This study investigated the removal of arsenic in twenty wetland columns, planted with Phragmites australis, from a synthetic acidic wastewater that simulated water in a highly polluted river in northern Chile, the Azufre River. The efficiencies of four wetland media, cocopeat, zeolite, limestone, and river gravel, were investigated. A range of environmental factors, including pH, Eh, temperature artd SO4 level, were monitored alongside the removal rates of arsenic and iron, in order to explain the factors that must be taken into account when applying the wetland system to treat acidic wastewaters. Experimental data demonstrated that the primary route of arsenic removal is via coprecipitation with iron at increased pH level. The chemical equilibrium of arsenic-iron coprecipitation has been analysed. Also discussed are the effects of wetland media on arsenic mass removal rates, and the potential routes of arsenic removal in constructed wetland systems under oxidising condition.
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