Multi-routes and mechanisms of biochar in enhancing the fouling resilience in an anaerobic membrane bioreactor during municipal wastewater treatment

Membrane fouling is a daunting challenge in applying anaerobic membrane reactors (AnMBRs). The effects and mechanisms of biochar (BC) in enhancing the fouling resilience of an AnMBR for treating municipal wastewater (MWW) were revealed in this study. During the half-year operation, the twice addition of BC effectively alle-viated membrane fouling through multiple approaches. BC expanded the membrane capacity of AnMBR for wastewater from 720.3 to 1855.4 m3/m2. BC prevented inorganic foulants from precipitating on the membrane surface and enhanced the capacity for organic foulants. The functional groups and protein structures suggested that foulants with lower binding forces were stripped from the membrane surface by BC, while foulants with stronger binding forces were trapped on the membrane, forming a more homogeneous and compact fouling structure. The BC-scrub-effect test indicated that BC detached 71.3% of the cake and 41.6% of the gel foulants. The descent of the transmembrane pressure was divided into fast (0.34 kPa/h) and slow (0.07 kPa/h) foulant release rates, which was attributed to the varied characteristics of composition, spatial distribution and binding forces between foulants from the cake and gel layers. BC significantly enriched functional microbes like Long-ilinea, Acinetobacter and Methanobacterium and stimulated metabolic functions such as Fermentation and Hydro-carbon degradation, thus improving membrane resilience for organics, and resulting in a lower content of soluble organic foulants on the membrane. This study provides a better understanding of the multiple approaches by BC to enhance the fouling resilience of an AnMBR treating MWW.

Automated summary

This study reveals the effect and mechanism of biochar in enhancing the resilience of anaerobic membrane reactors to membrane fouling in treating municipal wastewater. Through multiple approaches, biochar effectively alleviates membrane fouling and improves the treatment capacity for organics. Furthermore, biochar can regulate microbial community and metabolic functions, further enhancing the membrane's resistance.