JP2845642B

PURPOSE:To ensure that oxidized nitrogens such as nitrate nitrogen and nitrite nitrogen contained in untreated water for drinking is efficiently removed and at the same time, treated water where especially harmful nitrite nitrogen is constantly detected is obtained. CONSTITUTION:A biologically denitrification device 1 removes oxidized nitrogen in water biologically with the help of bacterial which oxidize hydrogen using hydrogen gas as a hydrogn-addition element. In the downstream of this device 1, a chemical denitrification device 7 which decomposes and removes nitrite nitrogen in water chemically under the chemcial action of a hydrogn addition catalyst such as palladium catalyst, is arranged and connected. Consequently, oxidized nitrogen contained in untreated water can be removed efficiently and at the same time, a nitrite blood stream can be completely removed using the chemical denitrification device 7, if the blood stream is ontained in a treated water flowing out of the bilogical denitrification device 1.