Simulation Experiments Study On Gas And Biomass Change In-situ Remediation Of Nitrate By Nano Emulsified Oil

In recent years,emulsified oil has achieved abundant research results in situ repair groundwater pollution.However,in the process of actual application,because of the residue retention of emulsified oil,microbial degradation and gas production of microbial degradation,it frequently cause clogging,which result in the decrease of repair efficiency or failure.In order to solve this problem,focusing on the gas effect in the process of nano emulsified oil enhance nitrate denitrification,batch experiments were carried out to analyse the nitrate degradation,gas composition,gas production,gas process and microbial changes.On this basis,the permeability loss of porous media was analyzed and assessed by one-dimensional concept column model in a hypothetical open and closed aquifer system.The main results are as follows:?1?Nitrate degradation results show that the degradation experiments have been completed for ten cycles in 150 days and the results indicated that 2 mL nano emulsified oil can enhance 50 mg/L nitrate degradation.The highest removal rate was99.5%and average reduction rate was 2.02 mg/d.Meanwhile,on the 150th days,nano emulsified oil still works,which reflects the longer effective longevity.Tween 80 and Span 80,as the main components of nano emulsified oil,can enhance effective nitrate degradation.The total removal rates for systems with Tween 80 and Span 80 were49.2%and 58.6%,respectively.?2?The CO₂ and N₂ were the main gases produced by nano emulsified oil anaerobic fermentation and nitrate denitrification,and average gas production rate in was 0.45 m L/d and 0.37 mL/d,the accumulated gas production was 172.17 m L and59.00 m L,respectively.In the reaction of the selected carbon sources,microbial proliferation showed a completed growth curve,and growth rate constant of the exponential phase were 0.25,0.11 and 0.06,respectively.The denitrification rate,nitrogen generation rate and microbial growth were consistent.?3?One-dimensional concept column model assessment results show that in an open aquifer system,which gas can be released in time,only 0¹%reduction came into being in permeability of medium and fine sand.However,in a closed aquifer system,which gas cannot be released in time,the accumulated gas can lead permeability loss to 100%in both medium and fine sand.Microbial growth caused same degree of permeability loss both in open and closed system,and the value were6.01%and 7.08%in medium and fine sand,respectively.?4?Contribution rate of gas production results show that in open system,the contribution rate of gas production and microbial proliferation to permeability loss in medium and fine sand is 0.5%and 6.5%,respectively,with a total of 7%.In contrast,the contribution rate in closed system is 94%and 6%,respectively,with a total of100%.It indicates the microbial growth is the main reason for permeability loss in open aquifer system,oppositely,gas accumulation is the main reason in closed aquifer system.Thus,changing the opening degree of aquifer system is expected to alleviate aquifer clogging.