The Relationship Between Iron Oxides/Oxyhydroxides and Toxic Metal Ions in Drinking Water Distribution Systems A Review

Iron (Fe) oxides/oxyhydroxides in drinking water distribution systems (DWDS), produced by electrochemical, chemical, and biological reactions, can adsorb toxic metal ions, including strontium, lead, arsenic, and vanadium that, if desorbed, generate pulses of drinking water with elevated toxic metal ion concentrations. To illustrate that potential, sorption data for strontium ( cation) and vanadium (oxyanion) in functioning DWDS are reviewed. In addition, the influence of flow/no flow on adsorption and desorption of strontium in a model DWDS is included. The reactions that influence adsorption and desorption within a DWDS are extremely complicated and poorly understood. The sorption capacity of Fe oxhydroxides varies with surface area, which in turn varies with source water and disinfectant. Desorption and release can be triggered by changes in source water, disinfection chemicals, or flow. Because of the interrelatedness of adsorption/desorption and Fe corrosion products, subtle changes in DWDS operating procedures can trigger major changes in water quality.