Investigation of the formation and effects of upstream trihalomethanes in Tehran's raw and drinking water using the spectrophotometric method

Abstract

Developing countries, such as Iran, lack the resources and infrastructure to effectively and continually monitor environmental variables related to safe drinking water. The concentration of trihalomethanes (THMs) in Tehran's drinking water was assessed using spectrophotometry as an alternative method rather than the commonly used GC–MS. This method proposes a more economical and available option for developing countries and local water treatment plants in small towns. Three surface water sites, i.e., the Karaj River, the Mamaloo River, the Jajrood River, and eighteen tap water sites, were logistically chosen to test this method. This study evaluates the effect of seasonal variables on trihalomethanes formation potential (THMFP) and its impact on drinking water THMs concentrations. According to the statistical analyses during summer, THMFP and temperature positively correlated with the correlation coefficient of 0.84 and P < 0.05. Also, a positive linear correlation was observed between THMFP and UV254 with a correlation coefficient of 0.73 and P < 0.05. THMFP started to decline during fall as the temperature decreased except in November when THMFP increased due to natural organic matters (NOMs) augmentation in rivers. The highest level of the monthly average concentration of THMs in drinking water was 33.9 ± 5.8 μg/L in September, and the lowest was 22.9 ± 4.2 μg/L in December. The results indicated a linear correlation between THMFP in surface water and THMs concentration in drinking water with a correlation coefficient of 0.81 and P < 0.05. This observation suggests that THMFP in surface water can directly affect THMs' levels in drinking water.