Water Environment Federation (WEF) Discussion Forums / Biological Nutrient Removal / WEF Discussion Forums / What is the reason for ammonia increase after activated sludge treatment? / Latest Posts

RE: What is the reason for ammonia increase after activated sludge treatment?

Milos — Mon, 31 Mar 2008 07:16:15 GMT

Too little data for answer. Key data are in the mass balance of the total nitrogen; inflow (before and after primary clarifier) - in kg/d. Also the external flows - externa substrate in the digestion, dosing of nutrients into biological stage.

RE: What is the reason for ammonia increase after activated sludge treatment?

Jerry — Sat, 29 Mar 2008 19:53:19 GMT

It may be spending to much time in the clarifier and getting anaerobic. Try increasing the return rate. The usual number is 100 % return rate of the influent flow.

RE: What is the reason for ammonia increase after activated sludge treatment?

Wiff P — Sat, 29 Mar 2008 11:09:58 GMT

I would agree with Woody's suggestion. The organic N component of influent BOD is being converted to ammonia as BOD is broken down. Running influent and effluent TKN (which will give you ammonia N and organic N which combined equal TKN) will likely confirm the conversion of organic N in the influent to ammonia N in the effluent. At these F/M's you'd expect that!

Wiff Peterson

RE: What is the reason for ammonia increase after activated sludge treatment?

Cocodrie — Wed, 26 Mar 2008 21:04:36 GMT

I would add to the list of things to watch:

Alkalinity - well known culprit when lacking;

Nutrients, especially phosphate.

Industrial wastes will often be out of balance when compared to domestic in which bacteria thrive.

RE: What is the reason for ammonia increase after activated sludge treatment?

Wiff P — Thu, 15 Nov 2007 15:51:57 GMT

Right, I would agree with those folks who responded that Organic N conversion to ammonia is likely cause. You should be able to confirm as was recommended by getting influent and effluent TKN data and looking for reduction of organic N component of TKN over to N. High F/M would indicate likely potential for only partial nitrification of ammonia produced from breakdown of organic N. Fact that the system is working implies plenty of organic N as ratio of ammonia to BOD is too low to facilitate BOD breakdown unless the nitrogen is there in another form, so it's likely there as ammonia N. A full nitrogen balance would be interesting to trace it all through but seems pretty likely you'll see what's happening from testing for reduced forms in influent and effluent (TKN, organic, ammonia)...

Wiff Peterson

RE: What is the reason for ammonia increase after activated sludge treatment?

bugwisperer — Sun, 21 Oct 2007 12:12:42 GMT

Woodie is the man. It makes me crazy when us engineers are getting ready to do a design and go sample for the routine stuff including ammonia but ignore the organic fraction which is only going to be recognized with the TKN test. Thank you Woodie!! Depending on the nature of the carbon (how readily bioavailable it is) you can get in trouble if your ammonia fraction is low and your organic fraction is more complex and slower to ammonify. ie, the bug can go to town on the carbon (believe theres quantities of acetate and glycol in soaps and shampoos ) but not have enough ammonia for cell synthesis. They dont like this at all and have seen on several occasions the mixed liquour turn snotty - stringy - almost like putting your hand in a polymer tank. This situation is of course not typical to normal doemestic wastewater but is in industrial wastes including some food process wastes. I havent read about any settling problems on this one and its highly unlikely there wouldnt be settling problems so I'm thinking there is likely high TKN that shows itself in excess ammonia at the butt end of the process.

RE: What is the reason for ammonia increase after activated sludge treatment?

rocsmith — Wed, 10 Oct 2007 13:14:37 GMT

The wastewater would require a BOD:N ratio of 5:1 for aerobic heterotrophic growth. There is probably a lot of organic N in the influent which is being converted to ammonia and partially nitrified.

RE: What is the reason for ammonia increase after activated sludge treatment?

Jerry — Mon, 08 Oct 2007 18:37:40 GMT

Do an Ammonia test on your centrate.

RE: What is the reason for ammonia increase after activated sludge treatment?

