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Water co-produced with oil and gas is termed produced water. Produced water is very difficult wastewater to treat and characteristics changes by well to well. In this study, treatability of produced water generated from oil production fields in Trakya region which is operated by National Oil and Natural Gas Company of Turkey was investigated. The aim of this study is to investigate the pre-treatment alternatives of reverse osmosis and nanofiltration membranes and find the most appropriate treatment combination. Management of produced water was also evaluated. Dissolved air floatation (DAF), acid cracking (AC), coagulation (CA) with lime and precipitation, cartridge filters (CDF) (5 and 1 μm), microfiltration (MF) and ultrafiltration (UF) were used as pretreatment techniques, and nanofiltration (NF) and reverse osmosis (RO) were carried out to reduce salt content of produced water as a final treatment. Different combinations were tried to determine the best pre-treatment combination regarding both the best effluent water quality and high permeate flux. According to the experimental results, treatment combinations provided required treatment to reach discharge standard for COD which is 250 mg/L for petroleum industry in Turkey. However, different treatment combinations should be applied to reach the discharge standard for sodium.

Although NF membrane supplied the COD discharge standards, salt concentration was high in permeate. Thus, RO membrane can be effectively applied for the treatment of produced water after appropriate pre-treatment. The experimental results showed that primary sedimentation + oil/ water separator + DAF system + 1 μm ceramic or metallic cartridge filte + 0.2 μm ceramic or metallic MF gave the best pre-treatment option by means of permeate flux and water quality before RO membrane. Activated carbon adsorption can also be used which we could not investigate between 0.2 μm MF and RO membranes. According to cost analysis, collecting wastewater and establishing only one membrane plant at one place gave the cheapest solution. However, fourth alternative which is collecting the wastewater at three main stations and treating in site by different three membrane plants may be a best solution by means of flexibility of three membrane plants. Additionally, pilot scale experiments should be carried out for final decision.