METHOD FOR TREATING DRAINAGE BY ULTRAVIOLET RAY

PROBLEM TO BE SOLVED: To improve a capacity of oxidation treatment by ultraviolet rays by controlling dissolved oxygen in a reactor in a process in which drainage is irradiated with ultraviolet rays in the reactor. SOLUTION: Wastewater including municipal sewage, industrial drainage, and drainage containing reducing sulfur compounds is introduced from a drainage tank 1 into a reactor 3 by a pump 2, a blower 10 is operated, and the water is irradiated with ultraviolet rays by a ultraviolet lamp 5 in the reactor 3 while the water being aerated. In this process, the radiation is done while watching dissolved oxygen (DO) in the reactor 3 as an index. With the use of a DO sensor 8 and a DO controller 9, the number of revolution of the blower is controlled automatically or manually, and aeration is conducted from an air diffusing tube 4. An ORP sensor 6 and an ORP controller 7 for monitoring and controlling oxidation-reduction potential are arranged, and the aeration or the ultraviolet radiation is controlled by ORP of the reactor 3 and/or a treated water tank 12.