Civil Engineering Reference
In-Depth Information
report investigating the water quality of the Mississippi River revealed a total of 36
organic compounds found in the treated drinking water in New Orleans. This alarmed
not only the water utilities but also the public, environmental activists, and Congress.
11
Although health effects of these compounds were largely unknown, these ''new''
discoveries, in addition to the results of the 1969 CWSS Survey, led Congress to enact
the original Safe Drinking Water Act (SDWA) of 1974. On December 16, 1974, Pres-
ident Ford signed into law the SDWA Public Law 93-523 (PL 93-523). This act gave
the administrator of the fledgling U.S. Environmental Protection Agency (USEPA) the
authority to control the quality of the drinking water in public water systems through
the development of regulations, or by other methods. The act required a three-stage
mechanism to establish comprehensive regulations (and standards) for drinking water
quality:
National Interim Primary Drinking Water Regulations (NIPDWRs) were to be
promulgated to protect the public health. This would be accomplished using gen-
erally available technology and treatment techniques.
•
The National Academy of Sciences (NAS)
12
was to conduct a study on the human
health effects of exposure to contaminants in drinking waters. This study would
''consider only what is required for protection of the public health, not what is
technologically or economically feasible or reasonable.''
12
•
Revised National Primary Drinking Water Regulations were to be promulgated,
based on the NAS report, establishing maximum contaminant levels, to be set at
levels sufficient to prevent the occurrence of any known or anticipated adverse
health effects with an adequate margin of safety.
•
From 1975 to 1983, the USEPA promulgated interim regulations based on the 1962
Public Health Service Standards included in Tables 1-2 and 1-3. Some of the stan-
dards were revised by the EPA Advisory Committee on the Revision and Application
of the Drinking Water Standards. The first set of interim regulations became effective
on June 24, 1977, and contained maximum contaminant levels (MCLs) and monitoring
requirements for microbiological contaminants, ten inorganic chemicals, six organic
compounds, radionuclides, and turbidity.
Disinfection By-products
An additional interim regulation was adopted on November 29, 1979, regulating a new
class of four contaminants: trihalomethanes (THMs). Researchers at USEPA and the
Netherlands had discovered in 1974 that THMs were formed in drinking water as a
result of chlorinating water that contained natural organic matter.
13
The four THM
compounds include chloroform, bromoform, bromodichloromethane, and dibromo-
chloromethane and are regulated together as Total THMs (TTHMs), or the sum of the
concentration of each compound. At that time, chloroform was a suspected human
carcinogen, and by 1976 the U.S. Food and Drug Administration (USFDA) had banned
its use in all drugs. Thus, by 1979, the National Interim Primary Drinking Water
Regulations were complete.
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These are shown in Table 1-4.
In 1979, USEPA also set regulations for a set of non-enforceable standards. These
National Secondary Drinking Water Regulations (NSDWRs) provide MCLs and guid-
ance
to
public water suppliers
regarding contaminants that may cause aesthetic
