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 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.