Building Design and Construction Handbook - Merritt - Ventech!

14.4 SECTION FOURTEEN
Publishing Company, New York; G. Fair, J. C. Geyer, and D. A. Okun, ‘‘Water and
Wastewater Engineering,’’ John Wiley & Sons, Inc., New York; and E. Nordell,
‘‘Water Treatment for Industrial and Other Uses,’’ Van Nostrand Reinhold, New
York. The ASTM ‘‘Manual on Industrial Water’’ contains extensive data on processwater
and steam requirements for a variety of industries. Data on water for fire
protection are available from the American Insurance Association, New York, and
the National Fire Protection Association (NFPA), Quincy, Mass.
Water for buildings is transmitted and distributed in pipes, which may be run
underground or aboveground. Useful data on pipeline sizing and design are given
in J. Church, ‘‘Practical Plumbing Design Guide,’’ and C. E. Davis and K. E.
Sorenson, ‘‘Handbook of Applied Hydraulics,’’ McGraw-Hill Publishing Company,
New York. The American Insurance Association promulgates a series of
publications on water storage tanks for a variety of services.
Characteristics of Water. Physical factors of major importance for raw water are
temperature, turbidity, color, taste, and odor. All but temperature are characteristics
to be determined in the laboratory from carefully procured samples by qualified
technicians utilizing current testing methods and regulations.
Turbidity, a condition due to fine, visible material in suspension, is usually due
to presence of colloidal particles. It is expressed in parts per million (ppm or mg/
L) of suspended solids. It may vary widely in discharges of relatively small streams
of water. Larger streams or rivers tending to be muddy are generally muddy all the
time. The objection to turbidity in potable supplies is its ready detection by the
drinker. The U.S. Environmental Protection Agency (USEPA) limit is one nephelometric
turbidity unit (NTU).
Color, also objectionable to the drinker, is preferably restricted to 15 color units
or less. It is measured, after all suspended matter (turbidity) has been centrifuged
out, by comparison with standard hues.
Tastes and odors due to organic material or volatile chemical compounds in the
water should be removed completely from drinking water. But slight, or threshold,
odors due to very low concentrations of these compounds are not harmful-just
objectionable. Perhaps the most common source of taste and odor is decomposition
of algae.
Chemical Content. Chemical constituents commonly found in raw waters intended
for potable use and measured by laboratory technicians include hardness,
pH, iron, and manganese, as well as total solids. Total solids should not exceed
500 ppm. Additionally, the USEPA is continually developing, proposing, and adopting
new drinking water regulations as mandated by the Safe Drinking Water Act.
Hardness, measured as calcium carbonate, may be objectionable in laundries
with as little as 150 ppm of CaCO 3 present. But use of synthetic detergents decreases
its significance and makes even much harder waters acceptable for domestic
uses. Hardness is of concern, however, in waters to be used for boiler feed, where
boiler scale must be avoided. Here, 150 ppm would be too much hardness and the
water would require softening (treatment for decrease in hardness).
Hydrogen-ion concentration of water, commonly called pH, can be a real factor
in corrosion and encrustation of pipe and in destruction of cooling towers. A pH
under 7 indicates acidity; over 7 indicates alkalinity; 7 is neutral. Tests using color
can measure pH to the nearest tenth, which is of sufficient accuracy.
Iron and manganese when present in more than 0.3-ppm concentrations may
discolor laundry and plumbing. Their presence and concentration should be determined.
More than 0.2 ppm is objectionable for most industrial uses.