Enhanced Bioremediation Of Crude Oil Contaminated Soil Using In Suit Modified Fenton Oxidation

Stepwise Fenton oxidation avoids disadvantages which produced by traditional Fenton Fenton oxidation.Such as decreasesing H₂O₂ stability and damaging bacteria.Therefore,in this study,we use two kinds of oil-contaminated soil.Three kinds of H₂O₂ concentration and four kinds of stepwise Fenton oxidations were preformed.In order to optimize operating conditions of stepwise Fenton oxidation.In addition,adopts four kinds of stepwise Fenton per-oxidation.No inoculating,inoculating with native bacteria and foreign bacteria was performed after per-oxidation.In order to measured the effects of indigenous bacteria remained during stepwise Fenton oxidation on nutrients mobilization,subsequent bioremediation and bacteria recovery.And decreased H₂O₂ concentration of pre-oxidation,to find the limited value of indigenous bacteria and nutrition whih promote bioremediation.In order to find the suitable stepwise Fenton pre-oxidation method.The conclusions of experiments are as following:(1)After stepwise Fenton oxidation,the remove efficieny of TPH improved significantly and oxidation efficiency of SOM decreased.The suitable pre-dosage of H₂O₂ is 225mM-300mM,and the suitable addition times is 3-4.In addition,soil organic matter(SOM)is the essential factor to produce hydroxyl radicals rather than particle size.Higher soil organic matter,greater the hydroxyl radical production.And most hydroxyl radicals were producted in the first stage.(2)Fe³⁺was reducted by hydroxylamine hydrochloride,it improved the utilization of iron.The TPH removal efficiency of S1 and S2 has been up to 64%and 75%.And the removal efficiency of main component(C₁₆-C₂₆)increased 20%Relative to adding Fe²⁺twice.(3)The concentration of TOC and NH₄⁺-N were respectively 9-11 times and29-36 times higher after Fenton oxidation,promote the remove efficiecy of long chain molecules.Combine with biodegradation,the remove efficiency of TPH increased13-37%relative to untreated soil.However,with high concentration of H₂O₂,indigenous bacteria count dncreased to 10³ cfu/g soil.The biodegradation of most alkenes has significant decreased.(4)Under the condition of low or high concentrations of H₂O₂ and Fe²⁺will release of high,medium,low three different levels of nutrition,but residual indigenous bacteria populltion and oil oxidation efficiency varied greatly.When adding low concentrations of H₂O₂,oil oxidation efficiency is low but residual indigenous bacteria population is high.When adding high concentrations of H₂O₂,oil oxidation efficiency is high but residual indigenous bacteria population is low.(5)When the remaining indigenous bacteria population is higher than 10⁷cfu/g,the soil remediation can be promoted under the condition of low nutrition.When the remaining indigenous bacteria populationis less than 10⁵cfu/g,only high nutritional conditions can restore the indigenous bacteria activity,and promote soil remediation..In addition,the study found in three nutrition levels,microbial activity,nutrient utilization,and TPH removal efficiency in remaining more indigenous bacteria system were higher than in less indigenous bacteria system.(6)Crude oil contaminated soil with long chain hydrocarbon need high nutrition.In high nutrition condition,biodegradation of all alkanes(C₂₉and C₃₀)were well.In medium nutrition condition,biodegradation of two kinds of alkanes(C₂₉and C₃₀)were limited.In low nutrient condition,biodegradation of five kinds of alkanes(C₂₆-C₃₀)were limited.However,due to TOC wil contend with TPH,the main alkanes of C₁₈-C₃₀degradation rate lower than the medium nutritional condition.Thus the medium nutrition is the best condition.