When the epidemic caused schools to use remote learning, Rebecca Bushway, a science teacher in Washington, offered her pupils an ambitious task: design and build a low-cost lead filter that repairs faucets while also removing the hazardous metal. Using 3D printing and high-school chemistry, the team has created a functioning prototype: a three-inch (7.5-centimeter) tall filter housing made of biodegradable plastic that they plan to sell for $1 each.
‘The science is simple,’ Bushway told AFP during a recent visit to the Barrie Middle and Upper School in suburban Maryland, where she showed the filter. Bushway has presented the prototype at four conferences, including the famous American Chemical Society’s spring meeting, and intends to publish a manuscript in a peer-reviewed publication. Up to ten million US houses still get their water through lead pipes, and kid exposure is especially dangerous.
The metal, which bypasses a critical bodily defence known as the blood-brain barrier, can result in persistent cognitive impairment and contribute to psychological issues that worsen long-term poverty cycles. A significant pollution problem discovered in Flint, Michigan in 2014 is likely the most well-known recent tragedy, but lead poisoning is ubiquitous and disproportionately affects African Americans and other minorities, according to Barrie team member Nia Frederick.
The dangers of lead poisoning have been recognised for decades, but the lead industry’s lobbying prevented serious action until recently. President Joe Biden’s government has offered billions of dollars from an infrastructure plan to pay the removal of all lead pipes around the country over the next few years, but people need solutions immediately.
A devious ruse
Bushway’s concept was to exploit the same chemical process used to rehabilitate polluted soil: exposing dissolved lead to calcium phosphate powder generates solid lead phosphate, which stays inside the filter along with safe free calcium. The filter has a cunning trick up its sleeve: behind the calcium phosphate is a reservoir of a chemical called potassium iodide.
When the calcium phosphate is depleted, the dissolved lead reacts with potassium iodide, making the water yellow – an indication that the filter needs to be replaced. Wathon Maung, a student, spent months creating the home on 3D printing software and went through several prototypes. Calcium phosphate was aggregating within the filter, delaying the process. However, Maung discovered that by integrating hexagonal bevels, he could secure the flow of water and prevent clumping. The result is a flow rate of two gallons (nine litres) per minute, which is the usual rate at which water runs out of a tap.
The Barrie team would then like to integrate a spectrophotometer, which would detect yellowing of the water before it is perceptible to the human eye and turn on a little LED warning signal. A chemical engineer who was not involved in the work, Paul Frail, said the group ‘deserves an unbelievable lot of credit’ for integrating general chemistry ideas with 3D printing to build a unique product.
However, he stressed that the filter would need to be tested further using ion chromatography machines, which are often found at universities or research labs, as well as market research to establish demand. Bushway is sure that a market exists. Reverse osmosis devices that provide the same function cost hundreds to thousands of dollars, but carbon block filters costing roughly $20 must be updated every few months, which is more often than her group’s filter.