There are approximately 53,000 water utilities in the United States. These include public systems, private systems, and cooperatives and these utilities serve 85 percent of our Nation's population. As a group, they provide some of the safest drinking water in the world. Probably the principal reason is that for over 100 years, most U. S. water utilities have chlorinated the water they deliver. Chlorine disinfectants destroy the organisms that cause diseases such as cholera, typhoid and dysentery among others. Still, there are some problems. Can our drinking water be made even safer?

My last several columns dealt with our water resources infrastructure and so does this column with a different slant. An article in the Science section of the August 27 issue of the New York Times prompted me to write this column which primarily summarizes the information contained in the article.

The article states that many individual cases of waterborne diseases still occur (in the U. S.) and related hospitalization costs approach $1 billion each year. Microbes such as mycobacteria can survive chlorination and cause infections particularly in elderly people or persons whose immune systems are compromised. In 2007 and 2008, the last two years for which data are available from the Center for Disease Control, 164 waterborne disease outbreaks occurred, nearly all from the parasite Cryptosporidium. In response, many utilities now are treating their produced water with ultraviolet light that inactivates Cryptosporidium and some other organisms that are chlorine resistant.

In spite of these statistics, the fact is that waterborne diseases affect far, far less than one percent of the U. S. population. Nevertheless, researchers are studying ways to decrease further the number of waterborne illnesses or infections.

Recent research has determined that in many cities and towns, the principal problem is not with the water supply itself but with the delivery infrastructure. Water delivery infrastructure in many cities and towns is very old, very complex, and in some cases not completely known to the current water utility employees. Researchers led by Norman Pace of the University of Colorado are studying the ecology of several of these old delivery systems and are mapping the ecological niches in them where certain chlorine-resistant microbes may hang out. What the researchers have discovered is that in some cases, the water from the faucet may be markedly different from the water that leaves the treatment facility. Dr. Pace said, "The ecology is the distribution system."

The research indicates that one reason for this is that some benign and a few potentially harmful bacteria species survive chlorination and may persist in older distribution systems in something called biofilms. Biofilms are a sticky polymer-like substance made up of DNA, proteins and carbohydrates that form on and cling to the inside of pipes. Evidence exists that in some cases these biofilms may break loose and carry bacteria throughout the distribution system.

Still, our utility-supplied water is safe. But the work of the researchers in the Pace program together with greater attention to the aging distribution systems can make it even safer. I strongly support this research and urge cities and towns to monitor bacterial concentrations carefully and to consider upgrades to their distribution systems. Even safer water should be the goal of every utility.