Thickening of sewage sludge is one of the most important basic treatment steps of the entire sludge treatment process. For decades thickening of sewage sludge has been accomplished by using either gravity settling in thickeners or in a flotation unit or by mechanical thickening. Flotation and mechanical thickening processes are almost solely used for the thickening of waste activated sludge. In 1998 the former ATV Sub-Committee 3.2 "Stabilisation, Disinfection, Thickening, Dewatering and Conditioning of Sewage Sludges" presented the working report "Thickening of Sewage Sludge". The various procedures and their efficiency and cost-effectiveness have been updated and are now presented in this Advisory Leaflet.
