Public networks for urban drinking water supplies can provide potable water for millions of customers, especially in megacities. Toxic substances, whatever its origins, can threat many inhabitants within a very short period. Even a few drops could have devastating consequences. A reliable drinking water protection system is indispensable to avoid the tragic consequences of contaminated drinking water. How to solve this challenge? Collecting probes and analyze drinking water quality in a lab is not a smart solution. Such analysis takes too much time. In case of an emergency, it is not possible to react as fast as needed. A continuous monitoring in order to identify contaminations quickly and also catch unexpected toxic substances seems to be inevitable.
“In order to protect the population, we have to be able to detect the hazardous substances as quickly as possible and know how they will spread,” explains Dr. Thomas Bernard, a specialist for flow models at Fraunhofer Institute for Optronics, System Technology and Image Exploitation IOSB in Karlsruhe. The scientist and his team from the French-German project SMaRT-OnlineWDN (Online Security Management and Reliability Toolkit for Water Distribution Networks) in collaboration with partners from industry and research have developed tools that enable water utilities to respond quickly and, in an emergency, to initiate countermeasures to protect the population. The German Federal Ministry of Education and Research (BMBF) and the French National Research Agency (ANR) were promoting the project. Berlin’s water utility, BWB Berliner Wasserbetriebe, coordinated the project.
Drinking water protection with numerous simulation models
A mathematical model for simulating the drinking water supply network hydraulics and the distribution of quality parameters in the piping systems carries out several tasks simultaneously. It is based on numerous simulations and identifies the optimum locations for sensors in order to ensure early detection of contaminations. Furthermore, the online simulation model locates the source of the impurities very precise. It is also possible to calculate where the impurity will spread in the next few hours. This is a good prerequisite to put in place an early warning system. It was not a straightforward task to calculate and predict the water’s path and thus the path of the toxic substance. There is no guarantee that the water flow in the supply network is identical everywhere. “It changes depending on the pressure in the pipes, their diameter and geometry, and the number of users. And turbulence and chaotic flows occur in places where the pipe system branches.” explains Dr. Thomas Bernard.
Tests at the Water Technology Center TZW in Dresden (Germany) have helped Bernard and his French partners to establish an intelligent detection module. Installed sensors in a complex pipe network, which has been built out of Perspex, register the water’s movement. The researchers were able to optimize his computer simulations using the measurement values. The aim is to calculate the flow of the water in the supply networks of entire cities in real time. “Such simulations could assist utility companies in making the right decisions in emergencies, but only when they are precise and fast enough,” says the group leader.
90 percent of all anomalies are no cause for alarm
For a successful calculation, it is not enough to measure only the flow direction. It is necessary to consider several measurement values. The opacity, temperature, pressure, chlorine and oxygen content, pH value and the amount of bacterial contamination of the water have to be measured simultaneously. In the case of critical values, the alarm doesn’t trigger immediately. First of all, possible causes will be figured out. A different tapped water source or an opened or closed pump may be the reason. “More than 90 percent of all anomalies are caused by changes to operating conditions and are no cause for alarm,” explains Bernard.
Along with Strasbourg, Paris’s drinking water system will be monitored in the future
The research team already exceeded the laboratory stage. In Strasbourg, they implemented a new system in order to test it under real conditions. They monitor the network’s water quality in real time. Hydraulic and water quality sensors in the pipe network deliver information for the database. The collected data is then sent to a process control system. It is possible to flush contaminated water or block off parts of the supply network in case of an emergency. Along with Strasbourg, Paris’s drinking water system will be monitored in the future. A further cornerstone is a monitoring platform that takes the myriad of sensor data and clearly represents, visualizes, and stores it. It will also automatically generate reports so that, for instance, fluctuations in water quality can be regularly summarized.
The ResiWater project partners are also driving sensor development. The Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart, for example, was working for many years on AquaBioTox. This is a biosensor made from living cells that fluoresce. When bacteria come in contact with toxic substances, the intensity of the fluorescence decreases. The AquaBioTox prototype will be fully automated as part of the ResiWater project.
Information source: Fraunhofer Institute for Optronics