Aquarellus: a numerical too to calculate accumulation of particulate matter in drinking water distribution systems

Abstract

[EN] Despite preventive measures, turbid (vernacular: “discolored”) distributed drinking water is still a common cause for customer complaints across the world. Discoloration events are caused by the accumulation of particulate matter in drinking water distribution systems (DWDSs) and subsequent remobilization during hydraulic events [1], although uncertainties remain concerning the specific accumulation and transport processes. For Dutch DWDSs, it is plausible that microscopic particles originating at treatment plants contribute substantially to the particulate matter that resides in DWDSs, and that physical processes within the distribution network are cardinal in the subsequent transport during distribution. Aquarellus, a predictive numerical tool has been developed to predict the accumulation of particulate material in DWDSs. It integrates hydraulic calculations using the EPANET toolbox with a particle transport module that is based on a description of gravitational settling, particle stagnation, bed load transport, and resuspension of particles in distribution pipes, depending on the shear stress near the pipe wall [2]. The performance of the multi-core calculations allows for simulating distribution network sizes that are common to Dutch water utilities (100s of km total pipe length). The user can assign the injection of multiple particle species corresponding to temporal patterns at multiple source locations. A graphical user interface handles user IO and the visualization of geographical maps as well as time-dependent build-up of particulate material across the distribution network and within individual pipes. To characterize particle properties (critical input parameters) encountered in Dutch DWDSs, we performed lab experiments on 9 samples from 3 water utilities to determine particle size distributions, mass density, mobility thresholds, and a measure for gravitational settling. Using the outcomes of these lab experiments, a sensitivity test with a range of input parameters was performed in Aquarellus. This helped determine how the variation in the relevant input parameters influence the calculated spatial patterns of accumulated particulate matter ̶ a measure for the discoloration risk. We compared the modeling results to turbidity measurements from systematic cleaning actions in a real-life Dutch distribution network (Spijkenisse). Finally, we will discuss the potential for applying the tool to assist the planning of cleaning actions and monitoring programs.