Analysis of hydrochemical characteristics of domestic water in rural areas of Lanzhou City

The concentrations of major ions, salinity, total hardness, pH and electrical conductivity (EC) in domestic waters (cellar, well, spring, river, pool, tap waters) in rural areas of Lanzhou City were measured and compared with the background of Sanitary Standards for Drinking Water (GB5749—2006). Based on the results, domestic water salinity in rural areas of Lanzhou City was in the range of 0.14~2.72 g·L^-1, with an average of 0.76±0.63 g·L^-1. Significant differences were noted among the different domestic water types, with an order of decreasing salinity as follows: well water > spring water > pool water > tap water > river water > cellar water. Average total hardness of the waters was 397.06±307.13 mg·L^-1, with also a decreasing order as follows: well water > river water > tap water > spring water > cellar water > pool water. With the exception of pool water, all the water samples had higher hardness than the background standards for drinking water. Ion concentrations, except potassium, were significant different in the water types. Well water had the highest ion concentration. Some well water samples had extreme concentrations of NO₃^--N, sulphate and chloride, far in excess of the background standards. But the average for all samples was lower than the standard. Significant differences (at P<0.05) also existed in EC and pH among different water types. The following hydrochemical types were noted for different water types: HCO₃-Cl-Ca-Mg for well water, HCO₃-Cl-Ca for spring water, HCO₃-Cl-SO₄-Ca-Na for pool water, and HCO₃-Ca-Mg for cellar, river and tap waters.