METHOD FOR REMOVING HARDLY DECOMPOSABLE ORGANIC MATTER

PROBLEM TO BE SOLVED: To improve the availability of ozone without needing of 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 contact tower 3 and a biological filter bed 4 successively to decompose the hardly decomposable org. matter in the raw water by an ozone oxidation-treatment and a biological oxidation-treatment, a biologically treated water flowing out from the biological filter bed 4 is shunted to return to an inflow part of the ozone contacting tower 3 and to execute repeatedly the ozone oxidation- treatment 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.