aitifacti, S^eto $attt THE LIBRARY OF EMIL KUICHLING, C. E. ROCHESTER, NEW YORK THE GIFT OF SARAH L. KUICHLING 1919 Cornell University Library TD 225.W31 ..Purification of the Wasliington water 3 1924 004 460 386 CORNELL UNIVERSITY LIBRARY ENGINEERING I Cornell University y Library The original of tiiis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924004460386 SENATE. PURIFICATIO]^ OP THE WASHINGTON WATER SUPPLY. AN mQIIIRY HELD BY DIRECTION OF THE UNITED STATES SENATE COMMITTEE ON THE DISTRICT OF COLUMBIA. EDITED AND COMPILED BY CHARLES MOORE, Clerk of the Senate Committee on the District of Columbia. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1901. OOIiTTEI^TS. INTRODUCTION. Action of the United States Senate on the question of the filtration of the District of Columbia water supply. Page. Report of Mr. McMillan, from the Senate Committee on the District of Columbia ix Report of Rudolph Hering, George W. Fuller, and Allen Hazen xii CHAPTER I. Statements made at a hearing held at the Waldorf-Astoria Hotel, New York City, January 4, 1901. Persons present at the hearing 3 Statement of Dr. J. S. Billings 4 Pressure filters not efficient 5 Five essentials in filtration 6 Statement of Prof . William P. Mason 7 When slow sand filter is preferred 8 The Washington tests 9 Conclusions 11 Bacterial efficiency 11 Comparison by cities 12 What the Washington figures show 13 The Cincinnati report 15 Tests of turbidity 16 The Elmira plant 18 Colon bacillus 19 Statement of Allen Hazen 21 Efficiency of filters 22 Necessity of use of coagulants 23 Gravity and pressure filters 24 Mechanical filters can do satisfactory work 25 Bacteria in under drains - r 26 Colon bacillus 27 Local conditions determine the type of plant 28 Improvements in mechanical filters 29 Statement as to the Hyatt patents 29 Cost of process 31 HI IV CONTENTS. Statement of Allen Hazen — Continued. Page. Covering for filter beds •'^ Effect of ice on filter beds ^2 The measure of turbidity ^^ The cost of alum ^^ The use of alum **' Chemical changes produced by alum 39 Storage capacity of Washington reservoirs 39 Statementof George W. Fuller 40 The Washington problem ^■. •-..■- 41 Efficiency of mechanical filters 42 Types of mechanical filters 43 Chemical changes in efiluent f f oiii mechanical filtration 44 Boiler incrustation 45 Bacterial efficiency * 46 Turbidity '- 47 Colon bacillus 48 Relative cost of filtering systems 49 The McDougall System..... -. ^.- - - 50 The Fischer system 50 Statement of Edmund B. WeBton ....^.^ ^^........^.^.s..... 52 Eesults from mechanical filters 52 Comparative costs 55 Bacterial efficiency 60 Medical Society report 61 Deceptive figures 62 Statistics from cities using mechanical filters .:.. 64 The Morison filter 66 Bacterial efficiency of Washington filters 67 The Washington problem ■. 70 The Pittsburg slow sand filter 71 Statement of joim W. Hiil 72 Per capita use of water i 72 The Cincinnati system 73 Covering filters 73 Points of superiority of the slow sand filter 74 A coagulant not absolutely necessary for any water » 76 Knoxville, Lexington, and Elmira filters 77 Pressure filters 79 Bacterial efficiencies 80 Covering of Washington filtration beds 80 Statement of Eudolph Hering 82 The Atlanta plant 83 Mechanical filtration at Philadelphia 84 Efficiency of filters 85 The clear water basin 85 Slow filters preferred ^ ^.... 86 Double filtration 87 The clear water basin 87 Washington sewer system 89 Covering filters ■. ..^ 90 Comparative merits of slow and rapid filters 90 Statement of John M. Diven 91 Statement of George A. Johnson 94 CONTENTS. T CHAPTER II. A paper on the Filtraiion of Public Water Supplies, prepared by Lieut. Col. Charles Smart, deputy colonel surgeon. United States Army, and indorsed by Surgeon- Oeneral Sternberg. Page. Letter from Surgeon-General Sternberg 98 Letter from Lieut. Col. Charles Smart 98 Filtration in German cities 99 Filtration in the United States 100 Mechanical filters 101 Slow sand filtration 101 Experiments in Washington 102 Bacterial efficiency of mechanical filters _ . _ 103 Comparisons 104 The use of alum .-. 105 Conclusion 106 CHAPTER III. A paper on the Filtration of Public Water Supplies, prepared by P. A. Surg. H. D. Oeddings, of the Marine-Hospital Service, and indorsed by Supervising Surgeon- Oeneral Wyman. Letter from Surgeon-General Wyman - 107 Letter from Dr. H. D. Geddings 108 The English or slow sand filtration process 109 Rate of filtration by the slow sand method 110 Covering of filtering beds for the slow sand filtration method Ill Results obtained from the use of slow sand filtration Ill Mechanical filtration or the so-called American system 113 Objections urged against the mechanical system of filtration 114 Efficiency of the mechanical system 115 Cost of mechanical filtration r 116 Comparison of the slow sand and the mechanical system of filtration 117 CHAPTER IV. Letter from Mr. Robert Spun- Weston in regard to the report of the District of Columbia Medical Society. Need for filtration 121 Practical effects of filtration 121 Cost of sand filtration 121 Comparative cost of sand and mechanical filters 122 Mechanical filters ineffective 123 Effects of filtration on turbidity 123 Clarification by sand system satisfactory 124 Results accomplished by experiment of sand filter 125 The use of coagulants 127 CHAPTER V. Extract from the report of the committee on public health of the Washington board of health. Sanitary condition of Washington 129 The natural and mechanical methods of filtration 130 Typhoid fever statistics ■'-^-'- Comparative death rates 1^2 VI CONTENTS. CHAPTER VI. Historical review of the sanitary efforts to lessen typhoid fever in the District of Columbia. Page. Appropriation for experimental filtration 1^* Eesults of Colonel Miller's experiments 1^^ Hearing of experts on water purification ^36 Turbidity as a factor in purification of Potomac water 137 Efficiency of sand-bed filtration 138 Typhoid fever statistics 1^^ The lessened death rate from typhoid fever the main object of filtration 140 Pittsburg statistics I'^l Superior bacterial efficiency of slow sand filtration in Washington 142 Danger from tjrphoid fever germs in periods of greatest turbidity 144 Effects of alum as a coagulant 145 Importance of hygienically pure water 146 APPENDIX— PAET I. Report of the investigation on the feasibility and propriety of filtering the water sup- ply of the city of Washington. The letter from the Secretary of War 149 The letter from the Chief of Engineers U. S. A 149 Colonel Miller's report 150 The water supply of Washington 151 The Potomac Eiver water 156 Results of chemical analysis of Washington water supply 1 59 Filtration 165 Experimental filters 168 English or slow sand filter (a) 168 The American or mechanical filter (6) . 169 Methods of conducting tests of filters 170 Turbidity 170 Rate of filtration 173 Scraping sand filters 175 Amount of water supply between scrapings 176 Efficiency of the filter under the various conditions 177 Amount of water reqmred for washing and waste 181 The amount of coagulant required 182 Estimate of cost of the Washington water supply 182 Conclusions and recommendations 189 Letterof Dr. W. M. Mew 191 APPENDIX— PART 2. Report made by a special committee of the Medical Society of the District of Colum- bia upon the relative merits of the slow sand and mechanical fUtraikm. Letter from Dr. Thomas C. Smith 193 Need for filtration 193 Practical effects of filtration 194 Cost of sand filtration 194 Comparative cost of sand and mechanical filtration 194 Mechanical filtration ineffective 195 Superior bacterial efficiency of sand filtration 196 CONTENTS. VII Page. Reduction of typhoid fever 197 Effects of filtration on turbidity 199 Clarification by sand filtration satisfactory 199 Addition of alum to Potomac water not warranted 199 Reasons why experimental sand filter did not accomplish even more striking results 200 Sand filtration a natural process 201 Results of mechanical filtration, the American process 203 Results of mechanical filtration unsatisfactory 203 Installation of sand filtration instantly recommended 203 APPENDIX— PART 3. A discussion of the filtration of water for public use by the American Society of Civil Engineers, at tlw London meeting, 1900. Remarks of Mr. Rudolph Hering, of New York 205 Methods of purification 206 Efiiciency of sand filters 206 Continuous and intermittent filtration 207 Filter covers 207 Settling basins 207 Cleaning slow-sand filters 208 Mechanical filters 208 Pressure filters 208 Both systems give good results 209 Sanitary effects 209 Reliability of operation 209 Conclusions 209 Remarks of George F. Deacon, of Liverpool 210 Remarks of George W. Fuller, of New York - 211 How foreign and American problems differ 211 Turbid waters 212 Three types of waters 212 Waters of the Glacial Drift region , 213 Waters of the South and West 213 Waters of the Delaware, Susquehanna, and Allegheny 214 American experiments 215 English sand filtration, not mechanical 216 Covers for filters 217 Mechanical filters 217 The question of coagulation 217 Difficulty of operating sand filters where waters are turbid 219 Remarks of Samuel Rideal, of London 219 Remarks of Henry Davy, of Birmingham 220 Remarks of Dr. Ad. Kemna, of Antwerp 221 Remarks of Walker Hunter, of London 223 Remarks of Nicolas Simin, of Moscow 224 R6sum6by Rudolph Hering 228 APPENDIX— PART 4. Daily mean temperatures in the District of Columbia. Letter from H. E. Williams, Acting Chief United States Weather Bureau 233 Senate Report No. 2380, Fifty-sixth Congress, second session. THE RELATIVE MERITS OF THE MECHANICAL AND THE SLOW SAND SYSTEMS OF FILTRATION FOR THE WATER SUPPLY OF THE DISTRICT OF COLUMBIA. February 19, 1901. — Referred to the Committee on Appropriations and ordered to be printed. Mr. McMillan, from the Committee on the District of Columbia, submitted the following REPORT. On December 20, 1900, the Senate, by resolution, directed the Com- mittee on the District of Columbia to make investigation and report as follows: Resolved, That the Committee on the District of Columbia be, and it is hereby, directed to investigate and report to the Senate, at the earhest 'practicable date, the relative advantages of the so-called mechanical system and of the slow sand system of water filtration for cities, and the necessary expenses of such investigation shall be paid from the contingent fund of the Senate. The committee respectfully reports as follows: The subject of the filtration of the District of Columbia water supply was brought to the attention of Congress in 1894 by Col. George H. Elliot, Corps of Engineers, then in charge of the Washington Aqueduct. The District of Columbia appropriation act approved June 30, 1898, provided that the officer in charge of the Washington Aqueduct should make an investigation of the feasibility and propriety of filtering the water supply of Washington, and submit to Congress a full and detailed report thereon. Three thousand dollars was appro priated for the purpose. The duty of making this investigation devolved upon Lieut. Col. A. M. Miller, Corps of Engineers, whose report is contained in Senate Doc. No. 259, Fifty-sixth Congress, first session. This report was received while the District appropriation bill for that year was under consider- ation, and it was decided to appropriate $200,000 to be expended on those portions of a filter plant which would be necessary in either case whether the mechanical system or the slow sand system of filtration should be adopted. This action was taken because more time was X MECHANICAL AND SLOW SANU SYSTEMS OF FILTRATION. desired to decide upon the system to be adopted for the District of Columbia than could properly be given within the limited time then at the disposal of Congress. After a very long and careful investigation, the report from the War Department, known as Colonel Miller's report, took the ground that the water supply of the District of Columbia contained suspended clay in such fine particles as to make it practically impossible to use the slow sand system of filtration, and he, therefore, recommended the adoption of the rapid, or mechanical, system of filtration. This report was sharply attacked by the Medical Society of the Dis- trict of Columbia, and, following the lead of the medical society, by the board of trade and the business men's association. It was argued by those bodies that the use of alum as a coagulant was in itself objec- tionable, and that the mechanical process was inferior to the slow sand system as a means of removing those forms of pollution that are the cause of typhoid fever. An inquiry conducted by this committee in New York City on Janu- ary 4, 1901, was attended by men who have made for themselves the highest reputation in the matter of the construction and operation of filters for public water supplies. No large filter plant, either in exist- ence or projected, was unrepresented at that meeting. The plants at Lawrence, Mass.; Albany, N. Y. ; East Providence, R. I.; Norfolk, Va. ; Elmira, N. Y., were among those as to which direct testimony was given; and the projects at Philadelphia, Pittsburg, Louisville, Cin- cinnati, Paterson, and New Orleans were discussed by men who had served or were then serving upon the boards of experts for those cities. No such representative gathering of filtration experts ever before took place in this country. It is true that the discussion of the subject of the filtration of public water supplies held at the meeting of the American Association of Civil Engineers in London, England, in July, 1900, brought together a larger representation of foreign experts; but the leaders of the discussion in London were also present in New York, and at the latter gathering the American problem had its fullest discussion. The result of this discussion established the fact that the slow sand filter, wherever it had been put into operation, had produced uniformly good results both in clearing the water from turbidity and also in removing bacteria. The theory was maintained, however, that dif- ferent types of water require different treatment, and that for waters that are simply polluted the slow sand filter is to be preferred; whereas for very turbid waters, containing fine particles of clay, the use of a coagulent is necessary. From this theory but one expert dissented, Mr. John W. Hill, who has had experience in the study of the water supply at Cincinnati, Philadelphia, and other cities. Mr. Hill main- tained that he had never found a water for which he would not recom- mend the slow sand filter, Cincinnati being no exception. With the MECHANICAL AND SLOW SAND SYSTEMS OF FILTRATION. XI exception of Mr. Hill, the experts were of the opinion that the mechan- ical system, when properly operated, was capable of producing superior results as to the clearness of the water and equally good results with the sand filter as to bacterial efficiency. It was admitted that such results had not been uniformly attained; and this was held to be due to a variety of causes which had prevented the mechanical systems from being managed with a view to obtaining the highest efficiency of which they were capable. There are to-day no cities of the size of Washington using the mechanical system of filtration; but, on the contrary, Lawrence, Mass. , and Albany, N. Y., are successfully operating slow sand filters, and Pittsburg is putting in a slow sand system. Philadelphia is about to install a slow sand-filter plant for three-fourths of her water supply and is to construct a mechanical plant for the other fourth, merely for temporary use, the expectation being that the water supply at that particular point will be exhausted within a definite time. At Cincin- nati a mechanical system has been recommended; at