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Wastewater treatment - Sludge treatment and disposal ...

Wastewater treatment - Wastewater treatment - Sludge treatment and disposal: The residue that accumulates in sewage treatment plants is called sludge (or biosolids). Sewage sludge is the solid, semisolid, or slurry residual material that is produced as a by-product of wastewater treatment processes. This residue is commonly classified as primary and secondary sludge.