INDUSTRY’S INDISPENSABLE RAW MATERIAL, WATER, RIGHTLY DEMANDS THE CONSTANTVIGILANCE OF THE CHEMI,CALPROFESS~ON
fur Dri~kC~g Water
A. M. BUSWELL
IK
1880, the National Board of Health began a n extensive study of tests which had been proposed u p t o t h a t time for detecting pollution in water. The work was under the direction of J. W. Mallet, and one of the analysts was W. A. Noyes, then a graduate student a t Johns Hopkins, later t o become Secretary and then President of the AMERICAN CHEXICAL SOCIETY. T h e results of this investigation were published in 1883 as the annual report of the board for 1882. The introduction conveys the notions which prevailed in the field of sanitation a t the time. Mallet was convinced that the danger of pollution lay not in some chemical substance capable of causing disease but rather in the presence of living organisms in the organic matter carried by these waters. One of the earliest tests for such organic matter was the effect of heat on the evaporated residue. I n reviewing the previous literature on this test, Mallet quoted from Angus Smith, who expressed remarkable confidence in his ability t o judge the quality of water by the appearance and odor of its burning residue. H e claimed t o “detect humous and peaty acids, nitrogenous organic substances, and nitrites,” “to estimate their amount t o a very useful point of accuracy,” and t o distinguish their “animal or vegetable origin.” The tests for nitrates, nitrites, chlorides, and ammonia were in use in substantially their present form, but the principal interest centered around the determination of carbon and albuminoid nitrogen. The Mallet report was, therefore, concerned mainly with a comparison of the combustion process advocated by Frankland and Armstrong, the permanganate process developed independently by Kubel, Schultz, and Tidy and the albuminoid process of Wanklyn. T h e combustion method consisted in determining the carbon and nitrogen in the dry residue by converting t o carbon dioxide and nitrogen gas. This was obviously a very difficult procedure and was never generally adopted. T h e permanganate and albuminoid processes were essentially the same as we know those determinations today. Other early attempts t o measure organic carbon b y precipitation with alum, by dialysis, and by specific reagents were cited but dismissed as unreliable. For a comparison of the selected methods, sample waters of “known” quality were examined. Mallet’s conclusions from the results of this very extensive investigation were so sane and broadminded as t o warrant enumeration in a n account of this sort. Briefly, he says in the “Annual Report of the National Board of Health (1882)”:
A- A. Bzuwefi
should be given priority when judgment is passed on the quality of the water. 3. There are no sound grounds for establishing standards of purity based upon the amounts of certain constituents present. 4. Water analysis has two entirely legitimate uses: the discovery of the usual character of a water supply, so that suspicious changes can be detected and traced; and the detection of gross pollution, such as occurs with injury t o pipes and extensive leakage of drains. 5. Local standards of purity based upon sufficiently thorough and repeated examinations may be established. 6. Careful determination of nitrites and nitrates in drinking water is extremely important. 7 . I n judging a large-city water supply, it would be wise t o use all three methods considered for determining organic matter, and in no case should only one be used. EARLY BACTERIOLOGICAL AND BIOLOGICAL WORK
Mallet attempted to correlate bacteriological examinations with the chemical data, but the methods available were so cumbersome as t o discourage routine examination. The status of bacteriological water examination in 1880 is indicated by the experiments of the German biologist, Emmerich, who tested polluted waters by swallowing them himself, by feeding them t o animals, or by injecting animals subcutaneously with concentrates of polluted samples. Although he found t h a t water generally considered unwholesome or even dangerous could often be drunk with impunity by one in good health, he produced fever and even death in animals by subcutaneous injection of concent,rates. Following the current practice, the biological portion of the work, under the direction of Martin, Sternberg, and Hartwell included a microscopical examination, culture studies, and pathological experiments. For the microscopical examination, 200 ml. of the total sample were treated with 1 ml. of 1% osmic acid on the day of arrival, then set aside for the examination of sediment with and without staining (aniline violet) on the following day. The water was examined for organisms when received, and after a few hours’ standing the deposit (if any) was examined with and without staining. Then, after thorough mixing of the sample, several specimens were evaporated t o dryness and the residue was examined with and without staining. For culture study, 1 liter of a water sample was evaporated a t a low temperature t o about 5 ml. without risk of contamination from the air and within a moderate time by a special low-temperature reduced-pressure method. After filtration, part of the concentrated residue was inoculated with a tiny drop of a stale-hay infusion, containing a large variety of bacterial organisms. P a r t of the inoculated liquid was placed in a n hermetically sealed flask and placed in a warm chamber a t 40” C. T h e rest was put in the refrigerator. Next day, both specimens were examined microscopically, with and without aniline violet, and compared as t o the number of bacterial organisms contained in the samples. T o determine the pathogenic potency of the concentrate, usually 45 minims (approximately 2.5 ml.) were injected beneath
1. It is impossible t o judge the sanitary character of drinking water by any methods of chemical analysis investigated. 2. Information as t o the source and history of a water supply ahould not only be considered along with chemical evidence but
Coordinator: A. M. Buswell, State Water Survey Division, Urbana, 111.
