One welcome development is that municipal treatment plants have started to go beyond basic filtering and disinfecting, which can allow chemicals, bacteria and pharmaceuticals to remain in the water supply. Cincinnati and Louisville use activated carbon filters and ultraviolet light disinfection to make water cleaner. San Diego has built a pilot plant that can turn wastewater directly into superclean drinking water [see “Bottoms Up,” on page 68]. Regulators should allow municipalities to bring such plants online.