Water Treatment
▲Caution
predict the corrosive tendencies of the tower water toward concrete. An explanation and method of calculating the Langelier index can be found in all books on water treatment. Maintaining a positive Langelier index provides excellent protection of concrete.
Slime, a gelatinous organic growth, and algae, a green or brown plant growth, may grow in the cooling tower or heat exchangers. Their presence can interfere with cooling efficiencies. Proprietary compounds are avail- able from water treating companies for the control of slime and/or algae; however, compounds which contain copper are not recommended.
Chlorine, if used, should be introduced at a point in the circulating water system that will promote rapid dispersal, and residual chlorine should not exceed one part per million parts water (1 ppm).
Scaling
Scale can be caused by the uncontrolled presence of sulfates, silicates, carbonates, or oxides, and their effect can be accentuated by the presence of suspended muds. Some suggestions and limitations follow:
•Calcium sulfate may be introduced in the
pressed as CaCO .
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•Calcium carbonate generally will not form scale in the cooling tower if carbonate scaling does not occur in the condenser. However, if
2
•Silica scale is virtually impossible to remove. However, silica scale is unlikely if concentrations of SiO are held below 150 ppm.
2
•Oxides, such as iron oxide, can coat all parts of the system if soluble iron is present in concentrations above 0.5 ppm. Iron oxides do not usually develop into thick scales but, like mud, can accentuate the development of other scales.
Foaming
Heavy foaming sometimes occurs when a new tower is put into opera- tion. This type of foaming generally subsides after a relatively short period of operation. Persistent foaming can be caused by the concentrations of certain combinations of dissolved solids or by contamination of the circulating water with
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