Science of Water : Concepts and Applications

20 The Science of Water: Concepts and Applications
MULTIPLE-BARRIER CONCEPT
On August 6, 1996, during the Safe Drinking Water Act Reauthorization signing ceremony, President
Bill Clinton stated:
“A fundamental promise we must make to our people is that the food they eat and the water they drink
are safe.”
No rational person could doubt the importance of the promise made in this statement.
The Safe Drinking Water Act (SWDA), passed in 1974 and amended in 1986 and (as stated
above) reauthorized in 1996, gives the United States Environmental Protection Agency (USEPA)
the authority to set drinking water standards. This document is important for many reasons, but is
even more important because it describes how the USEPA establishes these standards.
Drinking water standards are regulations that the USEPA sets to control the level of contaminants
in the nation’s drinking water. These standards are part of the SWDA’s “multiple-barrier
approach” to drinking water protection. The multiple-barrier approach includes the following
elements.
1. Assessing and protecting drinking water sources—Means doing everything possible
to prevent microbes and other contaminants from entering water supplies. Minimizing
human and animal activity around our watersheds is one part of this barrier.
2. Optimizing treatment processes—Provides a second barrier. This usually means fi ltering
and disinfecting the water. It also means making sure that the people who are responsible
for our water are properly trained and certifi ed and knowledgeable of the public health
issues involved.
3. Ensuring the integrity of distribution systems—Consists of maintaining the quality of
water as it moves through the system on its way to the customer’s tap.
4. Effecting correct cross-connection control procedures—Is a critical fourth element in the
barrier approach. It is critical because the greatest potential hazard in water distribution
systems is associated with cross-connections to nonpotable waters. There are many connections
between potable and nonpotable systems—every drain in a hospital constitutes
such a connection—but cross-connections are those through which backfl ow can occur
(Angele, 1974).
5. Continuous monitoring and testing of the water before it reaches the tap—Monitoring
water quality is a critical element in the barrier approach. It should include having specifi c
procedures to follow should potable water ever fail to meet quality standards.
With the involvement of the USEPA, local governments, drinking water utilities, and citizens, these
multiple barriers ensure that the tap water in the United States and territories is safe to drink. Simply,
in the multiple-barrier concept, we employ a holistic approach to water management that begins
at the source and continues with treatment, through disinfection and distribution.
The bottom line on the multiple-barrier approach to protecting the watershed is best summed
up in the following (Spellman, 2003):
Ideally, under the general concept of “quality in, means quality out,” a protected watershed ensures that
surface runoff and infl ow to the source waters occur within a pristine environment.
WATERSHED MANAGEMENT
Water regulates population growth, infl uences world health and living conditions, and determines
biodiversity. For thousands of years, people have tried to control the fl ow and quality of water. Water