MIT has hopes for ‘selective, economical’ shockwave water purification

Massachusetts Institute of Technology (MIT) researchers say they have a new application for shock electrodialysis when it comes to the “continuous, selective, and economical” removal of lead from water.

The MIT engineers say the new system is the latest in a series of applications based on initial findings six years ago by members of the same research team. The technology was initially developed for desalination of seawater or brackish water, and later adapted for removing radioactive compounds from the cooling water of nuclear power plants, according to the research team.

The team describes the process — yet to be scaled up from the laboratory level — in a new research paper. That paper states that an electric field is used to produce a shockwave inside an electrically charged porous material carrying contaminated water. The shockwave then spreads as the voltage increases, leaving behind a zone where the metal ions are depleted, and separating the feed stream into a brine and a fresh stream.

The process results in a 95% reduction of lead (to safe levels below 1 ppb) from the outgoing fresh stream without compromising small amounts of elements such as sodium and magnesium that are essential for healthy drinking water.

In principle, “this makes the process much cheaper,” MIT professor of chemical engineering, Martin Bazant, told MIT News. “Because the electrical energy that you’re putting in to do the separation is really going after the high-value target, which is the lead. You’re not wasting a lot of energy removing the sodium.” Because the lead is present at such low concentration, “there’s not a lot of current involved in removing those ions, so this can be a very cost-effective way,” added Bazant.

The biggest challenge in trying to remove lead is that it is generally present in tiny concentrations exceeded by other elements or compounds. For example, sodium is typically present in drinking water at a concentration of tens of parts per million, whereas lead can be highly toxic at just a few parts per billion.

The MIT team believes that the experimental and theoretical results could be used to guide the development of low-cost, point-of-use systems for continuous removal of lead from municipal water.

The MIT research team received support from a MathWorks Engineering Fellowship and a fellowship awarded by MIT’s Abdul Latif Jameel Water and Food Systems Lab, funded by Xylem Inc.