Is this water safe to drink?

The FESS Operation Department works to ensure that the drinking water at Fermilab is safe.

It’s easy to take water for granted. We expect clean, clear and safe water whenever we turn on the tap. But whether the water comes from deep underground or a surface water source, getting it to you involves a lot of engineering and science. “Raw” water has to be treated using filtration and chemicals, then pumped to consumers through a system of mains over a broad area. The quality of water that is delivered to the end user depends on many variables—the quality of the source, the degree of treatment and the condition of the piping systems all the way from treatment to the faucet.

Water quality questions related to Fermilab’s distribution system arise on occasion. Obviously, the most important quality of drinking water is its safety. When we think of “bad” water, we’re usually worried about microorganisms that make us sick. Fermilab purchases water from the City of Warrenville, and like most public water supplies, the water is chlorinated. Free chlorine in the water quickly gets “used up” through biological and chemical reactions and becomes “combined” chlorine. While chlorine in the free state is a powerful disinfectant, maintaining a sufficient residual concentration of combined chlorine is just as effective at keeping drinking water safe.

The safety of our drinking water is virtually assured, but other qualities, such as color, odor and taste can deteriorate. These characteristics are recognized by regulatory agencies as “secondary characteristics” and are not subject to enforceable standards. Most of our water mains and pipes inside buildings are decades old and subject to corrosion and failure. Old systems can harbor pockets of microorganisms such as sulfate-reducing bacteria (SRB), which don’t cause disease, but which convert sulfates in the water to hydrogen sulfide, which imparts a rotten-egg odor. As deposits of SRBs are killed off by the disinfectant properties of the water, they can slough off and discolor the water. The result is water that is still safe, but not very appealing.

The FESS Operations Department addresses specific water quality issues as they occur by studying the existing system to better understand the causes of problems and to enable us to make improvements. FESS engineers use a CAD model to estimate flow rates and water residence times as a function of building consumption and pipe sizes. The ultimate answer is to replace old, deteriorated iron pipe with copper or plastic pipe, and we are making progress on this goal, but it is a big job. The immediate goal is to continue to provide safe water for everyone at Fermilab.

Rod Walton