Evaluating the increased risk of leachate generation resulting from codisposal of sewage sludge in a municipal solid waste landfill in a semi-arid climate

Abstract

Field and laboratory experiments were carried out to determine whether the codisposal of sewage sludge in a municipal solid waste landfill in a semi-arid location would increase the likelihood of leachate generation. Field cells were filled with sludge : refuse mixtures at ratios of 1 : 5.5 and 1:11. A refuse-only cell was also constructed. Leachate collection systems were installed beneath these cells. After one year of operation no leachate had been detected in any of the collection sumps and it was decided to irrigate the cells. Despite extensive irrigation, only one cell, the refuse- only cell, produced any leachate. Profiles of moisture content in the field cells taken two years after construction indicated the moisture content of the waste had in fact decreased, which was attributed to evaporative losses. It is suggested that in semi-arid climates the use of expensive lining systems may not be necessary. Furthermore, the addition of sewage sludge appears to improve the moisture retention capacity of refuse, an observation that was confirmed by the laboratory lysimeter results.