A few intermittent buried sand filters have been constructed in Switzerland for the onsite treatment of small wastewater sources. The good experiences to date will certainly favour a more frequent application in the future. Investigations of the hydraulic behaviour and the removal efficiency, especially in one filter during and after a hydraulic flush, showed that the hydraulic load per dosing interval should preferably not be larger than 10 1/m2,interval. Tracer experiments as well as the analysis of pollutants during the intervals revealed considerable quality fluctuations along the hydraulic peak discharge depending strongly on the instantaneous hydraulic dose. Furthermore, maturation periods of several months are necessary in order to reach a maximum steady state performance that usually includes full nitrification. Besides detailed information on the hydraulic behaviour, a series of performance data of different buried filters gives an overview of the concentrations and the removal rates observed for organic matter and nitrogen compounds.

Onsite Wastewater Treatment, Small Treatment Plant, Biological Treatment, Biological Fixed Bed, Intermittent Buried Sand Filter, Tracer Experiment, Treatment Performance
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© IWA Publishing 1990
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