Chemical and microbiological safety of drinking water in distribution networks made of plastic pipes

In recent years, metal alloys used for drinking water distribution are gradually being replaced by PVC and HDPE pipes. In areas of distribution networks made of plastic, consumer complaints related to a significant deterioration of organoleptic parameters of water are frequently recorded. The decline in water quality is most likely the result of chemical and biological processes occurring on the inner walls of the transmission pipes coexisting with the disappearance of disinfectant residues. Plastic pipes are also characterized by high failure rates associated with aging of polymeric materials under operating conditions. Published reports indicate disturbing phenomena occurring in plastic pipes: oxidative aging of polymers, degradation of antioxidant coatings, release of organic compounds to water as well as surface damage and scaling, generating microplastic particles. PE and PVC networks are also susceptible to biofilm formation, characterized by a high phylogenetic diversity of microorganisms. Studies presented in the literature, indicating the risks resulting from the exploitation of PE and PVC pipes, are mainly based on model tests. There is a lack of works, which would complementarily explain all the phenomena occurring in working water pipes made of plastics. The aim of this review is to present the current state of knowledge regarding the phenomena and processes that can occur in PE and PVC pipes in service and their relevance to the safety and quality of drinking water in distribution networks, as well as to identify areas that require further analysis to enable water producers to deliver an appropriately high-quality product to consumers.