GRIDLEY STP - Secondary Wastewater Treatment Plant in Gridley, Illinois

GRIDLEY STP is a municipal wastewater treatment facility located in Gridley, McLean County, Illinois. The plant serves a population of approximately 1,210 residents, providing essential sanitation services for this small Midwestern community. The plant operates with secondary treatment, which is the standard level required by the U.S. Clean Water Act for municipal wastewater facilities. With a designed capacity of 681.37 volume units and an average discharge of 492.10 volume units, the plant operates below its capacity, indicating room for future growth. As a U.S. facility, it operates under the National Pollutant Discharge Elimination System (NPDES) permit program, administered by the Illinois Environmental Protection Agency. The treated effluent is discharged into local waterways that ultimately drain into the Illinois River basin, part of the larger Mississippi River watershed. This system supports diverse aquatic life and provides water resources for communities downstream. The plant's secondary treatment helps protect these water bodies from excessive nutrient loading and organic pollution.

The plant discharges into receiving waters that flow into the Illinois River, a major tributary of the Mississippi River. This watershed supports a variety of fish species and provides habitat for migratory birds along the Mississippi Flyway. The secondary treatment process reduces biochemical oxygen demand and suspended solids, helping to maintain water quality in this agriculturally intensive region.