Optimizing Water Quality: Aeration for THM Reduction

1. Reducing THM via Aeration: A Case StudyNovember 21, 2013by Gary Williams, P.E.Jones & Henry Engineers Southeast AWWA District Meeting

2. Agenda • Location • History • Pilot • Implementation • Take Away Information

3. Location Map

4. Distribution System Map

6. Water Quality 2008

7. THM 2008

8. Water History • 1972 Water Treatment Plant, Low Head Dam, and Reservoir Constructed • 1993 Water Treatment Plant Study • 1996 Reservoir Study • 1999-2000 Water Treatment Plant Expansion $3,000,000 • 2002 Second Reservoir $2,300,000 • 2004 Water Distribution System DBP Reduction Study • 2005 Chlorine Dioxide Benchtop Study • 2005 MIEXBenchtop Study • 2006 RSSCT for GACBenchtop Study • 2008 THM Reduction via Aeration Opflow Article

9. 2008 THM Reduction via Aeration Opflow Article

10. Research • Limited Research Available for Dynamic System • One Company Marketed a System $$$$$$$$ • Air : Water Ratios (cfm : gpm) 5 to 60 • If A:W = 40 and processing water @ 700 gpm = 28,000 cfm blower • Approximately 200 hpBlower

11. Pilot • Assumed 20:1 A:W ratio or 14,000 cfm • Determined Approximate Area Diffusors for 14,000 cfm in Clearwell 2 • Assumed One/half Depth of Clearwell or 7 feet • Calculated the Volume over the Diffusors • Developed the Detention Times in the Three Celled Clearwell • Influent Cell 60 minutes • Aeration Cell 75 minutes • Effluent Cell 60 minutes • Scaled down the flows of air and water to match a 4-inch PVC pipe

12. Pilot

13. Test Pipe Arrangement

14. Pilot Protocol • Two Pilot Steps • First Step Test Entire A:W Range • Second Step Optimize Results of the First Step • Goal was to Optimize Air Required • Parameters Tested • TOC • THM • HAA5 • Chlorine Residual • Stability • pH • Total Alkalinity • Total Hardness • Calcium Hardness • TDS • Chlorides • Sulphates

15. Pilot Results

16. Pilot Results

17. Other Pilot Results

18. Project Costs • Aeration System • 5:1 A:W ratio 3,500 scfm Blower • Stainless Steel Diffusors • Caustic Soda Feed System to increase pH to 8.9 • 12-inch Air Piping to Clearwell Diffusors • Electric and Controls • Project Cost - $401,700 • Annual O&M - $73,000 • GACSystem • Project Cost - $1,225,600 • Annual O&M - $145,000

19. Brand X • 2011 SolarBee Aeration System Proposal • Two 15 HP Blowers 580 scfm Each • Three Submersible Mixers • 86 Diffusor Assemblies • Caustic Soda Feed System to increase pH to 8.9 • 8-inch Air Piping to Clearwell Diffusors • Electric and Controls • Project Cost - $571,700 • Annual O&M - $21,000 • SolarBeeOffer • Install Clearwell Equipment • Provide Temporary Blower and Piping • 6-month Trial • If Satisfied, Purchase Price $360,000

21. Second Thoughts • April 1, 2012 SolarBee Oops • Further Testing Showed Spray Aeration Preferable • Highly Recommended Spray System • One GS-12 Submersible Mixer in Clearwell 1 • Two SN-15 Floating 15 HP Pump/Mixer/Spray Systems • Two Ventilation 2HP Blowers 750 scfm Each • Caustic Soda Feed System to increase pH to 8.9 • 12-inch Air Piping to Clearwell • Electric and Controls • Project Cost - $369,900 • Annual O&M - $22,000 • SolarBeeOffer • Provide In-Clearwell Equipment and Two Blowers • Install Clearwell Equipment • 6-month Trial • If Satisfied, Purchase Price $168,000

23. Schedule • Bid – October 2012 • Preconstruction Meeting – November 2012 • Substantial Completion – March 2013 • Total Completion – June 2013

24. TTHM Summary (all values TTHM in ppb, except where noted)

25. Maximum Residence Time Running Annual Average

26. Take Away Information • THMsHave to be Formed • Aeration Does Not Reduce Formation Potential • Chloroform is Typical Target THM • Powered Air Supply for Ventilation Probably Required • Check pH/Stability • Check Chlorine Residual