Soil aquifer treatment (SAT) is a nature-inspired solution for improving the water quality\nthrough soil percolation. The biodegradation of organic matter typically occurs in the shallowest\nsoil layer and it depends on the contaminantâ??s characteristics (water solubility, molecular structure)\nand specific soil properties (pore size distribution). The present study aims at identifying which\ngrain size fraction of typically used sandy soils in the shallowest layer of SAT systems can provide\nthe optimal conditions for microbiological growth that can be reached by a trade-off between soil\nmoisture as well as nutrients and oxygen supply. For this, soil columns were used at a laboratory\nscale to determine the relationship between the pore size distribution of four different grain size\nfractions and biodegradation rates of organic matter from synthetic wastewater. The results obtained\nfrom this experimental setup indicate that bacterial colonies reached optimum growth when about\n60% of the available pore space was filled with water. For the selected soil, this was achieved by the\nfraction with grain sizes in the range of 630 micron to 1000 micron, having pore diameters between 87 micron\nand 320 micron and a mean pore diameter of 230 micron.
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