blackwater: dark water in water bodies such as rivers and waterholes, resulting from decay of excessive organic matter and consequent sudden depletion of oxygen in the water, OR raw sewage

greywater: domestic wastewater (eg from washing machines or baths); often reused for purposes other than drinking (eg watering gardens), rather than being drained into the sewerage system

wastewater: water that is degraded in quality and originates from various sources, including homes, industries and surface runoff