CHAPTER X

RESULTS OBTAINED

The object of adding chlorine or chlorine compounds to water is for the purpose of destroying any pathogenic organisms that may be present. In a few instances some collateral advantages are also obtained but, in general, no other object is aimed at or secured.

Chlorination does not change the physical appearance of water; it does not reduce or increase the turbidity nor does it decrease the colour in an appreciable degree.

The chemical composition is also practically unaltered. When bleach is used there is a proportionate increase in the hardness but the amount is usually trifling and is without significance. During 1916 when the Ottawa supply was entirely treated with bleach at the rate of 2.7 parts per million (0.92 p.p.m. of available chlorine) the average increase in the total hardness as determined by the soap method was 2.5 parts per million.

When chlorine is added to prefiltered water, as an adjunct to filtration, an increase in the number of gallons filtered per run has been noted at some plants. This increase is not so great with rapid as with slow sand filters but in some instances it has led to appreciable economies.

Walden and Powell[1] of Baltimore, found that the addition of a quantity of bleach equal to approximately 0.50 p.p.m. of available chlorine enabled the alum to be reduced from 0.87 to 0.58 grain per gallon. The percentage of water used in washing the filters was also reduced, from 4.1 per cent to 2.9 per cent, whilst the filter runs were increased on the average by one hour and ten minutes. The net saving in coagulant alone amounted to 30 cents per million gallons.

Clark and De Gage[2] found that the use of smaller amounts of coagulant during the period of combined disinfection and coagulation resulted in an increase of nearly 25 per cent in the quantity of water passed through the filter between washings, and also in a material reduction of the cost of chemicals, which averaged $2.62 per million gallons for combined disinfection and coagulation as against $4.86 for coagulation alone. The water used in these experiments was obtained from the Merrimac River at Lawrence.

The effect of hypochlorite on the reduction of algæ growths on slow sand filters was first noticed by Houston during the treatment of the Lincoln supply in 1905. Two open service reservoirs were fed with treated water and were themselves dosed from time to time. "Previous to 1905 they developed seasonally most abundant growths, but during the hypochlorite treatment it was noticed that they remained bright, clear, and remarkably free from growths" (Houston[3]).

Ellms,[4] of Cincinnati, has also noted the effect of hypochlorite on algæ. When the bleach was added to the coagulated water the destruction of the plankton was not as satisfactory as had been anticipated and it was found that large doses destroyed the coating of the sand particles and rendered the filters less efficient. The use of bleach in the filtered water basin was more successful and cleared it of troublesome growths.

In 1916, during the treatment of the London Supply with bleach (dosage 0.5 p.p.m. of available chlorine), Houston made further observations on this point. The Thames water, taken at Staines, had previously been stored for considerable periods in reservoirs, but this necessitated lifting the water by pumps which consumed large quantities of coal that were urgently needed for national purposes. As a war measure, the storage was eliminated and the water treated with hypochlorite at Staines and allowed to flow by gravitation to the various works where the slow sand filters are situated. The treatment resulted in a marked reduction in the growths of algæ, the reduction in the area of filters cleaned in 1916 (June to September) as compared with 1915 being as follows:

Percentage Filter Works. Reduction (Approximate). Grand Junction (Hampton) 6 Grand Junction (Kew) 43 East London (Sunbury) 30 Kempton Park 33 West Middlesex 56

A portion of this reduction can probably be attributed to the elimination of storage.

Chlorination, by decreasing the load on filter beds, has enabled the rate of filtration to be increased in some cases. This increased capacity, which would otherwise have necessitated additional filter units, has been obtained without any further capital outlay. At Pittsburg (Johnson[5]) the rate of filtration, after cleaning, was increased 250,000 gallons each hour until the normal rate was reached; restored beds were maintained at a 250,000 gallon rate for one week. After the introduction of chlorination it was found possible to increase the rates more rapidly without adversely affecting the purity of the mixed filter affluents.

_Hygienic Results._ Evidence as to the actual reduction of the number of such pathogenic germs as _B. typhosus_ in water supplies by chlorination is most readily found in the death rates from typhoid fever in cities that have no other means of water purification. In some cases this evidence is necessarily of a circumstantial nature; in others it is definite and conclusive.

Some of the earlier results of the effect of chlorination on typhoid morbidity and mortality rates were compiled by Jennings[6] and others have been published by Longley.[7] These data have been brought up to date in Table XXXI and other statistics added.