Louisville, Ky., and Paterson, N. J. , also the mechanical system is to be used. The specifications, however, call for a type of filters differing radically from any plant now in operation. The fact that slow sand filters have been doing highly efficient work for three-quarters of a century, under widely diverse conditions of operation, in the largest cities of the world would make the argument from experience conclusive in favor of the slow sand system, provided the Potomac River water were of the type that can be treated without the use of a coagulant at all times. The further fact was developed that the cost of the two systems dur- ing a series of years is about equal, the first cost of the lands necessary for the slow sand filter being offset by the annual cost of the alum used as a coagulant. In order to determine first whether the waters of the Potomac are of such a character as to make the use of a coagulant a necessity, and also to obtain the opinions of men who have had large experience in the installation and operation of filter plants, the committee asked for a professional report from Mr. Eudolph Hering, Mr. George W. Fuller, and Mr. Allen Hazen. This report, which has been agreed to by these three experts of conspicuous service and ability, is appended and made a part of the committee's report. In brief, they recommend the adoption of the slow-sand filter sys- tem, modified by the use of coagulation during periods of extreme turbidity in the Potomac water. This combined system has all the advantages that three-quarters of a century have shown slow sand filters to possess, and it also provides for dealing with the peculiarly turbid waters of the Potomac during those exceptional periods when the slow sand system must fail to produce a clear water without mate- rially impairing the filter beds. Xir MECHANICAL AND SLOW SAND SYSTEMS OF FILTRATION. The occasional coagulation of Potomac water at times of excessive and continued turbidity, in order to prepare the raw water for the filter beds, is a comparatively small incident in the operation, and the auxiliary works necessary thereto would be of small cost and of easy operation. On an average, during but one month in a year such treatment would be necessary. Several sites are available for filtration beds, and each has its advan- tages. The beds might be located along the line of the conduit, where land is cheap; or, if a site near the Howard University reservoir should be selected, the result would be a considerable and highly desirable addition to the park system. At the same time the pumping required to deliver the water to the filter beds would give a very considerable additional head to the gravity supply, thus diminishing the amount of so-called high service required. This additional head for the gravity system is particularly desirable, for the reason that even the comple- tion of the Howard University reservoir will not give an entirely satisfactory head of water on Capitol Hill and in certain other parts of the city that depend on the gravity sei-vice. The committee is under obligations to Mr. Hering, Mr. Fuller, and Mr. Hazen for putting aside other and pressing work and devot- ing their time continuously to the solution of an intricate and perplex- ing problem. Colonel Miller very courteously placed at the disposal of the experts all the records and resources of his office that could aid them in the prosecution of their studies, and the engineer officers of the District government did everything in their power to facilitate the investigation. The committee is also under obligations to Surgeon-General Stern- berg, U. S. A. , to Lieut. Col. Charles Smart, U. S. A. , and to Super- vising Surgeon-General Wyman and Dr. Geddings, United States Marine-Hospital Service, for special reports made at the instance of the committee. In conclusion the committee recommends for use in the District of Columbia the adoption of the slow sand system of water filtration, modified by the use of coagulants whenever the waters of the Potomac are so turbid and turbid for so long a period as to make the use of a coagulant desirable. EEPORT OF MESSES. RUDOLPH HERING, GEORGE W. PULLER, AND ALLEN HAZEN, ON THE METHODS OP PURIFYING THE WATER SUPPLY OP THE DISTRICT OP COLUMBIA. Washington, D. C, February 18, 1901. Sir: In accordance with your request, we present to you herewith a report upon the purification of the Potomac River water for the supply to the District of Columbia. This subject was investigated by Lieut. Col. A. M. Miller, Corps of Engineers, U. S. A., who, on March 28, 1900, made a report thereon to Gen. J. M. Wilson, Chief MECHANICAL AND SLOW SAND SYSTEMS OF FILTRATION. XIII of Engineers, U. S. A., which was printed as Senate Doc. No. 259, Fifty-sixth Con- gress, first session. In his studies Colonel Miller gave attention to two processes for the purification of the Potomac water. One of these is variously known as American, rapid, or mechani- cal filtration; the other, as English, slow, or sand filtration. Colonel Miller recom- mended the adoption of mechanical filtration for the Washington water supply, the plant to be located near the new Howard University reservoir. Exceptions were taken to this conclusion by a special committee of the Medical Society of the District of Columbia, which made a report dated December 5, 1900, and printed as Senate Doc. No. 27, Fifty-sixth Congress, second session. This com- mittee earnestly recommended the prompt installation of slow sand filters, on the ground that it considered them to be more reliable in purifying the water at all times, and therefore safer from an hygienic standpoint. By direction of the Senate Committee on the District of Columbia, a hearing was held at the Waldorf-Astoria Hotel in New York City on January 4, 1901, as to the relative merits of the two systems of filtration for the Water supply of Washington. At this hearing statements were made by a number of gentlemen familiar with the subject of water filtration. At j'our request the undersigned proceeded to the city of Washington, inspected the pertinent parts of the waterworks system and several sites available for filters, secured data bearing upon the problem, and conferred with ofiicers affiliated with this branch of the District service. We beg to express our obligations to all of these gentlemen for the very courteous and efficient assistance which they have rendered us in our investigations. The character of the raw water is often an element of controlling importance in deciding a question of this kind. Generally speaking, sand filters are best adapted to purifying waters that are not extremely turbid, and mechanical filters have marked advantages in the purification and clarification of waters which for considerable periods are very turbid. It was, therefore, necessary for us to examine all the avail- able evidence regarding the character of the Potomac water. At those places in this country where observations have been taken on the amount and character of turbidity of different river waters the methods used have not every- where been the same. To compare the Washington data, which cover a period of twenty-three years, with those concerning other waters which have been studied in detail we have converted them to standards with which we are more familiar and have been able to compare the results with a reasonable degree of confidence. As a result of this study we estimate that a million parts of raw Potomac Eiver water contain, as an annual average, about eighty parts of suspended matter. For the purpose of comparing in general terms the character of this water with the charac- ters of others which have been carefully studied the following table, based on the best evidence now available to- us, is presented: Estimated annual average amount of suspended matter in raw water. Parts per million. Merrimac Kiver, Lawrence. . .■. i 10 Hudson Eiver, Albany - 15 Allegheny Eiver, Pittsburg .■. -. 50 Potomac Eiver, Washington ■. 80 Ohio Eiver, Cincinnati .-. ^ - - - 230 Ohio Eiver, Louisville ^ - 350 Mississippi Eiver, New Orleans^ - - ^ 560 In the purification of river waters there are other very important factors to be considered besides the average turbidity or the weight of suspended matter. Most XIV MECHANICAL AND SLOW SAND SYSTEMS OP FILTRATION. prominent among them aie the fineness of the suspended matter during flood periods and the duration of periods of turbid water. With streams where periods of turbidity are of short duration it is often possible at such times to close the intake, thereby avoiding the necessity of treating the most turbid water. The supply in the meantime must be maintained from storage reser- voirs. We find that for Washington this procedure would not always be practicable, because the periods of highly turbid water sometimes last much longer than the period during which the supply could be maintained from the existing reservoirs, or from reservoirs which it is practicable to build. We find that the water of the Potomac Eiver at Great Falls following heavy rains is more turbid than any water which is successfully purified by slow or sand filters in this coimtry. Few exact data regarding the turbidities of European streams are available, but it is certain that none of the waters filtered by the better known Euro- pean sand filters approach, on an average, the turbidity of the Potomac water. By subsidence it is possible to reduce materially the excessive turbidity of river waters by passing them through reservoirs. According to the best evidence now available there are times when plain subsidence of this river water for any reasonar able period of time would not afford an adequate treatment preparatory to its suc- cessful purification by sand filtration. During some years this condition would not obtain, while during others subsidence might be inadequate for periods amounting in the aggregate to ten weeks and on an average to about one month each year. It is further probable that the bacterial efficiency of the process might sometimes become inadequate, due to the general disarrangement of the filters caused by excessive turbidity. This condition would be less important at Washington than it was at Cincinnati. The water of the Ohio Eiver at Cincinnati was found to be so turbid that it could not be adequately purified even after sedimentation, by sand filtration, for about 35 per cent of the time. On this basis we estimate that at Wash- ington the proportion of the time when sand filters alone would be inadequate would amount to about 8 per cent. As to the relative merits of the two systems of purification studied by Colonel Miller, namely, the treatment of plain subsided waters by sand and by mechanical fil- ters, his conclusion is correct, namely, that the latter system would be the more effi- cient and the more judicious one for the city of Washington to adopt. Since his investigations were instituted, some improvements have been made in the general processes of both slow and rapid filtration. Relative to the former, this progress appUes, for very turbid clay -bearing waters, to the use of coagulants when needed. This procedure was studied at length at Cincinnati, and is used at a num- ber of small places in Europe. It is referred to in Colonel Miller's report as the modified English system. It was not investigated by him owing to lack of funds, and in the absence of practical results he did not consider it. Within the past few months material improvements in mechanical filters have been developed in connection with several municipal water supplies. These depar- tures from former types of filters, in a measure are made possible by the expiration of the Hyatt patent. In our endeavor to solve the Washington problem we have devoted ourselves to a careful consideration of the relative merits of these two methods in their most improved forms. We have based our consideration of the problem on a daily supply of 75,000,000 gallons of water, which approximates the present carrying capacity of the aqueduct. This amount is sufficient to supply all legitimate needs of a population much greater than the present one. ^ Whenever a new aqueduct becomes necessary the question of purifying the additional supply of water thus obtained will be a part of the new problem. In our opinion it is unnecessary now to consider the purification of more water than can be carried by the existing aqueduct. MECHANICAL AND SLOW SAND SYSTEMS OF FILTRATION. XV In this connection we beg to call your attention to the large waste of water in Washington, and to suggest the advisability of taking measures to limit such waste. One of the most effective means of doing this is by the use of meters; and we recom- mend that they be placed on all public buildings at once, and on private services, when deemed necessary, as rapidly as practicable. The question of deciding between the two systems of purification, with the improve- ments above indicated, is in some respects a difficult one. In character the water for Washington is intermediate between the water for Pittsburg, where sand filters are best adapted to the conditions, and the water for Cincinnati, where American filters are preferable. If the Potomac water were more turpid, or turbid for longer periods than the records show, mechanical filters would unquestionably have the preference. If it were less turbid, or if turbid periods were of shorter duration, the advantage would clearly lie with sand filters. Practical experience with sand filters is much more extensive and more favorable than that with mechanical filters. Our knowledge of what they will do rests not alone upon experimental investigations, but upon actual use for many years by some of the largest cities of the world. The force of this statement is somewhat reduced, however, by the fact that the raw water at Washington is more turbid than the raw water at the places where sand filters have been generally used. Our knowledge as to the results that can be obtained by mechanical filters rests more upon experimental evidence than upon results obtained in practice. Neverthe- less,, these investigations have been made upon such a scale and with such care as to give the greatest confidence in their results. It appears from consideration of the evidence at our disposal that the average yearly bacterial efficiency of the two systems would be about equal. During the warmer months of the year this efficiency would probably be greatest in the case of sand filters.