Carbon source selection is a bottleneck problem in the process of groundwater nitrate in-situ remediation. This paper chose the emulsified soybean oil as the carbon source in the study. It studied the ratio of emulsified soybean oil, the impact of emulsified soybean oil injection on permeability of medium and through the indoor column simulated experiment in-situ remediation of emulsified soybean oil as carbon source in the process of removing the effect of nitrate, and evaluate the emulsified soybean oil denitrification effect. In the paper, the conclusions could provide a basis for the practical engineering. The main conclusions were as follows:The ratio experiment of emulsified soybean oil showed, the volume fraction of oil between 55% and 60%, at the same time the volume fraction of emulsifier between 13% and 15%, the stability of emulsified soybean oil was good. The grain size of the samples were micron grade, and the viscosity of the samples were similar to water. The properties of the samples were beneficial to the emulsified soybean oil injection and uniformly distributed in the aquifer sands. The COD cumulative released quantity of the samples were between 105-106 mg/L. The properties of emulsified soybean oil were able to meet the requirements as carbon source of denitrification reaction.The permeability of column simulated experiment showed, at the initial stage when the emulsified soybean oil injected into the column, the hydraulic conductivity of each column suddenly dropped, the hydraulic conductivity fell to about 20% of the initial value. With the increasing of the volume, the hydraulic conductivity of column gradually recovered to the 30% to 50% of the initial hydraulic conductivity, at the same time, the column effluent cumulative release quantity of COD had achieved more than 80% of COD emission of emulsified soybean oil. After adding emulsified soybean oil would have an effect on the permeability of medium, so it need pay attention to the change of hydraulic conductivity in the practical engineering.The simulated column experiment that used emulsified soybean oil to remove nitrate showed, in the experiment of 116 days, the nitrite nitrogen (NO3-N) concentrations of the inffluent were 20 mg/L and 50 mg/L.The lowest nitrite nitrogen (NO3-N) concentrations in the effluent could reach 0.32 mg/L and 0.45 mg/L. The highest nitrate nitrogen removal rate could reach 99%. The total removal efficiency were about 73% and 70%. The amounts of total removal of nitrate nitrogen were 437.2 mg and 1117.0 mg respectively. Emulsified soybean oil as the carbon source of in-situ nitrate remediation had an good effect on nitrate removal.The calculation results of emulsified oil evaluation showed that, the longevity of the emulsified vetetable oil that were injected could reach 116 days or so. The amount of unit volume emulsified soybean oil to remove nitrate nitrogen were 5.5 g/L and 14.0 g/L. In the denitrification reaction, the ratios of COD/N were 30.9 and 12.8. The utilization rates of COD were 35.13% and 35.13%. According to the calculation of COD/N ratio, the loss of carbon source in the experiment could remove nitrate nitrogen quality were 268.76 mg and 584.74 mg. The half-life of emulsified soybean oil removing nitrate could reach 13 and 24 days or so. |