METHOD FOR REMOVING HARDLY DECOMPOSABLE ORGANIC MATTER

PROBLEM TO BE SOLVED: To improve the availability of ozone without needing an ozone contact tower having a complicated construction and to efficiently remove a hardly decomposable org. matter. SOLUTION: At the time of introducing a raw water to the ozone contacting tower 3, a flocculate filtering vessel 4 and a biological filter bed 6 successively to decompose the hardly decomposable org. matter in the raw water by an ozone oxidation-treatment, a flocculate filtration and a biological oxidation- treatment, a treated water flowing out from the flocculate filtering vessel 4 or the biological filter bed 6 is shunted to return to an inflow part of the ozone contacting tower 3 and to execute repeatedly the ozone oxidation, the flocculate filtration and the biological oxidation-treatment. In this way, an OH radical generated by a reaction between the ozone and a radical inducing substance is used in the highest degree to the oxidation of the hardly decomposable org. matter.