| Nowadays,energy and environment is one of the most important topics in the world.The Chinese government also pays more and more attention to the problems of environmental pollution in the process of energy development.During oil and gas exploring process,a large number of waste drilling muds,the key environmental pollutants,were produced.How to deal with the waste drilling mud effectively,and recycle of pollutants has been become a hotspot in recent years.In this paper,the bioremediation of waste drilling mud under the condition of pot experimentwas performed;we chose the waste polysulfonate drilling muds as treating materials,and mixed the drilling muds and soil as the ratio of 1:2;and then two treatments were designed,i.e.,inoculation of mixture of five drilling mud degrading bacteria inoculant(T1)and both inoculation of mixture of five drilling mud degrading bacteria inoculant and combing with cultivating plants(T2).After 180 days growth,the soil sample was collected and the degradation effect,including variation of pollutant concentration and microbial properties was determined.The results were as the followings:1.The concentration of chromaticity,turbidity,COD,Cl",SO42-and oil in the soil extraction liquid of the mud-soil mixture decreased obviously.The removal rate of Cl-and SO42-in T1 and T2 were 87.78%and 84.72%,65.13%and 61.48%,respectively;the removal rate of COD in T1 and T2 was 91.31%and 94.03%,respectively.The removal rate of oil in T2 was 82.94%,was higher than that of T1.The final degradation effect on waste drilling mud of T2 was better than that of T1.2.The soil extraction liquid of T2 had not obvious inhibitory effect on plant seed germination rate:the germination rate was higher than T1.The clover and alfalfa seeds had quite low tolerance to mud contaminants,in untreated mixture system,the germination rate were very low,which was 20%and 12%,but the germination rates increased significantly in treated mud-soil mixture systems which could reach to 70%-90%.Conversely,the seeds of wheat,ryegrass,corn and soybeans had high germination rates,the mud contaminates could hardly inhibit the seed germination;they had strong tolerance to mud contaminants.3.As the number of cultured microorganism.in T2.the number of bacteria(pH7)was 11326×104cfu/g,and the quantity of high pH tolerant bacteria(pH9)was 1091×104cfu/g,the fungi was 36.76×104cfu/g,and the actinomycetes was 815×104cfu/g.In a word.the number of cultured microorganism in treatment 2 was more than the treatment 1,and the bacterial diversity index,and soil microbial biomass carbon-nitrogen were higher than T1 as well.4.The soil DNA was isolated and the bacteria community was determined by Miseq technique,then the heatmap dendogram was constructed,the results showed that,at the genus level of similarity,the bacteria community was very different,genus Lysobacter.Gaiella,Arenimonas,Thermomonas,Xanthomonas,Sphingomonas and lamia were dominant communities in CK soil,however,genus Bartonella,Luteimonas,Brevundimonas.and genus Nitrospira,Bacillus,Achromobacter,Mesorhizobium,Flexibacter and Pseudomonas were predominant one in T1 and T2 soil.5.Polyphenol oxidase and dehydrogenase activity in bioremediation soil were significantly higher than the control soil,and the enzyme activity in T2 was higher than T1.Especially,we found there was a significant positive correlation between soil enzyme activity and diesel degradation rate.Therefore,the plant and degrading bacteria combined could reach a higher conversion efficiency of organic matter,microbial activity was stronger as well.In contrast of bioremediation soil and control soil.the former's physical and chemical properties of the nutrient content,i.e.NPK,was higher,pH was neutral,the conditions of physical and chemical properties was more suitable for the growth of microorganisms and plants than that of untreated one,and the microorganisms and plants also accelerated the conversion speed and efficiency of pollutants in the mud. |
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