GARWIN STL Wastewater Treatment Plant, Garwin, Iowa | Secondary Treatment

GARWIN STL is a municipal wastewater treatment facility located in Garwin, Iowa, within Tama County. The plant serves a small population of 533 residents, reflecting its role in a rural community. As a secondary treatment plant, it provides biological treatment to reduce organic pollutants before discharge. The plant operates under the U.S. Clean Water Act, which requires secondary treatment for municipal wastewater. With a designed capacity of 302.83 cubic meters per day and an average daily flow of 227.13 cubic meters, the facility operates below its capacity, indicating room for future growth or seasonal variations. Secondary treatment typically involves activated sludge or trickling filters. The treated effluent is discharged into a local water body, likely a stream or river within the Iowa River basin, which ultimately drains to the Mississippi River and the Gulf of Mexico. The plant's location inland, far from the coast, reduces direct marine impact, but its discharge contributes to the overall nutrient load in the Mississippi River watershed, which is a concern for Gulf hypoxia.

The plant discharges into a local waterway within the Iowa River basin, which flows into the Mississippi River and eventually the Gulf of Mexico. The region is part of the Corn Belt, where agricultural runoff contributes to nutrient pollution. The plant's secondary treatment helps reduce organic matter and some nutrients, but does not provide advanced nutrient removal, which is relevant to downstream water quality concerns such as algal blooms and hypoxic zones in the Gulf.