TABLE XXXI.--EFFECT OF CHLORINATION ON TYPHOID RATES

AVERAGE TYPHOID DEATH RATE PER 100,000 POPULATION

----------------+-------------+--------------+--------------+----------- City. | Commenced | BEFORE USING.| AFTER USING. | |Chlorination.+-------+------+-------+------+ Percentage | |Period.|Rate. |Period.|Rate. | Reduction. ----------------+-------------+-------+------+-------+------+----------- Baltimore |June 1911 |1900-10| 35.2 |1912-15| 22.2 | 36 Cleveland |Sept. 1911 |1900-10| 35.5 |1912-16| 8.2 | 77 Des Moines |Dec. 1910 |1905-10| 22.7 |1911-13| 13.4 | 41 Erie |Mar. 1911 |1906-10| 50.6 |1912-14| 15.0 | 70 Evanston, Ill. |Dec. 1911 |1908-11| 29.0 |1912-13| 14.5 | 50 Jersey City |Sept. 1908 |1900-17| 18.7 |1909-16| 8.4 | 55 Kansas City, Mo.|Jan. 1911 |1900-10| 42.5 |1911-16| 14.2 | 66 Omaha, Neb. |May 1910 |1900-09| 22.5 |1911-16| 10.6 | 53 Trenton |Dec. 1911 |1907-11| 46.0 |1911-14| 28.7 | 35 Montreal |Feb. 1910 |1906-10| 40.0 |1911-16| 25.0 | 37 Toronto |Apr. 1911 |1906-10| 31.2 |1912-16| 7.8 | 75 Ottawa |Sept. 1912 |1906-10| 34.0 |1913-17| 17.0 | 50 ----------------+-------------+-------+------+-------+------+-----------

The figures given in this table show the effect of chlorination only; no other form of purification was used during the periods given, except at Toronto where a portion of the supply has been subjected to filtration.

It will be seen that since chlorination was adopted the typhoid death rates have been reduced by approximately 50 per cent and that the averages for the period after treatment are almost invariably less than 20 per 100,000, a figure that a few years ago was regarded as satisfactory. The average death rate for the last available year is 11 per 100,000, a result that is even more satisfactory and exceeds the anticipations of the most optimistic of sanitarians.

A portion of the reduction in the typhoid rates is no doubt due to improvements in general sanitary conditions but the reduction is much greater than can be accounted for in that manner alone and in many cases there was a sharp decline immediately following the commencement of chlorination.

In a few instances there is evidence that chlorination has reduced the typhoid rates of cities previously supplied with filtered water. Diagram X, drawn from data supplied by Dr. West, of the Torresdale Filtration Plant, shows the effect of disinfecting the filter effluents at Philadelphia.

During the years 1909-10-11, when practically the whole of the city supply was filtered, the average typhoid death rate was 18, but when the water was also chlorinated, in 1914-15-16, the rate was only 7, a reduction of 61 per cent.

The figures in Table XXXII show that the Torresdale filters, during 1915-16 were unable to adequately purify the water and that chlorination was necessary.

TABLE XXXII.--CHLORINATION OF FILTER EFFLUENTS

(TORRESDALE)

----+---------+---------+----------+---------------------------------- | | | | BACTERIA PER CUBIC CENTIMETER. | Oxygen | | +-----------------+---------------- |Consumed.| Colour. |Turbidity.| Untreated. | Treated. | | | +---------+-------+---------+------ | | | |Gelatine.| Agar. |Gelatine.| Agar. ----+---------+---------+----------+---------+-------+---------+------ 1915| 1.70 | 12 | 0.6 | 141 | 30 | 28 | 14 1916| 1.90 | 12 | Nil. | 88 | 23 | 38 | 11 ====+=========+=========+==========+=========+=======+=========+====== | _B. coli communis_ | | Per Cent Positive Tests. | +----------------------+-------------------------+ | Untreated. | Treated. | Added Chlorine +----------+-----------+------------+------------+ Parts Per |10 c.cms. | 1 c.cm. | 10 c.cms. | 1 c.cm. | Million. ----+----------+-----------+------------+------------+---------------- 1915| 66 | 24 | 5 | 0.3 | 0.18 1916| 49 | 16 | 7.4 | 1.9 | 0.15 ----+----------+-----------+------------+------------+----------------

In Diagram XI the typhoid death rates of Columbus, Ohio, and New Orleans are shown to exemplify conditions that have not been improved by chlorination. The endemic condition of typhoid in Columbus was brought to an abrupt conclusion by the installation and operation of the softening and filter plant in September, 1908, and no further reduction followed the introduction of chlorination in December, 1909.

