Investigation of detergent pollution in the Khako and Dare-Moradbaig Rivers of Hamedan Province using linear alkyl benzene sulfonate (LAS) measurement as a wastewater discharge marker

This study was conducted to investigate the concentration, ecological, and health risk assessment of linear alkylbenzene sulfonate (LAS(, as the most common anionic surfactant in detergent formulations, in the Khako and Dare-Moradbaig Rivers in Hamadan Province. 13 stations accordingly were selected for water sampling, and some water quality parameters were measured at the sampling site. The samples were then transferred to the laboratory, the LAS absorption was read by spectrophotometer (UV-VIS-NIR) at 650 nm, and the final LAS concentration was calculated using the calibration curve equation. The results showed the LAS concentration was in a range of 0.2-1.66 mg/L. The Pearson correlation test did not show a significant linear relationship between LAS and water quality factors. The results of the ecological risk assessment in 9 stations were high risk, medium risk in 2 stations, and low risk in the 2 other stations. The results of the health risk assessment of LAS also showed no risk at different age groups. The comparison of LAS concentration with standard surfactant discharge (in surface water, irrigation, and agricultural applications in Iran) showed that the mean concentration of LAS in terms of discharge into surface waters is less than the allowable limit. By contrast, in terms of use for agriculture and irrigation, the mean LAS concentration is higher than the allowable limit. Given the importance of these rivers in terms of drinking water and agriculture supply and the need to maintain the health of the environment and society, it is necessary to take effective measures to control the entry of untreated wastewater into the Khako and the Dare-Moradbaig Rivers.