The Dutch drinking water utilities abide by the legal provisions for monitoring the microbial quality of drinking water in the distribution network. The monitoring programme for this regular control is established in the Drinking Water Act and is supervised by the Human Environment and Transport Inspectorate (ILT); among its stipulations is the mandatory frequency of measurements. In their regular control programmes, and following work activities on the network, the drinking water utilities collect 100 ml samples, which are analysed for microbial parameters (coliforms, coli group bacteria and, when the latter is positive, also for E. coli). These organisms do not in principle come from the pumping station, but they are present in the environment or in faeces, and are therefore an indicator of contamination in the pipe network – e.g., resulting from a leakage or the network’s depressurisation during work activities.
Optimising sampling locations
Numerical source-determination methods offer the possibility, on the basis of positive measurements, of determining the risk areas in the distribution network. With this in mind, KWR has developed and tested a numerical tool within the institute’s Joint Research Programme with the water utilities. The tool makes it possible to determine optimal measurement locations and to identify potential source-areas of contamination. The CST method has already proven its worth: contamination source locations in a distribution network have been successfully identified (Van Summeren, 2014); to be sure, this requires a sufficient number of measurements and a representative hydraulic model.
The objective of this project is to use the CST tool to optimise sampling locations, and thereby increase the chance of detecting possible contaminations in the pipe network. This makes it possible, following a positive measurement, to quickly determine the locations for follow-up measurements, so that the potential source area can be effectively identified.
We will collect data on coli group bacteria from Brabant Water. Using a representative distribution network model, we will then apply CST to calculate the optimal measurement locations, and we will develop a method to determine the optimal locations for follow-up measurements. In the development phase, we will learn about the calculating rate and effectiveness of the containment of the source area. Based on the outcome, we will determine the method and the size of the evaluation area.
Recommendations for application in Brabant Water’s data and visualisation platform
The proposed research is linked to the current development of a comprehensive data and visualisation platform by Brabant Water, which is intended for the use of numerical models and measurement and environmental data for operational objectives.
The method developed in the project will be applied to a selected evaluation area in the Province of North Brabant, for which newly measured positive detections will be used. Calculations will be done for the locations for follow-up measurements, which Brabant Water will then carry out.
On the basis of the research results, we will present recommendations on the implementation of the developed method as a real-time data application by Brabant Water.