The low-income Enchanted Valley community just outside Rio de Janeiro’s Tijuca Forest National Park has managed something no other favela has done: built its own biosystem to process its waste. The project could serve as an example in rural areas across Brazil, where many lack access to sewage treatment facilities. The federal government has a plan to improve sewage treatment throughout Brazil, which it is pursuing through private concessions of large urban areas. But that approach doesn’t help small, isolated communities like Enchanted Valley, where the smell of sewage is now gone and its nearby waterfall is clean for bathing.