Water from the pre-filters (polarite and sand) was treated with bleach to give a concentration of 1 p.p.m. of available chlorine and passed through the De Chlor filter. The average bacteriological results obtained during the first six months operation were as follows:
| Bacteria Per c.cm. Gelatine 3 Days at 20° C. | B. coli Index Per 100 c.cms. | |
| Raw river water | 6,775 | 600 |
| Water from pre-filters | 579 | 119 |
| Water from De Chlor filter | 33 | Nil |
Free chlorine could not be detected by chemical tests in the filtered water which was also free from abnormal tastes and odours. It is stated that the carbon has to be removed and revivified periodically. The filter was washed about once per week, the wash water being only one-tenth of one per cent.
The experimental filter was operated for nearly two years before being removed to permit the erection of larger units having a total capacity of one million Imp. gallons per day.
BIBLIOGRAPHY
[1] Hooker. Chloride of Lime in Sanitation, New York, 1913.
[2] Griffen and Hedallen. J. Soc. Chem. Ind., 1915, 34, 530.
[3] Hale. Proc. N. J. San. Assoc., 1914.
[4] Adams. J. Amer. Pub. Health Assoc., 1916, 6, 867.
[5] Ellms and Hauser. J. Ind. and Eng. Chem., 1913, 5, 915 and 1030; ibid., 1914, 6, 553.