Microbial community distribution and extracellular enzyme activities in leach bed reactor treating food waste: Effect of different leachate recirculation practices

• Continuous leachate recirculation is ideal for food waste hydrolysis in LBRs.
• L/S ratio of 1:1 and buffer addition selectively enriches hydrolyzing bacteria.
• Key enzymes in LBRs are α-mannosidase, α-fucosidase, lipase and β-galactosidase.
• Lactobacillus sp. was found to be predominant in food waste treating LBRs.

This study aimed at understanding the relationship between microbial community and extracellular enzyme activities of leach bed reactor (LBR) treating food waste under different leachate recirculation practices (once per day and continuous) and liquid to solid (L/S) ratios (1:1 and 0.5:1). Microbial community analysis using PCR-DGGE revealed that Lactobacillus sp., Bifidobacter sp., and Proteobacteria were the most abundant species. Number of phylotypes was higher in LBRs with intermittent recirculation; whereas, lower number of phylotypes dominated by the key players of degradation was observed with continuous recirculation. The L/S ratio of 1:1 significantly enhanced the volatile solids removal compared with 0.5:1; however, this effect was insignificant under once a day leachate recirculation. Continuous leachate recirculation with 1:1 L/S ratio significantly improved the organic leaching (240 g COD/kg volatile solid) and showed distinct extracellular enzyme activities suitable for food waste acidogenesis.