hi al experts.
i am working in a Effluent treatment plant which consist of equalisation followed by anaerobic hybrid reactor then activated sludge process and At and clarifier...it is brewery plant, and 13mld capacity...with the flow rate of 40kl/hr treated...the problem is, the clarifier gets disturbed once in ten days and even after sludge is removed from clarifier constantly..the turbidty remains...wats the solution and SVI 30  of aeration tank is maintained 400 ml/ltr settling....sometimes the sludge floats on top...wats the reason

floating sludge (usually denitrification) has three key ingredients

very little/no dissolved oxygen, presence of nitrates (usually around 10 mg/L or greater will do it) and a readily available food source (soluble BOD). Eliminate one of the variables and you eliminate the problem.

This can be done several ways- a simple way that has worked at a few plants I've troubleshot is increasing the RAS rate and increasing the dissolved oxygen a bit higher than normal right before the clarifier. Another possibility is to add a denitrification step to your process, or if your permit allows lower your sludge age and skip nitrification all together.

As for the disturbance every ten days my best guess would be a higher influent BOD that day (possibly due to cleaning/ etc). It may be a good idea to test the influent COD in house daily to help control the flow rate from your EQ tank. One trick that works for me is if I know there's going to be an abnormally high COD that day, leave some extra room in the EQ tank to run the flow lower the next day. Try to maintain as constant of a loading rate as possible. (think lbs/day) Another possibility is to build up your MLSS to match the higher load coming on that day. (more bugs needed for more food)

That's just one possibility- to truly know what's going on when the clarifier is "distrubed" a microscopic examination should be done. From the info you provided it sounds like a periodic slug load.

sounds like you've got the same recipe for denitrification: nitrate, BOD, and low/no DO in the clarifier during this period. Denitrification is going to be tough, especially with the many hours of downtime.

That's an awful long time to have sludge/ wastewater sitting in the clarifier. You could try leaving the RAS pump on for another minute or two during the cycle, or at the end of the day even turning up the RAS pump before your shift is over for an hour or two to eliminate the blanket for the night.

An EQ tank would be nice, so you could feed at a constant rate and always have some water flowing through the plant.With some modifications, this situation may be better suited for an SBR. In industries we often have to work around what we have. The main thing is compliance though.

Dear grrun and sludgefather;
The RAS pumps work all day. Like i said, they work according to 30 min cycle, 24/7, regardless of there's wastewater flowing into the aeration tank or not. The air supply doesn't stop either. There're 2 air blowers in the system, working 24/7, shifting every 2 hours. And we do have EQ tank in the system. The problem is that the water pumps in the EQ tank work depending on the level switches. When the water reaches a certain level, the pumps work, and the water isn't enough for the system to work all day.

While the RAS rate is approximately 100%, I'm beginning to suspect that your discharge SS is high. Sitting overnight (?), the sludge is rising to the surface of the clarifier, but the water underneath is clear. What is the water like in the discharge? I would try to reduce the influent pumping rate by one way or another and slightly increase the wasting rate because this would reduce the denitrification problem. The operational control points that you are using are fine for a continuously operating plant; however, the intermittent flows to your plant are distorting the results. Are you discharging to a POTW (Publicly Owned Treatment Works)? What are your discharge limits? Where is the RAS discharge located?

Finally, I would take the time to observe the system for the entire operational cycle to see what happens during the various phases. I know that this may seem a waste of time because the system is automated; but this is the best way to find a solution to your problem.

grrun

i have white colour foam problem in aretion lagoon . in areation lagoon 3 floating areators fix in one vertical line . but due to some mechenical problem we have to stop the first areators moter. but after stoping i have foam problem from the another day so pls can u tell me why its coming and what the factor for coming this kind of problem..............

I was involved with a plant that had problems every 10 to 14 days during the extended commissioning phase.

It would seem the bright sparks who designed and operated it didn't seem to understand the concept of pH in relation to nitrification.  

The plant would begin to fully nitrify, the pH would drop very low, the low pH would kill off the nitrifiers.  The plant would recover then begin to nitrify...and so one every 10 to 14 days.  

This cycle continued until the started using the caustic dosing that was installed on the plant.

Check your pH thoroughly.

grrun,
It wasn't until I looked at a plot of all the results for the month that the problem jumped out at me.  Then the solution was simple.  Live and learn.

Just as an aside, I retire tomorrow after 43 years...

I hope to be able to continue to share my experiences, good and bad, for a while yet.

Cheers

Geoff

The sludgefather

The  farewell speech was so hard...I had to draw a deep breath a few times.

Fancy getting emotional about working in wastewater.  

I say what a load of old piffle  (whatever piffle is).