The city of Superior is looking to eliminate nearly 11 tons of chlorine from its wastewater treatment process.
The council Tuesday approved a proposal by Strand Associates Inc., to provide preliminary engineering for ultraviolet disinfection.
"What we're using right now is elemental chlorine," said John Shamoa, operations manager at the Superior Wastewater Treatment Plant. "That's a little bit of a different than you use in a swimming pool but with the same effect. What the basic change would be is that elemental chlorine would be something that wouldn't be used anymore."
Instead, he said, ultraviolet radiation would disable the bacteria in the treatment process so it would no longer be a threat.
Elemental chlorine gas is pressurized and cooled to turn it into a liquid for transport and kills bacteria in drinking water, swimming pools and wastewater treatment.
ADVERTISEMENT
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.
According to a memo from Assistant Public Works Director Jeff Goetzman and Engineering Manager Steve Roberts 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.
The current disinfection process creates potential safety hazards for workers and citizens, Shamoa said. The process also results in the chlorine released into the Lake Superior watershed, he said.
By going to ultraviolet radiation treatment, Shamoa said the city would eliminate the need for elemental chlorine.
"We might still need to use, occasionally, a strong bleach solution in our operations but that would be much safer than using the liquid or gaseous chlorine."
Ultraviolet radiation works by altering bacteria at a genetic level, "deactivating them" so they can't multiply, Shamoa said.
The system works with phototubes and the water runs through them and is treated with ultraviolet radiation, said Dan Romans, environmental services administrator for the city.
"It doesn't have the effect of changing any kind of organic ... that may be in the water where chlorine has the potential to chlorinate organics," Romans said. "By using UV, we eliminate that potential as well ... When we move to technology like this that has been proven in industry for 15-20 years, what we're trying to do is look to the future and make sure we're not adding anything to the environment if we can avoid that."
ADVERTISEMENT
Funding for the engineering project will be paid through a Section 154 grant, a federal grant program created by U.S. Rep. Dave Obey, D-Wausau, to provide funding for infrastructure projects in the four northernmost counties of Wisconsin to protect the Lake Superior watershed.
