Long-term performance study applying a tandem AnSBR-ASBR to treat wastewater containing N, N-dimethylformamide: Sludge physicochemical properties, microecology, and functional genes

Abstract

The effective treatment of industrial pollutant N, N-dimethylformamide (DMF) containing wastewater is a matter of worldwide concern. This study investigated the performance and microecology of anaerobic granular sludge (AGS) and aerobic sludge (AS) in treating DMF wastewater. It was also explored the degradation pathways of DMF in an anaerobic sequencing batch reactor series aerobic sequencing batch reactor (AnSBR-ASBR). Results showed that 5 mg/L DMF facilitated the degradation of chemical oxygen demand (COD) by AGS with AS, while 100 mg/L DMF reduced the efficiency of AS. The physicochemical properties of the sludge showed that the polysaccharide and protein levels in extracellular polymeric substances and key enzyme activity (acetate kinase, coenzyme F420) deteriorated when DMF increased from 25 to 100 mg/L. As the DMF dose increased (0–100 mg/L), the Euryarchaeota abundance in the AGS decreased from 28.41% to 11.06%, and the predominant methanogenic pathway shifted from a combination of aceticlastic methanogenesis (AM) and hydrogenotrophic methanogenesis (HM) to HM. The metabolic pathway to effectively remove DMF was as follows: hydrolysis of DMF to dimethylamine, methylamine, and finally mineralisation to CO2. The abundance of dmd-tmd, a functional gene encoding dimethylamine/trimethylamine dehydrogenase, increased as the DMF increased in the AS. This study systematically examined the operating efficiency and stability of the AnSBR-ASBR, and summarized the AGS and AS stress response, microbial community evolution, key metabolic pathways to DMF, also provided useful information for the treatment of industrial wastewater containing DMF.