ABSTRACT
Iron coagulation/flocculation for arsenic (As) removal was evaluated in a double filtration system based in the CIS-UNR® process. Two pilot systems, each one consisting in an up-flow gravel filter (UGF) followed by a rapid sand filter (RSF) were evaluated in two wells with As polluted water. One well water presented variable As (10 to 40 µg As/L) and iron (1.2 ± 1.0 mg Fe/L) concentration, the latter worked as coagulant. The other one presented around 46 ± 5 µgAs/L and 0.1 mgFe/L, therefore iron was dosed (4 ± 2 mg Fe/L,11.6 ± 5.8 mg FeCl3/L). In the first case 20 to 40% removal was reached by the UGF and further removal (42–83%) after the RSF. The second case showed (76 ± 15%) removal after the UGF and up to 82 ± 16% in the rapid filter water. Both reached less than 10 µg As/L. The CIS-UNR® process, originally designed for working with polyaluminum chloride (PACl), performed well at low iron coagulant concentration and the need of the RSF as a polishing step was demonstrated.
