9.5 Standards Required of Water 243
regulations, at no time can turbidity (cloudiness of
water) go above 5 nephelometric turbidity units (NTU);
systems that filter must ensure that the turbidity go no
higher than 1 NTU (0.5 NTU for conventional or direct
filtration) in at least 95% of the daily samples in any
month. As of January 1, 2002, turbidity may never
exceed 1 NTU, and must not exceed 0.3 NTU in 95%
of daily samples in any month.
9.5.1.3 Chemical Standards
The EPA standards are by far the most comprehensive
and include maximum quantities, expected in water, of
disinfectants, by-products of disinfectants, inorganic
chemicals such as antimony, arsenic, lead and mercury,
organic chemicals such as acrylamide and benzene,
radionucleotides such as alpha particles.
9.5.2 Standards Required for Recreational Waters
Standards set for drinking water include microbiologi-
cal, chemical, radiological, turbidity, etc. For recre-
ational waters, the standards appear to be mainly
microbiological. Furthermore, since diseases, which
can be contacted in recreational waters, are not enteric
ones that enter by the oral–fecal route, it has been sug-
gested that the standards should include the content of
water of other indicators, organisms besides those used
for drinking water. Microorganisms that are used to
assess the microbial quality of swimming pool and
similar environments include heterotrophic plate count- HPC (a general measure of nonspecific microbial
levels), fecal indicators (such as thermotolerant coli-
forms, E. coli), Pseudomonas aeruginosa,
Staphylococcus aureus and Legionella spp. HPC, ther-
motolerant coliforms, and E. coli are indicators in the
strict sense of the definition.
As health risks in pools and similar environments
may be fecal or non-fecal in origin, both fecal indica-
tors and non-fecally derived microorganisms (e.g., P.
aeruginosa, S. aureus, and Legionella spp.) should
therefore be examined. Fecal indicators are used to
monitor for the possible presence of fecal contamina-
tion; HPC, Pseudomonas aeruginosa, and Legionella
spp. can be used to examine growth, and Staphylococcus
aureus can be used to determine non-fecal shedding.
The absence of these organisms, however, does not
guarantee safety, as some pathogens are more resistant
to treatment than the indicators, and there is no perfect
indicator organism.
In practice, enteric organisms have mainly been
used. Thus, to protect human health from waterborne
pathogens, the EPA recommends monitoring marine
recreational waters for enterococci (recommended
threshold: geometric mean of 35/100 mL), and in
Table 9.5 (continued)
List of National Secondary Drinking Water Regulations
Contaminant Secondary standard
Aluminum 0.05 to 0.2 mg/L
Chloride 250 mg/L
Color 15 (color units)
Copper 1.0 mg/L
Corrosivity noncorrosive
Fluoride 2.0 mg/L
Foaming agents 0.5 mg/L
Iron 0.3 mg/L
Manganese 0.05 mg/L
Odor 3 threshold odor number
pH 6.5-8.5
Silver 0.10 mg/L
Sulfate 250 mg/L
Total dissolved solids 500 mg/L
Zinc 5 mg/L
Last updated on Wednesday, March 18th, 2009. http://www.epa.gov/safewater/contaminants/index.html