NOVELTY - Treating contaminated liquid (9) by forming bacteria flora using earthworm humus (1), involves distributing contaminated liquid into the superior part of a containment tank; providing a layer of earthworm humus in the containment tank for filtering the contaminated liquid; providing a medium layer (2) for bacteria inoculation below the earthworm humus layer in the containment tank; and providing an inert layer (3) below the medium layer proximate to the base of the containment tank.    USE - For treating contaminated liquid (such as sewer water, industrial water, liquid waste, semi-liquid waste) by forming bacteria flora using earthworm humus (claimed); for cleaning sewer water (domestic), industrial water (such as food industry-related discharges e.g. slaughterhouses, dairies, vine-yards and agro industries) or other water that presents organic contamination.    ADVANTAGE - The bacterial flora inoculation system is triggered the same way (using earthworm humus) for different liquid or semi-liquid wastes. The method/system does not produce unstable muds. The system degrades the totality of the organic solids coming from the contaminated water without producing unstable muds unlike the rest of the traditional systems, because the earthworms in the medium of the bacterial inoculation degrades the totality of the solids that are retained in the system and transforms it in a stable odorless material like humus. The filtering of riverbed does not get impermeable. The system of water treatment based on bacterial inoculation needs only impulsion pumps to distribute homogeneously the contaminated water over the upper surface of the bacterial inoculator thus drastically reducing the energy costs in comparison to the traditional biological treatment systems. The method produces a sub-product that can be used as natural fertilizer.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a system for treating liquids by forming bacteria flora using earthworm humus, comprising: a containment tank for receiving a contaminated liquid distributed through an opening into the tank, where the containment tank further contains a layer of earthworm humus through which the liquid is filtered; a medium layer for bacteria inoculation below the earthworm humus layer in the containment tank; and an inert layer below the medium layer proximate to the base of the containment tank.    DESCRIPTION OF DRAWING(S) - The figure shows in-flow of water and the layers that the water crosses over (humus, cellulose material, stones and double bottom), before being released by a pendent.    Earthworm humus (1)    Bacteria inoculation medium made up of celluloid material (2)    Third layer of inert material such as quarry stones and rocks (3)    Pastelones (5)    Supports (6)    Water emitter (7)    Polyvinyl chloride perforated pipe network (8)    Contaminated water. (9)