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the skin of a rabbit in the anterior abdominal wall, in the neck, or in the groin. Before injection, the animal was tied down and his rectal temperature was taken three times a t hourly intervals. After injection, his temperature was taken five times hourly, and the same schedule was continued through the next day. For comparison, an uninjected animal was tied and observed in the same way at the same times, and differences in general conditions were noted. When possible, post mortem examinations were made of animals which died under experiment, but in hot weather commencing decomposition often rendered these tests valueless. The labor involved in experiments of this sort was considerable. Consequently, analysts of that time were deterred from undertaking routine biological water analyses. DEVELOPMENT OF STANDARDS FOR ILLINOIS
During the next 30 years, various laboratories developed their own chemical standards for potable waters. These were applicable within the region for which they were developed. C. W. Mason (1910) summarized the commonly accepted standards i n the eastern part of the country, and European practice was discussed by J. c. Thresh (1913) in their texts on water examination. The development of chemical standards in Illinois is typical of this work. T h e first systematic study of water quality in Illinois was undertaken by A. W. Palmer, head of the Department of Chemistry at the University of Illinois, in 1895. On the basis of 1787 analyses completed up t o December 1896, the Palmer standards of water purity for the immediate locality were published in 1897. They were prefaced by the following comment:
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number of samples of equal size, which was shown t o give a much lower probable error in the degree of pollution indicated. EVOLUTION OF NATIONAL STANDARDS FOR DRINKING WATER
One year after the formation within the AMERICAN CHEMICAL SOCIETY of the Division of Water, Sewage, and Sanitation Chemistry and the formation within the American Water Works Association of a chemical and bacteriological section, the first bacteriological standard for drinking water was adopted by the Treasury Department on October 21, 1914. Fifteen of the leading chemists, bacteriologists, public health experts, and sanitary engineers of the country were its authors. Its specifications were designed only for drinking water supplied t o the public by common carriers in interstate commerce. The new standard was in no sense intended as a definition of purity; rather, i t established “the furthest deviation from purity considered permissible,” so t h a t the health of the public could be protected, the prescribed quality of supply could be obtained without prohibitive cost, and the process of examination would not be too cumbersome. Because of the practical difficulty of securing first-hand information regarding the source and handling of supplies as offered t o the public, it was necessary t o rely almost completely on tbe information given b y laboratory examination. Chemical impurities were considered of minor sanitary importance (in line with Mallet’s thought some 30 years before). The definition of bacterial limits of impurity, on the other hand, was more readily accepted because of the greater knowledge of the disease-producing hazard of certain bacteria. The standard was accordingly defined in terms of the total
Because of differences due t o the nature of the strata from which waters are drawn or with which they have been in contact, the topography of the,district, and the general environment of the sources, no fixed standards of purity for any and all potable waters can be justly established, yet for pur oses of comparison, and for the information and convenience orthose receiving our reports, the following limits have been provisionally adopted for ordinary shallow wells in the State of Illinois. The maximum limits of impurities were stated as: total solids 500 p.p.m., no blackening or offensive odor on ignition of the residue, oxygen consumed 2.0 p.p.m., chlorine (as chloride) 15.0 p.p.m., nitrogen as free or saline ammonia 0.02 p.p.m., nitrogen as albuminoid ammonia 0.05 p.p.m., nitrogen as nitrites 0.001 p.p.m., nitrogen as nitrates 15.0 p.p.m. The formation of a reasonable and just opinion regarding the wholesomeness of a water requires that all the data of the analysis be considered with the history of the water, the nature of the source, the character of the soil and earth or rock strata, and the surroundings. This is a task for the expert. The Palmer standards were revised by Edward Bartow in 1907 in the last attempt t o correlate chemical data with dangerous pollution. Bartow found i t necessary t o set up five different sets of limits and t o include the newer bacteriological test as well. By the turn of the century, the science of bacteriology was beginning t o develop analytical techniques of increasing reliability. Within the next 20 years, these methods largely superseded the chemical tests for water safety, although the chemical determinations are still used in evaluating the amount of foreign matter present and the control of treatment processes. The development of bacterial standards was the result of the cooperation of laboratories from all parts of the country. This cooperative work is recorded in the successive reports of the Committee on Standard Methods of the American Public Health Association and the American Water Works Association. By 1912, the 37’ C. count on agar had been substituted for the 20” C. count on gelatin. Through the work of D. D. Jackson and others, lactose had been substituted for glucose in the fermentation test. Within the next decade, the use of sample volumes in geometric series was t o be replaced by the use of a
I n mid-l800’s, “Plumbers to the Croton Water Works” o$ered rotary p u m p s and models for chemical use
Aerators in the N e w York City water system looked like this in the year 1917
Hydraulic dredge i s used to excavate for river punaping station near chemical plant
Companies can perform a greai service by preventing the contamination of rivers with industrial wastes
