A microscopic examination won't help you much with nitrifiers. Nitrosommonas and Nitrobacter are the only ones easily identified and there are other bacteria that are responsible for this. With that said there are other things you can look at that are beneficial. It may help though in the overall performance of the plant (is the long SRT hurting you?) Is there a high amount of septicity/ organic acids (these grow zooglea, tetrads, and certain filaments) which may be inhibiting nitrification.

One easy check to see if the long SRT is causing a spike is to check the orthophoshate throughout the plant. If you see a large increase toward the end of the aeration tank along with an increase in ammonia it's possible the bacteria are starving and cell lysis is responsible (this re-releases the nutrients).

I don't quite understand your analytical data. 10:1 BOD/ Total N in the influent you'll be short on nitrogen. 5 mg/L alkalinity at the end of the process is way too low. You need at least >50. It's possible the alkalinity is the limiting factor here (this is the food source for the nitrifiers). Increase this with chemical addition of alkalinity and it's possible that may do the trick.

best regards,

Ryan

disregard the part about the BOD/N ratio. There's a big surplus of nitrogen. I misread that as well as the as the meq/L. What does that convert to as mg/L alkalinity as CaC3?

Thank you all.
More info; my ORP(oxdation reduction pt) sensor shows 250 mV which i asume is good process condition. Further i am also using NaOH (29%) to control the pH level of the MLSS.I am not quite sure if this will inhibit nitrification process by forming some inhibiting compounds. Large SRT is not a problem for me , but if it is distroying my nitrification than i had di reduce it.
@ SludgAge;  my plant doesnot have chemical or any biological phosphorus removal process like EBPR or any (of course only for assimilation of COD removal heterotrops) and inlet-outlet  phosphate is  6 and 2.5 mg/L respectively. And there are no any septic sludge , wastewater is normal municipal wastewater.

Any reason for not having nitrification OR is it just a high sludge age that could be the cause.

Kind regards
BHP

I agree with DS. I'd test amines especially.

What TKN values do you have for your influent/effluent?

Hi BHP,

Liangs' remark on the HRT is quite relevant over here; it could be that the HRT is too short compared to the ammonium oxidation rate, which I expect to be on the low side in this case. another possibility (alone or in combination with the foregoing) is that the affinity for ammonium of the AOB (Ammonia Oxidising Bacteria) is lowered due to some toxicant.

So we are talking about alkalinity around 155 mg/l?  I think that the use of NaOH may be affecting the nitrification rate.  Or else some type of inhibitor has entered the plant and is suppressing your nitrifiers.  

40 days is rather long for a SRT, your F/M ratio indicates a high MLSS concentration, and combined they suggest too many bugs for the load of food.  I suggest double checking your D.O. levels throughout aeration, checking nitrate conc in plant effluent, and considering why you carry such a high level of solids in your plant's inventory.  Your set up suggests that you treat high/variable BOD loadings, or else there are shock loadings from pH, BOD, toxics, or temperature.  Are any of these factors at your plant?  Did you used to have foam problems and resolved them by changing the process to what it is now?  

The bottom line appears to be poor metabolic reactions by your bugs.  What is the F/M ratio suggested for your plant?  If it is different from what you are operating at today, why is that?  Good luck!

~Eric

Also based on the nitrate in your effluent it looks like you're getting some degree of nitrification.