Résumé :
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Anaerobic digestion processes for the treatment of wastewaters and sludges are well over 100 years old. The anaerobic process is a natural gasification process, producing very useful end-products. It has taken a long time to prove that these processes are useful tools in sustainable development. A breakthrough was the development of the Upflow Anaerobic Sludge Bed reactor by Professor Gatze Lettinga. This showed that the anaerobic process could be operated as a highly effective and high-rate wastewater treatment process, opening the way to its implementation under practical conditions. It has, so far, been a struggle to prove the feasibility of anaerobic treatment, despite the obvious advantages in energy consumption, sludge production, and required land area; its drawbacks, i.e. required effluent polishing, odours, sensitivity to toxic compounds, made potential users reluctant to choose anaerobic instead of the conventional aerobic systems. However, as shown by the contributions in this issue, intensive research has overcome most of these drawbacks.
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