ANN ARBOR, MI – Ann Arbor is preparing to add a UV disinfection system to the city’s water treatment plant to help keep a diarrhea-causing parasite out of the city’s drinking water.

City Council voted unanimously Monday night, April 15 to approve a $2.6-million contract with Weiss Construction Co. to build the new system to meet state and federal requirements.

In 2017, the Michigan Department of Environmental Quality notified the city its drinking water from the Huron River contained levels of cryptosporidium, a waterborne parasite, requiring additional protections to comply with U.S. Environmental Protection Agency rules.

The city must install the UV system by June 2020 to comply. The project includes new piping, ultraviolet light reactors, electrical work and control modifications.

Cryptosporidium is a microscopic parasite that can live in the intestines of humans and animals and cause a diarrheal disease called cryptosporidiosis, according to the Centers for Disease Control and Prevention. Both the disease and the parasite are commonly known as “crypto,” and it’s in Huron River water.

City Council adopted a 146-page plan for the UV disinfection system Monday stating the city is not currently in violation in terms of contaminant levels and there have been no disease outbreaks, but the city is required to provide additional crypto control due to high concentrations detected in the past.

According to a chart provided by the city last fall, the running annual average of crypto in the city’s source water was above the EPA “red line” level from late 2014 into 2015, but it has stayed below it since 2016. If it’s above the red line, more treatment is required.

Under normal conditions, the city can meet the requirements, but there are times, such as during annual maintenance at the plant, when the city is unable, hence the need for a UV system, said Brian Steglitz, water treatment plant manager.

In addition to the $2.6 million base contract with Weiss, the city has a $260,000 contingency for the project.

Council also voted to increase a separate engineering contract for the project to $374,315. LG Design Inc. did a $24,500 study for the city and is helping design the system.

The new UV treatment is just one of several projects the city has planned to improve its water system.

“Ann Arbor has a proud history of providing safe, reliable drinking water to its customers, complying with drinking water regulations, and planning for the future,” the project plan states.

“In the 1990s, Ann Arbor implemented ozone disinfection and granular activated carbon to enhance disinfection, reduce disinfection byproducts, and provide better tasting water for its customers.”

In 2006, the city completed a comprehensive plan to prioritize additional improvements.

The city is now planning more than $280 million in upgrades over the next several years, including replacing a large portion of the water treatment plant and aging water mains.

The city also has been installing new carbon filters to reduce harmful PFAS chemicals in the city’s drinking water.

17 Carbon filtration media installed at Ann Arbor Water Treatment Plant

The city’s staff says water rate increases are needed to fund ongoing improvements, but City Council is divided 6-5 on increasing rates at this time. Council will vote on new rates next month.

Council approved another $200,000 contract increase with the Stantec engineering firm Monday for other water system projects.

Stantec has been helping the city with work related to the Barton Dam turbines, a survey of Barton Pond where the city gets most of its drinking water, Barton pump station and water intake improvements, an ozone chiller replacement project, Geddes Dam repairs and other miscellaneous engineering work.

The firm’s assistance is needed to maintain an aggressive capital improvement schedule, Steglitz said.

Whether the new UV system can treat for dioxane, another threat to the city’s water supply, has come up.

“UV doses for 3-log inactivation of Cryptosporidium are not effective for removal of contaminants such as 1,4-Dioxane,” the city’s UV system plan states. “Much higher UV doses combined with hydrogen peroxide can be used for oxidation of certain chemical contaminants. This is called the UV advanced oxidation process.”

The city’s water system is projected to serve nearly 142,000 people by next year and more than 152,000 people by 2050, including customers in the city and Scio and Ann Arbor townships.