Transport And Transformation Of Nitrate Contaminants In Groundwater Modeling And Removal

In recent years, due to the irrational exploitation of groundwater and pollutant emissions, groundwater has been severely contaminated. Using of pesticides and fertilizers and discharging of sewage and industrial waste leading groundwater nitrate contaminant has become one of the most popular and biggest pollution area problem. Once the contaminants move into groundwater, then will migration and diffusion with groundwater flow with the result that continue to expand the scope of pollution. Therefore predicting the distribution in time and space of nitrate underground aquifers becomes more and more important.There chose Tsukuba catchment system as the research object, nitrate is the representative contaminant of inorganic pollutants. Carried out long-term monitoring for groundwater level and concentration of pollutants of this research area, and used Visual MODFLOW software to simulate groundwater flow and nitrate transportation and transformation. For nitrate contaminated of groundwater, Nano zero valent iron-nickel bimetallic nanoparticles (Fe-Ni) and supported nano zero valent iron-nickel bimetallic nanoparticles were synthesized by borohydride reduction method. Compared carbon microspheres supported Fe-Ni with ordinary activated carbon supported Fe-Ni. The following conclusions:(1)MODFLOW module and RT3D module are used to establish groundwater flow model and nitrate transport model. By comparing measured groundwater head and nitrate concentration with calculated values, we found that the established model fit better and had high sensitivity and accuracy. It can be used to simulate groundwater flow and trends of inorganic contaminant nitrate in groundwater effectively.(2)Use transient flow instead steady flow can reduce the impact of season, rainfall and other natural factors on nitrate concentration and the groundwater level dynamics. Therefore Visual MODFLOW model can be used to simulate the transportation and transformation of nitrate in the underground aquifer.(3)By SEM and XRD characterization techniques discovered, Fe-Ni agglomeration and chained, Fe-Ni supported by carbon can be well dispersed in the carbon surface. With Fe-Ni dosing concentration increasing, nitrate removal efficiency increased. When dosing concentration is higher than 1.0 g/L, continue to increase the dosing concentration have very small influence on nitrate removal efficiency. After reaction 180 min, Fe-Ni dosing concentration were 0.5,0j8,1.0,1.2,1.5 g/L, the nitrate removal efficiency were 54.52%, 76.93%,93.56%,95.47% and 96.35%, respectively.(4)It can be found from comparison of different nanomaterials on the removal of nitrate, carbon microspheres and ordinary activated carbon both have adsorption capacity to nitrate. Three types of nano materials on pollutant reduction capabilities:Fe-Ni/C> Fe-Ni/AC> Fe-Ni. This is due to supported nano zero valent iron-nickel bimetallic nanoparticles can catalytic reduced nitrate when adsorption, on the other hand, carbon microspheres prepared by hydrothermal and pyrolysis method has better dispersion than ordinary activated carbon, and are in the optimal size range for effective transport through groundwater.