Microbial Immobilization Of Modified Wheat Straw And Its Biodegradation Of Drilling Waste Mud

This paper mainly focused on the characteristics of drilling mud with high COD,high petroleum hydrocarbon content,difficulty in handling,and other pollution characteristics.On the basis of free microbial treatment,adsorption-immobilized microorganisms were used to treat drilling mud.The research mainly studied the screening and identification of high-efficiency petroleum-degrading bacteria,the optimization of carrier material modification conditions,the determination of the conditions for the preparation of immobilized microorganisms,and the tolerance to alkaline environment,salt content,temperature,Cr,Pb of immobilized and free bacteria.The effect of immobilized microorganisms based on modified straw on the treatment of drilling mud was studied.The high-quality oil-degrading bacteria were screened from the drilling mud by means of domestication of crude oil,and the selected strains were observed and identified,their growth curves were determined.According to the degradation rate of petroleum hydrocarbons,the composition of microorganisms used for immobilizing microorganisms was determined.The results showed that three strains were selected and named as X-1,X-2,and X-3.The 16S rDNA analysis showed that all of them were Ochrobactrum.The microorganisms used for the immobilized microorganisms were composed of X-1,X-2 and X-3 were mixed in a volume ratio of 2:2:1 to obtain a mixed broth.The wheat straw was modified to study the optimum modification conditions of the composite modifier on the basis of studying the optimum modification concentration,modification time,and modification temperature of a single modifier,and various factors were determined by response surface methodology.At the same time,the preparation conditions of immobilized microorganisms were studied.The results showed that when the ratio of straw and modifier was 2:15(w:v),the best modification condition was 0.1 mol/L sodium hydroxide solution and 1 mol/L hydrogen peroxide in volume ratio of 3:1 mixed solution,modified at 30 ? for 60 min.The influence of the three factors on the modification results is:volume ratio>modification temperature>modification time.The optimal preparation conditions were:30?,130h/min adsorption for 12h.Tolerance experiments showed that the microbiological adsorption immobilization technology can improve the tolerance of microorganisms to extreme environments to a certain extent,including extreme alkaline environment,salt content,temperature,Cr content,and Pb content.It provided references for the application conditions of immobilized microbial degradation drilling mud.When the biodegradation processing time was 100 d,the COD of the immobilized microbial sludge decreased from 1900.9 mg/L to 932.5 mg/L,the petroleum hydrocarbon decreased from 3424.8 mg/kg to 1143.6 mg/kg,and the soluble salt content increased from 27.4%to 21.8%,and the degradation effect of the three substances was higher than that of the free bacteria treatment group.When the immobilized microorganisms were combined with soil to repair drilling mud for 100 days,COD decreased from 923.6 mg/L to 182.7 mg/L,the degradation rate was 80.2%;petroleum hydrocarbons decreased from 1433.6 mg/kg to 263.5 mg/kg,the degradation rate was 81.6%;soluble salt content decreased from 10.11%to 7.73%,the degradation rate was 23.5%.