JPH0310364B

PURPOSE:To enable treatment generating no clogging by one stage of a disc filter and to attain decrease in cost, by performing filtering through formation of at least two layers consisting of a mat comprising a filter agent and a mat comprising a substance to be filtered. CONSTITUTION:When a sweetener 22 or a sweetener mixture 22b is supplied from an inlet box 14 and while water 21 is supplied from a second inlet box 27, liquid layer of the sweetener 21 or the sweetener mixture 22b is constituted at a water level near to a liquid surface 28 while the liquid layer of white water 21 is constituted therebelow. When a rotary disc 3 advances in the liquid, the mat 29 of the sweetener 22 or the sweetener mixture 22b is at first formed on the filtering surface of a sector 12 and, thereafter, the mat 30 of white water 21 is formed. As a result, the fine solid substance in the white water is surely collected by the first layer comprising the liquid layer of the sweetener 22 or the sweetener mixture 22b and, even in the clarification and filtering of the white water with a high concn., treatment is enabled by one stage of disc filter.