Abstract: There is provided a nitrogen treating method capable of treating nitrogen compounds efficiently. The method is a nitrogen treating method of treating nitrogen compounds in for-treatment water by electrolysis and performs a first treating step of producing ammonia from the nitrogen compounds in the for-treatment water by electrolysis using a cathode and an anode between which a cation exchange film is interposed so as to define a cathode reaction region and an anode reaction region, and a second treating step of removing the ammonia in the for-treatment water treated in the cathode reaction region by the first treating step.

Abstract: To provide an apparatus construction which makes it possible to perform a water treatment sequence by automatic control for reducing nitrate (nitrite) ions in water being treated through an electrochemical reaction and substituting nitrogen gas for the resulting ammonia for removal of ammonia from the water; and a detecting method using the apparatus for automatically detecting the progress of reduction or denitrification, or degradation of the treating capability of cathode or anode. The water treatment apparatus comprises a cathode (15) which reduces nitrate (nitrite) ions through an electrochemical reaction, an anode (16), an electrolytic bath (10) containing the cathode and the anode, and a hydrogen gas sensor (30) which measures a hydrogen gas concentration in the electrolytic bath (10). Water to be treated is introduced into the electrolytic bath (10), and an electric current is applied to the water.

Abstract: In a water treatment apparatus, the time for treatment after water to be treated is introduced into an electrolytic bath is reduced. The water to be treated in a reservoir is subjected to electrolysis at a first electrolytic bath. Electrolysis is carried out at respective first and second electrolytic baths. By the electrolysis at the second electrolytic bath, hypochlorous acid is generated from chloride ions at the anode side. The solution subjected to electrolysis at the second electrolytic bath is mixed at a predetermined site of the pipe connected between the reservoir and the first electrolytic bath with the water output from the reservoir via a pipe prior to introduction into the first electrolytic bath. Accordingly, the water subjected to electrolysis at the first electrolytic bath can be sterilized in advance by the hypochlorous acid generated by electrolysis at the second electrolytic bath.

Abstract: An object of the present invention is to provide a water purification system capable of treating for-treatment water containing a nitrogen compound such as polluted ground water efficiently and achieving a reduction in size of the system. The water purification system comprises an electrodialyser for concentrating a nitrogen compound in polluted ground water as for-treatment water containing a nitrogen compound, a nitrogen treatment device for treating the nitrogen compound in the for-treatment water treated in the electrodialyser by electrolysis as an electrochemical process, the for-treatment water containing at least chloride ions, and a pump for returning the for-treatment water treated in the nitrogen treatment device to the electrodialyser.

Abstract: There is provided a nitrogen treating method capable of treating nitrogen compounds efficiently. The method is a nitrogen treating method of treating nitrogen compounds in for-treatment water by electrolysis and performs a first treating step of producing ammonia from the nitrogen compounds in the for-treatment water by electrolysis using a cathode and an anode between which a cation exchange film is interposed so as to define a cathode reaction region and an anode reaction region, and a second treating step of removing the ammonia in the for-treatment water treated in the cathode reaction region by the first treating step.