Microplastics could pose big treatment challenges

Water flows through a number of grid chambers.
Just after the initial screening, water flows through a number of grid chambers at the Metropolitan Wastewater Treatment Plant in St. Paul on Aug. 1, 2017. The chambers slow the water down to 1 foot per second allowing sediment to settle into sludge to be removed, along with 70 to 80 percent of microplastics.