The effect of chloride and orthophosphate on the release of iron from a cast iron pipe section

“Colored water” resulting from suspended iron particles is a common drinking water consumer complaint which is largely impacted by water chemistry. A bench scale study, performed on a 90-year-old corroded cast-iron pipe section removed from a drinking water distribution system, was used to evaluate the effects of orthophosphate and chloride on iron release, color and turbidity. Experiments showed that an increase in chloride concentration of 100 mg/L significantly increased the concentration of iron released from the pipe section while the presence of orthophosphate at 3 mg/L decreased iron release. Chloride increased and orthophosphate decreased the water color and turbidity caused by the release of iron, but there was not a linear relationship with respect to the concentration of iron released. The control of chloride and orthophosphate concentrations is important in controlling the problem of colored water.