effective in taste and odor control, provided
1. type of activated carbon used meets
2. dosage is correct,
3. carbon is mixed intimately with the water,
4. carbon is in contact with the water for an
Acceptable commercial preparations of ac-
tivated carbon should meet the following
1. It does not contain any soluble mineral in-
jurious to health.
2. Moisture content is not over 8.0 percent.
3. It is powdered form that wets down and
goes into suspension readily, does not settle too
rapidly, and does not float on the surface when
4. At least 99 percent of the carbon in water
suspension passes a 100-mesh sieve and 95 per-
cent passes a 200-mesh sieve.
5. It has enough adsorption capacity to reduce
a concentration of 0.1 milligrams per liter (mg/l)
phenol in distilled water to 0.01 ppm.
Because of the wide range in waters, no
general rule can be given for activated-carbon
dosage. The dose required at each water plant
must be determined by periodic laboratory tests.
The test is made by preparing a number of
samples of raw water, adding the standard
amount of treating chemicals and varying
amounts of carbon to each sample, allowing plant
contact time, filtering, and making odor tests.
Numerical comparison can be made with the
threshold odor test. A carbon dose of 3 ppm
removes most tastes and odors from water.
However, dosages can vary from 3 to 15 ppm,
depending upon the odor of the water. Laboratory
tests will determine the dosage.
Activated carbon is fed into the water by dry
feeders. It must be handled more carefully than
coagulant because it is a fine powder; therefore,
the feeder must bean approved type and designed
to prevent the spreading of the carbon dust and
causing fires. In addition, inhaling of the dust by
personnel, even in low concentration, can affect
their lungs. The dry feeder room should have
explosion proof electrical equipment. A spark or
pilot flame can create an explosion. Dry carbon
will float on the surface of the water for a long
time. Therefore, it is important that the carbon
be wetted thoroughly, mixed by agitation using
a paddle wheel, swirling action, a spray, or so
forth, in a small tank. Some dry feeders have a
mixing chamber in which the carbon is wetted by
the swirling action of the water.
Activated carbon may be applied to the water
at one or several points, depending on the results
desired. Carbon is added at one or more of the
. In the raw water, as early as possible after
it enters the plant. This point of application is not
recommended for extremely turbid waters.
. In the mixing basin. When added before
sedimentation, activated carbon not only removes
foreign matter from the water, but the carbon that
settles in the sedimentation basin continues to
absorb products of sludge decomposition, thus
preventing formation of secondary tastes and
odors. Black alum is premixed activated carbon
and coagulant that can be used in special situa-
tions both as a coagulant and for taste and odor
CHEMICAL, BIOLOGICAL, AND
Should chemical or biological agents or
nuclear weapons be employed during conflicts,
the water supply of the area involved would, in
all likelihood, become contaminated. A water
source contaminated with a chemical, biological,
or radiological agent can cause incapacitation
or death to a consumer. Effective means for
determining the presence of CBR agents, followed
by proper decontamination procedures, can
reduce or eliminate the hazards caused by these
In the event that you are assigned to super-
vise or manage a field water supply point, you
will be responsible for the detection and removal
of CBR contaminants. The supervisor of a water
point crew must be sure the crew is trained
in the identification of CBR contamination by