The key regulative parameters in pilot-scale IC reactor for effective incineration landfill leachate treatment: Focus on the process performance and microbial community

Abstract

Anaerobic digestion is a promising sustainable method for treating highly concentrated organic wastewater from the point of energy recovery. In this study, a pilot-scale internal circulation (IC) reactor was constructed to investigate the key regulative parameters that guaranteed the stable and efficient treatment of incineration leachate. The IC reactor was operated for 77 d by feeding real incineration leachate. With an organic load rate (OLR) of 30 kg/ (m3·d) and an influent pH value of 7.5, the reactor achieved its highest organic removal loading rate (ORLR) and biogas yield of 21 kg/ (m3·d) and 6.3 m3/d, respectively. The kinetic analysis confirmed that the two key parameters that significantly correlated (P < 0.05) with the methane yield and Rmax of sludge were OLR and influent pH value. Key enzyme activity of F420 increased 33.2 % when OLR was raised, but decreased by 5.6 % when influent pH was lowered to 6.8, further demonstrating the need for control over these two operational parameters of IC reactor. High-throughput sequencing results indicated that acetotrophic methanogen Methanosaeta had an overwhelming relative abundance of over 47.2 % in the entire community of all sludge samples. Nevertheless, the enrichment of unclassified_Bacteroidales and Methanobacterium strengthened hydrogenotrophic methanogenesis (HM) with step raise of OLR to 30 kg/ (m3·d), then increased the methane production potential and F420 activity of sludge. This study proposed a referable regulation method for the treatment of the actual landfill leachate via IC reactor.