bacterial population and the prevalence of B.(B.) coli, while culture media and methods of detection and identification were specified t o be those of “Standard Methods of Water Analysis,” 4.P.H.A. 1912. I n May 1922, the new Surgeon General called for a revision of the 1914 standards. Indicative of the importance attached by that time to drinking-water standards, the advisory council included representatives of six federal departments, of ten scientific societies, including the A.C.S., A.LT.A., A . W . R . A . , and A.O.A.C., and twenty members-at-large, all experts in chemistry, bacteriology, Banitation, or public health. The keynote of the new standards promulgated in June 1925 was safety. A satisfactory water was defined as “clear, colorless, odorless, pleasant t o the taste” and containing no excessive amounts of soluble mineral substances nor of chemicals employed in treatment. Quantitative limits were set on turbidity and color. Concentration limits (with quantitative methods of analysis) were established for mineral substances naturally occurring in waters and for chemicals used in water treatment. Whereas-in 1914 it was questioned “how far it is justifiable t o tax the carriers t o eliminate impurities whose deleterious effects are so doubtful,” the early concern for expense and for the unpopularity of laboratory examination was gone, and the presence of lead, copper, or zinc in excess of prescribed limits was now recognized as grounds for rejection of a supply. The bacteriological standard was changed to include only the test for organisms of the B.(E.) coli group (according t o “Standard BIethods,” 5th edition, 1923) as being the most highly specific test and giving the most information as t o fecal pollution and the potential presence of other pathogens from the intestinal tracts of diseased persons. The statistical basis for the technique of establishing both the limiting values for the mean density of B.(E.) coli and the allowed range and frequency of deviation from this mean was carefully and clearly treated with graphs in an appendix. I n contrast t o this degree of detail, neither the total number of samples t o he submitted nor the intervals of collection were defined, both being left to the judgment of the certifying authority. A further revision of drinking water standards a as undertaken in 1941. The first report of the committee was found unworkable. Further study resulted in the present standards which date from February 1946. At this time, requirements as to the source and protection of a water supply and the condition of the entire water-supply system were established. The newer bacteriological sampling techniques based on statistical analysis and interpretation were redefined. The minimum number of samples, the collection, and the location of sampling points !%-ere respecified in terms of the population served. Because these standards are still in effect today, are nationally accepted, and are probably the highest national standards in the world, they deserve mention. T h e chemical characteristics of a certifiable water were defined as: ( a ) the absence of any excessive amount of soluble mineral salts and of any chemicals used in treatment; (6 j limiting concentrations of potentially poisonous elements BY follows: lead 0.1 p.p.m., fluoride 1.5 p.p.m., arsenic 0.05 p.p.m., selenium 0.05 p.p.m., hexavalent chromium 0.05 p.p.m., with salts of barium, hexavalent chromium, heavy-metal glucosides or other substances physiologically harmful being barred from use in drinking-water supplies; (c) limiting concentrations of undesirable elements where other more suitable supplies were available as follows: copper 3.0 p.p,m., iron and manganese together 0.3 p.p.m., magnesium 125 p.p.m., zinc 15 p.p.m., chloride 250 p.p.m., sulfate 280 p.p.m., phenolic compounds 0.001 p.p.m. in terms of phenol, and total solids 500p.p.m. (or intheabsenceofa better supplyup to 1000 p.p.ni.). For chemically treated watersLe., lime-softened, zeolite, or other ion-exchange treated waters, or waters subiected t o anv other chemical treatments-the following three requirements are prescribed: ( a ) that tjhephenol-
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phthalein alkalinity (calculated as CaCO.?) be not greater than 15 p.p.m. plus 0.4 times the total alkalinity, which limits the permissible p H t o about 10.6 a t 25" C.; ( b ) that the normal carbonate alkalinity not exceed 120 p.p.m., which can be accomplished (since the normal alkalinity is a function of the hydrogen ion concentration and the total alkalinity) by keeping the total alkalinity within the limits suggested below when the p H of the water is within the range given; pH Range, 25O C. 8.0 t o 9.6 9.7 9.8 9.9 1
10.0 10.1 10.2 10.3 10.4 10.5to 10.6
Limit for Total Alkalinity (P.p.m. a8 CaCOs), 25" C . 400 340 300 260 230 210 190 180 170 160
(c) t h a t if excess alkalinity is produced by chemical treatment, . d
the total alkalinity not exceed the hardness by more than 35 p.p.m. (calculated as CaC03). Up t o this time, these standards had been considered only in their application t o water supplies of common carriers in interstate commerce. T h e 1946 revision was unique ih t h a t it contemplated for the first time the use of a standard for water quality generally acceptable and applicable t o all public water supplies in the United States. The publication carried the full endorsement of the A.W.W.A., which after study of the text resolved that it be voluntarily accepted by the association as the standard for all public water supplies. The association recommended t h a t state boards of health and their sanitary engineering personnel, in constructive cooperation with water works management, make every effort t o conform t o these standards. The high quality of drinking water in the United States today is in no small way the result of the vigilance and the scientific cooperation of the AMERICANCHEMICAL SOCIETY, which througho u t the development of these standards has been consistently represented on every advisory committee for revision.
A. M. BUSWELL AND L. A. RUSSELL
The Dalecarlia purijcation plant supplies Washington, D . C . , with a large share of its water
Sand filter plant for water purification was installed by Washington Sanitary Commission at Burnt Mills, M d .
