Research On Process And Breeding Of Bacterial Community Of Microbial Treatment On Oilfield Produced Water

This research aimed at selecting and cultivating highly active, stable and highly adaptable microbes to degrade TPHs and SS efficiently from oil field produced water, which provided basis for microbial treatment of produced water by compounding and optimizing the process craft.In this study, TPHs content and SS content of produced water from oil fields of all stripes were measured by double wavelength UV spectrophotometry and millipore membrane filter technique, then the pH value, species and quantity of microbial were analyzed. Dominant strains were separated by enrichment culture, preliminary screening and second screening. Then they were tested by morphological, physiological and biochemical and 16S rRNA sequential analysis to ensure their species. Strain ratio was optimized by orthogonal test. The effect of aeration time, temperature, pH value to the treatment efficiency of produced water was studied by indoor simulation experiment. After these, the treatment conditions were optimized by response surface experiments with Design-Expert. Field test was designed according to the result of indoor simulation experiment. Then TPHs and SS content were monitored for 15 days after clean water and sewage cultivation to analyze the stability of water and measure the corrosive characteristics of the water.The research find that TPHs and SS content of sewage from different oil field varied remarkably, pH between 7.6-9.5, microbial biomass 102-103 CFU/mL, most of the microbes were bacteria and yeasts. There were three kinds of dominant microbes PW01, PW04 and PW06. PW04 degraded TPHs most efficiently that the degradation rate reached to 64.8%. And PW06 degraded SS most efficiently that the degradation rate reached to 50.8%. These three strains were Bacillus subtilis, Sphingobacterium multivorum and Pseudomonas fluorescens after being appraised, result of orthogonal experiment showed the optimum compound:B. subtilis PW01:S. multivorum PW04:P. fluorescens PW06=23:1, inoculum concentration 1.0%,1.5%and 0.5% respectively. Results of response surface experiments showed the optimum process condition:aeration treatment 6 h, temperature 37 ℃, pH 7.5, TPHs degraded 93.35%、SS degraded 89.62%. After field test, the TPHs content of effluent water was between 6.3-8.6 mg/L, whose degradation rate reached to 90%, and the SS was between 7.2-8.5 mg/L, whose degradation rate reached to 85%. And the effluent water was non-corrosive.TPHs and SS content of sewage disposed by compound microbes all reached to the national standard, relevant rules of industry and oil field corporation. Disposed water were quality-stable and non-corrosive, which could be reinjection or be drained away directly.