/l)

7 HISTORICAL DISTRIBUTION SYSTEM TTHM RAA Total Trihalomethanes (ug/l) Distribution System - TTHM Running Annual Average (RAA) Stage 1 TTHM Violation Stage 1 DBPR: nd Quarter RAA = 85 ppb rd Quarter RAA = 84 ppb After violation: Implemented process controls to reduce TTHM formation within the distribution system.

8 STAGE 1 DBPR COMPLIANCE DOES NOT EQUAL STAGE 2 DBPR COMPLIANCE The Stage 2 DBPR would eliminate system wide averaging of TTHM s and replace it with Locational Running Annual Averages (LRAA). It was clear that several sites would not comply under Stage 2 DBPR. Additional treatment would be necessary in order to achieve future compliance.

9 STAGE 1 DBPR COMPLIANCE DOES NOT EQUAL STAGE 2 DBPR COMPLIANCE (PRE) WTP-GAC: Jan 03 Oct 08 Stage 1 DBPR: 16 Sites Sites influenced by chlorinated ground water have lowest TTHMs. 5 sites: < 30 ppb

10 STAGE 1 DBPR COMPLIANCE DOES NOT EQUAL STAGE 2 DBPR COMPLIANCE (PRE) WTP-GAC: Jan 03 Oct 08 Stage 1 DBPR: 16 Sites Sites influenced by chlorinated ground water have lowest TTHMs. 5 sites: < 30 ppb Some sites are blended between treated surface water and chlorinated ground water. 5 sites: ppb

11 STAGE 1 DBPR COMPLIANCE DOES NOT EQUAL STAGE 2 DBPR COMPLIANCE (PRE) WTP-GAC: Jan 03 Oct 08 Stage 1 DBPR: 16 Sites Sites influenced by chlorinated ground water have lowest TTHMs. 5 sites: < 30 ppb Some sites are blended between treated surface water and chlorinated ground water. 5 sites: ppb Sites influenced by treated surface water have highest TTHMs. 6 sites: > 80 ppb

12 GAC CHOSEN AS METHOD FOR ACHIEVING STAGE 2 DBPR COMPLIANCE 8 GAC contactors installed post-filtration cubic feet of 8x30 mesh size bituminous coal media per contactor. 15 minutes EBCT at max plant flow of 35 MGD through 7 contactors (or 5 MGD per contactor). Replace spent virgin media with fresh virgin once the adsorptive capacity for TOC removal was spent The final Plant Effluent TOC would be reduced to less than 0.9 mg/l. The cost of GAC replacement was estimated at $7,000, annually.

13 A ROUGH BEGINNING The GAC contactors were placed online in November of In 2009, the newly adopted rate structure would only support $2,000, towards GAC replacement annually. Efforts to improve efficiency took the following forms: Improved understanding of the distribution system Distribution system optimization Pilot and full scale testing of GAC GAC Operation optimization

14 UNDERSTANDING OUR DISTRIBUTION SYSTEM Since 2009, Palmdale Water District lab staff has painstakingly gathered and analyzed thousands of samples from the treatment plant, GAC process, and the distribution system.

15 UNDERSTANDING OUR DISTRIBUTION SYSTEM A GCMS was purchased to facilitate the volume of samples that staff was analyzing for TTHM. In-house analysis allows staff to quickly check operational changes against TTHM and TOC data in the plant and distribution system.

16 UNDERSTANDING OUR DISTRIBUTION SYSTEM Through careful analysis of the evolving distribution system, a new target Plant Effluent TOC was developed: The allowable Plant Effluent TOC increased from 0.9 mg/l to 1.1 mg/l. This elevation of the target TOC reduces the strain on the GAC contactors.

17 OPTIMIZING DISTRIBUTION OPERATIONS Staff sought to improve two factors within the distribution system that contributed to THMs: 1. Detention Time 2. Chlorine Residual

18 Detention times were reduced by: OPTIMIZING DETENTION TIME Abandoning Keep the Tanks Full policy. Adopting a policy of active reservoir management. Daily tank turn over. Reduced system storage targets PRV s were adjusted to allow flow from stagnant pressure zones down to higher demand pressure zones.

