World's Largest Ultraviolet Disinfection Facility Tackles Chicago River

Engineers with the Metropolitan Water Reclamation District at the O'Brien plant's new ultraviolet disinfection facility. (MWRD)

The notoriously polluted Chicago River is about to get cleaner with disinfection technology at a Skokie water treatment facility.

Ultraviolet radiation will kill harmful bacteria and pathogens in water released from the O’Brien Water Reclamation Plant into the North Shore Channel and North Branch of the Chicago River. The Metropolitan Water Reclamation District (MWRD) announced the new disinfection facility at a ribbon-cutting ceremony this morning. Sen. Dick Durbin acknowledged the Chicago River's murky history while praising the new disinfection effort.

“The city’s record when it comes to the Chicago River, the river that runs through the heart of downtown, has not been great,” Durbin said. “Today, we make a major step forward to reverse that trend and protect the valuable resource of the Chicago River.”

The O’Brien plant has the capacity to treat 450 million gallons of water per day and serves more than 1.3 million people within 143 square miles, making it the world’s largest ultraviolet disinfection facility, according to the MWRD.

The plant’s 896 ultraviolet lamps shine on treated water, turning it a shade of green that's reminiscent of the annual dyeing of the Chicago River. But those are germ-killing ultraviolet rays, not green dye.

The O'Brien plant will be the MWRD’s second water treatment facility to disinfect treated water. Last year, its Calumet facility began disinfecting treated water released into the Calumet River system by using chlorine to kill bacteria. A subsequent de-chlorination process is necessary to remove the chemical since it’s harmful to the environment.

The O’Brien plant’s ultraviolet disinfection approach is not only cheaper than using chlorine, but also safer, according to the MWRD’s director of engineering, Dr. Catherine O’Connor.

“With ultraviolet disinfection, the advantage is there are no possible disinfection byproducts or dissolved solids in the water,” O’Connor said.

The O'Brien plant first removes solids and sludge from human and industrial waste in the water before microbial processes break down organic matter. But until now, it did not disinfect the treated water as its final step.

That green hue is ultraviolet light, which kills or neutralizes any remaining bacteria or microorganisms in the water before it's released into the river. (MWRD)

Chicago is the last major city to disinfect treated water released into waterways. According to the Chicago Tribune, the MWRD spent more than $13 million to avoid adopting the measure. The path to disinfection didn’t start until 2011, when the Obama administration ordered a cleanup of the river that would make it suitable “for recreation in and on the water” in compliance with the Clean Water Act, the 1972 federal law outlining U.S. water standards.

In its press release announcing the O’Brien plant’s new disinfection process, the MWRD said the technology will “reduce the risk of health problems resulting from direct contact with the water while swimming or recreating on a waterway.”

But don’t go jumping in the river just yet. While O’Connor said the water of the Chicago River’s North Branch and North Shore Channel will now have a considerably “lower bacterial load,” it’s still not safe enough to swim in.

“We want [people] to exercise public health common sense, like not touching your hand to your mouth or washing your hands before you eat if you’ve made contact with the water," O’Connor said. 

“Any illness that would come from the water wouldn’t be terribly serious, but it would cause discomfort, like gastrointestinal distress.”

Part of the city's sanitation problem is due to the antiquated combined sewer system that continues to dump untreated raw sewage and stormwater into the river after heavy storms cause overflows. Water treatment plants are unable to handle the excess wastewater, so into the waterways it goes.

The MWRD hopes the McCook Reservoir, part of the city’s large-scale Deep Tunnel Project, will help alleviate this problem. After heavy rainfalls, the reservoir will accumulate excess raw sewage and wastewater from the O’Brien plant to be treated at a later time. The reservoir will be capable of holding 3.5 billion gallons of water after the completion of its first phase next year.

O’Connor said the MWRD decided to announce the disinfection process at the O’Brien plant after it was put into practice for a 60-day trial period.

Follow Evan Garcia on Twitter: @EvanRGarcia


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