Arsenic Removal from Water by Moving Bed Active Filtration

Abstract

Arsenic (As) in drinking water was removed by a combined co-precipitation, active filtration process. A serpentine prereactor for ferric chloride (FeCl3) reagent mixing was combined with a moving bed active filter, followed by separation of waste residuals from clean water discharge. Waste effluent, using 10% of influent for transport, was retained in a clarifier for settling prior to water recycling. Process residuals passed leach tests for landfill disposal. The pilot-scale apparatus was tested at a small community, public drinking water system in Fruitland, Id. In a 49hour test, influent groundwater averaging 40.2±1.0μg∕L total As (n=17) was fed at 38L∕min(10gpm) and FeCl3 solution was added at an optimized Fe to As molar ratio of 133:1. Arsenic concentrations were reduced to 3.3±1.4μg∕L(n=49) over the test period. Research observations support the hypothesis that the formation and renewal of iron oxide-coated sand in the active filter is a viable mechanism for high efficiency As removal. Further testing is underway to optimize long-term operating performance and to characterize the chemical processes of the system.