Research and industrial application of microbial treatment technology for heavy oil-produced water

Addressing the significant challenge of achieving discharge standards for heavy oil produced water, this study investigated the composition of organic pollutants and determined the contribution rate of heavy oil to the Chemical Oxygen Demand (CODcr) in the produced water. Concurrently, indigenous microbial strains from the heavy oil reservoir were screened and evaluated, leading to the selection of three highly efficient oil-degrading strains. The removal efficiencies of these three strains for petroleum hydrocarbons and CODcr were investigated. Furthermore, pretreatment and biological treatment processes for the produced water were developed. The results demonstrated that the three selected high-efficiency oil-degrading strains achieved petroleum hydrocarbon degradation rates exceeding 78% and CODcr degradation rates surpassing 55%. By enhancing the pretreatment process for heavy oil produced water, the CODcr concentration in the treated effluent was reduced to ≤ 300 mg/L. The implementation of a "hydrolysis acidification + biological contact oxidation" process achieved a 57.1% CODcr removal rate following microbial treatment, establishing a foundation for subsequent advanced treatment to meet discharge standards. Analysis of the influent and effluent components from the microbial treatment process verified that the microorganisms effectively degraded both light and heavy hydrocarbons in the heavy oil produced water.