Impact of UASB start-up and different HRT on treatment effect of old landfill leachate

Inoculating with activited sludge as the seed material in UASB reactor, the treatment efficiency of municipal landfill leachate (13 years old) was investigated. Keeping the influent COD concentration unchanged as well as a gradual reduction of the HRT, 1~3 mm anaerobic granular sludge can be obtained at volumetric loading rate of 40 g COD/(L·d). The final biogas production was 100 L/d and methane content were between 60%~70%, COD removal efficiency remained at 90%, the MLSS of bottom of the sludge layer was 81 g/L. The best treatment effect was at HRT of 48 h comparing the HRT at 6, 12, 24, 48 and 72 h, COD removal rate reached a maximum of 35%.