Hello there. Stumbled upon your site earlier today and after about a half hour of searching through the forums I couldn't find a solution to my problem so maybe you can help.

I run a plant whose influent is strictly citrus waste, high acid and sugar. We recently added on to the head of our system multiple surge tanks to aid with keeping a constant flow and keep our system from over flowing.

Currently our clarifiers have a very cloudy appearance could be from pin point flocs. My sludge blanket is kept between 2 and 3 feet. Aeration basins are a chocolate brown color with no odor. We have white soapy foam on the surface of all aeration basins but it could be due to detergents in the caustic cleaners used at the plant. pH is highly buffered very little to no NaOH is added after primary adjustments of pH before treatment. pH actually rises around .5 from start of treatment to the end.

I'm trying to figure out what is causing the darker color in the aeration basins and how to clear up my effluent.

My initial thoughts where old sludge but after a look under the microscope I saw only free swimming ciliates but no stalked ciliates.
Could nutrient deficiency be causing this?
Is it possible to have too much air?
Could the new surge tanks cause this? They are non aerated and are not agitated other than the pump that pumps into them. Is it possible sludge in those tanks could be septic and introducing into my system? We waste the sludge that does settle in them into our digesters but maybe we are not getting it all.

I'd appreciate your thoughts good to find some people to talk to about this stuff  

Infeed BOD is around 3000. Unfortunatly DO through the system is .5-.1. I have continued to add more fine bubble diffuesers to each of the basins to try and get it up but nothing seems to work. Thought our DO probe was messed up but used it in the lab with a beaker and a small air pump and I got readings. I currently have the air on a timer. About 42 min on 18 min off.  Going to switch it to always on and see if that helps. If not then may be off to order some new diffusers for each basin.

"We have white soapy foam on the surface of all aeration basins but it could be due to detergents in the caustic cleaners used at the plant."

While you have flow equalization, you do not necessarily have contaminant concentration equalization. If your influent consists primarily of cleaners from batch cleaning operations, then this may not be a problem. However, if the influent primarily consists of other flows with surges from batch cleaning operations; you may have to blend the wastewater from these cleaning operations to moderate the concentration fluctuations.

I'm not sure about the cloudiness in your effluent. You might try filtering a sample through filter paper and if the filtrate is still cloudy, it may be from surfactants. After filtration you may try shsking a sample in a bottle and if this produces a stable foam, surfactants may be the problem.

The soluble BOD/COD ratio may provide additional information. Surfactants usually take longer to biodegrade than sugars and organic acids.

Keep us posted,

grrun

I think that the proposed trial with "always on" aeration is worthwhile. Also if you could clarify Dallas's question ... was the DO 0.5 to 1.0 or was it 0.5 to 0.1 mg/L. (Obviously there is a huge significance to this)

I have not looked at the other responses, but you mentioned sugar being high.  That smacks of soluble COD and BOD which can also mean nutrient deficiency.  All of these have negative impacts upon biological processes.  You should check your concentrations of nitrogen, phosphorus, and carbon feeding into your aeration system.  This can point out what is lacking to allow maximum organism growth.  

The surge tanks ought to be mixed at the very least to prevent solids drop out.  Our equalization basins have dissolved air to keep things fresh and mixed.  

The cloudy aspect to the clarifiers indicates incomplete treatment; could be that nitrification has only partially occured, but more likely is that the soluble sugars have not been completely broken down due to lack of contact time with bugs which comes from both physical limitations of tank size and not enough bugs.

Good luck in finding a solution!

~Eric

Dallas:
No typo there it reads .1-.5 mg/L. I know very low. I calibrated the probe using room temp air, got a little over 8 mg/L so the probe is working correctly.

Tom:
Flow rate ranges from 30k gpd to 60k gpd. We have 12 aeration basins each holding roughly 5800 gallons a piece. We use two Roots universal blowers which alternate off and on. They put out about 1085 cfm spreading around 57 cfm per tank. They run at 4.5-5.0 psi.

Sobisch:
Going to check for orange oil late today when I get some free time. I will let you know the concentration although it may not be high due to not processing fruit currently.

Shortly after posting my first message yesterday I set the blowers to stay on continuously. I will be checking DOs daily to see if they begin to come up. We add back nutrients to our system but I haven’t had the concentrations checked in awhile, maybe I need more.

We got holes cut into the surge tanks so hopefully we can get some air into these tanks this weekend. Blending back our surges from tank cleaning with our normal sugar waste would be quite difficult although I believe getting some mixing in those surge tanks will help.

Thanks for all the ideas so far guys. Glad to find some people interested in this as much as me.

The rest of the 1085cfm is used for coarse air for mixing in the equalization tank and in digesters. Also to run the WAS and RAS pumps.

Diffusers are only a few months old and are EDI flexair fine bubble diffusers from the USA bluebook. I didnt think about the new and old being mixed but that makes perfect sence. We do keep an eye on bubble patterns coming up to make sure it looks even.

this is why I asked for a separation step before aeration.

Dear Ben W,

you might try to reduce the organic load by adding coagulants or flocculants.
Of course you should do some jar testing in advance.

Kind regards
T. Sobisch

I heartily agree.  Prevention is far better than trying to treat after the fact.  It saves money also!  Best management practices should be reviewed at the source industry and then enforced firmly.

~Eric