(1) Activated carbon. This treatment is used when blister agents are
present. Activated carbon is a relatively pure, finely powdered form of carbon that
adsorbs many substances readily. It is an excellent adsorbing agent because the
fineness and porosity of the carbon particles give it an enormous surface area. One
cubic inch of activated carbon particles has an internal and external exposure area of
about 20,000 square yards. The activated carbon is added to a pretreatment tank set
up separately from the coagulator assembly. Raw water is pumped into this
pretreatment tank from the source and the activated carbon is added. A concentration
of 600 ppm is generally sufficient. The water is al lowed to remain in contact with the
carbon for 30 minutes or longer and is then pumped to the purification unit for the usual
treatment.
(2) Aeration. When hydrogen cyanide is the contaminant and the water is
warm (700F or above), the aeration treatment may be used. Water may be aerated by
spraying it into the air, allowing it to flow over cascades, passing it through beds of
coke, or passing air under pressure into the water. The spray method can be effectively
used with Army purification equipment. Water can be recirculated through storage
tanks or reservoirs by pumping the water out of the tank and spraying it back through an
elevated strainer or nozzle attached to the discharge end of the hose (see figure 6-18).
Figure 6-18. Aeration of water
MD0160
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