Water Pollution - The Drinking Water - page 173

FBRR applies to public water systems that use surface water or groundwater
under the direct influence of surface water, practice conventional or direct
filtration, and recycle spent filter backwash, thickener supernatant, or liquids
from dewatering processes.
Note: This section has provided only a summary of federal drinking
water requirements; to ensure full compliance, consult the federal regu-
lations at 40 CFR 141 and any approved state requirements.
Opportunities for Public Involvement
The USEPA encourages public input into regulation development. Public
meetings and opportunities for public comment on MDBP rules are
announced in the Federal Register . The USEPA's Office of Groundwater and
Drinking Water also provides information regarding the MDBP rule and
other programs online ( www.epa.gov/safewater/standards.html ).
Flocculants
In addition to chlorine and sometimes fluoride, water treatment plants often
add several other chemicals, including flocculants, to improve the efficiency
of the treatment process—and they all add to the cocktail mix. Flocculants
are chemical substances added to water to make particles clump together,
which improves the effectiveness of filtration. Some of the most common
flocculants are polyelectrolytes (polymers)—chemicals with constituents
that cause cancer and birth defects and are banned for use by several coun-
tries. Although the USEPA classifies them as “probable human carcinogens,”
it still allows their continued use. Acrylamide and epichlorohydrin are two
flocculants used in the United States that are known to be associated with
probable cancer risk (Lewis, 1996).
Groundwater Contamination
Groundwater under the direct influence of surface water comes under the
same monitoring regulations as does surface water (i.e., all water open to the
atmosphere and subject to surface runoff). The legal definition of groundwa-
ter under the direct influence of surface water is any water beneath the surface
of the ground with (1) significant occurrence of insects or microorganisms,
algae, or large-diameter pathogens such as Giardia lamblia ; or (2) significant
and relatively rapid shifts in water characteristics such as t u r b i d it y, tempera-
ture, conductivity, or pH, which closely correlate to climatological or sur-
face water conditions. Direct influence must be determined for individual