Coupled electrocoagulation and oxidative media filtration for the removal of manganese and arsenic from a raw ground water supply

Abstract

The application of electrocoagulation (EC) as a standalone technology, as well as coupled with oxidative media filtration was investigated for the removal of arsenic and manganese from a community’s groundwater supply. The effects of metal loading (ML), current density and flocculation time was investigated, in addition to the subsequent use of GreensandPlus™filtration. Effective removal of arsenic was yielded to levels well below World Health Organization limits, with final concentrations below 3 μg L−1, from an initial concentration of 9.77 μg L−1. The optimal ML, or coagulant dose, was observed to be 10 mg L−1, with very little removal at MLs below 2 mg L−1. EC was not as effective for manganese removal, with only 10% reductions at an ML of 10 mg L−1. Further manganese reductions were yielded during flocculation, yielding a final total manganese concentration of 98.97 μg L−1, below both the WHO and Health Canada maximum allowable concentration for drinking water. When coupled with oxidative media filtration, arsenic was nearly completely removed, with final concentrations below 0.1 μg L−1. While the mechanism of arsenic removal was primarily associated with the iron coagulant floc formation, manganese removal was attributed to the catalyzed oxidation reduction reaction with the manganese dioxide media. Comparative studies using conventional coagulant resulted in arsenic concentration to decrease to 4.4 μg L−1, over an order of magnitude greater than those achieved with EC.