19 OPTIMIZING CHLORINE RESIDUAL The addition of tank mixers in reservoirs to stabilize chlorine residuals.

20 OPTIMIZING CHLORINE RESIDUAL Targeted reduction of Plant Effluent chlorine residual. Beginning in 2009, Palmdale Water District Water Treatment Plant began targeting a chlorine residual at the 6MG Clearwell to be between mg/l to ensure appropriate disinfectant and reduce TTHM formation as it enters the distribution system. Chlorine Residual (mg/l) MG Clearwell Chlorine Residual Max = 2.20 Min = 0.38 Avg = Max = 1.41 Min = 0.73 Avg = 1.03

21 OPTIMIZING CHLORINE RESIDUAL Aggressive monitoring, maintenance and control of booster chlorination to achieve lower but more consistent chlorine residuals. Chlorine Residual (mg/l) MG Clearwell Chlorine Residual

22 GAC TESTING GAC Types Bituminous Coal Coconut based Enhanced coconut Wood based Lignite GAC Mesh Sizes GAC Processing Virgin versus Reactivated

23 KEY CONCLUSIONS Bituminous coal and enhanced coconut were the best options for TOC removal. For the purpose of TOC removal, the mesh size was superior to Re-activated GAC media was as effective as virgin media and significantly less costly.

24 OPTIMIZING GAC OPERATIONS The critical advancements for the District in terms of cost reduction have come from changing operational strategies with GAC: Successful utilization of re-activated carbon. Utilizing biological removal of GAC for extended periods.

25 RE-ACTIVATED GAC MEDIA Re-activated carbon media has been in use at PWD since Re-activated carbon has provided equal to better performance than virgin media. Turn around on removal, reactivation, and replacement material has been typically 4-6 weeks. Re-activated carbon costs roughly 25 40% less than the replacement of virgin material.

26 LEVERAGING BIOLOGICAL REMOVAL Two general phases of TOC removal: Adsorptive: The initial TOC removal phase due to the physical properties of GAC media Initial plan to consider GAC spent when TOC removal < 40% Biological: The extended phase of removal due to consumption of TOC by biological activity Typically stabilizes between 30 40% TOC removal

27 100% Adsorptive vs. Biological TOC Removal 90% 80% TOC % Removal 70% 60% 50% 40% 30% 20% 10% 0% TOC Loading (lbs)

28 TOC % Removal 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Adsorptive vs. Biological TOC Removal ADSORPTIVE PHASE (TOC Loaded) 9,100 lbs Average Removal = 67% TOC Removed = 5,756 lbs TOC Loading (lbs)

29 100% 90% 80% Adsorptive vs. Biological TOC Removal ADSORPTIVE PHASE BIOLOGICAL PHASE TOC % Removal 70% 60% 50% 40% 30% 20% 10% 0% (TOC Loaded) 9,100 lbs Average Removal = 67% TOC Removed = 5,756 lbs TOC Loading (lbs) (TOC Loaded) 3,300 lbs Average Removal = 37% TOC Removed = 1,190 lbs Extends GAC Contactor life ~21%

30 LEVERAGING BIOLOGICAL REMOVAL Utilizing the two phases (adsorptive and biological) of TOC removal allow for: Precise control of Plant Effluent TOC (Target = 1.1 mg/l) Increased EBCT (empty bed contact time) More contactors online Reduced exchanges of GAC media

31 THE EFFECTS OF OPTIMIZATION AND GAC The combination of GAC and distribution system optimization brought the TTHM LRAA for each Stage 1 DBPR site below 80 ppb prior to the implementation of the Stage 2 DBPR.

32 THE EFFECTS OF OPTIMIZATION AND GAC Total Trihalomethanes (ug/l) Distribution System - TTHM Running Annual Average (RAA) Stage 1 TTHM Violation WTP-GAC online Stage 1 DBPR: nd Quarter RAA = 85 ppb rd Quarter RAA = 84 ppb After violation: Implemented process controls to reduce TTHM formation within the distribution system. November 2008: WTP-GAC online

33 THE EFFECTS OF OPTIMIZATION AND GAC Total Trihalomethanes (ug/l) Distribution System - TTHM Running Annual Average (RAA) Stage 1 TTHM Violation WTP-GAC online Stage 2 DBPR Stage 1 DBPR: nd Quarter RAA = 85 ppb rd Quarter RAA = 84 ppb After violation: Implemented process controls to reduce TTHM formation within the distribution system. November 2008: WTP-GAC online Stage 2 DBPR: Began April 1,

