High schoolers develop an inexpensive filter to remove lead from tap water

The next generation of scientists and inventors are finding ways to address society's problems. A group of high school students and their instructor have come up with a solution to the problem of lead in drinking water. Theirs is the only one currently on the market that includes a bio-degradable plastic cartridge and indicates when it is used up by turning the tap water yellow.

The results will be presented at the spring meeting of the American Chemical Society.

A few years ago, I saw a video of a woman in Michigan turn on her tap water, and it came out brown, says Rebecca Bushway, who is the project's principal investigator. She is presenting the work at the meeting and that made me think that it would be nice to have a water filter that could tell you if the water has lead in it.

Millions of homes in low-income communities still get their drinking water from lead-laden pipes. If the chemistry of the water isn't ideal, or it flows quickly because of high demand, pipes can be damaged. When the corroding material contains lead, the toxic metal can get into the water and cause a dark discoloration and sometimes visible particles.

Until old pipes can be replaced with lead-free versions, filters can help remove or reduce this pollutant from tap water. The high cost and large size of lead filters can be barriers. None of them indicate that the water could pose an immediate health risk, and few of them indicate that they should be changed.

Bushway wondered aloud to her upper-level high school chemistry class if there was a little filter similar to the ones that are made for camping to purify water, that they could make from inexpensive components. When the students were excited about the idea, they started thinking about the project in 2020 when they couldn't attend class because of COVID-19 restrictions. The team met virtually and discussed designs for an attachment to screw a filter onto a sink's faucet. When they returned to the classroom in the spring semester of 2021, they 3D printed the attachment and the filter housing. The final step was to fill the cartridges with a mixture.

Lead is dissolved in water to form calciumphosphate and free calcium. Bushway explains that the calcium ends up in the water and the lead stays in the filter. The nylon screen on the bottom of the unit is where lead is trapped. Once the reaction capacity of the calciumphosphate is reached, dissolved lead reacts with the iodide in the water, which causes the water to yellow.

The chemistry is straightforward, but crafting the water purification system has been more difficult. As the surface area decreases, the reaction rate between it and calcium phosphate will go down. The lead student engineer incorporated hexagonal bevels inside the filter, which will make the water spiral as it goes through and keep the powder from clumping.

The students will add a tiny spectrophotometer to the bottom of the filter to measure the amount of water in it. As soon as the detector identifies the yellow color of the lead, the indicator light will turn on. Bushway says that this will show the presence of lead in the water.

Bushway thinks the team is on their way to making and selling filters for less than $1 each. The material used in the housings could help reduce the environmental impact of the filter.

Bushway says that the experience has shown students that they can make a difference and that there are problems that they can fix with science.

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