91av

Factories making explosives and rocket propellants can contaminate
groundwater with perchlorates, recently identified as presenting health risks,
says Calgon Carbon of Pittsburg (GB 2 340 113). Bacteria can break down the
chemicals, but this takes time. Calgon’s quicker answer is to pass the
contaminated water through an ion-attracting resin—as used in some water
softeners—to suck up any negatively charged perchlorate and nitrate ions.
Brine is then pumped through the exchanger, washing any explosive residue into a
chamber where bacteria can break them down.