Abstract
Water pollution cased by eutrophication has been worse year after year. Conventional methods for purification of an eutrophicated water like fast filtration or flocculation cost quite high and some times they cause secondary pollution. In this paper very slow bottom-filter method is proposed for this purpose and experiments were carried out to evaluate the method. In theses experiments asand-filter and a gravel-filter were set on whole the bottom of tanks and the water in the tanks was circulated by a pump and a airliftpump through the filters.As the results, it is shown that water polluted by eutrophication can be purified thoroughly by a bottom-filter, remarkable clogging of the filters could not been observed, an airlift-pump can decrease pH to eliminate non-ionic ammonium which causes serious fishkill and the method can be expected not only to improve water quality but also sediment.
