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 Engineers at Entex determined that 16 units would

need to 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

2014 Finally a cold winter to really test the system out.

How did it perform?

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

Questions