Sewage Sludge Directive

Council Directive 86/278/EEC of 12 June 1986 on the protection of the environment, and in particular of the soil, when sewage sludge is used in agriculture (OJ L 181, 4.7.1986, pp. 6-12)

https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:31986L0278

Treated sludge means sludge which has undergone biological, chemical or heat treatment, long-term storage or any other appropriate process so as significantly to reduce its fermentability and the health hazards resulting from its use.