ABSTRACT
Even when chlorinated or otherwise treated, community water supplies in devel oping countries often do not meet standards applied in many developed countries. Even chlorination does not provide protection against parasites such as Giardia lamblia, Cryptosporidium, or Cyclospora. Water treatment plant sand filtration is required to remove these pathogens. Even if operations at the treatment plant meet international standards, contamination can occur during distribution. Unbe knownst to water and health authorities cross-connections may exist between the potable and nonpotable supplies. Back-siphonage can occur, bringing polluted water into the main supply when water outlets are submersed and negative line pressure occurs following shutting off the water supply or excessive nearby uses. Power failures are not uncommon in some developing countries, and periodically power is cut off for load shedding. Pump failure can shut down water distribution, other than that from higher elevations than the supply, and this situation can be conducive to back-siphonage where submersed inlets exist. In more rural settings, the potential for occurrence of all these situations is even higher, and the water treatment may be inadequate, or there may be no treatment at all. Furthermore, the water may come from unprotected sources close to sites of fecal pollution. Addi tional hazards can come from ice in drinks and by brushing teeth with potentially contaminated water.
