MIL-HDBK-1165
water. There are numerous vendors available who specialize in
determining the proper types and dosages of chemicals for cooling
towers. A qualified vendor is one that is able to perform to
specifications and maintain a preset level of water chemistry.
b) Sulfuric acid. There is a chemical treatment
approach that warrants special mention because of its
effectiveness in maintaining cooling tower water quality:
sulfuric acid treatment. Sulfuric acid, when added to
recirculating tower water, lowers the pH of the water and
"digests" metal solids such as calcium bicarbonate (primary cause
of scale), thus solubilizing water sediments. Sulfuric acid
treatment reduces the amount of bleed-off required by increasing
the number of times the water can recirculate. Sulfuric acid is
corrosive, however, and care must be taken to ensure that workers
do not physically come in contact with it, or that the cooling
tower system is not damaged (corrosion) by adding too much
(causing a very low pH). The cost of incorporating and operating
a sulfuric acid system is relatively low. Discharge of the bleed
off may become a problem due to the lowered pH and sewer district
restrictions on allowing acidic solutions into the sewer. Due to
the environmental concerns associated with sulfuric acid, this
method should only be employed if other alternatives are not
feasible.
5.4.1.6
Ozone Injection. Ozone generators have proven very
effective in biocidal treatment of circulating water in cooling
tower systems. Ozone injection has also shown some effectiveness
in reducing system corrosion and scaling, although this process
may not preclude the need for chemical treatment. By adding
ozone treatment you can increase the number of cycles of
concentration of your cooling tower water, reducing the water
usage accordingly. If ozonation can replace the use of chlorine
or other toxic agents, this will also help the installation
attain its pollution prevention goals for toxic chemical
reduction.
5.4.1.7
Water Recycling, Reclamation, and Reuse. Depending on
the quality, the make-up water for cooling towers can come from a
variety of sources such as once-through coolers, reject water
from RO systems, and high quality municipal wastewater effluent.
Incoming make-up water may need to be pretreated by ion exchange,
filtration, or lime softening.
a) Reuse. Cooling tower discharge is usable with
little or no treatment in many applications that do not require a
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