Abstract: To allow compact and simple design of a water treatment system capable of denitrification, an anaerobic treatment vessel 3 is provided downstream of an aerobic treatment vessel 2, and a filter layer 5 having a large number of carriers for microbes filled therein is formed in the anaerobic treatment vessel so that sulfur contents may be reduced by sulfate reducing microbes bred in the filter layer and the nitrate nitrogen is gasified by sulfur denitrification microbes with the aid of the sulfides thus obtained. In particular, the carriers preferably comprise a floating filter material in the form of plastic foam blocks that can float in the water.

Abstract: In a method for backwashing a water processing system using a buoyant filter layer constrained under wire mesh screen extending across a processing vessel, a water surface level in the processing vessel is lowered below the wire mesh screen. Air is subsequently released from under the buoyant filter layer to separate substances clogging the filter layer, while allowing the release of air out of said vessel from an upper part thereof. By lowering the water surface level below the upper wire mesh screen, the filter material is allowed to move more freely because the filter material is not restricted by the wire mesh screen from making upward movement. Hence, when air is released from under the filter layer, the filter material can move uniformly over the entire filter layer, and the clogging substances such as SS captured by the filter material and the biological film formed on the surface of the filter material can be favorably removed without damaging the filter material.

Abstract: In a water processing system for processing highly contaminated water, comprising an anaerobic chamber, an aerobic chamber, a buffering chamber, and a recycle for recycling part of the water received in the buffering chamber back to the anaerobic chamber, filter material forms a buoyant filter layer in an upper part of the water received in the anaerobic chamber without any constraint imposed on the filter material with the result that the filter layer can be highly resistant against clogging, and can be easily maintained with the result that the overall system can be made both simple and economical. Either an upflow arrangement or a downflow arrangement is possible for the anaerobic chamber. Furthermore, by using an integral structure combining various processing units into a single processing vessel, the overall size of the system can be minimized.