The Nitration and Denitration reaction alternately in a activated sludge system

Dear all,

The stripping sour water is treated by activated sludge to be the make-up water for cooling tower, the NH3-N reduction rate is improved in the past 1 month, we think the loading of COD is reduced maybe, and that make the nitrifying bacteria to be the dominant strains. The strange is the NH3-N reduction reaction , the nitration and denitration reaction alternately in a activated sludge system (data as the attachment) .

1.Is the loading of COD reduced ( from about 600 ppm reduce to 300 ppm), and to trigger the nitration?
   (a) the activated sludge system is 8,000 M3, the MLSS is about 2,500~3,000 ppm.
   (b) the inflow is about 4,000 M3/D.

2.The NH3-N react to be NO3-N (nitrate is produce), and alternately to denitration (nitrate is disappear )in a few days?

Thanks.

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Taxonomy

• Cooling Boiler & Wastewater
• Cooling Systems
• Activated Sludge
• Utility Boiler and Cooling Water Treatment
• waste activated sludge

5 Answers

1. Dear Lin,

   It is important know the lab analysis of the inlet and outlet to we can think in any possible option.

   We could think that you can have some aerobic and some anaerrobic zones in this aeration tank.

   Regards,

   Orlando D. Gutiérrez Coronado

2. For oxidation of ammonia to nitrite then nitrate, you need 3 things.  

   1) The correct bacteria.  These need to be replaced if they are lost from a plant.  They have to be freshly made and they lose their viability on storage.  These are not the same as freeze-dried bacteria.

   2) Free oxygen throughout the plant because the bacteria which oxidise are strict aerobes

   3) bicarbonate.  Because the bacteria fix their carbon from carbonate, if that becomes depleted then they are unable to grow.

   Loss of oxygen inhibits the growth of the bacteria but they will recover if oxygen is only lost for a short time.   

3. What was dissolved oxygen levels, there did not seem to be any ammonia nitrification? Also alkalinity and pH were low on occasion, these will be key to sustain nitrification, something is happening but not consistent? Something else inhibiting nitrifiers?

   1 Comment

   1. 1.The DO is about 4 ppm.

      2.The TKN of inflow is 30~40 ppm, the TKN of effluent is 4 ppm, the NH3-N is nitrification.

      3.The pH is about 7, and the cresol (about 30 ppm) maybe the inhibitor, but we still need to check.

4.  There was no good nitrification in the process. As the HRT (hydraulic retention time) is high and sufficient, there may be insufficient oxygen in the process. 

   1 Comment

   1. 1.The DO is ​about 4 ​ppm, the O2 should not the matter.

      2.The TKN of ​inflow is 30~40 ​ppm, the TKN of ​effluent is 4 ​ppm, the NH3-N ​is nitrification in  ​the last ​month.

5. The reduction in COD from 600 to 300 is making whatever O2 you are adding more efficient for the metabolic activity of the Nitrifiers as the standard minimum ratio of O2 to NH3-N is 4.5 to 1 the same ratio for the alkalinity required.