Industrial effluents with varying characteristics may have very high pollution potential with high COD. Such effluents are difficult to treat using biological treatment only. In this case, use of hydrogen peroxide in combination with ferrous sulphate popularly known as Fenton’s reagent can be used a pre-treatment to reduce the toxicity of effluent to a certain level. This pre-treatment will aid in reducing load on the biological system which will in turn reduce the size of the biological treatment reactor. Operational problems such as disturbance of the biological system, disintegration of the filter media will also be avoided.  
Fenton’s reagent gives an average COD removal efficiency of 35%. It also helps in reduction of BOD, chloride, oil & grease, TSS and phosphate and increases TDS and Sulphate content.