Insights into long-term effects of amino-functionalized multi-walled carbon nanotubes (MWCNTs-NH2) on the performance, enzymatic activity and microbial community of sequencing batch reactor. (November 2019) - Gao, Mengchun
Abstract: Carbon nanotubes (CNTs) inevitably enter domestic sewage and industrial wastewater with the continuous increase of their production and application field. The potential effect of CNTs on biological wastewater treatment processes has raised wide concerns due to their biotoxicity. In the present study, the performance, microbial community and enzymatic activity of sequencing batch reactors (SBRs) were evaluated under 148-day exposure of amino-functionalized multi-walled CNTs (MWCNTs-NH2 ) at 10 and 30 mg/L. The COD removal efficiency at 10 and 30 mg/L MWCNTs-NH2 gradually reduced from 91.03% and 90.43% on day to 89.11% and 86.70% on day 148, respectively. The NH4 + -N removal efficiency at 10 and 30 mg/L MWCNTs-NH2 gradually reduced from 98.98% and 98.46% on day 1 to 96.65% and 63.39% on day 148, respectively. Compared to 0 mg/L MWCNTs-NH2, the oxygen-utilizing rate, ammonia-oxidizing rate, nitrite-oxidizing rate, nitrite-reducing rate and nitrate-reducing rate at 30 mg/L MWCNTs-NH2 were decreased by 52.35%, 60.58%, 55.12%, 56.56% and 57.42% on day 148, respectively. The microbial reactive oxygen species and lactate dehydrogenase release on day 148 was increased by 59.71% and 55.28% at 30 mg/L MWCNTs-NH2, respectively. The key microbial enzymatic activity related to nitrogen removal decreased with the increase of operation time under MWCNTs-NH2 stress. The relative abundances of Nitrosomonas, Nitrosospira, Nitrospira and some denitrifying bacteria at 10 mg/L MWCNTs-NH2 gradually reduced with an increment in operation time. The changes of nitrogen removal rate, microbial community and enzymatic activity of SBR were related to the time-cumulative nonlinear inhibition effect under long-term exposure. Graphical abstract: Image 1 Highlights: MWCNTs-NH2 inhibited microbial nitrogen removal rates of sequencing batch reactor. MWCNTs-NH2 decreased the microbial enzymatic activities under long-term exposure. The microbial ROS production and LDH release increased under MWCNTs-NH2 stress. MWCNTs-NH2 under long-term exposure exerted obvious change of microbial community. Abstract : The performance, nitrifying and denitrifying rate, enzymatic activity and microbial community of SBR were impacted under long-term exposure of MWCNTs-NH2 .