Study On Screening And Treatment Effect Of Waste Drilling Mud Degradation

High-efficiency waste drilling mud degradation strains for were screened and separated from the enriched and cultivated waste drilling mud fluid.The degradability of the selected strains on crude oil was evaluated,and the culture conditions of the selected strains were optimized.The treatment effect of waste drilling mud was evaluated by the solid bacterial agent of the screened strain.The treatment effect of screening strains for waste drilling mud was evaluated using solid bacteria agents.The main results obtained in this study are as follows,hoping to provide research basis and technical support for the biologically harmless treatment of waste drilling mud.(1)Two high-efficiency degrading bacteria,named D₃ and R respectively,were separated and screened from the waste drilling mud.Through morphological characteristics,physiological and biochemical analysis and 16S r DNA sequence analysis,the two strains were identified as Bacillus velezensis and Pseudomonas aeruginosa.(2)Strains Bacillus velezensis D₃ and Pseudomonas aeruginosa R could both produce glycolipid biosurfactants with petroleum hydrocarbons as the sole carbon source.The surface tensions of the two fermentation broths were 27.1 m N/m and 27.5 m N/m,respectively,and the emulsification index were 44.6%and 24.9%,respectively,which had a good emulsification effect on petroleum hydrocarbons.(3)The suitable growth conditions for the strains Bacillus velezensis D₃ and Pseudomonas aeruginosa R were the initial p H 5.0?7.0,25?40?and the 0.5%?7%salinity.According to the growth curve,the R strain growed faster than the D₃ strain.The time for the former to reach the stable phase was 32 h,and the latter was 44 h.The growth pattern of the R:D₃=1:1 compound strain was more consistent with that of the R strain.The maximum cell density was reached at 32 h of culture.(4)The strains Bacillus velezensis D₃ and Pseudomonas aeruginosa R both had good degradation properties for petroleum hydrocarbons.Under suitable growth conditions,within10 days,2.5%of crude oil could be degraded by strain D₃ with the 56.2%crude oil degradation rate,while 3.5%of crude oil could be degraded by strain R with the 52.9%crude oil degradation rate.The strain D₃and R had a synergistic effect on the degradation of crude oil and could be used in combination.The crude oil could significantly degraded by the R and D₃ mixed bacteria agent(1:1,w/w)with a degradation rate of 62.4%.(5)The R strain,D₃ strain and their mixed bacteria agent(1:1,w/w)were inoculated into the solidified material bran at a ratio of 10%,and then fermented for 72 h to prepare a composite solid inoculum.The number of bacteria in the solid bacterial agent was 7.5×10⁸CFU/g,4.3×10⁸ CFU/g and 1.1×10⁸ CFU/g,respectively.(6)The solid mixed bacterial agent had a good treatment effect on waste drilling mud.For the polysulfonated drilling mud with an initial oil content of 4.34%,after 90 days of treatment with the solid mixed bacterial agent,the oil content in the mud was reduced to1.48%,and the degradation rate reached 65.8%.The mineral oil content meets the standard?Pollution Control of the Comprehensive Utilization of Oil and Gas Field Drilling Solid Waste?Xinjiang Uygur Autonomous Region Local Standard(DB 65/T 3997-2017),and the final number of bacteria in the mud was as high as 10¹¹CFU/g;For polysulfonated drilling mud with an initial crude oil content of 0.42%,after 80 days of treatment with the solid composite bacterial agent,the crude oil content could be reduced to 0.21%and the degradation rate was 71.4%.The treated mineral oil and heavy metal content all meeted the relevant standards of?Agricultural Sludge Pollutant Control Standard?(GB4284-2018)B-grade sludge products.Both the number of bacteria and actinomycetes in the mud reached 10¹¹ CFU/g.