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

Abstract

Due to increased consumption of drinking water in the world, there are attempts to apply new solutions for accessing sufficient amounts of water with proper quality. In addition, efficient usage of energy and finding a solution for reducing the scale-related problems in drinking water pipes are among major concerns of urban water supply. Annually, significant budgets are assigned for removing the scale of pipes as well as home and industrial devices. The present study endeavors to examine the scale-formation and corrosion potential of drinking water in drinking water distribution network of Shiraz City (south of Iran). This study is of descriptive type conducted through Langelier, Puckorius, Ryznar, Larson and aggressive indices and taking 144 samples of different sources and points of distribution network. The results showed that the mean values of LI, RI, LS and AI 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 of 33 home pipe samples and 8 network pipe samples were analyzed by X-ray diffraction method. Results indicated that 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.