This European Standard specifies characteristics and related requirements, assessment methods, the marking and assessment and verification of constancy of performance (AVCP) procedures for prefabricated secondary treatment units for populations up to 50 inhabitants. Prefabricated secondary treatment units in accordance with this European Standard are: - used for the treatment of effluent from product in accordance with EN 12566 1 or EN 12566 4; NOTE Equivalent septic effluent may come from existing septic tanks. - made of concrete, steel, PVC-U, Polyethylene (PE), Polypropylene (PP), Glass Reinforced Polyester (GRP-UP), Polydicyclopentadiene (PDCPD), PVC and/or EPDM; - used on the top of the ground (outside the building) or buried in the ground; - with or without extension shaft; - made of components that are packaged or site-assembled and placed on the market as a kit by one manufacturer. This European Standard does not cover prefabricated secondary treatment units: - where vehicle lo