AWWA JAW56923

Orthophosphate and polyphosphates are widely used by drinking water utilities to reduce lead, copper, and iron (Fe) release from distribution system materials and reduce visible Fe precipitation and related discolored water complaints. Bench-scale experiments were conducted to evaluate the effect of orthophosphate and several polyphosphates on the properties of Fe particles and suspensions derived from the oxygenation of Fe(II) at a single oxygen concentration over a broad pH range. Results showed that polyphosphates and orthophosphate, to a lesser extent, reduced apparent color and turbidity of Fe suspensions, decreased particle size, made the zeta potential more negative, and increased Fe suspension stability. A fixed-mass concentration of low-molecular-weight polyphosphate was more effective at reducing the particle size of Fe(III) solids than high-molecular-weight polyphosphates. Includes 53 references, tables, figures.