Water is becoming a progressively scarce resource on our planet. Although we have vast amount of water on our planet, but fresh water makes up only about 1% of all the planet’s water bodies. It is reasonable to say at this point, that any sources of water which might be used economically and effectively be promoted and further developed in the overall benefit of human kind. A large proportion of fresh water is used for human consumption, followed by irrigation use, and whenever fresh water is scarce, marginally good quality or water treated after wastewater treatment should be used for agricultural purposes. Domestic wastewater is comprised of 99.9% water and the 0.1% remaining part consists or organic/inorganic suspended and dissolved solids, making it unfit for human use and placing it in the wastewater category, which may be made suitable for agricultural use. So, the composition of wastewater is dependent upon the functions to which the water was subjected and its treatment is also dependent upon the initial use of water. This book deals with the various treatments to which the waste water is subjected to make reuse of water a possibility.