Author(s): Juan Ernesto Ramirez Juarez; Maria Alejandra Alvarado Alvarado; Anuard Isaac Pacheco Guerrero; Alba Nelida Garcia Beltran; Angel Alfonso Villalobos De Alba

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Keywords: Potable water; Ca/Mg ratio; Ca precipitation; Pipe obstruction

Abstract: Obstructing pipes due to salts precipitation is one of the principal problems occurring in water supply systems. High levels concentrations of alkalinity and hardness encourage the precipitation of Ca and Mg salts. Intermittent water supply systems promote the precipitation of these salts due to the increase in the residence time of water in the distribution system. Precipitation rate can be modified by the Ca/Mg hardness concentrations ratio present in the water; this delays the precipitation of salts. The objective of this work was to determine the effect of the Ca/Mg concentrations ratio on Ca and Mg precipitation under drinking groundwater water sources conditions. Precipitation kinetics experiments were performed using synthetic water at different Ca/Mg concentrations ratios; those were performed at the same alkalinity and Ca concentrations obtained in real potable groundwater. The pH, electrical conductivity, alkalinity, Ca, and Mg hardness were measured. Both electrical conductivity and alkalinity reduction are related to Ca precipitation, whereas pH increases at the start of assays and is reduced during Ca precipitation. High Ca and Mg precipitation was obtained at higher Ca/Mg ratios than 5.5, while the precipitation of these ions was reduced at lower ones. The knowledge of the Ca/Mg concentration ratio contained in drinking water sources could predict the precipitation of salts in pipes.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221676

Year: 2022