Milwaukee disinfects its water to ensure safety for residents. Here's what you should know
Drinking water is much in the news these days, as PFAS contaminations continue to spread across the state and private well owners clash with big agriculture over phosphorous and nitrates that can get into drinking water.
But day to day, water systems take steps to ensure water flowing into homes, businesses and the environment is clean and safe from every-day contaminants.
Like water systems across the country and the world, Milwaukee Water Works disinfects its water to ensure that residents have a safe, clean source of water to rely on for cooking, drinking, bathing and whatever else they may need it for.
Here's a look at how public water is protected.
How do Wisconsin water systems disinfect their water?
Wisconsin water systems aren't actually requited to disinfect their water, but they do need to make sure that the microbial content is safe for human consumption, said Steve Elmore, the drinking and groundwater director for the Department of Natural Resources.
Water systems are required to test for things like E. coli and total coliform, and if those bacteria are over a certain threshold, the system has to take action to ensure customers don't get sick.
What about Milwaukee Water Works?
Milwaukee Water Works uses chlorine to disinfect water as it enters the treatment plant, but at the end of the process, before it's pumped out to customers, ammonia is added, and the reaction between the two chemicals creates chloramine, said Michelle Natarajan, the water quality manager.
"The purpose of that is it's a longer lasting disinfectant, so it's not quite as strong as the chlorine is, but now that the water has already been cleaned through various steps," she said.
"We just want to make sure that there is something in it so that when it reaches homeowners at the far edges of the city, that it's still safe and it will still help to fight any bacteria that could be accumulating in their internal plumbing."
Why is disinfection necessary?
Especially when water is pulled from surface sources, such as Lake Michigan, bacteria and other harmful elements have to be killed before the water can be sent out.
"It's very important that we use disinfectants to kill waterborne illnesses at the beginning of the process, and to keep somewhat of a residual of those products in the water to help kill anything that could be lurking in internal plumbing downstream," Natarajan said.
"So it's basically a very necessary public health measure. If we drank water straight from Lake Michigan, the population would not be as large as it is today. A lot of people would have died untimely deaths of giardia and cryptosporidium and all the other fun critters that are lurking in the lake."
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Is Lake Michigan water safe?
Yes.
Though no one should be drinking the water directly out of the lake, the water in Lake Michigan is relatively clean, Natarajan said.
"It does change over time, so we keep a close eye on it. But right now with all of the mussels in the bottom of the lake, they helped to filter out a lot of contaminants ahead of time so that we're starting with a relatively clean source of surface water," she said. "We still go through all the same treatment steps but we don't have to worry as much about a lot of the other issues that other communities do."
Are the disinfectants used in Wisconsin different from other states?
"It's pretty standard," Elmore said.
Chlorine and chloramine have been used since the early 1900s to ensure safe drinking water, he said, and it hasn't been detrimental.
Ozone is also used regularly to disinfect water typically when it enters the treatment plant, but it's not a long-acting disinfectant.
"At the the drinking water treatment plant, they can have ozone there that can kill the bacteria in the surface water coming in," Elmore said. "Some systems use Lake Michigan water, and as they pull in that lake Michigan water they can add ozone and that can kill bacteria."
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Are the chemicals monitored for safety in the water sent to homes?
Yes.
Elmore said that regular testing is required sometimes as often as two times a day, to ensure chlorine or chloramine levels aren't too high or too low.
"In a city the size of Madison or Milwaukee, they're taking bacteria tests every day, and when they do that, they also have to measure the chlorine level at that location where they're they're taking the bacteria sample," Elmore said. "And so we would know pretty soon after if there was too much chlorine in the in the system."
If a measurement came back with more than 4 parts per million of chlorine, the water system would have to take immediate action to bring levels down and notify customers.
Water systems also have to monitor for disinfection byproducts, which are created when certain compounds interact with chlorine. Byproducts can be harmful to human health, so systems must monitor water going out to residents to ensure its safe. Some systems opt to use only chloramine because it causes less byproduct creation, Elmore said.
Should I be concerned about chlorine or disinfection byproducts?
At the levels chlorine is used in Wisconsin water systems, residents shouldn't be worried.
"Chlorine is a is an effective disinfectant. It's something we've known for over 100 years can reduce disease. Before we added chlorine to drinking water there there was widespread occurrence of cholera in drinking water, and people would get sick from the cholera," Elmore said.
"And since then, we've been a much more healthy society because we disinfect our water with chlorine. It's one of those sort of necessary things. And we manage it appropriately, so it doesn't cause other problems."
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How did the cryptosporidium outbreak happen in the 1990s?
In 1993, a change in the recipe of additives in Milwaukee's drinking water led to an outbreak of gastrointestinal issues and deaths due to cryptosporidium, a type of bacteria capable of making humans very sick. Tens of thousands in the Milwaukee area suffered with chronic intestinal problems that disrupted schools and workplaces.
Excess cryptosporidium in the water was pulled into the treatment plant from Lake Michigan and wasn't killed off effectively before it was sent out into the homes of residents.
"They had changed some of their chemical processes in the treatment plant in Milwaukee, that caused that cryptosporidium not to be removed through the filtering treatment that they had there," Elmore said.
"It's an interesting piece of history because a whole line of regulations was (created) because of the outbreak in Milwaukee in 1993. That event really triggered a whole new set of regulations in our industry that have been used nation, you know are now in place nationwide and it really changed things in in other countries as well."
The city spent hundreds of millions of dollars implementing new processes — like treating the water entering the plant with ozone to kill off any lingering bacteria or viruses — as well as adding new monitoring systems, an auto-shutdown feature and extending the length of the intake pipe in Lake Michigan.
Now, the city rarely gets complaints about the taste or color of the water, marking a vast improvement in treatment.
What about private wells?
Private wells don't have the same level of regulation as public water systems, and the majority of wells don't have treatment systems unless homeowners buy and install them.
Homeowners who struggle with bacteria like E. coli may sometimes use chlorine to disinfect their own wells, but it's not a practice that's recommended. Elmore said that if they're having reoccurring issues, well owners should consider digging a new well, especially if their existing well is old or has failing infrastructure, such as a rusted or broken well casing.
"The regular chlorination of drinking water should really be left to professionals that know what they're doing and the operators of the public water system," he said. "It's not really something that that a private homeowner should be doing regularly."
Laura Schulte can be reached at leschulte@jrn.com and on X at @SchulteLaura.
This article originally appeared on Milwaukee Journal Sentinel: Here's what you should know about the disinfection of drinking water
