you can have high ammonia with low BOD. It depends on if nitrification is happening or not. The nitrifying bacteria are autotrophic while the BOD removers are heterotrophic. Heterotrophic bacteria eat organic carbon while autotrophs eat inorganic carbon.

If you want more nitrification you'll likely need to increase BOD removal first. Nitrification usually won't happen until most of the BOD is gone. You'll also need enough dissolved oxygen to keep the conditions in the trickling filters aerobic. Assuming there's enough dissolved oxygen if you want to increase BOD removal you'd probably need to find a way to enhance primary settlement or possibly step feed some of the waste two the second part of the trickling filter right away.

I'm not sure why you have an action limit on ammonia if there's no permit for it. It sounds like all is well for you.

best regards,

Ryan

If you have no ammonia consent then it is not essential to be concerned about ammonia values. Is the action level at 25 mg/l an internal (why do you have the value? What do you have to do when this is breached) or external (you do have a consent. What does your regulator expect you to do when this value is exceeded) requirement? Where do you discharge? If freshwater, what is the fish life like? (If poor, and you are charged on your discharges, you may wish to discuss with your regulator a reduction in charges in return for a committment to improving effluent quality - but do the cost analysis before you talk to the regulator.)

With filters you have restricted options to enhance performance. You could look at replacing the media with more modern, higher-surface, media, to provide a greater biofilm surface - but initially performance will fall off, while the new media gets populated.

You could look at recirculating final effluent if the media is not fully wetted - various guidelines on wetting rates available in the literature for different kinds of media. I can't remember what are the suggested wetting rates, but Metcalfe & Eddy might have these look-up tables.

If using forced aeration you could look at DO profiles and increasing the blower settings if the DO drops below 1.5 mg/l for a large aprt of the biotower.

You could look at adding a dedicated nitrifying activated sludge tank between the two biotowers, or after the final biotower.

Remember too that nitrification is going to take up a significant oxygen demand and this needs to be accounted for if this is something you want to accomplish.

Personally I agree fully with Bendle Boy, I think life is good and no worries. (time for some fishing!) It would be intersteing to find out how much of your BOD is CBOD and soluble CBOD and how much of it is from nitrification in the BOD test. It's very possible you might be getting good CBOD removal already.

best regards,

Ryan

I'm unsure that that this would work; but I would slightly decrease wasting. The decrease in wasting may increase the population of nitrifiers which would bring the ammonia concentration down without materially affecting BOD removal if adequate DO is maintained. I think that you would have to monitor DO, the effluent parameters, and sv 30 results closely. Anyway, this is my reasoning.

grrun

All biomass shed from the bio-tower is removed from the system and no "sludge" is recirculated. However I do believe that recirculation of some of the settled liquid from the clarifiers could improve Nitrification.

On another note would having the filter being made into just one stage and use what is at the moment the second stage part of the 1st stage and then increase primary settlement from 2 tanks into 4 make more of a difference? and then take out the middle stage of settlement.

the BOD COD removal is anywhere between 80 - 95% depending on the strength on the incoming trade effluent, Effluent temp is always in the mid teens. I have measured the PH of the sludge and that is quite acidic but never done the incoming flows.
I take it for effective BOD removal it is the filter that is key for this am I right?

we have a lime plant installed to dose lime powder into the liquid sludge to raise the ph to between 9 and 10, the hope was that the return liquors from the filter presses and dewatering the sludge tanks would help raise the ph levels on the incoming sewage from the town thus helping the sie generally.
I was told though that lime can possible increase ammonia too is this correct?

May have been mentioned by the others but if not, Have your scientific people check on alkalinity as well, if you don't have the buffering capacity, the nitrifiers won't work.

Man I wish I had a works without an ammonia consent...