Development over the last 200 years has taken Swedish society from dugout latrines, to underground sewers flowing into lakes or coastal waters, to advanced wastewater treatmentplants. Wastewater issues have changed from resolving local sanitary problems to a global environmental issue.This paper ’Wastewater Treatment in Sweden’ is published by the Swedish Environmental Protection Agency (Swedish EPA) to provide an historical overview of development of urban wastewater treatment from 1900s to the present. The paper is published biannually and includes the most recent statistical data from 2020 for releases and sludge from wastewater treatment plants.This information is published in accordance with Article 16 of theUrban Wastewater Treatment Directive (91/271/EEC). The Directive applies to all wastewater collected in sewage systems, but specific requirements apply only to treatment plants serving more than2,000 persons. For Sweden, this corresponds to over 400 wastewater treatment plants.