| Petroleum is a complex mixture of diversified hydrocarbons,which is known as"industrial blood" and "black gold".Meanwhile,petroleum is the essential and strategic energy in the industrial production and daily life.Due to improper operation or accident leakage,et al.,oil spills or emissions occur frequently in the process of the petroleum exploration,extraction,transport,refining and storage,which give rise to serious environmental pollution.It causes potential risks not only on human health but also on the environment.Currently,soil with oil contaminated has become a global environmental problem,especially the oily sludge,which has become the research hotspot to scientists.Because of its low cost,environmentally friendship,and high-efficiency,the bioremediation techniques for petroleum contaminated soil are particularly popular in which bioaugmentation is most commonly used in practice.However,the methods and strategies in bioaugmentation technology in our country is not mature,even absent.The number of the companies to provide effective technology for oily sludge treatment is comparatively little,and most products are not very effective in practical application.The related studies for oily sludge treatment is limited to laboratory shaking flask level,lack of practice at field scale.Meanwhile,many factors can affect the success of bioaugmentation,such as the metabolic p6tential of the microorganism strain and the biological availability of pollutants et al.Hence,the study for site treatment of oily sludge and related mechanism is quite essential for establishing effective bioaugmentation strategyIn this study,the oily sludge derived from the wells in Chinese Petroleum's Changqing Oilfield Company Yuancheng operating area oil recovery plant was chosen as treatment object.The solid inoculum of Bacillus sp.,Acremonium sp.and Phanerochaete sp.were used as the bioaugmentation agent.Different fungus-bacterium consortia and strategies(one-off bioaugmentation and sequential bioaugmentation)handling oily sludge have been applied in this study.Furthermore,in order to study the functional mechanism of bio-surfactants rhamnolipid and fungi in the bioaugmentation treatment,this research selected the mixed polycyclic aromatic hydrocarbons(PAHs)as pollutant models,including naphthalene(NAP),fluorene(FLO),Phenanthrene(PHE),anthracene(ANT)and fluoranthene(FLA).This experiment studied the solubilization of mixed PAHs with the bio-surfactants rhamnolipid supplementation.Moreover,the study combined the rhamnolipid with the dispose of mixed PAHs contaminated soil by microorganism consortium to evaluate the effectiveness of rhamnolipid in actual soil bioremediation.Meanwhile,based on the features of fungal-bacterial consortium in field test,the research established a pollutant transfer model of Acremonium sp.with the tetracyclic PAHs fluoranthene as model pollutant to explore the function of Acremonium sp.in fungi-bacteria consortium at the process of bioremediation.In addition,the research further studied the tolerant capacity of Acremonium sp.and the varying pattern of fluoranthene transfer and removal rate by Acremonium sp.with different heavy metals supplementation.The results are as follows:(1)The degradation efficiency of degradation efficiency showed difference with different bioaugmentation treatment strategies in treatment of oily sludge.The sequential bioaugmentation of fungal-bacterial consortium has confirmed to improve significantly the total petroleum hydrocarbons(TPH)removal rate(p<0.01).The high microbial biomass and metabolic activity were observed simultaneously with this strategy.The best treatment group was sequential bioaugmentation treatment group with the fungal-bacterial consortium composed of Bacillus sp.,Acremonium sp.and Phanerochaete sp..After 60 days,the removal rate of TPH of this treatment reached 91.24±1.56%,even though the initial oil content in the contaminated soil summed up to 119 260 mg/kg.(2)Due to the variance of metabolic enzymes,different bioaugmentation consortia obtained obvious differences in the degradation efficiency of different petroleum hydrocarbon components(light and heavy chains,aromatic components).Compared with the consortium of Bacillus sp.and Acremonium sp.,the consorthium of Bacillus sp.and Phanerochaete sp.was more effective on the heavy chain components.(3)Rhamnolipid at different concentrations had strong solubilization of the five PAHs.Solubility reflected by Sw*/Sw for the five PAHs has been enhanced by 10 or more times when the rhamnolipid concentration was 500 mg/L.(4)Rhamnolipid supplementation could significantly improve the total removal rate of mixed PAHs in soil treated with microorganism consortium(p<0.05).The maximum of total removal rate of anthracene and fluoranthene was acquired by sequential bioaugmentation treatment group with the fungal-bacterial consortium of Bacillus sp.and Acremonium sp.,reaching 81.54±2.04%?73.86±1.31%,respectively.(5)Acremonium sp.had the transmission capacity for hydrophobic organic compounds(HOCs)such as fluoranthene.As the extension of incubation time,the transfer rate of fluoranthene by Acremonium sp.increased gradually.After 14 days,the transfer efficiency of fluoranthene reached 8.29±1.01%.(6)The presence of heavy metals(HM)has been confirmed to affect the transfer and removal rate of fluoranthene by Acremonium sp.,and the effects varied depending on heavy metals species.Compared with the control,Mn2+?Fe2+ supplementation could significantly improve both the transfer and removal efficiency(p<0.01),and the fluoranthene removal efficiency increased by 12.85%,7.29%respectively.However,Cu2+ and Al3+ supplementation presented obvious inhibitory effect both on the transfer and removal efficiency.The fluoranthene removal efficiency decreased 14.05%?22.54%respectively compared with the control group. |
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