Study On The Effect Of Delayed Pre-oxidation Combined With Subsequent Petroleum Bioremediation

Fenton oxidation technology is one of the effective ways to degrade petroleum-contaminated soil with high efficiency and low cost.The traditional Fenton method is often subject to the adsorption of petroleum in the state of adsorption and the presence of free radicals in the treatment of petroleum pollution.the degradation effect was limited by the desorption rate and free radicals generated in the liquid phase severely.Previous studies have found that the hydrogen peroxide can be catalyzed not only in the solid phase,but also produce·OH directly oxidizes petroleum contaminants,which also less harmful to soil microorganisms.This study found that the degradation effect of TPH is better in the solid phase system,when the decomposition rate of H₂O₂is slow.And the maximum instantaneous intensity duration of·OH is prolonged,so it is called a delayed system.Therefore,the characteristics of solid phase iron formation technology and catalytic oxidation mechanism are further studied.The effects of delayed pre-oxidation and traditional pre-oxidized solid-phase iron Fenton technology on indigenous microorganisms are analyzed.Finally,the actual value of pre-oxidation combined with subsequent bioremediation of petroleum is obtained.The following conclusions are drawn through research:(1)The delayed oxidation can be promoted in high-iron manganese oxidation state iron.In the soils of the eastern suburbs and northern Shaanxi,the addition of humic acid promoted the formation of Fe-Mn oxides,with a ratio of 79.1%and 84.1%;and in the soil of Jiangsu,the addition of fulvic acid promoted the formation of Fe-Mn oxides,with a ratio of 80.1%.In addition,the formation of Fe-Mn oxides can be further promoted by adding organic matter.In the Fe-Mn oxides system the decomposition rate of H₂O₂is relatively low,and the maximum instantaneous intensity of·OH lasts for a long time.(2)Oil soil with high petroleum hydrocarbon content can be repaired in delayed oxidation system.The removal rate of the high oil system(24200 mg/kg)was15.2%-30.6%higher than that of the low oil system(18000 mg/kg).The oxidation removal rate of TPH is up to 62.5%.(3)the oxidation of long-chain hydrocarbons can be effectively promoted by graded dosing when the total dosage of H₂O₂is constant.In the delayed oxidation system,when the total amount of H₂O₂is 1800 m M,the TPH oxidation rate of the four-time addition is 62.1%,which is 1.24 times of the one-time addition.And the removal rate of the long-chain hydrocarbon is 1.34.times in the delayed oxidation system,compared to the trandition system.The TPH removal rate was increased to84%after adding hydroxylamine hydrochloride,(4)The oxidation rate of TPH increased with the increase of H₂O₂concentration.The THP chemical and biological repair rate was the highest when the concentration of H₂O₂was 1350 m M.At this time the delayed oxidation system was 64.7%,which was 10.3%higher than that of the traditional system.The removal rate of short-chain hydrocarbons in the delayed system is 4.7%?10.5%higher than that of the traditional oxidation system,and the long-chain hydrocarbons are 3.8%?11.5%higher.(5)The external bacteria effectively overcome the problem of reduced TPH repair efficiency in the late stage of bioremediation under high H₂O₂concentration.In the delayed oxidation system,when the dosage of H₂O₂was 1800 m M,the external bacteria could increase the biodegradation rate of TPH by 18.6%.(6)Low iron content and low H₂O₂concentration conditions are more conducive to the occurrence of delayed oxidation.When the dosage of H₂O₂is 900 m M and the amount of iron is 2g,the removal rate of TPH can reach 56.9%.The biochemical combined removal rate of long-chain hydrocarbons in the delayed oxidation system is16.0%-39.3%higher than that of the traditional oxidation system.