Since 1845, when Semmelweiss succeeded in stamping out puerperal fever in Vienna, where it had been so long established as to be endemic, chlorine has been very generally employed in sanitary work and the conditions necessary for obtaining successful results have been partially elucidated. Baxter was the first to state that the disinfecting action depended more upon the nature of the pabulum than upon the specific organism present and this was confirmed later by Kuhn, Bucholtz, and Haberkorn. The latter found that urine consumed large quantities of chlorine before any disinfection occurred.
One of the earliest preparations used in sanitary work was an electrolysed sea water, usually known as Hermite Fluid. This was introduced by M. Hermite in 1889 and was employed for domestic purposes and for flushing sewers and latrines. It was used at Brest for the dissolution of fæcal matter and a prolonged trial was given to it at Worthing in 1894. The report of Dupré and Klein, who conducted the bacteriological examinations, was against the process, but Ruffer and Roscoe reported more favourably and further trials were carried out at Havre, l’Orient, and Nice. The Lancet (May 26, 1894) reported at length upon the Worthing experiments: it was found that during the electrolysis of the sea water, the magnesium chloride was also partially converted into hypochlorite, which then dissociated into magnesium hydrate and hypochlorous acid; the former deposited in the electrolyser and left the solution acid and unstable; urine was found to act upon it at once with a consequent loss in strength of over 50 per cent.
Another electrolytic method was that of Webster,[3] who installed an experimental plant at Crossness, near London, in 1889. A low-tension direct current was passed between iron electrodes placed in the sewage and although the process was largely one of chemical precipitation, Webster noted the disinfecting value of the hypochlorite formed from the chlorides normally present in the sewage. He also directed the attention of sanitarians to the possibility of using sea water as a cheap source of chlorides and a plant based on this principle was erected in Bradford in 1890 and reported upon by McLintock.[4]
Strong salt solutions were substituted for sea water by Woolf and the product was commercially known as “Electrozone.” A plant of this description was installed at Brewster, N. Y., in 1893[5] for chlorinating the sewage from a small group of houses. The sewage was discharged into a small creek which polluted Croton Lake. Successful results led to a similar treatment near Tonetta Creek.[6] This was apparently the first occasion on which the specific object was the destruction of bacteria.
Electrozone was used at Maidenhead, on the Thames, in 1897 and the installation was reported upon by Robinson, Kanthack, and Rideal in 1898. Kanthack found that a dosage 3-3.6 p.p.m. reduced the organisms in a sewage effluent to 10-50 per c.cm. whilst Rideal found that about 18 p.p.m. of chlorine produced a condition of sterility in 1 c.cm.
Chloride of lime had previously been used in the London sewage as a deodourant by Dibden in 1884 but the treatment was not successful and was abandoned in favour of other oxidisers.
During the last decade of the twentieth century the use of bleach for the disinfection of both sewage and water received the attention of many well-known German sanitarians and many important results were obtained.
In the earlier experiments made at Hamburg, Proskauer and Elsner[7] obtained satisfactory results with 3-4 p.p.m. of chlorine on a clarified sewage with 10 minutes contact. Dunbar and Zirn (ibid.) used crude sewage and found that 17 p.p.m. of available chlorine were required to remove B. typhosus and cholera vibria with a contact period of two hours. A striking feature of all the German work on chlorination is the very high degree of purification aimed at: quantities as large as one litre were tested for specific organisms and in many of the experiments with sewage B. coli was found to be absent from a considerable percentage of the samples.
The importance of previously removing suspended matter, which could not be penetrated by the germicide, was emphasised by Schwartz[8] although it had been previously noted by Schumacher.
At the Royal Testing Station in Berlin, numerous experiments on sewage chlorination were made by Kranejuhl and Kurpjuivut.[9] The results were judged by the B. coli content, which was taken as an index of pathogenicity because this typical intestinal bacillus was found to be more frequent and less viable than the majority of the pathogenic organisms.