Customer complaints of red water problems remain to be a frequent occurrence for water utilities. While material sources may vary, it is generally accepted that iron rust resulting from corrosion of iron based pipes is the predominant cause of red water issues. Recent efforts have lead to the development of a number of models that predict the occurrence of iron release and subsequent red water formation. This paper provides a detailed analysis of recently developed iron corrosion release models. Significant disagreement exists as to the processes and mechanisms leading to the release of iron corrosion materials into the water supply. This lack of consensus is made evident when comparing each of the iron release models. Considerable variation exists as to mechanisms considered and specific modeling goals. While each model may be beneficial for simulating certain aspects of corrosion release, no single model has been developed that provides a comprehensive portrayal of iron corrosion release phenomena. / Master of Science

The net present replacement value of all publicly and privately owned potable water pipes in the U.S. is on the order of $2.4 trillion dollars, and costs associated with deteriorating iron pipes is billions of dollars per year. Problems arising from iron corrosion include reduced lifetime of the material, scale buildup and energy loss, nonuniform corrosion and leaks, catastrophic failure, "red water," disinfectant loss and bacterial re-growth. Iron corrosion is a very complicated process and is affected by many factors. This research focused on the effect of disinfectant type, sulfate/chloride ratios, nitrate concentration, and magnesium hardness on iron corrosion. For the waters tested, chlorine better controlled red water and microbial activity in the bulk solution than chloramine. Changes in the sulfate/chloride ratio did not have a large effect on iron corrosion. High levels of nitrate increased the rate of chlorine decay as a result of free ammonia formation, and also increased the release of iron. Increased magnesium and zinc decreased the red water caused by high silicate. Microbiological activity is important in iron corrosion, and control of re-growth in water distribution systems is a major challenge for water utilities. A separate study examined the inter-relationship between iron corrosion and bacterial re-growth, with a special focus on the potential of iron pipe to serve as a source of phosphorus. Under some circumstances corroding iron and steel may serve as a source for all macronutrients necessary for bacterial re-growth including fixed carbon, fixed nitrogen and phosphorus. Conceptual models and experimental data illustrate that levels of phosphorus released from corroding iron are significant relative to that necessary to sustain high levels of biofilm bacteria. Consequently, it may be more difficult to limit re-growth on iron surfaces by limiting phosphorus in the bulk water. / Master of Science