The Three Rivers Clean Water Plant experienced a discharge of biosolids from the treated storage tank early Wednesday.
The discharge volume, which was estimated at 600 gallons, entered the St. Joseph River through the Lincoln Street storm drains.
Crews responded immediately to stop the discharge and to clean the street. Plant officials said water samples will be taken from the river to ensure no impact to the environment took place.
Due to the dilution factor of the St. Joseph River, which flowed at a rate of 1.5 billion gallons per day during the discharge, there is very little threat to the environment.
The Michigan Department of Environmental Quality has been notified of the incident.