In New Orleans the typhoid rate decreased on the inception of the new water works system in 1909 and again after the installation of the Carrollton filters in 1912. The product of the filtration plants has always been above suspicion but aftergrowths occasionally developed and the bacterial count then exceeded the United States Treasury standard. To overcome this difficulty, hypochlorite was used in 1915, but, as was anticipated, it had no effect on the typhoid rate. The high rate in New Orleans is largely due to outside cases received for hospital treatment and to other circumstances beyond the control of the water and sewerage department.

In all the examples previously cited, the evidence as to the effect of chlorination on typhoid mortality rates is circumstantial but, taken as a whole, it is fairly conclusive. In the examples to be considered next the evidence is more direct.

One of the most conclusive experiments as to the beneficial effect of chlorination is that reported by Young[8] of Chicago. The water supply of Chicago was obtained from Lake Michigan by means of intake pipes and pumped to various parts of the city. The distribution system was divided into four districts and, although there was a certain amount of mixing along the borders, the water supplied to each district was substantially separate. The rapid and progressive decline in the typhoid rate of Chicago (from 19 in 1900 to 10.8 in 1911) subsequent to the diversion of the city sewage from the lake, led to the assumption that water-borne typhoid had ceased to be of any moment. Early in 1912, however, permission was secured to chlorinate the supply of one district (No. 1) and the treatment was continued until December when the solutions commenced to freeze. Diagram XII shows the effect of the treatment on the autumnal increase in District No. 1 as compared with the other three districts. The autumnal increase was calculated from the excess of typhoid incidence for July to November inclusive, over that for February to June inclusive.

These results demonstrate in a most striking manner the beneficial effect of chlorination. The general conditions, with the exception of the raw water supply, were approximately the same in all four districts. Diagram XIII shows that the raw water supply of District No. 1 was slightly worse than any of the others, 21.8 per cent of the samples from District No. 1 containing _B. coli_ in 1 c.cm. as compared with 21.0 per cent in the most polluted supply of the other districts.

The results obtained at Ottawa are also conclusive. Following two epidemics of typhoid fever in 1911 and 1912, caused by breaks in the intake pipe, hypochlorite treatment was commenced and has been in continuous operation until February, 1917, when chloramine treatment was substituted. The dosage has been so regulated as to assure a high degree of purity at all times in the water delivered to the mains and as evidence of this it might be mentioned that the average _B. coli_ index (calculated by Phelps' method) for the years 1916 and 1917 was only 0.27 per 100 c.cms. The typhoid rates for the five years preceding the epidemic years and for a similar subsequent period are given in Diagram XIV.

The diagram shows that there has been a constant reduction in the city typhoid rate since the last severe epidemic with the exception of the year 1915. The high rate of that year was caused by a localised epidemic started by polluted well water and spread by flies from an unsewered area. This outbreak was the cause of about seven deaths registered during that year (population 100,000).

The objection might be raised that if the reduction of the typhoid rate were due to the water treatment, the decline should have been abrupt and not a gradual one. It is probable that there has been practically no water-borne typhoid in the city since chlorination was commenced but this fact is masked by cases from other sources. During 1911 and 1912 over 3,500 cases of typhoid were reported, of which an appreciable number would become carriers for various periods of time. As these carriers decreased the number of cases infected by them would also decrease and so account for a gradually declining death rate.

It might be further objected that the reduced typhoid rate is due to a general improvement in the sanitary conditions. If the death rate from causes other than typhoid can be regarded as a measure of the general sanitary conditions it is obvious from the data in Table XXXIII that the improvement in the typhoid rate is immeasurably greater than can be ascribed to that cause.

TABLE XXXIII.--DEATH RATES IN OTTAWA BEFORE AND AFTER CHLORINATION

--------------------------+-------------------+--------------------- | RATE PER 100,000 | PERCENTAGE Cause. +---------+---------+-----------+--------- | 1908-12 | 1913-17 | Reduction | Increase --------------------------+---------+---------+-----------+--------- Total[A] | 14.90 | 14.78 | 1.2 | ... Typhoid, total | 34[B] | 17 | 50.0 | ... Typhoid, city | 26[B] | 8 | 69.2 | ... Pneumonia | 100 | 107 | ... | 7.0 Tuberculosis | 133 | 138 | ... | 3.7 Diarrh[oe]a and Enteritis | 139 | 128 | 7.9 | ... under 2 years | | | | --------------------------+---------+---------+-----------+---------

[A] Rate per 1,000.

[B] 1906-10, epidemic years 1911-12 excluded.

