DUAL-USE FILTERS KEEP WET-WEATHER FLOWS UNDER CONTROL.

Through a storm-water bypass system completed with other plant improvements in 1985, the Wheaton, Illinois Sanitary District municipal treatment plant has increased its wet-weather hydraulic capacity without expanding biological treatment or resorting to underground storage systems. The Wheaton solution is designed around six pulsed-bed, rapid sand filter cells that normally accept secondary effluent. However, during wet weather, they are assigned to treat primary effluent to a level that allows chlorination and discharge without further process steps. The new process diverts flows above 14. 5 mgd to a modified excess-flow treatment scheme.