There are various options for treating sludge including stabilization, thickening, dewatering, drying, and incineration. The
costs for treating sludge and removing sludge from wastewater are roughly the same. Typically a polymer chemical
is used for the volume reduction process known as dewatering. Polymers are slippery chemicals, which mean that there is always a risk of slipping or falling due to spills and leaks. Polymers can also be environmental stress crack agents.
Dewatering decreases sludge liquid volume as much as 90 percent. Digested sludge is put through large centrifuges that work in the same fashion as a washing machine spin cycle. The spinning centrifuge produces a force that separates the majority of the water from the sludge solid, creating a biosolid substance. Then the water pulled from the spinning is sent back to the plant for reprocessing. Adding polymer chemical to the substance improves the consistency, creating a firmer product that is easier to manage. The bio-solid cake consists of between 25 and 27 percent solid material