native bacterial mixed culture: a proportionate solution for refinery and petrochemical wastewaters

background heat, chemical and organic pollution are three types of environmental pollution, caused by refinery and petrochemical industries. problems caused by hear and chemical pollutants are currently resolved to some extent but organic pollution such as poly aromatic hydrocarbons (pahs) are still considered as important problems of industry and environment. objectives a laboratory study was carried out to investigate the effects of native bacterial mixed culture (bmc) isolated from mixtures of refinery and petrochemical wastewaters for treatment of wastewaters of refinery and petrochemical industries. materials and methods all bacteria were isolated from two refineries and two petrochemical plants of iran. several bacterial strains from both kinds of wastewater were mixed and two final stock culture collections (bmca and bmcb), showed the ability to improve the growth among strains. bmca was added to the refinery wastewater (activated sludge influent sample) and bmcb was added to petrochemical wastewater (activated sludge influent sample). the effects of continuous and non-continuous aeration at high and low pressures, along with the effects of nutrient addition in the beginning of experiment versus sequential addition at specific time intervals, were studied. results native bmc, when continuous high level aeration was used, decreased chemical oxygen demand (cod) in refinery and petrochemical wastewaters for about 81% and 63%, respectively. gradual addition of nutrients increased cod removal of refinery and petrochemical wastewaters to 85% and 87%, respectively. conclusions native bmcs from mixture of refineries and petrochemical wastewaters can be an effective method of wastewater treatment of both regional refinery and petrochemical plants. high pressure continuous aeration and gradual nutrient addition to the native bmcs can improve bioremediation of organic wastewater in different industries.