NITRIFICATION/DENITRIFICATION OF WASTE MATERIAL

摘要

A method for treating a waste material in which the material is subjected to periods of aeration with air or other oxygen-containing gas, to bring about biological oxidation and nitrification, alternating with periods during which aeration is discontinued to allow development in the material of anaerobic conditions leading to biological denitrification of the material. Aeration is discontinued when the rate of change of dissolved oxygen concentration in the material reaches or exceeds a predetermined value, for example 0.1 to 4 mg/l hr, and resumed after the nitrate concentration in the material is reduced to a desired level, for example after 4 hours. The method preferably takes place in a single vessel (1). Waste enters via inlet (13) and exits via outlet (14); waste entry and exit are preferably continuous. Flow of air to diffuser (12) can be cut-off by means in conduit (11), such means being controlled by a signal processor which monitors the ratio of change of the dissolved oxygen levels sensed by sensor (9). Chemicals for the removal of phosphorous nutrients may be added to the waste material prior to or during the treatment.