As the suburban population around London, England, grew and occupied the drainage area from which the London water supply was obtained, just in such proportion was the water supply polluted, and London was early forced to devise measures for purifying an already polluted water; so it is that as early as 1839 London was filtering part of the water derived from surface sources, and so successful were the early attempts that at the present time although London is supplied with water by eight separate water companies, all of the water used within its confines which is derived from rivers, lakes or streams, is filtered before delivery into the distributing mains. Europe was not slow to grasp the value of filtration, and at the present time most cities of importance in Continental Europe have slow sand filters, while America, or at least the United States, which is reputed to adopt almost immediately anything which possesses merit, had constructed no filters as late as 1880, and to-day can number but few. A striking illustration of the value of filtration for sterilizing an infected water supply can be instanced in the cholera epidemic of Hamburg, Germany.
MAP
showing the Locations of the Cases of Cholera adjacent to the Boundary between HAMBURG and ALTONA in the Epidemic of 1892
Boundary line indicated by line of dashes.
Cases of cholera by solid circles.
Cases of cholera imported from Hamburg by circles.
Water mains in Hamburg streets by black lines.
On the river Elbe, some miles from the sea, there are three cities adjoining and forming in appearance one large city of 800,000 inhabitants, the combined sewage of which is discharged into the river Elbe. The water supply to the city of Hamburg, a free German city, with a population of 640,400, is derived from the Elbe above where the sewage is discharged into the river but not sufficiently far away to escape contamination from a recision of polluted water at flood tide. This water after some imperfect sedimentation passes direct to the consumer without filtration. The supply of water to Wandsbeck, a city of 20,000 population, is obtained from a lake which is unexposed to contamination and is filtered before being delivered to the mains. The supply to Altona, on the other hand, a Prussian city of 143,000 inhabitants, is obtained from the river Elbe at a point about 8 miles below where it receives the combined sewage of the three cities, with their population of over 800,000. It will thus be seen that the source of supply to Altona is the worst of the three. This most grossly polluted supply, however, is filtered with exceeding care before delivery to the consumers, and to this fact is attributed the freedom from cholera that visited Hamburg in 1892. The story is well told by Dr. Thorne, medical officer of the London Local Government Board.[9]
"The different behavior of Hamburg and Altona as regards cholera is extremely interesting. The two towns adjoin; they are practically one city. The division between the two is no more obvious than that between two densely peopled London parishes, and yet a spot map indicating the houses which were attacked with cholera, which was shown to me by Professor Koch, points out clearly that whereas the disease prevailed in epidemic form on the Hamburg side of the boundary line, that line running in and out among the streets and houses and at times passing diagonally through the houses themselves, formed the limit beyond which the epidemic, as such, did not extend. The dots on one side of the dividing line were proof of the epidemicity of cholera in Hamburg, their comparative absence on the Altona side of it was proof of the absence of the epidemic in Altona. To use Professor Koch's own words: 'Cholera in Hamburg went right up to the boundary of Altona and then stopped. In one street, which for a long way forms the boundary, there was cholera on the Hamburg side, whereas on the Altona side was free from it, and yet there was one detectable difference, and one only, between the two adjacent areas—they had different water services.' Professor Koch has collected certain proofs which he regards as crucial on this point, and Dr. Reincke has supplied me with a small plan in support of the contention. At one point close to and on the Hamburg side of the boundary line between Hamburg and Altona, is a large yard, known as the Hamburger-Platz. It contains two rows of large and lofty dwellings, containing 72 separate tenements and some 400 people, belonging almost wholly to those classes who suffered most from cholera elsewhere in Hamburg. But while cholera is shown by the spot map to have prevailed all around, not a single case occurred among the many residents of this court during the whole epidemic. And why? Professor Koch explains that owing to local difficulties, water from the Hamburg mains could not easily be obtained for the dwellings in question, and hence a supply had been laid in from one of the Altona mains in an adjacent street. This was the only part of Hamburg which received Altona water, and I am informed that it was the only spot in Hamburg in which was aggregated a population of the class in question, which escaped the cholera. At the date of my visit to Hamburg, a notice board was affixed at the entrance to this court. It stated that certain tenements were to let; but, above all, in large type, and as an inducement to intending tenants, was the announcement that the court was not only within the jurisdiction of Hamburg, with the privileges still attaching to the old Hanseatic cities, but that it had a supply of Altona water.