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 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/cu31924004978064 
 
Cornell University Library 
 TD 745.S39 
 
 Report on sewage disposal at the Nationa 
 
 3 1924 004 978 064 
 
REPORT 
 
 SEWAGE DISPOSAL 
 
 AT THB 
 
 NATIONAL SOLDIERS' HOME 
 
 NEAR SANTA MONICA, CAL. 
 
 J1'^ 
 
 JAMES DV SCHUYLER 
 
 M. Am. Soc. C. E. 
 
 Consulting Hydraulic Engineer 
 
 NOTES ON THE SEPTIC 
 
 PURIFICATION OF SEWAGE 
 
 SAMUEL S TOR ROW, A. B. 
 
 Assoc. M. Am. Soc. C. E. 
 
 I<OS ANGELES : 
 Press of b. R. Baumgarbt & Co. 
 
 1900 
 
CONTENTS. 
 
 I. Preface. ' 
 
 II. Sewage. 
 
 III. Putrefaction. 
 
 IV. Chemical Purification, Precipitation Treat- 
 
 ment. 
 y. Chemical Purification, Antiseptic Treatment. 
 
 A'l. Bacterial Treatment — 
 
 ( a ) Aerobic. 
 
 (b) Anaerobic. 
 
 ( c ) Combined. 
 
 yil. The Principle of the Control of Putrefactiori 
 
 by Control of Bacterial Contents. 
 MIL Bacterial Beds, Action, Control and Capacity. 
 
 IX. Septic Tanks, Action and Capacity. 
 
 X. The Measure of the Purifying Action. 
 Measure of Action by Bacteria. 
 
 By Numbers. 
 By Varieties. 
 Measure of Action by Nitrites and Nitrates. 
 
INTRODL'CTORY. 
 
 The use of sewage on the fields and gardens at the 
 Soldiers' Home near Santa Monica prior to 1899 had 
 been accomplished with little attention to sanitation 
 and without any attempt to give it preliminary treat- 
 ment to render it inoffensive, or innocuous, and 
 unpleasant odors were frequently wafted on the breezes 
 of midsummer to several farm dwellings situated in 
 the lee of the irrigated fields. These odors became a 
 serious nuisance and were complained of by the neigh- 
 bors, one of whom threatened suit to enjoin the use 
 of the sewage in that manner. This threat served to 
 call the attention of the management to the subject, 
 and negotiations were begun with the City of Santa 
 Monica for the purpose of securing a means of disposal 
 of the sewage into the ocean through the Santa Monica 
 Sewerage System. 
 
 Prior to closing a contract for this method of disposal 
 the author was requested to investigate the subject 
 and report on all available methods of disposal of the 
 sewage and the abatement of the nuisance complained 
 of. The following report was prepared as the result 
 of this investigation. This report has been subrhitted 
 to the General Board of Managers of the Homes for 
 Disabled Volunteer Soldiers, at A¥ashington, and has 
 received their approval, and the appropriation for 
 constructing the septic tank recommended has been 
 
made by Congress, and at the present writing is avail- 
 able for the work. The writer has been instructed 
 to prepare plans and carry them into effect, and it is 
 expected that the tank will be in operation before 
 November ist. 
 
 Its operation will be looked upon with no little 
 interest by the Engineering profession, as, so far as 
 known, it will be the first application of the principle 
 of septic treatment of sewage on the Pacific Coast. 
 
 The publication of the report has been frequently 
 urged by the fi'iends of the writer familiar with it, 
 but it did not appear to him as complete an expose 
 of the biological processes involved as was desirable, 
 and at his suggestion Samuel Storrow undertook the 
 subjoined treatise on the subject, which, together with 
 the report, is printed for private circulation, in the 
 hope that it may prove useful to Engineers and laymen 
 seeking a general summary of fin de siccle practice in 
 sewage disposal. 
 
 JAS. D. SCHUYLER. 
 Los Angeles, Cae., August, 1900. 
 
SOME NOTES 
 
 ON THi; 
 
 SEPTIC PURIFICATION OF SEWAGE. 
 
 Samuel Storrow, 
 Assoc. M. Am. Soc. C. E. 
 
 Los Angeles, Cal. 
 1900. 
 
SOME NOTES ON THE SEPTIC PURIFICA- 
 TION OF SEWAGE. 
 
 The design of James D. Schuyler, Consulting Civil 
 Engineer, of a system for the disposal of the sewage 
 originating in the Soldiers' Home, near Santa Monica, 
 includes the construction of a septic tank, so arranged 
 as to be always filled with sewage. This idea is new 
 in locaj practice and the interest shown in the method 
 as evidenced by frequent personal inquiries, has led 
 to this attempt to present more fully the biological 
 side of the design and the beneficial results brought 
 about by this septic tank. 
 
 These inquiries have been of two classes, from those 
 whose interest is purely scientific, and from those who 
 wish to know the applicability of the process to special 
 cases. After examining thoroughly into the nature 
 of the materials and processes employed, we will be 
 able to outline the limits of the applicability of the 
 biological methods of purification. The study and 
 comparison of some of the local problems will then 
 serve to exemplify the investigation. 
 
 II. SEWAGE. 
 
 Sewage is water seriously contaminated by the 
 animal and vegetable wastes from the processes of 
 human economy. The contained animal substances 
 
are largely composed of fibrin, gelatin, chondrin, albu- 
 men, etc., all of which are unstable, complex com- 
 pounds containing carbon, nitrogen, hydrogen and 
 sulphur. These nitrogenous compounds speedily 
 undergo decay by putrefaction, giving off foul odors 
 whenever the supply of oxvgen is deficient. The vege- 
 table substances in sewage are mainly starch, cellulose, 
 gummy matters and tannin. These decompose slowly, 
 giving off few disagreeable odors. 
 
 The following table compiled from various sources* 
 gives a fair idea of the constituents of ordinary 
 sewage. 
 
 * "Purification of Sewage and Water," W. J. Dibdin. 
 
 "Sewage Disposal in the United States.'' Rafter & 
 Baker. 
 
 "Report to London County Council." Clowes & 
 Houston. 
 
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 < 
 
 Oh 
 
 < 
 
 
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 Q 
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 m 
 
 u 
 
 ■S3}Ej;i\J 
 
 ■u3Soj;ifvj 
 
 o 
 H 
 
 'l^ioi 
 
 ■oiueSjq 
 
 ■[Bjauipj 
 
 T1 
 
 
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 ^ 
 
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 •3IUeSjO 
 
 IEJ3U!J\[ 
 
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 01 
 
The mineral matter contained in the sewage is 
 generally harmless. The whole problem consists in 
 destroying the small amount of organic matter. The 
 chemical composition of this organic matter, as a 
 whole, is outlined above, and the chemical composition 
 of the various animal and vegetable substances is 
 shown in — 
 
 TABLE II.* 
 
 Chemical Composition of Organic Contents of 
 Sewage. . . Per Cent. 
 
 Substances. 
 
 Gelatin . 
 Chondrin 
 Albumin 
 Cellulose 
 Starch . . 
 Fat 
 
 
 a 
 
 
 a 
 
 <u 
 
 
 
 bo 
 
 c 
 
 bo 
 
 , 
 
 <u 
 
 O 
 
 1-1 
 
 be 
 
 i-i 
 
 •0 
 
 >^ 
 
 .ti 
 
 >^ 
 
 X 
 
 ^ 
 
 ffi 
 
 
 
 18.3 
 
 6.6 
 
 25- 
 
 14.4 
 
 7.1 
 
 29.4 
 
 16. 
 
 7-1 
 
 22. 
 
 
 6.2 
 
 49.4 
 
 
 6.2 
 
 49-4 
 
 
 12.7 
 
 II-3 
 
 c 
 o 
 
 J3 
 
 U 
 
 SO. 
 
 49- 
 
 S3- 
 
 44-4 
 
 44-4 
 
 76.4 
 
 III. PUTREFACTION. 
 
 The usual putrefactive processes of Nature combine 
 the organic substances present with a certain amount 
 of oxygen. The nitrogenous matters are reconstructed 
 with the giving off of ammonia or possibly of free 
 nitrogen, oxides of nitrogen are formed, nitrous and 
 nitric acids, carbonic acid, sulphuretted hydrog-en, 
 marsh gas, water, etc. Such are the chemical changes 
 through which the organic contents of the sewage must 
 
 * Dibdin, Cit. 
 
13 
 pass from its condition of dangerous and offensivel- 
 putrifying nitrogenous organic compounds to inert and 
 harmle'^s nitrites and nitrates. This putrefactive pro- 
 cess is materially assisted, if not wholly broup'h-t about, 
 bv the life action of certain small organisms called 
 bacteria or microbes. These small organisms, by the 
 process of their economy, utterly destroy all the 
 organic compounds with which they come in contact, 
 even to the extent of making a full meal of those of 
 their late friends who may succumb to the infinites- 
 simal struggle for the survival of the fittest. A full 
 recognition of the essential part in all putrefaction 
 played by these bacteria is a primary requisite for the 
 successful dealing with the matter in hand. 
 
 The purification of sewage is the oxidation of the 
 organic contents, chemically shown by the nitrogen 
 appearing wholly as nitrates, biologically shown by 
 the growth and change of the bacterial life through a 
 cycle ending in the complete extinction of such life. 
 Since the bacterial life is the cause of the chemical 
 change and is itself dependent upon certain chemical 
 and physical conditions, we have in our hands a simple 
 control of the whole putrifactive process. 
 
 IV. CHEMICAL CONTROL OF PUTREFAC- 
 TION. 
 
 Chemical purification of sewage effects one thing 
 only, and that is the separation of the undissolved sus- 
 . pended matters from the liquid matters.* Certain 
 experiments in the laboratory have gone beyond this 
 point, but, whatever may be claimed to the contrary, 
 there is no workable process by chemical precipitation 
 yet invented which will yield a "tank effluent" even 
 
 * "Sewage Treatment and Sewage Disposal." W. S. 
 Crump, Eng. and Bldg. Record XXVII, Eng. News 
 XXIX. 
 
14 
 approximately purified from its objectionable contami- 
 nations. The great claim for the value of many chem- 
 ical processes of purification is the consequent savmg 
 of the manurial values in the sewage. Sewage does 
 contain ingredients of considerable manurial value, 
 but they are as the needle in the haystack. It has 
 hitherto always cost more to prepare the manure for 
 market than it will sell for when prepared. 
 
 When the local conditions in any case are such that 
 the manurial contents of the sewage can be made to 
 yield, or assist in yielding,* some return for its treat- 
 ment, this should by all means be done. But it must 
 be borne in mind that the primary object is to dispose 
 of the sewage thoroughlv and without nuisance. 
 
 There are many cases where the rapid precipitation 
 of the solid suspended matter is advisable, and in a 
 few of these cases chemical precipitation may be indi- 
 cated, but even here bacterial processes are rapidly 
 proving a superior adaptability. In a few cases chem- 
 ical treatment is indicated on account of its encour- 
 aging or retarding influence on the bacterial life pro- 
 cesses. 
 
