Wastewater from households and industries must be treated before being discharged to rivers and lakes to ensure the safety of the water for recreation and to protect aquatic ecosystems. While modern technology seeks to address these water quality cleanup requirements, the introduction of new and different pollutants and the need to design treatment technologies that are both economical and effective continues to provide a challenge to engineers. In this module, students examine the sources and characteristics of wastewater and are introduced to the government regulations that specified required levels of treatment. We then explore the engineered processes used to treat wastewater in cities, rural communities, individual homes and aboard the International Space Station. Supports Water Unit Lesson 6.