A system for the degradation treatment of organics in organically-polluted water is provided with a treatment tank for receiving, as the organically-polluted water, sewage or wastewater from a food-related factory. The treatment tank includes an inlet, an outlet arranged at a position upper than a vertical position of the inlet, and at least one, preferably plural air diffuser pipes for intermittently feeding oxygen-containing gas into the organically-polluted water in the treatment tank. The air diffuser pipe(s) are arranged at a position lower than the vertical position of the inlet such that an aerobic zone and an anaerobic zone can be formed in an upper part and a lower part of the treatment tank to effect degradation of soluble organics in the organically-polluted water primarily with aerobic bacteria and to effect degradation of solid organics in the organically-polluted water primarily with anaerobic bacteria, respectively.On a side lower than the vertical position of the air diffuser pipe(s) as first air diffuser pipe(s), at least one, preferably plural second air diffuser pipe can be desirably arranged to intermittently feed oxygen-containing gas into the organically-polluted water in the treatment tank such that the organically-polluted water can be agitated as a whole. A process is also disclosed for the degradation treatment of organics in organically-polluted water.