One further objection might be made: that the raw water was not infected during 1913-17 or infected to a smaller extent than during the previous period. Attempts to isolate _B. typhosus_ from the raw water have invariably been futile but their presence in 1914 might be inferred from the fact that during the latter part of the summer of that year an epidemic of typhoid fever occurred at Aylmer, a village that discharges its sewage into the Ottawa River about six miles above the Ottawa intake. Hull, situated on the opposite bank of the river and having a population of 20,000, takes its water supply from the same channel that supplies Ottawa but at a point a few hundred feet further down stream. During November and December, 1914, some 200 cases of typhoid fever (incidence 1,000 per 100,000) occurred in Hull as compared with 28 in Ottawa. As the Ottawa intake is situated between the Hull intake and the outlet of the Aylmer sewer it is incredible that the Ottawa raw water was not also infected.

In 1916 a liquid chlorine plant was installed in Hull, but in 1917, owing to an accident, it was out of commission for a short period and at least 100 cases of fever developed during the following month. During the same period only two cases were reported in Ottawa and of these one was obviously contracted outside the city.

In view of the preceding facts it must be granted that the improvement in the typhoid rate of Ottawa can be definitely attributed to an improvement in the water supply caused by chlorination.

The efficacy of chlorination to prevent and check epidemics of water-borne typhoid has never been doubted. Innumerable instances could be cited in which the prompt treatment of large public supplies has promptly checked outbreaks that threatened to assume serious proportions and there is no doubt that the extremely low typhoid morbidity rate on the Western Front of the European battlefield is partially due to the extensive and rigorous chlorination measures that have been instigated. Prophylactic vaccination and the prompt isolation of typhoid carriers have largely contributed to the wonderful results obtained but due credit must also be given to the systematic purification and treatment of water supplies. Similar results have been obtained at training camps in Canada and in other countries by effective treatment with either liquid chlorine or hypochlorite.

Since the inception of water chlorination in America in 1908, the merit of the method has been very generally recognized throughout the Continent but was regarded with scepticism in Europe, except as a temporary expedient, until the results obtained by the military forces compelled more general recognition. Before the war, chlorination of water supplies in England was only practised in a few isolated and relatively unimportant instances; in 1917, practically the whole supply of London was chlorinated and at Worcester a similar treatment has been recommended to enable the slow sand filters to be operated at higher rates without reducing the quality of the water supplied to the consumers.

_Use and Abuse of Chlorine._ Inasmuch as chlorination has no beneficial effect on water except the reduction of the bacterial content it should be used for this purpose only and under such conditions as permit the operations to be under full control at all times. The supplies that can be most efficiently and safely treated are those that are relatively constant in chemical composition and bacterial pollution. Changes in volume can be dealt with by automatic apparatus but sudden changes in organic and bacterial content require a change of dosage that cannot be made by any mechanical appliance. Long experience and accurate meteorological records may in some cases enable those in charge of chlorination plants to anticipate changes in the conditions of the water supply, but it is always preferable to provide a positive method of preventing sudden changes by using chlorination merely as an adjunct to other processes of purification. Unpurified waters that are objectionable on account of their bacterial content only are very rare, as the cause that produces the bacterial pollution usually produces other conditions that are equally objectionable though not so dangerous to health. Sudden storms in summer, or sudden thaws in winter, usually cause large increments in turbidity accompanied by soil washings that often carry appreciable quantities of fæcal matter into surface water supplies. Lake supplies often suffer in the same manner and sewage, which during normal conditions is carried safely away from water intakes, obtains access to the supply. If the dosage is maintained at a level sufficiently high to meet these abnormal conditions, complaints as to taste and odour would ensue, and in general, such a practice is impossible. Some supplies have been chlorinated successfully for years but the principle of using chlorination as the first and last line of defence cannot be recommended. Success can only be obtained by eternal vigilance and the responsibility for results is more than water works officials should be called upon to assume.

Chlorination is an invaluable adjunct to other forms of water purification and it is not improbable that, in the future, filter plants will be designed to remove æsthetic objections at the lowest possible cost and that chlorination will be relied upon for bacterial reduction. Chlorination is the simplest, most economical, and efficient process by which the removal of bacteria can be accomplished and there is no valid reason why it should not be used for that purpose.

The popularity of this process has suffered through the efforts of over zealous enthusiasts who have been unable either to recognize its limitations or to appreciate the fact that a domestic water supply should be something more than a palatable liquid that does not contain pathogenic organisms. Every system of water purification has its limited sphere of utility and chlorination is no exception to the rule.

BIBLIOGRAPHY

[1] Weldon and Powell. Eng. Rec., 1910, =61=, 621.

[2] Clark and De Gage, 41st Annual Rpt. Mass. State B. of H. 1910.

[3] Houston. 12th Research Rpt. Metropolitan Water Board, London.

[4] Ellms. Eng. Rec., 1911, =63=, 388.

