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ERCIM News No.48, January 2002 [contents]
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TELEMAC — Telemonitoring and Advanced Telecontrol of High Yield Wastewater Treatment Plantsby Olivier Bernard TELEMAC is a recent research project coordinated by ERCIM. The project’s aim is to design a reliable modular system based on anaerobic digestion, which supports remote monitoring and control of wastewater treatment units without the need for local expertise. TELEMAC focuses on a re-emerging industrial wastewater treatment technology, namely anaerobic digestion, which up until this point has not been exploited to its full potential due to a lack of tools. The anaerobic wastewater treatment process is based on a complex ecosystem of anaerobic bacterial species that degrade organic matter. Compared with the traditional aerobic treatment, it has a high capacity to degrade difficult substrates at high concentrations, produces very little sludge, requires minimal energy and can even recover energy using methane combustion (cogeneration). However, in spite of these advantages, industry is reluctant to use anaerobic treatment plants because they can become unstable under certain circumstances. A disturbance can lead to a destabilisation of the process due to accumulation of intermediate toxic compounds resulting in biomass elimination. In such a case, several months are necessary for the reactor to recover. It is therefore a big challenge for computer and control sciences to make this process more reliable, more profitable and usable on an industrial scale. TELEMAC will develop an efficient and reliable monitoring system for controlling anaerobic digestion, despite the uncertainties and the variability inherent in the biology. Managing such an efficient but unstable nonlinear biological process remotely is a challenge that will require both environmental technical skills and IST competencies. With such a system, depollution will become possible even in remote areas. Using a network of smart sensors, robust advanced control procedures, fault detection and isolation techniques, a centre of remote experts will be able to manage the complex nonlinear anaerobic digestion process via the Internet and assist the local technician at the local treatment plant. The expected results are:
Coupling diagnosis and advanced control techniques is the core of the solution proposed by TELEMAC for the management of anaerobic treatment plants. The fault detection and isolation module must be able both to detect faults in the process and to determine the origin of the problem. When a failure is detected, the model corresponding to the symptoms of the process will be chosen from the model base developed specially for faulty situations. The software sensors and the control algorithms based on the selected model will then be activated. The supervision system must not only test the integrity of the process, but must also verify that the selected algorithms (eg, controllers, software sensors, fault detection) do their job properly. In this case, it must therefore also be able to check the coherence of the algorithms' outputs with their theoretical properties (eg, convergence rate, dynamical behaviour). If they turn out to be inefficient, an alarm will be triggered. In addition, the supervision system will take advantage of the advanced methods relying on analytical models (eg, software sensor predictions, residuals generated from the model, process forecasts) to provide a new set of rules for the fault detection and isolation procedure, so as to improve the diagnosis. This synergy between advanced control (ie, mainly analytical model-based control) and advanced supervision systems (based on fuzzy logic, qualitative reasoning, machine learning) is a very promising and innovative idea for biological wastewater treatment processes. Another innovative aspect is the original management approach of a wastewater treatment plant. Data from the sensor network, faults, controller outputs, simulations, and expert consultancies are combined in a supervision system, and the outcome is structured, harmonious and formalised on-line information. The history of the plant can be invoked directly to feed and improve the management policy, and eventually, to make its telemanagement accurate and efficient. This will improve the knowledge of plant operation and will be employed to optimise the cost/performance ratio. The system will be validated with partners from the winery industry. The treatment of vinasses and alcoholic wastes is difficult and these pollutants have a deep environmental impact both in Europe, where the wineries belong to the category of sensitive industries, and in other regions of the globe, where they are responsible for tremendous damage to water resources (Mexico, Brazil, etc). Most of these wastes are produced by SMEs and generate significant and disseminated pollution. For example, a middle-sized winery generates pollution equivalent (in Biological Oxygen Demand) to a town of 15 000 people. The project will provide SMEs and larger corporations with an efficient anaerobic wastewater treatment plant and a remote expert centre via the Internet. The project is being carried out by a consortium of European and South American partners under the scientific coordination of Olivier Bernard from INRIA. Link: |
