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Sludge Removal
May 05^th, 2012, 6:36am

Hii All,

I am trying to understand the sludge dewatering systems.

finding some of the queries as below can anyone help me out?

1) What are the criteria for selecting the need to primary clarifier?
2) What is the sludge consistency after Primary Clarifier, Sec Clarifier, HRSCC and Thickener?
3) How sludge is removed from the clarifier?
4) How to decide the sludge removal time period?
5) If I want to take sludge from primary clarifier to thickener, do I required sludge sump? If yes, what should be the retention time?
6) Is thickener having batch process or contious?
7) Do Thickener have any feed limiting conditions w.r.t. sludge consistency?
8) Is the sludge been recycled in case of primary clarifier?

As of now I restricted this question list upto this only. But, lot of more question still running in mind.

Plz kindly help me out Embarrassed

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Geoff

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Re: Sludge Removal
Reply #1 - May 5^th, 2012, 10:00pm

Lots of questions...I'll answer the bits I have direct knowledge of.

1) What are the criteria for selecting the need to primary clarifier?
A plant that has only secondary treatment uses a lot more energy than a plant with both primary and secondary treatment. The civil and O & M cost of primary treatment has to be weighed against overall cost savings.

2) What is the sludge consistency after Primary Clarifier (3 - 4%), Sec Clarifier, HRSCC and Thickener (4 - 5%)?
I used to aim for the figures shown in parenthesis but it is plant & equipment specific.

3) How sludge is removed from the clarifier?
Scraper system moves settled sludge to off-take where a positive displacement pump transfers it to sludge treatment area.

4) How to decide the sludge removal time period?
Operate sludge pumping system to remove target mass or volume of sludge each day - thus target density ( 3-4%) will be achieved

5) If I want to take sludge from primary clarifier to thickener, do I required sludge sump? If yes, what should be the retention time?
Not sure what your asking - sump where?

6) Is thickener having batch process or contious?
A bit of both. The feed from the primary clarifiers might be for 10 to 20 hours per day. Sludge systems work best with a fairly continuous removal of sludge so it doesn't get too thick and then difficult to pump.

7) Do Thickener have any feed limiting conditions w.r.t. sludge consistency?
Thickeners are limited by their discharge thickness more than anything. Once a sludge gets above 6 to 8% you need very high performance pumps. The sludge ceases to behave like a normal fluid at higher densities

8) Is the sludge been recycled in case of primary clarifier?
Some plants waste their secondary sludge to the primary clarifier so it can be co-thickened in the one thickening system.

Cheers

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Flowing Fluid

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Re: Sludge Removal
Reply #2 - May 6^th, 2012, 11:35pm

Thanks a lottt Geoff,

Most of the questions have been resolved...

Now I can atleast understand the some of the things which are nor found in book.

Regarding below question,

5) If I want to take sludge from primary clarifier to thickener, do I required sludge sump? If yes, what should be the retention time?

I want to ask that when we remove sludge from primary clarifier then do we required it to store in sludge storage tank before feeding into Thickener of we can directly pumped it into thickener?

Thanks Again.....

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Geoff God Member Offline Posts: 1006 Gender: Company or Organization: Retired. :-)	Re: Sludge Removal Reply #3 - May 7^th, 2012, 1:16am Unless there are specific reasons to do otherwise I would use the thickener as the storage tank. What is the treatment capacity of the plant? Cheers
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Min YaBB Newbies Offline I love Water and Wastewater.com Posts: 6 Company or Organization: Yooqi Water Treatment	Re: Sludge Removal Reply #4 - May 9^th, 2012, 11:01pm cake filtration screw press can directly dewater sludge from from primary clarifier even sludge as dilute as 0.1% solid.hope it is useful for you !
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