(Harlan) Harlan Municipal Utilities (HMU) is providing an update regarding a recent operational issue involving its reverse osmosis water treatment system. The situation has been resolved, and water quality remains safe.
On Friday, April 17, a 100-horsepower motor on RO Unit #2 failed, prompting operators to initiate an emergency shutdown to protect the system from further damage. On Monday, April 20, operators installed a spare 100-horsepower motor and conducted pre-startup checks, placing RO Unit #2 on standby service.
Early Tuesday morning, staff identified that a blend valve on RO Unit #2, despite not being in active service, was stuck in the open position. This created a false flow reading within the system. Because chlorine feed rates are automatically calculated based on total water production from both RO Unit #1 and Unit #2, the system interpreted a higher-than-actual water flow and temporarily increased chlorine dosing.
HMU immediately notified the Iowa Department of Natural Resources. After review, IDNR confirmed that this situation did not constitute a Maximum Contaminant Level violation and posed no risk to public health. As such, no public notification was required.
In the interest of transparency, HMU is voluntarily sharing this information with customers. Further investigation by SCADA system integrators determined that a coding error prevented the blend valve from resetting properly unless RO Unit #2 completed a full normal shutdown sequence. The coding issue has since been corrected.
As of 10:00 a.m. on Wednesday, April 22, chlorine levels have returned to normal operating ranges.
HMU remains committed to provided safe, reliable drinking water and maintaining open communication with the community.
