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San Angelo City Council November 6, 2012 Hickory Update
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San Angelo City Council November 6, 2012 Hickory Update

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  • Cement with rubberWell 7 how big was the split (3 inch crack in casing).P
  • Cement with rubberWell 7 how big was the split (3 inch crack in casing).P
  • To meet DBP regulations the City currently adds chlorine and ammonia simultaneously after coagulation. Conventional wisdom is that chloramines form minimal TTHMs and that HAAs (mostly dihalogenated species) are formed. Here we see significant TTHM formation from chloramine disinfection. Another interesting observation was the continued TTHM formation within the distribution system. So what is the cause of the elevated DBP formation. Most probably the elevated bromide concentration.
  • The City of San angelo gets its water from predominately two sources – O.H. Ivie and the Concho River. Due to increasing pressure on existing surface water supplies they are currently looking at adding a new groundwater source. Note the very high bromide concentrations – especially in their current water sources. These are very high.
  • But the most interesting observation was the significant increase in TTHM formation after chloramine formation. Typically we see little additional TTHM formation after chloramines are formed. This atypical increase is most likely due to the high bromide concentration in the water.
  • Transcript

    • 1. Agenda1. Progress Update a. Well Field Piping b. Transmission Main c. Booster Pump Station & Well Field d. Treatment2. THM Compliance Strategies: Challenges & Solutions3. Questions & Discussion 2
    • 2. Well Field Piping CurrentStatus: Construction is 100% complete Contract close-out underway with the TWDB 3
    • 3. Transmission Main NTP January 23, 2012 Substantial completion July 16, 2013 (540 days) Final completion September 14, 2013 (600 days) Current status: Construction is approximately 45% Complete 4
    • 4. Progress as of Oct. 29, 2012 5
    • 5. Progress Summary Work progressing at both lay headings Over 28 miles installed Slightly behind overall schedule, but catching up and getting closer to planned schedule Valves and appurtenance work ongoing with dig/lay/bury 6
    • 6. Sta. 2624+00 looking west (Osburncropfield) 7
    • 7. Sta. 2624+00 looking east (note the solidrock) 8
    • 8. Dig, Lay Bury
    • 9. Expect utilities along the way (gas, etc)…. 10
    • 10. Booster Pump Station & Well Field NTP June 18, 2012 Substantial completion June 18, 2013 (365 days) Final Completion July 17, 2013 (395 Days) 11
    • 11. Progress Summary On schedule Access road complete except for BCV areas Booster pumps and well pumps in fabrication Booster pump cans on site Cleaning and video of wells nearly complete 12
    • 12. Excavation for meter vault 1 13
    • 13. Hickory Wells 1-9 Background Wells drilled in the 1970s Potential obstructions or items identified by the initial video survey at some wells. TCEQ required cleaning of the well casings at each well along with removal of debris or obstructions noted in the initial video survey followed by a new video survey to confirm the condition of the wells. 14
    • 14. Current status Cleaning and video complete for wells 1, 3, and 8. Casing in good condition. Cleaning work ongoing of wells 2, 5, 6, and 9. 15
    • 15. Current status (Continued) Well 4 known obstruction cleared only to encounter another obstruction (rubber plug). In process of evaluating options to remove the second obstruction. Well 7 initial cleaning complete, video revealed a split in the casing at 65 feet depth. Proposed repair is press or “swage” a sleeve inside the casing. 16
    • 16. Well brush fabrication 17
    • 17. Brushing and cleaning of well 18
    • 18. Well purge 19
    • 19. Well 4 obstruction chunk 20
    • 20. Groundwater Treatment Plant Design Procurement documents • Select radium removal system supplier • Complete • Advertise November 2012 Expedited Design schedule • Bid plans and specs – March 2013 • Construction start – June 2013 (pending TCEQ & TWDB approval and council award for bids) 21
    • 21. Visited three radium removalgroundwater treatment facilities  Vineland, NJ • In service since 2006; retrofitted in 2011  Upper Deerfield, NJ • In service since 2009  Aqua NJ Southern Division • In service since 2008
    • 22. Radium Removal System Site Visits 23
    • 23. Radium Removal System Site Visits 24
    • 24. THM Compliance Strategies: Challenges and Solutions November 6, 2012 City of San Angelo Council Meeting P. Greg Pope Ph.D., P.E. Carollo Engineers, Inc.
    • 25. What are THMs? Cl2 + Natural Organic Matter + Bromide  Halogenated Organics (THMs) THMs Disinfectant 27
    • 26. Why do we care about THMS? THMs (Trihalomethanes) are a family of four chemicals (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) that are regulated by the USEPA EPA maximum contaminant level = 80 µg/L Some people who drink water containing THMs in excess of the MCL over many years may experience health problems 28
    • 27. Several Factors Impact THMFormation Source water quality • natural organic matter (NOM) • bromide pH Water age Disinfectant type Disinfectant concentration 29
    • 28. How Can THM Formation be Controlled? Cl2 + NOM + Bromide  THMs Alternate Disinfectants•Chloramines 30
    • 29. How Can THM Formation be Controlled? Cl2 + NOM + Bromide  THMs Alternate Disinfectants Remove/Reduce•Chloramines NOM Reactivity •Reverse Osmosis •GAC •pH Control •Ozone •Chlorine Dioxide 31
    • 30. How Can THM Formation be Controlled? Cl2 + NOM + Bromide  THMs Alternate Disinfectants Remove/Reduce THM•Chloramines NOM Reactivity Removal/Degradation •Reverse Osmosis •Biological Filtration •GAC •Aeration •pH Control •GAC •Ozone •Chlorine Dioxide 32
    • 31. To limit DBP formation the COSA Useschloramines for disinfection 100 Water Plant 90 Mathis Field 80 70 60 TTHM (µg/L) 50 40 30 20 10 0 Jun Aug Sep Nov Jan Feb Apr Jun Jul
    • 32. High bromide source waters pose a challenge to utilities that use chloraminesParameter O.H. Ivie Concho Hickory Reservoir RiverBromide (mg/L) 1.6 0.89 0.39pH 7.9 8.1 7.5TOC (mg/L) 4.8 7.6 0.2TDS (mg/L) 1350 950 480 34
    • 33. Blending Treated Groundwater with TreatedSurface Water Reduced THM Formation 180 160 2 day THM formation 140 120 TTHM Formation (µg/L) 100 80 60 40 20 0 75% TSW/ 50% TSW/ 25% TSW/ 100% TGW 100% TSW 25% TGW 50% TGW 75% TGW
    • 34. Current THM Formation 90 80 70 60 TTHMs (µg/L) 50 40 pH 7.5 30 20 10 0 30 minutes 5 days 36
    • 35. Optimizing pH Decreased THM formation 90 80 70 60 TTHMs (µg/L) 50 pH 7.5 40 pH 8.3 30 20 10 0 30 minutes 5 days 37
    • 36. Summary Strategies aimed at optimizing chloramine formation conditions may reduce THM formation. Bench –studies indicated that: • Blending the source water with a lower bromide, less reactive groundwater decreased DBP formation. • Disinfection at elevated pH (8.3 vs. 7.5) reduced THM formation. 38

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