Experimental Study On The Treatment Of High-salinity Oil-field Water By Hydrolytic Acidification-biological Contact Oxidization

The wastewater from oil exploit is huge, oily waste water with high salt contains high concentration of Cl" and plenty of oil pollution. The waste water have poor biodegradability, it will pollute the water and the soil if it has not been treated. Currently, there are few research reports on high-salt oil wastewater. In this situation, my research using acidification and biological contact oxidation system in the laboratory studied on the treatment of high-salt oil wastewater,analyzing the indicators removal of COD, ammonia nitrogen, oil and other pollutions of the wastewater, and the change law at different HRT, temperature, pH. Draw the best design and process control parameters. Below are the results of this research:(1)Optimized the parameters of hydrolytic acidification stage, acidification tank, pH in the range of 5.0-6.2, DO between 0-0.5mg/L, the temperature between 19.8～24.2℃,the optimum HRT is 8h. In these conditions, COD removal rate was 31.4%, oil removal rate was 23.6%, and improved biodegradability of wastewater, creating favorable conditions for further biological treatment.(2)On the stage of Biological contact oxidation, the first tank, pH between 7.02～7.35, DO between 1.8～3.8mg/L, the second tank, pH between 7.23～7.44, DO between 3.4～5.1mg/L. Overall temperature between 20.1～23.7℃,the best HRT is 8h.(3)Keep the conditions of hydrolytic acidification stage, when control DO in first tank of Biological contact oxidation stage between 1.8～3.8mg/L, second tank between 3.4～5.1mg/L, the optimum temperature is 25℃,the optimum pH is 7.(4)Keep the best conditions, monitor pollution indicators, the system has significant removal effect on the main pollutant COD, ammonia nitrogen, oil.The average removal rates are 91.32%,92.55%,92.6%,the entire system run stable, out-water has low concentration on COD, ammonia nitrogen, oil. Fully in line with the national A standard of "Integrated Wastewater Discharge Standard"(GB8978-1996).(5)When the Cl- concentration of in-water from llg/L jump to 25g/L, COD removal rate of the system is from 89.03% down to 32.56%, ammonia nitrogen removal rate is from 91.36% down to 39.08%, the color of hydrolytic acidification tank turn shallow, flocs turn loose, treatment effect significantly worse, nearly has no effect on oil, microbial biomass have aignificant reduction in biological contact oxidation tank,out-water turbidity, the color of biofilm turn dark, when the in-water Cl- concentration back to 11g/L, the whole system need about 8.5 days to restore the normal treatment level to the pollutant.