Waste Water Treatment; is the treatment of domestic and industrial wastewater to make it suitable for reuse or discharge to nature. Treatment is usually achieved by biological processes such as aeration, activated sludge systems, membrane bioreactors or slow sand filtration. The flowsheet generally starts with sedimentation, where water and solids are separated, followed by solidification of the dissolved matter as biological flocs, and ends with final sedimentation to obtain water of the desired purity. With the right treatment, it is of course possible to make the vast majority of industrial water available for reuse.

Waste water treatment processes are as follows:

Sludge as a result of treatment can be disposed of by a number of methods; it can be subjected to thickening, stabilization, conditioning, disinfection and dewatering, thermal drying, thermal reduction methods. After these, there are alternatives for final disposal such as distribution and marketing, chemical stabilization, landfilling and deposition in lagoons.