1. Check that the plant meets following operating conditions necessary for successful nitrification:
· Temperature
Temperature has a significant influence on the process. The optimal range is narrow - between 25°C and 30°C. For every 10°C drop in temperature the activity will be reduced by 50%. No activity will occur at temperatures below 7°C. The temperature should not rise above 35°C.
· Dissolved Oxygen
The process is heavily dependent on the dissolved oxygen concentration. Levels above 2 mg/L are ideal. When the level drops below 1 mg/L, oxygen becomes the limiting nutrient and the process slows down and eventually stops altogether.
· Alkalinity
The process consumes a large amount of alkalinity. Ideally the alkalinity needs to be greater than 200 units (measured as calcium carbonate).
· pH
The optimal range is narrow and lies between 7.5 and 8.5.
· Salinity
Ideally the level of salinity (measured as mg/L salt) needs to be less than 1000. The process will occur at higher levels but the activity will be greatly reduced. Up to 75% of the activity can be lost at levels above 3000.
· BOD
The process occurs best in environments with a low BOD level. Levels below 50 mg/L are ideal. At levels above 200mg/L the nitrifying bacteria are likely to be outcompeted for oxygen by faster growing genera, thus slowing the nitrification process.
· Heavy Metals
Heavy metals have a negative effect on the process. The total absence of heavy metals will help to ensure maximum activity.
· Other Factors
The process is most efficient when the biomass is attached to support media, thus providing sufficient retention time and adequate mixing. In activated sludge plants a sludge age of 8 to 10 days is desirable but this may be able to be reduced by maintenance dosing and other factors.
