Wastewater is a combination of water and water-transported wastes from domestic, commercial, industrial and agricultural sites. It also includes surface and storm water inflow, and groundwater infiltration that may enter the sewer system. On a global scale, nearly 80% of wastewater generated is discharged into the environment without treatment, leading to massive levels of water contamination. There are several ways of treating wastewater based on the type of contamination. A combination of physical, chemical and biological methods can be used to treat wastewater in wastewater treatment plants. Wastewater, after it has been treated, can be reused for the artificial recharge of aquifers, rehabilitation of natural ecosystems including wetlands, and industrial purposes. Certain processes such as ultrafiltration, forward osmosis, reverse osmosis, ozonation and advanced oxidation ensure that wastewater is made reusable. This book studies, analyzes and upholds the pillars of wastewater engineering and its utmost significance in modern times. It includes some of the vital pieces of work being conducted across the world, on various topics related to the treatment and reuse of wastewater. It is a vital tool for all researching or studying wastewater engineering as it gives incredible insights into emerging trends and concepts.