Sewage Sludge Thermal Processing

Abstract

Different points related to the disposal of sewage sludge are explored: its formation, characteristics, and processing. Four sludge disposal procedures that are currently employed are discussed, i.e., landfilling, recycling in agriculture, incineration, and dumping into the sea. The current trend indicates the increasing interest in sludge incineration. Various technologies for the thermal processing of sewage sludge are lumped in three groups: co-combustion, mono-combustion, and alternative processes. Promising potential for efficient sludge incineration (e.g., mono-combustion or co-combustion with coal) is offered by the fluidized-bed combustors. In difference to coal, sewage sludge has very high contents of water and volatile matter, a high fraction of ash, and appreciable amounts of nitrogen and phosphorus. Of concern in sludge incineration, there are also heavy metals, acid gases (including NO_x), and dioxins and furans.