12
REPORT OF THE KING INSTITUTE, GUINDY
raw water of the Adyar river during this period showed very heavy organic
pollution. The submerged sand filter produced sulphuretted hydrogen and
yielded poor results generally while the percolating filter gave definitely better
results and sulphuretted hydrogen was not produced in the filter.
(ii) Experiments at Kilpauk..—The investigation of various methods of
pretreatment of the Madras Red Hills Lake water which commenced in October
1927 has continued throughout the year. Many different methods of purification
have been investigated. During the year under report 9,709 samples of water
from the Kilpauk plant have been examined, compared with 3,336 samples
examined last year. The results of the investigation have been reported to
Government and embodied in G.O. No. 709, P.H., dated 15th March 1929.
It was possible, from the results obtained, to formulate specific recommenda-
-tions for improving the quality of the City water-supply. A system of percolat--
ing filters to precede the secondary sand filters has been recommended for
adoption. Further important experiments are now in progress on the relative
merits of different types of materials for use in the percolating filters.
Sewage.—Mr. N. Swaminathan continued to work as Sewage Analyst and
at times helped with the analyses of many of the water samples at Kilpauk.
During the year under report analyses were made of sewage and effluent
from the sewage installations in Madras and in the mufassal. Brief details are
given in Table XVIII.
Among the Madras installations visited, the Lady Willingdon Training
College, Queen Mary's College,. Engineering College and Waterton Estate dealt
with domestic sewage only. Municipal Septic Tank at Spur Tank received laundry
waste as well as sullage and Carnatic Mills and Buckingham Mills dealt exclusively
with dye-house wastes.
Out of the various samples thus analysed in Madras, the installation at the
Waterton Estate belonging to the Binny Mills Co., Ltd., and the installation at
Engineering College, Guindy, gave satisfactory final effluents. The standard fixed
for the satisfactory final effluents was as follows :—
Albuminoid nitrogen
...
...
...
.. . 0.2 parts per 100,000.
Oxygen absorbed in four hours ......
2.0
"
"
Suspended solids ...... ...
3.0
"
"
The effluents in other cases were not so satisfactory. The unsatisfactory
nature of the final effluents in Carnatic Mills and Buckingham Mills might be
due to the chemical nature of the sewage dealt with.
Analyses of special water samples such as from the Cooum were made,
samples being drawn from different places along the course of the river. The
results showed considerable improvement over last year's figures due to the
pumping of sea-water into it. Such analysis at various points during high and
low tides was also undertaken to find out to what distance from the sea the seep--
age of sea-water into the river was noticeable. It was found that seepage did not
proceed farther than the Commander-in-Chief's Bridge, Egmore, i.e., for about
three miles from the sea.
The Analyst and his staff visited Ootacamund in May 1928 to carry out
analysis of sewage and effluent from the Municipal Septic Tank and Sewage Farm.
The results of this examination conducted for over ten days showed that
though the sewage entering the septic tank was of strong character, the subsoil
final effluent was very satisfactory. It was observed that during rainy weather
some of the septic effluent was found to reach the final effluent channel directly
without being drained through the soil. This is a distinct danger and steps should
be taken to drain it through the soil.
Madura was visited in June 1928 to carry out analysis of sewage and effluent
from the Municipal Sewage Farm. The water entering the Sewage Farm is
mainly sullage which is directly distributed on the farm without any previous
treatment. The results of analyses of the subsoil effluent were quite satisfactory.