 V. CHEMICAL ANTISEPTIC TREATMENT. 
 
 One must carefullv distinguish between chemical 
 processes having for an object the oxidation of the 
 organic contents of the sewage and chemical processes 
 looking to the prevention of putrefaction by antiseptic 
 means. The addition of chemicals to assist the bac- 
 terial life is generally along the line of attempting to 
 add to the amount of oxygen in the water, and thus 
 is merely a part of a bacterial system of purification. 
 The antiseptic treatment is directly opposed to the main 
 object sought to be accomplished. We have already 
 seen that the oxidation of the contained organic mat- 
 
 * See papers in Jour. Roy. Ag. Soc. of England. 
 
15 
 ter is the ultimate end sought, so that any method of 
 preservation or prevention of decay by antiseptics must 
 be worse than useless, as it destrovs that bacterial life 
 upon the active life processes of which we are depend- 
 ent. 
 
 Deodorization, as distinct from disinfection, is some- 
 times properly emploved when it is desired to obtain 
 temporary relief from offensive odors. The result of 
 all experience up to date seems to show that bacterial 
 processes alone can be depended upon to solve all our 
 vexed cjuestions of sewage disposal without nuisance, 
 and that chemistry will merely serve as a check of the 
 amount and rate of the work being done. 
 
 'fe 
 
 VI. BACTERIAL TREATMENT OF SEWAGE. 
 
 It is known that the process known as nitrification 
 of the complex nitrogenous organic compounds exist- 
 ing in sewage is brought about by two definite classes 
 of organisms,* each producing a distinct stage in the 
 process, and each being so distinct in its life history as 
 to admit of substantially separating these two stages 
 of the putrefactive process. The life processes of one 
 of these classes of organisms liquefy the suspended 
 organic imprities, and the life of the other yields 
 nitrates. By a judicious control over the conditions 
 affecting the growth and multiplication of one or the 
 other of these organisms we can readily stimulate or 
 retard either part of the process. 
 
 The aerobic organisms, when oxygen is freely pres- 
 ent, destroy the organic matters contained in sewage 
 without the accompaniment of offensive products. 
 The anaerobic organisms multiply and act where there 
 is no air and yield inoffensive products. 
 
 These two classes of organisms are always present 
 
 * Investigations Rothamsted Station, Robt. Waring- 
 ton, Bulletin No. 8. 
 
i6 
 in crude sewage. They are bacilli and so minute ni 
 size that it is difficult to describe them in popular terms. 
 In "Applied Bacteriology," by Permain & Moore, we 
 are told that if we could view an average man under 
 a degree of magnification equal to the higher powers 
 used in the microscopic study of bacteria, he would 
 appear to be about four miles high. So rapid is the 
 multiplication of bacteria under favorable conditions 
 that in one week the number of the descendants from 
 one bacterium would be expressed by a number of 
 fifty-one digits. Forty thousand million bacteria weigh 
 one grain, and yet in three days the combined weight 
 of the descendants of a single microbe would weigh 
 7,366 tons. Five hundred million microbes have a 
 bulk equal to the head of a pin, and yet in five days the 
 descendants of one bacillus will aggregate the volume 
 of the entire ocean. It is needless to say that these 
 figures are the theoretical increase without death or 
 disaster. The lack of food and the presence of un- 
 favorable physical conditions prevent unmanageable 
 multiplications of this description. Enough has been 
 said to show the enormous force that the engineer has 
 at his disposal when he enlists the friendly offices of the 
 bacteria. 
 
 VII. THE PRINCIPLE OF THE CONTROL OF 
 
 PUTREFACTION BY CONTROL OF 
 
 BACTERIAL CONTENTS. 
 
 In a report by Dr. A. C. Houston, M. B., D. Sc, 
 written August 9th, 1898, and since then materially 
 endorsed, we read : — 
 
 "Sewage already contains all the organisms which 
 are necessary for its decomposition and final purifica- 
 tion. In order to discover a method of biological treat- 
 ment all that has to be done is to discover the best and 
 most practical way of allowing the natural purification 
 
17 
 by the action of the bacteria to take place without 
 nuisance or danger. 
 
 "In brief, the so-called biological treatment of sewage 
 is neither more nor less than the attempt to imitate 
 nature's own methods of effecting the decomposition 
 and finally the purification of the effete matter of the 
 animal and vegetable kingdom. 
 
 "Putrefaction has been called putrid fermentation, 
 but putrefaction is rather to be looked upon as a fer- 
 mentation which is putrid or otherwise, according to 
 the conditions under which it is conducted and the 
 degree of its completeness. 
 
 "The products of decomposition by so-called putre- 
 faction are of the most varied kind, and there is no 
 doubt that putrefaction is brought about, not by a single 
 germ, but by a large number of different bacteria, some 
 aerobic, others anaerobic. Each one of these germs 
 may produce intermediary products of widely different 
 character, but all of them, perhaps, tend in the direction 
 of finally resolving highly complex substances to their 
 simplest component parts. 
 
 "Now the organic matters found in sewage are partly 
 in suspension and partly in solution, and sewage con- 
 tains in itself the necessary living germs for the destruc- 
 tion of both these forms of organic matter. The aim 
 and object of the biological treatment of sewage is to 
 render soluble by microbial agencies the solid matters.* 
 In the final process of purification, these substances 
 should undergo oxidation induced by the life processes 
 of nitrifying organisms, and an effluent should be pro- 
 duced, which is free from putrescible matter and con- 
 tains only inorganic or mineral substances. 
 
 "The mere solution of the great mass of the sus- 
 pended matters by bacterial agencies, which is, perhaps, 
 common to all the different processes at present under 
 trial, is a sufficient vindication of the enormous advan- 
 tage to be gained by the biological treatment of sewage. 
 One point which has been rather lost sight of is that 
 there is probably no bacterial process in practical oper- 
 ation at the present time which is not eminently suc- 
 cessful in that it places the sewage in a most favorable 
 state for its final purification by land irrigation. 
 
 "The presence of bacteria in enormous numbers in 
 an effluent does not perhaps necessarily imply that the 
 effluent is of a degraded character and highly putresci- 
 
 * This is accomplished in the Septic Tank, as ex- 
 plained in IX. 
 
i8 
 ble ; it may only mean that the liquid has passed through 
 a previous stage of putrefaction, preparatory to its 
 purification, in which case the danger so far as nuisance 
 is concerned may be regarded as potential and not 
 actual." 
 
 When the sewage is first formed it contains a great 
 variety of bacterial life. As it passes onward through 
 the plumbing arrangements and into the sewers the 
 IDUtrefactive processes become active, and it is the 
 object of good sewers to remove the sewage so quickly 
 that the rapidly generated noisome odors will not be 
 generated until the sewap^e has passed too far awav to 
 offend our eyes or noses. The construction of these 
 sewers is a matter of hydraulic engineering not ger- 
 mane to our subject. The contractor who builds the 
 sewers and often the engineer who designs the sewer- 
 age system knows little or nothing about the life pro- 
 cess that ma^' go on in sewage. He is concerned only 
 that his pipes and sewers shall carry their burden and 
 discharge it from the lower end. How needless it is 
 to say that a better design and better construction can 
 be made by an engineer who fully realizes that his 
 problem of disposing of the sewage really means more 
 than the mere transportation of the offensive matters. 
 
 In the great majority of sewerage systems the whole 
 system is looked upon as a nuisance to be buried under- 
 ground and lost to sip-ht and mind as soon as possible. 
 No thought is given to the mighty forces at work, 
 which, if properly controlled might readily allow of a 
 very material purification of the sewage as it flows 
 onward to the outlet, and all this without offense or 
 material expense, thus often doing away with the need 
 of a large and expensive outfall sewer at the same time 
 that the sewage is discharged in a condition of suffi- 
 cient purity to admit of its profitable use. 
 
 The contents of the raw sewage is well shown in 
 Table I. It will be noticed that each of the objection- 
 able organic impurities, the complete oxidation of 
 
19 
 which is the object sought to be accomplished, already 
 contains a considerable quantity of oxygen. There is 
 also present, dissolved in the water, a considerable 
 amount of oxygen. Since the complete destruction of 
 the organic contents of the sewage is merely oxidation 
 or slow combustion, it is pertinent to inquire what pro- 
 portion of the needed oxygen is already present in the 
 sewage. The amount of oxygen required to oxidize 
 the substances shown in Table II as the principal 
 organic contents of sewage is shown in Table III. 
 
 TABLE III.* 
 
 Pounds of Oxygen Required to Oxidize ioo Pounds 
 OF Certain Substances. 
 
 Substance. 
 
 Oxygen Required by the 
 
 
 
 
 
 
 
 
 
 
 c 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 d 
 
 
 
 
 PM 
 
 
 ^ 
 
 g 
 
 
 S 
 
 O 
 u 
 
 1.^ 
 •d 
 
 
 
 
 S5 
 
 :? 
 
 K 
 
 u 
 
 H 
 
 
 
 52. 3 
 
 S2.8 
 
 II3-3 
 
 248.4 
 
 25.0 
 
 41. 1 
 
 S6.8 
 
 131. 
 
 229.0 
 
 29.4 
 
 45-7 
 
 S6.8 
 
 141-4 
 
 253 -9 
 
 22.0 
 
 
 49.6 
 
 118. 4 
 
 168.0 
 
 49-4 
 
 
 49.6 
 
 118. 4 
 
 168.0 
 
 49-4 
 
 
 I0I.6 
 
 202. S 
 
 304.0 
 
 "•3 
 
 bo 
 
 B <y 
 
 is 
 < 
 
 Gelatin . 
 Chondrin 
 Albumen 
 Cellulose 
 Starch . . 
 Fat 
 
 223.3 
 119. 6 
 231.9 
 118. 6 
 118. 6 
 292.8 
 
 Some of this oxygen is already present in the water 
 of the sewage. At the temperature of 62 degrees F., 
 and at the normal pressure of the atmosphere at sea 
 level, air contains 21 per cent of oxygen and still pure 
 
 ♦ Dibdin, Cit. 
 
water contains 6-10 per cent of oxygen by volume. 
 As the essentially pure water passes from the water 
 supply into the sewers it becomes contaminated with 
 organic matter, and the multiplying aerobic bacteria 
 at once begin to draw upon the oxygen. So long as 
 a supply of oxygen remains distributed throughout 
 the liquid the aerobic bacilli predominate over the 
 anaerobic forms and the putrefaction goes on without 
 the accompaniment of offensive smell. If the with- 
 drawal and use of the oxygen could be offset by the 
 addition of a new supply increasing up to the amount 
 demanded by the rapid growth and increase of the 
 aerobic bacilli, the growth of the anaerobic forms 
 might be permanently held in abeyance and the sewage 
 wholly purified without offense. 
 
 This idea is attempted wherever sewerage systems 
 discharge into large bodies of water, and depend upon 
 extreme dilution to render the sewage unobjectionable; 
 but this method is generally unsuccessful because the 
 amount of oxygen already contained in the sewage 
 and diluted waters, supplemented by additional absorp- 
 tion as the first is used, is not enough* to supply the 
 demand. A very material purifying action undoubt- 
 edly takes place. It may be that the purification is 
 ultimately essentially perfect. 
 
