Take a close look, these Humboldt penguins are actually under the water’s surface. As the birds slip into the water in Seattle’s Woodland Park Zoo, visitors can watch their underwater antics through thick panes of glass. One thing we can’t see though, is the sustainable filtration system in the exhibit. Rainwater is collected from the roof to replenish any that evaporates from the pool, while a manmade wetland delivers water from the pool to supply plants and microbes with nutrients. Water is purified through this process and then returned to the penguin pool.















