Procédés extensifs d'épuration des eaux usées adaptés aux petites et moyennes collectivités

The Commission's Environment-Directorate General wants to support the distribution of less intensive purifying processes, via the development of technical exchanges and advisories. This guide and the development of aids such as structural funds and cohesion funds are examples of this. This guide, which was developed within the framework of a group effort with France (Water Directorate of the Ministry of Ecology and of Sustainable Development, and Water Agencies), simply mentions the intensive techniques and concentrates, above all, on the extensive techniques for treating urban waste water. These techniques take up, by definition, more surface area than traditional intensive processes developed for large agglomerations. However, the investments costs for less intensive processes are generally less and the operating conditions of these less intensive processes are simpler, more flexible and allow more energy to be saved. Finally, these techniques require reduced manpower and less specialised manpower than intensive techniques. They can be applied in the various European configurations that do not exceed a few thousand population equivalents. One must bear in mind when reading this document that the techniques that we are going to cover cannot be used for capacities greater than 5,000 p.e. except in exceptional circumstances. After a reminder of the objectives to be met by small and medium sized agglomerations and a quick presentation of the different intensive approaches, we will describe the following techniques in more detail: - infiltration percolation; - vertical reed beds flow filters; - horizontal flow reed beds filters; - natural lagoons; - aerated lagoons; - association of different less intensive approaches In order to help in the choice of an approach, a comparison of these different techniques is carried out on the following criteria: - quality of the discharges; - advantages and drawbacks; - available space; - permeability of the ground; - adaptability of the approaches to climatic conditions; - cost