- When the river water is at or near the freezing point, the conditions upon which sand filters depend are less effective, and the efficiency of mechanical filters would probably be a little greater. This deterioration of sand filters would not be materially changed by covering them, as it appears to depend upon the temperature of the water while passing the filters, and this is not materially infiuenced by covers. There will apparently be but little difference in the cost of the two systems. The cost of constructing sand filters is larger than the "cost of constructing mechanical filters, but the latter are more expensive to operate; and when interest and deprecia- tion charges on the investments are added to the costs of operation, the difference between the total costs is within the limits of accuracy of the two estimates. After a full consideration of the various aspects of the problem we are of the opinion that the long and favorable experience with sand filters, particularly in the light of the effect which they have had upon the health of the communities using them, should be given greater weight than the present evidence that American filters are able to give substantially equal hygienic efficiency. In view of the fact that there is no available evidence of decided advantage to be gained by adopting the newer method, we prefer in this case to adhere to the one supported by long precedent. In regard to the exact site for filters, the short time at our disposal has not allowed us to make the necessary surveys and detailed estimates of cost to decide definitely whether a site near the new Howard University reservoir sufficient for the construc- tion of filters to purify all the water that can be gotten through the present aqueduct, or a site beyond the District limits, and near the line of the aqueduct, large enough to allow almost indefinite extension, is to be preferred. The former site has this advantage: That filters constructed upon it would be at such an elevation that the filtered water could be supplied at a greater elevation than that which would be available from the Howard University reservoir. It may be found upon further XVI MECHANICAL AND SLOW SAND SYSTEMS OF FILTRATION. study that this additional pressure will justify the somewhat greater cost of filters in this vicinity. In consideration of the full evidence we recommend the construction of a com- plete system of slow or sand filters, with such auxiliary works as may be necessary for preliminary sedimentation, and the use of a coagulant for a part of the time. There is no reason to believe that the use of this coagulant will in any degree affect the wholesoraeness of the water. EespectfuUy presented. Rudolph Hisung. Gbokge W. Fuller. Allen Hazbn. Hon. James McMillan, Chairman Senate CommiUee on the District of Columbia, Washington, D. C. PURIFICATION WASHINGTOK WATER SUPPLY. w s— 01 1* PURIFICATION OF THE WASHINGTON WATER SUPPLY. CHAPTEK I. STATEMENTS MADE AT A HEAEING HELD AT THE -WAIiDOEF- ASTOBIA HOTEL, NEW YORK CITY, JANUABY 4, 1901. Bj'^ direction of the United States Senate Committee on the District of Columbia, an inquiry into the relative merits of the mechanical and the slow sand systems of filtration for the water supply of the District of Columbia was held at the Waldorf-Astoria Hotel, New York City, on Friday, January 4, 1901. The persons present at the request of the committee were: Lieut. Col. Alexander M. Millek, United States Corps of Engi- neers, the officer in charge of the Washington Aqueduct. Dr. William C. Woodward, the health officer of the District of Columbia. Dr. J. S. Billings, director of the Consolidated Libraries of New York City. Prof. William P. Mason, professor of chemistr}^ at the Rensselaer Polytechnic Institute, Troy, N. Y. Mr. Allen Hazen, C. E., St. Paul Building, New York City. Mr. George W. Fuller, consulting expert in water purification and sewage disposal, No. 220 Broadway, New York City. Mr. Edmund B. W^bston, consulting engineer. Providence, R. I. Mr. John W. Hill, hydraulic engineer, Cincinnati, Ohio. Mr. Rudolph Hering, C. E., No. 100 Williams street, New York City. Mr. John M. Diven, superintendent of the Elmira, N. Y., filtra- tion plant. Mr. George A. Johnson, bacteriologist, St. Louis, Mo. The inquiry was informal in character. Senator McMillan, chair- man of the Senate Committee on the District of Columbia, having been detained by the delay in the arrival of the western train, Mr. Charles Moore, the clerk of the committee, called the meeting to order, and he also presided at the afternoon session. Colonel Miller, who is charged with the construction of the District filtration plant, and Health Officer Woodward questioned those who testified. The 4 WASHINGTON WATER SUPPLY. hearing began at 10 o'clock in the morning, and was continued, with two short intermissions, until half after 5 in the afternoon. The Senate resolution ordering the inquiry is as follows: In the Senate of the United States, December 20, 1900. Resolved, That the Committee on the District of Columbia be, and it is hereby, directed to investigate and report to the Senate, at the earliest practicable date, the relative advantages of the so-called mechanical system and of the slow sand system of water filtration for cities; and the necessary expenses of such investigation shall be paid from the contingent fund of the Senate. The first person called upon was Dr. J. S. Billings, formerly a sur- geon in the United States Army, and now the director of the consoli- dated Astor, Lenox and Tilden libraries in the city of New York. STATEMENT OF DE. J. S. BILLINGS. Dr. Billings. 1 have seen the operation of the slow sand system of filtration at Hamburg and at several other places in Europe, particu- larly in England, during my experience in charge of the department of hygiene in the University of Pennsylvania. I have observed the results of some experiments with the Chamberland pressure filters. With the patent mechanical filters I have had no experience. With the general literature on the subject up to four or five years ago I am tolerably familiar. It was part of my work as a teacher of hygiene to lecture on filtration, and I have followed the matter, although not in detail, for the past four or five years. I have glanced over the report of the engineers on the experimental filters at Washington, and have looked over the little pamphlet sent me by Senator McMillan, containing the report of the Medical Society of the District of Columbia on that subject. I have looked over the reports as to the experimental preparatory filters at Pittsburg, just published, and the reports of the filtration of the Massachusetts board of health at Law- rence, Mass. That is the best answer I can give as to my experience, or as to the grounds for forming an opinion. I do not pretend to be an expert in the matter. Mr. MooKB. Have you made up your mind as to the respective merits of the English or slow sand system and the so-called American or mechanical system ? Dr. Billings. I think the question must be settled from special data in the case of each individual city. Neither system has any such marked superiority over the other that it is to be preferred at all hazards and at all costs. Mr. MooEE. Are you satisfied that the mechanical system can pro- duce as good results, under proper care, as the slow sand system? DK. J. S. BILLINGS. 5 Dr. Billings. No, sir; but I can not give details or undertake to criticise tiie mechanical system. As I say, I have not examined that system thoroughly, but the slow sand filter I am familiar with. 1 would not pretend to pass judgment upon the abstract question. In the particular case of Washington, however, I would, on the whole, from what I know of Washington — and based upon the facts given in these I'eports — prefer to adopt the slow sand filter. PRESSURE FILTERS NOT EFFICIENT. Colonel Miller. You speak of the mechanical or American method, and you speak of pressure filters. Now, I think, as a general rule, it has been agreed that the pressure mechanical filter is not an eflicient method for hygienic purposes. The method proposed in my report is not a pressure filter. The report proposes a gravity system, involving the use of coagulants, by which rapid filtration is secured. You stated, in the first part of your remarks, that it depended upon the individual city as to which filter was the best to adopt. What discrimination do you make in that respect? Dr. Billings. Well, in the first place there would be the procuring of a sufficient area for slow sand filters, which in the case of some cities might be impossible, or possible only at an enormous cost. That should be considered. Colonel Miller. In the case of the sanitation of a great city that does not enter much into the consideration. Speaking hygienically, what are the reasons why you prefer the American system, or the mechanical method to slow sand filters? Dr. Billings. I prefer the slow sand filters, because their efiiciency has been thoroughly demonstrated, and the efficiency of the mechanical system I do not think has been demonstrated for large cities. Colonel Miller. Your experience has been gained from the obser- vations at Hamburg, and of some other foreign filters ? Dr. Billings. Yes; and other large systems. Colonel Miller. The slow sand filter is the only system that is used abroad. Do you consider that the slow sand filter is eflScient where the water is continually roily or turbid, and contains finely divided matter ? Dr. Billings. It is satisfactory from a sanitary standpoint, although it may not always give a clear effluent, and it may be more costly by reason of requiring more frequent removals of the deposits from the surface of the sand, and the breaking up of the bacteria deposit on the surface of the sand causes a lower efficiency for a time. Colonel Miller. Are there any objections to be raised against the American system on the score of the passage of alum through the filters ? 6 WASHINGTUW WATER SUPPL'T, Dr. Billings. As to that, I have no positive knowledge. I should judge from the reports that there are not. I think that alum does not appear in the effluent. Colonel Miller. It depends upon the water? Dr. Billings. Yes, sir; but I do not think my opinion is very valu- able upon that subject. Colonel Miller. Then you have not formed any very strong opin- ion on the subject? Dr. Billings. No; not sufficiently to put myself in the position of an advocate of one system over the other in all cases. THE FIVE ESSENTIALS IN FILTRATION. Dr. Woodward. From the standpoint of a general water supply there are, I think, five points to be considered with reference to the effluent. The first is the character of the effluent as shown bj^ the typhoid fever death rate; the second is the character of the effluent as determined by simple bacterial purity; the third is the quality of the water from the standpoint of clearness; the fourth is the quality with reference to the consumption of soap by the community, and the fifth is the effect of the effluent in causing incrustation upon steam boilers. Is not that the proper order of importance? Dr. Billings. I should think that would be the proper order. The influence upon typhoid fever is the one that will come up. most fre- quently for consideration in this country. The effects relative to cholera should also be considered, and I should perhaps modify that suggestion as to typhoid fever so as to include diseases, which may be caused by water-borne organisms, etc. Dr. Woodward. Of course, in this country we take typhoid fever as the typical water-borne disease. I used it only in that way. With reference to the correspondence between the bacterial efficiency and the probable typhoid-fever death rate, should we expect the death rate from water-borne diseases to vary as the bacterial efficiency of the filter — that is, to vary with the number of organisms taken out; or, we may say, with reference to the bacterial deficiency — I mean the ttumber of organisms that remain in the water. Dr. Billings. You mean the number of the specific organisms that remain in the water? Dr. Woodward. The number that remain in the water, rather than the number taken out. You have never, I judge from your state- ment, gone into the question of the relative efficiency of these two systems in the removal of the colon baciUus. Dr. Billings. No. I should judge from the Washington reports, from the Pittsburg report, and also from the Massachusetts reports, that the statements given were probably accurate as to that point. PEOF. WILLIAM P, MASON. 7 Dr. Woodward. Do you know of any standard with reference to the turbidity of the water from a sanitary standpoint — any fixed standard? Dr. Billings. I do not know of any. Dr. "Woodward. A slight degree of turbidity, if occasional, would be objectionable or unobjectionable from a sanitary standpoint? Dr. Billings. If the turbidity were due merely to extremely fine particles of alumina or clay, I do not know that there would be. Dr. Woodward. But with a high bacterial efficiency, would you be inclined to regard as important a slight degree of turbidity in the effluent? Dr. Billings. The superior efficiency of a filter in regard to remov- ing infectious forms of organism I should consider of greater impor- tance than its efficiency in removing slight turbidity. Colonel Miller. Is there such a thing as typhoid fever being en- demic to localities ? Dr. Billings. Well, in one sense, the common sense of the word, yes. The specific organisms appear to be closely connected or identi- fied with certain places and pretty much absent in other places. Colonel Miller. With reference to that, how does Europe, and the Continent generally, compare with this country in that respect? Dr. Billings. 1 think the statistics show more typhoid in this country than in Europe, as a rule. There are localities in Europe where typhoid is very prevalent; but the conditions for a particular place may change. Colonel Miller. Of course there may be local conditions, but as a general rule do you think this country is more liable to typhoid than Europe ? Dr. Billings. As I remember the statistics of the large cities of this country (I have had charge of the compiling of the vital statistics for the last two censuses prior to this), for the cities of 100,000 inhabitants and upward the proportion of typhoid is larger in this country than it is in the European cities. Colonel Miller. I know that in Grermany the rules as to the use of water are very strict. Is there a law there requiring the population to use filtered water where such water is furnished ? Dr. Billings. I do not know. It would be difficult for the people to use any other water in such places as Berlin or Hambui-g. STATEMENT OF PROF. WILLIAM P. MASON. Mr. Moore. Professor Mason, what has been your experience in regai'd to water filtration ? Professor Mason. Well, I have spent a good many years upon the water question, and have considered generally a great number of questions relative to water filtration by various methods. 8 WASHINGTON WA.TEB SUPPLY. Mr. Moore. You were, I believe, connected with the Albany filter plant? Professor Mason. No, I never was. I was asked by the board of health in that city to express an opinion with reference to the method of filtering the Albany supply. As early as 1885 I advocated putting in the plant which they now have. If they had put it in sooner, more lives would have been saved. Mr. MooEE. The Albany plant is a slow sand filter system ? Professor Mason. Yes, sir; the English bed. Mr. Moore. At the time the Albany plant was built was the mechanical system much used to filter the water supply of cities? Professor Mason. Yes; the mechanical system was pretty well known then. Mr. Moore. I understand that you have prepared a paper setting forth in some detail your views on the subject. Professor Mason. Yes; I have. The reason T prepared this paper was that at the time Senator McMillan sent me the Washington reports I did not know exactly what would be the nature of this meeting, so I prepared a statement. I may say that I wrote it without any knowl- edge of the local conditions at Washington. 1 have seen the Potomac River from the cars onlj^, and all 1 know about the situation is what I get from the printed matter furnished. when the slow sand filter is preferred. I have read Senate Doc. No. 259, Fifty-fifth Congress, third session, relative to experiments conducted to determine the feasibility and propriety of filtering the water supply of Washington, and have also read Senate Doc. No. 27, entitled "Relative Merits of Slow Sand and Mechanical Filtration" (both documents having been sent me by Hon. James McMillan, United States Senate), and I beg to offer the follow- ing comments thereupon: After a pretty wide experience in matters connected with the puri- fication of municipal water supplies, I have concluded that, where local conditions do not intervene to affect the choice, the following general rule may be safely followed in selecting the type of a proposed filtra- tion plant: First, I believe in the English bed for great cities using fairly clear raw waters; and secondly, I recommend mechanical filtra- tion for very roily waters, and for small places, irrespective of the character of the raw supply. No hard and fast rule can, however, be laid down, as each case must be judged upon its own local conditions. Thus, not long since, I recommended filtration for two cities using the same raw water, but in one case I proposed the use of an English bed, and in the other I suggested a mechanical plant as best suited to the city's needs. PROF. WILLIAM P. MASON. 