DRINKING WATER TREATMENT ADAPTATION FOR LEAD CORROSION CONTROL UNDER CLIMATE-DRIVEN WATER QUALITY CHANGE

Abstract

Lead in drinking water remains a public health concern worth mitigating. Drinking water treatment and distributed water chemistry are key determinants of lead release. Gradual and acute climate-driven changes in source water quality, treatment technology and regulatory targets create new challenges for corrosion control related to natural organic matter, coagulant selection, inorganic compounds, and excess product in wastewater. The goal of this work was to investigate how drinking water treatment adaptation influences lead corrosion control with an emphasis on organic matter and treatment strategies for enhanced removal, orthophosphate-based corrosion inhibitors, trade-offs with sequestration, and the feasibility of zinc-reduction. Pilot- and bench-scale studies in combination with time-series modelling and screening-level exposure projections were used to evaluate lead response to environmental events and experimental treatments. Following an extreme precipitation event, natural organic matter increased in source water and was associated with a prolonged elevation in total lead in a model distribution system and projected increases to short-term exposure risk. Enhanced organic matter removal via granular activated carbon improved lead control in a bench-scale reactor of galvanic lead solder. Equivalent total organic carbon removal was achieved at lower product doses of a chloride-based (polyaluminum chloride) coagulant relative to sulfate- based (alum), but was linked with increased galvanic lead corrosion. Orthophosphate- silicate may be an alternative to blended phosphate for systems needing to manage discolouration due to high iron/manganese, though risks of increased dissolved lead must be considered. In low-alkalinity water, reducing zinc in orthophosphate inhibitors may be feasible without compromising lead or cement corrosion, but may result in small increases in copper. These reductions could offer a more sustainable option with lower burden for wastewater treatment. This work demonstrated shifts in source water quality and treatment processes like coagulation, filtration, corrosion inhibitors and sequestrants can be protective or destabilizing for lead control and infrastructure maintenance. Utilities should consider whole-system trade-offs in lead control, treatment performance, and downstream sustainability during process adaptation or redesign.