Waste water treating method and waste water treating apparatus

A waste water treating method for treating a nitrogen compound and a phosphorous compound in for-treatment water, which comprises:

• a first treating step of treating the for-treatment water by use of a pair of iron electrodes which are at least partially immersed in the for-treatment water, such that the nitrogen compound is converted to nitrite ions and ammonia or ammonium ions and the phosphorous compound is precipitated as iron phosphate in said first treating step, and
• a second treating step of treating the for-treatment water by an electrochemical process by use of a pair of electrodes which are at least partially immersed in the for-treatment water and are made of a noble metal or a conductive material coated with a noble metal, such that ammonia or ammonium ions are denitrified to nitrogen gas in said second treating step.

A waste water treating apparatus for treating a nitrogen compound and a phosphorous compound in for-treatment water, the apparatus comprising:

• a pair of electrodes which are at least partially immersed in the for-treatment water so as to treat the for-treatment water by an electrochemical process,
• hypochlorous acid producing means for producing hypochlorous acid, and means for feeding hypochlorous acid produced by the hypochlorous acid producing means into the for-treatment water,
• wherein one of the electrodes is a cathode made of a conductive material, whereas the other of the electrodes is an anode made of iron.

A waste water treating apparatus for treating a nitrogen compound and a phosporus compound in for-treatment water, the apparatus comprising:

• a pair of electrodes which are at least partially immersed in the for-treatment water so as to treat the for-treatment water by an electrochemical process, and
• control means for switching the polarities of the electrodes therebetween,
• one of the electrodes being a cathode made of a noble metal or a conductive material coated with a noble metal, the other of the electrodes being an anode made of iron.

A waste water treating apparatus for treating a nitrogen compound and a phosphorus compound in for-treatment water, the apparatus comprising:

• a pair of electrodes which are at least partially immersed in the for-treatment water so as to treat the for-treatment water by an electrochemical process, and
• a pair of electrodes which are at least partially immersed in the for-treatment water so as to treat the for-treatment water by an electrochemical process and are made of a noble metal or a conductive material coated with a noble metal.