Study On "Aerobic Biochemical And Microfiltration Membrane" Combined Technology For Low Penetrability Oilfield Produced Water Treatment

This paper makes laboratory studies on low penetrability oil field produced water treatment effect by high-rate oil-degrading aerobic bacteria in Sequencing Batch Reactor(SBR). It makes research on the polluting effect of highly mineralized oily wastewater on microfiltration membrane fouling. It proposes engineering design of the "aerobic biochemical and microfiltration membrane" combined technology in the treatment of Changqing oil field produced water, and the operating effect for 86 days of the combined technology is studied.(1) SBR technology adding high-rate oil-degrading aerobic bacteria has good effect in the treatment of Changqing oilfield produced water. It has stable water quality of effluent, low concentration of pollutants, and high oil removal rate. Under the condition of joining the carrier, the effluent concentration of oil averages in 6.39 mg/L, oil removal rate reaches 98.21% in average. The effluent concentration of COD averages in 60 mg/L, the COD removal rate reaches 94.98% in average.(2) Experimental studies on pollution characteristics of microfiltration membrane finds out that impurities, inorganic salt ions, oil substances, and so on in the highly mineralized oily wastewater of Changqing oil field cause membrane pore blockage, which cause severe membrane fouling. The cleaning method of "NaOH solution, HCl solution and alkaline surfactant" is determined by the research. This method has significant effect in recovering the membrane flux, whose recovery rate can reach more than 90%.(3) The research proposes the "aerobic biochemical and microfiltration membrane" combined technology desighed for Changqing oil field produced water treatment with the processing scale of 300 m3/d. After 86 days of continuous running test, the research finds out that the desighed technology has strong oil concentration fluctuations resistance, and stable operation. When treating oil field produced water, its oil pollutant removal effect is remarkable, effluent quality reaches the designed control requirements, and oil concentration is less than 2.5 mg/L which is far below the limit of low penetrability oil field injection water quality standard. In the whole system, flotation, biological reaction pool and membrane component’s contribution to oil removal rate is 59.91%, 37.63% and 2.47% in average respectively, and to removal rate of COD is 41.18%, 53.72%, 5.37% in average respectively. Flotation and biological reaction pool adding high-rate oil-degrading aerobic bacteria are main working section in removing oil and COD in effluent. The membrane system is an important part to ensure the combined technology be successfully applied in Changqing Oilfield produced water treatment.