Determination of Terihalamethanes(THMS) and Haloaseticacides(HAAS) concentration in drinking water supply Network of Urmia city in a over around year

Abstract

Introduction: Today, surface water as a source of drinking water is exposed to various pollutants. On the other hand, increasing world population and increasing water consumption, and shortage of drinking water due to pollution of sources, have made drinking water supply one of the main concerns Become universal. In providing safe drinking water, the disinfection process is one of the most common and important water purification processes, which is performed to eliminate microorganisms. However, one of the main concerns is the reactivity of chlorine with organic and inorganic substances, followed by the formation of disinfection by-products. Therefore, this study was conducted to determine the concentration of trihalomethanes and Halostatic acids in the water supply system of Urmia over a period of one year Materials and Methods: Surface and groundwater sources are used in the water supply of Urmia and this study is a descriptive cross-sectional study. Sampling from eighteen areas of the distribution network during the four seasons of the year to 72 samples (18 samples in each season) from different areas was performed by the method recommended in the standard method book. Temperature, residual chlorine, and pH parameters were measured at the sampling site and the samples were transferred to the laboratory while maintaining a cold chain. After preparing the samples, the concentrations of Trihalomethanes and Halostatic acids were measured using a gas chromatographic device equipped with an ECD detector. Also, total organic carbon (TOC) was measured for water samples in the laboratory. Data analysis was done using Kolmogorov Smirnov, ANOVA and Kruskalvalis tests, and to investigate the relationship between different parameters (residual chlorine, pH and temperature) with THM and HAA compounds, a linear regression test was performed considering the effect of season. Carcinogenic and non-carcinogenic risk assessment was calculated using chronic daily intake (CDI). Results: According to the results the mean concentration of Trihalomethanes compounds in winter, spring, summer, and autumn are 8.95, 10.54, 57.64, and 19.23, respectively, and for Haloacetic acids are 7.5, 27.35, 140.23 and 48.57μg/ml were measured. Therefore, the highest and lowest levels of Trihalomethanes and Haloacetic acids were related to summer and winter. Among the five studied areas, the highest amount of Trihalomethanes and Haloacetic acids were related to the areas where water resources were supplied from surface water ( Shahrchai Dam). The results of statistical analysis showed that there was a significant difference between the average concentration of THMs and HAAs in different seasons (p<0.05) and no significant difference was observed in different regions. Using linear regression test, the relationship between pH parameters and residual chlorine was investigated, and pH and season parameters were significant at the level of 0.05 and residual chlorine at the level of 0.1. The mean annual carcinogenic risk of these compounds for men and women was 1.089×10-5 and 1.149×10-5.The value of this index during life by exposure to THMs and HAAs in summer was higher than in other seasons. However, in all four seasons, the value of this index was in the tolerable range(10-4-10-6). Also, the estimation of cancer risk in five regions of Urmia was examined separately, among the five regions, region one has the highest carcinogenic risk (5.044×10-5 for men and 5.32×10-5 for women) and region two has the lowest carcinogenic risk (1.98×10-5 for men and 2.098×10-5 for women). The level of carcinogenic risk in the five regions was within the USEPA standard range (10-4-10-6). The total risk posed by exposure to these compounds in drinking water was higher for women than men. In the study of non-carcinogenic risk, the sum of these two compounds was less than (1) for both women and men and did not pose a threat to consumers' health. It is suggested that in future studies, the amounts of other emerging compounds due to chlorination in the drinking water system of Urmia and the risk caused by them be investigated. Conclusion: According to the results of this study, it can be said that the average annual concentration of trihalomethane and haloacetic acid compounds was less than the recommended national and international standards Based on the results of the linear regression test, residual chlorine parameters and pH were among the influencing variables in the formation of THMS and HAAS. In the study of carcinogenic risk in five regions and in different seasons, the value of this index was more than the USEPA standard in region one (10-4-10-4) and in other regions and in four seasons in the tolerable range. It is suggested that in future studies, the amounts of other emerging compounds caused by chlorination in the drinking water system of Urmia and the risks arising from them be investigated.