Screening Of Microorganisms For Efficient Disposal Of Oily Sludge And The Construction Of The Fermentation System

With the development of industry,the demand for oil is increasing,resulting in the production of more and more oily sludge,which is about 3 million tons per year.Oily sludge mainly contains aged crude oil,heavy metals,suspended solids and benzene series.At present,the main treatment methods are physicochemical method(chemical hot washing,solvent extraction,conditioning mechanical separation technology)and biological method.If the physicochemical method is not handled properly,it will cause secondary pollution to the environment.Therefore,the biological treatment of oily sludge has become a research hotspot at home and abroad.The key of biological treatment is the screening of efficient degradation strains,degradation mechanism and construction of fermentation system.In this paper,nine crude oil-degrading strains were isolated from the oily sludge of an oil field in Shandong Province,contaminated soil and laboratory mixed strains.The compound bacteria were constructed by orthogonal experiment,the immobilized bacteria were prepared by using biochar as the substrate.The optimal fermentation conditions and the degradation effect of immobilized bacteria on crude oil in oily sludge were studied,and the degradation mechanism of immobilized bacteria was preliminarily explored.The conclusion is as follows:(1)After enrichment culture and primary screening,nine strains were isolated and purified,and they were named SF1,SF2,SF3,SF4,SF5,SF6,SF7,SF8 and SF9.By 16S r RNA analysis,SF1 was Ochrobactrum intermedium,SF2 and SF8 belonged to Enterobacter spp.,SF3 and SF7 belonged to Acinetobacter spp.,SF4,SF5,SF6 and SF9 belonged to Pseudomonas spp.Among them,strain SF1 had the strongest degradation ability to crude oil,with a degradation rate of 48.73%.Strains SF2,SF7 and SF9 had stronger degradation ability,with degradation rates of 41.90%,45.35%and 32.25%respectively.The degradation rates of other strains were also higher than 20%.(2)The orthogonal experiment showed that the oil degradation effect of the bacteria group composed of SF1,SF2,SF3,SF4,SF5,SF6,SF7 and SF9 with the addition of2:1:1:1:1:1:2:2 was better than that of a single strain.The bacteria group was the best efficient bacteria group with the degradation rate of 57.88%.The effects of inoculum,p H,oil concentration,and salinity and P source on crude oil degradation were investigated.The results showed that when inoculum was 13%,p H was 7,crude oil concentration was 0.25%,and P source was KH₂PO₄+Na H₂PO₄·H₂O,the crude oil degradation rate reached 60.77%.(3)With biochar as the adsorption carrier,the highly effective bacteria were fixed on the biochar.The results showed that when the pine biochar was the best immobilized carrier,the immobilized time was 18 h,the rotation speed was 150 r/min,the optimal temperature was30?35?,and the p H was 7,the degradation rate of the biochar immobilized bacteria on the crude oil reached 65.76%.(4)Scanning electron microscopy and Fourier transform infrared spectroscopy were used to characterize the performance of biochar immobilized bacteria.The results showed that there were many pores with different pore sizes on the surface of biochar,and the biochar also had certain adsorption performance to crude oil,and the surface mainly had functional groups such as-OH,-CH and C-O in hydroxide group.The degradation of crude oil by immobilized bacteria is due to the adsorption of biochar on the one hand and the degradation of microorganisms on the other hand.In contrast,the degradation of high-efficiency bacteria is dominant.