Investigation of Oil-in-Water Emulsions Treatment by Crude Oil Degrading Bacteria and Coagulation with Cationic Polyacrylamide

Background: Oily wastewater which is released from different industries is one of the most common pollutants. Efficiency of conventional methods such as gravity separation and skimming, dissolved air flotation, demulsifying, coagulation and flocculation are frequently not efficient enough is not acceptable. Therefore, in this study it was intended to use a new strategy that is combined by two methods. Methods: Nine crude oil degrading bacteria were isolated from oil contaminated sites in the Persian Gulf at Terminal of Bandar Abbas. Choosing cases were cultured in the ONR7a medium supplemented with 1% (v/v) of crude-oil. Two strains that had more growth and higher oil removal were chosen and identified from nine isolated strains for further study. Due to its low price and simple usage of coagulation-flocculation process, the next step of this study was dedicated to this physical treatment method. The coagulants usage has also some limitation because of its toxicity and health hazard, therefore the coagulant content in waste treatment process should be optimized. In this study it is attempted to investigate the efficiency of bioremediation following by coagulation -flocculation process. Results: The two isolated strains are identified with biochemical and molecular methods as Alcanivorax and Idiomarina. Then crude oil biodegradation for each strain is determined by spectrophotometry and Gas Chromatography (GC). Cationic polyacrylamide (CPAM) was chosen as flocculants. The crude oil removal was determined by using 30 mg/L, 50 mg/L and 70 mg/L CPAM in jar test for synthetic oily wastewater with three different crude oil content (500 mg/L, 1000 mg/L and 1500 mg/L). The results have shown that the highest removal efficiency is reached by using 70 mg/L of CPAM in the synthetic wastewater with 1000 mg/L crude oil in there. Conclusion: The study demonstrated that the bio degradation of oily wastewater following by flocculation removes the oil significantly from the synthetic oily wastewater.