Drinking Water Quality for the 21" Century
275
hypothesized as being the precursor materials to the newly defined organic
disinfection bypro ducts (DBPs).
The Safe Drinking Water Act (SDWA) of 1974 and its Amendments in 1986 and
1996 are changing the way in which water is treated and delivered in the United
States. Drinking water standards throughout the western world often take their cue
from US regulations. The United States Environmental Protection Agency (USEPA)
actively assists in the development of the World Health Organization's Guidelines for
Drinking Water Quality (WHO 1996), which provides a basis worldwide for
communities to take appropriate preventative action in order to maintain a high level
of drinking water quality. The European Union produces directives that establish
minimum standards for water quality; the member states can choose to enforce at
higher levels if appropriate to their economic status. Each of these Standards' bodies
shares the goals of ensuring the availability of a high-quality drinking water for the
consumer. Under the SDWA, for example, the USEPA is required to regulate
chemicals in drinking water so that high standards of quality are attained at the point
of consumption. The Surface Water Treatment Rule (SWTR) promulgated under the
SDW A specifies treatment and monitoring requirements that must be met by all
public water suppliers, but these may be in conflict with the chemicals in use to meet
the treatment goals if those chemicals are compromising fmished water quality.
In 1984, the USEPA began to regulate the acceptable levels of DBPs in
distributed waters based upon epidemiological data and the ability to measure low
levels of byproducts in drinking water. Trihalomethanes (THMs) and haloacetic
acids (HAAs) are the dominant species found in finished drinking water (Rook
1977) and both classes of disinfection byproducts (DBPs) have been identified as
possible human carcinogens. In fact, bromodichloromethane (CHCIzBr) (a
bromine-containing THM) does appear to be genotoxic and could be the THM
responsible for carcinogenic activity in drinking water (Pegram 1995).
Furthermore, Waller and coworkers (1998) found an association between high
exposure to TTHMs and in particular CHel2Br and spontaneous abortion in
humans. There are also concerns that bromine-containing HAAs may be of higher
carcinogenic risk than the THMs (Bull 1995) and the USEP A has found that
bromate is the most carcinogenic of the DBPs assessed to date (USEPA 1994).
The current regulated levels in the United States are dictated by stage I of the
Disinfectants/Disinfection By-Products (D/DBP) Rule, which establishes
maximum contaminant levels (MCLs) for total trihalomethanes and five of the
haloacetic acids (HAAS) at 80 and 60 Ilg r', respectively. Many surface-water
treatment plants practicing chlorination were quickly found to be out of
compliance on the regulated levels of these compounds and were faced with
having to make some serious choices about alternative treatment technologies. At
the front end of the process, the removal of natural organic matter could be
attempted by physical/chemical means using a process of coagulation and
filtration or the conversion of this material into lower molecular weight forms,
incompatible with the formation of the halogenated byproducts with chlorine, or
subsequently attempted using oxidation processes such as with ozonation. In
either of these cases, it became clear that there need not be a compromise on the
disinfection status of the water, since now when the chlorine was added, the
275
hypothesized as being the precursor materials to the newly defined organic
disinfection bypro ducts (DBPs).
The Safe Drinking Water Act (SDWA) of 1974 and its Amendments in 1986 and
1996 are changing the way in which water is treated and delivered in the United
States. Drinking water standards throughout the western world often take their cue
from US regulations. The United States Environmental Protection Agency (USEPA)
actively assists in the development of the World Health Organization's Guidelines for
Drinking Water Quality (WHO 1996), which provides a basis worldwide for
communities to take appropriate preventative action in order to maintain a high level
of drinking water quality. The European Union produces directives that establish
minimum standards for water quality; the member states can choose to enforce at
higher levels if appropriate to their economic status. Each of these Standards' bodies
shares the goals of ensuring the availability of a high-quality drinking water for the
consumer. Under the SDWA, for example, the USEPA is required to regulate
chemicals in drinking water so that high standards of quality are attained at the point
of consumption. The Surface Water Treatment Rule (SWTR) promulgated under the
SDW A specifies treatment and monitoring requirements that must be met by all
public water suppliers, but these may be in conflict with the chemicals in use to meet
the treatment goals if those chemicals are compromising fmished water quality.
In 1984, the USEPA began to regulate the acceptable levels of DBPs in
distributed waters based upon epidemiological data and the ability to measure low
levels of byproducts in drinking water. Trihalomethanes (THMs) and haloacetic
acids (HAAs) are the dominant species found in finished drinking water (Rook
1977) and both classes of disinfection byproducts (DBPs) have been identified as
possible human carcinogens. In fact, bromodichloromethane (CHCIzBr) (a
bromine-containing THM) does appear to be genotoxic and could be the THM
responsible for carcinogenic activity in drinking water (Pegram 1995).
Furthermore, Waller and coworkers (1998) found an association between high
exposure to TTHMs and in particular CHel2Br and spontaneous abortion in
humans. There are also concerns that bromine-containing HAAs may be of higher
carcinogenic risk than the THMs (Bull 1995) and the USEP A has found that
bromate is the most carcinogenic of the DBPs assessed to date (USEPA 1994).
The current regulated levels in the United States are dictated by stage I of the
Disinfectants/Disinfection By-Products (D/DBP) Rule, which establishes
maximum contaminant levels (MCLs) for total trihalomethanes and five of the
haloacetic acids (HAAS) at 80 and 60 Ilg r', respectively. Many surface-water
treatment plants practicing chlorination were quickly found to be out of
compliance on the regulated levels of these compounds and were faced with
having to make some serious choices about alternative treatment technologies. At
the front end of the process, the removal of natural organic matter could be
attempted by physical/chemical means using a process of coagulation and
filtration or the conversion of this material into lower molecular weight forms,
incompatible with the formation of the halogenated byproducts with chlorine, or
subsequently attempted using oxidation processes such as with ozonation. In
either of these cases, it became clear that there need not be a compromise on the
disinfection status of the water, since now when the chlorine was added, the