FRESENIUS ENVIRONMENTAL BULLETIN, vol.27, no.2, pp.765-770, 2018 (SCI-Expanded)
Nitrate, phosphorus and heavy metals are among the most common pollutants and create potential dangers for groundwater contamination. In this research, a liner design was proposed for waste repository sites, constructed wetland basins and manure management lagoons to prevent groundwater contamination by seepages from the bottom of these facilities. For this purpose, sand-bentonite and pumice-bentonite mixtures with pre-defined grain size range (1.00-0.50 mm) and bentonite content (30%) was used. The mixtures were compacted at optimum moisture content and maximum dry weight and then permeability tests were carried out over compacted mixtures. Various concentrations of nitrate, phosphorus (25, 50, 100, 150 and 200 ppm) and heavy metal (Cd, Ni, Pb, Cr and Cu) solutions (10, 20, 30, 40 and 50 ppm) were used to saturate the permeability test samples. Extracts of permeability tests were used to investigate the adsorption characteristics of proposed mixtures for liner design. With regard to heavy metal adsorption, bentonite had the best performance because it is a clay mineral. Sand and pumice exhibited similar performances in lead and cadmium adsorption, but pumice had much better performance than sand in chrome, copper and nickel adsorption. Although sand-bentonite and pumice-bentonite mixtures exhibited similar performance in nitrate adsorption, again pumice-bentonite mixtures had much better performance than sand-bentonite mixtures in phosphorus adsorption. Current results revealed that pumice with macro-micro pore structure and resultant adsorptive surface characteristics could be used as an alternative of sand in liner design.