ABSTRACT
In this unit, primary and secondary sludges are compared, followed by methods of sludge thickening. The mass volume relationship is derived, and equations to find the specific gravity of sludge with varying types of solids and moisture content are shown. Sludge stabilization is defined and anaerobic sludge digestion is detailed. The stages of anaerobic sludge digestion and the equation for finding the capacity of a digestor is illustrated with solved example problems. The monitoring of volatile solids and alkalinity levels and the composition of gases produced in the operation of an anaerobic sludge digester are discussed. Calculations for finding volatile solids reduction are shown. The various methods of sludge dewatering, including vacuum and pressure filtration and centrifugation, are discussed. A section on the various methods of sludge disposal, including sludge as a soil filler, sludge composting, drying beds, incineration and disposal to sea, is included.
