SEWAGE TREATMENT APPARATUS

PROBLEM TO BE SOLVED: To provide a sewage treatment apparatus capable of removing both of phosphoric acid and nitrogen. SOLUTION: A sewage treatment apparatus is equipped with a sewage housing tank, electrodes 2 and 3, a DC power supply and a control part. The electrodes 2 and 3 comprise rectangular iron plates to elute iron ions removing phosphoric acid in sewage by electrolysis. The lower half parts of the electrodes 2 and 3 are covered with carriers 9, 10 comprising porous reticulated members made of a polypropylene resin. The carriers 9 and 10 allow microorganisms participated in denitrification reaction to live in sewage. When the control part reverses the polarities of the electrodes 2 and 3, phosphoric acid is removed by the flocculation reaction of iron ions and phosphate ions in sewage on the side of the electrodes 2 and 3 becoming anodic in polarity. Further, on the side of the electrodes 2 and 3 becoming cathodic in polarity, nitrogen is removed by denitrification reaction based on the microorganisms on the carriers 9 and 10.