Little water warriors

摘要

After the Sept. 11, 2001, attacks, water department managers became keenly aware of their facilities' vulnerability. Since then, they have put in place a range of measures, from physical features protecting buildings to tests that detect the presence of toxins in their water supply. Now, in large cities like New York City and more modest burgs like Altoona, Pa., tiny soldiers are lighting the way in the fight against terror.