 Attempts to Renew the Oxygen. — The amount 
 of oxygen withdrawn by the life processes of the bac- 
 teria can be replaced in various ways. Permanganate 
 of potassium serves as a deodorizer, and by decompo- 
 sition as a source of supply of oxygen. The action of 
 the oxygen from permanganate of potassium is pecul- 
 iarly selective, acting first on those matters which are 
 
 * Dibdin, Cit., pp. 124-129. 
 
 Rafter & Baker, Cit., pp. 9, 23, 73. 
 
 22nd An. Rept. Mass. State Bd. Health, pp. 525-54^. 
 
 Jour. Frank. Inst., Nov. 1891. 
 
 Trans. Am. Soc, C. E. XXIV, 21. 
 
in an advanced stage of decomposition. In the small 
 quantities possible to employ in sewage purification, it 
 is not an antiseptic. 
 
 Oxygen From Air. — Since the oxygen originally 
 in the water that has become sewage came from the air 
 it has often been tried to utilize the air as the source 
 of re-supply. Complete processes* of purification are 
 dependent upon this idea, the air being driven into the 
 sewage by the aid of pumps. In this way oxygen is 
 undoubtedly added, but the violent agitation of the 
 sewage is detrimental to the action of the bacteria for 
 whose benefit the oxygen is being added ; and the main- 
 tenance of a system of air pumps with men to care for 
 them, is a matter of considerable expense. 
 
 Oxygen by Intermittent Filtration. — The 
 most successful method of adding the needful oxygen 
 is by the method of intermittent filtration by which, at 
 intervals, a certain amount of sewage is run into a 
 filter bed so prepared that the sewage sinks down and 
 through the filtering medium and is discharged, allow- 
 ing the surface and interstices to be exposed to the air 
 for the absorption of oxygen for a certain length of 
 time, before the filter receives its second load of sew- 
 age. This method, while simple in its apparent action, 
 is so important as to deserve a careful analysis. It is 
 not simply a method of filtration, but of the combined 
 straining and filtering out of the suspended and undis- 
 solved organic impurities and the destruction within 
 the filtering medium of both the undissolved and dis- 
 solved organic impurities. It is capable of discharg- 
 ing a filtrate unobjectionable to sight, smell or taste, 
 except for its containing certain mineral nitrates. This 
 result is brought about wholly by bacterial action. The 
 so-called filter beds are really bacterial beds, and as 
 such should be described. 
 
 * Geo. E. Waring's process, as installed by D. A. 
 Tompkins & Co. 
 
VIII. BACTERIA BEDS. ACTION, CONTROL 
 AND CAPACITY. 
 
 Among the earlier attempts in purifying sewage 
 was that of filtration, or the straining of the sewage 
 through beds of sand and gravel so fine as to prevent 
 the passage of the suspended matters. The effluent 
 was soon found* to have also parted with much of its 
 dissolved organic matter. Such a result was not well 
 understood at first, but we now know that it is due to 
 the action of the bacteria contained in the filtering 
 medium. So important is the bacterial action and so 
 much more does it accomplish than the merely mechan- 
 ical action of filtration that the whole process is now 
 designed primarily for the encouragement of the 
 growth and action of the bacteria ; the idea of filtering 
 being essentially a secondary consideration. 
 
 The most energetic nitrifying bacterial action taking 
 place as a result of the life processes of the aerobic 
 bacteria in the presence of oxygen, it has been found 
 best to so design the system that intermittent charges 
 of sewage are passed into the surface of the beds and 
 sinking slowly downwards and draining away from 
 below are followed by the entrance of air. Thus the 
 contained bacteria are well nourished and stimulated 
 to their utmost activity by alternate doses of rich food 
 and oxygen. Earth, sand and gravel are the materials 
 most commonly employed to make the bacterial beds, 
 and these are laid down in layers in previously pre- 
 pared excavations, so connected with the sewage supply 
 that the action of filling first one bed and then another 
 is automatic. 
 
 The earthy filling of the beds acts as a breeding 
 ground for the bacteria, which develop in great num- 
 
 * Reports Mass. State Board of Health, Lawrence 
 experiments. 
 
 Rafter & Baker, Cit., p. 286. 
 
23 
 
 bers and of such varieties as will thoroughly dispose of 
 the raw sewage, destroying the dissolved organic im- 
 purities at once and rapidly acting upon the suspended 
 matters. 
 
 The degree of purification from these bacterial beds 
 IS highly satisfactory.* The amount of sewage that 
 can be applied per acre is far greater than can possibly 
 be utilized by the plant life growing on the filters. In 
 the best English practice 10,000 gallons per acre per 
 day (or a little less than one-half of an inch in depth) 
 is purified by irrigation. In Paris 30,ooot gallons per 
 acre per day (or i>^ inches in depth of water) is dis- 
 charged into the fields per day. Here in California 
 we consider an annual supply of water equal to 24 
 inches in depth per year (applied in six months) an 
 ample supply, or less than one-eighth of an inch per 
 day. This is 3,600 gallons per acre per day. There 
 are cases on record of successful farming in San Diego 
 County for several successive years with quantities of 
 water equal to about one-fourth of this. All of which 
 goes to show that in the purification of sewage by broad 
 irrigation the action of the growing crop is an unim- 
 portant factor, and if we are merely trying to purify 
 the greatest amount of sewage with the least expendi- 
 ture of time and land we can accomplish our desired 
 result more satisfactorily on land prepared for that 
 specific purpose. 
 
 Sewage that has been passed through properly con- 
 structed bacteria beds is so purified and relieved of its 
 objectionable organic contents that it is probably 
 much purer than the ordinary drinking waters fur- 
 nished in cities taking their supply from rivers. In the 
 Lawrence experiments bacterial beds of fine sand were 
 
 * For a statement of the case of Berlin, Germany, see 
 "Sewage Farms of Berlin." H. A. Roechling, Proc. 
 Inst., C. E., CIX, 3. 
 
 t Eng. News, XXXIX, 2. 
 
24 
 
 used only five feet thick. On these sewage was poured 
 at the rate of 100,000 gallons per acre per day. After 
 these had been in use a long enough time to have 
 assumed a stable condition, the effluent from tank No. 
 2 was frequently used for drinking, without any notice- 
 able effect. Seven wells in constant use were chosen 
 to represent an average, and seven purified effluents 
 from seven dififerent tanks were chosen for comparison. 
 The average result is shown in — 
 
 TABLE IV. 
 
 Comparison of Effluent and Well Water^ Lawrence, 
 Mass. Parts per 100,000. 
 
 
 Ammonia. 
 
 g 
 
 
 6 
 
 Nitrogen. 
 
 
 
 Average 
 Effluent from 
 
 1 
 
 
 
 a 
 
 E 
 
 3 
 
 < 
 
 e2 
 
 1 
 
 o5 
 
 u 
 
 J3 
 
 15 
 
 Tanks i, 13, 6, 6, 
 4, 2, 7 
 
 .0060 
 
 • 0113 
 .0086 
 
 .0173 
 .0342 
 
 4-74 
 S-84 
 
 I. 19 
 2.02 
 
 .0002 
 .0011 
 
 238 
 801 
 
 Seven wells 
 
 .0256 
 
 This table does not show that all effluent from all 
 bacteria beds is sufficiently purified to be safely used 
 for drinking water. To quote the words of Hiram 
 F. Mills, M. Am. Soc. C. E. :— 
 
 "Judging by the chemical analysis, there is nothing 
 in the effluents known, or even suspected by chemists, 
 to be harmful. 
 
 "Although nearly all of the bacteria that were in the 
 sewage did not live to pass through the filters, there 
 have been found in the effluents from filters of coarse 
 sand more bacteria than are found in some public drink- 
 ing supplies, and some of these evidently came from 
 the sewage; and, until we learn that disease-producing 
 bacteria are not among those that come through, we 
 
25 
 
 must assume that they may be among them ; and 
 although reduced in numbers to such an extent that 
 they may do no harm, we yet know that bacteria in 
 general increase with enormous rapidity when under 
 favorable conditions, and we do not yet Itnow enough 
 to allow us to assume that the very small number of 
 one or two in a thousand of the number in the sewage 
 that come through may not increase in the human body 
 or under other conditions to such numbers as to be 
 harmful. 
 
 "From this cause we are not able to assume that the 
 effluent from coarse-sand iilters five feet in depth is 
 suitable for drinking water." 
 
 This extraordinary degree of purification is brought 
 about by the- life action of the bacteria, and the object 
 of the engineer is to provide the best breeding and 
 feeding ground for these minute organisms. The 
 action of the bacteria on the sewage is two-fold, and 
 it is possible to so essentially separate these two stages 
 that the modern sanitary engineer can design the puri- 
 fication system in two distinct parts. By reference to 
 Table I it will be seen that of the contained organic 
 matter 43 per cent is in the form of undissolved solids, 
 and 57 per cent is in the form of solids that have been 
 dissolved. Since the desired breaking down of the 
 complex organic compounds is to be a chemical action 
 brought about by the digestive action of exceedingly 
 minute organisms, the first step is to prepare their food 
 in the condition of the finest division possible. This 
 is accomplished by those bacteria having a liquefying 
 or hydrolytic action. It is probable that this liquefying 
 action is largely brought about by certain products of 
 the micro-organisms called "enzymes," which, though 
 not living, are the product of the anaerobic forms of 
 animal and vegetable life. By the production of these 
 enzymes the sphere of action of the liquefying bacteria 
 is considerably widened. This liquefying action being 
 caused mainly by the action of the anaerobic bacteria, 
 
26 
 
 the first work is to stimulate the growth of the anaer- 
 obic organisms. 
 
 When sewage is first formed, by the origin of the 
 domestic wastes, the first putrefactive action must be 
 aerobic, on account of the oxygen dissolved in the 
 fluids and the surrounding air. The presence of this 
 oxygen results in the production of small quantities 
 of nitrates. This initial oxygen, and with it the vivi- 
 fied aerobic forms of organisms are soon exhausted. 
 The action of the aerobic forms is checked even if the 
 bacteria are not wholly destroyed. The anaerobic 
 forms multiply and carry on the work. By their aid 
 the solids are broken down and become liquefied and 
 dissolved in the sewage. The process to this point 
 includes the formation of ammonia, nitrous and nitric 
 acids, free nitrogen, methane, hydrogen, carbonic acid, 
 marsh gas, etc. These gases are inflammable, and 
 can be burned or discharged into the air without 
 nuisance. After the complete liquefying of the organic 
 contents of the sewage it is time to again call in the 
 aid of the aerobic bacteria to nitrify the dissolved 
 materials in the presence of a large amount of oxygen. 
 
 It is feasible to somewhat combine all these pro- 
 cesses and indeed it is somewhat probable that two or 
 more kinds of bacteria acting together can effect 
 decomposition which neither of them can do separately 
 and that in no case can we expect to so differentiate as 
 to restrict the action to one species. 
 
 The most that can be hoped for is to introduce physi- 
 cal conditions that will assist the desirable forms and 
 retard the growth of others. 
 
