AWWA ACE54429

Two surveys of US drinking water utilities were conducted to clarify trends in phosphate inhibitor use. Survey results indicated that drinking water utilities add phosphate inhibitors for a variety of reasons including: control of iron, lead, and copper corrosion; and, prevention of calcite precipitation. Types of inhibitors used include polyphosphate, orthophosphate, zinc orthophosphate, and phosphate blends with dosage ranges from less than 0.2 mg/L to more than 3 mg/L as phosphate, with most utilities dosing between 1 to 2 mg/L as phosphate. Surprisingly, most utilities only considered limited information when selecting an inhibitor, and often did so without any direct confirmation that the inhibitor would be effective. Includes 5 references, figures.