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The City of Clare, A Case Study
A Case Study of Ammonia Reduction in a Lagoon Treatment System
By John Holland
The City of Clare WWTP The Clare WWTP was constructed in 1989. It is one of
the few continuous flow through lagoons in Michigan.
The plant consists of
Bar Screen
Microscreens
3 Aerated Lagoons
2 Clarifiers run in series
FeCl2 and Polymer fed
UV Disinfection
The City of Clare WWTP The average influent ammonia nitrogen is ranges from
15 to 20 mg/L.
The average BOD ranges from 180 to 250 mg/L.
Average flow is 600,000 gallon per day.
Detention time is about 30 days in the lagoons.
During the winter water temperature can be as low as slightly above 32F.
The issue. The NPDES permit limit for Ammonia Nitrogen is 11.0
mg/L from May 1st to Sept. 30th.
Even with this limit the Clare WWTP could not meet this limit during the months of May, June and part of July.
In 2008 the MDEQ issued a directive that the issue be resolved.
The Solutions Examined The City of Clare and their engineer of record, Goudie,
Fraser and Associates began to look at possible solutions.
Solutions examined
Mechanical Plant
Turning part of one of the lagoons into basically an activated sludge pond.
Air stripping
Fixed media
Solution Selected The fixed media option was selected.
Most cost effective
Clare WWTP only needed to lower ammonia nitrogen by about 40% for 3 months of the year.
Could use existing aeration blower as back-up.
Did not require extensive modification to the plant.
Lagoons were left in operation as units were installed.
The Fixed Media The fixed media chosen was the ENTEX Technologies,
Inc. Webitat modules.
A pilot study was performed in early spring to ensure that the units would work under the conditions present at the Clare WWTP.
The pilot study performed very well under the conditions.
The Pilot Plant
The Process It was determined that 16 units would be installed.
The first 6 would be installed in lagoon #1 to enhance BOD removal.
There would be no changes to lagoon #2.
The final 10 units would be installed in lagoon #3 primary function would be ammonia nitrogen reduction.
The Modules
Installation
Aeration System
Piping and Control Valves
Piping continued
Lagoon Mixing The Webitat units did require additional mixing to
ensure proper removal.
The 8 - 30 HP aerators were removed from lagoon #1 and replaced with 6 – 15 HP aerators.
The diffuser system in lagoon #3 was determined to be sufficient for mixing.
Operation Units have controlled air flow
Control valves open once a week to full to scour the media
And now for the Important Stuff
Well how’s it working? Installed December 2011
Ammonia Final Effluent 2012
1/1/
2012
1/10
/20
12
1/19
/20
12
1/28
/20
12
2/6
/20
12
2/15
/20
12
2/24
/20
12
3/4
/20
12
3/13
/20
12
3/22
/20
12
3/31
/20
12
4/9
/20
12
4/1
8/2
012
4/2
7/20
12
5/6
/20
12
5/15
/20
12
5/24
/20
12
6/2
/20
12
6/1
1/20
12
6/2
0/2
012
6/2
9/2
012
7/8
/20
12
7/17
/20
12
7/26
/20
12
8/4
/20
12
8/1
3/20
12
8/2
2/20
12
8/3
1/20
12
9/9
/20
12
9/1
8/2
012
9/2
7/20
12
10/6
/20
12
10/1
5/20
12
10/2
4/2
012
11/2
/20
12
11/1
1/20
12
11/2
0/2
012
11/2
9/2
012
12/8
/20
12
12/1
7/20
12
12/2
6/2
012
0
5
10
15
20
25
Series1
Ammonia Final Effluent 2013
1/1/
2013
1/10
/20
13
1/19
/20
13
1/28
/20
13
2/6
/20
13
2/15
/20
13
2/24
/20
13
3/5/
2013
3/14
/20
13
3/23
/20
13
4/1
/20
13
4/1
0/2
013
4/1
9/2
013
4/2
8/2
013
5/7/
2013
5/16
/20
13
5/25
/20
13
6/3
/20
13
6/1
2/20
13
6/2
1/20
13
6/3
0/2
013
7/9
/20
13
7/18
/20
13
7/27
/20
13
8/5
/20
13
8/1
4/2
013
8/2
3/20
13
9/1
/20
13
9/1
0/2
013
9/1
9/2
013
9/2
8/2
013
10/7
/20
13
10/1
6/2
013
10/2
5/20
13
11/3
/20
13
11/1
2/20
13
11/2
1/20
13
11/3
0/2
013
12/9
/20
13
12/1
8/2
013
12/2
7/20
13 0
2
4
6
8
10
12
14
16
18
Series1
Ammonia Nitrogen 2014
1/1/
2014
1/10
/20
14
1/19
/20
14
1/28
/20
14
2/6
/20
14
2/15
/20
14
2/24
/20
14
3/5/
2014
3/14
/20
14
3/23
/20
14
4/1
/20
14
4/1
0/2
014
4/1
9/2
014
4/2
8/2
014
5/7/
2014
5/16
/20
14
5/25
/20
14
6/3
/20
14
6/1
2/20
14
6/2
1/20
14
6/3
0/2
014
7/9
/20
14
7/18
/20
14
7/27
/20
14
8/5
/20
14
8/1
4/2
014
8/2
3/20
14
9/1
/20
14
9/1
0/2
014
9/1
9/2
014
9/2
8/2
014
10/7
/20
14
10/1
6/2
014
10/2
5/20
14
11/3
/20
14
11/1
2/20
14
11/2
1/20
14
11/3
0/2
014
12/9
/20
14
12/1
8/2
014
12/2
7/20
14 0
5
10
15
20
25
30
Series1
2014 Finally a cold winter to really test the system out.
How will it perform? – stay tuned!!!
Questions