Range of Values
Volume (as percent of water treated) Suspended solids concentration Solids content
Solids content after long-term settling Composition, alum sludge:
Hydrated aluminum oxide Other inorganic materials Organic materials
Source: Lang, L.E. et al., Procedures for Evaluating and Improving Water Treatment Plant Processes at Fixed Army Facilities, Report of the U.S. Army Construction Engineering Research Laboratory, Champaign, IL, 1985.
Sludges resulting from coagulation treatment are the most common and are typically found at all municipal water treatment works. Typical characteristics of these sludges are reported in Table 9.6.
Stabilization of wastewater sludges and dewatering of most all types of sludge are necessary for economic, environmental, and health reasons. Transport of sludge from the treatment plant to the point of disposal or reuse is a major factor in the costs of sludge management. Table 9.7 presents the desirable sludge solids content for the major disposal and reuse options. Sludge stabilization controls offensive odors, lessens the possibility for further decomposition, and significantly reduces pathogens. Typical pathogen contents in unstabilized and anaero-bically digested sludges are compared in Table 3.10. Research on the use of various fungal strains as a means to stabilize sludges has been conducted with mixed results but may hold promise in some cases (Alam et al., 2004).
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