Improving process stability, biogas production and energy recovery using two-stage mesophilic anaerobic codigestion of rice wastewater with cow dung slurry

摘要

Two-stage anaerobic digestion (TSAD) is a promising strategy for process-specific operation of the distinctive stages of anaerobic digestion to ultimately enhance the process yield and stability. TSAD aids in reducing the inhibitory effects of acidogenesis on methanogenesis and maintains the harmony of the overall process. TSAD of rice wastewater is examined in the present study. Single-stage mono digestion of rice wastewater confronts volatile fatty acid (VFA) accumulation and process instability mainly due to unbalanced C/N ratio, high organic load and biodegradability. This study is an attempt to resolve the glitches by adopting two-stage anaerobic codigestion (TSACoD) with cow dung slurry (CDS) for enhanced process stability, performance and digestate quality. TSACoD reduced the negative interference of VFA production on the performance of methanogens and increased the yield by 58.69% and the total energy recovery by 1.58 times. The optimal ratio of RWW: CDS was observed to be 25:75 (%v/v) and the highest yield of biohydrogen and biomethane was 7.58 mL H_2/g VS and 292 mL CH4_/g VS respectively. This study provides insights on the crucial process conditions to be maintained and monitored for effective anaerobic digestion of highly biodegradable substrates.