Phenol inhibition to biological nitrification process

Nitrifying bacteria are easily affected by the surrounding factors and toxic compounds due to their physiological and ecological characteristics. The nitrification inhibition will in turn influence the stability of nitrification process and reduces nitrification efficiency, which may confine the application of denitrification in industrial wastewater treatment. This paper aims to present the author's investigation into the nitrification inhibition of phenol by batch experiments, which can commonly be seen in the industrial wastewater with nitrifying bacteria enriched by the special cultural medium. The results indicate that the phenol concentration was 20 mg/L if calculated in the nitrification inhibition formula under the condition that the extent of inhibition was about 50%. Since the inhibition of phenol to nitrification is by nature non-competitive and reversible, the inhibition can be eliminated through washing and dilution. Furthermore, if the temperature coefficients of phenol are free and the phenol-contained (the extent of nitrification inhibition was 50%) nitrification reaction were 1.09 and 1.15 respectively. Nitrification rate will be more sensitive to temperature change in phenol-contained wastewater, and as a result, proper control of temperature can also promote the counteraction of the inhibition to some extent. In addition, it is also necessary to add heterotrophic bacteria in a specific proportion to pure the nitrifying bacteria, which may produce the similar effect because heterotrophic bacteria help to degrade the phenol and protect the nitrifying bacteria by floc. And finally, the coexistence of phenol and 2,4-dichlorophenol might probably result in the superposition effect. That is perhaps one of the reasons why the treatment efficiency of industrial wastewater be worsening in contrast to the municipal sewage. Thus the nitrification of the industrial wastewater should be paid more attention to.