Scale Formation and Corrosion of Drinking Water Pipes: A Case Study of Drinking Water Distribution System of Shiraz City

Due to increased consumption of drinking water in the world, there are attempts to apply new solutions foraccessing sufficient amounts of water with proper quality. In addition, efficient usage of energy and finding asolution for reducing the scale-related problems in drinking water pipes are among major concerns of urbanwater supply. Annually, significant budgets are assigned for removing the scale of pipes as well as home andindustrial devices. The present study endeavors to examine the scale-formation and corrosion potential ofdrinking water in drinking water distribution network of Shiraz City (south of Iran). This study is of descriptivetype conducted through Langelier, Puckorius, Ryznar, Larson and aggressive indices and taking 144 samples ofdifferent sources and points of distribution network. The results showed that the mean values of LI, RI, LS andAI were 0.07 (slightly scale forming), 7.1 (non-scale forming), 1.2 (corrosive) and 14 (non-corrosive),respectively. The mean of scale formation rate value in Shiraz drinking water pipes was 0.26 mm/y. Accordingly,zones located in east, southeast and south of Shiraz have more problems of scale formation. Scale composition of33 home pipe samples and 8 network pipe samples were analyzed by X-ray diffraction method. Results indicatedthat main compositions in scale samples were calcium carbonate, calcium sulfate, magnesium carbonate,magnesium sulfate, hematite, maghemite, magnetite, goethite, zinc oxide, gypsum, vivianite, dolomite,hydroxyapatite and troilite. Main elements in scale samples were magnesium, silicon, phosphorus, sulfur, zinc,copper and lead.