9 It must be remembered that roily waters may vary one from the other to a material extent, even when the degree of turbidity i.s the same; for equality in turbidity does not infer equal fineness in the particles producing such turbidity, nor does it predicate an equal power on the part of such particles to form themselves into larger aggregates. Thus with, the same degree of turbidity two waters might give vevy different filtrates after passage through an English bed. It is because of such variations in raw waters that experimental filter plants are established with a view of determining whether or not a proposed plan of purification is suited to the water under considera- tion; for it has been found that the results obtained in one localitj^ may not answer for the conditions existing in another. Had I been asked to give a snap-shot opinion as to the best form of filter for Washipgton, my reply would have favored an English sand bed, for I incline to such form of filter for so large a city unless there be special evidence showing some other form better suited to the local conditions. THE WASHINGTON TESTS. Of course the best manner in which to arrive at a just decision touching upon the selection of a municipal filter plant is to make prac- tical tests of the forms proposed while they are operating upon the water that the chosen one will be expected to purify. Such test Washington has made, and I have read with interest the record of results. I have also read the comments made upon these above-mentioned results by the special committee of the Medical Society of the District of Columbia (as given in Document 27), and I feel that in some respects such conaments and criticism almost take the form of special pleading. For instance, I do not see the wisdom of allowing the public to infer that in some instances mechanical filtration of city water has been a direct cause of a decided increase in typhoid fever. No one who knows anything about filtration believes that to be a fact; and, more- over, so far as two of the cities are concerned where such strange results are claimed, namely, Elmira, N. Y., and Lexington, Ky., I chance to know that the true state of things is quite the reverse of this and that the filters have greatly improved the typhoid death rate. With reference to the remaining town I have no data. Referring again to the medical society's criticism, I do not think it was well to include the figures on page 41 of Colonel Miller's report when striking the general average for comparison between the filters, for the reason that the mechanical filter was idle a large fraction of that time, and, moreover, because the eflSciency of that filter on December 27, 28, and 30 was so poor as to show a manifest and pre- ventable error somewhere. The run from January 6 to March 2 is a 10 WASHINGTON WATER SUPPLY. fairer period for comparison, omitting from the record, however, the work of the English filter bed for January 8, which is surely an error. Striking the averages upon this run, we have the efficiency percent- ages as follows: Per cent. English filter bed 97.64 Mechanical filter 98. 60 Placed in graphic form, the ' ' curves " showing the number of bacteria yet remaining in the filtrates from the two filters are given in the accompanying chart. The relative averages of 88.9 and 86.9 per cent for the entire run of two hundred and sixty -six days are of little value, for such low per- centages are entirely inadmissible in any form of plant whatever, except when the actual count is very low. The continuous running of the English bed and the interrupted work- ing of the mechanical plant is commented upon as unfair to the former. Suc„ a statement is in error. Interruption in operation is of no advan- tage to a filter, and often may be quite the reverse. On page 5 of document 27 it is stated that the "percentage of germs which remained in the water from the alum filter was 70 per cent larger than the percentage of germs remaining in the water from the sand filter." This statement is an error, if the calculation be based, as it should be, on the run recorded on page 42 of Colonel Miller's report; but aside from all that it must be remembered that percentages in such form may be very misleading. For instance, on February 17 the per- centages of bacterial removal for the two filters were: Per cent. English bed 99.3 Mechanical plant 99. 9 Such results are practically perfect, and are consequently to be con- sidered as practically identical. How unfair it would be, therefore, to state that the English bed was passing so many germs as to be 60 per cent inferior to the mechanical plant. With reference to the question of the use of alum by a mechanical filter and its possible eilect upon the health of the community drinking the water, it almost needs an apology at this late day to remind the people that free alum in the filtrate from a municipal plant is an evi- dence of carelessness on the part of the management not to be tolerated for a moment. It should be as carefully guarded against as the scrap- ing of an English sand bed to undue thinness by successive cleanings. No alum reaches the consumer, and the aluminum hydrate formed goes to the sewer with the removed dirt. The change in the chemical composition of the water by the use of alum is a turning of carbonate of lime into sulphate of lime, which is a change without significance from a hygienic point of view, but one PROF. WILLIAM P. MASON. 11 which is unpopular with the steam users, because the scale formed by the sulphate attaches itself more firmly to the boiler tubes than does that resulting from the presence of carbonate of lime. It is, I think, unfortunate to make use of the expression "sulphuric acid" when speaking of the operations of a mechanical filter. It is unnecessary, and, moreover, it frightens the uninitiated. Sulphates are involved in this form of filtration, but no free sulphuric acid. Would anyone think it wise to refer to the use of "hydrochloric acid " as a part of our daily food, when the real meaning intended was its combined form in the shape of common salt? CONCLUSIONS. In conclusion, let me say that although, in the absence of experi- mental information, I should have favored an English filter bed for Washington, yet now that a practical trial has been made under the direction of reliable and competent men I should consider it great lack of wisdom to attempt to question their findings or to discredit their recommendations. BACTERIAL EFFICIENCY. Dr. Woodward. As to the various qualities of the efiluent of a filter, stated in the order of their relative importance, will you please specify them, if you recall them. Professor Mason. I recall them. I should place the passage of dis- ease germs through a filter as of first importance. Dr. Woodward. In arranging the relative importance of the quali- ties of the effluent, would you place first the death rate from water- borne diseases? Professor Mason. That I should place first. Dr. Woodward. The value of water as indicated by bacterial counts. Professor Mason. That should be second. Dr. Woodward. The clearness of the water as indicated by the naked eye. Is that of sanitary importance ? Professor Mason. No, sir; that is not of sanitary importance. Dr. Woodward. Now, with reference to soap consumption? Professor Mason. That is an item. Dr. Woodward. Then, with reference to hard boiler scales? Professor Mason. That is also an item. Dr. Woodward. Are those fairly arranged in the order of their importa.nce ? Professor Mason. I should say that that was about as good alist and order as one could make out. Dr. Woodward. Now, with reference to the statistics furnished by the medical societies of Elmira and Lexington, do you know of any more reliable statistics? 12 WASHINGTON WATER SUPPLY. Professor Mason. Yes; I have some myself from Elmira. I was in charge of that plant, running it under an order of the United States court; so I know all about it. I ran that plant for eight days. Dr. Woodward. I mean with reference to the typhoid fever death rates. Professor Mason. I think you refer to the germ. Dr. Woodward. No; I am referring solely to the number of deaths that occurred from typhoid fever, as obtained from official sources in the two cities. We would be glad to learn better, if we are in error. Colonel Miller. Dr. Woodward, you only take one year before and one year after the filter plant was installed, and you then get one death more in the second year, and say there is an increase of 10 per cent in typhoid fever. If that poor devil had died on the 31st of December, you would have changed your percentage to the other side. An increase of 1 death, or from 10 deaths to 11, is hardly fair. Dr. Woodward. That is indicated fairly, 1 think; the report shows the period covered by the data. Professor Mason, have you any criti- cism to offer with reference to the relative eflEiciency of the two systems, as indicated by those figures ? Professor Mason. Now you are asking me to refer to cities like Atlanta and Chattanooga? Dr. Woodward. No; the cities that are compared in the Medical Society's report — Lawrence, Mass. ; Ashland, Wis. ; Hamilton, N. Y. , and Mount Vernon, N. Y. — all using sand filters, with an average reduction in the number of deaths from typhoid fever of 78.5 per cent.. Then Macon, Ga. ; Atlanta, Ga. ; Oakland. Cal. ; Reading, Mass. , using mechanical filters, showing an average decrease of 26 per cent. COMPARISON BY CITIES. Professor Mason. You must bear in mind in comparing those groups of cities, that when you are talking of Ashland, Wis., you are speak- ing of a really good up-to-date English filter bed. When you speak of Lawrence, Mass., you are speaking of a .carefully run filter bed a little different from the English type. But when you speak of cities like Atlanta and Macon, Ga., you' are not referring to the kind of filter that has been proposed for the city of Washington. The Atlanta and Malcon filters are not very good filters. They are of what is called the pressure type, and it is hardly fair to compare them with the open gravity form of filters such as are used at Elmira, N. Y. , and Lorain. I think it would be better to confine the comparison between the Eng- lish filter bed and the open gravity mechanical plant, which has been referred to in Colonel Miller's report. Dr. Woodward. With reference to that point, is it possible to get water to go through a given amount of filtering material at the rate PEOF. WILLIAM P. MASON. 13 of 130,000,000 gallons per acre per diem without more pressure than is required to filter water through the same material at the rate of 3,000,000 gallons per acre per diem; is not the pressure in the former case very considerably greater? Professor Mason. No. If you are at all familiar with open filters, you must know that it is a question of atmospheric pressure. Those are open tanks. Dr. WooDWAED. The current goes through at a considerably greater rate than in the other filters? Professor Mason. No; there is no pressure from the main. Dr. Woodward. But the amount of force exerted in twenty-four hours, would you regard that as the same ? Professor Mason. It could not be. If you drive a stream of water at the rate of 3,000,000 gallons a day through a sand bed, and another at the I'ate of 125,000,000 gallons, there is unquestionably a difference in pressure. At the same time I wish to distinguish between the open gravity mechanical and the close pressure mechanical, because I think there is -a great deal of difference in the efficiency. Dr. Woodward. Are there any large cities using the open mechan- ical filter ? Professor Mason. No, I think not, what you would call a great city; no city of the size of Washington. Li. Woodward. What is the largest city you know of? Professor Mason. I do not know the population of the towns named. Elmira has 36,000 population. That is hardly a laige city. WHAT THE WASHINGTON FIGURES SHOW. Dr. Woodward. With reference to the figures on page 41 of Colonel Miller's report, I notice that while you disregard certain days for the mechanical filter, you have apparently not disregarded more than one day for the sand filter. Did you notice that the figures for that filter run continuously from December 1 to 31, while as a matter of fact the report shows that "On December 27 the loss of head was 2.30, and the filter began to show signs of breaking through, and it should have been shut down and scraped." The weather was very cold, however, so that the filter was allowed to run until January 5; that is, from December 27 to January 5 before it was cleaned. Would you not dis- regard the figures from December 27 to January 6, and for a certain length of time after January 5, because of the pollution of the sand by the passage through it of this imperfectly filtered water ? Professor Mason. As I said, I threw that entirely out of considera- tion. Dr. Woodward. Then you took the average for the entire period? Professor Mason. No; I did not. I took the average on page 42. I think that on page 41 the record is so broken that it is hardly wise 14 WASHINGTOIir WATEK SUPPLY. to take it. I did not take the bottom of page 41. There is something the matter with that mechanical-plaut record for that part of the run. Dr. "Woodward. Is there not something the matter with the sand plant, as just stated? Professor Mason. Yes; I think there is; and for that reason I think t is wise to throw it all out and take page 42. I should throw the record out for January 8 for the sand plant, because that is not a fair figure for the sand plant. The sand plant can do vastly better than that. Dr. Woodward. If the sand plant was left to operate from December 27 to January 5, when it should have been shut down, would you not expect to find some effect upon the effluent for some time after it was started again, after simply scraping? Professor Mason. Yes; there is some inefficiency in the plant just after scraping. Dr. Woodward. Especially if the sand has been polluted by this impure water? Professor Mason. I do not understand that point. Dr. Woodward. The official report shows that on December 27 the filter should have been thrown out of service; the effluent was bad; the loss of head was great; but it was allowed to run until Januar}'^ 5. Would a simple scraping restore a filter of that sort? Professor Mason. Yes; I should expect it to. Dr. Woodward. Although it had a crack in it? Professor Mason. How deep did that crack extend ? Colonel Miller. What do you mean by having a crack in it ? Dr. Woodward. The fissure referred to over the pet-cocks? Colonel Miller. That was immediately stopped. There was an effort made, as had been made before, to find out the bacterial effi- ciency of the filter at different depths in the sand, and in order to obtain that pet-cocks were inserted in such manner that they would not come over one another, but just down to a certain depth; and I think you will find from my report that after the first scraping it brought an undue strain on that side of the filter and made a slight separation there. We shut down in that run because we were unable to stop the filter on account of the severity of the weather. If we had stopped filtering, our filter would have frozen solid; or, if we had drawn the water off and stopped filtering, the sand would have frozen, which would have destroyed the filter for all practical purposes. That was the reason we were obliged to let the filter run during that severe weather. Those tables which appear in the report are not selected at all. They are just exactly as they ran from day to day. The averages were taken without any regard to that point. I think you will find, among the averages taken by Dr. Kober, three or four days that the filter bed was allowed to run without coagulant. I wanted to see PBOF. WILLIAM P. MASON. 