A former Iowa wastewater treatment plant official has been sentenced to three months in federal prison for manipulating water sample test results to ensure plant discharges into the Missouri River met federal requirements.

Jay Niday, 63, of Sergeant Bluff, was sentenced Thursday in U.S. District Court in Sioux City and was also ordered to pay $8,500 in fines and court costs, federal prosecutors for Iowa said in a news release Friday. In October, Niday pleaded guilty to charges of conspiracy and falsifying or providing inaccurate information.

Niday was the second former plant official to be charged. Patrick Schwarte, who was a shift supervisor, pleaded guilty in January 2019 to the same two charges and was sentenced to two years of probation.

Prosecutors said Niday and Schwarte instructed other plant operators to raise chlorine levels added to wastewater on days that E. coli samples were taken. The elevated chlorine level would produce test samples showing plant discharges met federal limits for levels of fecal coliform and E. coli. Once the samples were taken, chlorine added to the city’s wastewater was reduced to levels unlikely to disinfect discharged water enough to meet those limits.

Niday told state investigators that administering the smaller levels of chlorine saved the city at least $100,000 in one year.

The city fired Niday and Schwarte in June 2015. No other plant employees have been charged.