Waters containing organic matter that differs much in quantity from the examples above may yield very different results and no generalisation can be made that will cover all cases. An increase of temperature increases the germicidal velocity and also the rate of absorption of chlorine by the organic matter; other factors determine which of these competitive actions predominates. =Method of Application (admixture).= A thorough admixture of the water and chlorine is a _sine qua non_ for successful operation. This should, if possible, be attained by natural means, but if there is any doubt as to the efficiency of the mixing process, mechanical appliances should be utilised. Pumps, especially centrifugal pumps, constitute a very convenient and efficacious method of mixing the germicide and the water, and the solutions should never be injected into the discharge pipes when it is possible to make connections with the suctions. [Illustration: DIAGRAM III EFFECT OF TEMPERATURE] [Illustration: DIAGRAM IV EFFECT OF TEMPERATURE] Inefficient admixture leads to local concentration of the chlorine, a condition which (_vide_ p. 35), results in a wastage of the disinfectant. Two practical examples of this effect may be cited. In one case the water was free from colour and contained very little organic matter. This water was chlorinated at one plant by allowing the bleach solution to drop into one vertical limb of a syphon approximately 6,000 feet long, the other vertical limb being used as a suction well for the pumps which discharged into the distribution mains. At the other plant the bleach solution was injected into the discharge pipe of a reciprocating pump through a pipe perforated with a number of small holes. The results for two typical months are given in Table X. TABLE X.--EFFECT OF EFFICIENT MIXING ------+-----------+-----------------------+--------------- | Available | BACTERIA PER C.CM. | | Chlorine +-----------------------+ | Parts Per | | | B. Coli Index Month.| Million. | Raw |Treated Water. | Per 100 c.cms. +-----+-----+ Water.+-------+-------+-------+------- | A. | B. | | A. | B. | A. | B. ------+-----+-----+-------+-------+-------+-------+------- July | 0.20| 0.25| 864 | 27 | 93 | <0.2 | 8.5 August| 0.20| 0.27| 1.108 | 12 | 120 | <0.2 | 10.2 ------+-----+-----+-------+-------+-------+-------+------- A = efficient mixing. B = inefficient mixing. The results with the "B" plant were very irregular. The hypochlorite and water did not mix thoroughly and, as several suctions pipes were situated in the suction shaft, there was no subsequent admixture in the pumps; this also caused complaints regarding taste and odour but the complaints were localised, and not general as would result from an overdose of solution due to irregularities at the plant.