15 exactly what the thing would do without a coagulant, and these days have been lumped in getting the averages there. Dr. Woodward. Mr. Hardy was apparently of a different opinion. He states : On draining the filter a very noticeable crack in the schmulzdecke was detected, run- ning along the periphery of the tank, just above the pet-cocks. The length of this crack was about 11 feet. Colonel MiLLEK. What date is that? Dr. Woodward. It was about January 3. He says: It is believed that the bad results from the filter during the latter part of the run, as well as the samples drawn from the pet-cocks, were caused by this crack. Colonel Miller. Mr. Johnson, do you remember when we stopped drawing from there ? Mr. Johnson. I do not know specifically, but know it occurred immediatelj^ after getting those first bad results. Colonel Miller. It was before this Januai'y arrangement — it was much before that. It was discovered, I think, on the first scraping. As to Mr. Hardy's report, you must remember that although you call him an expert in your report, I do not think any of these gentlemen would admit it. He was merely an assistant for the detail working of the arrangement, and not an expert. Dr. Woodward. Have you any knowledge as to the general bacterial efficiency of these two Washington experimental filters during the entire period? I do not mean the average of the daily samples but taking the total number of bacteria in the samples examined of the influents and effluents. Professor Mason. Don't you call that 88 per cent and a fraction and 88 psr cent and a fraction ? Dr. Woodward. That is the average of daily runs given by Colonel Miller in his report, not the percentage of the total possible number of bacteria in the samples of the influent and effluent examined. Do you know what the general showings are with reference to the relative bacterial efficiency of the two systems of filtration ? Professor Mason. In general, I see no difference between them. If I did I would very quickly settle down upon the better one for general recommendation to towns. I see no difference between the mechanical and the English bed in general. THE CINCINNATI REPORT. Dr. Woodward. I find this in the Cincinnati report, made, I believe, by Mr. Fuller, on page 377: In the purification of those classes of water for which the English type of filters is strictly applicable, the available evidence indicates clearly that this method is a satisfactory one when the filters are properly constructed and operated. Further, so 16 WASHINGTON "WATER SUPPLY. far as our knowledge goes, this method is ordinarily somewhat more efficient and more economical for water for which it is readily applicable than any other process of purification which has received serious attention. Do you agree with that? Professor Mason. Well, if you have a water that is not too muddy, supplying a large city, I agree with that statement so well as to always advocate an English bed. Dr. Woodward. What do you mean hy "too muddy? " Professor Mason. As to that, you will have to let me see a sample of the water. Dr. W^OODWAKD. Is there any reliable method of determining that point? Professor Mason. Oh, yea, sir; my method is the reliable method. [Laughter.] Dr. Woodward. Well, knowing your reputation, I am inclined to agree with you, but you might, for the benefit of the record, state it. TESTS of turbidity. Professor Mason. I should determine the degree of turbidity by comparing the turbid water with perfectly clear water to which a standard degree of turbidity has been added, and I would state the turbidity as so many parts per 1,000,000. For instance, if I say that the turbidity of the water is 14, I mean that it is so turbid as to exactly match the turbidity of distilled water to which 14 parts per 1,000,000 of clay have been added. Dr. Woodward. Have you examined the method of determining turbidity as followed in the Washington investigation ? Professor Mason. I do not know how that method compares with Mr. Hazen's method. Dr. Woodward. I believe it differed from Professor Hazen's method with reference to the accuracy of the readings, using the vernier for that purpose, and also with reference to the use of a strongly turbid water for the dilution of the effluent. Then the result was obtained by a certain formula. Colonel Miller. That is nothing but the grocers' rule, namely, given the prices of different teas to find the price of the mixture. Dr. Woodward. Does the turbidity of the water vary in direct pro- portion to the number of suspended particles; does the refraction and reflection of light vary directly or in some other proportion ? Professor Mason. It does not vary directly; that is, with an abso- lutely close calculation; but for ordinary purposes I think that the people would better understand the statement that twice the amount of clay being added you will have twice the degree of turbidity. Dr. Woodward. Better than in a sanitary report where you are writing the report in ten-thousandths? PROF. WILLIAM P. MASON. 17 Professor Mason. Yes; there is a discrepancj'. Dr. Woodward. And in a calculation of that delicacy would you regard it as necessary to take into consideration the light unit — would that influence the result? Professor Mason. Yes; it would. Colonel Miller. If they are all made under the same light, they are all comparable; there are the same conditions, as far as possible. Professor Mason. The light will make a difference. Dr. Woodward. Do you know how many companies there are at present controlling the output of alum, and the source from which it is derived, with reference to the possibility of a combine ? Professor Mason. No; I have no idea. Mr. Moore. Can you at all times get clear water from a slow sand filter — what you would call a reasonably clear water? Professor Mason. Oh, yes; there is no doubt about that. Reason- ably clear water, however, is a pretty indefinite term. Mr. Moore. If a slow sand filter were installed in Washington, is it your opinion that at all times the appearance of the water would be satisfactory to the average consumer? Professor Mason. I should think likely, although from the report I see that you do not get an absolutely clear water. Of course, the question of what is going to be satisfactory to the consumer is a diffi- cult question to answer. Up in Troy anything short of soup would be satisfactory. [Laughter.] I think that the man who is called on to put in the plant has to solve that question for himself. He sees the water that is being delivered, and, in his judgment, he pronounces it one that the people will be satisfied with. Of course, if it is abso- lutely clear he knows that they will be absolutely satisfied with it. If it is not absolutely clear, he thinks they will be satisfied with it, and takes his chances. Mr. Moore. In Washington during portions of the year we have -what might be called clear water. Dr. Woodward. Colonel Miller can probably speak with reference to its absolute clearness. Colonel Miller. In my report I have followed the standard used by most experts, namely, the Hazen scale — of twenty -five thousandths; that is, 0.025 is considered satisfactory water. Mr. Hazen. There is a difference of opinion as to that. I think in Pittsburg we- had 0.02 instead of 0.025. Colonel Miller. That difference, as Dr. Mason says, is insignificant. You say two one-hundredths, disregarding the five one-thousandths. Dr. Woodward. Of course the people would accept a water that the expert might not pass, for the reason that people generally use water in small quantities and would not detect what an expert would immediately recognize, w s— 01 2* 18 WASHINGTON WATER SW'PI'^.Y- Mr. Moore. Professor M^qq^ would you conclude, from the data jou tiave at hand, that the slow sand system in Washington would give an effluent satisfactory in appearance and of undoubted bacterial effi- ■ciency ? Professor Mason. Yes. But to repeat: the words of that letter which I have read, you have put this matter in charge of reliable men, and when they come to their conclusion, there is no reasom why you should not accept it. I believe that the sand; filters will do well. They have achieved results which show their efficiency. The mechanical filter appears at least equally good; and fOr other reasons which they do not state, probably from the general appearance of the water, the men who made the Washington tests seem to incline toiward the mechanical filter.. Mr. Moore. What is the difference in the cost oi the two systems? Which is the cheaper system? Professor Mason. Well, the English bed is more expensive to install and the mechanical plant is the more expensive to manipulate.. Mr. Moore. So that in a given number of years the expense of the two would be equal. Professor Ma^on. They would come pretty near each oither. Of course there is this trouble with the mechanical plant,, namely, the length of its life. With reference to that we have no data oi value. We do not know how long the mechajjical filter wili live. I see that the allowance of twenty yeairs- has been made for the parts called the perishable parts of the mechaoaical plant. I shojjild put it at about thirty years. I dp not know upon what that estimate was basedv THE ELMIRA PLANT. Mr. Moore. You spoke about your operation of the Elmira plant for eight days. Will you give some details as to what the results were? Professor Mason. The Elmira plant at that time was giving a bac- teriological' efficiency of 97+; 1 do not know the fraction. The appearance of the water was perfect; it was brilliant and clear, and there was no alum in the filtrate. Mr. Moore. What do you regard as the proper figure for efficiency from a bacteriological standpoint? Professor Mason. I wouMs get as near 99 as I could. Mr. Moore. What would you say is permissible? Is there not a limit in Germany ? Do not the Germans throw out of operation a filter that does not reach a certain. degree of efficiency? Ptof^ssor Mason. They have some pretty stiff laws there. 1 should say we ought- to get over 97. I think that is a generous allowance. They are doing better than that at Albany. PROP. WlBiLiAM P. MASOII. 19 Mr. Moore. Is there any. established type of naechanical filter; or would you make a mechanical filter to suit your own ideas, the same as you would draw up specifications for a house, or anything of that kindi Professor Mason. Under certain circumstances I would make a mechanical filter to suit my own ideas, more particulaTly when there was an excessive amount of sediment to be removed, on the ground that possibly the arrangement made in a typical plant, as supplied by the companies, might not give sufficient opportunity for sedimentation; but for the average run of water I would take the plant as the makers furnish it. It would hardly pay to go to the expense of a special plant. Dr. Woodward. One more question. Can the efficiency of 97+ for so short a period as eight days be compared fairly with the efficiencies that obtained continuously with the sand-filter beds generally ? Does not the efficiency, year in and year out, of a sand-filter bed exceed that figure ? Professor Mason. Yes. The sand-filter bed at Albany at present is running 99.45, which is very good, but I have seen reports from mechanical plants, covering quite considerable periods, that are prac- tically as good. Dr. Woodward. Comparing the figures given, allowing you 97+, or even 98, there remain in the water 2 per cent of the bacteria? Professor Mason. Yes. Dr. Woodward. The figures from the Albany plant just given by you would leave in the water one-half of 1 per cent of bacteria ? Professor Mason. Yes. Dr. Woodward. So that the number of bacteria in the water would be three times as great in the effluent from, the mechanical filter as in the effluent from the sand filter? Pl-ofessor Mason. Yes. COLON BACILLUS. Dr. Woodward. And even supposing that the bacterial efficiency of each filter with reference to the colon bacillus, and therefore pre- sumably with reference to typhoid bacillus, was the sarne, which is not admitted, the chances of contracting the disease would be three times as great with the effluent from the mechanical filter as with reference to the effltient from the' sand filter. Is that not a fair statement? Ptof essor Mason. Now that is first-rate arithmetic but yery poor filtration, for this reason: I have illustrated that. I have taken the run for those two filters that you havie in Washington f br two days and" Dt. Woodward. Siippose we confine the discussion to the particular 20 WASHINGTON "WATER SUPPLY. cases cited; that is, the two instances. Is there any error in that reasoning? Professor Mason. Yes; there is a heap of error in that reasoning. I will have to go back to my illustration to show it to you. Where you get a high eiEciency — up in the nineties or between 97 and 100 — in the shape of percentages, you get a very misleading result. I showed you that in my illustration. I said you have two filters, one is running 99.9 and one is running 99.3. If you reason on those two figures you will have a difference of 60 per cent in the eflSciency. That is all wrong. There is no practical difference between 99.9 and 99.3. Dr. Woodward. That is with regard to the efficiency, but disre- garding the bacteria that you have taken out, which we will admit do not hurt anybody, the bacteria that you have left in the water are the dangerous bacteria. Will you not admit that the danger from the bacteria in the water is, so far as we are able to calculate at present from our bacteriological knowledge, in proportion to the number of of bacteria left in it? Professor Mason. My dear sir, no; not when you get up your num- bers as high as that. Dr. Woodward.' Those are low numbers, if jou will excuse me, as to the bacteria left in. Professor Mason. To return one moment to that illustration, if you will pardon me. If you get an efficiency of 99.9 and 99.3 we are deal- ing with one-tenth and seven-tenths. There is no difference between the figures. Dr. Woodward. Although one contains seven times as many bac- teria as the other? Professor Mason. Precisely. Although one contains seven times as many bacteria as the other. If you take a filter that runs 99.3 to-day and another which runs 99.9, those figures will reverse in time. Any such figures show perfect filtration and are to be considered identical. Dr. Woodward. Suppose I give you the figures that have actually resulted from the experiments in Washington during the entire period. Assume, for present purposes, that wherever the number of bacteria per cubic centimeter is given in Colonel Miller's tables, it is the result of the examination of just one cubic centimeter of water. Then the total number of bacteria found in the influent of the slow sand filter was 758,604, and in the effluent, 15,38-1:. The total number found in the influent of the mechanical filter was 729,314, and in the effluent, 19,425. In other words, the effluent from the slow sand filter con- tained 2.03 per cent of the possible bacteria, and the effluent from the mechanical filter contained 2.66 per cent. Would you or would you not regard the effluent, containing 2.66 per cent of the bacteria in the raw water as more