Water and Wastewater.com Help Forums - Needing Help with VAs with UASBs

msusprtn

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Needing Help with VAs with UASBs
May 11^th, 2012, 5:37pm

We have 2 UASBs (1MMgal each). They are fedd from a common EQ tank. One baffle section (approximately 15% of the total baffles) has fallen in each reactor. We have put a temporary repair in each... a piece of plastic sheet stock at a slight angle. Both of the reactors were loosing biomass like crazy prior to doing this.. They appear to have stabilized. Granules looking nice.. small, dense, black. We also added a surfactant to try to help the granules release.

1 of the reactors has recently started to have eleveated VAs. It went from 60-100 up to 150-180... We have slowed down the flow into that reactor.

The lateral distribution in the bottoms are a little plugged up, but there doesn't seem to be a major difference between the 2. The reactor that has the higher VAs does churn at the surface quite a bit more than the other. The baffle patch wasnt quite as effective on it.

We have been purchasing biomass like crazy trying to keep them going.

Was hoping for some ideas as to why the VAs would be higher. We will be repairing the baffles in June. Draining the tanks and cleaning out the distribution piping. Also, would missing 15% of the baffles be enough to lose all of our biomass?

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Peter_McCarthy

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Re: Needing Help with VAs with UASBs
Reply #1 - May 12^th, 2012, 7:53am

Hi Mauaprtn

When you say baffle, do you mean the GLSS? Sounds like you may have an influent distribution issue as you suggest. This will cause short circuiting in the reactors and this will lead to solids loss and higher VA. Did the existing design allow for flushing of the influent distribution laterals?

What is the COD and TSS loading on the reactors (kg /cu m.d)? Are you overloading the reactors?

Peter

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Peter_McCarthy Full Member Offline Water and Wastewater.com is the best! Posts: 191 Company or Organization: ADI Systems Inc.	Re: Needing Help with VAs with UASBs Reply #2 - May 12^th, 2012, 7:56am Any chance of using a temporary small tank after UASB to settle granules and use a positive displacment or air diaphagm pump to recycle captured granules back to UASB? If VA is high you need as mucch sludge mass as you can get. Peter
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msusprtn

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Re: Needing Help with VAs with UASBs
Reply #3 - May 14^th, 2012, 2:17pm

Baffle=GLSS... ours are "V" shaped if that helps any.

The existing design makes flushing difficult. There are several circuits in each UASBs... cleaning them out is done by sending the water flow through only 1 circuit at a time... so there isn't really a good way to flush them.

Each UASB is processing about 20,000 lbs per day of COD. Design is 2X that. TSS going into the UASBs is around 300 mg/l. TSS out is 600 mg/l for both... prior to having this problem TSS out was around 300 mg/l.

We arent set up for a tank to help settle the biomass out. Flow rate is around 800 gal/min... I'm thinking we'd have to get a pretty decent sized tank to do it.

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msusprtn YaBB Newbies Offline I love Water and Wastewater.com Posts: 3 Company or Organization: cpkelco	Re: Needing Help with VAs with UASBs Reply #4 - Oct 29^th, 2012, 3:59pm Just a follow-up We repaired them in June... the baffles were in worse shape than originally thought. The distribution headers were also plugged up pretty bad... lots of baffle debris (LOL). Now that the baffles & distribution systems are correct our anerobic biomass is back to growing! Wish it would grow faster!
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