 In large cities the sewage is from one to two days 
 or more' old when it arrives at the works. At this 
 stage, after being in dark sewers so filled with the 
 exhalations of the decomposing material as to be essen- 
 tially devoid of oxygen, the sewage is already rapidly 
 approaching the condition of a complete liquid. If 
 
27 
 
 this sewage is discharged onto a considerable area of 
 prepared bacteria beds the bacteria there present will 
 rapidly destroy all its organic contents, and that with- 
 out offense to sight or smell. After such a hearty 
 meal some of these bacteria require rest and oxyeen, 
 after which they will not only be ready for another 
 dose of sewage, but will also so increase in number and 
 ability as to effectually purify 200,000 gallons of sew- 
 age on each acre per day. By a careful study of the 
 action of these purifications, it was soon found that 
 the action was controlled by purely biological processes. 
 The mechanical filterinp- action of the soil is actually 
 detrimental, for it causes the coarse particles of sewage 
 to remain on the surface and act as an impervious laver 
 interfering with the free entrance of the sewage into 
 the soil. It has also been found largely by experiment 
 what size and kind of earthy material, and what times 
 for charging and discharging will gain the best results. 
 The whole process has been experimentally worked 
 out, and every step has been checked and re-checked 
 by repeated chemical and biological analyses. 
 
 As a final result we know that success in thorough 
 destruction of the organic impurities in sewage is 
 dependent upon several conditions which may be sum- 
 marized as — 
 
 1. A range of temperature from not lower than 
 20-25 deg. Fahr. for the coldest winter months up to 
 the limit known. 
 
 2. The solution of sewage must not be too strong. 
 
 3. The solution must be slightly, but not more than 
 slightly, alkaline. 
 
 4. The solution must be in contact with the bacteria 
 beds at least three hours. A longer time may give a 
 greater, and a lesser time is sure to give a lesser degree 
 of purification. 
 
28 
 
 5- The bacteria bed must be well aerated after each 
 application of sewage. 
 
 In practice it was found that the most efificient action 
 of the bacteria filter beds was within a foot or two of 
 their surface, but that if coarser materials were used 
 and the sewage not allowed to escape until it had been 
 held in contact with the filtering medium and bacteria 
 for some hours an equal degree of purification was 
 obtained and the action proceeded throughout the full 
 depth of the filter. 
 
 Since the purification is by bacterial action, and since 
 we can approximately control the growth and activity 
 of the various species, we are prepared to control the 
 rate and amount of putrefaction and exhalation of 
 offensive odors, and can carry the destruction of the 
 organic putrescible material to any desired degree of 
 completeness. Air with its contained oxygen admitted 
 into the bacteria beds in alternate doses with liquid 
 sewage, stimulates the growth of aerobic bacteria, and 
 retards the actipn and development of anaerobic forms. 
 Keeping out oxygen stimulates the anaerobic forms at 
 the expense of the aerobic. The complete putrefaction, 
 if it be done without offense, needs a careful adjust- 
 ment of the action of the two forms. We wish to first 
 liquefy the suspended organic matters with the aid of 
 the anaerobic forms. If we push the action of the 
 anaerobic forms too far, we will get a solution highly 
 toxic to aerobic organisms, and one very slow to nitrify. 
 If we stop the hydrolytic action at just the right point 
 the dissolved organic impurities have become an ideal 
 food for the aerobic orofanisms. The attempt has been 
 made to develop the two forms side by side or to obtain 
 bacteria that alone or conjointly with others will com- 
 plete the putrefaction without objectionable exhala- 
 tions, but so far without much success, except by slower 
 
29 
 
 action than when sharp differentiation is attempted 
 between the aerobic and anaerobic forms. 
 
 By carefully dividing: the process of putrefaction into 
 its two parts, the liquefying or anaerobic and the nitri- 
 fying or aerobic, and providing the proper facilities for 
 the assisting of these processes we at once raise the 
 purification of sewage to the level of a science. 
 
 The aerobic forms of bacteria effect the real purifi- 
 cation by destroying the dissolved organic material. 
 Food, oxygen, and rest, delivered alternately to a good 
 breeding ground, is the essential of success, and so suc- 
 cessful is this process today that it is easy to sufficiently 
 purify 2,000,000 gallons* per acre of prepared filter 
 beds each twenty-four hours. This is a depth over all 
 parts of the filter bed of more than three feet per day, 
 or 1 120 feet per year, or, according to the usual Ameri- 
 can practice, one acre of prepared filter bed will purify 
 the sewaee originated by 17,500 people. 
 
 In order that this rapid rate of working shall be 
 kept up, it is necessary that the bacteria in the filter 
 bed should be of no other form and have no other duty 
 to perform than that of destroying dissolved organic 
 impurities, and that the supplies of oxvo-en and food 
 shall be rightly proportioned throughout all parts of 
 the bed. 
 
 The filter beds are, in effect, tanks of a size varving 
 from ten feet square and three feet deep to one hundred 
 feet square and ten feet deep. In one case at Cross- 
 ness, England, a tank is in use having an area of one 
 acre (209 feet square) and a depth of only three feet 
 of filtering material. Whatever size tank is used, it is 
 filled with some coarse material, the particles of which 
 vary from the size of peas to that of eggs. Experi- 
 ence has proved that particles of this size admit of more 
 rapidly filling and emptying the bed and that the enter- 
 
 * Experience at Crossness, Eng. 
 
30 
 ing air more thoroughly penetrates to every part and 
 more easily reaches the colonies of bacteria growing 
 on the surface of the particles ; so that, the whole of the 
 bed being thoroughly drained and thoroughly aerated 
 each time, no opportunity is afforded for the develop- 
 ment of the anaerobic forms, and the whole tank is 
 utilized by the nitrifying aerobic forms. Experience 
 has further shown that coke is the most effective mate- 
 rial for the bed, of a size that will pass through a ring 
 two and one-half inches in diameter but be caught on 
 a ring of one-quarter-inch diameter. Burned clay, 
 coal, and even cracked stones have given most excel- 
 lent results. Sand, earth, loam, cinders and other fine 
 materials give a lesser rate for the same area of bed. 
 It is supposed that this lesser rate is due to the diffi- 
 culty in thoroughly draining a fine bed, the water being 
 held as in a sponge, and there is consequent failure of 
 complete aeration and the development of active 
 aerobic action throughout the whole bed, while the 
 anaerobic forms are allowed a too energetic action. 
 
 The details controlling the admission and discharge 
 of the sewage are simple and well tried. These, as 
 well as the questions pertaining to the exact size and 
 shape and material, the location, and other constructive 
 questions, are directly pertinent to the profession of the 
 engineer and must be varied as the circumstances of 
 each case may require, and the engineer alone, with 
 his knowledge of the stresses, physical and chemical, 
 that each part must withstand, can so design and con- 
 struct the works that premature disaster will not over- 
 take them. 
 
 IX. SEPTIC TANKS, ACTION AND CAPA- 
 CITY. 
 
 With this thorough knowledge of the forces at work 
 in the purification of sewage, we are prepared to under- 
 stand at once the need and action of the Septic Tank, 
 
31 
 the presence of which in Mr. Schuyler's design for the 
 Soldiers' Home has called out this discussion. 
 
 The aerobic forms of bacteria eat and destroy only 
 the dissolved organic impurities. It is, therefore, log- 
 ical that into a bacterial bed suitable for the growth 
 of only aerobic forms we should introduce only such 
 sewage as has had its originally suspended organic 
 contents changed wholly into dissolved organic matter. 
 This change is brought about by anaerobic bacteria, 
 thriving only in the absence of oxvgen. The Septic 
 Tank is for the growth and action of these forms. In 
 essential design it is merely a closed tank, into which 
 the sewage flows so slowly as to produce no eddies. 
 The scum and grease rise to the surface of the sewage 
 and form an essentially air-tight cover. .The sus- 
 pended mineral matter sinks to the bottom. The oxy- 
 gen originally contained in the sewage is rapidly 
 exhausted and the anaerobic forms of bacteria multiply 
 and complete their cycle of life, rapidly liquefying all 
 the suspended organic matter. A very considerable 
 amount of gas is given off, largely marsh gas, but it 
 is without offensive smell, except for a short time when 
 the tank is first brought into use and the aerobic forms 
 of bacteria are endeavoring to work with a deficient 
 supply of oxygen. When the tank has settled down 
 to steadv work on a substantially uniform sewage, 
 the gases eliminated are unofifensive and may be dis- 
 charged freely into the air or burned, the mixture being 
 highly inflammable, as the opportunity offers. 
 
 The sewage, being admitted quietly below the suf- 
 face of the tank at one end, flows quietly out from a 
 point below the surface at the other end, and the tank 
 is so proportioned that the time of passage from 
 entrance to exit will be about twenty-four hours. Such 
 suitable contrivances .are introduced into the design of 
 the tank as will tend to make the movement of the 
 
32 
 
 sewage very uniform and will prevent the access of 
 air. It is not proved that an air-tight roof is essential 
 for the safe-guarding of the anaerobic bacteria, how- 
 ever desirable it may be from an esthetic standpoint. 
 It can do no harm and its action cannot but be benefi- 
 cial in a windy country or where the action of the sun 
 is very intense. 
 
 The discharge from the Septic Tank is in no sense 
 purified; its contained organic material is merelv 
 wholly dissolved and a fit food for aerobic bacteria. It 
 may be fed to the aerobic forms by 
 
 1. Dilution in streams or the ocean. 
 
 2. Broad irrigation. 
 
 3. Intermittent filtration through bacteria beds. 
 
 We have already considered the action of the bac- 
 teria in disposing of the dissolved organic contents. 
 The action and result is the same, however and wher- 
 ever brought about. 
 
 In brief, dilution is only allowable where the water 
 into which the sewage is discharged is never used as a 
 public water supply or for pleasure purposes within 
 the radius of complete destruction of the organic con- 
 tents. Broad irrigation with crude sewage requires a 
 very large acreage of land, and is adapted onlv to 
 certain very special cases, for it is proved beyond a 
 doubt that crude sewage can so contaminate growing 
 crops as to make them unsafe for human consumption 
 and in a lesser degree so contaminate the flesh or milk 
 of graminivorous animals, although it is probable that 
 the processes of the putrefying bacteria destroy the 
 pathogenic germs contained in the sewage, and that 
 broad irrigation will ultimately destroy all pathogenic 
 germs, if thoroughly and carefully carried out. We 
 also know that thorough destruction of sewage by 
 farming it into the soil requires a greater amount of 
 work and more intelligent care than is commonly met 
 
33 
 with. A few cases have been proved where vegetables 
 contaminated by sewage have been the cause of dis- 
 ease. Intermittent filtration through bacteria beds is 
 an absolute destruction of all dangerous sewage. When 
 either irrigation or filtration is preceded by a thoroueh 
 treatment in a septic tank the sewage may be used for 
 irrigation with a perfect feeling of safety as regards 
 health and a perfect immunity from smell or nuisance, 
 but is is not safe to discharge the effluent from a septic 
 tank into any body of water afterwards used as a source 
 of supply for public drinking water, except it be first 
 further purified as by coke bacteria beds. In reference 
 to this there is no higher quotable authority than Prof. 
 Frank Clowes, Chief Chemist to the London County 
 Council, London, England, who says : — 
 
 "It should be explained that the experiments on inter- 
 mittent treatment in the coke beds have been carried 
 out by filling the coke-beds with sewage until the coke 
 is just submerged, then allowing the sewage to remain 
 in contact with the coke for several hours, and finally 
 draining the liquid away completely. The coke is then 
 allowed to remain for some time in contact with the 
 ,air, which fills the interstices of the coke-bed when the 
 liquid has flowed away. This series of processes is 
 repeated at regular intervals. 
 
