An anaerobic dynamic membrane bioreactor for enhancing sludge digestion: Impact of solids retention time on digestion efficacy

An anaerobic dynamic membrane bioreactor (AnDMBR), which enabled the decoupling of hydraulic retention time (HRT) and solids retention time (SRT), was used for enhancing sludge digestion, with the associated mechanisms elucidated. With the increase of SRT, the biogas production and sludge reduction rate were both enhanced. The specific biogas production and volatile solids (VS) reduction rate were improved to 0.79 L/g VS and 55.9% under SRT 50 d, respectively. Microbial community analysis revealed that Chloroflexi, which is capable of degrading metabolites and dead cells, was enriched at longer SRT. Further analysis showed that both acetoclastic and hydrogenotrophic methanogenesis contributed to the enhanced biogas production under higher SRT compared to the dominance of acetoclastic methanogenesis under lower SRT. The enhanced utilization of organic matter and acetate at longer SRT further confirmed the mechanisms. The results highlighted the potential of AnDMBR for high-efficient sludge digestion.