Development of a novel iron release flux model for distribution systems

Although red water is a primary focus for consumer complaints about water quality, none of the models currently available adequately address iron release in drinking water distribution systems. This lack is understandable, given the complex nature of iron sources, iron release mechanisms, often-conflicting influences of various physicochemical and biological factors, pipe material and age, and the cocktails of corrosion products released. This work describes a mathematical and pilot-scale empirical development of a zero-order flux model. Iron concentration was found to depend on surface-release flux (Km), pipe material, pipe geometry, and hydraulic retention time. Flux is a function of pipe material, water chemistry, and Reynolds number (Re). For the specific water quality used in this study, the galvanized-iron K-m (mg Fe/m(2)/d) values were 1.99 and 0.0045/(Re - 2,000) + 1.99 under laminar and turbulent flow conditions, respectively. Similarly, K-m was found to be 4.16 and 0.009/(Re - 2,000) + 4.16 for unlined cast-iron pipe under laminar and turbulent flow conditions, respectively