As tank _B_ was previously used as a bleach storage tank, the change from hypochlorite alone to chloramine necessitated very little expense. The treatment was commenced by gradually increasing the quantity of ammonia, until a dosage of 0.12 p.p.m. was reached, and constantly increasing the dosage of bleach, which was formerly 0.93 p.p.m. of available chlorine. Owing to the restrictions imposed by the Provincial authorities it has not been possible to maintain a dosage as low as that indicated as sufficient by the experimental plants results, but some interesting data have been obtained. Table XXIX shows the results obtained from February to October, 1917, from the chloramine treatment at Ottawa and also those obtained with liquid chlorine at Hull where the same raw water is treated with 0.7-0.8 p.p.m. of chlorine. TABLE XXIX.--CHLORAMINE RESULTS AT OTTAWA ---------+--------------+----------+--------+------------------+------- | _B. coli_ | | | | Hull |PER 100 C.CMS.| | | DOSAGE P.P.M. |_B. coli_ 1917 +------+-------+Turbidity.| Colour.+---------+--------+Per 100 | Raw | Tap | | | | |c.cms. |Water.| Water.| | |Chlorine.|Ammonia.| ---------+------+-------+----------+--------+---------+--------+------- Feb. | 268 | 0.88 | 3 | 40 | 0.57 | 0.05 | .... Mar. 1-18| 250 | 0.96 | 4 | 40 | 0.32 | 0.11 | .... Mar. 1-31| 643 | 0.43 | 4 | 40 | 0.47 | 0.14 | .... April | 5228 | 0.34 | 31 | 32 | 0.56 | 0.10 | .... May | 162 | <0.08 | 3 | 39 | 0.52 | 0.08 | .... June | 114 | <0.08 | 3 | 41 | 0.51 | 0.08 | .... July | 237 | 0.08 | 5 | 41 | 0.51 | 0.08 | 44.4 Aug. | 165 | 0.08 | 4 | 42 | 0.51 | 0.10 | 28.0 Sept. | 55 | <0.08 | 6 | 42 | 0.50 | 0.09 | 15.2 Oct. | 31 | 0.15 | 5 | 42 | 0.42 | 0.08 | 1.1 ---------+------+-------+----------+--------+---------+--------+ Average | 211 | 0.22 | 7 | 40 | 0.51 | 0.09 | ---------+------+-------+----------+--------+---------+--------+------- At the height of the spring floods the raw water contained 80 p.p.m. of turbidity and over 500 _B. coli_ per c.cm. but 0.6 p.p.m. of chlorine and 0.13 p.p.m. of ammonia reduced the _B. coli_ index in the tap samples to 2.5 per 100 c.cms.; samples taken in Hull on the same day (treated with 0.7-0.8 p.p.m. of liquid chlorine) gave a _B. coli_ index of 26.7. Previous experiences in Ottawa has shown that a dosage of approximately 1.5 p.p.m. of available chlorine is required to reduce the _B. coli_ index to 2.0 per 100 c.cms. under similar physical and bacteriological conditions.