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 (e.g. from washing machines or baths); often reused for purposes other than drinking (e.g. 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