SOCIAL AND ECONOMIC ISSUES
Water Distribution Networks are exposed to deliberate or accidental contamination. In particular, the drinking water supply is at potential risk of being a terrorist target and public health risks need to be detected in due time. This is why drinking water regulations require examining special germs and chemical substances on a regular basis. But today’s analytical techniques, which are carried out offline in special laboratories, are time-consuming and not efficient to warn the population of contamination risks in time. Furthermore, the techniques are limited in spectrum range – unknown or unexpected toxic substances are unconsidered which can threaten people’s health in the same way. Considering the changed level of threats an early identification of contaminants in drinking water is very important. It should respond quickly and reliably, be robust against false alarm, easy to handle by persons without scientific qualification and the operation should be economic in view of purchase and maintenance costs.
POSITION OF THE PROJECT
This project consists of a joint effort between German and French partners about research cooperation in Security in Water Distribution Networks. The sub-axis is protection of critical infrastructure and networks. This project constitutes a completely new industrial research effort. Some experimental research will be conducted at laboratory scale.
First of all, it is worth developing the complementarities with two previous EU and national projects (namely, SecurEau and STATuS) to clearly show their position with regards to the SMaRT-Online project.
1 COMPLEMENTARITIES WITH PREVIOUS FP7 AND NATIONAL PROJECTS
Research project SecurEau: The general goal of the FP7 SecurEau project (EC n° 217976) is the Security and decontamination of drinking water distribution systems following a deliberate contamination. More specifically, this project focuses on appropriate responses for rapidly restoring the use of the drinking water network after a deliberate contamination. To attain this goal, the SecurEau responses are on 4 different levels:
- Setup of an early warning system. Development of unspecific (multi-‐‑probe) sensors able to detect unexpected brutal changes to the water quality. Determination of optimal sensor locations;
- Grab/automatic sampling for identification or detection of the contaminant in a rapid and accurate manner. The early warning system has raised an alarm? There is high probability of a real contamination with potential risks. We want to identify it. It could be chemical, biological, radiological or nuclear;
- Contamination source identification and definition of the areas contaminated. Sorption/Reaction phenomena have been studied for a large array of contaminants to give an indication of the contaminated media (water and bulk flow, pipe wall and biofilm, sediments…) the level of importance and the transport. Additionally, contaminant source identification problem is solved to pre‑localise the sources of the problem;
- Decontamination procedures and control of the decontamination efficiency. New methods to decontaminate polluted installations including an integrated approach to neutralise water. A lot of scenarios are tested, with chemical (chlorine, hydrogen peroxide, peracetic acid…), mechanical (flushing, air scouring, swabbing, pigging…), or a combination of these methods. The control of the efficacy of decontamination, by using sensors (deposits measurements) and methods developed previously (in SAFER, a previous EU-funded programme under the 5th Framework, is also required), as well as a method verifying the efficiency of fixed bacteria (use of fluorescence coupled with FlowCytometry) (coupons installed previously, permanently, in representative areas of the network).
This four-year project has included in its final year a demonstration of the previous concepts.
On one hand, data acquisition, treatment and online modelling as calibration are not considered in the SecurEau project. On the other hand, determination of optimal sensor locations and contamination source identification are part of the SecurEau project. One objective of SMaRT-OnlineWDN is to complete and improve the previous methods to fully benefit from online water quantity and quality information. The multi-probe sensors will be used in combination with biological based toxicity sensors (biosensors) to improve the detection probability. It is expected the global false‑negative probability will be reduced for the sensor network. Moreover, optimal water quantity locations are also proposed to improve the observability of the hydraulic state in quasi real-time with less uncertainty in the predictions. It will immediately benefit the conditioning of the contaminant source identification problem, improving the source detection process. It will also be of benefit by reducing the uncertainty for contaminant impacts in a contaminant event scenario. Finally, the optimal sensor placement problem is understood as an adaptive sampling design problem with successive improvements by expanding an existing sensor network.
Research project STATuS: STATus is a research project in the field of network analysis and modelling funded by the BMBF, the German Federal Ministry of Education and Research. German Partners from the STATuS project possess skills in online modelling but not dedicated to security management.
In the first phase of STATuS the vulnerability of water distribution networks against deliberate contamination of the drinking water was studied. A risk-based approach was chosen. The results showed that the common technique of modelling the distribution system by use of calibrated offline models is not accurate enough for its application as an operative security tool in case of an emergency. In addition it was demonstrated that the risk (as product of probability of occurrence and impact of an event) is highly affected by the specific hydraulic state of the system, the volume of water that is used as carrier medium for the contaminant and the time interval during which the contaminant is pumped into the system. In particular, it was shown that the impact of an event at a certain location, especially in branched sub-networks, is not a continuous function of input mass per time but rather jumps up dramatically in the case where the input flow of contaminated water is large enough to displace the existing pipe volume of the sub‑network and the contaminant reaches superior main lines.
It is mandatory for the applicability of hydraulic simulation as an operative tool that the calculation draws a reliable picture of the current hydraulic state and water quality of the physical system. For this reason, it was decided that in the second phase of STATuS the prototype of an online water network security tool will be developed and implemented in a selected pilot zone of a real water distribution system. During the first step the existing SCADA system of the participating water supply utility will be completed by additional new multi parameter sensors and connected to the hydraulic simulation model using OPC client-server architecture.