D Shulmister — Mon, 08 Oct 2007 12:46:27 GMT

Here is the simplistic view: You have a very high influent BOD. As the BOD (organic matter) breaks down, a large concentration of ammonia is released. The "bugs" reduce the BOD before oxidizing the ammonia to nitrate. With such a high BOD, there may not be sufficient treatment time to eliminate the ammonia. Further, if the influent is deficient in alkalinity, the conversion to nitrate will be suppressed. What you may be seeing is a point where the BOD is reduced, but the ammonia carries through to the clarifier. You will not likely oxidize the ammonia in the clarifier. Your type of influent is probably best handled in a pure oxygen plant. You may need to process the aeration basin flow through another unit (like an ammonia stripping tower) to get rid of the ammonia.

RE: What is the reason for ammonia increase after activated sludge treatment?

Woodie — Mon, 08 Oct 2007 12:32:12 GMT

Rather than run ammonia-N only, I recommended you also analyze total Kjeldahl nitrogen (TKN) in the AS influent. The difference between TKN and ammonia-N will give you the concentration of organic nitrogen. Organic nitrogen can be converted to ammonia-N in the AS process. If you do not have the capacity to fully nitrify the ammonia-N that is being formed, you would potentially experience a higher ammonia-N in the effluent than in the influent.

Woodie

RE: What is the reason for ammonia increase after activated sludge treatment?

ahawater — Mon, 08 Oct 2007 09:40:12 GMT

As far as I know, there is no anarobic digester existed. The sludge from the clarifier is collected in a storage tank, then goes to the vacuum filter. The filtrate is back to the EQ Tanks. Filter cake is for offsite disposal.

The sampling event is in the end of August. So I think the water temperature is not low.

Thanks very much for your inputs. Please share your more thoughts.

RE: What is the reason for ammonia increase after activated sludge treatment?

ahawater — Mon, 08 Oct 2007 09:34:57 GMT

The retention time of aeration tank is about 2.4 days. also why does the retention time matter? I think the cell retention time should be considered. I don't know the cell retention time yet.

F/M in this range is overloading? I think it might be a little bit higher, but not that high.

influent sampling location is after EQ tank, which flows into aeration tank.

The industry is making shampoo, soap products.

RE: What is the reason for ammonia increase after activated sludge treatment?

Jerry — Mon, 08 Oct 2007 00:38:07 GMT

What kind of waste are you treating? It looks extremely high in BOD/COD.

Do you have Anaerobic Digesters?

RE: What is the reason for ammonia increase after activated sludge treatment?

Sabir — Mon, 08 Oct 2007 00:35:40 GMT

What is about temperature and nitrite level? Determining the cause(s) for effluent is often a difficult and confusing problem. However, high effluent ammonia concentration has several possible causes. Effluent ammonia concentration may be high due to :

Cold temperature,
Organic overloading
Low oxygen concentration and low alkalinity
Short hydraulic detention time
Release of ammonia from old digesting sludge

Ammonia is primarily removed by microbiological nitrification to nitrate. Nitrification requires 2.0 mg/l or greater dissolved oxygen concentration for optimum performance. Inorganic carbon (Alkalinity) is required by the nitrifying bacteria and nitrification becomes limited at a total carbonate alkalinity of <60-80 mg/L. One sign of an alkalinity limitation for nitrification is the buildup of nitrite about 1-2 mg/L.

Nitrification can be increased (resulting the decrease in ammonia) by raising the dissolved oxygen concentration and by adding alkalinity but nothing can be done about low temperature.

RE: What is the reason for ammonia increase after activated sludge treatment?

dswolf — Sun, 07 Oct 2007 10:48:04 GMT

Please clarify the influent sampling location(s).

How do you manage waste biosolids (anaerobic digestion)?
A possible source of ammonia is anaerobic digester supernatant being redirected to your aeration basin.

-David

What is the reason for ammonia increase after activated sludge treatment?

ahawater — Sun, 07 Oct 2007 08:46:37 GMT

In a activated sludge process, BOD influent concentration is from 3600-10000 mg/l, average is 6000 mg/l. BOD and COD ratio is 0.43-0.7. F/M in the aeration tank is from 0.5 to 1.3. Average F/M is 0.7. BOD and COD removal percentage in the activated sludge process is very high, over 95%. The performance of aeration tank seems good. Ammonia concentration in the influent is from 0.8-7.9 mg/l, average concentration is 4.6 mg/l. But effluent of clarifier ammonia concentration is much higher than the influent. The range is from 8.6-42.1 mg/l, average is 24.4 mg/l.

Why does the ammonia concentration increase? Is the F/M ratio too high? Please help me identify the reasons.

Thanks.