Wastewater represents an alternative to freshwater if it can be treated successfully for re-use applications. Promising techniques involve photocatalysis, adsorption, nanocomposites, and membranes. The book focuses on several topics related to the removal of organic pollutants from wastewater. Keywords: Wastewater Treatment, Organic Pollutants, Organic Dyes, Photocatalysis, Nanocomposite Photocatalysts, Photocatalytic Degradation, Adsorption, Membrane Filtration, Fenton Processes, Biosorbents, Phenolic Compounds, Carbon Quantum Dots, Methylene Blue Degradation, ZnO Composites, TiO2 Based Nanocomposites.