22-7 Drinking Water Quality

How Is Urban Drinking Water Purified? The High-Tech Centralized Approach

Areas that depend on surface water for drinking usually store it in a reservoir for several days. This improves taste and clarity by increasing dissolved oxygen content and allowing suspended matter to settle. Next, the water is pumped to a purification plant where it is filtered as needed and chlorinated to meet government drinking water standards. In areas with very pure groundwater sources, little treatment except disinfection is necessary

How Can We Purify Rural Drinking Water in Developing Countries? The Low-Tech, Decentralized Approach

Ways to purify drinking water can be simple. In tropical countries without centralized water treatment systems, the WHO is urging people to purify drinking water by exposing a clear plastic bottle filled with contaminated water to intense sunlight. In the strong sunlight found in most tropical countries, heat and the sun’s UV rays can kill infectious microbes in as little as three hours. Painting one side of the bottle black can improve heat absorption in this simple solar disinfection method. Where it has been used, incidences of dangerous child- hood diarrhea have decreased by 30–40%.

Another simple method involves adding a small amount of a chlorine-disinfectant solution to plastic or clay water-storage vessels with a narrow mouth and cap and a spigot—similar to what campers frequently use. The storage vessel design helps protect the disinfected water from additional bacterial contamination

How Well Is Drinking Water Quality Protected by Law?

About 54 countries, most of them in North America and Europe, have standards for safe drinking water. In Canada, drinking water is regulated by all three levels of government. The federal and provincial governments establish guidelines and monitor research concerning water safety. Municipal governments run the day-to-day operations of publicly owned water utilities. The federal and provincial guidelines set forth acceptable limits for a wide range of chemicals that might be found in drinking water. The guidelines are not legally binding, but most water utilities in Canada abide by them. Privately owned wells often do not meet drinking water standards for two reasons. One is that it costs at least $1 000 to test each well and owners would need to retest their water every few years. The other is that some homeowners oppose mandatory testing and compliance.

Is Bottled Water the Answer? Solution or Expensive Rip-off?

Despite some problems, experts say North America has some of the world’s cleanest drinking water. Yet many of us worry about getting sick from tap water contaminants, and many drink bottled water or install expensive water purification systems. Studies reveal that in North America bottled water is 240 to 10 000 times more expensive than tap water. In addition, about one-fourth of it is tap water, bac- teria contaminate about one-third of it, and various potentially harmful organic chemicals contaminate about one-fifth of it. On the other hand, some countries must rely on bottled water because some of their tap water is too polluted to drink. Use of bottled water can also cause some environmental problems.