Water which has been contaminated due to human use is termed as wastewater. It is the byproduct of various human activities and, can be classified into industrial wastewater, municipal wastewater and domestic wastewater depending upon its source. The techniques and methods which are used to remove contaminants and other unwanted particles from water fall under the discipline of wastewater treatment. Some of the common techniques used in a wastewater treatment facility are sedimentation, biochemical oxidation, polishing and chemical oxidation. According to the water being treated, treatment plants can be classified into industrial wastewater treatment plants, sewage treatment plants, Leachate treatment plants and agricultural wastewater treatment plants. This book is a compilation of chapters that discuss the most vital concepts in the field of wastewater treatment. It presents selected concepts that redefine wastewater treatment. This book is an essential guide for both academicians and those who wish to pursue this discipline further.