When the drinking water in a major city has even the slightest taste and odour residents will often phone and complain, despite the fact that these incidences are typically controlled rapidly by the water treatment plant. Most cities in North America have access to good water sources, which are highly suitable for the production of drinking water. These water sources are commonly from large lakes or rivers, which frequently drain non-contaminated watersheds, such as the Rocky Mountains from which many cities in Alberta, B.C., and Saskatchewan get their water. In addition to having good quality water to treat, major cities have biologists, microbiologists and engineers who test and evaluate the treatment processes on a daily basis. Experiments are run and treatment optimized.
Cities frequently treat their water to far higher standards than provincial or federal guidelines.
The Cryptosporidium parasite was distributed in the City of Milwaukee's drinking water in 1993. But, the traditional indicators for microbially unsafe drinking water, total coliforms, were absent in Milwaukee's water. The cost of waterborne diseases to a society can therefore be staggering. The Milwaukee incidence is so significant that there is likely not one large water treatment plant anywhere in the world that does not know what potential costs can be associated with distributing unsafe drinking water. Some of the toughest drinking water quality standards in the world are enforced the U.S. Environmental Protection Agency.