SIR 3S®, the simulation software used for the project, has already been successfully applied for online simulations of district heating networks and oil and gas pipelines. The software includes an OPC client enabling data exchange with any SCADA system that implements an OPC server. The online model of the pilot zone of STATuS is under construction at the moment. It is planned to carry out a series of field tests with different input scenarios and operations within the subsystem. One of the objectives is to study the behaviour of water quality parameters like conductivity, pH, turbidity, chlorine and temperature. Due to the relatively high cost for toxicity sensors, it shall be tested if common water quality sensors can support the detection of anomalous conditions. All the tests will be accompanied by online calculations. The issues in question are manifold: How can we reach a good matching of hydraulic measurements and calculation results? It is expected that the estimation of demand and its distribution in (near) real-time is crucial to this task. How can we get a good matching between water quality measurements and calculation results considering incomplete mixing? How can we integrate higher functions like source identification and how accurate are the results? What are appropriate time intervals for the online calculations and measurements?
2 POSITION OF SMART-ONLINEWDN
During the last years, powerful online toxicity sensor systems have been developed (e.g. AquaBioTox sensor system, a prototype by Fraunhofer IGB and IOSB (Bernard, Kuntze et al., 2009; Sedehizade, 2009)). For the first time, these online sensors enable the WDN operator to implement an online monitoring system of the network. On the other hand, these toxicity sensors are still quite expensive; hence the operator can only install a small number of such sensor systems in the network. Furthermore, these biological-based sensors tend to raise a relatively high rate of false‑positive alarms as it is difficult to maintain the sensor at a constant “operating point”. For most WDN operators one false alarm per year per sensor would be inacceptable.
In combination with this very sensitive warning system, another system could be setup. New options in this direction are offered by low-cost multi-probe sensors for measuring standard water quality indicators, such as chlorine residuals, pH, turbidity, and total organic carbon.
The development of such low-cost sensors is one output of the EU FP7 SecurEau project (SecurEau, 2011). The expectation is that if a contamination event occurs then significant variations in monitored water quality indicators will result. Else, it will pass undetected and a false-negative occurs but for a very low probability. A first question arises from the nature of the numbers and the location of sensors to install for monitoring of a water distribution network: The cheapest but less sensitive ones or the most expensive and most sensitive options or a combination of both.
Such a sensor network produces online data in great numbers. Acquisition of such a huge data stream and assimilation raises a challenging problem. To summarise, the first goal of this project is the development of the concept of an early warning system and a software solution for the reliable alarm generation in water distribution network. The early warning system consists of biologically based toxicity sensors and multi‑probe physical/chemical water quality parameters.
In case a reliable alarm has been generated, the WDN operator has to react very fast. Humans have to be protected against toxic drinking water. Hence the operator is highly interested in getting an answer to these questions very quickly: Where is the contamination source? What impact will the contamination have on the water distribution network? Which actions are necessary (e.g. which main pipes have to be shut)? Obviously in case of a toxic contamination, WDN operators need high quality decision support by means of powerful software tools in order to make the right decision in a very short time. The decision support has to be based on a reliable hydraulic picture and water quantity meters and sensors (pressure, velocity) are needed. So, it is expected in this project that a sensor network for both, water quantity and quality, linked with an online model of the WDN will allow (i) an estimation of the localisation of the contamination source and (ii) the simulation of short-time future scenarios in order to estimate the impact of a contamination source.
Hence the global aim of the proposed project SMaRT-OnlineWDN is the development of an online security management toolkit for water distribution networks (WDN) that is based on sensor measurements of water quality as well as water quantity (pressure, flow). Its field of application ranges from detection of deliberate contamination, including source identification and decision support for effective countermeasures, to improved operation and control of a WDN under normal conditions (dual benefit). Detailed information regarding contamination sources (localisation and intensity) is explored by means of an online running model, which is automatically calibrated to the measured sensor data.
In this project, the technical research work is completed with a sociological, economical and management analysis by the Engees Partner in France. Considering social science and economics combined with applied mathematics, civil and environment engineering and fluid mechanics research defines a pluridisciplinarity approach. The project objectives are discussed more detailed in the sequel chapter 2.4.
The cooperative research project consists of end users (BWB‑Berlin in Germany, CUS, Veolia-Vedif in France), technical and socio‑economic research institutions (Fraunhofer IOSB, TZW, Irstea, ENGEES) and industrial partners on both the French and the German side (Veolia‑Veri, 3S Consult). It ideally combines top-level research with the practical needs of water supply utilities. Majority of partners have experience from other research projects on water network security (project FP7 SecurEau: Irstea, Veolia, project BMBF STATuS: IOSB, TZW, 3S; project BMBF AquaBioTox: IOSB, BWB in Germany). The overall consortium supplements well together: From the SecurEau project and Veolia partner, " low-cost " multi-probe sensors were designed for monitoring usual water quality parameters.
Irstea, also involved in the SecurEau project, will bring its experience for optimal sensor placement and offline contaminant source identification. German Partner from STATuS project possesses skills in online modelling but not dedicated for security management. German partners from AquaBioTox have designed a biological-based sensor that can be placed in a WDN. Finally, CUS water service authorises the application of methods that will be developed by German and French and Engees permits to add in pluridisciplinarity by its contribution in risk analysis and evaluation of impacts.
