Early detection of chloroform hot spots in the Montevideo drinking water network

Abstract

The use of chlorine to disinfect water produces a series of by-products, particularly trihalomethanes. This is important given that there is a recognized association with different types of cancer after prolonged exposure, as well as with probable adverse effects on reproduction, especially in relation to offspring. The concentrations of these organic compounds vary greatly depending on the season and the conditions involved in providing water for consumption. This study was aimed at determining the geographic distribution pattern of chloroform in the city of Montevideo, and correlating that with the characteristics of the water distribution network. A total of 400 samples were taken from a sampling network between 2009 and 2015. Chloroform was identified by analyzing these samples using the headspace gas chromatography/mass spectrometry method. Data regarding piping length, diameter, and type of material were obtained. A geographic information system was constructed and hot spots were analyzed using the Getis–Ord Gi* statistic. A neighborhood piping density index was also proposed. The analysis found two zones in the city: hot and cold spots. The proposed index showed an increase in the Gi* statistic as the neighborhoods’ piping density increased, with a strong correlation. In addition, the highest Gi* statistic values corresponded to larger amounts of iron piping in neighborhoods. This work was able to determine that the hot spots were associated with the piping density in the neighborhoods as well as with the type of piping material, particularly iron.