London's Pulse: Medical Officer of Health reports 1848-1972
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Hints from the Health Department. Leaflet from the archive of the Society of Medical Officers of Health. Credit: Wellcome Collection, London
London County Council 1900
[Report of the Medical Officer of Health for London County Council]
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12
29th May,
1899
(dry coke)*
7th Feb., 1900.
Decrease.
15th March, 1900.
Decrease.
Primary coarse bed A
Primary coarse bed B
Secondary coarse bed A l
Secondary fine bed B 1
68.7
70.3
61.7
53.1
21.8
21.2
50.6
44.4
46.9
49.1
11.1
8.7
20.3
17.9
50.6
44.4
1.5
3.3
nil.
nil.
During these experiments the temperature of the sewage and of the effluents from the
various coke-beds was recorded. The average of these records shows that there was a fall of
about 7 degrees Fahrenheit in the temperature of the liquids in the beds, but that while the beds
were standing empty their temperature increased by about 3 degrees. The temperature of the
atmosphere during these examinations was on the average 10 degrees lower than that of the sewage
before it passed on to the coke-beds, and the tanks containing the beds were freely exposed on
all sides to the cooling action of the air.
The average results of these estimations are given in the following table—
| After the bed had remained empty for an average period of 5 hours. | After the bed had remained empty for an average period of 21 hours. | Composition of fresh air. | |
|---|---|---|---|
| Oxygen | 8.0 per cent. | 10.3 per cent. | 20 96 per cent. |
| Carbon dioxide | 5.7 „ | 5.7 „ | 0.04 „ |
The amount of ntirification effected by the beds is indicated in the following table—
| Average quantity of oxidised nitrogen present in the sewage and in the effluents from the beds. | ||||||
|---|---|---|---|---|---|---|
| During the period July 4th, 1899, to December 30th, 1899. | During the period January 1st, 1900, to May 19th, 1900. | During the whole period July 4th, 1899, to May 19th, 1900. | ||||
| Nitrous nitrogen. | Nitric nitrogen. | Nitrous nitrogen. | Nitric nitrogen. | Nitrous nitrogen. | Nitric nitrogen. | |
| Crude sewage | 0.0057 | 0.2289 | 0.0291 | 0.0783 | 0.0162 | 0.1617 |
| Effluent from primary coarse bed A | 0.1331 | 0.6391 | 0.0747 | 0.3937 | 0.1069 | 0.5291 |
| 0.0921 | 0.5089 | 0.0582 | 0.3297 | 0.0769 | 0.4289 | |
| „ secondary ,, ,, Al | 0.1096 | 1.3256 | 0.1187 | 1.0325 | 0.1137 | 1.1948 |
| „ „ fine „ B1 | 0.0584 | 2.2659 | 0.0540 | 2.2430 | 0.0564 | 2.2557 |
3.—PARTICULARS OF THE EXPERIMENTS OX THE BACTERIAL OR XATURAL PROCESS
OF SEWAGE PURIFICATION AT THE XORTHERN OUTFALL WORKS
(BARKING) WHICH HAVE NOT BEEX PREVIOUSLY REPORTED.
(a) The Purification of Crude Sewage by Passage through a Settling Tank and Subsequent
Treatment in a Coke-bed. (Series III.)
Since the loss in capacity of the bacteria beds appeared to have been caused by the suspended
matter present in crude sewage, a preliminary process of sedimentation was next tried.
This series of experiments was carried out between November 7th, 1900, and August 10th,
1901. It was the third series of experiments with crude sewage in coke-beds at the Northern
Outfall and, following previous reports, brings the publication of the details of the experiments
and' of the analytical results of the whole of the experiments up to the end of the year 1901..
I.—Particulars as to the arrangement of the tanks and of the beds.
The four iron tanks used in connection with the previous experiments were used for this
series in the following manner—
The two upper tanks, which were on a higher level than the others, and which had been
used as primary beds in the previous experiments, were emptied of their coke, and were used as
settling tanks (A and B). Each of these tanks was supplied with crude sewage from the mains
by a l½-inch iron pipe which dipped into the tank to a depth of 7 feet from the top.
* It must be remembered that the dry coke would itself absorb liquid.