Im baaaaaacccckkkkk!

Ok lets tackle this plant.  Still having unresolved issues.  

This is a 30,000/gpd package plant operating at 9000 gpd average.  Activated sludge.  Upflow clarifier.  Inf AVGs  200mgl BOD, 35mg/l NH3, 60 TKN, 6 total phos, 200 TSS.  We run, 9gpm through the plant, 120 gpm RAS(due to denitrification in clarifier standard 4.5times design flow or 46gpm.)  I have a Areation compartment  of 5473 gallons, Anoxic of 9859 gallons, and a clarifier of 3373 gallons.  I have another clarifier and aireation but is not used due to lower flows.  

D.O. stays at 2-3mg/l in AR and <0.20 in AX.  

Now why do I almost always have cake batter looking sludge on the clarifier surface?  Settleability is never observed as settling like a rock.  Manual says to let the MLSS run 1500 to 3500.  SO we run by MCRT calculating waste daily with a centrufuge of AR,AX,Clarifier core and RAS concentrations.

Typically we have had M.Parv, but recently we have had 0411 and S.Natans.

This area has only 100 customers.  Homeowners alone.  I have run samples on scum, core and whatnot for FOG.  The core of the clarifier has 170 mg/l of FOG.  Could that be my one and only issue or could there be more.  It is winter, sort of.......Water temp is below 10c.  

I would really like to find any solutions possible.  Years of fighting this plant and justifying myself over and over is getting old. Help me stop beating the dead horse and bury it.  I'm serving crow soon!

Hmmmm, mine is a single sludge system.  Runs in a loop from the clarifier to the AX zone to the AR back through the Clarifier.  MCRT of 30 days.  My clarifier is or always shoud be moving in the single sludge. If I waste it is to a holding tank for dewatering and disposal.  I could drop the MCRT to 25 days, that in turn drops my mlss down respectively.  They run hand in hand at this plant.

SO we run by MCRT calculating waste daily with a centrufuge of AR,AX,Clarifier core and RAS concentrations. and The core of the clarifier has 170 mg/l of FOG.

I don't really understand how only the core of the clarifier has a high FOG. My thinking is that the RAS should have a high FOG also. If you are running a liquid-liquid extration on the core; there may be some analytical interferences causing this high value.

While I'm a proponent of centrifuging sludge samples for MCRT determinations; I think that you may be over controlling the system. Because the AX detention time is approximately twice the detention time of the AR; I would look at the AX to see if denitrification is floating the sludge there as well. Anyway, my conclusion is that your sludge is too old.

Have you checked to determine if the WAS varies much in MLSS concentration throughout the day? This could be a problem with WAS and MCRT determination. Personally, I would try using only the (WAS)MLSSs/(AR)MLSSs and ignore the other MLSSs to estimate MCRT and I would lower the MCRT until the sludge begins to settle better even if the AR MLSSs drop. Remember, you are only running at 1/3 design rate.

Just my approach,

grrun

anything over 100 mg/L is considered high and will generally cause bulking and foaming problems. The best bet is to try to control at the source. I respectfully disagree that sludge age is the root cause of this problem but it is always an important parameter to look at.

best regards,

Ryan

I would then go and control my F/M by realizing that I am at one third design capacity on the flow.  You need to recalculate your MLSS targets, RAS return rate targets, and the WAS rate targets.  I would reduce the MCRT first and then the RAS rate back closer to the 41 gpm it is designed for.  

I would also try to figure out where the oil & grease is coming from and do community outreach to reduce it.  I am assuming that you do not have any primary clarification where the grease can be skimmed off.  Your MLSS could very well need to be between 450-1050 mg/l at the daily flow you currently have.  Be patient and good luck!

~Eric    Winter is coming back to Virginia this weekend!  Bad timing.

If S. Natans is the root cause of the poor settling then increasing wasting is the OPPOSITE of what you should do. S. Natans in large abundance indicates low DO for the applied F/M. Lower the F/M (increase sludge age) and increase the DO. It is essential though that you know for sure what filament you're dealing with/ what's predominant ect. Please note this advice is only based on the identifications you provided.

check your pm's

How are you coming with the settling tests?

grrun

Good idea with the FOG degraders- just make sure you're getting the bugs, not the enzymes. It's too bad they don't outcompete M. Parvicella so I'd do this in the collection system.

Detension time in the clarifier is more like 6 hours and the sludge rises in 2 hours which indicates that you haven't achieved a good sludge age yet. However, it does show that you're going in the right direction!

grrun

Consider that having 1 mg/L DO going into the clarifier will reduce the time that is required before denitrification becomes a problem. Closely monitor the settling tests.

It is difficult to collect influent composite samples for FOG. I would try to measure FOG in the MLSS samples to determine if the influent is getting an increasing, decreasing, or steady concentration of FOG.

Do you observe any oil or sludge floating in the centrifuged samples?

grrun