Biological removal of ammonium and p-cresol linked to nitrite reduction

The metabolic capability of denitrifying sludge to oxidize ammonium and p-cresol was evaluated in batch cultures. Ammonium oxidation was studied in presence of nitrite and/or p-cresol by 55 hours. At 50 mg/L NH4 + -N and 76 mg/L NO2 -N, the substrates were consumed at 100% and 95%, respectively, being N2 the product. At 50 mg/L NH4 + -N and 133 mg/L NO2 -N, the consumption efficiencies decreased to 96% and 70%, respectively. The increase in nitrite concentration affected the ammonium oxidation rate. Nonetheless, the N2 production rate did not change. In organotrophic denitrification, the p-cresol oxidation rate was slower than ammonium oxidation. In litho-organotrophic cultures, the p-cresol and ammonium were oxidized simultaneously but at different specific rates, being the main products, N2 and HCO3 . Finally, this is the first work reporting the simultaneous oxidation of ammonium and p-cresol linked to nitrite reduction.