In Switzerland, the installation of small treatment plants in rural areas is being and will be intensified. In order to remove the numerous small pollution sites, new guidelines have been established in which basic information is given on the procedure of how to consider local circumstances of wastewater characteristics and of how to integrate local quality requirements of the receiving water into the design of small plants. The statistics on small treatment plants show a preferential application for extended aeration, RBCs and trickling filters. Due to the lack of skilled operation and maintenance, the performance of small treatment plants is not always satisfactory. New economic, reliable and less service-demanding methods are increasingly studied and applied.
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