[5] Johnson. Eng. Rec., 1911, =64=, No. 16.

[6] Jennings. 8th Inter. Congr. Appl. Chem., =26=, 215.

[7] Longley. J. Amer. Waterworks Assoc., 1915, =2=, 679.

[8] Young. J. Amer. Public Health Assoc., 1914, =4=, 310.

APPENDIX

ESTIMATION OF CHLORINE IN CHLORINATED WATERS

REAGENTS. 1. Tolidine solution. One gram of _o_-tolidine, purified by recrystallization from alcohol, is dissolved in 1 litre of 10 per cent hydrochloric acid.

2. Copper sulphate solution. Dissolve 1.5 grams of copper sulphate and 1 c.cm. of concentrated sulphuric acid in distilled water and dilute the solution to 100 c.cms.

3. Potassium bichromate solution. Dissolve 0.025 gram of potassium bichromate and 0.1 c.cm. of concentrated sulphuric acid in distilled water and dilute the solution to 100 c.cms.

PROCEDURE. Mix 1 c.cm. of the tolidine reagent with 100 c.cms. of the sample in a Nessler tube and allow the solution to stand at least five minutes. Small amounts of free chlorine give a yellow and larger amounts an orange colour.

For quantitative determination compare the colour with that of standards in similar tubes prepared from the solutions of copper sulphate and potassium bichromate. The amounts of solution for various standards are indicated in the following table:

PREPARATION OF PERMANENT STANDARDS FOR CONTENT OF CHLORINE

--------------------+-------------------+----------------------- Chlorine. | Solution of | Solution of | Copper Sulphate. | Potassium Bichromate. Parts per million. | c.cms. | c.cms. --------------------+-------------------+----------------------- 0.01 | 0.0 | 0.8 .02 | 0.0 | 2.1 .03 | 0.0 | 3.2 .04 | 0.0 | 4.3 .05 | 0.4 | 5.5 .06 | 0.8 | 6.6 .07 | 1.2 | 7.5 .08 | 1.5 | 8.7 .09 | 1.7 | 9.0 .10 | 1.8 | 10.0 .20 | 1.9 | 20.0 .30 | 1.9 | 30.0 .40 | 2.0 | 38.0 .50 | 2.0 | 45.0 --------------------+-------------------+-----------------------

NAME INDEX

A Adams, 66, 82

B Bassenge, 9 Baxter, 4 Berge, 9 Berthollet, 1 Bevan, 29 Bonjean, 36 Bray, 24 Breteau, 26 Bucholtz, 5

C Catlett, 99 Clark, 53, 133 Comte, 47 Cross, 29 Cruikshank, 3

D Dakin, 22, 28, 129 Darnall, 89 Davy, 1 DeGage, 53, 133 DeMorveau, 3 Dibden, 6 Diénert, 48 Dienheim-Brochoki, 105 Dowell, 24 Dunbar, 6 Dunham, 129 Dupré, 5 Dusch, 4

E Ellms, 34, 83, 84, 133 Elmanovitsch, 36 Elsner, 6 Evans, 84

F Faraday, 103 Fischer, 16 Forcrand, 103 Fuller, G. W., 11

G Gascard, 47 Griffen, 17, 79

H Haberkorn, 5 Hale, 80, 100 Harrington, 34, 65 Hauser, 83, 84 Hedallen, 17, 79 Heise, 36 Henry, 2 Hermite, 5 Hewlett, 9 Hooker, 72 Horrocks, 48 Houston, 8, 59, 71, 133 Hsu, 21

J Jackson, 91, 99 Jakowkin, 26 Jennings, 135 Johnson, 11, 134 Jordan, H. E., 57

K Kanthack, 6 Kauffman, 9 Kellerman, 7 Kershaw, 107 Kienle, 65, 66, 90, 99 Kimberly, 7 Klein, 5 Koch, 4 Kolessnikoff, 16 Kranejuhl, 7 Kuhn, 5 Kurpjuivat, 7

L Landolt, 105 Langar, 10 Laroche, 47 Lavoisier, 1, 15 Leal, 16 Lehmann, 101 LeRoy, 83 Letton, 64 Longley, 43, 135 Lunge, 105 Lyon, 24

M Marshall, 102 Massy, 48 Meadows, 112, 114 McCrady, 130 McGowan, 8 McLintock, 5 Mohler, 31 Mohr, 79 Moor, 9 Muspratt, 126

N Nesfield, 8, 89 Nissen, 30 Norton, 21 Novey, 23 Noyes, 24

O Ornstein, 90 Orticoni, 36

P Pedler, 103 Percy, 3 Pettenkofer, 101 Phelps, 7, 17, 82 Pitcher, 112 Plucker, 10 Powell, 132 Pratt, 7 Proskauer, 6, 16