34 THE EFFECTS OF OPTIMIZATION AND GAC (POST) WTP-GAC: Nov 08 Dec 13 Stage 1 DBPR: 16 Sites Sites influenced by chlorinated ground water have lowest TTHMs. 10 sites: < 30 ppb

35 THE EFFECTS OF OPTIMIZATION AND GAC (POST) WTP-GAC: Nov 08 Dec 13 Stage 1 DBPR: 16 Sites Sites influenced by chlorinated ground water have lowest TTHMs. 10 sites: < 30 ppb Some sites are blended between treated surface water and chlorinated ground water. 6 sites: ppb

36 THE EFFECTS OF OPTIMIZATION AND GAC (POST) WTP-GAC: Nov 08 Dec 13 Stage 1 DBPR: 16 Sites Sites influenced by chlorinated ground water have lowest TTHMs. 10 sites: < 30 ppb Some sites are blended between treated surface water and chlorinated ground water. 6 sites: ppb Sites influenced by treated surface water have highest TTHMs. 0 sites: > 80 ppb

37 COMPLIANCE Stage 2 DBPR Sites: Apr 12 Dec 13 Stage 2 DBPR: 8 Sites Sites influenced by chlorinated ground water have lowest TTHMs. 1 sites: < 30 ppb

38 COMPLIANCE Stage 2 DBPR Sites: Apr 12 Dec 13 Stage 2 DBPR: 8 Sites Sites influenced by chlorinated ground water have lowest TTHMs. 1 sites: < 30 ppb Some sites are blended between treated surface water and chlorinated ground water. 7 sites: ppb (Max = 57 ppb) Sites influenced by treated surface water have highest TTHMs. 0 sites: > 80 ppb

39 STAGE 2 DBPR SAMPLE SITE EXAMPLES Two (2) specific examples of TTHM management through system optimization and use of GAC at the Water Treatment Plant: 1) E. Avenue T-2 2) Denise St.

40 EXAMPLE 1: E. AVENUE T E. Avenue T-2 - TTHM Locational Running Annual Average (LRAA) Total Trihalomethanes (ug/l)

41 EXAMPLE 1: E. AVENUE T E. Avenue T-2 - TTHM Locational Running Annual Average (LRAA) TTHM Averages: 2003 LRAA= 140 ppb Total Trihalomethanes (ug/l)

42 EXAMPLE 1: E. AVENUE T E. Avenue T-2 - TTHM Locational Running Annual Average (LRAA) TTHM Averages: 2003 LRAA= 140 ppb (Pre) WTP-GAC = 126 ppb Total Trihalomethanes (ug/l)

43 EXAMPLE 1: E. AVENUE T E. Avenue T-2 - TTHM Locational Running Annual Average (LRAA) TTHM Averages: 2003 LRAA= 140 ppb (Pre) WTP-GAC = 126 ppb (Post) WTP-GAC = 58 ppb Total Trihalomethanes (ug/l)

44 EXAMPLE 1: E. AVENUE T-2 Total Trihalomethanes (ug/l) E. Avenue T-2 - TTHM Locational Running Annual Average (LRAA) System Control TTHM Averages: 2003 LRAA= 140 ppb (Pre) WTP-GAC = 126 ppb (Post) WTP-GAC = 58 ppb 3 rd Quarter 2003: System optimization

45 EXAMPLE 1: E. AVENUE T-2 Total Trihalomethanes (ug/l) E. Avenue T-2 - TTHM Locational Running Annual Average (LRAA) System Control WTP-GAC online TTHM Averages: 2003 LRAA= 140 ppb (Pre) WTP-GAC = 126 ppb (Post) WTP-GAC = 58 ppb 3 rd Quarter 2003: System optimization November 2008: WTP-GAC online

46 EXAMPLE 1: E. AVENUE T-2 Total Trihalomethanes (ug/l) E. Avenue T-2 - TTHM Locational Running Annual Average (LRAA) System Control WTP-GAC online PRV Adjustment TTHM Averages: 2003 LRAA= 140 ppb (Pre) WTP-GAC = 126 ppb (Post) WTP-GAC = 58 ppb 3 rd Quarter 2003: System optimization November 2008: WTP-GAC online March 2010: PRV (32 nd St. E.) adjustment to decrease water detention time

