Corrosion or scaling tendency and trend for water resources in rural areas of Kashan, Iran

Scaling and corrosion both are destructive to materials (usually metals) in water supply systems. A dataset (from 2002 to 2013) of groundwater resources (including springs, qanats, deep wells and semi-deep wells) were examined for water tendency to corrosion or scaling in rural regions of Kashan, a city in Isfahan, central Iran. Water quality parameters including pH, temperature, Ca (mg/L), CO32- (mg/L), HCO3-(mg/L) and TDS (mg/L) were used to estimate water stability indices. Value of qualitative indices including Langelier (LSI), Ryznar (RSI), Puckorius (PSI) and trend of Calcium Carbonate Precipitation Potential (CCPP) as a quantitative index were calculated and analyzed for all water resources. Mean of LSI, RSI and PSI for all water resources were estimated to be 0.41±0.02, 6.39 ± 0.03, and 7.40±0.02, respectively. The CCPP value found to be 17.23±3.16, 15.66±1.38, 41.23±11.22, and 23.15±4.46 mg/L for springs, qanats, deep wells and semi-deep wells, respectively. The CCPP index was significantly increased from 2002 to 2013, with an average of 1.6 units per year. A significant scaling tendency was observed. This tendency in decreasing order was observed in deep wells, semi-deep wells, springs and qanats. The estimated CaCO3 scale weight per cubic meter of water was 21 g on average, which may be problematic for water distribution systems. Water withdrawal management and reduction in TDS of water resources, perhaps through decrease in agricultural drainage, can be effective to reduce the scaling tendency.