Chlorination of Water Part 1

Chlorination of Water.

by Joseph Race.

PREFACE

No apology is necessary for the publication of a book on the chlorination of water. This method of treatment, practically unknown fifteen years ago, has advanced in popularity during the last decade in a most remarkable manner, and in 1918 over forty millions of people are being supplied with chlorinated water.

It may justifiably be said that no other sanitary measure has accomplished so much at so small a cost; and that civilization owes a deep debt of grat.i.tude to the pioneers in munic.i.p.al water chlorination: Dr. A. C. Houston in England, and Mr. G. A. Johnson and Dr. Leal in America.

In this volume I have endeavoured to collect and correlate the information hitherto scattered in various journals and treatises and to present it in a comprehensible manner. The various aspects and methods of chlorination are discussed and suggestions have been made which, I hope, will stimulate research work in this fertile field of science.

I wish to acknowledge my indebtedness to the engineering staff of the Ottawa Water Works Department and to Lieut. W. M. Bryce for the preparation of diagrams.

JOSEPH RACE.

OTTAWA, ONT.,

April, 1918.

CHLORINATION OF WATER

CHAPTER I

HISTORICAL

Chlorine, although one of the most widely distributed elements known to chemists, is never found in the free condition in nature; it exists in enormous quant.i.ties in combination with sodium, pota.s.sium, calcium, magnesium, etc. As sodium chloride, common salt, it occurs in practically inexhaustible quant.i.ties in sea water together with smaller quant.i.ties of other chlorides. In mineral form, enormous deposits of sodium chloride are found in Galicia, Transylvania, Spain, in England (particularly in Cheshire), and in sections of North America. The most important deposits of pota.s.sium chloride are those at Sta.s.sfurt, Germany, where it occurs either in the crystalline condition as sylvine or combined with magnesium chloride as carnallite.

Chlorine was discovered by the Swedish chemist Scheele in 1774, but he, like Lavoisier and his pupil Berthollet, who declared it an oxygenated muriatic acid, was unaware of the elemental nature of the new substance.

Sir Humphrey Davy investigated this body in 1810 and definitely proved it to be an element; Davy designated the element chlorine from the Greek [Greek: chloros] = green.

The first attempt to utilise chlorine, or its compounds, for bleaching purposes, appears to have been due to James Watt, who noticed the decolourising properties of chlorine during a visit to Berthollet. This attempt ended in failure because of the destructive effect on the fibres, but, in later trials, this was prevented by first absorbing the gas in a solution of fixed alkali. These experiments proved the possibility of bleaching by means of chlorine compounds but the high cost of soda made the process unprofitable, and it was not until Henry succeeded in preparing a combination with lime that could be reduced to a dry powder that this mode of chemical bleaching became a commercial success.

The manufacture of chloride of lime (hypochlorite of lime, bleaching powder, bleach) was taken up by Charles Tennant in 1799 at St. Rollox near Glasgow, and in 1800 about 50 tons were sold at a price of $680 (139) per ton.

Chlorine is produced as a by-product in the manufacture of soda by the Leblanc process, but until 1865, when the British Alkali Act stopped the discharge of hydrochloric acid vapours into the atmosphere, the development of the bleaching powder industry was not rapid. The hydrochloric acid that was formerly discharged into the air as a waste product afterwards became a valuable a.s.set that enabled the Leblanc process to successfully compete with the newer ammonia-soda process. In 1890 another compet.i.tor to the Leblanc process was introduced when caustic and chlorine were produced in Germany by electrolytic methods.

After the successful development of this method in Germany, it was taken up in the United States of America and in 1912 more than 30,000 electrical horse-power were daily used in this industry. In 1914 the almost complete cessation of exports of bleach from Europe raised the price, which attained phenomenal heights in 1916 (cf. page 125), and stimulated the production of bleach both in the U. S. A. and Canada.

TABLE I.--BLEACH STATISTICS. NORTH AMERICA

-------------+----------------------------+--------------------- Year. | Bleach Manufactured, | Selling Price | Short Tons. | Per 100 Lbs.

-------------+----------------------------+--------------------- 1904 | 19,000 | 1909 | 58,000 | 1914 | 155,000 | $1.63 1915 | 180,000[A] | 2.63 1916 | 230,000[A] | 6.56 1917 | 260,000[A] | 2.44 -------------+----------------------------+--------------------- [A] Estimated.

As a disinfectant, chlorine was first used about the year 1800 by de Morveau, in France, and by Cruikshank, in England, who prepared the gas by heating a mixture of hydrochloric acid and pota.s.sium bichromate or pyrolusite; this is essentially the same as the original mixture used by Scheele.

During the early part of the last century the efficacy of chlorine of lime as a disinfectant, and particularly as a deodourant, was well recognised and as early as 1854 an English Royal Commission used this substance for deodourising the sewage of London. A committee of the American Public Health a.s.sociation reported in 1885 that chloride of lime was the best disinfectant available when cost and efficiency were considered.