 "It may be stated that the general results obtained 
 from about ten months' experiments of the coke-bed 
 treatment point to the following conclusions:— 
 
 "Size of Coke. 
 "The use of ordinary gas coke, in pieces about the 
 size of walnuts, seems to be attended with the following 
 advantages, as compared with the use of smaller coke. 
 The larger coke enables the bed to hold a larger volume 
 of sewage. The beds now in use had an original capa- 
 city for sewage which was nearly equal to the volume 
 of the coke which they contained, in place of only 20 
 or 30 per cent of that volume, as is shown by beds con- 
 taining smaller coke. The use of the large coke also 
 allows the bed to be more rapidly filled and emptied, 
 and to be more completely emptied and aerated. 
 
 "Depth of Coke. 
 "A bed 13 feet in depth has now been working satis- 
 
34 
 factorily since April i6th, 1899, and has given a purifi- 
 cation approximately equal to that effected by the four- 
 foot bed. 
 
 "Chemical Purification Effected by a Single Treat- 
 ment. 
 
 "The coke-beds have removed the vifhole of the sus- 
 pended matter, or sludge, from the crude sewage; and 
 they have yielded an effluent which occasionally shows 
 a slight turbidity, apparently due in ordinary flow 
 mainly to the presence of bacteria, which is increased 
 in storm flow by fine clay and mud. 
 
 "Not only has the suspended matter been removed, 
 but the removal of the dissolved oxidisible and putresci- 
 ble matters of the raw sewage has been secured to the 
 average extent of 52.7 per cent by the passage through 
 a single four-foot coke-bed. The effluent thus produced 
 remains free from objectionable odor when it is kept 
 in open or in closed vessels, provided the bacteria 
 present in it are not removed or killed by special subse- 
 quent treatment. 
 
 "Permanency of Coke-Beds. 
 
 "Since the coke-beds have become regular in their 
 action, neither the effluent nor the coke itself has become 
 foul. 
 
 "The capacity of the four-foot coke-bed, has during 
 the period in review been reduced from 50 to 33 per 
 cent of the whole volume of the bed, and this reduction 
 of capacity appears to be mainly due to fragments of 
 straw and chaff, apparently derived from horse-dung, 
 and to woody fibre derived from the wear of wood 
 pavements. (Note. This sedimentation of the coke- 
 beds has now been prevented by a simple but satis- 
 factory device.) 
 
 "Amount of Sewage Which Can Be Treated Daily 
 BY a Superficial Unit of the Coke-Bed. 
 
 "The volume of sewage which can be passed through 
 the coke-bed per unit of superficial area has not yet 
 attained its maximum, since the depth of the coke-beds 
 is being further increased. It originally amounted to 
 SSS.ooo gallons per acre per day for the four-foot coke 
 bed, and to 832,500 gallons per acre per day for the six- 
 foot coke bed. This represents in each case one filling 
 per day; but as has already been stated, two fillings have 
 been made successfully since February, 1898,' and this 
 corresponds to 1,665,000 gallons per acre per day for 
 the six-foot coke-bed. 
 
35 
 
 "The maximum possible rate of treatment by each 
 coke-bed is possibly not yet reached. 
 
 "The above daily rate of treatment will naturally be 
 augmented as the depth of the coke-bed is increased, 
 and if the satisfactory working of the 13-foot bed is 
 maintained, it will treat a volume of raw sewage equal 
 to at least three-and-a-half million gallons per day. 
 (Note. This 13-foot bed is now in active operation 
 at the rate of 4,200,000 gallons per acre per day.) 
 
 "Effect of Effluent on Fish. 
 "Fish die at once when they are placed in the effluent 
 produced by chemical precipitation. Not only gold-fish, 
 but roach, dace, and perch have lived for months in the 
 first effluent from the coke-beds, and they apparently 
 would live and thrive in this liquid for an indefinite 
 time. 
 
 "Bacterialogical Character of the Effluent. 
 "The results obtained by the bacteriological examina- 
 tion of the effluent by Dr. Houston thus far seem to 
 indicate that the coke treatment does not by any means 
 remove the bacteria from the crude sewage, and indeed 
 does not materially reduce the number. It shows that 
 the presence of many of the bacteria in the effluent is 
 possibly unobjectionable, and is probably necessary for 
 the purpose of completing the purification of the effluent, 
 
 "General Conclusions. , 
 "The liquid discharged from the outfall will be sweet 
 and entirely free from smell, it will carry within itself 
 the bacteria necessary for completing its own purifica- 
 tion in contact with aerated river water, and under 
 no conditions can it therefore become foul after it has 
 mingled with the stream. The effluent will in no way 
 interfere with fish-life in the stream." 
 
 X. THE MEASURE OF THE PURIFYING 
 ACTION. 
 
 From Table I we find that 100,000 parts of sewage 
 contain 41 .4 parts of organic matter. It is this small 
 amount of organic matter, less than one pound in a 
 ton, about one pint in fifty barrels, that causes all the 
 trouble, and the thorough destruction of this small 
 amount is our sole object. This organic material is 
 
36 
 not so dangerous in itself as it is dangerous because 
 the home and source of nourishment of myriads of 
 bacteria which are in themselves, or by their secre- 
 tions and waste discharges, or by their own decay, 
 highly poisonous when planted in the human system. 
 We have seen that the process of putrefaction is a pro- 
 cess of graduated purification, and that, in the final 
 product, the sewage is called purified because it is free 
 from orp^anic material. The purifying bacteria were 
 seen to be of two forms, each multiolying and going 
 through its special cycle of work, the one dependent 
 on the other, but not working exactly conjointly, as 
 the material making the most available food for the 
 liquefying or anaerobic forms is not yet ready for the 
 nitrifying or aerobic forms. We have further seen 
 that the giving off of fOul smells is due to the action 
 of the aerobic forms working in a deficient supply of 
 oxygen. By this knowledge of this complete cycle we 
 have a measure of the action. By taking a sample 
 of the crude or partially purified sewage and subjecting 
 it to an analysis of the fornls of its contained bacteria, 
 by a simple determination of what proportion of its 
 originally suspended organic matter has become dis- 
 solved and oxidized, by sight and by smell, we have a 
 means of testing how far has been the progress toward 
 complete purification. Starting with a material essen- 
 tially free from anaerobic bacteria, we watch the rapid 
 growth of those forms and the decrease of the aerobic 
 forms as the dissolved oxygen is exhausted. Then 
 comes the death of the liquefying anaerobic forms and 
 the rapid increase of the nitrifying aerobic organisms 
 and finally the completion of the work and the death 
 of all forms. 
 
 Table No. I shows that in crude sewage that has 
 advanced far enough in the seweraee system to reach 
 the site of the purifying plant there are from one to 
 four million bacteria per cubic centimeter. One cubic 
 
37 
 centimeter is a bulk about equal to one inch of an ordi- 
 nary pencil. When the putrefaction of sewage is active 
 this small bulk contains many million bacteria, and it 
 would be clearly impossible to count its inhabitants 
 even if we could see them or prevent an increase in 
 their numbers while we were counting. The method 
 of counting is to take one cubic centimeter of the sew- 
 age under examination and dilute it with pure water 
 to measure i,ooo or 10,000, or even 100,000 cubic 
 centimeters, and then, taking a small quantity of this 
 dilution mix it with gelatine and pour it onto a glass 
 plate. The gelatine hardens, holding the bacteria fast, 
 and the dilution of the sample of sewage has been so 
 arranged that there are but a few or a few hundred 
 bacteria on the plate, each separated from his neighbor 
 and held fast in a mass of gelatine. Each of the bac- 
 teria grows and makes a marking on the gelatine pecul- 
 ior to his kind and species, giving us ample opportu- 
 nity to count and study them. The amount of the 
 original sample of sewage being one cubic centimeter 
 and the amount of dilution of the water that has been 
 added being known and the number of bacterial devel- 
 opments or colonies on the gelatine plate being counted 
 it is easy to compute how many bacteria were in the 
 sewaee from which the sample was taken. 
 
 The effect upon the gelatine varies with the different 
 species, and nearly all can be recognized by this means. 
 The number and varieties that have been recognized in 
 purifying sewage is very great, but the presence and 
 number or the absence of certain varieties is a marked 
 characteristic of certain staees of the process. 
 
 But as these biological methods of testing the prog- 
 ress of the purification require a knowledge and skill 
 and the possession of facilities not commonly available, 
 other and simpler methods of control are afforded by 
 ■ chemical tests. ' The simplest of these is to make a 
 
38 
 determination of the amount of oxygen necessary to 
 oxidize a given amount of the crude sewage and an- 
 other determination of how much oxygen is needed 
 to any partially purified sample. The ratio is the 
 percentage of purification already completed. This 
 determination is easily made by measuring the amount 
 of oxygen absorbed by any given sample. By apply- 
 ing this idea in detail, we can determine — 
 
 First : The amount of organic matter in the sewage 
 susceptible to oxidizing at any stage of the process of 
 purification. 
 
 Second : The quantity of matter, organic or min- 
 eral, held in suspension or dissolved! 
 
 Third : The quantity of nitrites and nitrates. 
 
 The object of the whole process being the changing 
 of the oxidizable organic compounds into mineral 
 nitrites and nitrates, these points mark the several steps 
 in the process, and an accurate determination of them 
 enables the engineer to gauge the efficiency of his work, 
 to remedy or ward ofif trouble, and to work the purify- 
 ing plant at its best and most economical capacity. 
 
 XL EXAMPLES. 
 
 So many small towns have begun to re-arrange their 
 systems of sewage disposal in accord with modern 
 biological ideas that no complete list can be given. In 
 some cases entirely new svstems have been built, espe- 
 cially by the smaller towns and for the sewage from 
 isolated clusters of buildings, but more often the 
 chanee has been because of dissatisfaction with the 
 results of, and a desire to change, some existing sys- 
 tem, as was the case at the Soldiers' Home primarily 
 under consideration. At London, England, the aver- 
 age daily sewage discharge is 250,000,000 gallons, 
 with a maximum of 400,000,000 gallons per twenty-- 
 
39 
 four hours, and this amount is steadily increasing. 
 Exceedingly costly chemical tanks and processes have 
 been tried and found wanting. At the present time 
 biological tanks and coarse bacteria beds are being 
 built by merely filling the old precipitating tanks with 
 coke. In some cases the sewage is passed through a 
 second bacteria bed immediately after leaving- the first. 
 Sometimes it is discharged directly into the river. In 
 the case of London, so great is the area served, the 
 sewage is generally quite thoroughly liquefied when it 
 reaches the works, so that the sewers themselves serve 
 as a septic tank. The principal variation from the 
 ordinary in London has been making the filter beds 
 thirteen feet thick, which are now handling sewage 
 at the rate of over 4,000,000 gallons per acre per day, 
 with most excellent results. 
 
