Petroleum Refineries typically have high BOD and COD values which are mostly composed of oils, hydrocarbons (saturated and unsaturated), nitrogen containing organics, phenolics (phenols, cresols and xylenols), sulfides and mercaptans. In addition, ammonia is also present in many refinery wastewaters.
Treatment with ozone at elevated pH has shown good reduction in the phenolic concentration and also sulfides. The wastewaters contain almost nil dissolved oxygen which often leads to the failure of the biological system. Ozone in the pre-treatment can work wonders and increase the dissolved oxygen; simultaneously reducing the BOD. Final polishing of the effluent in terms of phenolic content, dissolved iron can be done by using ozonation in the pre-treatment.