Analysis of fluorides and chlorides in the drinking water distribution system of the city of Latacunga
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The present study evaluated the concentrations of free residual chlorine and fluoride in the drinking water distribution system of the Latacunga canton, Cotopaxi province, Ecuador, in order to verify compliance with the Ecuadorian Technical Standard NTE INEN 1108:2011 and the guidelines of the World Health Organization (WHO, 2017). Thirteen georeferenced sampling points were selected, covering the stages of intake, treatment, storage, and distribution. The samples were analyzed using spectrophotometry and colorimetric methods, ensuring accuracy and reproducibility in accordance with NTE INEN 2169:2013. The results showed residual chlorine concentrations between 0.074 and 0.891 mg/L (average 0.33 mg/L) and fluoride concentrations between 0.001 and 0.003 mg/L (average 0.002 mg/L). Although both parameters comply with regulatory values, a spatial variability of residual chlorine was observed, associated with manual dosing, transit time, and mixing conditions in tanks. Fluoride concentrations were uniform but below the recommended preventive range (≈0.7 mg/L), which limits their protective effect against dental caries. The system shows acceptable efficiency, although it requires automation of chlorine dosing, continuous monitoring, and hydraulic sectorization to stabilize the disinfectant residual. Based on the results, it is recommended to rehabilitate the distribution system and provide operational training to the operators to ensure a safe, stable supply in accordance with national and international drinking water standards.
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