This document discusses sustainable sanitation and sanitary conditions around the world. It notes that 2.5 billion people lack improved sanitation and many developing countries treat little of their wastewater. It also discusses diseases related to poor sanitation like diarrhea and ascariasis. Sustainable sanitation systems must protect human health, not harm the environment, be appropriate and affordable. Functions of sanitation include excreta containment and treatment, greywater management, and stormwater handling.