Five questions for Michel Dutang, Research and Development Manager at Veolia Environnement
Michel Dutang
Valeurs Vertes: Do you think there could be a lack of drinking water one day?
Michel Dutang: There is no risk of that, water doesn't simply disappear because it works in a cycle. However, resources must be conserved by purifying and avoiding pollution. In developing countries, real problems of resources could arise due to the lack of measures taken for conservation, purifying and recycling water.
Valeurs Vertes: What technologies could help deal with the constantly increasing demand for quality?
Michel Dutang: Basically, by using membrane technology. These procedures were discovered 20 years ago but they always lead to great progress. Improvement in the membrane procedures over 15 to 20 years will, to a large extent, decrease energy consumption by five. We should bear in mind that the use of membranes requires energy consumption as high as that needed to pump water. The finer the membrane to reach osmosis the more energy is required: 60 pressure bars for example to desalinate sea water. If we could divide this amount of energy by two, the procedures would be profitable for countries that have never been able to access them, like Palestine, which lacks water. It is not desalinating sea water that cost s the most but the energy needed for the procedure itself. This energy cost is an increasingly important issue.
Another technological issue: membrane sludge. The finer the membranes are the more risk of sludge, like sea water with algae. This involves maintenance and cleaning costs.
Valeurs Vertes: How can progress be made in solving the problem of sludge treatment?
Michel Dutang: More sludge means treatment of more and more water. Using sewage treatment for everything for several decades has meant there is no industrial pollution. High quality compost is obtained when nitrogenous and phosphorous organic life products are used. In Narbonne, where there is no industrial pollution, the sludge is composted with green waste and waste is no longer obtained but a real product, which can be monitored, labelled.
In the case of large old cities with millions of inhabitants, this monitoring is not possible, we must resort to two large scale destruction procedures, one of which is new and implies progress: oxidation by humidity, which is a process being installed in the city of Brussels. It is just like a pressure cooker with 44 pressure bars that rises to 200-300 degrees and to which oxygen is added. This procedure will be used to treat sludge in Brussels, Milan and Epernay. Another procedure: incineration, an extremely efficient controlled technique, although sometimes refused by people living nearby. Similarly, the co-incineration that consists of including damp sludge containing 80% water into an incineration oven with traditional household waste. This water content improves combustion in the oven; it burns the sludge better by treating it. Procedures are generally becoming more and more refined as we are becoming stricter about fulfilling regulations. Drinking water that complied with the 1961 regulations thirty years ago is no longer acceptable nowadays.
Valeurs Vertes: Has the French Water College been copied?
Michel Dutang: In international tenders, the French companies are the ones that reach the final and are awarded projects. We have been able to keep up with progress because our companies have the essential level that allows them to develop their research and growth. Our department employs 600 people, half of whom are involved in basic research and the other half in development. Procedures are being perfected from the pilot workshop stage, like the one we set up for the Brussels project to treat sludge for about 30,000 inhabitants/year. Some years are still needed to reach the real scale for 300,000 inhabitants, three years in this case to perfect and complete the procedure. With a budget of €100 million and 600 researchers and engineers we will be able to establish an innovative and reliable procedure.
Valeurs Vertes: What paths are open for research in the future?
Michel Dutang: There are several, in particular the one consisting of progress in water analysis from a bacteriological standpoint to detect germs and virus. We are working with the Pasteur Institute on the procedure to detect DNA in these pathogen agents in order to deal with them better.
Another path is the evaporation-concentration techniques that are still not perfect and are above all very energy consuming, but in 10 years time these procedures could be very interesting. We are working on drying polluted sludge to produce fuel. If at the moment you laugh at this procedure because it would require such great deal of energy, just remember that the old coachmen used to make fun of the first motorised vehicles, yet the latter has lasted much longer than the former. Thermodynamics could imply great progress. Another topic for the future: controlling the behaviour of pollutants in the natural environment, in underground waters, rivers and water reserves. It is healthier to purify what is naturally thrown in the water than to use a damaged natural environment to produce drinking water.
The aim is to eventually produce water without treatment thanks to improved knowledge of this natural environment for it to be modelled to attain the final goal: a return to the natural state once it has been purified of all the pollution.
Interview with Danielle Nocher
