Chapter 10 - Sludge Treatment and Disposal

Abstract

Sludge disposal is a major headache for many municipalities. Sludge represents the true residues of civilization, and its composition reflects the style of living, technological development, and ethical concerns. “Pouring things down the drain” is a way of getting rid of all manner of unwanted materials, not recognizing that these materials often become a part of the sludge that must ultimately be disposed off in the environment. Sludge are generated from nearly all phases of wastewater treatment. The first source of sludge in a wastewater treatment facility is the suspended solids from the primary settling tank or clarifier. Variability of the sludges is immensely important in the design of sludge handling and disposal operations. Sludge has three characteristics that make the solution unlikely: It is aesthetically displeasing, potentially harmful, and has too much water. The objective of sludge stabilization is to reduce the problems associated with sludge odor and putrescence, as well as to reduce the hazard presented by pathogenic organisms. Sludge may be stabilized using lime, aerobic digestion, or anaerobic digestion. Sludge thickening is a process in which the concentrations of solids is increased and the total sludge volume is decreased, but the sludge still behaves like a liquid instead of a solid. Dewatered sludge behaves like a solid after the treatment. Sludge is disposed by two types of methods: incernation and land disposal. Two types of incinerators have found their use in sludge treatment: multiple hearth and fluid bed.