| Oilfield wastewater is the main by-product generated by the oil and gas industry. The wastewater contains high concentration of oil, benzenes, phenols, PAHs (Polycyclic aromatic hydrocarbons), heavy metals, radioactive substances and chemical products. Such wastewater must be treated before discharged into the environment, otherwise it will severely pollute the surrounding ecosystem. With the increasing volume of wastewater all over the world, the treatment of produced water has lately become a significant issue.Currently, the produced water is usually treated through different physical, chemical and biological methods. However, the conventional physical-chemical method not only cannot remove small-suspended oil particles, but also will produce hazardous sludge. The biological method is widely used to treat oil field wastewater in recent years, it is considered to be a cost-effective and environmental friendly method. The BCO (Biological contact oxidation) process is a type of aerobic Biofilm technology which has been demonstrated that the combination of Biofilm reactor and Activated sludge process. It can not only maintain high hydraulic loading rates and retain high activated sludge concentration, but also produce less sludge.This paper mainly evaluated the capability of BCO process to treat oilfield wastewater under laboratory conditions, it can also provide theoretical reference and basic data for produced water bioremediation. The main results of this paper were as follows:(1) This paper mainly researched the feasibility and effect by single strain inoculation to treat oil field wastewater in Jiangsu province. The practical operation showed that BCO process for oilfield wastewater is available and stable, it also has a good treatment effect.(2) This system takes23days to complete the biofilm acclimation (oil removal rate kept more than91%) by using oilfield raw wastewater. The result showed that the BCO process has advantages of little biofilm formation time and quick start-up.(3) The research on biofilm formation effect with different carbon source nutrient showed that wheat bran as the main carbon source had a more significant effect than starch. The first oxidation reactor contribute most of the pollutant removal, accounting for almost70%of the toatal removal. (4) Research on oilfield wastewater of Matouzhuang by BCO process treatment showed The optimal conditions of BCO process were that the HRT was16h, the temperature was24.8℃, the pH was6.71and DO was6.56mg/L, under the optimal conditions, the average removal rates for oil, COD, TOC, SS, median particle size, sulfide and corrosion are98%,64.16%,49%,87.5%,82%,100%and51.8%, respectively; The oil concentration in effluent can meet A1level of re-injection industry standard (SY/T5329-94)(5) Results obtained by GC/MS analyses showed that most classes of organic compounds were removed by BCO process and other organic substances contribute to the residual COD and TOC contents of the effluent. On the other side, HPLC results indicated that the influent wastewater contains a total of12PAHs. BCO process degraded11PAHs effectively, except Dibenzo(a,h) anthracene.(6) Research on different kinds of oilfield wastewater by BCO process treatment showed: Under the same optimal conditions, the system achieved degradation efficiencies of96%～99.5%f or oil,50%～75%for COD and91%～94.1%for SS. The oil concentration in effluent of Chenbao, Tongzhuang^Matouzhuang、Cuizhuang and Zhoucheng all can meet A1level of re-injection industry standard (SY/T5329-94),while Tian83"s effluent reached A3level. |
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