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

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Presentation on theme: "Reducing THM via Aeration: A Case Study November 21, 2013 by Gary Williams, P.E. Jones & Henry Engineers Southeast AWWA District Meeting 1."— Presentation transcript:

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

2 Agenda  Location  History  Pilot  Implementation  Take Away Information 2

3 Location Map 3

4 Distribution System Map 4

5 5

6 Water Quality 2008 Raw Water Total Hardness285 mg/L as CaCO 3 Total Alkalinity133 mg/L as CaCO 3 pH8.2 Turbidity3.2 Total Organic Carbon4.5 mg/L Finished Water Total Hardness150 mg/L as CaCO 3 Total Alkalinity36 mg/L as CaCO 3 pH9.2 Total Organic Carbon (average)2.1 mg/L TOC Removal (average)51% 6

7 THM

8 Water History  1972 Water Treatment Plant, Low Head Dam, and Reservoir Constructed  1993 Water Treatment Plant Study  1996 Reservoir Study  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 MIEX Benchtop Study  2006 RSSCT for GAC Benchtop Study  2008 THM Reduction via Aeration Opflow Article 8

9 2008 THM Reduction via Aeration Opflow Article 9

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 700 gpm = 28,000 cfm blower  Approximately 200 hp Blower 10

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 Cell60 minutes  Aeration Cell75 minutes  Effluent Cell60 minutes  Scaled down the flows of air and water to match a 4-inch PVC pipe 11

12 Pilot 12

13 Test Pipe Arrangement Pilot Air Requirements Air: Water RatioRequired (cfm) Total Air (cf) 2: : : :

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 14

15 Pilot Results Air: WaterAir Rate Trihalomethane Results (ug/L) Ratio(scfm)October 14November 11 ControlN/A : : :10.35N/A6.7 10: : : : :

16 Pilot Results 16

17 Other Pilot Results TemperatureOctober 16 deg CNovember 12 deg C Control Sample (no aeration) TTHM Initial – 52.6 ug/LFinish – 47.1 ug/L pHInitial – 9.3Aerated – 7.9 Cl 2 Free mg/LInitial – 2.13Aerated – 1.96 Cl 2 Total mg/LInitial – 2.45Aerated – A:W ratio > 10:1 CHBrCl 2, CHBr 2 Cl, CHB 3 below Detectable Limit 17

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 inch Air Piping to Clearwell Diffusors Electric and Controls  Project Cost - $401,700  Annual O&M - $73,000  GAC System  Project Cost - $1,225,600  Annual O&M - $145,000 18

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 inch Air Piping to Clearwell Diffusors Electric and Controls  Project Cost - $571,700  Annual O&M - $21,000  SolarBee Offer  Install Clearwell Equipment  Provide Temporary Blower and Piping  6-month Trial  If Satisfied, Purchase Price $360,000 19

20 20

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 inch Air Piping to Clearwell Electric and Controls  Project Cost - $369,900  Annual O&M - $22,000  SolarBee Offer  Provide In-Clearwell Equipment and Two Blowers  Install Clearwell Equipment  6-month Trial  If Satisfied, Purchase Price $168,000 21

22 22

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

24 TTHM Summary 24 Sample Date Water Temp (deg C) Clearwell 1 Effluent Clearwell 2 Effluent DS202 (Max TTHM) % Removal In Clearwell #2 Regrowth in System 4/3/ %13.4 5/6/ %23.0 5/20/ %39.9 6/17/ %41.1 7/1/ %34.0 8/13/ %31.8 9/9/ %32.1 Note: Baffle wall opening sealed on 4/12/2013 (all values TTHM in ppb, except where noted)

25 Maximum Residence Time Running Annual Average 25

26 Take Away Information 1. THMs Have to be Formed  Aeration Does Not Reduce Formation Potential 2. Chloroform is Typical Target THM 3. Powered Air Supply for Ventilation Probably Required 4. Check pH/Stability 5. Check Chlorine Residual 26


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