Biological treatment is a destruction process relying on oxidative or reduction mechanisms. This process is used in wastewater treatment and in bioreclamation of contaminated sitres. It can be divided into two types, which includes aerobic biological treatment and anaerobic biological treatment. The aerobic biological treatment takes place in the presence of oxygen, while anaerobic biological treatment is an oxygen-devoid process. This treatment technology is applicable to wastewaters containing biodegradable organic constituents and nonmetallic inorganic constituents including sulfides and cyanides. There are four types of process, which includes activated sludge aerated lagoons trickling filter and rotating biological contactor. This process can be used on a broad class of biodegradable organic contaminants that includes refractiles that are not readily biodegradable.