 On the grounds of a golf club near Chicago a very 
 severe test was made of the septic system. A small 
 club house yielding only 850 gallons per day was fitted 
 with one tank twelve feet square by three feet deep, 
 and the effluent afterwards passed through a bed of 
 coke twelve feet square. Before the season was over 
 the crowds at the club house had so increased that the 
 daily sewage was more than 6,000 gallons per day. At 
 this point the system of purification was overworked 
 and broke down. But a short rest and a few minor 
 changes restored its efficiency, and the only change that 
 has been made in the design is to increase the size of 
 the tank so that the septic tank will have a capacity 
 eaual to the sewage originated in twenty-four hours, 
 and the filter tank will not receive sewage at a rate 
 greater than 500,000 gallon per acre per day. 
 
 As showing what has recently been done the follow- 
 ing table has been prepared : 
 

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41 
 In considering these examples we are limited in our 
 understanding by not knowing just what is the object 
 sought to be accomplished. In some cases it is suffi- 
 cient that the purification as controlled in the bacteria 
 tanks or beds be carried only to such a point as will 
 render the effluent unobjectionable to sight or smell, 
 while in other cases it may be necessary to control the 
 purification of the sewage until it can be discharged 
 almost directly into the source of a public water sup- 
 ply, and herein lies the great applicability and flexibil- 
 ity of the process, — the sewage can be prepared, and 
 that without offense, for the completion of the purifica- 
 tion by dilution or irrigation, or the process can be 
 controlled and the sewage kept within bounds until 
 the final effluent from a series of bacteria beds can be 
 discharged free of every possible contamination objec- 
 tionable to the human system. 
 
 In the arid or semi-arid sections of the country the 
 water contained in the sewage, aside from any manu- 
 rial value of the organic contents, has a very great 
 value for irrigation purposes, a value that may often 
 be saved by some simple treatment. The sewage flow 
 of Los Angeles equals about 700-800 miners' inches, 
 and a small part of this now sells for irrigating pur- 
 poses. 
 
 The wisdom of the City Council has decreed that 
 sewage shall not be used for the irrigation of certain 
 crops because it is feared that onions, strawberries, 
 tomatoes, radishes and celery may transfer raw sewage 
 from the fields to our mouths. There is some such 
 danger if the irrigation is improperly or carelesslv done 
 and the sewage has not first been properly and suffi- 
 ciently purified. If the crude sewage were first sub- 
 jected to the hydrolytic action of the anaerobic bac- 
 teria in a septic tank and then to the nitrifying action 
 of the aerobic forms in pronerly constructed bacteria 
 
42 
 
 beds, the effluent could be most safely used for the 
 irrigation of any and all crops or vegetables, and the 
 manurial values being still retained in the purified efflu- 
 ent, the value of the sewage for irrigation would be 
 materially greater than the value of clear water. It 
 would be very interesting to compare the slight cost of 
 so altering the present sewerage system of Los Angeles 
 as to incorporate a septic tank, a part of which can be 
 the sewers themselves, and a deep coke bacteria bed, 
 with the cost of the present outfall sewer and the large 
 outlay which must be put upon it immediately to rescue 
 it from destruction; and also to contrast the annual 
 cost of maintaining a system that sold 700 to 800 
 miners' inches of purified sewage with the present sys- 
 tem of paying a big price to throw away the greater 
 portion of the most valuable property the city possesses 
 — the irrigation water supply which flows in her 
 sewers. 
 
 Properly purified by these inexpensive methods de- 
 scribed, the sewage of Los Angeles should yield a hand- 
 some revenue — greater than the revenue derived from 
 the sale of river water in the days when it was mostly 
 used for irrigation directly from the stream. 
 
43 
 
 BIBLIOGRAPHY. 
 
 Engineering News, frequent notes, papers and illus- 
 trated articles. 
 
 Engineering Record, frequent notes, papers and 
 illustrated articles. 
 
 "Inland Sewage Disposal." C. P. Bassett, Trans. 
 A. S. C. E. XXV, 129. 
 
 "Self - Purification of Flowing Streams." C. G. 
 Currier, Trans. A. S. C. E. XXIV, 21. 
 
 "Lectures on Bacterial Processes." S. Rideal, Jour. 
 Soc. Arts, London. 
 
 "The Bacterial Treatment of Crude Sewage." 
 Clowes & Houston. Two reports to London County 
 Council. 
 
 "Manual of Bacteriology." Sternberg. 
 
 "Applied Bacteriology." Pearmain & Moore. 
 
 "Purification of Sewage and Water." W. J. Dib- 
 din. 
 
 "Sewage Disposal in the United States." Rafter & 
 Baker. 
 
 Reports of Massachusetts State Board of Health. 
 
 Report to Director of Public Improvements, City 
 of Columbus, Ohio. Julian Griggs and J. W. Alvord. 
 
 "Sewage Treatment and Sludge Disposal." W. S. 
 Crump. 
 
 "The Cesspool." L. P. Kinnicutt, Municipal Engi- 
 neering, XIX, 99. 
 
REPORT ON SEWAGE DISPOSAL 
 
 IfOR THE' 
 
 PACIFIC BRANCH, NATIONAL HOME FOR 
 
 DISABLED VOLUNTEER 
 
 SOLDIERS. 
 
 Near Santa Monica, Cae. 
 
 BY 
 
 James D. Schuyler, 
 Consulting Hydraulic Engineer. 
 
46 
 
 Los Angeles, Cal., June 14th, 1899. 
 
 Gen. O. H. La Grange, 
 
 Governor, N. H. D. V. S., 
 Soldiers' Home, Cal. : 
 
 Dear Sir : — 
 
 The proposition made to the Management of the 
 Soldiers' Home by the City Council of Santa Monica 
 to permit you to connect the sewerage system of the 
 Home with the outfall sewer recently constructed by 
 the City of Santa Monica for discharging the city sew- 
 age into the ocean, has brought the question of the most 
 expedient means to adopt for a permanent disposal of 
 the sewage of the Home to a direct issue. Before 
 deciding to accept or reject this proposition, Major 
 Wm. H. Bonsall, Local Manager, placed the matter in 
 my hands to make a thorough study of the entire situ- 
 ation and report upon all feasible methods available 
 for the disposal of the sewage, with such recommenda- 
 tions as in my judgment seemed most expedient. In 
 obedience to this trust I began the investigation on the 
 15th ult., and have made the necessary surveys and 
 examinations since that date by which the data have 
 been collected that enable me to prepare the following 
 report, respectfully submitted for your consideration : 
 
 The proposition of the City Council of Santa Monica 
 is set forth in the form of a resolution, No 291, passed 
 March 21st, 1899, and embodies the following pro- 
 visions : 
 
 The Home to build a sewage reservoir of 100,000 
 gallons capacity on the Home grounds, to be used as 
 a flushing tank for the main outfall sewer. 
 
 The outfall sewer to be constructed by the Home 
 from this reservoir to a point on Railroad avenue, mid- 
 way between Tenth and Eleventh streets, a distance 
 of 17,000 feet, to be not less than 10 inches in diameter. 
 
47 
 Of this distance 2,600 feet are within the city limits of 
 Santa Monica, which portion of the sewer must be 
 deeded to the City immediately after completion. In 
 consideration of this transfer and for the further con- 
 sideration of $800.00 to be paid annually to the City, 
 the Home would be permitted to discharge its sewap-e 
 through the City system into the ocean. This privi- 
 lege, however, would be subject to abrogation by either 
 party on giving 18 months' notice of intention. 
 
 I examined the plans of the Santa Monica system 
 in the Citv Engineer's office, and the constructed works 
 in the City, sufficientlv to satisfy myself that the capa- 
 city of the system is considerably greater than the pres- 
 ent or probable future requirements of the town for 
 many years to come, and that therefore the addition of 
 the sewage from the Home would not over-tax; the 
 main outfall sewer. Prom the point where the pro- 
 posed connection would be made the sewer is 12 inches 
 in diameter for 2,000 feet, with a capacity of 1,300,000 
 gallons daily when half full; then follows 1,600 feet of 
 14-inch pipe on 2 per cent grade; then 6,753 f^^t of 
 20-inch on a minimum grade; and thence it is 24-inch 
 to the end. The 20-inch pipe has a capacity of 2, c;oo,- 
 .000 gallons daily, and the 24-inch 4,600,000 gallons 
 per 24 hours, running half full. At the crossing of 
 Ocean avenue, where I examined the sewer, the depth 
 of flow was but two and a half inches in the bottom of 
 the pipe, indicating that the svstem is so little used as 
 yet that it is greatly in need of a flushing head to drive 
 out the accumulation of sewage below high-tide level. 
 
 The voluriie of sewage from the Soldiers' Home, 
 applied in 100,000-gallon doses as proposed, would be 
 precisely what is required by the City of Santa Monica 
 to operate their system successfully, and the advantage 
 of such a flushing would be so decidedly in the favor of 
 the City that the annual payment sugeested should 
 
48 
 properly be reversed, and accrue to the Home rather 
 than be a tax upon the Home. In other words, the 
 proposition appears to me to be one which would only 
 be acceptable to the Home as a dernier ressort. If 
 there were no other effective and advantageous ways 
 of disposing of the sewage of the Home the suggested 
 plan would be one to be seriously entertained, although 
 if discharge to the ocean is seriously considered at all, 
 my preference would be decidedly in favor of an inde- 
 pendent outfall sewer to be owned and operated' exclu- 
 sively by the Home, and not be subject to the caprice 
 of the officials who may in future be selected to govern 
 the destinies of Santa Monica, and who would have 
 power to exclude the Home from enjoying the use of 
 the City's main sewer, or even of that portion that had 
 been built by the Home within the limits of the City, 
 at a cost of some $2,400. 
 
 The estimate of cost of the proposed connection with 
 the Santa Monica sewer prepared by Capt. E. J. Rising, 
 Quartermaster of the Home, was $16,000, which cov.- 
 ered the cost of the proposed reservoir and the neces- 
 sary sewer pipe, manholes, etc., from this reservoir to 
 the point of junction. It did not include, however, the 
 sewer pipes required to be laid to connect all the Home 
 sewers so as to discharge into the reservoir, which I 
 find would need 2,350 feet of 6-inch pipe, and 1,550 
 feet of 8-inch pipe, the cost of which would be about 
 $1,200. Captain Rising's estimate coincides with a 
 bona fide bid for the work by a responsible contractor, 
 and as far as it goes it may be accepted as sufficient 
 with the addition of $1,200 for connections in the 
 Home Grounds and a further addition for right of way 
 and engineering, for which two items it would be safe 
 to add another $2,800, making the total cost of this 
 connection $20,000. In the matter of right of way 
 the City of Santa Monica does not propose to provide 
 the same, although the Council, in its proposition offers 
 
49 
 its "best power and influence" to obtain the right of 
 way for the Home. This "power and influence" may 
 possibly not be sufficiently powerful to obtain the neces- 
 sary rights free of cost to the Home, and therefore to 
 cover all contingencies, it would be best to increase the 
 estimate as suggested. 
 
