Particles in the drinking water system: from source to discolouration

Water discolouration in networks results from increased turbidity due to high levels of suspended particles. Hydraulic incidents such as pipe burst or hydrant use impose extra shear stresses on sediment layers in the network, leading to particle resuspension. The mass balance over a network or parts of the network may be used to analyse the different sources and accumulation processes; this article focuses on the contribution of the "mass in" from the pumping station as particles. Three analysis methods have been developed within the joint research program of the Dutch water companies (BTO-program): the continuous monitoring of turbidity, the Mass Settling Potential Method and the Resuspension Potential Method. The continuous monitoring of turbidity and particle counting enable an analysis of the relative contribution of sources for particles, e.g. corrosion of cast iron. The Mass Settling Potential and Resuspension Potential methods add insight into actual sediment load and actual discolouration risk. Further development of these methods will enhance knowledge of the origin and fate of particles in a network, enabling the formulation of effective measures against discolouration and associated water quality problems.