Water aggressiveness and the possibility of changing quality for human consumption

ABSTRACT

The physicochemical characteristic of groundwater is a function of the interactions with the soil/rock mineralogy during its infiltration and its length of permanence in the aquifers, in addition to anthropogenic influences resulting from the use and occupation of the soil. Thus, it is common to find waters with high levels of corrosive or fouling aggressiveness. The Langelier Saturation Index is one of the indicators to assess the degree of water aggressiveness. In this work, samples of copper tubes were exposed to raw and drinking water, in which sodium hypochlorite was used as a disinfectant. The water samples were classified as “moderately corrosive” (Langelier Saturation Index = -3.2). Copper tube samples were immersed in water for 1 month, 1 week and 1 day, keeping the exposure rate of the tube in water at 0.5205 cm³.cm⁻². After the exposure time, concentrations of 1.006 ± 0.025 mgCu.L⁻¹ to 1.614 ± 0.051 mgCu.L⁻¹ were identified in the samples with raw water and 1.073 ± 0.034 mgCu.L⁻¹ to 1.979 ± 0.222 mgCu.L⁻¹ in the samples with drinking water. The copper concentrations in the raw and drinking water samples showed statistical differences (p > 0.005). The corrosion rate of copper tubing ranged from 0.0225 cm.year⁻¹ to 0.0012 cm.year⁻¹ depending on the exposure time of the water samples. No statistical differences were identified in the corrosion rate when the samples were subjected to raw water and drinking water (p < 0.005). The results proved that aggressively corrosive waters can cause copper pipe corrosion, changing its quality.

Keywords:
Water supply; corrosion; drinking water; contamination