Abstract
Groundwater pollution and human health risks caused by leachate leakage have become a worldwide environmental problem, and the harm and influence of bacteria in leachate have received increased attention. Setting the isolation distance between landfill sites and groundwater isolation targets is particularly important. Firstly, the intensity model of pollutant leakage source and solute transport model were established for the isolation of pathogenic Escherichia coli. Then, the migration, removal and reduction of bacteria in the aerated zone and ground were simulated. Finally, the isolation distance was calculated based on the acceptable water quality limits, and the influence of hydrogeological arameters was analyzed based on the parameter uncertainty. The results of this study suggest that the isolation distances vary widely ranging from 106 m–5.46 km in sand aquifers, 292 m–13.5 km in gravel aquifers and 2.4–58.7 km in coarse gravel aquifers. The gradient change of groundwater from 0.001 to 0.05 resulted in the isolation distance at the highest gradient position being 2–30 times greater than that at the lowest gradient position. There was a difference in the influence of the thickness of the vadose zone. For example, under the same conditions, with the increase of the thickness of the aeration zone, the isolation distance will be reduced by 1.5–5 times, or under the same thickness of the aeration zone, the isolation distance will be significantly shortened. Accordingly, this needs to be determined based on specific safety isolation requirements. In conclusion, this research has important guiding significance for the environmental safety assessment technology of municipal solid waste landfill.
Highlights
Groundwater pollution and human health risks caused by leachate leakage have become a worldwide environmental problem, and the harm and influence of bacteria in leachate have received increased attention
An appropriate isolation distance can ensure that the concentration of toxic and harmful substances after leakage will continue to decay under the interception effect of the vadose zone and the purification and dilution effect of the aquifer so that the water quality of the supply wells around the landfill site can meet the standard of safe water use[3]
The results showed that when the groundwater gradient increased from 0.001 to 0.05, the required isolation distance in sand, gravel and coarse gravel aquifers increased from 106 m to 5.46 km, 292 m to 13.5 km and 2.4 km to 58.7 km, respectively
Summary
Groundwater pollution and human health risks caused by leachate leakage have become a worldwide environmental problem, and the harm and influence of bacteria in leachate have received increased attention. An appropriate isolation distance can ensure that the concentration of toxic and harmful substances after leakage will continue to decay under the interception effect of the vadose zone and the purification and dilution effect of the aquifer so that the water quality of the supply wells around the landfill site can meet the standard of safe water use[3]. Significant correlations with giardiasis, the hepatitis virus, and parasitic diseases have been investigated[23], and some studies have found that bacteria can migrate kilometers in karst aquifers and km in chalk aquifers[24], while phages migrated 920 m in polluted coarse gravel aquifers and bacteria migrated 600 m in polluted gravel aquifers[25] These results show that groundwater pollution caused by bacteria in leachate is widespread, there have been relatively few studies of its influence. It is necessary to investigate for properly determining groundwater isolation distance for landfill sites with consideration of bacteria
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