Sludge is a byproduct of treated wastewater. Sludge must be treated to reduce its volume and weight for easier handling and turning it into a usable end product.

 The first common step for sludge treatment is thickening. Sludge is thickened to reduce its overall volume making it easier to handle and dewater.

The sludge is then dewatered to further remove water by means of mechanical pressing or by centrifugal force to separate the solids from the water.

In most casese, dewatered sludge can contain as much as 70 percent water content. Sometimes these dewatered sludge require further water removal by sludge drying process.