Chlorination of Water

by Joseph Race

TABLE VII.—OXYGEN TO CHLORINE RATIO

Observer.	Oxygen Absorbed Ratio ————————. Chlorine Absorbed
Rouquette	1
Bonjean	0	.5
Orticoni	Less than 1
Valeski and Elmanovitsch	0	.4
Race	0	.4
Theoretical	0	.22

The value of 0.4 (0.39) obtained by the author is the average of over one hundred determinations covering a period of two years. The experiments of Zaleski and Elmanovitsch were made with the water of the Neva River.

The divergence in the ratios affords additional evidence in favor of reaction (2) mentioned on [page 28] and also shows that the chlorinated compounds are less readily oxidized than those from which they are produced. Heise[8] has found that the amount of chlorine consumed is usually proportional to the concentration in which it is added though not necessarily a function of the concentration of the organic matter.

Temperature. The evidence regarding the effect of temperature upon the dosage required is somewhat conflicting. Ellms ([vide supra]) found that the velocity of the germicidal action varied directly with the temperature and this has also been the author’s experience with laboratory experiments. Typical examples of these are given in [Tables VIII] and [IX].

TABLE VIII.[B]—EFFECT OF TEMPERATURE

Available Chlorine 0.4 Part Per Million
Contact Period.	Temperature, degrees, Fahrenheit.
	36	70	98
Nil	424	424	424
5 minutes	320	280	240
1.5 hours	148	76	12
4.5 hours	38	14	3
24 hours	2	0	0
48 hours	2	0	0
[B] Resultsare B. coli per 10 c.cms.

TABLE IX.[C]— EFFECT OF TEMPERATURE

Available Chlorine 0.2 Parts Per Million
Contact Period.		Temperature, degrees, Fahrenheit.
		36	70	98
Nil		240	240	240
5	minutes	240	250	235
1	hour	245	235	195
4	hours	215	190	170
24	hours	143	130	115
48	hours	130	59	19
72	hours	...	28	...
96	hours	...	16	...
120	hours	...	6	...
[C] Resultsare B. coli per 10 c.cms.

The reaction velocity of a germicide is proportional to the temperature[9] and the influence of temperature may be mathematically expressed by the formula K1/K2 = θ(T2 - T1), in which K1 and K2 are the constants of the reaction at temperatures T2 and T1, respectively, and θ is the temperature coefficient. From the value of θ, the velocity constant of a germicide for any temperature may be calculated from the equation KT = K20° × θ(T - T20°). K1 and K2 are obtained from the formula KT = log(N1/N2)/(t2 - t1) in which N1 - N2 is the number of bacteria destroyed in the interval t2 - t1.