Abstract:
Laboratory-scale digesters were operated to study the effect of leachate circulation on
biogas production. Two reactors (20L) were performed using market waste and rice straw
(< imm particle size) in 1:3 ratio. One reactor was operated with leachate circulation in
once a day and other one was performed in twice a day (12 hrs interval). After filling the
reactors with required total solid level (20%), the digested material of a biogas digester
(operated by market waste alone) were added to reactors in equal quantity as inoculums
and reactors were sealed. Biogas production, methane content, temperature and pressure
were measured in daily and pH, chemical oxygen demand (COD) in leachate samples were
regularly monitored in once a week. After 100 days of anaerobic digestion, it was observed
that the gas production, pH, COD in reactor 1 (leachate circulation in twice a day) was
better than the reactor 2 (leachate circulation in once a day). The initial measurable gas
production was observed during 4-5 days after filling the reactors. After ~ 40 days, the
maximum gas amount was produced and it was gradually decreased. The comparatively
higher gas production was noted in reactor 1. Total gas production in two reactors
were 40714 and 36325 cm3/kg of dry matter, respectively. When the leachate circulate
frequently, COD were reduced due to consuming the volatile fatty acid by methanogenesis.
Based on this study it can be concluded the leachate circulation influence the rate of biogas
production while consuming the COD in leachate.