 If the proposed reservoir is to act as the Santa 
 Monica people desire it to act, in flushing out their 
 sewer, it should discharge its contents of 100,000 gal- 
 lons within a period not longer than one hour. At 
 this rate, however, the capacity of the line would be 
 overtaxed, and there would be danger of accumulating 
 so much head on parts of the line as to either burst the 
 pipe or overflow the manholes, and create a public 
 nuisance. The discharge from the reservoir would 
 have to be made with great care to avoid this result, 
 and the gate would have to be raised just sufficiently 
 to fill the sewer, and no more. This, I anticipate, 
 would lead to much annoyance, and require so much 
 special attention as to become a burden to the Home 
 Management. It could never be neglected, or the res- 
 ervoir might overflow. If the discharge were to be 
 made automatic by a siphon, the rate of discharge 
 would still be likely to be excessive, without a fine 
 adjustment of the mechanism, which, with sewage is 
 more difficult to attain than with clear water. If the 
 sewage were allowed to flow without the proposed 
 storage, as it comes from the Home, no reservoir would 
 be needed, but this would not suit the purposes of the 
 Santa Monicans, or comply with their proposition, and 
 if the flow were to come to them in that way and not 
 as a flushing head they would be likely to desire to 
 rescind the contract or take action to compel such atten- 
 tion to the flushing as would annoy the Home Manage- 
 ment. 
 
 Furthermore, the storage reservoir would be a 
 greater source of nuisance and complaint from the 
 
5° 
 neighboring population than anything of which thej 
 have heretofore complained. It would accumulate the 
 solid matter of each day's flow, which would cling to 
 the bottom and sides and be difficult of removal with- 
 out thorough washing and cleaning daily. The site 
 selected for the reservoir is quite near the town of Saw- 
 tell e, and the odor arising from it would be sure to 
 cause complsdnt. To wash it out daily would require 
 additional labor, and a further expenditure of water, 
 which the Home can ill afford to spare. 
 
 The volume of sewage discharged from the Home, 
 as determined on May 27th, by careful measurements 
 over well constructed weirs at each of the sewer out- 
 lets, was found to be as follows : 
 
 Kitchen sewer 12,782 gallons per 24 hours 
 
 Main Barracks sewer 60,959 " " " " 
 
 Hospital sewer 27,859 " " " " 
 
 Small sewer 3,400 " " " " 
 
 Total 105,000 " " " 
 
 This is believed to be about the minimum flow, as 
 the laundry was not in operation on that day. The 
 volume of discharge from the laundry was ascertained 
 approximately from the number of times the washing 
 machines are filled, and computed at 7,000 gallons per 
 day of eight hours. The laundry is now operated 
 three and one-half days each week. The entire weeklv 
 flow may therefore be estimated at 759,500 gallons, or 
 an average of 108,500 gallons daily. This may at 
 times reach a considerably higher amount, possibly 
 120,000 gallons daily, and with the growth of the 
 Institution it would be safe to provide for as much as 
 150,000 gallons per 24 hours. When this volume is 
 reached the 100,000-gallon reservoir would have to be 
 emptied every sixteen hours, and require more atten- 
 tion. Of course, it would be possible to plan a reser- 
 voir which would be emptied automatically at more 
 
SI 
 
 frequent intervals, but this is not the suggested plan, 
 and the expense would be greater. 
 
 Considering all the conditions of the proposition 
 made by Santa Monica, and the complications to which 
 it may lead, I do not hesitate to advise that it be 
 rejected. 
 
 Independent Ocean Outfaee. 
 
 If any plan were to be entertained for discharging 
 the sewage into the ocean either one of two routes for 
 an outfall line may be selected. The shorter one, fol- 
 lowing a contour grade line from the Home to the 
 Northwest corner of Santa Monica, and thence along 
 the Northerly boundary of the City, to the ocean, would 
 require a total length of 25,600 feet of pipe, including 
 1,200 feet of cast-iron outfall in the ocean, and cost 
 approximately $50,000. The other via Ballona Slough, 
 reaching the ocean about one-half mile South of the 
 Santa Monica outlet, would require 33,300 feet of pipe, 
 and cost approximately $62,000, including cast-iron 
 pipe laid on the floor of the ocean about 1,200 feet out 
 from shore, with the necessary wharf for maintaining 
 it. By the Northerly route the pipe would reach the 
 shore where the bluffs are high, be suspended over the 
 railway tracks, and rest on top of the wharf, discharg- 
 ing freely into the ocean above tide level at the end of 
 the wharf. By the Southerly route the low elevation 
 of the shore would probaly compel the pipe to be laid 
 on the ocean bed. 
 
 These alternative plans for carrying the sewage of 
 the Home to the ocean have been considered at the 
 request of Major Bonsall, and are briefly mentioned, 
 for purposes of comparison in the matter of cost, with 
 other plans of sewage disposal to be discussed later on 
 in this report. Both of them are practicable, and 
 feasible, but I do not regard either of them as offering 
 the best solution of the problem, and therefore cannot 
 
52 
 
 recommend their serious consideration, not onlv be- 
 cause of the great expense involved, but for the reason 
 that it would deprive the Home of a very considerable 
 portion of its present irrigation supply. 
 
 Disposal by Irrigation. 
 
 Since the establishment of the Home, nearly twelve 
 years ago, the sewage has been used for irrigating the 
 vegetable gardens, the alfalfa field and the orchards 
 of the Home Grounds. This has been accomplished 
 without offense to the population of the Home, possibly 
 due to the fact that the prevailing winds are from the 
 ocean and carry any effluvia arising from the fields 
 away from the buildings. Complaints have come, how- 
 ever, from the occupants of two or three dwellings on 
 adjacent lands to the East of the Home Grounds, of 
 ofifensive odors, which at certain times in the hottest 
 weather are said to be quite unbearable, and threats of 
 injunction have been made by these neighbors; to pre- 
 vent a continuance of the use of sewage for irrigation. 
 The inhabitants of the village of Sawtelle, adjoining the 
 Home on the South, are also beginning to fear these 
 odors, and are apprehensive of a possible contamina- 
 tion of their, water supply, which is derived from wells 
 sunk on the town site, by percolation from the sewae-e- 
 irrieated fields, which lie at a higher level, and are a 
 part of the sloping plain on which the village is built. 
 The depth of the wells in the town is from 60 to 180 
 feet, and the level of the plane of saturation is from 
 45 to 70 feet below the surface. The valley lands, 
 which are irrigated with sewage, have a general slope 
 of about 2 per cent, and are composed of fine alluvial 
 loam, intermixed with streaks of fine gravel, in irreg- 
 ular channels, which cannot be traced with any special 
 continuity through the land, although following gen- 
 erally parallel with the little surface water-courses. 
 Here and there the gravel is in patches on the surface. 
 
53 
 and excavations show that it occurs in layers alternat- 
 ign with the soil. The general slope of the fields, how- 
 ever, is toward a main water-course to the Eastward, 
 leaduig- away from the direction of the village. I regard 
 it as practically certain that no amount of water applied 
 to the surface in irigating these fields could possibly 
 reach the wells of the town at their great depth, but 
 would be carried away to one side, while the very small 
 amount of water actually applied would be absorbed 
 in plant growth, evaporated from the surface soil, or 
 retained in the soil by capillarity, aside from the fact 
 that all germs of disease or contamination carried by 
 the sewage would be oxidized and destroyed by the 
 natural processes of nature long before reaching the 
 depth or distance which would have to be traversed 
 to permit them to contaminate the well waters of Saw- 
 telle. In fact, the only way the water of these wells 
 could be affected would be by conducting a sewer pipe 
 to each of them and allowing the raw sewage to mingle 
 with the water. The land directly over or around 
 them might be irrigated intermittently, in moderate 
 amount, without danger of contamination, while it is 
 as certain as any other well-established fact that under 
 existing conditions no impurity can come to these wells 
 from the sewage irrigation of the Home. 
 
 On the great sewaee farm of Berlin, Germany, for 
 example, the entire water supply of the people living 
 on the farm, (numbering 7,900 in 1890), is derived 
 from wells, dug in the midst of irrigated fields, and the 
 health of the inhabitants of the farm is so excellent that 
 it has been chosen as the site for four Homes for Con- 
 valescents. The sewage farm is in fact a health resort, 
 rather than a breeding place for disease. This experi- 
 ence is confirmed in all parts of the world where sew- 
 age irrigation is scientifically practiced. The danp-er 
 of impairino- the water supoly of Sawtelle bv continu- 
 ing sewage irrigation at the Home may therefore be 
 
54 
 dismissed from consideration as absolutely groundless ■ 
 and beyond all possibility of ever occurring, unless as 
 I say, the raw sewage is brought directly to the wells 
 and mingled with the water. 
 
 From my examination of the methods of handling 
 the sewage in vogue at the Home I can readily under- 
 stand why complaints of bad odors should have arisen. 
 I found quite a number of foul-smelling ditches where 
 sewage had been allowed to flow so long that the land 
 was supersaturated beyond its ability to absorb further 
 moisture, and the solid matter was putrefying and fes- 
 tering in the sun; shallow cesspools where matter had 
 accumulated and was decaying, and various open stand 
 pipes along the lines of the sewers filled with offensive 
 feces. A number of the garden beds were also water- 
 logged with excessive application of sewage without 
 cultivation, and solid matter was decaying on the sur- 
 face of such over-taxed and over-soaked areas. The 
 sum of all these neglected spots, offensive to the eye 
 and the nostrils, was sufficient, when conditions became 
 most favorable, to create a nuisance to those living to 
 the leeward, and I have no doubt the complaints have 
 not been altogether from imaginary causes. I doubt, 
 however, if the health of the neighborhood has been 
 in the slightest degree impaired, but a bad smell is a 
 nuisance, and it is this fault which must be corrected. 
 It is the duty of every community to care for its waste 
 products and purify or dispose of its sewage in such 
 manner as to render it inoffensive to any. one residing 
 in its vicinity. 
 
 Methods of Sewage Purification. 
 
 As a concrete result of the experience gained in the 
 Eastern States and in England, France and Germany, 
 the disposal of sewage has resolved itself to three gen- 
 eral methods, which are known as — 
 
 I. Broad irrigation, 
 
55 
 
 2. Intermittent downward filtration, 
 
 3. Chemical precipitation, 
 
 and named in the order of accepted preference. A 
 combination of any two of these methods is frequently 
 employed to effect such a degree of purification as will 
 render the effluent admissible into streams from which 
 domestic water supply is derived. The late Colonel 
 Geo. E. Waring, the eminent Sanitary Engineer, 
 writes : 
 
 "To accomplish this natural purification, (by which 
 the water of the foulest sewer can be made as pure as 
 that of the mountain brook), it is only necessary to 
 bring the sewage into contact with light, well-aerated 
 soil. 
 
