(Micro) nanoplastics promote the risk of antibiotic resistance gene propagation in biological phosphorus removal system.

Microplastics (MPs), nanoplastics (NPs) and antibiotic resistance genes (ARGs), as emerging pollutants, have been frequently detected in wastewater treatment plants. However, the behavior of phosphorus and ARGs under MP and NP (MP/NP) pressure in biological phosphorus removal (BPR) system is still unknown. This study investigated the effects of MP/NPs on phosphorus removal and ARGs propagation in BPR system. Results showed that MP/NPs had no influence on phosphorus removal, but significantly promoted the amplification of tetracycline resistance genes (TRGs). Moreover, the TRG abundance were more facilitated by MPs than NPs, and the TRGs of efflux pump and enzymatic modification mechanism were mainly enriched. Meanwhile, MP/NPs increased the transmission risk of multiple resistance genes and mobile gene elements (MGEs). Microbial communities demonstrated the main polyphosphate accumulating organisms shifted from Acinetobacter to unclassified_Gammaproteobacteria, which explained why phosphorus removal efficiency was unaffected with MP/NP addition. Correlation analysis revealed there was no significant correlation between ARGs and MGEs (intI1 and intI2), but the abundances of potential hosts of ARGs were significantly increased with MP/NP addition, implying microbial community structure changes rather than gene horizontal transfer was the main factor promoting ARG propagation under MP/NP pressure.

The occurrence and fate of siloxanes in wastewater treatment plant in Harbin, China.

The occurrence and fate of four cyclic (D3 to D6) and 10 linear (L5 to L14) siloxanes were investigated in influent and effluent wastewater, sludge from a wastewater treatment plant (WWTP), and surrounding air and soil within the WWTP in Harbin, Northeast China. The mean concentrations of total siloxanes in influent and effluent were 4780 and 997 ng/L and in excess sludge and aerobic sludge were 25.1 and 32.3 µg/g dw, respectively. The concentrations in air and soil within the WWTP were 243 ng/m(3) and 4960 ng/g dw, respectively. A similar composition profile of siloxanes in influent and sludge suggests their same source. Seasonal variation with concentration was comprehensively studied. It was found that temperature and rainfall are the two important factors for the seasonal variation of siloxanes. Adsorption with sewage sludge was the major way for the removal of siloxanes during the municipal wastewater treatment process. Overall, on a daily basis, the mass loading of the Σsiloxanes into the WWTP, out of the WWTP with the effluent and sludge, were estimated to be 3.0, 0.6 and 1.3 kg, respectively. In general, 21 % of siloxanes were discharged into the receiving body (Songhua River), 43 % of siloxanes were absorbed on sludge, and 36 % of siloxanes were lost during the whole process of WWTP.