The population supplied exclusively from the Lea by the East London Company is of a poorer class than that of the rest of London, and this may account for the slightly higher death-rate in this section. Aside from this the rate is remarkably uniform and shows no great difference between the section drinking ground-water only and those drinking filtered river-waters. The death-rate from typhoid fever is also very uniform and, although higher than that of some Continental cities with excellent water-supplies (Berlin, Vienna, Munich, Dresden), is very low—lower than in any American city of which I have records.
In this connection, it was shown by the Registrar-General that there is only a very small amount of typhoid fever on the watersheds of the Thames and Lea, so that the danger of infection of the water as distinct from pollution is less than would otherwise be the case. Thus for the seven years above mentioned the numbers of deaths from typhoid fever per million of population were only 105 and 120 on the watersheds of the Thames and the Lea respectively, as against 176 for the whole of England and Wales.
| LONDON FILTERS, 1896. | |||||||
|---|---|---|---|---|---|---|---|
| Twenty-sixth Annual Report of the Local Government Board, pages 206-213. | |||||||
| Company. | Amount of Storage Raw Water, Days. | Average Thickness of Sand, Feet. | Average Rate of Filtration. | Bacterial Efficiency. | |||
| Imperial Gallons per Square Foot per Hour. | Millions U. S. Gallons per Acre Daily. | Maximum. | Minimum. | Average. | |||
| Chelsea | 12.0 | 4.0 | 1.75 | 2.19 | 99.92 | 99.62 | 99.86 |
| West Middlesex | 5.6 | 2.75 | 1.25 | 1.56 | 99.94 | 91.48 | 99.79 |
| Southwark & Vauxhall | 4.1 | 2.5 | 1.5 | 1.88 | 100.00 | 84.33 | 97.77 |
| Grand Junction | 3.3 | 2.25 | 1.63 | 2.05 | 99.98 | 84.03 | 99.31 |
| Lambeth | 6.0 | 2.8 | 2.08 | 2.60 | 99.97 | 96.45 | 99.81 |
| New River | 2.2 | 4.4 | 1.89 | 2.37 | 100.00 | 77.14 | 99.07 |
| East London | 15.0 | 2.0 | 1.33 | 1.67 | 99.93 | 97.03 | 99.56 |
APPENDIX VI.
THE BERLIN WATER-WORKS.
The original works were built by an English company in 1856, and were sold to the city in 1873 for $7,200,000.
The water was taken from the river Spree at the Stralau Gate, which was then above, but is now surrounded by, the growing city. The water was always filtered, and the original filters remained in use until 1893, when they were supplanted by the new works at Lake Müggel. Soon after acquiring the works the city introduced water from wells by Lake Tegel as a supplementary supply, but much trouble was experienced from crenothrix, an organism growing in ground-waters containing iron, and in 1883 this supply was replaced by filtered water from Lake Tegel. With rapidly-increasing pollution of the Spree at Stralau the purity of this source was questioned, and in 1893 it was abandoned (although still held as a reserve in case of urgent necessity), the supply now being taken from the river ten miles higher up, at Müggel.
The watershed of the Spree above Stralau, as I found by map measurement, is about 3800 square miles; the average rainfall is about 25 inches yearly. At extreme low water the river discharges 457 cubic feet per second, or 295 million gallons daily, and when in flood 5700 cubic feet per second may be discharged. The city is allowed by law to take 46 million gallons daily for water-supply, and this quantity can be drawn either at Stralau or at Müggel.
Above Stralau the river is polluted by numerous manufactories and washing establishments, and by the effluent from a considerable part of the city’s extensive sewage farms. The shipping on this part of the river also is heavy, and sewage from the boats is discharged directly into the river. The average number of bacteria in the Spree at this point is something over ten thousand per cubic centimeter, and 99.6 per cent of them were removed by the filters in 1893.
The watershed of the Spree above the new water-works at Müggel I found by map measurement to be 2800 square miles, and the low water-discharge is said to be 269 million gallons daily. The river at this point flows through Lake Müggel, which forms a natural sedimentation-basin, and the raw water is quite clear except in windy weather.
There were 16 towns on the watershed with populations above 2000 each in 1890, and an aggregate population of 132,000, which does not include the population of the smaller places or country districts. None of these places purify their sewage so far as they have any. Fürstenwalde with a population of 12,935, and 22 miles above Müggel, has surface sewers discharging directly into the river. Above Fürstenwalde the river runs through numerous lakes which probably remove the effect of the pollution from the more distant cities. There is considerable shipping on the river for some miles above Fürstenwalde (which forms a section of the Friedrich Wilhelm Canal), but hardly any between Müggel and Fürstenwalde. The raw water at Müggel contains two or three hundred bacteria per cubic centimeter, and is thus a comparatively pure water before filtration. It is slightly peaty and the filtered water has a light straw color.