NOVELTY - A wastewater treatment plant comprises a reaction tank (10) containing wastewater and a gas; gas separation units (12) dividing an internal space of tank into two sections to define a residing space by ascending gas for activation of an oxidizing reaction and a biochemical treatment zone (35, 37) at a lower portion of the separation unit for forming a catalyst layer to activate the ozone reaction while the ozone is in contact with wastewater.    USE - As a wastewater treatment plant for converting polluted matter contained in water into stable matter.    ADVANTAGE - The biochemical plant can improve the efficiency of wastewater treatment and enhances the reaction speed of the ozone through biochemical reaction. Since the gas is reacted with the catalyst layer, the ozone concentration is increased so as to realize high efficiency of wastewater treatment. Since the reaction tank has a predetermined space, it may increase the residing time of gas. The treatment plant maximizes the reaction concentration of the ozone around the wastewater surface and maximizes the amount of OH free radicals. By increasing the residing time of the ozone and by repeated contact between the gas and wastewater, the plant minimizes the ozone concentration exhausting outside in an insoluble state.    DETAILED DESCRIPTION - A wastewater treatment plant comprises: a reaction tank (10) into which wastewater and a gas are introduced; more than one gas separation unit (12) dividing an internal space of tank into upper and lower sections to define a residing space by ascending gas so as to increase a residing time of gas and an amount of dissolved oxygen by increasing a contact area of the wastewater and gas, to incur a concentration difference by a difference of molecular weight of gas, and to increase the concentration of gas caused by a catalyst reaction for activation of an oxidizing reaction; and a zone (35, 37) for biochemical treatment at a lower portion of the separation unit, and for forming a catalyst layer to activate the ozone reaction to generate a biochemical reaction while the ozone is in contact with wastewater.    DESCRIPTION OF DRAWING(S) - The figure shows a side sectional view of a biochemical plant for wastewater treatment.    a reaction tank (10)    gas separation unit (12)    gas supply tube (22)    gas supply tube (35, 37) biochemical treatment plant. (24)