Treatment of waste drilling mud by domesticated complex microbial flora

Abstract:

[Background] The waste drilling mud in the oil field has high oil content, complex pollutant and serious environmental hazards, and existing technologies cannot meet the requirements of the increasingly developed petroleum exploitation industry in the treatment of waste drilling mud. Biological treatment of waste drilling mud has the advantages of simple process and low cost, but it also has some limitations, including poor broad-spectrum, long processing cycle, low petroleum degradation rate and the fluctuation of sludge properties affects the active stability. [Objective] To improve the biological treatment of waste drilling mud, a microbial community with high activity and high environmental tolerance was constructed, and the comprehensive performance and genetic stability was analyzed. [Methods] Through directional enrichment, induction and acclimation methods, the efficiency of petroleum hydrocarbons emulsification and degradation was expected to be improved, and the feedback inhibition of co-metabolic substrate and quorum sensing system sensitivity were expected to be reduced. We analyzed the structure and the active members' types of the microbial community, and studied the corresponding relationship with emulsification-degradation of petroleum hydrocarbons. [Results] An active microbial community was enriched from drilling waste mud containing more than 12 g/kg oil, more than 80% aromatics-colliod-asphalt and more than 8 g/kg salt. The main members include Pseudomonas, Rhizobia, Rhodobacter and Dethiobacter alkaliphilus, with the ratio of 27.44%, 20.73%, 8.54% and 7.93%, respectively. During the continuous acclimation of more than 22 generations, the quantity of Pseudomonas, Alishewanella and Halomonas was accounted for more than 92.72%, the structure and activity of the microbial community was stable. When the waste drilling mud was treated for 5 days by the active community, the oil content of soil decreased from 12403 mg/kg to 42 mg/kg, the comprehensive oil removal efficiency was 99.67%, and the petroleum hydrocarbon degradation rate was 68.9%. The content in crude oil saturated soil was analyzed before and after microbial community action, the original oil content was 261 g/kg, and the oil content after treatment was 305 mg/kg, deoiling rate was 99.88%. [Conclusion] After acclimation, the microbial community has stable activity, strong tolerance to high salt environment, the active microbial community has strong industrial application potential in drilling waste mud, oily soil and sludge pollutant treatment.

Key words:drilling mud;crude oil degradation;active microbial community;community structure