In Yogyakarta, 400-500 ton/day of municipal solid waste (MSW) is dumped in Piyungan Landfill Site. High organic and water content of the MSW releases a considerable amount of leachate as the aqueous effluent generated from MSW accumulation by the rain water percolation and thewater content of the waste itself. Yogyakarta City Authority has strived to control leachate release into environment by means of putting geo membrane lining and dedicating two hectare area foreleven retention ponds. However, the increasing amount of incoming MSW has increased the risks of high concentration leachate discharge regardless the current preventive efforts. This study aimed to develop mathematical model to predict the leachate distribution patterns into the water streams. The model served as a predictive tool for the city authority to anticipate the possibility of leachate pollution into the water streams and take action accordingly. The first part of the model predicted the fluctuation of the pollutant concentration in the ponds’ effluent as the starting point of the leachate discharge. The second part of the model estimated the extent of leachate diffusion in the streams into which it was discharged. Model constants were determined by fitting the model with the field data collected during August 2015-August 2016. The sampling points covered the radius of 2 kilometers around Piyungan landfill site. The sampling period included the data during dry and rainy seasons to capture the lowest and highest concentration of leachate in the retention ponds.

Keywords: leachate; landfill site; municipal solid waste; mathematical model; water pollution


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