The advanced oxidation process has proven to be the most effective treatment technology for completely removing organic contaminants from wastewater. It is a broad-spectrum technique, as it is not selective towards organic compounds. In this process, hydroxyl radicals having a very high oxidation potential of 2.7 eV are produced in situ. It offers a powerful water treatment solution for the reduction and/or removal of residual organic compounds as measured by COD, BOD or TOC. Generally, the effectiveness of the treatment depends on the type of effluent, its physical and chemical properties, based on the type of AOP system to be used. Since the Fenton process is pH sensitive, it provides a very limited working range, around 2-4, to overcome this drawback some Fe complexes with ligands such as EDTA, EDDS, oxalates and tartrates are reported which provide a wide pH range. Nanoparticle technology is another means for the rapid degradation of refractory organic waste in a much shorter time. This article is a review of all the technologies used in the past, their disadvantages and the new techniques that overcome them. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original EssayThe ever-growing population has cost ever-increasing industrialization which causes water pollution, resulting in unwanted impacts on our environment. To meet water needs, the concept of reduction, reuse and recycling has taken firm root in the concept of water treatment and management. For over a decade, social organizations, NGOs and government bodies have established various dos and don'ts to protect the environment, and sustainable development plays a key role. Strict quality standards are claimed for toxic chemicals that negatively affect the biosphere and cause landfill. It has generally been observed that pollutants not acceptable to biological treatments can be characterized by high chemical stability and/or great difficulty in being completely mineralized. Different separation techniques consist of conventional phase separation techniques (adsorption processes, stripping techniques) and methods that destroy contaminants (chemical oxidation/reduction). Adsorption processes cause more landfills, while chemical oxidation/reduction aims to mineralize contaminants into carbon dioxide, water and inorganic substances or, at least, transform them into harmless products. So a technique that produces complete degradation of non-biodegradable waste without any phase change is a need of the hour. In 1987, Glaze et al. defined AOPs as “water treatment processes at near ambient temperature and pressure that result in the generation of hydroxyl radicals in quantities sufficient to effect water purification”. Previously it was used only for the treatment of drinking water, subsequently its application in industrial wastewater was studied and it proved to be an excellent technique for the degradation of non-biodegradable organic compounds. In AOP treatment, hydroxyl radicals (OH•) or sulfate radicals (SO42-) are generated in sufficient quantities to oxidize refractory organic substances into carbon dioxide, water and biodegradable inorganic wastes. Hydroxyl radical differs from common oxidants such as chlorine and ozone which have a dual role of decontamination and disinfection, AOPs are mainly applied for the destruction of organic or inorganic contaminants in water and wastewater. The.