Inhibition of the Nitrification Process of Activated Sludge Micro-Organism by Scrubber Water from an Industrial Flue Gas Cleaning Process.

The microbial transformation of ammonia to nitrate, the nitrification, is a central process in the nitrogen biogeochemical cycle. In a modern wastewater treatment plant, the nitrification process is a key process in the removal of nitrogen and inhibitory compounds in sewage can seriously affect the nitrogen removal. A major sewage cleaning plant in the southern part of Denmark is a recipient of industrial sewage from a major fish meal industry. Severe nitrification inhibition was observed in scrubber water from an incineration of process air, and the processes that lead to the production were stopped. In order to investigate the relation between incineration temperatures and the production of inhibitory compounds, the process air was burned at temperatures from 800°C to 1000°C. The termically affected condensate was collected and the nitrification inhibition effect of the condensate was tested using active sludge from the municipal wastewater cleaning plant. The investigation showed that it is possible to reduce the nitrification inhibition effect considerably by raising the incineration temperature from 800°C to 850°C and in some cases to 900°C. The investigation also showed that a further rise in the temperature beyond 850°C and in some cases 900°C, is unnecessary.