dangerous than the effluent containing but 2.03? ALLEN HAZEN, 21 Professor Mason. Is that for the whole run? Dr. Woodward. Yea, regarding, however, December 27 as the end of the fourth run of the slow sand filter, as indicated by page 62 of Colonel Miller's report, but even including the figures for the beginning of the fifth run when the filter was undoubtedly polluted as result of use from December 27 to January 5. "Without reference to, or con- sidering the two experimental filters, but simply for the sake of the argument, is it not the number of bacteria in the effluent and not the number left in the filter that indicate the danger in the water? Professor Mason. Yes; as to the general proposition jou. are right: That if you have more bacteria present in the efiluent from filter A than you have in the effluent from filter B, of course the danger will increase with the number of bacteria in the water. There is no doubt about that. Dr. Woodward. And probably in proportion to the two. Professor Mason. Provided you do not get those numbers too small. STATEMENT OF ALLEN HAZEN. Mr. Moore. Mr. Hazen, with what filtration work have you been connected ? Mr. Hazen. I was connected at first with the Lawrence Experiment Station of the Massachusetts State board of health. The Lawrence city filter was built in 1892, and was put in operation in September, 1893. Also I have been connected as engineer with the construction of filter plants at Far Rockaway and at Red Bank, and with the Albany filter plant and with the Superior Water, Light, and Power Company at Superior, Wis., and a plant for the Pennsylvania State Insane Asylum at Harrisburg. I have also designed other- filters and have made many investigations and tests of filters in service. Mr. Moore. You are the author of a treatise on the purification of water, the latest edition of which was published in 1900? Mr. Hazen. Yes, sir. Mr. Moore. There have been very rapid advances made in filtra- tion, and of late the knowledge on the subject has increased very largely ? Mr. Hazen. Yes, sir. The number of filter plants has increased very largely. The capacity of the filter plants is approximately eight times as great to-day as it was ten years ago. That ratio applies approximately both to sand and mechanical filters in the United States. There have been many very able people who have been studying the problem from different standpoints, and of course much information has accumulated. Mr. Moore. Which is the largest filter plant in the United States, in so far as the amount of water filtered is concerned i 22 WASHINGTON WATEIt SUPPLY. Mr. Hazen. My impression is that the Albany plant is the largest. The nominal capacity of that plant is 15,000,000 gallons per day. It has delivered for short periods up to 20,000,000 gallons. Mr. Moore. Have you examined the Senate documents that were sent to you in regard to filtration? Mr. Hazen. I received a copy of Colonel Miller's report when it was issued, and examined it at that time. I have not examined it since hearing from you in connection with this matter. Mr. Moore. Do you consider that for waters of the New England type the slow sand filter bed is the best? Mr. Hazen. I thought at Albany the sand filters would be best and recommended them. I think at Lawrence the sand filter is unquestion- ably the best. Mr. Moore. The Merrimac River water is a clear water, but is pol- luted at Lawrence by the sewage from Lowell, Nashua, and Manchester? Mr. Hazen. Yes; and other cities. Mr. Moore. Does the sewage from those cities drain into the Mer- rimac River? Mr. Hazen. Directly; yes, sir. Mr. Moore. What were the results that came from the establish- ment of the filter plant at Lawrence, so far as typhoid fever was concerned? Mr. Hazen. It has been very largely reduced. The reduction was very large from the start, and it has gradually increased. The effi- ciency of the filter has increased with age. It is considerably greater than it was the first year. EFPICIENOT OF FILTERS. Mr. Moore. Is that due to the filter, or the method of operation? Mr. Hazen. In part to both, I think. It is generally true that a new sand filter does not give the best results. The processes are largely biological, and it takes a certain time for the organisms to get properly placed on the sand. So the Albany filter, for instance, is doing a great deal better now than it did a year ago. Mr. Moore. Would you say that it is necessary to treat the Cin- cinnati water, and the water generally of the Ohio and Mississippi with the coagulant? ' Mr. Hazen. It was found to be so at Cincinnati and Louisville. We did not find it to be so at Pittsburg. Colonel Miller. That was the Allegheny River. Mr. Hazen. That was the Allegheny, which is the largest part of the Ohio. The water is taken from the river seven or eight miles above Pittsburg. The amount of suspended matter, as it was found at Cincinnati, was about five times as great as we found it at Pitts- ALLEN HAZEN. 23 burg, and was till greater at Louisville. So there is a very gteat difference in the character of the waters. Mr. MooKE. Is there much pollution in the Allegheny Eiver? Mr. Hazen. There is quite a good deal at Johnstown, Oil City, Franklin, and Olean, and a number of other towns. Mr. Moore. Then Pittsburg, as I understand, is putting in the slow sand filter? Mr. Hazbn. It will be put in shortly. The money is appropriated and we are working on the plans now. Mr. Moore. From your experience, can you get as good results ordinarily with the mechanical filter as with the slow sand filter ? Mr. Hazen. That is with reference to bacterial eiEciency ? Mr. Moore. Yes; is there a possibility of it? Mr. Hazen. I think it is largely a question of construction and operation in both cases. Sand filters can be operated to give high bac^ terial efficiencies, and the general practice has established certain stand- ards. I think it would be possible to operate filters to give much higher efficiencies than are secured at Lawrence and Albany, if the increased bacterial efficiency would justify the additional expenditure necessary to secure it. And so also with the mechanical filters iti even greater measure. It is possible to operate them to give very bad results, or it is possible, by taking great care, and particularly by using large amounts of chemicals^ to get very high efficiencies. Mr. Moore. What advantage has the mechanical filter to recom- mend its use in preference to the sand filter? the necessity of using coagulants. Mr. Hazen. The mechanical filter is alwajj's used in connection with a coagulant, and the coagulant is necessary for the treatment of extremely turbid waters. Mr. Moore. Is necessary ? Mr. Hazen. Yes, is necessary; so that when a water is so turbid that it must be coagulated, it is better, or at least cheaper, to filter it with the mechanical filters. Mr. Moore. That opens up two questions — better and cheaper. Mr. HazEN. I think it has usually been decided upon because it is cheaper. Mr. Moore. Then you would have no hesitation in saying that a mechanical filter, properly constructed, will give satisfactory results from the standpoint of bacterial efficiency. Mr. Hazen. A mechanical plant can be operated to give a very high bacterial efficiency. Mr. Moore. Well, have they been so operated? Mr. Hazen. In plants actually built? 24 WASHINGTON WATEK SUPPLY. Mr. Moore. Yes. Mr. Hazen. I do not think so; at least not very often. I have tested some mechanical filter plants and operated them — experimental mechan- ical filter plants — and plants on a considerable scale, and while it is possible to obtain very good efiiciencies, there are a good many things in connection with mechanical filters to cause low degrees in the efficiency. It seems to me that there are greater possibilities of acci- dents of this kind happening with mechanical filters than with sand filters, where the operations take place more slowly, and, it seems to me, can be more perfectly controlled. GRAVITY AND PRESSURE FILTERS. Colonel Miller. In making a comparison between the effects of filtra- tion on typhoid fever, the District Medical Society report which has been read mentions certain cities. Do you know what system is used at Davenport, Iowa? Mr. Hazen. I have the statistics of all those places at my office. They are published in "The Filtration of Public Water Supplies." Colonel Miller. I have it from your authority. How do yoii regard the pressure filter bacteriologically with reference to the gravity filters? Mr. Hazen. The data in regard to what can be accomplished by pressure filters are much less adequate than the data, with reference to the gravity mechanical filters. There are some very recent results that I have seen from pressure filters that seem to correspond very closely with what could have been obtained by gravity filters. Colonel Miller. Are pressure filters generally adopted for waters where bacterial efficiency is the object sought? Mr. Hazen. I should say that they had been used to a considerable extent for that purpose. Colonel Miller. Was that the object in placing pressure filters in Atlanta and Chattanooga? Mr. Hazen. I do not know. Colonel Miller. It is claimed that those filters were installed only to remove turbidity. Is not one objection to pressure filters that they are very irregular in their working with reference to velocity ? Mr. Hazen. That depends upon how they are placed. If water is pumped through the filter to a receiving reservoir, the amount of the (effluent can be made constant. Colonel Miller. Are there not some that merely take pressure from gravity ? Mr. Hazen. I presume there may be. Colonel Miller. In that case the amount of the effluent depends upon the rate of consumption ? Mr. Hazen. Yes, sir. ALLEN HAZEN. 25 Colonel Miller. So that in such a case they would not work regu- larly? Mr. Hazen. The pressure filters that 1 have seen^ where the rate fluctuates with the consumption, have usually been designed with quite large filtering areas, so that the maximum draft is not excessive. Mr. Moore. Please define what you mean by pressure filters ? Mr. Hazen. A pressure filter is a filter in an inclosed receptacle so that the water can be passed through it at greater pressure than the atmospheric pressure would afl^ord or than could be obtained by gravity. Colonel Miller. I merely ask the question because you have remarked that the bacterial efficiency of pressure filters decreases after they are a year old. Mr. Hazen. I do not think we know much about the bacterial effi- ciency of the pressure filter. mechanical filters can do satisfactory work. Mr. Moore. Has a type of mechanical filter been developed that could be used with satisfactory results in filtering 60,000,000 gallons of water a day? Mr. Hazen. Oh, I think so. Mr. Moore. You think there are mechanical filters now in use that are capable of doing the work and doing it satisfactorily ? Mr. Hazen. That is to say, they could do it on a large scale. There is nothing impossible in that. Colonel Miller. And increase the efficiency ? Mr. Hazen. Yes, sir. Dr. Woodward. Do you regard a slight increase of turbidity in water, especially if only occasionally, as in any way diminishing its potability and safety ? Mr. Hazen. Not its wholesomeness, but I regard turbidity as objec- tionable. Dr. Woodward. From an aesthetic standpoint only. Mr. Hazen. Principally from an aesthetic standpoint. Dr. Woodward. From a sanitary standpoint, what are the most reliable guides to the safety of drinking water? Mr. Hazen. Why, the fundamental point — the one that the others all come back to — is the effect of the water on the health of those who use it. The others are indirect, dependent upon our theories of the transmission of disease, though arriving at the same thing. Dr. Woodward. In other words, it depends on the mortality, from water-borne diseases in the first place; or, stated in another form, on the number of bacteria in the water ? Mr. Hazen. That is about it; j^es, sir. Dr. Woodward. With reference to the experimental plants at Pitts- burg, in which I believe Warren and Jewell mechanical filters were 26 WASHINGTON WATER SUPPLY. compared with sand filters, do you remember the relative bacterial efficiency of the two ? Mr. Hazen. The sand filters gave somewhat better bacterial efficiency. Dr. WooDWAKD. They did give better results? Mr. Hazen. Yes, sir. Dr. Woodward. Are you familiar with the most recent report on those filters, as it appears in the Journal of the Association of Engi- neering Societies for November ? Mr. Hazen. Yes; I have seen that article, but I have not read it. Dr. Woodward. You do not know, then, whether the same superi- ority has continued or not? Mr. Hazen. I have the records from Pittsburg up to date in official form. I was directly responsible for the original experiments, but I am not responsible for this publication, and do not know as to its accuracy. BACTERIA IN UNDEEDRAINS. Dr. Woodward. I understand that; but I had the figures and I thought that possibly you were familiar with them. With reference to the origin of bacteria in the effluent of a sand filter, can you give any information for the benefit of the committee with reference to that? Mr. Hazen. That is, do you mean, as to whether they all come from the raw water ? Dr. Woodward. Yes. Mr. Hazen. There are usually a certain number of bacteria, or colonies of bacteria, I think, that come from the underdrains that are washed off. The numbers of bacteria coming from that source vary greatly. In some cases the numbers coming from that source would be almost insignificant and in others considerable; in the summer and in certain types of construction growths have taken place which have increased the numbers very much. Dr. Woodward. In the light of present knowledge do you regard it within the bounds of probability that we should get typhoid bacilli, or colon bacilli — more particularly typhoid bacilli — from colonies in the underdrains ? Mr. Hazen. No, sir. Dr. Woodward. In other words, the bacteria that are derived from the underdrains are harmless ? Mr. Hazen. They are harmless; yes, sir. Dr. Woodward. Then the percentage of bacteria which is found in the effluent of a sand filter is increased by certain additions of harm- less bacteria which grow in the underdrains ? Mr. Hazen. I believe that is generally the case. Dr. Woodward. If, then, it were possible to take a sample of water for analysis from the lower strata of the sand filter, and to exclude ALLEN HAZEN. 