R Rabs, 110 Race, 36, 110, 116 Raschig, 115 Rickard, 108 Rideal, E. K., 84 Rideal, S., 6, 9, 21, 22, 60, 115, 116 Roscoe, 5 Roozeboom, 103 Rouquette, 36 Ruffer, 5

S Sandman, 56 Scheele, 1, 15 Schroder, 4 Schuder, 10 Schumacher, 7 Schumburg, 10 Schwann, 4 Schwartz, 7 Semmelweiss, 4 Sickenberger, 9 Smeeton, 53 Smith, 126

T Tennant, 2 Thomas, 53, 56 Thresh, 87 Tiernan, 92 Tolman, 111 Traube, 9

V Valeski, 36 Von Loan, 90

W Walden, 132 Walker, 87 Wallace, 92 Wallis, 83 Warouzoff, 16 Watt, 2, 3, 15, 106 Webster, 5, 105 Wesbrook, 31, 44, 53 West, 91, 99, 136 Whittaker, 31 Winkler, 84 Winogradoff, 16 Winslow, 110 Woodhead, 7 Woolf, 5

Y Young, 138

Z Zirn, 6

SUBJECT INDEX

A Absorption of chlorine by water, 35 Abuse of chlorination, 144 Acids, effect of, 19, 21 Action of chlorine, 16 Admixture, effect of, 39 Aftergrowths, 55 accelerated growth, 58 _B. coli_ in, 57 effect of liquid chlorine, 99 views as to nature of, 56 Algæ, effect of chlorine on, 133 Alkalies, effect of, 19, 20 Allen-Moore cell, 111 Ammonia, and chlorine, 24 and sodium hypochlorite, 114 effect on bleach, 21 effect on oxidising action, 21 soda process, 2 Antichlors, 86 Antiseptics, early work on, 3 chlorine as an, 50 Application of chlorine, point of, 43 Auto-suggestion, 62

B _B. choleræ_ suis, 31 _B. cloacæ_, 31 _B. coli_, aftergrowths, 57 in sewage, 6, 7 in water, 9, 28, 31 standard, 46 viability of, 52, 55 _B. cuticularis_, 53 _B. fæcalis alkaligenes_, 31 _B. enteritidis_, 31 _B. enteritidis sporogenes_, 53 _B. lactis ærogenes_, 31 _B. subtilis_, 53 _B. tetani_, 9 _B. typhosus_, 9, 10, 30, 31 Bacteria surviving chlorination, 50 aftergrowths, 55 nature of, 53 spores, 57 Benzidine, 83 Bleach, analysis of solution, 79 as deodourant, 3, 6 as sewage disinfectant, 6, 7 at Adrian, 11 at Boonton, 11, 16 at Bubbly Creek, 11 composition, 14 decomposition of, 25 discovery, 2 germicidal velocity, 20, 21 hydrolysis, 18, 19 production, 3 stability of, 17 toxic action, 22 treatment, 72 control of, 78 cost, 86 dosage regulation, 75 in France, 78 losses in, 81 mixing tank, 73 plant design, 72 storage tank, 75 Brest experiments, 5

C Carnallite, 1 Chicago, typhoid rate, 138 Chloramine, 114 at Denver, 124, 126 at Ottawa, 28, 116 contact period, 123 cost of, 124 decomposition of, 126 experimental results, 119 germicidal power, 116 operation of process, 126 plant design, 120 preparation of, 115 ratio of chlorine and ammonia, 116, 122 tastes and odours, 28, 64, 117 toxic action, 22, 29 Chlorides, effect of, 20 Chlorine, and ammonia, 24, 25 discovery of, 1 disinfection, effect of pabulum, 4 general reactions, 28 hydrate, 103 detection of, 81 effect on flowers, 68 estimation of, 81 in sanitary work, 4 medicinal dose, 67 oxygen equivalent, 23 liquid, 89 advantages of, 97 cost of treatment, 101 disadvantages of, 101 germicidal efficiency, 99 machines, 89 peroxide, 9 water, 102 corrosion of pipes, 69 damage to seeds, 68 decomposition of, 15 heat of formation, 27 Chlorometer, 84 Chloros, 8 Chlorozone, 105 Colour, effect on dosage, 33 Columbus, typhoid rates, 137 Complaints, 62 Contact period, effect on dosage, 44 effect on taste, 43 usual practice, 45 Cost of bleach plant, 85 bleach treatment, 86 liquid chlorine treatment, 101 Crossness experiments, 5

