Effect of saline water and sludge addition on biodegradation of municipal solid waste in bioreactor landfills

Bioreactor landfills require sufficient moisture to optimize the biodegradation processes and methane generation. In arid regions, this is problematic given the lack of fresh water supplies. Saline water can be used but may inhibit the biodegradation of the municipal solid waste (MSW) in landfills. Sludge may be used to enhance the biodegradation of MSW under saline conditions. For this study, two groups of laboratory-scale bioreactor cells were used to study the impact of saline water and sludge addition on the biodegradation of MSW in bioreactor landfills. The first group ( four bioreactors) operated without sludge addition. The second group ( four bioreactors) operated with the addition of sludge. The salt concentrations in the two groups were 0, 0.5, 1 and 3% (w/v), respectively. All bioreactors were operated at neutral pH levels with leachate recycling. The methane yield was 70.6, 61.7 and 47.5 L kg(-1) dry waste for bioreactors R1, R2 and R4, respectively; and 84.7, 78.7, 72.6 and 59 L kg(-1) dry waste for bioreactors R5, R6, R7 and R8, respectively. The high salt content (3%) inhibited the MSW biodegradation as evidenced by the methane yield, the percentage reduction in leachate concentration and the settlement that occurred during the study. Sludge addition was able to improve the methane yield at all salt concentrations.