Council Directive 91/271/EEC on Urban Wastewater Treatment was adopted on 21 May 1991, amended by the Commission Directive 98/15/EC.
Na Unión Europea, aprobouse a Directiva do Consello 91/271/EEC sobre Tratamento de Augas Residuais Urbanas o 21 de maio de 1991, emendada pola Directiva da Comisión 98/15/EC.