Complex sentence: The purpose of sustainable sanitation is the same as sanitation in general: to protect and promote human health by providing a clean environment that will make disease transmission unlikely, especially via the fecal-oral route.
Split into simpler sentences: The purpose of sustainable sanitation is the same as sanitation in general: to protect and promote human health. Sustainable sanitation systems provide a clean environment that will make disease transmission unlikely, especially via the fecal-oral route.