Study On The Remediation Of Petroleum Hydrocarbon Contaminated Soil By Persulfate Oxidation Combined With Biodegradation

This study combined chemical oxidation and microbial remediation technology in the remediation of petroleum hydrocarbon contaminated soil to produce synergistic effect.As a new type of efficient oxidant,persulfate has the advantages of high stability,good water solubility,strong oxidation.Persulfate has been widely used in the remediation of soil and groundwater contaminated by organic matter.In this paper,single microbial remediation,single chemical oxidation remediation and chemical oxidation combined with microbial remediation were studied respectively.The feasibility of coupled remediation was proved and the optimal coupled remediation scheme was explored by comparing the three remediation methods through relevant indicators.The following conclusions were obtained from the experiments:（1）In microbial remediation experiments,adding nutritional agents could significantly enhance soil microbial activity and promote soil total petroleum hydrocarbon（TPH）degradation.Compared with the control group,the degradation efficiency of TPH increased by 47.14%and 34.55%after adding nutritional agents Y1and Y2,respectively,and the degradation efficiency of easily degradable components（C8-C16）and refractory components（C18-C22）increased synchronously.Compared with the control group,the degradation efficiency of components C8-C16 increased by23.22%and 18.62%,while C18-C22 increased by 47.52%and 33.03%after adding nutritional agents Y1 and Y2.At the genus level,the community structure changed significantly after repaired.The most dominant bacteria changed from Arthrobacter to Novosphingobium and Cavicella.Moreover,a new petroleum hydrocarbon degrading bacterium Nocardioides was derived from enrichment,which was proved to be a species capable of producing biosurfactant.Nocardioides has been proved to be a strain capable of producing bioactive agents,which is conducive to increasing the water solubility of organic pollutants,thus increasing their bioavailability and improving the degradation effect of petroleum hydrocarbons（2）In the remediation experiments of alkali activated persulfate oxidation,CaO and CaO₂showed stronger basicity than Na OH.However,a large amount of heat release resulted in the thermal decomposition of sodium persulfate（PS）,which limited its reaction with organic contaminants.In addition,CaO₂dissolved in water produced Ca（OH）₂precipitation,which hindered the transport of oxidants in the soil medium,and also affected the remediation effect to some extent.Na OH as an alkali source activated sodium persulfate could play the best remediation effect,and the optimal activation ratio of PS/Na OH was 1/4（mass ratio）.It was found that the treatment with1%PS/Na OH（mass ratio）of 1:4 was better than the control group in the degradation of TPH and n-alkanes.At the end of the treatment,the soil TPH concentration was reduced to 866.22mg/kg,which met the soil pollution control standard.Therefore,1%PS was selected after comprehensive consideration.The optimal alkaline activation scheme was to restore petroleum hydrocarbon contaminated soil with the mass ratio of PS to Na OH of 1:4.（3）In activated persulfate oxidation combined with microbial remediation experiments,activation treatment could accelerate the decomposition of PS,and the PS consumption efficiencies of Fe²⁺,H₂O₂,Na OH and heat（50℃）activation at 28d were61.39%,62.84%,83.17%and 100%,respectively,which were faster than that of unactivated control group（49.33%）.Only unactivated PS and thermally activated PS showed better coupling effect.At the end of the 28d experiment,the TPH degradation efficiencies of PS,PS+Y1 and PS+Y2 groups were 64.24%,79.22%and 68.53%,respectively.The degradation efficiencies of soil TPH in Ht PS,Ht PS+Y1 and Ht PS+Y2groups were 58.31%,63.21%and 74.05%,respectively,and only unactivated PS could achieve simultaneous degradation of easily degradable and refractory components in the pre-oxidation stage.The coupling remediation of thermal activated PS showed that the degradation effect of refractory C18-C22 components was improved.The final degradation efficiencies of C18-C22 components by Ht PS,Ht PS+Y1 and Ht PS+Y2were 42.46%,62.02%and 73.5%,respectively,which increased 19.56%～31.04%compared with the control group.After PS oxidation,soil species richness and community evenness decreased significantly,which were recovered after adding nutrient agents.After PS oxidation,soil enriched and derived more kinds of petroleum hydrocarbon degrading bacteria,such as Paenibacillus,Xanthomonas,Arthrobacter and Pseudomonas.The effects of the two nutrient agents on soil bacteria were similar,and the most dominant bacteria were Bacillus and Nocardioides after coupled restoration.