Two-Year Operation of an Air-Iron Treatment System for the Removal of Arsenic from Simulated Bangladeshi Tubewell Water

摘要

A model system for As(Ⅲ) removal from simulated Bangladeshi tubewell water (in mg/L: As(Ⅲ) 0.2, Fe(Ⅱ) 5, Ca~(2+) 40, Na~+ 50, SO_4~(2-) 9, Cl~- 70, HCO_3~- 133, PO_4~(3-) 6, SiO_3~(2-) 20) was operated indoors for a period of 2 years at the rate of 8 L per day. The system comprised: 1. water storage tank with tap regulator, 2. tank with internal baffles which forced water repeatedly down through crushed brick and up to the surface, 3. tank containing scrap iron (fire-burnt tin-plated steel cans), 4. water lock to maintain water level, and 5. storage tank. In tank 2, particles of Fe(OH)_3.nH_2O (Ⅰ) were retained in the crushed brick, while As was partially precipitated with I and partially oxidized to As (Ⅴ). Arsenic removal in tank 2 varied from 95% to 30% (in the presence of PO_4~(3-) & SiO_3~(2-)).The arsenic concentration in the output water was < 5 μg/L for two years. The design of a pilot system for safe agricultural water is presented.