Leachate drawdown in a lab-scale vacuum-assisted pumping well model with synthetic MSW Available to Purchase

The drawdown performance of conventional leachate pumping wells in municipal solid waste (MSW) landfills is often variable and sometimes unsatisfactory. The integration of vacuum-assisted vertical leachate pumping wells has shown significant potential for improving leachate drawdown performance. However, the improvement in the hydraulic response of MSW during leachate drawdown using vacuum pumping wells has not been quantified. In this study, laboratory-scale model tests were conducted to investigate the desaturation of synthetic MSW using vacuum pumping wells. Both continuous and cyclic vacuum applications with a pressure range from 0 to −10 kPa were tested. The results demonstrated the occurrence of gas bubble instability during leachate drawdown, with a critical pore water pressure for gas bubble destabilisation of approximately 6 kPa. High vacuum pressures could either increase the hydraulic conductivity of the synthetic MSW by way of enhanced gas bubble expulsion or decrease it because of increased MSW compression. The cyclic vacuum application may provide an energy-saving strategy for lowering leachate levels using vacuum pumping wells, as it resulted in nearly the same leachate pumping capacity as that of constant vacuum. The optimal leachate pumping capacity for both constant and cyclic vacuum applications ranged from −6 to −8 kPa.