Abstract
Physicochemical coagulation process is one of the most popular techniques to remove phosphorus in wastewater treatment processes where the activated sludge was used. However, the influence of coagulants on biological nitrification is not elucidated in detail. Then, the influence of polyferric sulfate as coagulant on nitrogen conversion by ammonia oxidizer was investigated by using water quality test and transcript analysis. In the batch operation of the nitrification-denitrification process, Fe/P molar ratios of 0, 1 and 5 were tested. Phosphorus concentration was immediately decreased at the beginning of the experiment in the case of Fe/P = 1 and 5, however, 40% of ammonia remained in the case of Fe/P = 5. In this case, the amoA mRNA expression was suppressed because of the excessive addition of polyferric sulfate. Furthermore, T-RFLP profiles of amoA mRNA showed that polyferric sulfate affects various species of ammonia oxidizer, and some species suffer a great loss.
