Dyes are versatile compounds that have been successfully used in textile printing, rubber, cosmetics, plastic, pharmaceutical, and leather industries to color the products. Dye-using industries, particularly textile or printing industries are responsible for the generation of a great amount of colored wastewater that are polluting and threatening the environment. Many of these dyes are carcinogenic, mutagenic, and teratogenic, as well as harmful to human, aquatic life, and other living things and their elimination from wastewater is highly essential. Various approaches have been implemented in the efforts to mitigate the issue related to textile wastewater, such as adsorption, biological processes, advanced oxidation processes, membrane technology, etc. In this Volume 1, the application of various types of polymers in different wastewater treatment technologies are presented. The synthesis procedure of some polymers, the polymer modification, the effect of operational parameters onpolymer efficiency, the interactions between polymers – dyes, etc are discussed.