Study On Disinfection Technology Of Oilfield Produced Water

There are a large number of microorganisms in the oilfield produced water, such as sulfate-reducing bacteria, iron bacteria, saprobe bacteria and other microorganism, and their growth, metabolism, reproduction process, not only cause serious corrosion of drilling equipment and other metallic materials, but also increase difficulties to sewage treatment and reuse. Therefore, the search for a suitable disinfection technology to meet the actual demand of oil production is imperative. Above three kinds of bacteria of oilfield sewage were the main research objects, a bottle of law and culture in vitro dilution of the three bacteria were cultured and counting. Electrochemical disinfection and ozone oxidation were sterilization methods to research effect. The orthogonal experiment design and the single-factor authentication were used to optimize technology of electrochemical and ozone sterilization.The advantages and disadvantages of the two disinfection methods were compared and evaluated. Sterilization is that electrolysis disinfection has the advantages of good effect, high stability, low investment, and can be widely used in disinfection of oilfield sewage. Electrochemical disinfection experiments with Ti/RuO₂ for the anode and cathode for Ti, mainly saw about the influence of the electrolysis time, current density, plate spacing, pH, and type of power on the bactericidal effect. The results show that under optimal conditions, that is, the current density of 30 mA/cm², pH 5.0, a distance of 3.0cm, a DC power supply, electrolyzed oilfield produced water for 10 min, the killing rate of SRB, FB, TGB rate are respectively100%, 99.95%, 99.91%, three kinds of bacteria in the water after being disposed can meet A-class reinjected standard of the recommended level SY/T5329-94. COD and BOD removal rate were 58%, 37.5%, respectively.Experimental results of electrochemical disinfection mechanism show that, the electric field together with activated chlorine play an important role of in electrochemical disinfection. The electric field kills bacteria only in the presence of electric field, and disinfection rate is not high, generally it is unable to meet water disinfection requirements. The activated chlorine disinfection need time, when the initial concentration of chloride ions is 3100 mg/L, electrolysis 2 min after holding 10 min, disinfection rate can be achieved 99.6%.The ozone dosage, contact reaction time and pH were studied to mainly determine the influence on the bactericidal effect in the ozone disinfection experiments. The results show that under optimal conditions, that is, ozone dosage of 3.0 mg/L, pH 6.0, ozone oxidation time of 30 min, SRB, FB, TGB bactericidal rates were respectively 99.09%, 98.95 %, 98.10% of oilfield produced water.Compares the two disinfection methods, it is can be known that the electrochemical disinfection has the advantages of shorter time required and lower energy consumption. and oxidation material generated in the process of electrolysis still has bactericidal effect after a period of cessation electrolysis, and can inhibit the second birth of bacteria. Therefore, electrochemical bactericidal is more appropriate to oilfield sewage disinfection than ozone disinfection.