NOVELTY - Contained system comprises tank having closed base and inlet at or adjacent to top of tank, tank being vertically stratified into uppermost first zone which is aerobic, second zone below first zone which fluctuates between aerobic and anaerobic conditions, and third zone below second zone which is anaerobic when tank is in use, first zone comprising first intermediate layer, and second intermediate layer, second zone comprising porous structures, third zone providing settlement pond, and unit for extracting liquids and/or solids from settlement pond.    USE - The contained system is useful for processing sewage and/or greywater (claimed).    ADVANTAGE - The contained system operates at ambient temperature without external heating compared to existing system.    DETAILED DESCRIPTION - Contained system comprises (a) a tank having a closed base and an inlet at or adjacent to the top of the tank, (b) tank being vertically stratified into an uppermost first zone which is aerobic when the tank is in use, a second zone below the first zone which fluctuates between aerobic and anaerobic conditions when the tank is in use, and a third zone below the second zone which is anaerobic when the tank is in use, (c) first zone comprising (i) a first intermediate layer which includes porous structures adapted to facilitate the movement of liquids thus aerobic conditions are maintained, and an organic matrix, and (ii) a second intermediate layer located below the first intermediate layer, comprised of materials with a C:N ratio of 25:1 and 200:1, (d) second zone comprising porous structures adapted to facilitate the movement of liquids thus aerobic conditions are maintained in the second intermediate layer, (e) third zone providing a settlement pond, and (f) unit for extracting liquids and/or solids from the settlement pond, where the system is seeded with micro-organisms and/or macroorganisms selected or adapted to digest and/or decompose inflow material. An INDEPENDENT CLAIM is included for method of using the system.