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HE most significant advance in theoretical chemistry from the standpoint of water was the new concept of hydrogen ion concentration, because this involved the ionization of water itself. I n the practically simultaneous announcements by E. W. Washburn (1908) and S. P. L. Sorensen (1909) of the difference between titratable acidity and p H , the buffering properties of weak bases and weak acids were explained. The importance of this concept t o coagulation, corrosion, and culture studies is obvious. There followed the colorimetric methods for determination of pH and later their standardization against the electrometric measurement of p H for culture media. Today in chemical work, the electrometric measurement of p H has almost entirely replaced the use of indicators. The chemistry of the nitrogen determinations was explored in a sizable body of research, but in view of biochemical developments, these determinations were not of as great importance as once might have been thought. Certain inaccuracies and inconsistencies in the determinations of free and albuminoid ammonia were explained and rectified by the use of a phosphate buffer a t constant at p H of 7.4 in place of sodium carbonate added before distillation. T h e colorimetric determination of nitrites A. M. Buswell and L. A. Russell, State Water Survey Division, Urbana, 111.
Laboratory technicians conduct precise tests to determine the quality of drinking water 597
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INDUSTRIAL AND ENGINEERING CHEMISTRY
on treatment with sulfanilic acid followed by 1-naphthylamine and the determination of nitrates by treatment with phenol disulfonic acid were given extensive study with respect t o the chemistry of the reaction, interference effects, and sensitivity. T h e formation of free chlorine by oxidation of the chloride ion present with the nitrate led to the use of alkaline reduction of nitrates with aluminum and sodium hydroxide when chloride concentration was high. However, in the case of highly polluted waters, the use of strong alkali makes this method unreliable because of the hydrolysis of urea. Almost all public water supplies depend on the o-tolidine test for safety. Though the chemistry of the reaction between residual chlorine and the o-tolidine reagent is not complicated, the critical importance of this test to the safety of public water supplies has warranted much research to increase its reliability. The reaction is essentially an oxidation. Therefore, any ions present which have the proper oxidation-reduction potential to oxidize the o-tolidine reagent constitute an interference and source of false results. Also, the presence of nitrite, if high enough, may be sufficient t o consume completely the amount of residual chlorine usually considered adequate protection. Coupled with this is the fact that nitrite itself, given sufficient reaction time, will develop a yellow color with o-tolidine, creating a false residual and hence a real hazard. The development of green, blue, and red compounds instead of the characteristic yellow was a confusing aspect of the test until it was knonm that blue was characteristic of very alkaline samples and represented insufficient acid present for complete oxidation to the yellow compound. Moreover, the red was indicative of insufficient o-tolidine for the amount of oxidizing agent present. This resulted in the formation of a chloride derivative of the yellow holoquinone. The yellow color caused by the nitrite was traced t o diazotization followed by coupling with more o-tolidine, a reaction which could be reversed t o the colorless diazonium salt by excess acid. The search for a reagent more specific to chlorine and giving a stable color development revealed t h a t o-tolidine mas the best t o be found. The elimination of interference, the effect of pH, the order of addition of the reagents, the o-tolidinechlorine and the acid-0-tolidine ratios, and the temperature effect have all been studied and these results incorporated in the procedure in the latest “Standard Methods” (1946). When it vias found that the copper sulfate-potassium dichromate standards being used were no spectrophotometric match for the true yellow of the o-tolidine reaction, new standards of potassium chromate-dichromate were introduced. These were practically a perfect match both spectrophotometrically and visually. T h e meaningless results which came from using the method for low residuals on waters with high residuals led to the development of the drop dilution method (which uses a sufficiently small sample to give a residual of only 1.0 p.p.m.) and the equal v o l ~ m emethod (which uses a sufficiently large amount of the o-tolidine reagent t o react with the amount of oxidizing agent present). Chloramines react more slonly with the o-tolidine reagent but give the same yellow holoquinone. T h e necessity for distinguishing chloramines from free chlorine led t o the development of the o-tolidine-arsenite test, which measures the free available chlorine by removing interfering substances with arsenite and then allowing only 5 seconds for the reaction with o-tolidine, whereas 5 minutes are required for the chloramine reaction. The success of this test depends upon a rigorous adherence t o the details of the procedure. A recent study of this reaction notes the interference of hydrochloric acid when used as the acidifying agent but lists a number of correction factors which, if applied, allow the determination of the true free chlorine concentrat,ionfrom the results of the o-tolidine-arsenite test.
