3rd ASM International Congress of Agriculture and Environment, Antalya, Turkey, 16 - 18 November 2017, pp.42-43
Constructed wetlands, also called as natural wastewater treatment systems, are constructed for treatment of domestic, industrial and agricultural wastewaters in specially design basins filled with graded substrate material and planted with aquatic plants. Either natural compacted materials or synthetic liners are used prevent seepage from the bottom of constructed wetland basins. In this study, liner design was proposed for constructed wetland basins to prevent groundwater contamination through seepages from the bottom of these facilities. Sand-bentonite and pumice-bentonite mixtures with pre-defined grain size range (1.00-0.50 mm) and bentonite content (30%) was used in experiments. Different 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 compacted mixture samples. Permeability extracts were tested for adsorption and desorption characteristics of proposed mixtures for liner design. With regard to heavy metal adsorption, bentonite had the best performance. 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 adsorption surface characteristics could be used as an alternative of sand in liner design.