Eau de Javelle, first made by Percy at the Javelle works near Paris in 1792, is another chlorine compound that has enjoyed a considerable reputation as a disinfectant and deodouriser for over a century; it is essentially a mixture of sodium chloride and sodium hypochlorite.

The discovery of electrolytic hypochlorites dates back to 1859, when Watt found that chlorides of the fixed alkalies and alkaline earths yielded hypochlorites on being submitted to the action of an electrical current.

Until the middle of the last century disinfection was regarded as a process that arrested or prevented putrefactive changes but the nature of these changes was imperfectly comprehended and micro-organisms were not a.s.sociated with them.

In 1839 Theodor Schwann,[1] who might be regarded as the founder of the school of antiseptics, reported that "Fermentation is arrested by any influence capable of killing fungi, especially by heat, pota.s.sium a.r.s.eniate, etc...."; but his results were not accepted by the adherents of the theory of spontaneous generation and it was not until the publication of the work of Schroder and Dusch[2] that Schwann's views were even partially accepted. The final refutation to the spontaneous generation theory was given by the monumental researches of Pasteur who, in 1862, proved the possibility of preparing sterile culture media and demonstrated the manner in which they could be protected from contamination. Bacteria and other micro-organisms were shown to be responsible for the phenomena that had been attributed previously to the "oxygen of the air," and from this period the development of bacteriology as a science proceeded rapidly.

The next important step, from the public health standpoint, was the discovery by Koch, in 1876, that a specific bacterium (_B. anthracis_) was the cause of a specific disease in cattle (anthrax or splenic fever). In 1882 Koch made a further advance by developing a solid culture medium which permitted disinfectants and antiseptics to be studied quant.i.tatively with a greater degree of accuracy than had been possible previously.

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 quant.i.ties 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 faecal matter and a prolonged trial was given to it at Worthing in 1894. The report of Dupre 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 pa.s.sed 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 subst.i.tuted 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: quant.i.ties 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.

Other important work on this subject was carried out, in connection with the pollution of the Hooghly River, by a Bengal Government Commission in 1904; and by the State Board of Health of Ohio in co-operation with the Bureau of Plant Industry of the United States Department of Agriculture in 1907. The chlorination experiments of the latter were reported by Kellerman, Pratt, and Kimberly.[10]

The most valuable contribution to the disinfection of sewage was that of Phelps,[11] who critically examined the work of previous experimenters and directed attention to the unnecessary stringent standards adopted in European practice. His work at Boston in 1906, at Red Bank, N. J., and at Baltimore in 1907, demonstrated in an indubitable manner the economic possibilities of sewage chlorination. The dosages necessary for crude sewage and filter effluents were indicated and also the necessary contact periods. This work marks the commencement of a new era in sanitary science.

The first occasion on which chlorine compounds were first used for the disinfection of water cannot be definitely ascertained. It has been stated to the author that bleach was used for treating wells as early as 1850 but this treatment was apparently made without definite knowledge of the destruction of micro-organisms.

In 1897, Sims Woodhead employed bleach solutions for the sterilisation of the distribution mains at Maidstone, Kent, subsequent to an epidemic of typhoid fever.

The credit for the first systematic use of chlorine in water disinfection is due to A. C. Houston with whom McGowan was a.s.sociated in the work carried out at Lincoln in 1904-1905.[12] The reservoirs, filters, and distribution system, owing to flood conditions, became infected with typhoid bacilli which caused a severe epidemic amongst the consumers. The storage and purifications works were thoroughly treated with a solution of "chloros" (sodium hypochlorite containing approximately 10 per cent of available chlorine) which was regulated to give an approximate dosage of 1 part per million. The bacteriological results were entirely satisfactory but many complaints were received that the treatment had imparted a mawkish taste to the water. This was attributed to the action of the alkaline chloros on the organic impurities in the water. It was also stated that the water injured plants, fish, and birds and extracted abnormal amounts of tannin from tea but no substantiating evidence was produced in support of these complaints. Houston made a continuous physiological test of the effect of the chlorinated water on small fish by suspending a cage of gold fish in the filter effluent chamber and also proved that the treatment had no appreciable effect on the plumbo-solvency of the supply.

Nesfield, of the Indian Army Medical Service,[13] reported in 1903 the results of numerous experiments on the destruction of pathogenic organisms by chlorine compounds and suggested their use in military work to prevent a recurrence of the appalling loss of life from water-borne diseases (especially enteric fever) such as took place during the Boer War. Nesfield proposed to use about 100 p.p.m. of available chlorine and to remove the excess after a contact period of 10 minutes. This work is especially interesting from the historical standpoint because it contains the first suggestion of the possibilities of compressed chlorine gas in steel cylinders.