27 that from the underdrains, the so-called bacterial effici«ncy of the filter would be higher? Mr. Hazen. Yes, sir; that has been arrived at in another way, par- ticularly by Mr. Clark, now in charge of the Lawrence experiment station. He has found that in some cases the efficiency of the sand filter in removing the colon bacillus from the Merrimac River, which contains them in large numbers, is materially greater than the bacterial efficiency as a whole. Dr. Woodward. That is with a sand filter. We are confining our attention now to the sand filter. The percentage of removal of the colon bacillus is greater than the percentage of the removal of the bacteria as a whole? Mr. Hazen. Yes, sir. Dr. Woodward. Then, when we speak of the bacterial efficiency of a slow sand filter, if we would be strictly accurate, we would have to correct it if some of the bacteria we found there got in it from the underdrains. Mr. Hazen. That, I think, is a proper thing to take into account. Dr. Woodward. And among the additions from the underdrains there is no probability of typhoid or pathogenic organisms ? Mr. Hazen. I think not. Dr. Woodward. Then the efficiency with reference to these organ- isms would be higher than the results show, as you have just stated? Mr. Hazen. I believe that it would be higher. Dr. Woodward. Can you give any idea as to the origin of the bac- teria in the mechanical filters — that is, the origin of the bacteria in the effluent? Mr. Hazen. In mechanical filters, since they have a much higher rate of filtration, if there were corresponding growths in the filters, the numbers of bacteria would be dissipated through very much larger quantities of water and would be proportionally less per unit. In mechanical filters any growths of bacteria in the filter generally I should regard as absolutely unimportant. Colonel Miller. The passage of water is so rapid that they would not have time to develop ? Mr. Hazen. Yes, sir. colon bacillus. Dr. Woodward. That would probably be the case. Now with refer- ence to the colon lacillvs^ which we have to take as an index to the probability of typhoid bacillus, you have spoken of the results obtained iia Lawrence as to their reduction. Are you familiar with the experiments that were made at Cincinnati on this same point with reference to the two types of filters ? Mr. Hazen. I am not familiar with the details just now. 28 WASHINGTON WATER SUPPLY. Dr. WooDWAED. You would expect the tj^phoid-fever death rate of a community to vaiy with the number of bacteria in the water, assum- ing all such bacteria to be derived from the same source ? Mr. Hazen. I think it would, generally. Dr. Woodward. Then, in studying the probable typhoid-fever mortality of a community supplied by slow sand filters, for the pur- pose of comparing it with the typhoid-fever mortality of a community having mechanical filters, we would consider, not the relative bacterial efficiency of the two filters, but the bacterial deficiency — if I may so call it — indicating the percentage left in the water? Mr. Hazen. I think that your standpoint is correct. LOCAL CONDITIONS DETERMINE THE TYPE OF PLANT. Dr. Woodward. You stated, I believe, that there is no type of mechanical filter as yet developed and capable of being installed in Washington that has been installed elsewhere with success ? Mr. Hazen. No, sir; no plant has been installed of that size. Dr. Woodward. Any plant that might be installed would have to be adapted to the local conditions. Mr. Hazen. Certainly. Dr. Woodward. And to that extent would be in the nature of an experiment? Mr. Hazen. Yes, sir. Dr. Woodward. What would be your estimate as to the life of the working parts, the machiner}', etc., of a mechanical filter? Mr. Hazen. I think that would depend entirel}"^ on the design and the materials of which they were constructed. Dr. Woodward. Would that influence the first cost? Mr. Hazen. Necessarily. Dr. Woodward. That would be a matter of engineering theoiy rather than experience ? Mr. Hazen. Yes, sir. Dr. Woodward. One man might design a plant and say it would last twenty years, another thirty years, and another fifteen years, and possibly it might last ten, and in actual experience it might last forty ? Mr. Hazen. I have seen some appliances that would not last even five years. Dr. Woodward. Then when we undertake to calculate the running expenses of a mechanical filter, taking into consideration the duration of the plant, we are dealing, 1 believe, with a very uncertain factor. Mr. Hazen. It is an uncertain factor, and still reasonable estimates can be made, knowing the particular conditions. Dr. Woodward. When you saj^ " reasonable estimates," within what limits of error would j'ou be willing to undertake to make an estunate? Mr. Hazen. That would vary with the different items. ALLEN HAZEN. 29 Dr. WooDWAED. There would be a limit of error, though? Mr. Hazen. Yes; of course. Dr. Woodward. The only way of determining that would be by running your filter until it wore out. Am I correct? Mr. Hazen. Yes; that would be one way. IMPROVEMENTS IN MECHANICAL FILTERS. Mr. Moore. Has there been any marked advance within the past three or four years in the construction of mechanical filters, or are thej' substantially the same as they were three or four j^ears ago ? Mr. Hazen. There have been a good many substantial improve- ments made within three or four years, and quite recently some novel designs have been made. I think there is a chance for very decided improvements in mechanical-filter designs, notwithstanding the facts that a great deal of skill has been put into the present designs, and that they represent many admirable features. Mr. Moore. Would you say that the future is with the mechanical filter, or with the slow sand filter; do you think that for any reason the mechanical filter will supplement the slow sand filter ? Mr. Hazen. I stated, I think, before the Franklin Institute some time ago in this way: That, apparently, for sewage-polluted and rea- sonably clear waters the sand filter was the best, while for muddy waters the mechanical filters would be the best. There is, however, a possibility that a type of filter differing somewhat from both the sand and present mechanical filter — perhaps embodying some parts of each — will be an element in the future. Mr. Moore. Has that probability taken definite form in actual con- struction ? Are you looking forward to the construction of any com- bination of the two ? Mr. Hazen. That has been contemplated. I do not think anything has been constructed as yet. It has not been possible to do that because of the Hyatt patent, covering the use of the continuous appli- cation of coagulant in filtration. The owners of the Hyatt patent have controlled the entire mechanical-filter construction. STATEMENT A§ TO THE HYATT PATENTS. Mr. MooRE. Then there is a certain amount of royalty that enters into the cost of the use of the mechanical filter? Mr. Hazen. That has been so. I think the patent expires next month. Mr. Moore. How wide is that patent? Mr. Hazen. It covers the application of coagulant in a continuous manner in connection with filters. Mr. Moore. What relations have the various filter companies to the Hyatt patents ? S& WASHINGTON WATER SUPPLY. Mr. Hazew. Other gentlemen present to-day, namely the repre- sentatives of the owners of the Hyatt patent, can give you much better information upon that point than I can do. Mr. MooEE. Is there any person in the room whc can tell just exactly what the patent situation is? What is the basis of the patents involving the use of coagulants? Mr. Dennison. Just what do you mean by the basis? Mr. MooKE. You represent the company owning the Hyatt patents, do you not? Mr. Dennison. Yes. As Mr. Hazen has stated, that patent involves the continuous application of a coagulant. Mr. Moore. Are there several filter companies ? Mr. Dennison.. Yes, sir. Mr. MooEE. All use a coagulant? Mr. Dennison. They doi, in some sense; yes. Mr. Moore. What are their relations with your company? Mr. Dennison. Some of them are down on our companies and some are not. I always thought that the principle of that patent repre- sented practically the number of dollars that it cost to maintain it. It has been in litigatijon practically ever since the patent was granted. Mr. Mooee. Then, as I understand it, there are certain companies that are tributary to you, and there are certain companies that are using the coagulant without, as you claim, the right to use it? Mr. Dennison. Yes, sir. There are, however, no companies operat- ing under a royalty fromi us. They haye either the right to use it or they have not. Mr. Mooee. There' ia no payment to you by them? Mr. Dennison^ No^, sir. Mr. Mooee. On what do they base their right to use it? Mr: DENNisom. That they can not get along without it; they must have it. The gj?eat contention was as to the use of the word " contin- uous!" In the fiist place', after the patent was established — that is the mere use of the coagulant continuous process — there were then intro- duced settling tanks^ a'nd it was claimed that that was not an infringe- ment. That was finally decided to be an infringement. Mr. MooEE. So far as the courts hav6 decided these matters they have sustaiiied) the Hyatt. patent?' Mr. Dennison. Yes,vsir... Mr. MooRE. Theue a. 0. duit was completed and water supplied from the Potomac December 5, 1863, and since that date the system has been in successful operation. It was found that the receiving reservoir was frequently rendered very turbid from sudden rises in Little Falls Branch and from surface drainage, thus making the water supply objectionable. To avoid this trouble a by -conduit was built carrying the Potomac water around the receiving reservoir, and it was intended to use the reservoir only when in a suitable condition as to turbidity or otherwise in case of emergency. The constant turbidity and impurity introduced by the watershed draining into the receiving reservoir was finally remedied in 1895 by collecting this surface water and draining it into Little Falls Creek below the reservoir. At the time of the first introduction of the Potomac water, the dam at Great Falls was a riprap dam and extended across the Maryland chan- nel only. At low water in the Potomac constant difficulty was encoun- tered in obtaining a sufficient supply of water. This was partially obviated by extending temporary dams above Conns Island, wnich was on the west side of the Maryland channel, and clearing out this chan- nel by the removal of rock from its bottom. The riprap dam required constant repair after the damage caused by spring freshets and the run out of the ice. In 1886 this dam was replaced bj'' a masonry structure which was extended to the Virginia bank of the Potomac at a level of 148 feet above mean tide water at Washington and was finally, in 1896, raised to the level of 150.5 above the same level. The capacity of the conduit after the raising of the dam was 76,500,000 gallons per diem when the water in the distributing reser- voir was held at a level of 144. This last amount may be considered as the present capacity of the "Washington water system, as a lower height in the reservoir than 144 would so materially decrease the pressure in the mains that a marked lowering of the gravity supply would result. With the present head a large part of the city can not be supplied by gravity. This portion is supplied by direct pumping and by a high- service reservoir at Fort Reno, to which water is pumped by the Dis- trict Commissioners. To recapitulate, the following is a concise description of the present Washington Aqueduct system: The water supply is taken from the Potomac River at Great Falls, about 14 miles above the city. At this point a masonry dam extends across the river from the Maryland to the Virginia shore. Its total length is 2,877 feet, and the width of its crest in the Virginia channel and across Conns Island is 8 feet 3 inches and in the Maryland channel 7 feet 9 inches. In 1895-96 the crest of the dam was raised from a reference of 148 feet above mean tide at the Washington Navy- Yard to 150.5 feet above the same datum plane. The top of the mouth of the feeder of the conduit at Great Falls is at a reference of 149 feet and the bottom at a reference of 139.6 feet. The water passes from the feeder through the gatehouse and into the conduit, which at this point has a reference of 152 feet at the interior surface of the crown of the arch. The slope of the conduit is uniform between the gatehouse at Great Falls and the distributing resei-voir and is 9 inches in 5,000 feet. FILTEKING WATEE SUPPLY OF WASHINGTON, D. C. 155 The conduit is circular in cross section, and for the greater part of its entire length is 9 feet in diameter and composed either of rubble masonry plastered or of 3 rings of brick, but where the soil in which it was built was considered particularly good the inner ring of brick was omitted and the diameter is 9 feet 9 inches. Where the conduit passes as an unlined tunnel through rock the excavation was sufficient to contain an inscribed circle 11 feet in diameter. The lengths of the conduit and its connections are as follows: Length of feeder at Great Falls, 256 feet. Area of cross section at mouth, 157.45 square feet. Length of conduit between gatehouse at Great Falls and north con- nection of Dalecarlia Reservoir, 47,896.6 feet; least diameter, 9 feet. Length of by-conduit around Dalecarlia Reservoir, 2,730.5 feet; diameter for 625 feet, 8 feet; for rest of distance, 9 feet. Length of conduit between south connection of the Dalecarlia Reser- Yoir and north connection of the distributing reservoir, 10,149.87 feet; diameter of conduit, 9 feet. Length of by-conduit around the distributing reservoir, 2,274.35 feet; diameter 7 feet. At the distributing reservoir the water passes into four cast-iron mains, 48 inches, 36 inches, 30 inches, and 12 inches in diameter, respectively. The Dalecarlia Reservoir has a storage capacity of about 150,000,000 gallons; is practically without paved slope wall, is perfectly protected against pollution from the drainage of the surrounding country, and is provided with a spillway, the reference of the bottom of which is 146.5 feet. The reference of the interior surface of the crown of the arch of the conduit at the north connection of this reservoir is 143.77 feet and at the south connection 143. 39 feet. The distance between these points, measured along the line of flow of the water aciross the reservoir, is about 3,550 feet. The distributing reservoir has a storage capacity of about 150,850,000 gallons and is divided by a puddled and paved wall, through which is a passageway which can be closed with stop planks, into two sections containing 97,600,Q00 and 53,250,000 gallons, respectively. The interior surface of the crown of the arch of the conduit at the north connection of this reservoir has a reference of 141.87 feet. In addition to the three reservoirs already mentioned, which form a part of the aqueduct system, there is another reservoir, built and con- trolled by the Commissioners of the District of Columbia, called the Fort Reno Reservoir, with a capacity of about 4,500,000 gallons, the ref- erence of its water surface, when the reservoir is full, being about 420 feet. This reservoir, like the high-service reservoir in Georgetown, is sup- plied with water taken from the 36-inch main by the U street pumping station. The Dalecarlia and distributing reservoirs supply this station and that part of the District which lies below 100 feet above datum. The areas lying between the levels of 100 and 210 feet above datum are sup- plied by pumping from the U street station directly into the distribu- ting mains. The areas having a greater elevation than 210 feet above datum are supplied from the Fort Reno Reservoir. It will be observed, therefore, that the total present storage capacity 15(3 FILTERING WATER SUPPLY OF WASHINGTON, D. 0. of all reservoirs is a little over 305,000,000 gallons, or about six days' normal supply. There is now under construction, for increasing the water supply of Washington, a tunnel from the present distributing reservoir to a new reservoir situated near the Howard University. The new reservoir has a capacity of 300,000,000 gallons, thus raising the capacity of storage to 605,000,000 gallons. The new reservoir, being situated about 4 miles east of the present distributing reservoir, will occupy a more central distribution point, and thus somewhat reduce the loss of head now obtaining at Capitol Hill and east thereof. The level of water in this reservoir will be 144, and it is estimated will add about 15 feet additional height to the water delivered at Capitol Hill. Until the average daily consumption of water becomes considerably greater than at present, the reference of the surface of the water at the lowest stage of the Potomac will be about 151 feet at the mouth of the feeder at Great Falls ; about 146.75 feet at the Dalecarlia Eeser- voir, and 146 feet at the distributing reservoir. The following table gives the daily consumption of water by the District of Columbia as furaished by the Washington Aqueduct for the last twenty -six years : Date. Daily con- sumption. Popula- tion. Amount per capita per diem. 1874 , . . Gallons. 