The Electric Induced Ozone Air Flotation Integrated Process For Oilfield Waste Water Treatment

In order to explore the characteristics of ozone-coagulation process with the removal process,this study compared the effect of ozone-coagulation process with traditional coagulation process and ozone pre-oxidation process through beaker tests.Based on the efficiency treatment effects of ozone-coagulation process,the ozone-coagulation process is further optimized to the electro-induced ozone flotation integrated process,and it was applied in pilot tests as well as field tests of one oilfield for providing a theoretical basis for the efficient removal of oilfield wastewater.The main research contents and experimental results of the paper are as follows:For the wastewater collected from a coalition station in one oilfield,the optimal reaction conditions for the coagulation process were:PAC dosage 30mg/L,pH value 7.0,suitable temperature 50℃,The average oil removal rate and SS removal rate were 67.91%and 71.74%,respectively,the treatment effect was very unsatisfied;The optimal reaction conditions for pre-oxidation of ozone were as follows:dosage of O₃ was 6mg/L,pH was 7.0 and temperature was 50℃.Under these conditions,the average oil removal rate and SS removal efficiency were 69.83%and 67.53%,respectively,the effluent quality could not reach the injection standard;The optimum reaction conditions for the ozone-enhanced coagulation process are as follows:dosage of O₃ was 6mg/L,dosage of PAC was 30mg/L,pH was 7.0,temperature was 50℃.When the crude oil of influent was 110.4mg/L and the SS of influent was75.6 mg/L,while that of effluent was less than 10 mg/L and less than 5 mg/L,respectively,which can reach the standard of injection water quality,greatly improving the treatment effects of single tradition processes.According to the treatment effect of each process,it is determined that the ozone-enhanced coagulation reaction process can meet the requirements of the oilfield water treatment,and it was further improved into an electro-induced ozone air flotation integration process.Through the pilot test study,the optimal reaction conditions of electro-induced ozone air flotation integration process were as follows:ozone dosage was 10 mg/L,dissolved gas pressure was 0.3 MPa,and reflux ratio was 0.5,the average removal rate of oil content and SS after treatment were 97.4%and 97.7%,respectively,which can reach the standard of injection water quality.Based on the good treatment effect of the electro-induced ozone flotation integrated process,field tests of electro-induced ozone flotation integrated process were performed on the produced water from an oil field.According to the results,oil removal rate can reach 98.26%,while the total removal rate of SS can reach 98.92%.The amount of oil and SS in effluent was less than 5 mg/L and less than 1 mg/L,respectively.The average particle size of 0.7μm,microorganisms and organic matters were also effectively degraded.The effluent quality compliance rate was100%.Based on the forecast of the operating cost of the ozone-flotation integrated ozone-fueled processing equipment with the processing scale of 10m³/h,15m³/h and 20m³/h,the processing cost of the three specifications equipment was all lower than 5 yuan m³/h,which shows the electro-induced ozone flotation integrated process is economically feasible.