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crackcrack Ex Member	MLSS vs WAS/SRT Apr 01^st, 2012, 5:08am Hi there again, I am looking for a simple method of wasting sludge in order to keep a sludge age of around 12 days. I am thinking of using RAS pumps to return all A.S back to aeration and the then waste sludge from the aeration basin in order to keep a constant MLSS for the sludge age. Can anyone tell me an ideal MLSS to aim for? Thanks
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The sludge judge

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Re: MLSS vs WAS/SRT
Reply #1 - Apr 1^st, 2012, 8:18am

there is no magic number for MLSS. I've seen municipalities run at 1500 mg/L and some industries need to run at 8000 mg/L. I

What type of plant do you have, what are the requirements (nitrification?) Unless you have extended air 10 day SRT is probably a good starting point, let the MLSS go to where it wants to as long as everything else is running good.

I'm a big fan of wasting directly from the aeration tank. This makes process control much easier.

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The sludge judge God Member Offline Posts: 649 Wisconsin Gender: Company or Organization: private	Re: MLSS vs WAS/SRT Reply #2 - Apr 1^st, 2012, 8:20am misread your question: waste based on your desired SRT and the MLSS will drift to where it wants to go. don't worry about this number for now but still measure it and keep track of your F/M.
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crackcrack

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Re: MLSS vs WAS/SRT
Reply #3 - Apr 1^st, 2012, 2:30pm

Thank you for reply...

So what you are saying is that if a system creates 4000 MLSS over approx 10 days, then 4000 is the approx number?

If so then would that not be a good way to control WAS from aeration - keeping MLSS at that number?

Our systems are definitely a challenge. A massive FM ratio change for 8 weeks of every year - we get massive winery wastes that flip the FM from almost 10% to 100% overnight.

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« Last Edit: Apr 2^nd, 2012, 7:33am by crackcrack »

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The sludge judge

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Re: MLSS vs WAS/SRT
Reply #4 - Apr 2^nd, 2012, 8:47am

If SRT is your control strategy the same amount of sludge every day is wasted every day to keep the SRT at 10 days.The MLSS will fluctuate a little based on the F/M. Still watch your MLSS and F/M ratio and track them.

When you know the high strength waste is coming ditch the SRT control strategy and build the MLSS up before hand. Look at your past data and calculate what you would want your F/M ratio to be. (adjust this to when conditions are best at the plant). During this period shoot for a target F/M ratio or target MLSS concentration.

best regards,

Ryan

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crackcrack Ex Member	Re: MLSS vs WAS/SRT Reply #5 - Apr 2^nd, 2012, 2:09pm Thanks Ryan. I will work on this. Great information!
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