Physico-chemical Characteristics of Corrosion Scales from Different Pipes in Drinking Water Distribution Systems

Abstract

Corrosion scales formed on iron pipe surfaces are an important factor defining water quality in drinking water distribution systems, since they would release contaminants and cause water discoloration at transient hydrodynamic regimes. Consequently, characterization of corrosion scales is indispensable to water quality protection. In this study, corrosion products were carefully collected from three old, corroded iron pipes made of different materials and exposed to different water qualities and operation conditions. Physico-chemical characteristics of these scales were determined using Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Inductively Coupled Plasma (ICP), X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). Testing results show that scale characteristics, including micromorphology, porosity and composition, vary significantly due to different pipe materials, water qualities and hydraulic conditions. Zinc coatings in galvanized pipes contribute to metal corrosion prevention, while attention should be paid to zinc release. High corrosive surface water facilitates the formation of developed corrosion tubercles, in which the compact shell-like layer conduces to maintain the structural stability of corrosion scales under disturbance. Structural breaks and low-velocity zones in water distribution systems might be in high potential of contaminant release, since the inhomogeneous materials and unusual hydraulic conditions would result in unstable scale characteristics.

Metals in Occluded Water: A New Perspective for Pollution in Drinking Water Distribution Systems

“…Thirty-six days later the concentrations of copper and chromium ions in the occluded water decreased by 84.9% and 93.5%, respectively. One of the reasons for this phenomenon may be that corrosion scales are mainly composed of iron oxide (hydroxide) and have an adsorption effect [26,27]. Copper and chromium in the occluded water were adsorbed on the corrosion scales, resulting in a gradual decrease in the concentrations of copper and chromium (Figure 3).…”

Studying the impacts of non-routine extended schools' closure on heavy metal release into tap water

“…12 The presence of oxidants such as free chlorine and DO under regular water use conditions improves the stability of metallic corrosion products; however, under extended stagnation conditions, their absence or low concentration promotes the solubility of corrosion products and increases their release into water. [51][52][53] Water chemical quality…”

Hydraulic and Technological Investigations of a Phenomenon Responsible for Increase of Major Head Losses in Exploited Cast-Iron Water Supply Pipes

“…This phenomenon is caused by an incrustation of pipe walls by sediments precipitating from water or being a product of pipe corrosion [6,7], sometimes being socalled hydrobiological accretion [8][9][10][11]. It leads to a recurring pollution of the treated water in the water supply system [12,13] as well as reduction and deformation of the cross-section area of the pipelines. Along with the exploitation time of a cast-iron pipeline, the absolute roughness k of its internal wall increases [14][15][16][17].…”