Fuente: WIPO "organic farming" A cleaning system (1) for water is constituted so as to be provided with: an aerobic region (90) in which breeding water (9) that contains organic matter and oxygen are present; an aerobic layer (6) linked with this aero Die region (90) and in which aerobic bacteria make their habitat; a facultative anaerobic layer (5) provided adjacent to this aero Die layer (6) and in which facultativeanaerobic bacteria make their habitat; an obligatory anaerobic layer (4), which is provided adjacent to this facultative anaerobic layer(5), in which obligatory anaerooic bacteria make their habitat, and which is constituted b y andosol (40); an anaerobic space (3),which is an anaerobic environment into which obligatory anaerobic bacteria making their habitat in the obligatory anaerobic layer(4) and products thereof can flow; and a tube (18) as a linking means for this anaerobic space (3) and the aerobic region (90).