Evaluation of Changes in Scale Deposits in Groundwater-Supplied Drinking Water Distribution Systems During Demineralization with an Organic Acid: A Basis for In Situ Removal

Abstract

Mineral scale deposits in groundwater-supplied drinking water distribution systems reduce hydraulic efficiency and increase maintenance costs. This study evaluated the effectiveness of citric acid as a descaling agent for natural scale deposits collected from the Benito Juárez and La Joya drinking water distribution systems in Zacatecas, Mexico. The samples were treated with citric acid solutions at concentrations of 1, 2, and 3 M (moles per liter) and characterized before and after treatment using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and inductively coupled plasma optical emission spectrometry (ICP-OES). In addition, statistical analyses were performed using analysis of variance (ANOVA) and Tukey’s test. The scale deposits were composed mainly of calcium carbonate and exhibited differences in their initial mineralogical composition between the two systems. Treatment with citric acid promoted the progressive dissolution of carbonate phases, resulting in mineralogical, chemical, and morphological changes. The 3 M solution produced the highest degree of mineral dissolution, whereas the 1 M and 2 M treatments showed statistically similar behavior. The results demonstrate that scale deposit removal efficiency is influenced by the initial composition of the scale deposits, providing a scientific basis for optimizing remediation strategies in drinking water distribution systems.