Effect of ammonia oxidizing bacteria communities in enriched nitrifying activated sludge and sludge from full scale wastewater treatment plants on degradation of 17α-ethynylestradiol via co-metabolism

Abstract

Ammonia oxidizing bacteria (AOB) has been reported for their capability of degrading several recalcitrant organic pollutants during ammonia oxidation by co-metabolism mechanism. 17α-ethynylestradiol (EE2) is a synthetic female hormone that is the main component in oral contraceptive pill. EE2 can be released via human excretion causing the municipal sewage being an important source of EE2. Previous studies suggested that EE2 is persistent in contact with activated sludge but can be degraded by AOB in nitrifying sludge (NAS) during the oxidation of ammonia. However, all of the previous studies so far focused only on the AOB obtained from enriched NAS with extremely high ammonia levels. Therefore, this study, focused on the degradation patterns of EE2 (10 mg/L) by enriched NASs (with initial ammonium concentrations of 2 and 30 mM) and sludge from full-scale wastewater treatment plants (WWTPs) (two municipal and two industrial WWTPs) of which were different in AOB communities. AOB communities in enriched NASs from 2 and 30 mM reactors differed significantly. NASs from both reactors exhibited different degradation patterns of EE2. NAS containing AOB with high affinity to ammonia (Nitrosomonas oligotropha cluster) was able to degrade EE2 more than that with low affinity to ammonia (Nitrosomonas europaea cluster). In municipal sludge (MWWTP-A and MWWTP-B) AOB played a major role in EE2 degradation while small amounts of EE2 were degraded by heterotrophs. In contrast, in industrial sludge, heterotrophs were the one that degraded EE2 considerably. Results tended to showed that sludge with different AOB communities exhibited different degradation patterns of EE2. AOB with high affinity to ammonia (Unknown Nitrosomonas cluster, Nitrosomonas communis cluster and Nitrosomonas oligotropha cluster; MWWTPA, MWWTP-B, IWWTP-B) was able to degrade more EE2 than AOB with low affinity to ammonia (Nitrosomonas europaea-Nitrosomonas mobilis cluster, IWWTP-A). However, it is hard to say this conclusion exactly as heterotrophs also played significant role in sludge from full-scale WWTPs and can not be neglected.