Vol. 43, No. 3
Recent,ly, a number of dangerous explosions in central Illinois were traced to methane in water supplies. Accordingly, a method was devised for the detection of methane in water supplies. I n addition, safety-limit concentrations and corrective measures were prescribed, based upon consideration of the behavior of dissolved ga.ses and the nature of water supply systems and storage reservoirs. Probably the most significant recent advance in methods of water analysis is the widespread adoption of instrumental techniques. Two instruments in particular are making possible greater precision in shorter working time : the photelometer and the flame photometer. The photelonieter, then known as the photoelectric hcmoglobinometer, was designed in 1929 by Sanford and Sheard as a means of determining the hemoglobin content of blood samples. Measurement was made of the percentage transmission of light, according to Lambert’s law. Today maximum sensitivity of the instrument is produced by the use of a filter whose t’ransmission band is as close as possible t o that of the material in Eolution, so that practically all light which does not change in intensit’y with concentration is screened out. Thus, small differences in concentration cause noticeably different and reproducible readings. The simplicity and the accuracy of t,his technique gave considerable impetus t,o the development of colorimetric 1net.hods to replace some of t,he long and tedious gravimetric determinat,ions. Copper, iron, chromium, arsenic, potassium, magnesium, tannins, orthophosphat’e, and silica can now all be determined in water by use of the photelometer. It has been a particular boon in the case of silica, which has become very important in scale and corrosion studies. Such studies have been neceasitated by the conditions which exist in the new higher-pressure boilers, which require in general more attention to the quality of boiler feed water. For some years, flame photometers were not susceptible t’o the degree of accuracy required by most analysts. However, persistent research has explored most of the troublesome aspects of interference effects and has both encouraged improvemerlt in t,he construction of the instrument and brought’ t o light interferences which were previously unsuspected. Increased knoiT1edge of the instrument and of the precautions which are a part of intelligent, operat$ion is making possible the rapid and precise determination of sodium, potassium, lithium, and calcium on very small samples which require no previous preparation. The abandonment of the “temporary hardness” determination has eliminated many misleading or meaningless data. Various attempts to improve the soap-hardness test were not sufficiently successful, but the versenate-hardness test seems t o provide a satisfactory, rapid method for hardness determinations. The B.O.D. determination for pollution load has been the subject of many important papers before the Division of Water, Sewage, and Sanitation Chemistry, and the reproducibility and accuracy of the test have been greatly improved.
F. W. MOHLMAN
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ONDITIONS of filth and disease became so rampant in England that finally the use of water t o dispose of sewage was introduced early in the nineteenth century. But although this was a great advance in convenience and safety, new difficulties developed. The classical references to the condition of the Thames and the Rhine indicate t h a t there also existed the urgent need for effective ways t o dispose of sewage prior to its dischargc into streams.
F. W. RIohlman, Sanitary District of Chicago, Chicago, Ill.
A Royal Commission was established in England in 1857 and several others continued their studies of the problem until the turn of the century. Frankland was the leader in these early investigations, before the germ theory of decomposition was fully established. Because of a general lack of understanding, chemical methods of precipitation were developed, in which lime, alum, ferrous sulfate, ferric salts, zinc salts, and-of all rombinations-alum, blood, and charcoal (ABC) were used as precipitants. Acting as adsorbents, other inert solids were added, notably clay, marl, paper, and peat. However, unable t o stabilize the putrescible organic matter, these costly processes fell into disrepute. When Iiiological methods of treatment were discovered and evaluated by the Royal Commissions, chemicals were almost entirely :lbandoned and such processes as contact beds, trickling filters, and sand filters supplanted the methods then in vogue. The Royal Commission of 1857 was followed by others 111 1868, 1882, and 1898. Frankland turned t o biological filters but without much success. At Lawrence, Mass., the State Board of Health started experiments in 1886. This date marks the birth of sand filters, contact beds, and trickling filters in the United States. All conceivable combinations of depth, area, size of stone, and rate of dosing were studied, and by 1900 biological filters were well established in America. One of the most impressive results of this development was the discovery of the role of nitrification in stabilizing sewage. I n fact, nitrification was considered absolutely essential to satisfactory sewage treatment, and not until after 1930 did sewage technologists agree that stabilization might be possible with little or no nitrification. The use of contact beds never became very common in the United States, but intermittent sand filters dominated the scene in Massachusetts and wherever suitable sand could be found. Trickling filters became the most approved type of treatment by 1910, but flow rates of less than 3,000,000 gallons per acre per day were adopted. Moreover, complete nitrification was expected in summer by the use of such installations. T h e large areas that were required created concern, but no investigator had the temerity t o suggest that higher rates might be possible. The introduction of the activated sludge process in 1913, following its discovery by Ardern and Lockett a t Manchester, England, completely overturned American practice. I n America, this process was much more fully developed than in England, and soon America was dotted with activated sludge plants. T h e fine effluent, the high capacity