Reactive transport modeling of subsurface arsenic removal systems in rural Bangladesh

摘要: Subsurface Arsenic Removal (SAR) is a technique for in-situ removal of arsenic from groundwater. Extracted groundwater aerated and re-injected into an anoxic aquifer, where the oxygen in injected water reacts with ferrous iron aquifer to form hydrous ferric oxide (HFO). Subsequent extraction contains temporarily lower As concentrations, because sorbs onto HFO. Injection, storage, together called cycle. A reactive transport model (RTM) was developed PHREEQC determine hydrogeochemical processes responsible (im)mobilization during experimental SAR operation performed Bangladesh. Oxidation Fe(II) As(III) were modeled using kinetic-rate expressions. Cation exchange, precipitation HFO, surface complexation, as equilibrium processes. best set complexation reactions corresponding constants adopted previous studies simulate all 20 cycles experiment. The gives reasonable match observed concentrations different elements extracted (e.g., r(2) value 0.59 or higher). are governed by four major First, concentration decreases response elevated pH injection likewise increases when native neutral flows in. Second, sorption capacity due gradual buildup Third, enhanced preferential As(V). Fourth, competitive Si limits freshly precipitated HFO sorption. Transferability demonstrated through successful application model, without further calibration, two additional sites This confidence that could be useful assess potential performance at locations Bangladesh based on local conditions.