Denitrification of leachate using composted domestic waste at different levels of stability: a batch test investigation

This study presents an investigation into the viability of pre-treated general wastes at dif?ferent degrees of stability as carbon sources for in-situ bio-denitrification at landfills. Do?mestic waste was composted and stabilised for eight (8) and sixteen (16) weeks within two different mini-landfill cells located at the Bisasar Road landfill, Durban, South Africa. Eight substrate categories were developed using the composted domestic wastes and com?mercial garden refuse with stand-alone and combinatory approaches. Adopting small-scale dynamic batch tests, landfill leachate, treated with 500 mg/l nitrate concentration level, was used to comparatively assess the denitrification efficiency of the stand-alone and aug?mented substrates. Results demonstrate that substrates based on domestic waste were unable to independently sustain the denitrification process. Full denitrification was only achieved on the augmented substrates. Kinetic analyses show that a zero-order reaction better describes the denitrification rate independent of the nitrate concentration. These results thus elucidate the benefits inherent in adopting augmented substrates in treating landfill leachate.