Manganese Greensand for Removal of Arsenic in Drinking Water

Abstract

Abstract The present study was initiated to identify treatment techniques suitable for the removal of As from small community groundwater supplies below the current interim maximum acceptable (IMAC) concentration of 25 µg/L prescribed in the Guidelines for Canadian Drinking Water Quality. The effectiveness of manganese greensand filtration (MGSF), including the effect of Fe(II) in the influent, was studied in batch (intermittent) and column (continuous) modes. Batch studies based on the Freundlich adsorption isotherm model showed that the percent removal efficiency of arsenic by MGSF to the IMAC value was 60 for 24-h equilibration. Column studies gave an overall percent removal efficiency of 41. However, in the presence of Fe(II), especially at an Fe/As concentration ratio of 20, manganese greensand gave an overall efficiency of 83% and a throughput volume of 1,440 L. Results showed that at a Fe/As ratio of at least 20 and in the presence of Fe(II), manganese greensand is capable of removing As to below the IMAC value, under continuous mode of operation and when the influent As concentration is <200 µg/L.