Physical, chemical and biological quality assessment of aqueduct (Qanat) water for drinking, agriculture and irrigation of urban green spaces

BACKGROUND AND OBJECTIVES: The aqueduct is one of the most complex and amazing inventions of human history, created to meet the most vital needs of human society in arid and semiarid regions areas. If aqueducts are properly maintained, reconstructed, and restored, they can be valuable water supply system from ground water resources. The quality of the water in these sources will have a direct impact on the consumer of its consumption, so it seems necessary to check the water quality of these sources.METHODS: This study investigated the state of five aqueducts in Tehran using parameters such as calcium, magnesium, phosphate, sulfate, turbidity, total hardness, nitrate, alkalinity, electrical conductivity, Biochemical Oxygen Demand, Chemical Oxygen Demand, total coliform and fecal coliform. Then the obtained values were compared with the permissible limits of the World Health Organization and the national standard of Iran. The data was analyzed using SPSS26 software and a one-sample t-test.FINDINGS: The results of water quality during a one-year survey period showed that the parameters of alkalinity, electrical conductivity, total dissolved solids, sulfate, and nitrate were below the maximum desirable and permissible standards of the national standard of Iran and the World Health Organization, and therefore will not create any restrictions for drinking and agricultural use. Total hardness, phosphate, turbidity, calcium, magnesium, and chlorine have discrepancies with the national standards of Iran and the World Health Organization and these components must be adjusted for use. According to the one-sample t-test, there was a significant difference between the average and the permissible values of all parameters except magnesium at the 95% confidence level. All aqueducts except the America aqueduct had levels of fecal coliform that were higher than the maximum allowed by the environmental standards therefore, before using the aqueduct, it must be purified to control the environmental standards.. However, the total coliform, Biochemical Oxygen Demand, Chemical Oxygen Demand levels were not a problem. In addition, the water quality of these sources was placed in a group (C3S1) based on the Wilcox diagram.CONCLUSION: The physical and chemical analysis of the studied aqueduct water showed that the water quality is suitable for the irrigation of green spaces and salt-resistant plants. The biological characteristics of the studied aqueduct water also revealed that these sources were polluted by domestic and industrial effluents. This issue will only grow worse with time, as the amount of rainwater decreases and the amount of pollution in the underground water sources increases