Novel electro-assisted micro-aerobic cathode biological technology induces oxidative demethylation of N, N-dimethylformamide for efficient ammonification of refractory membrane-making wastewater

Recalcitrant and toxicological membrane-making wastewater displays negative impacts on environment, and this is difficult to treat efficiently using conventional hydrolytic acidification. In this study, a novel electro-assisted biological reactor with micro-aerobic cathode (EABR-MAC) was developed to improve the biodegradation and ammonification of N, N-dimethylformamide (DMF) in membrane-making wastewater, and the metabolic mechanism using metagenomic sequencing as comprehensively illustrated. The results showed that EABR-MAC significantly improved the ammonification of refractory organonitrogen and promoted DMF oxidative degradation by driving the electron transferred to the cathode. Additionally, the inhibition rates of oxygen uptake rate and nitrification in EABR-MAC were both lower under different cathode aeration frequency conditions. Microbial community analysis indicated that the functional fermentation bacteria and exoelectrogens, which were correlated with COD removal, ammonification, and detoxification, were significantly enriched upon electrostimulation, and the positive biological connections increased to form highly connected communities instead of competition. The functional genes revealed that EABR-MAC forcefully intervened with the metabolic pathway, so that DMF converted to formamide and ammonia by oxidative demethylation and formamide hydrolysis. The results of this study provide a promising strategy for efficient conversion of organonitrogen into ammonia nitrogen, and offer a new insight into the effects of electrostimulation on microbial metabolism. [Display omitted] The recalcitrant and toxicological membrane-making wastewater displayed negative impacts on human health and environment due to its serious poisonous effects such as embryotoxicity, hepatotoxicity, teratogenicity, and carcinogenicity. The conventional hydrolytic acidification technology was difficult to remove the organic nitrogen pollutants and reduce the toxicity efficiently. In response to this issue, a novel electro-assisted biological reactor with micro-aerobic cathode was investigated to drive biotic oxidation of N, N-dimethylformamide, to speed up the ammonification rate of refractory organonitrogen by targeted regulation of key functional microbiota, genes, and metabolic pathways. This study would provide a feasible strategy for efficient conversion of refractory organonitrogen, to benefit the advanced treatment of carbon and nitrogen in subsequent process. •A nove