| Due to the widespread use of petroleum worldwide,petroleum hydrocarbon contamination in soil and groundwater has become more and more serious for decades.As a passive restoration technology relying on the natural mechanism of the site,natural attenuation has the advantages of economy,environmental protection and sustainability.However,the remediation cycle is long and the processing efficiency is low,and it is untoward to satisfy the needs of short remediation time and high efficiency.Therefore,this study mainly uses batch experiments,under laboratory conditions,through the biostimulation of nutrient sources and rhamnolipid biosurfactants,the bioenhancement of exogenous degrading functional flora and the different treatment methods of biostimulation-enhancement combination to strengthen the degradation ability of microorganisms.By means of gas chromatography,16 Sr RNA sequencing,principal component analysis and canonical correlation analysis,the degradation effects of petroleum hydrocarbon pollutants in groundwater were compared and analyzed.Lastly,the research and development of microbial enhanced functional preparations was carried out.1.The effects of nutrient sources and biostimulation of different concentrations of rhamnolipid on the enhancement of microorganisms and the degradation of petroleum hydrocarbons were studied,and the changes of environmental factors and bacterial community structures were compared.The results explained that: supplementing the P nutrient source adjusted the C/N/P ratio to 100:20:1,which could provide the optimum nutritional conditions for the microorganisms.The addition of rhamnolipids can augment the dissolution of petroleum hydrocarbons,accelerate the touch of petroleum hydrocarbons with microorganisms,and facilitate transmembrane transport through rhamnolipid-induced structural changes.Within the scope of this experimental design,when 3 g/L rhamnolipid and P nutrient source were added,the highest degradation rate of petroleum hydrocarbons in groundwater was 60.1%.Azospirillum and Magnetospirillum became the dominant genera in the biostimulation test.2.On the basis of the biostimulation research,the bioaugmentation research was further carried out by using 6 kinds of petroleum hydrocarbon degrading bacteria groups.Changes in environmental factors,changes in ion concentrations and changes in bacterial community structure were compared.The results explained that the degradation rate of petroleum hydrocarbons was60% by bioaugmentation of 6 kinds of petroleum hydrocarbon degrading bacteria,the C/N/P ratio was adjusted to 100:10:1 by adding nitrogen and phosphorus nutrient sources,and the biostimulation of rhamnolipid biosurfactant was effective on petroleum hydrocarbons.The degradation rate was 57%.In the biostimulation group,Clostridium sensu stricto and Bacteroides became the dominant genera.The genus Tistrella mobilis and the genus Pseudomonas were found in the bioaugmentation group,which proved that the exogenous flora could ensure life activities and play a role in degradation under the experimental conditions.3.On the basis of biostimulation and bioaugmentation research,biostimulation of 6 kinds of petroleum hydrocarbon degradation mixed flora +nutrient source,mixed flora + rhamnolipid,mixed flora + nutrient source +rhamnolipid-Strengthen joint research.Changes in environmental factors,changes in ion concentrations,changes in redox processes,changes in bacterial community structure and changes in bacterial diversity were analyzed.The results showed that within the scope of the experimental design,the biostimulation-enhanced combination group of mixed flora + nutrient source +rhamnolipid had the highest petroleum hydrocarbon degradation rate of 83%.The experimental group experienced nitrate reduction,iron and manganese reduction and sulfate reduction.The most important was sulfate reduction among them.In conclusion,the biostimulation-bioaugmentation combination formulation of mixed flora + nutrient source + rhamnolipid has the best promotion of the removal of petroleum hydrocarbons.Because the combined treatment group provided both NP nutrient source and rhamnolipid biosurfactant,which ensured suitable nutritional conditions for microorganisms,and emulsified petroleum hydrocarbons to promote degradation.The exogenous mixed bacteria group is also provided,which improves the biological metabolism ability of microorganisms to petroleum hydrocarbons. |
PDF Full Text Request