Recovery of lead, iron, and copper from point-of-use-filters to examine performance

Abstract

Over the last few decades, reliance on point-of-use (POU) treatment for removing actual or perceived contaminants in drinking water has increased within the United States. Understanding POU treatment removal performance, and accurately estimating metals exposure at the tap, is critical for understanding POU water treatment device effectiveness and potential reductions in contaminant exposure. Previous bench-scale efforts have documented significant removal of dissolved Pb using faucet-mounted POU filters; however, limited efforts have challenged these filters with extreme water quality conditions which are more common in homes reliant on private well water. Characterization of typical rates of metals uptake by POU filters would support: improved exposure estimates and predictions, a better understanding of long-term filter performance under different conditions, and identification of conditions where POU use is recommended. In the current study, standard faucet-mount activated carbon POU filters were tested in a laboratory setting in order to: 1) determine removal of Pb, Cu, and Fe under low and high concentration conditions designed to reflect previous observations of residential water quality; and 2) evaluate the effectiveness of an acid flow-through procedure in recovering metals from used POU filters exposed to varying concentrations of Pb, Cu, and Fe. Although the filters tested here successfully removed Pb and Cu from waters of both high and low-level concentrations (>91% removal), Fe removal varied considerably. The acid flow-through procedure yielded mixed results: while 25.1-70.4% of influent Pb mass was recovered, recovery of Cu and Fe from the dosed filters was unpredictable. This was attributed in part to leaching from the filter media itself; in addition to Cu and Fe, concentrations of several other elements (e.g., Ti, Si, Al) increased and appeared to leach from control filters during the acid flow-through procedure. Given these results, alternative methods for assessing uptake of metals to POU filters should be explored.