despite small areas, the freedom from odors and flies, and the simple mechanical control of the operation so captured the fancy of American engineers and chemists t h a t all other processes declined and filters were wellnigh forgotten. However, early enthusiasm for the activated sludge process was tempered when the difficulties of sludge disposal were recognized. Activated sludge was very low in solids content, averaging only 1 t o 2%. Before the process could be considered a success, much research had to be done t o improve the disposal of the sludge which accumulated in large quantities. Milwaukee pioneered in studies in p H control and heating in the pretreatment step before vacuum filtration. However, filtration was made practical only after the superlative value of ferric chloride as a conditioner was discovered in Chicago in 1927. Now all activated sludge plants use this chemical for dewatering undigested activated sludge. “Digestion” is a magic word in sewage disposal development. Ever since Imhoff tanks were installed in America in 1909, the advantages of digestion in the disposal of sludge have been recognized. Digestion changes the foul, greasy character of fresh sludge to homogeneous, gas-filled, loamlike solids which will air-dry quiclrly and without odor. T h e digestion process, accomplished by anaerobic methane-producing bacteria, gives off
Increased city population required the installation of four new sedimentation tanks at sewage plant
By introducing gelatinous solids into turbid water supplies, jlocculator improves settling and Jiltering characteristics
I n foreground i s automatic magnetite filter at the Eldridge, Calif., sewage works; clarijier and digester in background 599I
sectionof
the clayton sewage plant in ~ contains a battery of chemical feeders
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Activated plant in sanitary District has capacity for 400 million gallons of sewage a day
weights of gas equal to or actually greater than the weight of organic matter destroyed, and this gas has been used to heat the digesters and run gas engines which, in turn, light and heat sewage disposal plants. The production of gas and the advantages of heating sludge Rere well established in America, notably by chemists Buswell and Ruaolfs, and by the extensive research carried on in Illinois and Xew Jersey. Today digestion is standard practice in the disposal of sewage solids, unless certain cities elect to filter and dry activated sludge for sale as fertilizer or to be burned as fuel. The fertilizing value of activated sludge is well established by its content of 670 nitrogen and 3% phosphorus pentoxide. Digested sludge, on the other hand, contains about half this content of fertilizer constituents and is suitable only for disposal as a dry filler or compost. However, this use is adopted in some cases, although the material is too low grade t o warrant For even the l shipment~ for any ~great distance. ~ ~ local disposal, , met sludge is useful, but its value hardly equals the cost of disposal. The \Taste disposal problem has become a paramount concern of industrial chemists. The importance of treating wastes from industry is recognized as being almost equal to the importance of sewage treatment, if our streams and lakes are to be maintained in decent condition. Industrial chemists are developing such processes as neutralization of acids, precipitation of solids, screening of food products wastes, and biological treatment of liquids, in efforts to eliminate the undesirable qualities of industrial wastes. Sotable examples are the plants of the Dow Chemical Co., Calco Chemical Division of ilmerican Cyanamid Co., Celanese Corp., American Viscose Corp., Upjohn Co., and Lederle Laboratories. l l a n y other chemical manufacturing plants neutralize, stabilize, or evaporate their wastes inside the factory and thus do not have t o install final treatment plants. These companies include Du Pont, National Aniline, Corn Products, Commercial Solvents, Koppers, and various distillers or alcohol manufacturers. Industry's acceptance of its responsibility for proper waste disposal has developed largely during the past 20 years. During this same period, sewage disposal engineers have markedly improved one of the basic biological methods of treatment. The old stereotyped trickling filter has been streamlined and now is in common use a t rates five t o ten times higher than those employed formerly. This process is moving to the forefront and now is almost on a uar with the activated sludge treatment in terms of space requirements, freedom from odor and flies, and, t o some extent, quality of effluent. Chemists and bacteriologists found that continuous, rather than intermittent, dosing of stone beds is feasible and that, except for nitrification, almost comparable effluents can be produced. The theory is that the sewage should be applied continuously t o the entire surface of the filter in a raindrop type of spray, rather than intermittently a t higher rates. This theory seems t o be substantiated, and the highrate filters appear to be well adapted t o organic types of industrial wastes. Some development of high-rate anaerobic digestion of concentrated organic wastes has occurred, although such treatment still resides in the experimental category. Because of the large tank capacities required, this process is rather expensive. Chemists still have many unsolved problems ahead, particularly those involving the disposal of wastes from atomic energy plants. This is a momentous problem, but it is being attacked widely and thoroughly and does not appear unsurmountable. So far, the methods adopted have proved their worth. Those who have worked or lived among the wastes have done so with almost complete safety. This criterion may be modified as time elapses, but in the meanwhile there is evidence that processes will be available in time to prevent danger from untreated subatomic wastes. I
Studying atomic energy wastes, research assistant removes radioactive specimen f r o m its lead container
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Chemists thus are challenged b y many unsolved problems, but the notable advances during the past 75 years permit the confident forecast that future progress will continue at a n accelerated pace.
