DIAGRAM IX
BLEACH AND AMMONIA PRICES
In Canada, the market conditions are still (1918) favourable to the chloramine process: bleach is 25 per cent higher than the U.S.A. product and ammonia can be obtained for one-half the New York prices.
Advantages of the Chloramine Process. Although the market conditions may, in some instances, be unfavourable to the chloramine process, the method possesses certain advantages that more than offset a slight possible increase in the cost of materials. The taste and odour of chloramine is even more pungent than that of chlorine but since the introduction of the process in Ottawa no complaints have been received. Owing to the reduced dosage, slight proportional fluctuations in the dosage do not produce the same variations in the amount of free chlorine which is the usual cause of complaints. A public announcement that the amount of hypochlorite has been reduced also has a psychological effect upon the consumers and tends to reduce complaints due to auto-suggestion.
The most important advantage of the process is the elimination of the aftergrowth problem. At Denver, where the aftergrowth trouble is possibly more acute than at any other city on the continent, it was effectively banished by the use of chloramine. At Ottawa, the sanitary significance of B. coli aftergrowths is no longer of practical interest because such aftergrowths have ceased to occur. Whatever may be their opinion as to the sanitary significance of aftergrowths, all water sanitarians will agree that the better policy is to prevent their occurrence.
Operation of Chloramine Process. For the successful operation of the chloramine process, the essential factors are low concentrations of the hypochlorite and ammonia solutions. The author has found that hypochlorite containing 0.3-0.5 per cent of available chlorine and ammonia containing 0.3-0.5 per cent of anhydrous ammonia can be mixed in a 4 : 1 or 8 : 1 ratio without appreciable loss in titre. Solutions of these concentrations mixed in 4 : 1 ratio lost only 2-3 per cent of available chlorine in fifteen minutes and less than 10 per cent in five hours. The effect of mixing solutions containing 4.35 per cent of available chlorine and 2.2 per cent of ammonia is shown in [Table XXX].
TABLE XXX.—LOSS ON MIXING HYPOCHLORITE
AND AMMONIA
| Hypochlorite containing 4.35 per cent available chlorine. Ammonia contained 2.2 per cent NH3 | |||
| Ratio Chlorine to Ammonia by Weight. | Loss of Available Chlorine After | ||
| Few Minutes. | 1 Hour. | 24 Hours. | |
| Per cent | Per cent | Per cent | |
| 6 : 1 | 19 | 19 | 19 |
| 4 : 1 | 24 | 25 | 25 |
| 2 : 1 | 45 | 47 | 47 |
| 1 : 1 | 91 | 91 | 92 |
| 1 : 2 | 20 | 28 | 65 |
The stability of chloramine is a function of the concentration and the temperature and in practice it will be found advisable to determine in the laboratory the maximum concentrations that can be used at the maximum temperature attained by the water to be treated (cf. Muspratt and Smith[6]).