Chemical-free arsenic removal from potable water with a ZVI-amended biofilter

With a reduction in the maximum allowable concentration (MAC) from 25mug/L to 10mug/L in Canada, arsenic in potable water is of growing concern. Many of the currently available arsenic removal technologies require considerable capital investment that is not feasible for small to medium-sized communities. These technologies also have associated operating costs and skill requirements that make them unsuitable for many small-scale utilities. As a result several small communities in Western Canada do not currently meet the new arsenic MAC and will require innovative potable water treatment solutions to do so.;Continuous column studies with nutrient-enhanced RO water showed no statistical difference in arsenic removal performance of various mixtures (v/v) of filtration sand and ZVI provided the mixture consisted of at least 300% ZVI filings. Column studies with Kannata Valley and Buena Vista raw water indicated that columns containing 50/50 and 40/60 ZVI/filtration sand (v/v) could effectively remove arsenic to well below 10mug/L. Arsenic removal efficiency of the ZVI/sand columns was greater than 95% and 88% for Buena Vista and Kannata Valley water, respectively, using both 50/50 and 40/60 media mixtures. Arsenic speciation tests of raw and treated water indicated that the ZVI filings were equally adept for removing As(III) and As(V). No significant amount of iron was leached from the ZVI/sand columns under the conditions tested.;This research project examined the use of a zero valent iron (ZVI)/sand column to remove arsenic from potable water. Batch studies were conducted using both arsenic-spiked reverse osmosis (RO) water and naturally arsenic-laden groundwater from two Saskatchewan communities (Kannata Valley and Buena Vista, Saskatchewan). The Langmuir isotherm best described the adsorption of arsenic onto ZVI for all samples. The maximum loading capacity (Langmuir constant qmax) was found to be 833,2000 and 5 000mg As/kg ZVI for arsenic-spiked RO, Buena Vista water and Kannata Valley water, respectively.