|
MAY 1-7 IS NATIONAL DRINKING WATER WEEK, & FOR THAT BE GRATEFUL!
< back to articles
May 1-7, 1994, has been designated by the American Water Works Association (representing municipal water supply agencies) as "National Drinking Water Week." This is a good time to reflect upon what everyone takes for granted, but which is a very complicated process of bringing safe drinking water into millions of homes and commercial buildings.
Municipal water supplies undergo elaborate testing and treatment involving dozens of procedures. If we were to follow a specific unit of water from the time it enters an intake pipe until it exits the purification plant, we would find it an all-day journey of eight hours or close to it.
The biggest municipal systems serving cities such as New York and Chicago require pipes measuring as much as 15 feet in diameter to handle volumes of water ranging upwards of a billion-billion-gallons a day. All this fresh water typically comes from massive man-made reservoirs (in the case of Southern California and New York) or even more massive natural reservoirs such as the Great Lakes. Huge pumps lift thousands of gallons at a time dozens of feet to different treatment stations.
First, chemicals are added in a rapid mixing procedure. There is chlorine for sterilization, aluminum sulfate or alum and polymer for coagulation, lime and caustic soda to prevent corrosion in the distribution mains, activated carbon to remove taste and odors, and fluoride to prevent dental cavities in children's teeth.
(There was much controversy when fluoride was first introduced into water supplies back in the 1950s. Some people even viewed it as part of a Communist plot. However, study after study has borne out that the procedure has done what it was supposed to do in dramatically reducing tooth decay. Likewise, there is little evidence of any harmful side effects.)
Following the rapid mix of chemicals into the water, it typically passes into mixing and settling basins for a leisurely bout of flocculating. No, there is nothing obscene about this. The flocculation process involves the settling of impurities after slow mixing with alum or some other flocculent. Around 90% of the solids typically are taken out of the water in the settling basins - some of which have capacities ranging into millions of gallons.
From the settling basins water usually travels to a large sedimentation tank to complete the clarification (making water clear and solid-free) process. From there the water goes through sand filters for final "polishing." Then the water receives a final dose of chlorine and, added in recent years, frequently a phosphate-based chemical to inhibit lead leaching from the distribution piping system. Safe, pure (except for trace impurities) water then passes into a variety of pumping stations for distribution throughout a municipality.
Along the way microbiologists and chemists monitor thousands of water samples for both organic and inorganic contaminants ranging from fungi to asbestos fibers to radioactivity. These monitors employ the most sophisticated scientific tools such as scanning electron microscopes and x-ray analyzers. They seldom find worrisome levels of anything, but when they do there are systems in place to quickly notify the EPA and other relevant government agencies, which may then issue warnings or take other remedial action.
Last year's outbreak of intestinal illness in Milwaukee - along with a lesser episode in the nearby city of Racine - are among rare cases when the treatment process broke down. Most water-borne ailments in modern America can be traced to organisms or substances that enter the water supply after it passes through the treatment plant. They get introduced either in the municipal distribution piping, in the building mains or within the building's piping system itself.
If there is a weak link in this system, it is the distribution piping. Some of our older cities still rely upon some old wooden pipes that are centuries old. The Associated General Contractors of America has estimated it would take upwards of $20 billion worth of infrastructure improvements to bring our nation's water supply and sewage treatment systems up to where they should be.
Nonetheless, even in its present state, America's water systems are the envy of most of the world. This is something to contemplate and be proud of during National Drinking Water Week. It is not something to take for granted.
|
