ABSTRACT
Sludge is the name that describes a muddy or slushy mass, deposit, or sediment as (1) the precipitated solid matter produced by water and sewage treatment processes; (2) mud from a drill hole in boring; (3) the muddy sediment in a steam boiler; (4) waste from a coal washery; or (5) the precipitated or settled matter from industrial processes. Water treatment sludge consists of suspended solids, coagulation chemicals, usually an alum or polymers with a limited amount of biological materials. A comprehensive review of industrial sludge can be found elsewhere [1]. In that review, sludge from petroleum, metal-nishing, ¤ue gas cleaning, water treatment, pulp and paper processing, polymer plants, chemical plants, as well as mineral and metallurgical industries are discussed. The sludge addressed in this chapter is the by-product of a wastewater treatment plant. Brief reviews on the treatment, usage, and disposal of this type of sludge are available [2,3]. In this chapter, we take a comprehensive approach to examine the literature on sludge dewatering and drying in order to give readers a relatively detailed and complete picture of this area that is growing with the expenditures on environmental cleanup and control, amounting to about US $150 billion in the United States and about US $400 billion globally in 1997 [4].
