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Reducing THM via Aeration: A Case StudyNovember 21, 2013

by Gary Williams, P.E.Jones & Henry Engineers

Southeast AWWA District Meeting

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Agenda

Location History Pilot Implementation Take Away Information

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Location Map

Distribution System Map

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Water Quality 2008

Raw WaterTotal Hardness 285 mg/L as CaCO3

Total Alkalinity 133 mg/L as CaCO3

pH 8.2

Turbidity 3.2

Total Organic Carbon 4.5 mg/L

Finished WaterTotal Hardness 150 mg/L as CaCO3

Total Alkalinity 36 mg/L as CaCO3

pH 9.2

Total Organic Carbon (average) 2.1 mg/L

TOC Removal (average) 51%

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THM 2008

Date of Sample

Sample Location Second Quarter 2007 Average RAA

MR002 LRAA

HAA5Average RAA

5/24/2007 RD002 38.9 13.4RD003 40.8 14.4MR002 50.2 43.3 47.8 59.3 11.8 13.2 17.8

7/10/2007 RD002 82.3 16.6RD003 85.3 15.2MR002 102.0 89.9 50.4 60.6 16.7 16.2 14.4

10/11/2007 RD002 54.1 17.3RD003 58.3 16.4MR002 81.7 64.7 58.1 69.3 22.0 18.6 15.9

1/16/2008 RD002 40.6 19.3RD003 40.7 20.8MR002 54.9 45.4 60.8 72.2 20.4 20.2 17.0

4/2/2008 RD002 40.5 13.6RD003 40.6 13.1MR002 60.3 47.1 61.8 74.7 14.2 13.6 17.1

7/8/2008 RD002 85.1 33.1RD003 85.3 32.1MR002 131.0 100.5 64.4 82.0 34.7 33.3 21.4

10/9/2008 RD002 52.0 28.8RD003 55.7 28.8MR002 80.6 62.8 63.9 81.7 33.3 30.3 24.4

Fourth Quarter 2008

Total Trihalomethane & HAA5 2007/2008

Thrid Quarter 2007

Fourth Quarter 2007

First Quarter 2008

Second Quarter 2008

Third Quarter 2008

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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 MIEX Benchtop Study 2006 RSSCT for GAC Benchtop Study 2008 THM Reduction via Aeration Opflow Article

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2008 THM Reduction via Aeration Opflow Article

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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 hp Blower

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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 Cell75 minutes Effluent Cell 60 minutes

Scaled down the flows of air and water to match a 4-inch PVC pipe

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Pilot

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Test Pipe Arrangement

Pilot Air Requirements

Air: Water Ratio Required (cfm) Total Air (cf)

2:1 0.1 9.5

5:1 0.25 23.8

10:1 0.5 47.5

20:1 1.0 95

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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

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Pilot Results

Air: Water Air RateTrihalomethane Results

(ug/L)Ratio (scfm) October 14 November 11

Control N/A 47.1 38.02:1 0.10 16.9 16.75:1 0.25 5.7 9.07:1 0.35 N/A 6.710:1 0.50 2.1 5.720:1 1.00 2.7  30:1 1.50 2.6  40:1 2.00 3.0  50:1 2.50 2.1  

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Pilot Results

0 5 10 15 20 25 30 35 40 45 50 550.0

5.0

10.0

15.0

October 14November 11

Air to Water Ratio

Tri

halo

met

hane

s (ug

/L)

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Other Pilot Results

Temperature October 16 deg C November 12 deg C

Control Sample (no aeration) TTHM

Initial – 52.6 ug/L Finish – 47.1 ug/L

pH Initial – 9.3 Aerated – 7.9

Cl2 Free mg/L Initial – 2.13 Aerated – 1.96

Cl2 Total mg/L Initial – 2.45 Aerated – 1.19

@ A:W ratio > 10:1 CHBrCl2, CHBr2Cl, CHB3 below Detectable Limit

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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

GAC System Project Cost - $1,225,600 Annual O&M - $145,000

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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

SolarBee Offer Install Clearwell Equipment Provide Temporary Blower and Piping 6-month Trial If Satisfied, Purchase Price $360,000

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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

SolarBee Offer Provide In-Clearwell Equipment and Two Blowers Install Clearwell Equipment 6-month Trial If Satisfied, Purchase Price $168,000

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Schedule

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

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TTHM Summary

Sample Date

Water Temp (deg C)

Clearwell 1 Effluent

Clearwell 2 Effluent

DS202 (Max

TTHM)% Removal In Clearwell #2

Regrowth in System

4/3/2013 7 29.6 18.4 31.8 38% 13.4

5/6/2013 15 47.2 20.4 43.4 57% 23.0

5/20/2013 18 56.2 24.8 64.7 56% 39.9

6/17/2013 22 62.7 21.2 62.3 66% 41.1

7/1/2013 24 63.2 30.7 64.7 51% 34.0

8/13/2013 23 53.3 20.3 52.1 62% 31.8

9/9/2013 20 56.0 20.5 52.6 63% 32.1

Note: Baffle wall opening sealed on 4/12/2013

(all values TTHM in ppb, except where noted)

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Maximum Residence Time Running Annual Average

First Second Third Fourth First Second Third Fourth First Second Third Fourth2011 2012 2013

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

TTHM (ppb)HAA5 (ppb)

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Take Away Information

1. THMs Have to be Formed Aeration Does Not Reduce Formation Potential

2. Chloroform is Typical Target THM3. Powered Air Supply for Ventilation Probably

Required4. Check pH/Stability5. Check Chlorine Residual