Table A. Progress in Filtration Table B. Progress in Disinfection
of that regulation.2
Amendments to the federal regulations were adopted in 1925,
1942 and 1946, adding limits for inorganic and physical constituents.
In 1962, the most significant update to federal regulations applied
officially to interstate carriers (about 700 water utilities) and covered
dozens of physical, inorganic chemical, organic chemical and microbiological
constituents. Many states adopted the federal standards
by reference and made compliance mandatory in their jurisdictions.
In addition, many individual water utilities complied voluntarily.
Run Up to Passage of the SDWA
In 1974, the water industry and the general public was shaken
by a series of events and subsequent press coverage that drew attention
to drinking water legislation that had been stalled in Congress.
Consumer Reports carried articles in June, July and August
entitled, “Is Our Water Safe to Drink?” On November 7, 1974, the
Environmental Defense Fund released a study purporting to show
a link between lower Mississippi River water supplies and cancer
death rates.3 The next day, the U.S. Environmental Protection Agency
(USEPA) announced it had discovered 66 organic chemicals in
New Orleans’ drinking water and that it would undertake an 80-city
survey to investigate organic chemical contamination. The National
Organics Reconnaissance Survey (NORS) ultimately looked for
trihalomethanes and other volatile organic chemicals, primarily in
treated surface water. The December 1974 issue of Journal AWWA
carried an article by USEPA scientists Bellar, Lichtenberg and Kroner
that showed trihalomethanes were produced when natural organic
material in source waters reacted with chlorine used for disinfection
purposes.4 On December 5, 1974, a CBS news magazine program
broadcast the special, “Caution, Drinking Water May be Dangerous
for Your Health” and on December 8, the New York Times published
a long article, “What’s in the Water We Drink?”6 Given this highly
charged environment, it is not surprising that Congress passed the
SDWA on December 3, 1974, and President Gerald Ford signed the
bill into law a few days later.
Progress Made Under the SDWA
One measure of the success of the SDWA is in the expanded number
of regulated contaminants, which began with 22 in 1976 and
ramped up to 90 by 2000. The real test of the efficacy of the regulations,
however, is how waterborne disease has been controlled. Because
contemporary rates of disease and death due to drinking water
are far less than those at the turn of the twentieth century, we can’t
measure progress in those terms. What we can measure is the capital
investments water utilities have made to dramatically improve water
quality and safety in their treatment plants and distribution systems.
Because no survey exists that shows progress from 1974 to the present,
what I present here is anecdotal evidence. The examples cited
are from large cities, but progress has been made at all levels of U.S.
public water systems, including the very small system that rounds out
It was clearly a goal of the SDWA and the Surface Water Treatment
Rule to drastically curtail or eliminate unfiltered water supplies. Table
A shows that many large cities have installed filtration or have
ramped up their disinfection to provide barriers against pathogens
such as Cryptosporidium. Although in 1974, it would have been difficult
to convince anyone that advanced disinfection processes would
become so widely used, improvements in disinfection have occurred
for all water utilities in some manner (Table B). Our improved understanding
of the pathogens present in surface waters is part of the
reason for these advances (see Figure 1), as is the need to control
disinfection byproducts regulated under the SDWA.
In 1985, the Metropolitan Water District of Southern California
charted a course to replace free chlorine with ozone as the primary
disinfectant in its five large treatment plants. Hydrogen peroxide
feed systems were included in the upgrades to give the plants the
option to produce PEROXONE to control taste and odor problems.
Since then, ozone installations have been completed at the Mills,
Jensen, Skinner and Diemer plants and more are planned at the
Weymouth facility over the next few years. The ozone generation
capacity for these plants will ultimately be 2,640 mgd, which is the
largest ozone installed capacity for any water utility in the world.
Pathogen Contamination and Response by Utilities
Figure 1 shows how our original concerns with bacteria were
complicated with the discovery of viral contamination of some water
Figure 1. Progress in Disinfection