17,554,848 21,000,000 24, 177, 797 23,252,932 24,885,945 25,947,642 '.'■'.,740,138 26,525,991 29,727,864 24,314,7K 24, 827, 113 25,219,194 25,542,476 26,878,424 29,115,774 27,708,779 35,541,845 38,594,743 41,161,780 46,727,108 49,162,357 47,182,681 44,113,574 45, 267, 047 47,288,733 50,079,865 1130,182 1138,091 1146,000 1163,909 1161,818 1169,727 2177,638 1182,893 1187,968 1193,133 1198,198 3 203,459 1208,358 1213,357 1218,157 1225,309 2 232,460 1248,539 3 264,618 1267,569 3 270,619 1272,667 1274,815 » 276, 963 1 279, 432 1281,901 GaUons. 134 1875 152 1876 165 1877 151 1878 154 1879 . 153 1880 145 1881 145 1882 158 18S3 126 INS } 125 1885 124 1886 123 1887 - . 126 1888 133 1889 ■ 123 1890 153 1891 . . . 155 1892 156 1893 171 1894 182 1895 173 1896 .. .. 161 1897 163 1898 169 1899 178 1 Estimated. 2 United States census. 3 Police census. THE POTOMAC EIVEK WATER. The Potomac River, formed by the junction of its north and south branches, rises in the Allegheny Mountains, the north branch in the western part of Maryland, near the head waters of the Monongahela River, and the south branch in the State of West Virginia. These two branches, draining narrow and precipitous valleys in the mountainous regions, unite at Cumberland, Md. , to form the main river, thence in FILTErJNG WATEK SUPPLY OF WASHINGTON, D. 0. 157 a southeasterly direction, normal to its previous course and to the direction of the mountain range, the river flows to the sea through one of the great estuaries of the Atlantic — Chesapeake Bay. Owing to the narrow and steep-sided valleys in which it has its source, and to the fact that there are no lakes throughout its basin, the Poto- mac is subject to sudden and heavy freshets. The principal tributary is the Shenandoah River, joining from the south at Harpers Ferry. Many small streams, generally from the Maryland side, are also tributary, the principal one being the Monoc- acy River, upon which the city of Frederick is situated. These trib- utaries flow through a rolling and cultivated country quite in contrast to that above Harpers Ferry. The drainage area of the Potomac River above the Great Falls, whence is taken the "Washington water supply, is 11,043 square miles. The minimum flow of the river at the Great Falls is 1,065 cubic feet per second, or 700,000,000 gallons per diem, the average flow 6,500,- 000,000 gallons per diem, and the estimated flow during the flood of 1889 305,650,000,000 gallons. The estimated population for 1900 of the watershed is 491,813, or about 44.5 per square mile. The towns in the drainage basin of the Potomac are not sewered, so that very little direct sewage is emptied into the stream, the main source of contamination being from surface drainage, whence ina,j be expected pollution due to decaying vegetable and animal matter, the surface wash from fertilized tields, the excreta from man and animals, the waste from factories, and whatever salts may be held in solution derived from the natural geological formation of the basin. From the figures given above it will be seen that the Potomac River affords an abundant supply for the District of Columbia. The present consumption — 60,000,000 gallons per diem — is only about 7 per cent of the minimum dischai-ge of 700,000,000. The present population of the District of Columbia is estimated as 280,000, and will, according to estimate (see report upon the sewerage of the District of Columbia, House Ex. Doc. No. 445, Fifty-first Congress, first session), probably reach 500,000 in 1930. At the present rate of consumption this popu- lation would require a per diem supply of about 100,000,000 gallons, about 15 per cent of the minimum discharge. Pure water does not exist in nature. The rain that falls from the clouds becomes contaminated before reaching the earth. It absorbs ammonia, carbonic acid, sulphuretted hydrogen, and other gases from the atmosphere, especially in the vicinity of cities and towns. It takes up and holds iti suspension floating particles of the minute dust always present in the atmosphere — carbon in the form of smoke or floating soot. After falling to earth and before it again appears at the surface as springs it has, although having undergone a natural filtration, dis- solved from the soil and strata through which it has passed various soluble salts, which are sometimes so noticeable as to give a medicinal quality to the water. From the spring or fountain head the water, again starting on its journey to the ocean whence it came in vapor, is joined by other springs and surface drainage, becoming more or less polluted as the character of the districts through which it passes varies, till at last, receiving the enormous sewage discharge of large cities, it becomes dangerous as a domestic supply. The spread of many zymotic diseases is attributed by modern 158 FILTERING "WATER SUPPLY OF WASHINGTON, D. 0. authorities to polluted water. It is almost universally admitted that typhoid fever, Asiatic cholera, anthrax, and even tetanus are water- borne diseases, whose germs have been carried in the water contami- nated by surface drainage or sewage. The science of bacteriology has so far advanced that careful exami- nation of suspected water can differentiate these disease bacilli, and no source of supply should, under present conditions of civilization, be adopted for domestic purposes until this examination be made. The bacteriological examination of a source of supply, if a running stream, subject to the various changing conditions of the seasons, should be continuous for at least a j^ear to give perfectly satisfactory results, as the stage of stream, the temperature, and seasons of the year all affect its condition. In addition to the bacteriological examination, a water supply should also be submitted to a chemical analysis. By such analysis may be determined the probable source of pollution, if any exists. The chemical analysis of potable water consists in determining the parts per million of ammonia, nitrogen as nitrites and nitrates, chlorine, alkalinity, required oxygen, total solids, turbidity, color, odor, and taste. Ammmiia. — The presence of ammonia in abnormal or suspicious quantity indicates pollution by animal matter, decayed or decaying. Nitrogen as nitrites and nitrates. — The presence of nitrites is always to be looked upon with suspicion as indicating contamination. Nitrates indicate the former presence of nitrites more fully oxidized. Glilorine. — ^The presence of chlorine above the normal is very sus- picious. Chlorine is nearly always present in the water used for domestic purposes, due to common salt, and an excess is a positive indication of sewage contamination. Alkalwiity. — The determination of alkalinity is important as an indi- cation of hardness. Very hard water is expensive as wasting soap, and "scales" in cooking utensils and steam boilers, and frequently renders the water disagreeable to the taste. Required oxygen. — This determination gives a means of judging the amount of organic carbon present in water. Turhidity. — This is determined chemically by ascertaining the total amount of solids in suspension. Color. — This is deteimined ocularly by comparison with standards. Odor.— This is obtained by smell. Taste. — This is determined by physical test. No absolute standards can be established by which a water may be condemned as unfit for domestic purposes, as the source of supply must always enter into consideration, and an excess in any item of determination may be traced to harmless causes. The following are some of the standards quoted from Prof. William P. Mason's treatise on "Water supply:" Ammonia, — Professor Mallet gives from an analysis of 15 drink- ing waters believed to be wholesome, for albuminoid ammonia, 0.125 parts per million. Dr. Leeds gives as the highest limits as a standard for American waters, free ammonia 0.01 to 0.12 per million. Nitrites. — Mallet gives 0.0135 per million. Leeds gives (American rivers) 0.003 per million. FILTEEING WATER SUPPLY OP WASHINGTON, D. 0. 159 Nitrates. — Mallet gives as an average of 13 samples 0.42 per million. Extremes, to 1.04. CMorvne. — Leeds gives 3 to 10 per million. Ordinary sewage con- tains 110 to 160 per million. Human urine contains 6,872 per million. Hardness. — Leeds gives, in parts per million, 50 for soft and 150 for hard waters. Total solids. — Dr. Smart, National Board of Health, 1880, gives as a safe limit 300 parts per million; to be condemned, 1,000 parts per million. Leeds gives, as a standard for American rivers, 150 to 200 parts per million. Required oxygen. — Leeds gives 5 to 7 parts per million. These standards are shown below in tabular form: Total solids 150 -300 Freeammonia 0.01 - 0.12 Albumin, ammonia 10 - .28 Nitrites 0135- .003 Nitrates - 1.04 Chlorine 3 - 10 Required oxygen 5 - 7 EESULTS OF CHEMICAL ANALYSIS OF THE WASHINGTON WATEE SUPPLY. The chemical analysis of the water as taken from the faucet has been made weekly at the health office of the District Commissioners for several years. Col. Charles Smart, Assistant Surgeon-General, United States Army, kindly furnished analyses made by Dr. William M. Mew, Army Med- ical Museum. Analyses were also made during the experiments by Mr. Robert Spurr Weston, who had charge of this subject, as well as the bacterio- logical and physical examinations. The results of the analyses by the District health office and Dr. Wil- liam M. Mew are given below. The details of Mr. Weston's analyses can be examined by reference to his valuable report, which is submitted as an appendix. 160 FILTERING WATEE SUPPLY OF WASHINGTON, D. 0. StalemerU of ihe results of various analyses of Potomac water as delivered from the faucet in ihe laboratory of the health office, Washington, D. C, since July SS, 1897. [Parts per million.] No. Date. Total solids. Lose on ignition. Free ammonia. Albu- minoid Nitrites. Nitrates. Chlorine. Oxygen con- sumed. 1897. 1 July 22 145 48 0.002 0.175 Trace. 0.45 3.5 2.52 2 July 29 137 61 .006 .220 0.002 .47 3.6 2.74 3 Aug. 5 128 45 .000 .136 .000 .47 3.6 2.56 4 Aug. 12 142 60 Trace. .140 .000 .60 3.5 2.60 5 Aug. 19 131 39 .004 .128 .000 .50 3.5 2.40 6 Aug. 26 125 64 .000 .130 .000 .50 3.5 2,36 7 Sept. 2 140 52 .000 .130 .000 .52 3.5 2.30 8 Sept. 9 136 48 .000 .130 .000 .50 3.5 2.32 9 Sept. 16 125 61 .000 .110 .000 .54 3.5 2.16 10 Sept. 23 117 50 .000 .096 .000 .51 3.5 1.96 U Sept. 30 130 64 .000 .105 .000 .52 3.6 2.04 12 Oct. 7 136 60 Trace. .116 .000 .62 3.5 2.11 13 Oct. 14 145 60 .000 .110 .000 .35 5.0 2.00 14 Oct. 21 140 50 .000 .105 .000 .60 4 1.96 15 Oct. 28 142 51 .000 .115 .000 .55 4.0 2.04 16 Nov. 4 136 48 .000 .100 .000 .60 4.0 1.95 17 Nov. 11 139 66 .000 .120 .000 .60 4.0 2.00 18 Nov. 18 135 64 .000 .146 .000 .70 4.5 2.12 19 Nov. 23 140 56 .000 .140 .000 .70 4 5 2.10 20 Dee. 1 168 63 .0066 .197 .000 .70 4 5 3.08 21 Dec. 9 140 47 .004 .100 .000 .60 4.0 1.90 22 Dec. 16 131 42 .000 .098 .000 .60 4.0 1.84 23 Dec. 23 119 41 Trace. .096 .000 .60 4 1.72 24 Dec. 30 1898. 116 40 .001 .098 .000 .65 4.0 2.11 25 Jan. 6 121 38 .000 .098 .000 .65 4.0 1.84 26 Jan. 13 105 38 .000 .074 .000 .60 4 5 1.76 27 Jan. 20 116 42 Trace. .089 .000 .60 4 1.84 28 Jan. 27 140 44 .000 .110 .000 .60 4.0 2.06 29 Feb. 3 103 37 .001 .064 .000 .65 4 1.66 30 Feb. 10 100 36 .000 .084 .000 .60 4 1.72 31 Feb. 17 94 32 .000 .090 .000 .60 4 1.76 32 Feb. 24 100 41 .000 .074 .000 .75 3.5 1.56 33 Mar. 3 96 35 .000 .068 .000 .80 3.5 1.52 34 Mar. 10 95 38 .000 .060 .000 .85 3.5 1.42 35 Mar. 17 92 37 .000 .045 .000 .85 3.5 1.32 36 Mar. 24 96 36 .000 .060 .000 .80 3.5 1.36 37 Mar. 31 101 40 .000 .056 .000 .80 3.5 1.62 38 Apr. 7 108 38 .000 .089 .000 .76 3.6 2.12 39 Apr. 14 110 46 .000 .086 .000 .70 4.0 2.00 40 Apr. 21 98 39 .000 .097 .000 .70 3.5 2.16 41 Apr. 28 May 5 92 41 .000 .079 .000 .70 3.6 1.91 42 95 39 .000 .072 .000 .70 3.6 1.79 43 May 12 97 40 .000 .084 .000 .70 3.5 1.60 44 May 19 106 42 .000 .100 .000 .70 3.5 1.84 45 May 26 112 45 .000 .130 .000 .60 3.5 1.98 46 June 2 116 40 .000 .140 .000 .60 3.5 2.00 47 June 9 120 42 .000 .145 .000 .60 3.0 2.11 48 June 16 125 42 .000 .128 .000 .66 3.5 2.00 49 June 23 128 46 .000 .116 .000 .50 3.0 1.90 50 June 30 122 41 .000 .120 .000 .60 3.0 1.96 61 July 7 125 44 .000 .135 .000 .50 3.0 1.90 52 July 14 1899. 132 48 .000 .110 .000 .60 3.0 1.80 53 Aug. 28 128 61 .000 .130 .000 .80 4.0 2.60 54 Sept. 5 130 62 .000 .150 .000 .80 4.0 3.60 65 Sept. 21 131 46 .000 .165 .000 .70 4.0 2.36 56 Sept. 28 137 44 .000 .134 .000 .70 4 3.00 57 Oct. 4 144 43 .000 .110 .000 .70 4.0 3.20 68 Oct. 18 151 58 .000 .060 .000 .70 4 8.60 69 Oct. 24 157 45 .000 .125 .000 .70 4 4.00 60 Nov. 1 144 44 .000 .150 .000 .70 4 3.40 61 Nov. 9 166 42 .000 .140 .000 .70 4.0 3.60 62 Nov. 16 148 56 .000 .110 .000 .70 4.0 4 00 63 Nov. 22 125 44 .000 .105 .000 .70 4.0 3.60 64 Dec. 5 144 46 .000 .110 .000 .70 4.0 4.00 65 Dec. 6 137 48 .000 .065 .000 .70 4 6.60 66 Dec. 14 138 51 .000 .070 .000 .70 4 4.00 67 Dec. 28 1900. 146 48 .000 .097 lOOO .70 4 420 68 Jan. 4 154 52 .005 .120 .000 .72 4.0 6.00 69 Jan. 11 161 61 .004 .156 .000 .72 4.0 4.60 70 Jan. 18 132 35 .010 .110 .000 .72 4.0 6.60 71 Jan. 26 129 37 .010 .135 .000 .72 4.0 6.40 72 Jan. 31 145 40 .006 .140 .000 .70 4 4.50 AvRraffe . 126.7 45.6 .0008 .111 .637 3.78 2.55 riLTEKING WATEK SUPPLY OF "WASHINGTON, D. 0. 161 Batemeni of results of analyses of Potomac water from April S5 to October 25, 1899, inclusive. [The results are given In parts per 100,000 of the water.] Date. Chlorine, Nitrites. Nitrogen in ni- trates. Free am- monia. Albumi- noid am- monia. Oxygen used. Total solids. Lesson ignition. April 25 , Mays , May 11 May 17 Junel June 14 June 23 June 28 Julye July 19 August 2 August 16 August 30 October4 October 18 October 25 Averages 0.4 .4 .4 .4 .4 .4 .4 .4 .4 .4 .4 .4 .4 .4 .4 None. None. None. None. None. Trace. None. Trace. None. None. Trace. None. None. None. Trace. None. 0.10 .16 .16 Trace. Trace. 0.15 .10 .05 .10 .07 .10 .10 .11 .15 .12 .11 Trace. Trace. Trace. Trace. Trace. Trace. Trace. Trace. Trace. Trace. Trace. Trace. Trace. Trace. Trace. Trace. 0.008 .008 .006 .008 .006 .012 .008 .10 .006 .006 .012 .014 .015 .012 .007 .012 0.144 .150 .152 .232 *.250 *.264 .150 .192 .188 .164 .180 .220 .266 .262 .268 .284 9.4 9.7 13.0 14.0 11.0 16.0 9.7 14.5 12.0 11.2 12.1 12.5 12.6 13.9 14.6 16.1 4.5 4.1 *2.5 *3.0 *2.0 *3.5 4.0 5.5 4.0 4.2 4.0 4.1 5.4 4.7 6.4 4.8 Trace. .11 Trace. .015 .210 12.5 4.1 Note. — The asterisks point to experiments made to ascertain the loss on ignition after total removal of suspended matter by means of the centrifugal machine. Also, in two cases, the effect of this on the estimation of "oxygen used." That of June 1 had required, before the removal of suspended mat- ter, 0.264, and that of June 14 0.280 parts. In the nitrite column, where traces are reported, the reaction, never more than faint, became apparent in fifteen minutes. Experiments were made to ascertain the amount of suspended matter in turbid water on May 17 and on June 14. It amounted to 5 parts and 6 parts, respectively. All the "oxygen used" estima- tions given above were made upon water free from suspended matter. The albuminoid ammonia estunations on July 6 and 19, being unusually low, were repeated and found correct. The nitrogen in nitrates was estimated by the picric-acid method. W. M. Mew, Chemist, Suryeon^GeneraZ*s Ctfflee. December 15, 1899. The following are the results tabulated for comparison, by averages: Total solids. Free am- monia. Albumin, ammonia. Nitrites. Nitrates. Chlorine. Required oxygen. Health office. District of 126.7 126.0 139.0 150-300 0.0008 Trace. .013 .01-. 12 0.111 .150- .105 .10-. 28 Trace. Trace. 0.002 .W!aW