H. C. MARKS
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HE history of disinfection in the field of water, sewage, and sanitation chemistry over the past 75 years has been very largely the history of the chlorination of water and sewage. Following numerous European examples of the use of hypochlorite t o destroy contamination in water supplies, George W. Fuller applied the technique in Louisville, Ky., in 1896. In 1906, Phelps used chlorine compounds t o treat sewage in Boston, Mass., and in Red Bank, N. J. At about the same time, Kellerman, Pratt, and Kimberly also used hypochlorite t o treat sewage effluent . G. A. Johnson initiated continuous chlorination for the routine protection of water supply in 1908 a t the Bubbly Creek filter plant. He also set up a n installation to protect the water supply at Boonton, N. J. High cost and laborious application would have prevented hypochlorite from adequately protecting the modern public drinking water supply. Great advances in the elimination of water-borne diseases resulted from the development of liquid chlorine production and equipment for its application. I n the United States, the first use of liquid chlorine was made by C. R. Darnall a t Fort Meyer, Va. A chlorine-control apparatus which served as a basis for much of the future technological advance was installed by M. F. Tiernan and C. F. Wallace a t Dover, N. J., February 22, 1913. From the beginning, chlorination of drinking water required a delicate balance between sterilizing doses of chlorine on the one hand and concentrations below the taste threshold on the other. Improvements were necessary not only in control equipment but also in sterilizing efficiency and in minimizing tastes and odors. The first improved technique involved the joint use of ammonia and chlorine. On the American continent, this was first tried by Joseph Race at Ottawa, Canada, in 1916. It was believed t h a t the chloramine process gave better sterilization, and it was demonstrated that it minimized tastes and odors. The method was quickly taken up and used widely. At the same time, the chemistry of the process was thoroughly investigated. While chloramine is now known as basically less efficient than hypochlorous acid, the greater persistence of the chloramine residual has been of value. I n fact, the process is still used to advantage. I n swimming pool sterilization, the stability of the chloramine has been of particular importance. A second improved technique was superchlorination with or without subsequent dechlorination. After favorable reports from England, N . J. Howard applied the process at Toronto and in 1926 was the first t o observe that the chlorine requirements were related to the amount of nitrogenous material in the water. In 1928, R. D. Scott discovered the apparently unrelated fact that, under certain conditions, increasing chlorine dosage caused a decrease in the residual. He also pointed out that this phenomenon occurred correspondingly close to the point a t which there was a sudden reduction in phenolic tastes. Another piece of the puzzle was contributed by E. Watzl in 1929, when he discovered t h a t a suitable degree of superchlorination would oxidize nitrogenous materials t o nitrogen gas and thus remove them from the water. A certain time had t o elapse before these apparently isolated phenomena were connected in any way. I n 1939, H. A. Faber called attention t o a possible interrelation. At about the same
A municipal plant uses a group of Wallace and Tiernan chlorinators to disinfect city’s water supply time, A. E. Griffin demonstrated that the initial rise in residual followed by a dip and then by a secondary and permanent rise a s the dose was increased was a rather typical pattern. C. K. Calvert started unification of the picture by showing t h a t the quantitative aspects of this curve were closely related t o the ammonia nitrogen content of the water. Following these scattered beginnings, the reactions encountered in superchlorination have been investigated in great detail. This has led to the widespread application of superchlorination and realization of the great advantages of “free available chlorine residual.” Of great aid in practical application has been the “break-point” technique-that is, the method of controlling the degree of chlorination by a study of the chlorine residual-chlorine dose curve. The successful maintenance of the delicate balance in chlorination practice has also depended upon the availability of analytical methods for the control of dosage. Of greatest importance were the origination of the o-tolidine method and its development by Ellms and Hauser in 1913 and Wohlman and Enslow in 1919. While refinements in analytical methods have been basic throughout, the great progress made in recent years-in superchlorination, in the break-point technique, and in choosing the correct type of residual t o do the job-has, in large part, been brought about by the development of tests, such as the Laux o-tolidine test and the Hallinan o-tolidine arsenite test. While chlorine dioxide was suggested for water purification in the nineteenth century, its use on any sizable scale developed only after sodium chlorite was made available commercially. Then i t was recommended mainly for taste and odor control in phenolic waters in a paper given by Synan, MacMahon, and Vincent at the national meeting of the AMERICANCHEimcAL SOCIETY in September 1944. It was realized t h a t chlorine dioxide was of some value in disinfection and, in recent years, this reagent has found a place both in taste and odor control and as a n adjunct t o chlorine in disinfection. Bromine as a possible sterilizing agent for water was investigated by T. D. Beckwith and J. R. Moser in 1933. Their finding of a n activity not very different from chlorine was subsequently confirmed by F. W. Tanner, G. Pitner, and J. A. McCarthy. Because bromine is relatively expensive and conveniently applied only on a small scale, its use has been confined t o swimming pools. After a flurry of interest in the early twentieth century, the ozone process was held back by high costs and operating difficulties. The method was given renewed attention just prior to World War 11, but mainly for use in odor and taste control.
H. C. Marks, Wallace and Tiernan Products, Inc., Belleville, N. J. 601
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 43, No. 3
Recently, ozone has been considered for sterilization, but serious drawbacks have yet to be surmounted.
