[Effects of the leachate recirculation with pH adjusted on anaerobic landfill].

The landfill gas, biochemical indications of leachate and toxicity of leachate had been investigated in two simulated anaerobic bioreactors. After 40 days of simulated rainfall, one reactor was recharged with the original leachate directly while the other one was recharged with the adjusted leachate of which the pH was changed to 7.5. The results indicate that during the simulated rainfall the garbage is acidified rapidly with the pH value decreased to 5.21. Recharged with the original leachate, acidification of the landfill layer is deteriorated. Recirculation of the adjusted leachate, which can produce methane rapidly, can also remove organic pollutants significantly. At the 80th day methane production rate is up to 64.8%. After 170 days, the removal of BOD5 comes to 93.5% while the removal of COD is 89.1%. Furthermore, the biological toxicity of leachate decreases significantly and the semi-lethal concentration of leachate to tetrahymena rises to 3.27% from 0.24% within 24 hours.