Water and Wastewater.com Help Forums - Turbid Clarification, MLSS question

cth07

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Turbid Clarification, MLSS question
May 17^th, 2012, 10:41am

Hello all, new to the forum and looking for some help.
Operating a .650mgd municipal plant.
.7Mgal Schrieber aeration
.65Mgal oxi-ditch
3 50hp floating aerators
1 tornado mixer

2200 mlss, 76% Mlvss
450-500 CBOD
250-600 inf. SS, 2-8 eff SS
30 min Sett. 600 give or take 100 for both Hexaditch & Schrieber

Influent flows to Schrieber first the to ditch (all mlss to ditch no raw). Clarifier is after ditch and RAS goes back to Sch. tank.

Now question, we have had increase in BOD but have not increased the MLSS alot. Our eff. is turbid but usually at this time of year it is super clear(read a paper through it). Our F/M is between .11 and .12. The plant design is for .06-.08. We have never had to increase the Mlss so much but I think this is what needs to be done. Our settability is a concern too but the clarifier blanket stays <1ft. Any suggestion, comments will be appreciated. Let me know if more info is needed.

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The sludge judge God Member Offline Posts: 649 Wisconsin Gender: Company or Organization: private	Re: Turbid Clarification, MLSS question Reply #1 - May 17^th, 2012, 12:08pm Based on the info you provided raising the MLSS is a good idea to keep the F/M in line. I left you a mailing address for a microscopic eval as a professional courtesy. I'd like to find out the cause for your SVI being high. What is your DO?
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cth07 YaBB Newbies Offline I love Water and Wastewater.com Posts: 2 Company or Organization: Claiborne Utilities Dist.	Re: Turbid Clarification, MLSS question Reply #2 - May 17^th, 2012, 1:51pm depending on load, D.O. is 1.5- 3.5 max I am concerned we either don't have enough or too much. I have read other post with turbid eff. where the was endogenous respiration. As stated, usually, we have very clear eff. this time of year. That is relative though...
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The sludge judge God Member Offline Posts: 649 Wisconsin Gender: Company or Organization: private	Re: Turbid Clarification, MLSS question Reply #3 - May 17^th, 2012, 1:59pm based on the numbers, I'd suspect this is straggler floc. The protozoa/ metazoa, type of filaments, and floc size (<150um for pin floc, younger sludge larger and generally more diffuse)
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Tom Keenan - nesa

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Re: Turbid Clarification, MLSS question
Reply #4 - May 18^th, 2012, 4:54am

This definitely sound like a "young sludge" (or high f/m problem). if you increase the sludge age by allowing the MLSS to increase, (by reducing sludge wasting, NOT by stopping sludge wasting), then I expect that the effluent quality will improve.

If you design is for an f/m of only 0.06 to 0.08, and you are currently operating at 0.11 to 0.12, then the MLSS needs to be increased to about 4,000 mg/l.

D.O. in the range 1.5 mg/l to 3.5 mg/l is fine and should not be seen as a problem.

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tomkeenan@nesa.ie
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