Concerns about micropollutant in wastewater treatment effluent is increasing during the past decade due to their potential adverse environmental effects. It has been hypothesized that ammonia-oxidizing bacteria (AOB) were responsible for micropollutant biotransformation, which is crucial for micropollutant removal. Both inhibition studies and pure culture studies have been performed to test this hypothesis. By inhibiting ammonia oxidation in nitrifying activated sludge (NAS), the biotransformation of a number of micropollutants was inhibited to different extents, which was restored when the ammonia oxidation activity resumed. However, when using pure AOB cultures, such as <i>Nitrosomonas europaea</i>, only couple of those inhibited compounds were biotransformed. Such discrepancy might due to that the tested pure cultures were not the same as those in NAS, and the microorganisms dependently growing with AOB, such as nitrite-oxidizing bacteria (NOB) were not taken into consideration. Therefore, the objective of this study is to investigate the contribution of more environmental relevant nitrifiers to micropollutant biotransformation using a nitrifying community enriched from biofilm of a nitrification tower in a local wastewater treatment plant. We inoculated biofilm samples in basal medium without organic carbon added. Ammonium was supplied upon depletion. After about 8-months’ enrichment, we obtained a nitrifiing enrichment culture with 75.9% AOB and 11.4% NOB in the community based on quantitative PCR detection. The ammonia consumption rate reached 0.29mM/h, and COD declined to 30mg/L. We then investigated micropollutant biotransformation by this nitrifying enrichment culture. We used 9 micropollutants whose biotransformation were previously observed to be inhibited by inhibitor (i.e., allythiourea and octyne) treatment to NAS. Results showed that the enrichment culture was able to degrade more than 75% of Levetiracetam, 55% of Fenhexamid and 30.14% of Rufinamide, while all of the three compounds cannot be degraded by <i>Nitrosomonas europaea </i>pure culture. This led to two hypotheses: i) the AOB species in this enrichment culture have different micropollutant biotransformation capacities; ii) the co-existing microorganisms also contributed to the biotransformation of the three compounds. The community structure analysis is on-going to elucidate the contributions of different community members to the micropollutant biotransformation.

Micropollutant biotransformation by a nitrifying community enriched from biofilm of a nitrification trickling tower

254th National Meeting (2017)

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