AnnualReport-1931 — Page 457

M 122

One of the objects in examining the large number of tap samples was to check the chlorination of the water. The bulk of these samples showed no free chlorine which could be detected by the ortho-tolidine test, that is, the concentration in these was less than 0.02 parts per million. The following Table gives the results of these free-chlorine tests on tap samples:

No free chlorine fluid (less than 0.01 parts per million) 813 Samples Between 0.01 and 0.05 parts per million 199 0.05 and 0.10 50 77 " 21 ?? 25 0.10 and 0.15 20 39 " 0.15 and 0.20 19 27 " 1 "" " 7 Above 0.20 parts per million Highest figure found 0.20 ""

As regards the samples taken at the filter beds, it may be said that the general quality of the water was good. The following Table gives the least satisfactory figures for each of the principal supplies during the year:

Supply Colour* Transparency NH3 NH3 Oxygen absorbed Aberdeen 102.0 10 cm 0.0016 0.0061 0.069 Elliot 30.4 70 cm 0.0011 0.0077 0.047 West Point 3.0 100 cm 0.0016 0.0055 0.957 Albany 17.5 80 cm 0.0011 0.0055 Bowen Road 2.8 100 cm 0.0011 0.0055 0.026 Eastern 15.6 90 cm Shaukiwan 4.8 Sai Wan 3.9 Kowloon 69.0 30 cm 0.0011 0.0044 0.036 100 cm 0.0011 0.0055 0.008 100 cm 0.0016 0.0039 0.015 0.0011 0.0069 0.041 Shing Mun 62.6 21 cm 0.0022 0.0083 0.088

*Colour expressed in Lovibond units per 24 inch stratum.