US high school students design low-cost filter to remove lead from water

When the pandemic forced schools into distance learning, Washington-area science teacher Rebecca Bushway gave her students an ambitious task: to design and build a low-cost lead filter that attaches to faucets and eliminates toxic metal.

Using 3D printing and high school level chemistry, the team now has a working prototype – a three-inch (7.5 centimeter) high filter housing made of biodegradable plastic, which they hope to eventually put on the market for $1 each.

“The science is simple,” Bushway told AFP during a recent visit to Barrie Middle and Upper School in suburban Maryland, where she demonstrated the filter in action.

“I thought, ‘We have these 3D printers. How about we do something like this?'”

Bushway has presented the prototype at four conferences, including the prestigious American Chemistry Society Spring Meeting, and plans to move forward with an article in a peer-reviewed journal.

Up to 10 million American homes still receive water through lead pipes, with exposure particularly harmful during childhood.

The metal, which evades a key body defense known as the blood-brain barrier, can cause permanent loss of cognitive abilities and contribute to psychological problems that compound persistent cycles of poverty.

A serious contamination problem discovered in Flint, Michigan in 2014 is perhaps the most famous recent disaster – but lead poisoning is widespread and disproportionately affects African Americans and other minorities, a explained Nia Frederick, a member of the Barrie team.

“And I think that’s something we can help with,” she said.

The harms of lead poisoning have been known for decades, but lead industry lobbying prevented meaningful action until recent decades.

President Joe Biden’s administration has promised billions of dollars of infrastructure legislation to fund the removal of all lead pipes in the country over the next few years – but until that happens, people need solutions now.

A clever trick

Bushway’s idea was to use the same chemical reaction used to restore contaminated soil: exposing dissolved lead to calcium phosphate powder produces a solid lead phosphate that stays inside the filter, as well as harmless free calcium.

The filter has a nifty trick up its sleeve: underneath the calcium phosphate is a reservoir of a chemical called potassium iodide.

When the calcium phosphate runs out, the dissolved lead reacts with the potassium iodide, turning the water yellow – a sign that it’s time to replace the filter.

Student Wathon Maung spent months designing the case on 3D printing software, going through numerous prototypes.

“What’s great is that it’s kind of a little puzzle that I had to solve,” he said.

Calcium phosphate clumped inside the filter, slowing the reaction. But Maung discovered that by incorporating hexagonal bevels, he could ensure water flow and prevent clumping.

The result is a flow rate of two gallons (nine liters) per minute, the normal rate at which water flows from a faucet.

Next, the Barrie team would like to incorporate an instrument called a spectrophotometer that will detect yellowing in the water before it’s even visible to the human eye, then turn on a small LED warning light.

Paul Frail, a chemical engineer who was not involved in the work, said the group “deserves incredible credit” for their work, combining general chemistry concepts with 3D printing to design a new product.

He added, however, that the filter would require additional testing with ion chromatography instruments typically available at universities or research labs, as well as market research to determine demand.

Bushway is convinced there is a niche. Reverse osmosis systems that perform the same role cost hundreds to thousands of dollars, while carbon block filters available for around $20 need to be replaced every few months, which is more often than the carbon block filter. his group.

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