NOVELTY - Processing oilfield wastewater involves removing oil spill, dispersible oil, emulsified oil and suspended materials; separating suspended materials and solid particles; reducing viscosity of sewage to less than 0.4 mPa.s; microbiologically degrading polymer and petroleum in sewage with natural microbiological strains obtained by manual selection and domestication; filtering through ultrafiltration membrane to remove bacteria, virus and suspended materials in the sewage; and filtering inorganic ions through reverse osmosis membrane.    USE - Method for processing oilfield wastewater (claimed).    ADVANTAGE - The method effectively degrades polymer in the sewage, and the processed water satisfies the requirement of water for polymer solution.    DETAILED DESCRIPTION - Processing oilfield wastewater involves removing oil spill, dispersible oil, emulsified oil and suspended materials; separating suspended materials and solid particles; reducing viscosity of sewage to less than 0.4 mPa.s; microbiologically degrading polymer and petroleum in sewage with natural microbiological strains obtained by manual selection and domestication; filtering through ultrafiltration membrane to remove bacteria, virus and suspended materials in the sewage; and filtering inorganic ions through reverse osmosis membrane. Manual selection and domestication of microorganism for degrading polymer includes collecting polymer-containing sewage (250 ml) in oilfield, adding polymer (1000 mg/L) for oil displacement of oilfield, cultivating and domesticating for 3 months, purifying and separating strains, and separating 1 Bacillus strain (CGMCC 3345). Manual selection and domestication of microorganism for degrading petroleum includes collecting oil-containing sand sample (1 g) in oil field, pouring in a conical bottle filled with petroleum (500 mg/L) and distilled water (100 ml), cultivating and domesticating for 1 month, purifying and separating strains, and separating 1 Bacillus strain (CGMCC 3344). INDEPENDENT CLAIMS are included for a Bacillus strain (CGMCC 3345) and a Bacillus strain (CGMCC 3344).