D Dayton cell, 107 DeChlor filters, 87 Denver, chloramine treatment, 124, 126 Dichloramine, 128 Disinfectants, 50 Disinfection, early views of, 3 Dosage, 30 determination of, 46 effect of, admixture, 39 colour, 33 contact period, 43 initial contamination, 32 light, 45 oxidisable matter, 32 standard of purity, 30, 32 temperature, 34, 36 turbidity, 45 for military work, 48 regulation of bleach, 75 relation to oxygen absorbed, 36 tanks, 75

E Eau de Javelle, 3, 47 Electrical conductivity of treated water, 70 Electrolysed sea water, 5 Electrolytic hypochlorite, 2, 104 Bradford, 5 Brest, 5 Brewster, 6, 105 cost of, 113 Electrolytic hydrochlorite, Crossness, 5 discovery of, 3 diaphragm cells, 110 early use of, 5 efficiency of, 109 Havre, 5 non-diaphragm cells, 106 Electrozone, Brewster, 6 Maidenhead, 6 Tonetta Creek, 6

F Filter effluents, chlorination of, 34 Filters, effect on beds, 60 effect on runs, 132 Fish, effect on, 8, 67, 68

G Germicidal velocity, effect of acids, 21 alkalies, 20 ammonia, 21 chlorides, 20 Guildford, chlorination at, 9

H Haas and Oettel cell, 108 Halazone, 128 Hardness, effect of chlorine on, 132 Havre experiments, 5 Hermite fluid, 5 Hexamethyl-_p_-aminotriphenylmethane, 83 Historical, 1 Hooghly River, 7 Hydrazine, 126 Hydrogen peroxide, 24 Hydrolysis of hypochlorites, effect of, acids, 19 alkalies, 19 chlorides, 20 Hygienic results, 134 Hypochlorous acid, 17 decomposition of, 24, 25, 26 hydrolytic constant, 18

I Initial contamination, effect on dosage, 32 Intestinal organisms, viability of, 52 Iodoform taste, 65 Iron salts, effect on dosage, 33

J Jersey City, court case, 11, 16

K Kellner cell, 108

L Labarraque solution, 105 Leavitt-Jackson machine, 91 Leblanc process, 2 Light, effect on dosage, 45 Lincoln, chlorination at, 8, 59 Liquid chlorine, advantages of, 97 and tastes, 65 effect of temperature on, 95 machines, 89 dry feed, 94 E. B. G. Co., 91 Leavitt-Jackson, 91 operation of, 95 Wallace and Tiernan, 92 L'Orient, experiments at, 5

M M. agilis, 53 Maidstone, use of bleach at, 8 Margin of safety for taste and odour, 64 Material for bleach plants, 74 Military work, bleach method for, 78 chlorine water, 103 dosage for, 47, 48, 78 early European, 10 liquid chlorine, 102 typhoid reduction, 143 use of chlorine in, 8 Mixing tank for bleach, 73 Moisture, effect on chlorine gas, 16 Montreal, dosage at, 34 electrolytic cells, 112

N Nascent oxygen hypothesis, 17 Nelson cell, 111 Neva River, 36 New Orleans, typhoid rates, 137 New York, bacteria surviving treatment, 53 bleach efficiency, 100 liquid chlorine plant, 97 Nitrites, effect on dosage, 33 Nitrogen trichloride, 24, 128

O Odours, effect of contact period on, 43 nature of, 63 Ottawa, aftergrowths at, 57 bleach plant efficiency, 100 chloramine plant, 120 chloramine results, 121 sludge trouble, 65 typhoid rates, 140 Oxidisable matter, effect on dosage, 32, 36 Oxychloride, Guildford, 9 Middlekerke, 9 Ostend, 9 Ozone, 24

P Philadelphia and chlorination, 136 Pipe corrosion, 69 Pittsburg report, 71 Plumbo solvency, 71 _P. mirabilis_, 31 Potassium permanganate, 23 Puerperal fever in Vienna, 4 Pumps, for admixture, 41

R Red Bank, sewage disinfection at, 7 Reversed ratio of counts, 54

S Sewage disinfection at Baltimore, Berlin, 7 Boston, 7 Brewster, 6 Hamburg, 6 Maidenhead, 6 Sludge, as cause of complaints, 65 Sodium bisulphite, 86 Sodium chloride, deposits, 1 decomposition of, 106 Sodium hypochlorite, 105 decomposition of, 26 effect of ammonia on, 21 hydrolysis of, 26 Sodium thiosulphate, 87 Standard of purity, 30 Storage tanks, 75 Sulphuretted hydrogen, 33 Sylvine, 1

