Experimental Study On The Treatment Of Oily Sludge In Oil Refinery By Ultrasonic-microbial-electrochemical Coupling

Given the increased output of oil sludge in refinery and the difficulty of degradation in a single process,this study took the refinery scum sludge and biochemical sludge of Nanjing Jinling Branch of Sinopec as the research object.It carried out experimental research on the treatment of oil sludge in a refinery by ultrasound-microbial-electrochemical coupling method.The main research contents include:Two kinds of oily sludge were pretreated by ultrasonic wave.One strain of oil-degrading bacteria was screened from two types of oily sludge,and its growth characteristics and degradation characteristics were studied.The dry powder bacteria agent was prepared to explore the difference of viable bacteria number and degradation rate under different preparation conditions.The degradation simulation test of the two kinds of oily sludge was carried out by the ultrasound-microbial-electrochemical coupling method.The physical and chemical properties of oily sludge,the changes of soil typical enzyme activities,and the growth and distribution of hydrolytic bacteria with different electric field intensities decreased were analyzed during the test process.The degradation effect of the two kinds of oily sludge after 50days of operation of the equipment was investigated.The main findings are as follows:(1)The order of influence of process parameters of the ultrasonic method was power<time<temperature<frequency;When the ultrasonic power was 60 W,the ultrasonic time was 10 min,the ultrasonic temperature was 60?,and the ultrasonic frequency was 3 times,the removal rates of petroleum substances in the scum sludge and biochemical sludge were31.13%and 17.46%,respectively.After ultrasonic pretreatment,the long chain of petroleum hydrocarbons in oily sludge was destroyed,the intergranular space increases,the viscosity decreases,and the texture become loose.(2)YJ bacteria(Enterobacter cloacae subsp)were screened out from the scum sludge.The optimal growth and degradation conditions were pH7.0,salinity 3%,inoculation volume 5%,and liquid loading volume 30 mL.Under these conditions,the degradation rates of scum oil sludge and biochemical sludge crude oil medium were 70.79%and 89.37%,respectively,and the degradation followed the first-order kinetic model.FH strain(Shewanella putrefaciens strain)was screened out from the biochemical sludge.The optimal growth and degradation conditions were pH 7.0,salinity 3%,inoculation volume 8%,and liquid loading volume 30mL.Under these conditions,the degradation rates of scum oil sludge and biochemical sludge crude oil medium were 65.73%and 85.89%,respectively,and the degradation followed the first-order kinetic model.(3)Optimum preparation conditions of YJ immobilized bacterial agent:In the 100 mL immobilized medium,1.5 g sorghum shell biochar carrier with the particle size of 30-80 mesh was added and pyrolyzed at400?for 8 h.Then,5%YJ bacteria solution was added and fixed at 200r·min^-1 at 25?for 24 h.After freeze-drying,the immobilized bacteria was prepared,and the number of bacteria was about 9.34×10⁹ cfu·g^-1.Optimum preparation conditions of FH immobilized bacterial agent:100 mL immobilized medium was added with 3.0 g sorghum shell biochar carrier with the particle size of 30-80 mesh,which was pyrolyzed at 200?for 1h,and then connected with 5%FH bacteria solution,fixed at 200 r·min^-1and 25?for 18 h.After freeze-drying,the immobilized bacteria was prepared,and the number of bacteria was about 5.46×10¹⁰ cfu·g^-1.(4)Under the action of the direct current electric field,the pH of the sludge in the cathode area increased significantly,and the acidification of the sludge in other locations existed.When water migrated from anode to cathode,the water content decreased from cathode to anode,and the changing trend of oil content was similar to that of water content.TOC content,respiration intensity,and the activities of two enzymes were increased.Different electric field intensification had other promoting effects on the growth of degradation bacteria.The optimal electric field intensification of YJ and FH bacteria was 200 V·m^-1.(5)In the simulation test of the ultrasound-microbial-electrochemical coupling method,on the one hand,the scum oil sludge after ultrasonic pretreatment would naturally degrade,and the degradation rate was 2.51%.The degradation rate was increased to 3.62%after coupling electric field only,23.93%after adding YJ bacterial agent only,and 21.68%after adding FH bacterial agent only.After connecting the electric field,the degradation rate of YJ bacterial agent was increased to 28.17%,the final degradation rate was 51.49%,and the oil content was 187.80 mg·g^-1.After coupling the electric field,the degradation rate of FH bacterial agent was increased to26.35%,the final degradation rate was 50.26%,and the oil content was192.56 mg·g^-1.On the other hand,the biochemical sludge treated by the ultrasonic wave will also degrade naturally,with a degradation rate of3.35%.The degradation rate is increased to 5.61%after coupling electric field only,45.93%after adding YJ bacterial agent only,43.93%after adding FH bacterial agent only,and 58.71%after connecting electric field with YJ bacterial agent.The final degradation rate was 65.92%,and the oil content was 35.03 mg·g^-1,and the degradation rate was increased to 58.66%after FH strain coupling electric field,and the final degradation rate was65.88%,and the oil content was 35.07 mg·g^-1.