Construction begins for chemical-free treatment

The city of Superior is laying the foundation for a chemical-free way to disinfect wastewater.

RJS Construction has started to build the footings for the foundation of a 38-foot by 62-foot building that will eliminate chlorine and sulfur dioxide from the wastewater treatment process as the city converts the disinfection process to ultraviolet disinfection.

Ultraviolet radiation works by altering bacteria at a genetic level, “deactivating them” so they can’t multiply.

Treated wastewater will travel through channels in the new building past ultraviolet light banks, said Environmental Services Engineer Mark Unger, who is overseeing the construction project.

The current system, which uses chlorine to disinfect treated wastewater and requires sulfur dioxide to eliminate the chlorine before the water is released into the environment, is aging and needed to be replaced, said Steve Roberts, engineering manager with the city’s Division of Environmental Services. He said when the city began planning to replace the system, the goal was to find a disinfection system that would allow the city to take advantage of grant funding.

Nearly $1.4 million of the $4.9 million project, which includes construction of another facility to help the treatment plant on East First Street meet regulations for balancing the pH level of the water to minimize the amount of ammonia introduced into the bay, comes from federal and state grants.

By changing the system to a UV disinfection system, the city would eliminate use of 11 tons of chlorine in the treatment process, which can affect organic matter in the water.

The city’s Wastewater Treatment Facility uses elemental chlorine to disinfect treated wastewater.

While chlorine is an effective method for disinfection, it also poses a risk to public health.

According to the Centers for Disease Control and Prevention, when liquid chlorine is released, it quickly turns into a poisonous, yellowish-green gas that settles near the ground and spreads rapidly; the extent of poisoning depends on how a person is exposed, the amount of exposure and the length of time the exposure exists.

Chlorine is detectable at 1 part per million, can cause vomiting and coughing at 30 ppm, lung damage at 60 ppm and death at 1,000 ppm, creating a risk for workers and citizens. It also releases chlorine into the Lake Superior watershed.

It will also eliminate the release of a carcinogenic byproduct — trihalomethanes — that results from chemical disinfection of water into the environment, Roberts said.

The U.S. Environmental Protection Agency only allows the release of trihalomethanes at 80 parts per billion annually; however, the new one-step process would eliminate the by-product completely.

The project has been in planning stages for more than two years and construction is expected to be substantially complete by mid-November.

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