Treatment of oily wastewater using chemical/biological processes

The importance of oil and natural gas in human life is clear. Water produced along with crude oil and natural gas (produced water) during the extraction of oil and gas wells; is the largest volume of produced wastewater in the oil and gas industry. More than ۸۰% of the wastewater generated from the oil production process is produced water (PW). PW is a mixture of different organic and inorganic substances. Since water scarcity is one of the serious problems in the country, water and wastewater treatment is very important. In this study, a combination of chemical and biological processes was used to recover water associated with the production of oil and gas fields for industrial use. Because of the environmental standard, the chemical oxygen demand (COD) is very important; the COD parameter was used to measure the amount of wastewater treatment. Turbidity and residual Oil & Grease content were also analyzed. The initial values of COD, turbidity, and oil & grease in the wastewater were ۳۳۵۰ mg/L, ۲۵ NTU and ۷۲۲ mg/L, respectively. In the chemical process, ferric chloride (FeCl۳) and poly aluminum chloride (PAC) coagulants were used and the results showed that the FeCl۳ coagulant had a higher efficiency with COD, turbidity and O&G removal rates of about ۴۵%, ۸۰%, and ۹۰%, respectively. In the biological process, extracted and cultured oily-salt-loving microorganisms. Then, the sequential batch reactor (SBR) method was used, and the combined purification system over a period of ۲۴ hr. resulted in a removal efficiency of about ۸۵% for COD, ۹۰% for turbidity and the amount of Oil & Grease was trace. Consequently, with chemical and biological combined methods can treatment the produced water wastewater and reduce the amount of organic load for reuse in the industry.