Geotechnical aspects of sewage sludge monofills

Abstract

More stringent controls on the quality of wastewater discharges are giving rise to increasing volumes of sewage sludge for disposal. Within the European Community, the disposal of sewage sludge to sea ceased by 1998 under the Urban Wastewater Treatment Directive. Stricter waste disposal legislation and higher landfill taxes are forcing the water industry to look for more efficient disposal strategies. Dedicated sludge-to-landfill operations are presented as a viable option. The sewage sludge is dewatered to the optimum water content for compaction, placed in the landfill in layers and compacted to the maximum dry density, thereby maximising the operational life of the landfill site. The design, construction and long-term performance of such monofills are described. Adequate levels of dewatering for the sludge-to-landfill route can best be achieved at the treatment plant using conventional mechanical dewatering devices, sludge drying beds or thermal drying processes.