A holistic assessment of discolouration processes in water distribution networks

Reducing discolouration events in aging water supply networks is a major challenge facing water utilities worldwide as they are required to comply with increasingly stringent water quality regulations in a proactive and cost-effective manner. Emerging control methods for dynamic reconfiguration of network topologies could reduce the risk of discolouration by regulating hydrodynamic conditions to facilitate the implementation of self-cleaning networks. This review paper provides a holistic assessment of mechanisms and pathways which govern discolouration processes, associated models and the impact of system hydraulics so that control rules can be formulated. The possible role of biofilms in conditioning the wall-bound cohesive layers is identified and methods for their effective removal are discussed. The information presented identifies key variables and research gaps to facilitate the development of near real-time hydraulic and network topology control for the long-term and proactive management of discolouration risk.