Iron corrosion as a factor contributing to haloacetic acids formation in the distribution system: experimental assessment and model development

In this paper, the results of an experimental investigation into four potential explanatory factors (i.e. Fe(II) ions, pH, phosphate and reaction time) with different levels, and their influence in the formation of haloacetic acids (HAAs) in water samples are presented. This study revealed that Fe(II) ions (p = 0.0001), phosphate based corrosion inhibitor (p = 0.01) and pH (p = 0.003) were the main significant factors for HAAs formation. A change in Fe(II) ions concentration from 0 to 3 mg/L, and PO₄ dosage from 0 to 1.5 mg/L, decreased HAAs formation by more than 50 and 14% respectively. In contrast, HAAs formation was observed to increase 7.92% with the increase in pH values from 6.5 to 8.5 in the same reaction systems. Considering all of the significant factors, a predictive model for HAAs formation was developed using 40 experiments. The adequacy of the developed model was checked statistically using numerical and graphical diagnostics. The model was found to be statistically significant, and the lack of fit test was found to be insignificant. An independent data set, obtained from HAAs formation study using the natural water samples collected from three main water treatment plants in Nova Scotia, Canada, was used to validate the model.