In his 2017 TED Talk, Ashton Cofer explains the groups plan to make activated carbon, used in water purification systems, out of the carbon that exists in Styrofoam.
In his 2009 TED Talk, Michael Pritchard discusses his water filter technology designed to create safe, drinkable water out of the dirtiest water imaginable.
Rain gardens are exactly what they sound like: gardens. Only they're more like specially-engineered superhero gardens. Rain gardens are designed to infiltrate more water than a normal garden so that they can reduce stormwater runoff volumes and limit urban flooding. They are also capable of reducing some of the contamination in the water before it enters other water supplies like surface water or groundwater.