Geology Reference
In-Depth Information
TABLE 13.1 National Primary Drinking Water Standards for Selected Contaminants (USEPA, 2007
http://www.epa .GOV /safewater/contaminants/index.html#listmcl ) . See text for MCLG and MCL. (continued)
Contaminant
MCLG 1
MCL 1
Potential Health Effects
Contaminant Sources
Lindane
0.0002
0.0002
liver, kidney
insecticide, cattle, lumber, gardens
PCBs
0
0.0005
anemia, blood, cancer risk
factories, dry cleaners
Benezene
0
0.005
anemia, blood, cancer risk
factories, gas storage, landfills
Carbon tetrachloride
0
0.005
liver, cancer risk
chemical plants
1,2 Dichloroethane
0
0.005
cancer risk
industrial chemical factories
Ethlbenzene
0.7
0.7
liver, kidney
petroleum refineries
Styrene
0.1
0.1
liver, kidney, circ. syst.
rubber/plastic factories, landfills
Tetrachloroethylene
0
0.005
liver, cancer risk
factories, dry cleaners
Vinyl chloride
0
0.002
cancer risk
PVC pipes, plastic factories
Dioxin (2,3,7,8-TCDD)
0
0.00000003
reproduction, cancer risk
waste incin. chemical factories
Disinfectants
and By-products
MRDLG 8 =4
MRDL 8 =4.0
eye/nose irritation; stomach
Chlorine (Cl 2 )
add to disinfect drinking water
4
Total trihalomethanes
(TTHMs)
0.080
liver, kidney, nervous, cancer
byproduct of water disinfection
Bromate
0
0.010
cancer risk
byproduct of water disinfection.
In milligrams per liter (mg/L) unless otherwise noted
2 More than 5.0% samples total coliform-positive in month, then tests for fecal coliforms or E. coli. Fecal coliform and E. coli are bacteria that indicate water
may be contaminated with human/animal wastes. Disease-causing microbes (pathogens) in these wastes can cause diarrhea, cramps, nausea, headaches, etc.,
and may pose risk of severe illness for infants, the young, and those with weak immune systems.
3 For Giardia and viruses, the TT is a combination of (1) inactivation by disinfection and (2) filtration. Filtration (or boiling at home) is the technique for
Cryptosporidium, which has cysts very resistant to chlorine-based disinfect. Legionella is also controlled through inactivation/filtration. Turbidity a measure
of filtration effectiveness and must be < 0.3 NTU in 95% samples/month. (Treatment Technique is a required process intended to reduce level of a contami-
nant in drinking water.)
4 None established.
5 Nde or nde, natural deposit erosion
6 Million fibers per liter (<10 um in size)
7 Lead and copper TT controls the corrosiveness of water. When >10% of tap water samples exceed "action level" (in parens.) then additional steps needed.
8 MRDLG, Maximum Residual Disinfectant Level Goal (residual from water treatment), MRDL, Maximum Residual Disinfectant Level.
PART A. SIGNIFICANCE OF SELECTED
MAJOR INORGANIC CONSTITUENTS
Hardness
moderately hard, 121 to 180 ppm is hard, and more
than 180 ppm is very hard.
CALCIUM (Ca). Calcium may be leached from most
rocks, but limestone and dolomite provide the largest
amount. Calcium is a major cause of hardness and
forms scale on utensils, boilers, and pipes. Calcium is
not considered detrimental to health.
Hard water usually has significant amounts of calcium
and magnesium. Hardness is usually associated with
the effects that take place when using soap. Hard
water requires the use of large amounts of soap and
leaves insoluble residues in bathtubs and sinks. In
addition, hard water causes scale to form in water
heaters, boilers, and pipes.
Hardness depends mainly on the concentration
of calcium (Ca) and magnesium (Mg), but other sub-
stances such as sulfate (SO4) also form insoluble
residues from soap. Water having a hardness of less
than 60 ppm is considered soft, 61 to 120 ppm is
SODIUM (Na). Sodium is readily leached from rocks
and tends to remain in solution. Any salt, clay or silt-
rich deposits may provide high sodium concentrations
to circulating water. In addition, sodium may be taken
into solution if the transporting water comes in contact
with sewage or industrial wastes. The concentration of
sodium is not especially important in water for
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