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Sunday’s alert about a chemical spill in the Delaware River sent Philly residents rushing to the grocery store to stock up on bottled water.
Many had another idea: Can I skip the Acme and just run my tap water through the filter in my pitcher?
More specifically, will a Brita or Pur filter pull the materials from the Bucks County latex plant — identified by officials as butyl acrylate, ethyl acrylate and methyl methacrylate — out of my drinking water?
Philadelphia officials said Tuesday morning that all water in Philly’s system is confirmed safe to drink directly from the tap, and that current testing guarantees it’ll be fine through at least 11:59 p.m. Wednesday.
They also said the chemicals might slide down the Delaware without ever getting inside the riverside treatment plant that feeds about half the city. No “plumes” were spotted near the Baxter Drinking Water Treatment plant that feeds about half the city’s pipes, and infrared spectroscopy and gas chromatography testing has continued to come back negative.
Even so, the early confusion and the uncertainty of when the all-clear will come has many people wondering whether filtration could give that extra layer of certainty tap water is safe.
Here’s what we’ve found.
Regular water filters aren’t designed to remove these chemicals (but that doesn’t mean they don’t)
According to Brita, the answer to residents’ question about whether it’ll remove the hazards is no.
“Our filters don’t reduce butyl acrylate,” the company wrote on Twitter, in response to a question from Mike Roman, a former Trump administration staffer from Philadelphia.
That response is understandable because this particular chemical isn’t usually in drinking water, noted retired Penn State environmental engineering professor Fred Cannon.
“What they’re saying is that their system wasn’t designed for absorbing butyl acrylate from the water,” Cannon told Billy Penn, advising people to follow the manufacturer’s advice. “If the people that make them are saying that, you have to take their word for it.”
At the same time, after looking at the chemical structure of butyl acrylate, he thought it might well be attracted to activated carbon and caught by a filter.
“My experience is, that kind of compound has a moderate absorption capacity on things like Brita filters,” said Cannon, who has researched activated carbon technologies for American Water Co. and designed municipal water systems in California and Colorado.
Butyl acrylate hasn’t been used in home filter testing, in part because it almost never shows up in drinking water
The companies that make pitchers don’t know how their products would handle many substances, said Stephanie Wein, clean water and conservation advocate at advocacy nonprofit PennEnvironment.
“Those filters aren’t tested for the wide variety of specific industrial chemicals that could enter our waterways, but just a narrow band of common contaminants,” Wein said.
That’s because most of these substances, such as the latex components in this weekend’s spill from the Trinseo Altuglas plant in Bristol Township, almost never reach kitchen taps.
“It would be unlikely to find a specific pitcher that you could go run out and buy at Walmart or Target that would say, ‘Oh, we remove ethyl acrylate and butyl acrylate,’ because those are not things you typically have in your water,” said Beth Younts, an educator at Penn State Extension in Philadelphia who interprets water quality tests for residents.
Carbon filters work because they have a huge surface area
The filters used in pitchers for home use are micro versions of the much larger beds of activated carbon found in some water treatment plants, said Cannon, the retired engineering prof.
The carbon — made of burned wood or other materials — works by attracting particles of many substances to its relatively huge surface area. A handful of activated carbon has a surface area roughly equivalent to a football field, Cannon said, allowing it to hold a large amount of contaminants.
Surfaces of the carbon in a filter will eventually “fill up” with substances in the water, which is why it’s important to periodically install new filters, he added.
The effectiveness of a particular filter design in attracting a specific substance depends on several factors, per Cannon, including its chemical makeup, the size of the carbon particles, and how quickly the water moves over the filter.
Butyl acrylate was not listed in a reference guide of some 100 chemicals that have been tested with activated carbon, he said.
Water treatment facilities have multiple ways to keep contaminated water from reaching kitchen sinks
Treatment facilities have several layers of protection to keep hazardous chemicals from reaching their customers, Cannon said.
Water companies and agencies like the Philadelphia Water Department constantly test for quality and publish their results, and are required to satisfy contaminant limits set by the U.S. Environmental Protection Agency.
Treatment plants typically use sand filters, which can capture latex compounds, Cannon said, and flocculation, where materials are added to water to make contaminants clump together for easier removal. Some plants also flow water over beds of activated carbon to pull out additional chemicals.
It is not clear if Philadelphia Water uses carbon; last week, in connection to an unrelated EPA announcement about hazardous PFAS chemicals, the utility said it was considering upgrading its filtration methods.