Sessional_Paper_1911 — Page 225

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RESULTS OBTAINED FROM WATER SUPPLIES.

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(1) in England and America.

(2) in the Tropics generally.

It is necessary to note very briefly the chief differences between the Hongkong Waters and waters of a Temperate climate and other parts of the Tropics.

To illustrate what obtains in England the "Reports on the condition of the Metro- politan Water Supply" for the year 1910 have been made use of. It was considered particularly desirable to take the London Water as the example, though this is usually not done, as the Hongkong Water has already by others been compared with the London Water,

For America, the Report of the Massachusett's State Board of Health for the year 1909 has been made use of.

In both cases it will be noticed at once how far more efficacious the filtration is than is got either in Hongkong or in other parts of the Tropics. Tropical filtration gives relatively very disappointing results both as regards the total colonies on Agar per c.c. and as regards the removal of B. Coli from the filtered water.

As regards reports on the water in the Tropics generally, only a very scanty number of reports have been available; as far as they go they have been briefly noted.

·

LONDON Water,

The following tables are complied from the "Reports on the condition of the Metro- politan Water Supply" which were published monthly during the year 1910.

The average total number of colonies on Agar at 37° C. for 24 hours in the unfiltered raw waters ranged from 47 to 1,228 and typical B. Coli were present from 001 c.c. of the sample up to samples which were negative in 100 c.c.

After filtration the total number of Colonies on Agar at 37° C for 24 hours varied from 13 to 46 per c.c. (see Table XV) and B. Coli (Typical) were absent from 79 to 93 per cent of the samples in 100 c.c. of water (Table XVI). No such good results as these are obtained in Hongkong or as far as I know in any other Tropical place.

AMERICA.

Table XVII represents the results published by the Massachusett's State Board of Health for the year 1909 of the Lawrence City Water.

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