47 EXAMPLE 1: E. AVENUE T-2 Total Trihalomethanes (ug/l) E. Avenue T-2 - TTHM Locational Running Annual Average (LRAA) System Control WTP-GAC online PRV Adjustment Stage 2 DBPR TTHM Averages: 2003 LRAA= 140 ppb (Pre) WTP-GAC = 126 ppb (Post) WTP-GAC = 58 ppb 3 rd Quarter 2003: System optimization November 2008: WTP-GAC online March 2010: PRV (32 nd St. E.) adjustment to decrease water detention time Stage 2 DBPR site: Began April 1, 2012

48 EXAMPLE 2: DENISE ST. Total Trihalomethanes (ug/l) Denise St. - TTHM Locational Running Annual Average (LRAA)

49 EXAMPLE 2: DENISE ST. Total Trihalomethanes (ug/l) Denise St. - TTHM Locational Running Annual Average (LRAA) TTHM Averages: 2003 LRAA= 148 ppb

50 EXAMPLE 2: DENISE ST. Total Trihalomethanes (ug/l) Denise St. - TTHM Locational Running Annual Average (LRAA) TTHM Averages: 2003 LRAA= 148 ppb (Pre) WTP-GAC = 121 ppb

51 EXAMPLE 2: DENISE ST. Total Trihalomethanes (ug/l) Denise St. - TTHM Locational Running Annual Average (LRAA) TTHM Averages: 2003 LRAA= 148 ppb (Pre) WTP-GAC = 121 ppb (Post) WTP-GAC = 67 ppb

52 EXAMPLE 2: DENISE ST. Total Trihalomethanes (ug/l) Denise St. - TTHM Locational Running Annual Average (LRAA) System Control TTHM Averages: 2003 LRAA= 148 ppb (Pre) WTP-GAC = 121 ppb (Post) WTP-GAC = 67 ppb 3 rd Quarter 2003: System optimization

53 EXAMPLE 2: DENISE ST. Total Trihalomethanes (ug/l) Denise St. - TTHM Locational Running Annual Average (LRAA) System Control WTP-GAC online TTHM Averages: 2003 LRAA= 148 ppb (Pre) WTP-GAC = 121 ppb (Post) WTP-GAC = 67 ppb 3 rd Quarter 2003: System optimization November 2008: WTP-GAC online

54 EXAMPLE 2: DENISE ST. Total Trihalomethanes (ug/l) Denise St. - TTHM Locational Running Annual Average (LRAA) System Control WTP-GAC online PRV adjustment TTHM Averages: 2003 LRAA= 148 ppb (Pre) WTP-GAC = 121 ppb (Post) WTP-GAC = 67 ppb 3 rd Quarter 2003: System optimization November 2008: WTP-GAC online March 2011: PRV (Avenue R-8) adjustment to decrease water detention time

55 EXAMPLE 2: DENISE ST. Total Trihalomethanes (ug/l) Denise St. - TTHM Locational Running Annual Average (LRAA) System Control WTP-GAC online PRV adjustment Stage 2 DBPR TTHM Averages: 2003 LRAA= 148 ppb (Pre) WTP-GAC = 121 ppb (Post) WTP-GAC = 67 ppb 3 rd Quarter 2003: System optimization November 2008: WTP-GAC online March 2011: PRV (Avenue R-8) adjustment to decrease water detention time Stage 2 DBPR site: Began April 1, 2012

56 CONCLUSION Stage 1 DBPR and Stage 2 DBPR Compliance Cost-effective use of GAC as a post-filter adsorber Cost reduced by 78.5% (from $7M to $1.5M annually) Key Methods: Increased target Plant Effluent TOC from 0.9 mg/l to 1.1 mg/l through distribution system optimization Utilized re-activated GAC. Maximized TOC removal through careful balancing of adsorptive phase and biological phase contactors. Removes approximately 21% more TOC per contactor

57 CURRENT DEVELOPMENTS January 2014: Localized treatment began for removal of TTHM in the longest detention time pressure zone The District reduced the highest Stage 2 DBPR sites to be among the lowest. This allowed the target plant effluent TOC level to be adjusted up; further extending the life of GAC media. June 2014: Water Quality Supervisor, Amanda Williams, developed a functional model for predicting GAC performance. This has allowed staff to make refined adjustments to GAC contactor usage and lead to more efficient use of GAC Media.

58 CURRENT DEVELOPMENTS August 2014: the District began exchanging its GAC media from 8 30 mesh size to mesh size. This will also further extend the useful life of the GAC media. Staff estimates that the current developments will save the district an additional 50% annually on GAC media replacement starting in 2016.