Study On Oil Field Produced Wastewater By Ozone Oxidation Treatment

Along with extension of the oil-field development time and the enhancement of oil production technology, the quality of produced water has a great change, and it has brought new issues and new difficulties to the treatment of oil-field produced wastewater. At present, majority of oil fields in our country is in the oil development of the middle and the later period. The water content of produced oil is 70%～80%, and some oil fields have even reached as high as 90%. The production of wastewater contained oil is larger each day. The excessive wastewater contradiction has become prominent day by day. The problem of excessive wastewater and the wastewater always can not meet wastewater emission standards has been a serious threat to the normal production and the ecological environment. However, because of technical, economic and other reasons, the conventional craft is difficult to make it meet emission standards.In recent years, ozone oxidation treatment of refractory industrial wastewater is very active to research. In this study, we study on the ozone oxidation technology to deal with oil field produced wastewater by carrying on the pretreatment and the advanced treatment. The results showed that: (1) When the contact reaction time is 60min, ozone oxidation pretreatment bench scale experiment is benefit to decrease the COD of produced wastewater. And B/C values of wastewater reach the maximum 0.27; When the ozone dosage is 50mg/L and the contact reaction time is from 10min to 60min, the removal efficiency of COD is enhanced from 16% to 40%; In the experiment of ozonation by contact medium of activated carbon and ozone dosage is 50mg/L, the COD removal efficiency reaches 68% at 90min contact reaction time, Ozone oxidation was greatly improved; (2). the change of COD value, BOD₅ value and B/C value by pilot test experiment is similar to bench scale. It has provided the effective basis for the large-scale production application. And residual ozonation in wastewater effect on biological system greatly; (3) When the contact reaction time is 60min and ozone dosage is 5mg/L, the COD value is higher than . The COD removal efficiency of wastewater reaches above 65%. When the ozone dosage is 10mg/L, effluent COD value bellows 50mg/L stability. (4) The effluent COD of ozone/biology activated carbon system is 40mg/L, the ammonia nitrogen and the petroleum class has been lower than detection limit, and the TOC elimination rate is about 70%.