This book covers the technologies which are applied to treat and purify water. This treatise on water treatment is also closely associated with solid-liquid separations. The subject of water treatment is wide-ranging and the technologies discussed in this book not just confined to only physical methods of water pollution control. A comprehensive illustration of technologies pertinent to treatment of both ground water and wastewater (i.e., industrial, pharmaceutical and municipal) is embodied in this book. The approaches and technologies summarized are a combination of chemical, physical, and biological techniques. There eight chapters in this book. All the chapter deal with fundamental technologies used in water treatment process which include, coagulation, flocculation, activated sludge treatment, microfiltration, nanofiltration, reverse osmosis, membrane bioreactor technology, etc. In this book, particular stress is given to water treatment technologies which are not only environmentally friendly but also cost effective. This book can be treated as a ready reference for all the topics related to water pollution and water treatment. Students, researchers and industrialists in the field of water treatment can use this book to solve the problems related to water purification technologies.