ment of water for distilleries, carbonated beverages, canning, ice manufacture, and dyestuffs (1943), the control of scale and corrosion (1944), and sewage and trade-waste analyses (1946). The period of the division’s existence has seen the large scale application of the lime and soda softening process and the development of base-exchange processes for household softening as well as for laundry and industrial purposes and municipal supplies. Sterilization methods have progressed from the use of bleaching powder to the use of liquid chlorine, the chloramines, RIOIt t o 1913, chemists interested in water supply, sewage and break-point chlorination. Various pH-control methods for disposal, and related sabjects were presenting papers before coagulation and softening have been introduced. The activatedseveral sections of the AAIERICAX CHEMICAL SOCIETY and before sludge method of sewage purification has been developed from the general sessions of related associations. Chemists of none the earliest American experiments reported a t the division’s of the groups were satisfied, nor were superintendents and engifirst meeting to the recent completion of the largest installation of neers, when papers of interest to them were scattered among the this type in the world in a plant of the Chicago Sanitary District. more numerous papers on general chemical and bacStudies of stream pollution teriological subjects a t nahave shown the necessity for tional meetings. treating sewage and industrial Accordingly, a request was Officers of the Division of Water, Sewage, and wastes. Treatment of inpresented by Edward Bartow Sanitation Chemistry, 4915-1951 dustrial wastes within the to the Council of the Society Year Chairman Secret,ary factory has resulted in adin Milwaukee on March 24, H. P. Corson 1915-1916 Edward Bartow ditional profits t o the factories 1913, for the formation of a R. B. Dole H. P. Corson 1917 concerned. R a d i o a c t i v e section devoted to waterprobE. H. S.Bailey natural waters have been lems. I n due course, such a H. P. Corson 1918 It. S. Weston found. As fluorine in drinlisection was formed and given R. 9. Reston IT.Skinner 1919 ing mater has been suspected the name, Section of Water, J. W.Ellms UT.IT. Skinner 1920 as the cause of mottled Sewage, and Sanitation W.P. Mason 77;. W,Sltiririer 1921 enamel on teeth, surveys of Chemistry, corresponding to A. M. Buswell ST’. W.Skinner 1922-1923 the fluorine content of waters Division 14 of Chemical A b F. R. Georgia 1924 77’. W. Skinner throughout the United States stracts. The first meeting was F. R . Georgia 1925-1926 F. W.RIohlman have been made. The reheld in Rochester, N. Y . , in \Ti. D. Hatfield 1927 W. D. Collins moval of tastes and odors September 1913. The divi8.E. Cohurn W. D. Collins 1928-1929 from water by activated carsion was authorized a t the W.D. Hatfield W.D . Collins 1930 bon and chloramines has New Orleans meeting of the E.J. Theriault 1931 W.D. Hatfield been developed. Council in 1915. The first -4.S. Behrman E . J. Theriauli 1932 I n the 37 years of its existofficers elected were Edward A. S. Rehrman C. S. Boruff 1933 ence, the Division of Water, Bartow, chairman, E. B. C. S. Boruff 1934-1935 E. S. Hopkins Sewage, and Sanitation has Phelps, vice chairman, and R. C. Bardwell C. R . Hoover 1936-1937 presented a t 70 meetings of H. P. Corson, secretary. A. P. Black C. R . Hoover 1938-1939 the A~\IERICAN CHEMICAL soThe emphasis of the proF. G. Straub 1940 0. PI. Smith CIETY a total of 972 papers. grams has always been on F. G. Straub 1941 C. R. Hoover At the present time, research laboratory and plant research 19-12 C. S. Howard H. Gladys Snope in every phase of water, sewas opposed to operating data H. Gladys Swope 1943 L. F. Warricli age, and sanitation problems and routine tests. The conIT. Rudolfs H. Gladys &Tope 1944 is producing so many papers sistent growth in the scope C. C. Ruchhoft H. Gladys Swope 1945-1946 that the value of the national and number of papers as well W.W. Hodge H. Gladys Swope 1947 meeting (with its problems of as the increased interest of T. E. Larson 1948 H. Gladys Swope housing and meeting facilimembers has been proof of T. E. Larson 1949 William Stericher ties) is again becoming questhe service rendered and of T. E. Larson 1950 S. K. Love tionable, as the sessions dethe progress made. Through J. J. Dwger T 1.: 1,arson 1961 voted solely t o the division joint symposia with other extend through the divisions of the AMERICAN - practically _ entiye convention time, Thus it may be that the regi‘onal CHEMICBL SOCIETY, the Division of Watw, Sewage, and Sanitation Chemistry has sought to encourage cooperation in solving the meetings within the Society mill soon offer all the services of problems of water and waste treatment and analysis. the rational meeting without the problems of travel and housing. I n 1929, the Division of Industrial and Engineering Chemistry THE FUTURE and the Division of Gas and Fuel Chemistry were invited to join The treatment of waters containing radioactive wastes from this division in a symposium on the subject of boiler-room atomic energy developments in national laboratories will be chemistry. I n 1934, Section A of the Division of Physical and one of the most immediate and most challenging problems of Inorganic Chemistry met with this division to discuss the inthe future. But of even greater importance is the problem of organic chemistry of water supply. The Baltimore program in adequate water supply t o meet the tremendously increased 1939 held in conjunction with the Division of Colloid Chemistry demands of industrial plants, sanitation, and modern convenwas devoted t o colloids and wastes in water treatment. The iences (such as air conditioning), especially in large municipal Division of Industrial and Engineering Chemistry has convened areas, which are already reusing their water supplies many times with this division four times since the 1929 meeting: t o discuss over. The future problem is water not treatment. the nature and treatment of industrial wastes (1939), the treat-
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Condensed from committee report by Edward Bartow, W. D. Collins, F. W. ilIohlman, and H. Gladys Srvope
