The Iowa Department of Natural Resources blamed operator error for a 1,000 gallon spill from the Roquette America plant in Keokuk.
The sugar water ended up in the Mississippi River.
The tank from which the water spilled was shut down late Thursday night. The problem was reported to the DNR Friday morning.
Roquette America last fall paid a $4.1-million dollar penalty to settle allegations that it dumped industrial waste into the Mississippi River and Soap Creek.
At that time, the U.S. Environmental Protection Agency said the company had known for years that the wastewater treatment plant at its grain-processing facility in Keokuk couldn’t handle spills or surges.
The US EPA said instead of addressing the problem, industrial waste was allowed to discharge directly into the two waterways.