"Wastewater" refers to any water that has become contaminated by human influence, and is broken into two groups: sewage and stormwater, which are managed through separate systems in Denver.
Sewage comes from homes and businesses, commercial properties and public institutions, and is the wastewater generated from bathrooms and kitchens. Sewage runs through the sanitary sewer system, and is treated in Denver's sewage treatment facilities through a variety of biological and chemical processes and rendered safe before it's returned to the environment.
Stormwater is generated by water (from storm events or other sources) running across the surface of impervious surfaces, such as streets, sidewalks, parking lots, and roof tops where it picks up contaminants such as oil residue from cars, litter, and debris. Stormwater runs through Denver's storm drain system, where it is naturally treated and the water is reclaimed by the ecosystem.