Differences of bacterial communities in two full-scale A2/O municipal wastewater treatment plants and their effects on effluent total nitrogen removal

Abstract

Bacterial communities and functional bacteria played a vital role in the biological removal of nitrogen in wastewater. Bacterial communities, nitrogen removal and their correlationship were compared and analyzed in two full-scale anaerobic/anoxic/aerobic (A2/O) municipal wastewater treatment plants (WWTPs) (assigned as D and X plants). Illumina high-throughput sequencing results showed remarkable differences in the bacterial communities’ diversity were found between these two WWTPs. Significant differences in species diversity existed in anaerobic, anoxic, and aerobic tanks in X plant, while no significant differences were found among the D plant’s tanks. In the aerobic tanks of X and D plants, nitrifying bacteria genera accounted for 5.29% and 1.57%, respectively, while aerobic denitrifying bacteria accounted for 0.64% and 0.47%. In the two plants’ anoxic tanks, denitrifying bacteria accounted for 1.14% and 1.64%, respectively. During the two months of monitoring, average effluent total nitrogen (TN) concentrations of X and D plants were 14.85 ± 1.85 and 17.66 ± 0.92 mg/L, respectively, and the former was satisfied with the stringent discharge standard. Effluent TN was significantly negatively correlated with Nitrospira, Denitrobacter, Thauera, Comamonas and Dechloromonas (P<0.05) and positively correlated with Paracoccus and Dokdonella (P<0.05). Overall, species diversity in each functional tank of X plant was remarkably different, and functional genera were more abundant in X plant than that in the D plant, which might be one reason for the lower effluent TN concentrations in the two WWTPs.