1
Reducing THM via
Aeration: A Case Study
November 21, 2013
by
Gary Williams, P.E.
Jones & Henry Engineers
Southeast AWWA District Meeting
Agenda
2
Location
 History
 Pilot
 Implementation
 Take Away Information

Location Map
3
4
Distribution System Map
5
Water Quality 2008
6
Raw Water
Total 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 Water
Total 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%
THM 2008
7
Total Trihalomethane & HAA5 2007/2008
Date of
Sample Location
Sample
5/24/2007 RD002
RD003
MR002
7/10/2007 RD002
RD003
MR002
10/11/2007 RD002
RD003
MR002
1/16/2008 RD002
RD003
MR002
4/2/2008 RD002
RD003
MR002
7/8/2008 RD002
RD003
MR002
10/9/2008 RD002
RD003
MR002
Second
Quarter 2007 Average RAA
38.9
40.8
50.2
43.3
47.8
Thrid Quarter 2007
82.3
85.3
102.0
89.9
50.4
Fourth Quarter 2007
54.1
58.3
81.7
64.7
58.1
First Quarter 2008
40.6
40.7
54.9
45.4
60.8
Second Quarter 2008
40.5
40.6
60.3
47.1
61.8
Third Quarter 2008
85.1
85.3
131.0 100.5
64.4
Fourth Quarter 2008
52.0
55.7
80.6
62.8
63.9
MR002
LRAA
HAA5
Average RAA
59.3
13.4
14.4
11.8
13.2
17.8
60.6
16.6
15.2
16.7
16.2
14.4
69.3
17.3
16.4
22.0
18.6
15.9
72.2
19.3
20.8
20.4
20.2
17.0
74.7
13.6
13.1
14.2
13.6
17.1
82.0
33.1
32.1
34.7
33.3
21.4
81.7
28.8
28.8
33.3
30.3
24.4
Water History
8










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
2008 THM Reduction via Aeration Opflow
Article
9
Research
10
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

Pilot
11





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
Aeration Cell
Effluent Cell
60 minutes
75 minutes
60 minutes
Scaled down the flows of air and water to match a 4-inch
PVC pipe
Pilot
12
Test Pipe Arrangement
13
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
Pilot Protocol
14

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

Pilot Results
15
Air: Water
Ratio
Control
2:1
5:1
7:1
10:1
20:1
30:1
40:1
50:1
Air Rate
(scfm)
N/A
0.10
0.25
0.35
0.50
1.00
1.50
2.00
2.50
Trihalomethane Results
(ug/L)
October 14
November 11
47.1
38.0
16.9
16.7
5.7
9.0
N/A
6.7
2.1
5.7
2.7
2.6
3.0
2.1
Pilot Results
Trihalomethanes (ug/L)
16
50.0
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
October 14
November 11
0
5
10 15 20 25 30 35 40 45 50 55
Air to Water Ratio
Other Pilot Results
17
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
Project Costs
18

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

Brand X
19

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
20
Second Thoughts
21

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
22
Schedule
23
Bid – October 2012
 Preconstruction Meeting – November 2012
 Substantial Completion – March 2013
 Total Completion – June 2013

TTHM Summary
24
(all values TTHM in ppb, except where noted)
Sample
Date
Water Temp Clearwell 1
(deg C)
Effluent
Clearwell 2
DS202
% Removal In Regrowth in
Effluent
(Max TTHM) Clearwell #2
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
Maximum Residence Time Running
Annual Average
25
100.0
90.0
80.0
70.0
60.0
50.0
TTHM (ppb)
HAA5 (ppb)
40.0
30.0
20.0
10.0
0.0
First
Second
Third
2011
Fourth
First
Second
Third
2012
Fourth
First
Second
Third
2013
Fourth
Take Away Information
26
THMs Have to be Formed
1.

2.
3.
4.
5.
Aeration Does Not Reduce Formation Potential
Chloroform is Typical Target THM
Powered Air Supply for Ventilation Probably
Required
Check pH/Stability
Check Chlorine Residual