T Tannin, 67 Tastes, effect of contact period on nature of, 63 Temperature, effect on absorption of chlorine, 35, 38 bleach deterioration, 72 dosage, 34, 36 germicidal velocity, 38 pressure of liquid chlorine, 96 tastes and odours, 66 Thermophylic organisms, 54 Tolidine, 82 Toxic action of chlorine, 22, 29 Turbidity, effect on dosage, 45 effect of chlorine on, 132

U Use of chlorination, 144

W Water mains, disinfection of, 8 Well water, 7 Worcester, chlorination at, 11 Worthing experiments, 5

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CIVIL ENGINEERING

=5A= Unclassified and Structural Engineering.

=5B= Materials and Mechanics of Construction, including: Cement and Concrete; Excavation and Earthwork; Foundations; Masonry.

=5C= Railroads; Surveying.

=5D= Dams; Hydraulic Engineering; Pumping and Hydraulics; Irrigation Engineering; River and Harbor Engineering; Water Supply.

(Over)

=5E= Highways; Municipal Engineering; Sanitary Engineering; Water Supply. Forestry. Horticulture, Botany and Landscape Gardening.

=6=--Design. Decoration. Drawing: General; Descriptive Geometry; Kinematics; Mechanical.

ELECTRICAL ENGINEERING--PHYSICS

=7=--General and Unclassified; Batteries; Central Station Practice; Distribution and Transmission; Dynamo-Electro Machinery; Electro-Chemistry and Metallurgy; Measuring Instruments and Miscellaneous Apparatus.

=8=--Astronomy. Meteorology. Explosives. Marine and Naval Engineering. Military. Miscellaneous Books.

MATHEMATICS

=9=--General; Algebra; Analytic and Plane Geometry; Calculus; Trigonometry; Vector Analysis.

MECHANICAL ENGINEERING

=10A= General and Unclassified; Foundry Practice; Shop Practice.

=10B= Gas Power and Internal Combustion Engines; Heating and Ventilation; Refrigeration.

=10C= Machine Design and Mechanism; Power Transmission; Steam Power and Power Plants; Thermodynamics and Heat Power.

=11=--Mechanics.

=12=--Medicine. Pharmacy. Medical and Pharmaceutical Chemistry. Sanitary Science and Engineering. Bacteriology and Biology.

MINING ENGINEERING

=13=--General; Assaying; Excavation, Earthwork, Tunneling, Etc.; Explosives; Geology; Metallurgy; Mineralogy; Prospecting; Ventilation.

+---------------------------------------------------------------------+ | Additional Transcriber's Notes: | | | | * The original symbol in Table XIV (a circled +) has been changed | | to [¤]. | | * Some formulas have been spaced out for better readability. | | * Some minor typographical errors have been corrected (including | | indicators for references and missing diacritical marks from | | German words). | | * In-line multi-line formulas have been changed to in-line single- | | line formulas, if necessary with the addition of brackets. | | * Inconsistencies in spelling, hyphenation, lay-out or formatting | | have not been corrected, except in the following cases: | | * Bassenege, Schemmelweiss, Langar and Kanthdack in the name index| | have been changed to Bassenge, Semmelweiss, Langer and Kanthack | | as in the text. | | * Heisse, Jordon, Tonnetta Creek and Horrock's have been changed | | to Heise, Jordan, Tonetta Creek and Horrocks's, respectively, as| | elsewhere in the text. | | * Page 35: N^{1} and N^{2} in formula changed to N_{1} and N_{2} | | as elsewhere. | | * Page 7: Hadallen changed to Hedallen as elsewhere in the text. | | * Changes made to the text: | | * Page 17: --> changed to <=> in chemical formula as described in | | the text. | | * Page 26: H^{.} + HCO_{3} changed to H^{.} + HCO_{3}'. | | * Page 26: chlor-ions changed to chlorine ions. | | * Page 54: Gention Violet changed to Gentian Violet. | | * Page 103: Footnote marker [11] inserted (missing in original). | | * The author called Kurpjuivut, Kurjuivut and Kurpjuivat in various | | places in the text is probably called Kurpjuweit. The author | | called Schumburg and Schumberg in the text is called Schumberg. | | The book contains references to both Zaleski and Elmanovitsch | | and Valeski and Elmanovitsch; Zaleksi is probably correct. | | * Other remarks: | | * Footnote on Page 119: fraction unclear in the original, | | presented here as 5-1/2. | | * Page 134: affluents should probably be effluents. | | * In the original work, there is no TABLE XXII between TABLE XXI | | and XXIII. | +---------------------------------------------------------------------+