Effects of sewage sludge and refuse composition on the rate of degradation and leachate quality of co-disposed waste in a water deficient environment

Abstract

At the Goudkoppies landfill to the south-west of Johannesburg co-disposal is part of the landfill operation. Laboratory and field tests were conducted to model the landfill processes and the effects of sewage sludge addition. To test the hypothesis that the availability of nitrogen, phosphorus and moisture in the refuse and sewage sludge determine the effects of co-disposal, 19 lysimeters were monitored for 534 days. A factorial design approach was used to choose the lysimeter contents to simulate local landfill conditions. Degradation rates and ammonia concentrations in the leachate were found to depend on the interactions between the nutrients and moisture, rather than on any individual variable. Co-disposal led to a decrease in COD and nickel concentrations, while levels of ammonia and phosphorus in the leachate were elevated in comparison to the refuse-only test. From field tests it was concluded that co-disposal can be practised in the Highveld region without the formation of leachate, while enhancing the rate of refuse stabilisation.

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