ABSTRACT
This chapter describes the various sludge reduction processes by means of thermal treatment viz. complete combustion, incomplete combustion and pyrolysis processes. It discusses the usage of several types of thermal processes, viz. multiple hearth incineration, fluidised bed incineration, rotary kiln incineration and emerging incineration technologies, flash combustion, co-incineration, wet air oxidation and co-pyrolysis. The multiple hearth process converts dewatered sludge cake to an inert ash. Sludges processed by thermal reduction are usually dewatered untreated sludges. It is normally unnecessary to stabilise sludge before incineration. The hottest temperatures are on the middle hearths where the sludge burns and where auxiliary fuel is also burned as necessary to warm up the furnace and to sustain combustion. Application of organic residuals such as municipal wastewater sludge to land is being widely promoted as a cost-effective disposal alternative, with agricultural, forest, and range lands as well as land reclamation sites increasingly used for land application.
