Water and Wastewater.com Help Forums - how to lower SVI & MLSS?

jeffryy

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how to lower SVI & MLSS?
Jun 25^th, 2012, 7:31pm

Hi all,

I have four 4-Litre lab scale SBR runnning for 3 cycles a day (8hr x 3). With aeration, then anoxic phase during mixing. but somehow, the settling for each of them are different:

MLSS (mg/L) A B C D

20/06/2012 4000 3900 4700 4200

25/06/2012 3500 3800 4900 4100

SVI
20/06/2012 70 76.9 161.7 133.3
25/06/2012 85.7 68.4 151.0 126.8

I am currently wasting 150ml each, for 2 of the cycles, (300ml wasted a day) during end of mixing phase. pH is approx 7.5 and DO approx 5-6mg/L.

SBR C currently has the worst settling and by observation, SBR A's settling seems to be getting worse and looking like SBR D.

I know that I cannot waste too much, but is there anyway to bring down the MLSS and lower the SVI as well? Is it better if I change the wasting to 300 ml once/day without breaking it up to twice a day?

Any comments are appreciated. Thanks

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grrun God Member Offline WaterandWastewa ter.Com is the best! Posts: 3525 Pekin, IL Gender: Company or Organization: Freelance Environmental Engine	Re: how to lower SVI & MLSS? Reply #1 - Jun 25^th, 2012, 9:23pm I'm not sure what the feed BOD is, but 1,000mL/300mL is sludge age of 3.33 days. To improve settling, you should have a sludge age of 10 days or more. To promote NH₃-N oxidation, the sludge age needs to be greater than 7 days. I would try to reduce wasting to 100mL/day for starters. grrun
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jeffryy YaBB Newbies Offline I love Water and Wastewater.com Posts: 20 Company or Organization: rmit	Re: how to lower SVI & MLSS? Reply #2 - Jun 26^th, 2012, 1:04am sorry, but it is 4 litres capacity SBR. maybe I should write it as 4x 4L SBRs to make it less confusing.
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Eric Raj

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Re: how to lower SVI & MLSS?
Reply #3 - Jun 26^th, 2012, 8:43am

You probably need to increase your wasting to 400-450 mls per day. This would give you a sludge age of 8.8-10.0 days. See if this gives you improved settling.

The variation of your four SBRs indicates that dissimilar conditions exist in each. Either they were not originally set up identically, or else the wasting has not been accurately performed.

~Eric Grin

Love this break from the high heat and humidity! Long range outlook though is for hot weather to stay for about two weeks.

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jeffryy YaBB Newbies Offline I love Water and Wastewater.com Posts: 20 Company or Organization: rmit	Re: how to lower SVI & MLSS? Reply #4 - Jun 26^th, 2012, 9:11pm The COD of feed is about 600-700 mg/L and yes, you are right, C and D are originally wasted more than A&B. Then I try to standardise them by wasting the same amount for all, but they still do not display the same results. I will try to increase the wasting for all Thanks
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almar1965 God Member Offline Composting is the work of Satan !! Posts: 1269 Santiago Gender: Company or Organization: Sinquiver Ltda	Re: how to lower SVI & MLSS? Reply #5 - Jul 5^th, 2012, 12:07pm Hi if you wish to retain the same conditions in each unit you may need sightly different rates of wasting for each until they all have the same MLSS figure. regards Alistair
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