Variation Characteristics Of Water Environmental Elements And Enhanced Bioremediation Of Slightly Petroleum Contaminated Groundwater

Petroleum is widely used for various applications with the development of social economy.But due to leakage in the process of mining,transportation,utilization,storage and processing,petroleum comes into and causes pollution of groundwater,threatening ecological environment and human health.Carrying out in situ remediation,especially in situ bioremediation to petroleum contaminated groundwater is considered to be the most economical and effective method.At present,researches are mainly focus on monitoring,evaluation and prediction of water environment physical and chemical indicators and effect of strengthen remediation by adding electron acceptors or electron donors to groundwater.However,researches on the relationship between total pollutants and water chemical factors,microorganisms and metabolic enzymes in pilot scale are rare,especially in micro pollution cases,in situ enhanced bioremediation by adding degradation microbest has not been reported.Supported by the National Natural Science Foundation project "Response mechanism of microbial systems in the process of in situ enhanced bioremadition of petroleum-contaminated shallow groundwater-casestudy of a petroleum-contaminated site in northeast China as a".Based on previous works,this paper carried out in situ monitoring and analysis of water environmental elements such as total petroleum hydrocarbon(TPH),acidity(pH)value,redox potential(Eh),electric conductivity(EC),dissolved oxygen(DO),Na+,K+,Cat+,Mgt+,Cl-,SO42-,NO3-,HCO3-,Fe3+,Fe2+,Mn4+,enzyme activities of catalase,peroxidase,catechol 1,2-dioxygenase,catechol 2,3-dioxygenase,deoxyribonucleic acid of slightly petroleum-contaminated groundwater.Then,microbes were added into thepetroleum-contaminated groundwater via single well and multi-wells to enhance bioremediation.The effect of enhanced bioremediation was monitored and analyzed,and the variation characteristics of water environmental elements are identified in purpose of providing scientific basis for controlling and remediation of petroleum-contaminated groundwater.According to the tests and analysis,conclusions are as follows:1?In the process of natural attenuation of slightly petroleum-contaminated groundwater,concentration of TPH decreased,and a few water environmental elements show regularity vibration characteristics:DO,Fe3? and SO42-contents decreased gradually,one of the microbial degradation product HCO3-content increased,enzyme activities of catalase,peroxidase,catechol 1,2-dioxygenaseand catechol 2,3-dioxygenase decreased gradually,as groundwater environmental indicator,Eh value decreased gradually.2?In the process of natural attenuation of petroleum hydrocarbons,according to the variation characteristics of water environmental elements,while HCO3-content increased and pH value reduced,groundwater environment grows deoxidized,while enzyme activities of catalase,peroxidase,catechol 1,2-dioxygenase,catechol 2,3-dioxygenase decreased gradually,indicating that microbial degradation occurred in the process of natural attenuationbut gradually diminished.Microbes use electron acceptors such as dissolved oeygen,Fe3+,SO42-to degrade total petroleum hydrocarbon to carbon dioxide and water.According to analysis results of microbial community diversity in the contaminated groundwater,there is existence of petroleum hydrocarbon degradation bacteria.3?On the basis of natural attenuation,expanded training of aboriginal petroleum hydrocarbon degrading bacateria(benzene,naphthalene,alkane)was carried out and added via single-well and multi-wells to enhance bioremediation of slightly petroleum-contaminated groundwater.The results showed that after enhanced remediation,concentration of total petroleum hydrocarbon was significantly reduced,and electron acceptors such as FeC+ and SV42-contents obviously decreased.HCO3_content increases near the injection wells and showed a downward trend far away from the wells.Enzyme activities of catalase and peroxidase increased,while catechol 1,2-dioxygenase and catechol 2,3-dioxygenase decreased.pH value decreased significantly and groundwater environment trends to be more deoxidized.4?Analyzing the characteristics of enhanced bioremediation of slightly petroleum contaminated groundwater,the results show that microbial uses electron acceptors such as Fe3+,SO42" degrade total petroleum hydrocarbon to carbon dioxide and water,resulting in great increasing of HCO3-content and obvious lower of pH value,while groundwater environment is deoxidizated.Enzyme activities of catalase and peroxidase increased,which shows that bioremediation increase gradually,especially near the injection wells,microbial degradation effect is obvious.