Wastewater represents an alternative to freshwater if it can be treated successfully for re-use applications. Promising techniques involve photocatalysis, photodegradation, adsorption, bioreactors, nanocomposites, nanofiltration and membranes. The book focuses on the following topics: Biological Wastewater Treatment Technologies. Pesticides and their Treatment in Wastewater. Adsorption Removal of Organic Pollutants using Graphene-based Nanocomposites. Reverse Osmosis for the Removal of Organic Compounds from Wastewater. Treatment of Refractory Organic Pollutants using Ionic Liquids. Biohydrogen and Bioethanol Production from Agro-Industrial Wastewater. Methods for the Treatment of Dairy Wastewater. Membrane Bioreactors for the Removal Pesticides and Hormones in Municipal Wastewater. Carbon Nanotubes and their Composites for Treating Industrial and Municipal Wastewater. Low-cost Adsorbents for the Removal of Malachite Green from Water and Wastewater.