Iron stability on the inner wall of prepared polyethylene drinking pipe: Effects of multi-water quality factors

Iron is currently one of the main contaminants of drinking water. The inner walls of drinking pipes can cause iron to release in water chemistry, which alters the water quality, including its chloride, sulfate, bicarbonate, pH, and humic acid (HA) levels. Hence, the goal of this research was to improve our understanding of the multi-water quality factors affecting iron release in polyethylene pipes. An array of bench-scale experiments were conducted exposing model water with different concentrations of chloride, sulfate, bicarbonate, HA, and different pH levels to prepared polyethylene pipes following the response surface methodology. The single role of HA during iron release is also evaluated by changing its concentration. A comprehensive study revealed that regression models could be used to describe the relationship between the five water quality parameters and iron release. The coefficients of determination were 0.890 and 0.870 for the fitting equations of total and soluble iron concentrations in water, respectively. In the presence of HA, the concentration of iron in water increased more rapidly than that for the other four factors (chloride, sulfate, bicarbonate, and pH). In addition, the Visual MINTEQ results suggest that a lower HA concentration tended to increase the degree of saturation of iron solids. In turn, this limits iron release and considerably increases the iron concentration in water.