Inhibitory effect of phenol on wastewater ammonification

This study aimed to elucidate inhibitory effect of phenol on ammonification of dissolved organic nitrogen (DON) in wastewater. Laboratory incubation experiments were conducted using primary and secondary effluent samples spiked with phenol (100-1000 mg/L) and inoculated with mixed cultures, pure strains of phenol-degrading bacteria (Acinetobacter sp. and Pseudomonas putida F1), and/or an ammonia oxidizing bacterium (Nitrosomonas europaea). DON concentration was monitored with incubation time. Phenol suppressed the ammonification rate of DON up to 62.9%. No or minimal ammonification inhibition was observed at 100 mg/L of phenol while the inhibition increased with increasing phenol concentration from 250 to 1000 mg/L. The inhibition was curtailed by the presence of the phenol-degrading bacteria. DON was ammonified in the samples inoculated with only N. europaea and the ammonification was also inhibited by phenol. The findings suggest that high phenol in wastewater could result in low ammonification and high DON in the effluent.