Granular Activated Carbon Filtration as a Lead Control Strategy

Climate change-related increases in organic carbon in surface waters may present challenges in meeting regulatory requirements with regard to drinking water quality. Treatment adaptation that alters natural organic matter (NOM), metal oxides, and water chemistry can have a downstream influence on lead release. We compared the effect of the coagulant and filter type on water quality and lead release in a galvanic lead solder-copper system. Aluminum sulfate (alum), polyaluminum chloride (PACl), anthracite/sand, and granular activated carbon (GAC) were tested in a pilot-scale system. Lead release was evaluated in a bench-scale dump and fill experiment with treated water dosed with 0-2 ppm zinc-orthophosphate. GAC contactors reduced organic carbon in both systems and had a strong protective effect on lead release, likely due to less NOM complexation and improved orthophosphate performance. At equivalent Al doses, organic carbon removal was comparable between PACl and alum, but PACl showed slower GAC exhaustion rates, improving the removal efficiency. PACl was linked with increased galvanic corrosion due to higher CSMR. Zinc-orthophosphate mitigated galvanic corrosion of lead solder. Treatment facilities can decrease lead release by removing NOM, but alternative coagulants that may be considered for enhanced NOM removal can increase the chloride concentration and have detrimental effects as well.