Treatment Processes
Sludge
Sludge is the concentrated semi-solid pollutant left from industrial wastewater, or sewage treatment processes. It can also refer to the settled material resulting from conventional drinking water treatment, and numerous other industrial processes. The term is also sometimes used as a generic term for solids separated from suspension in a liquid; this 'soupy' material usually contains significant quantities of 'interstitial' water (between the solid particles).
The term biosolids was introduced to more constructively describe sludge and promote its suitability for reuse as a resource, rather than regarding it as a waste. Biosolids is defined as a "nutrient-rich, organic byproduct of the nation's wastewater treatment process."