Degradation of asbestos – Reinforced water supply cement pipes after a long-term operation

• Published in: Chemosphere (Oxford) Vol. 287; p. 131977
• Main Authors: Zavašnik, Janez, Šestan, Andreja, Škapin, Srečo
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2022
• Subjects: Asbestos cement; Asbestos fibres; Ca leaching; Degradation; Scaling; Water pipes; Asbestos cement; Degradation; Scaling; Ca leaching; Water pipes; Asbestos fibres
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2021.131977

Potable water supply system in major countries still uses a large proportion of asbestos-cement (AC) pipes for fresh drinking water delivery. Generally, after installation and initial purging, the AC tubes are believed to self-passivate by calcite scale and bio-film, especially when conveying hard water. However, the overall performance of AC tubes after decades of operation is significantly reduced and is still mainly unknown. In the current research, we investigated the AC water supply tube after 56 years of operation with high-hardness conveyed water. Our results show that asbestos fibres are emitted from degraded AC pipes as a result of wall softening due to calcium leaching from hydrated cementitious materials, resulting in the loss of mechanical stability. Although the water pumped into the system is not considered aggressive, the seasonal variations of water temperature and chemistry results in an interplay of calcite scaling and Ca leaching, the latter being the dominating process. By comparing the experimental observations with the long-term chemistry reports of the water supplied through the pipes, a positive relationship was established between the temperature and quality of the conveyed water with the corrosion and the calcite scale formation, which are dictating the emission of the fibres into the drinking water. In addition to the health risks posed by asbestos, these processes have many adverse effects on drinking water supply, such as pipe malfunction and destruction resulting in water loss, reduction of hydraulic capacity, microbial proliferation, and water quality deterioration, a topic of interest for global water industries process. •Deterioration of AC water pipe is seasonal and temperature and pH-dependent.•Higher water temperature results in calcite scaling, isolating the asbestos from drinking water.•Lower water temperature cause dissolution of calcite scales and Ca leeching from cement.•Porous degraded layer is mechanically unstable and results in spallation when subjected to vibrations.•Cement degradation by calcium leaching is the main reason for asbestos fibres release in drinking water.