Sludge is a semi-solid slurry and can be produced as sewage sludge from wastewater treatment processes or as a settled suspension obtained from conventional drinking water treatment and numerous other industrial processes.

Sludge analysis involves the determination of heavy metals, pathogens, micro-pollutants and hazardous elements from sludge of simple wastewater treatment plants and septic tanks. 

The most common tests for sediment and sludge are sludge volume index, total and volatile solids. Volatile solids, which is usually organic matters.