An annual report on the state's 964 community drinking water supply systems shows that 33 of them had problems ranging from bacteria to excessive arsenic in 2009.
The Minnesota Department of Health said 13 systems had detectable levels of coliform bacteria, 10 had arsenic levels that exceeded the standard and 10 had radium levels that were too high. Of those, 19 were city water systems.
Arsenic is a metal that can enter waterways from agriculture or industry, and radium is a naturally occurring radioactive metal. High exposure to each has been linked to cancer.
The presence of coliform bacteria indicates that it's possible that bacteria causing disease or illness could be in the water. Officials then examine the system further and can disinfect or flush out the system.
In 2009, the testing did not lead officials to order residents to boil their water, meaning there was little risk of illness, said Stew Thornley, a health educator with the Minnesota Department of Health's Drinking Water Protection division.
Thornley noted that since the U.S. Environmental Protection Agency made its arsenic standards stricter in 2006, the state has gone from about 40 community water systems exceeding the standard to 10 this year.
"We're still dealing with that," Thornley said. "But for the most part that's not something that's going to cause any immediate problems."
City officials are continuing to work with the health department to address any issues, he said. But health officials are pleased with the small number of problems that have been detected in recent years.
"Overall, the drinking water supplies in Minnesota are in good shape," Thornley said.
A link to the full report is available here.