 "The reducing bacteria always abound in the sewage 
 itself, in the surface soil and in the air, and oxygen, the 
 only other essential, is freely supplied by the atmos- 
 phere. When sewage is spread over a natural surface, 
 it is important that it be applied in thin sheets and 
 intermittently, so that every particle of the liquid and 
 of the soil may come in contact with the air. This is the 
 process known as 'Broad Irrigation.' Where abundant 
 land is available it is the system par excellence for 
 sewage treatment. Under good management 
 
 one acre will purify the wastes of from five hundred to 
 one thousand persons." 
 
 The concensus of opinion of all the leading Sanita- 
 rians of England is unanimous to the effect that the 
 preferable mode of purifying town sewage is by appli- 
 cation to land. Mr. Geo. W. Rafter, M. Am. Soc. 
 C. E., one of the leading Sanitary Engineers of the 
 United States, says, after reviewing the numerous 
 authorities on the subject in extenso, (Water Suuply 
 and Irrigation Papers of the U. S. Geological Survey, 
 No. 3, p. 48) : 
 
 "So overwhelming is this evidence that we must, in 
 the future, consider this part of the subject as what 
 the lawyers call res adjudicata, a proposition absolutely 
 settled and no longer to be called into question." 
 
56 
 On page 29 of the same publication he says : 
 
 "As a problem of efficient purification, therefore, the 
 superior efficacy of the land treatments may be conceded 
 without further discussion." 
 
 Again he writes : 
 
 "Formerly it was considered important to select a 
 sewage farm with reference to the surrounding inhab- 
 itation, because there was a prejudice against such 
 farms on account of the assumed liability of effluvium 
 nuisance. This objection has much less weight now 
 than it formerly had, because experience has fully dem- 
 onstrated that with proper management a sewage farm 
 is no more objectionable on account of bad smells than 
 any other mode of farming. We may conclude, there- 
 fore, in the light of present experience, that an objection 
 to sewage farms on account of serious effluvium nuisance 
 is not well founded." 
 
 The influence of sewage-irrigation upon public 
 health is discussed in Parkes' "Manual of Practical 
 Hygiene," (1884) ; 
 
 "That sewage farms, if too near to houses and if not 
 carefully conducted, may give off disagreeable effluvia 
 is certain ; but it is also clear that on some farms this 
 is very trifling, and that when the sewer-water gets on 
 the land it soon ceases. It is denied that more nuisance 
 is created than by any other method of using manure. 
 
 . . The evidence of Edinburgh, Croydon, Aldershot, 
 Rugby, Rumford and the Sussex Lunatic Asylum is 
 very strong against any influence in the production of 
 typhoid or dysentery by sewage-farm effluvia." 
 
 "It has been proven by very exact and interesting 
 experiments of Haegeli and Buchner,'' (says Dr. Wm. 
 H. Welch, Prof, of Pathology, Johns Hopkins Univer- 
 sity, Baltimore) "that bacteria are never lifted by a 
 current of air from the surface of fluids or from moist 
 surfaces in general. One could remain in a room con- 
 taining any quantity of cholera stools, swarming with 
 cholera bacilli, and there would be no danger of infec- 
 tion with cholera through the air. Bacteria are con- 
 veyed into the air only when they are in a dry condition, 
 and the cholera organism is quickly destroyed by 
 drying.'' 
 
57 
 
 Svibstantially the same reasoning is applied to the 
 germs of typhoid fever and other enteric diseases. 
 
 Without multiplying authorities on this subject, I 
 think you may be assured of these facts : 
 
 1st. That the process of disposing of your sewage 
 by broad surface irrigation, when properly applied, is 
 the most efifective means of purifying and rendering it 
 innocuous. • 
 
 2nd. That while this process may be accompanied 
 by slight odors, these can be so eliminated as to be 
 unnoticeable a few hundred feet distant. 
 
 3rd. That there is no danger to health in these 
 odors, nor any foundation to fear the spread of dis- 
 ease germs from the irrigated fields by wind currents 
 passing over them. 
 
 4th. That there is no danger of your sewage-irri- 
 gated fields ever becoming over-loaded or "sewage 
 sick," if the sewage is properly spread over even a 
 fourth or fifth part of the area readily available for its 
 use, and the land will always be benefited by its appli- 
 cation. 
 
 Furthermore, the value of the sewage for irrigation 
 at the Home can not onlv be rated in the direct pro- 
 portion which it bears to the entire water supply, but 
 for its value as a fertilizer of the irrigated fields. The 
 present water supply of 500,000 gallons daily costs 
 $10,000 per annum. Approximately one-fourth of 
 this volume passes off in sewage. If the sewage were 
 to be carried away to the sea an equal volume of clear 
 water would need to be purchased to replace the loss, 
 as the successful growth of vegetables and fruit at 
 the Home demands constant irrigation to maintain it. 
 This would represent a money value of $2,500 per 
 
 annum. 
 
 The manurial value is still higher. On the basis 
 of our average flow of 108,500 gallons daily I estimate 
 
58 
 that the sewage flow for one year contains the follow- 
 ing elements of plant food : 
 
 Nitrogen 32,900 lbs. worth 17c per lb. $5,493.00 
 
 Phosphoric acid.... 9,250 " " 7c " " 647.50 
 Potash 6,200 " " 5c " " 310.00 
 
 Total $6,450.50 
 
 The values above quoted are the market rates for 
 these minerals in New York. If to this be added the 
 value of the water, and the proposed tax of $800 per 
 annum which the City of Santa Monica desires you to 
 pay for carrying your sewage it is apparent, from these 
 figures, that an acceptance of the Santa Monica propo- 
 sition would virtually mean an expenditure of $20,000 
 for the privilege of throwing away nearly $10,000 of 
 value per annum. Your gardening may not be so con- 
 ducted as to enable you to realize the full value repre- 
 sented by these startling figures, although from the 
 great yield which I have seen produced on the, land I 
 have no doubt you enjoy a very considerable portion 
 of this amount. I am certain that the fertility of your 
 fields would be greatly diminished by discontinuing 
 the use of the sewage. 
 
 Special Advantages oe CaIvIFornia for Sewage 
 DisPOSAi, BY Irrigation. 
 
 The climatic conditions of California, and particu- 
 larly the Southern portion of the state, are specially 
 favorable for sewage irrigation, because of the light 
 rainfall, the large proportion of clear, sunny days, and 
 the general dryness of the air, which renders irrigation 
 necessary and desirable for the production of crops 
 throughout the year. In the Eastern States and in 
 Europe, on the contrary, where the ground freezes and 
 all growth ceases in winter, irrigation at that season 
 becomes more difficult, and it is necessary to resort to 
 
59 
 artificially prepared filter beds for the treatment of 
 sewage. 
 
 The soil of the Soldiers' Home gardens is also favor- 
 able for successful disposal of sewage, while the very 
 large area of the land suitable to irrigation renders 
 it easy to care for the limited volume of sewage in the 
 best possible way. I find that the area at present irri- 
 gated, below the outlets of the sewers, is approximately 
 Ii6 acres, distributed as follows: 
 
 Orchard, irrigated from kitchen sewer and 
 
 partly from main barracks sewer 32.2 acres 
 
 Garden, irrigated from kitchen sewer 10. 4 acres 
 
 Vegetable garden, between main barracks 
 
 sewer outlet and boulevard 10.7 acres 
 
 Vegetable garden, between boulevard and 
 
 hospital sewer outlet 12.9 acres 
 
 Corn field, irrigated from hospital, kitchen 
 
 and barracks sewer 30.2 acres 
 
 Corn field, irrigated from smallest sewer. ... 7.8 acres 
 Alfalfa field, irrigated from laundry sewer. . 11. 8 acres 
 
 Total 116. o acres 
 
 In addition to this there are 20 acres, now in grain, 
 which could be watered by gravity from the main bar- 
 racks and kitchen sewers. When it is considered that 
 the volume of sewage produced might, if necessary, be 
 effectively disposed of on 10 acres at the rate of appli- 
 cation given to the sewage farms of Paris, trance, 
 where the entire sewage of the City is thus being used 
 in irrigation, the area available at the Home is seen to 
 be more than ample. In fact very much more clear 
 water than sewage is used for irrigation at the Home 
 to grow the crops that are planted. 
 
 The; Composition of Sewage. 
 
 In sewage of average degree of dilution it is found 
 that 998 parts out of 1,000 are pure water, one part 
 consists of mineral matter of a harmless nature, salt, 
 
6o 
 etc., and the remaining one part is dead organic mat- 
 ter, which alone has the power of becoming offensive. 
 It is well understood that the decay or decomposition 
 of animal and vegetable tissue is due to the agency of 
 micro-organisms, called bacteria, microbes or germs. 
 These exist naturally in all sewage in enormous ciuan- 
 tities, ranging from a few hundred thousand to several 
 millions per cubic centimeter, (one-sixteenth of a cubic 
 inch). They belong to a vast number of species and 
 are capable of working the most diverse effects upon 
 the materials in which they live. The study of the 
 work of these organisms by such eminent bacteriol- 
 ogists as Pasteur, Frankland, Warington, Winograd- 
 sky, and the biologists of the State Board of Health 
 of Massachusetts, has, within the past ten to fifteen 
 years, added to the scientific knowledge of the world 
 a vast chapter of information which reads like a 
 romance and completely upsets all previously enter- 
 tained theories of the chemical resolution of organic 
 matter into mineral. It is known that conditions which 
 favor one kind of bacteria are deadly to certain other 
 kinds. The species which convert ammonia into 
 nitrous and nitric acids, and which are most useful in 
 the safe destruction of sewage, require oxygen for 
 their activity and life, and are designated, therefore, 
 as aerobic bacteria, while those which produce putre- 
 faction and decay cannot exist actively where much air 
 is present, and require the absence of light and air to 
 do their most effective work. Hence they are called 
 anaerobic bacteria. Both of these species of microbes 
 when properly controlled are the friends of man and 
 the modern processes of sewage disposal are those 
 which intelligently make use of these microscopic 
 orp-anisms for the reduction of the wastes of the world 
 to innocuous mineral matter. Temperature is an im- 
 portant element in promoting the work of these ovp-an- 
 isms, as they are comparatively inactive in temperatures 
 
6i 
 below 40 deg. or above 120 deg. Fahrenheit. The 
 aerobic bacteria are those at work in the soil, when the 
 sewage is applied to the surface, and they exist in 
 greater numbers on the surface, or a few inches below 
 than at greater depths, as they can there get the great- 
 est amount of oxygen. One species convert the 
 organic matter into nitrous acid, and another species 
 transform the nitrous into nitric acid, which combines 
 with mineral bases to produce mineral nitrates, and 
 the process is called nitrification. In this form it be- 
 comes food for plants, and is thus again reconverted 
 into organic matter, and so the eternal round of Na- 
 ture's economy goes on. In order that these bacteria 
 may be periodically supplied with oxygen, and continue 
 the work of nitrification it is essential that the applica- 
 tion of sewage to the soil be made intermittently, to 
 permit each dose to be wholly nitrified before the next 
 is applied. The stirring of the soil after each irriga- 
 tion assists in the work, as it reopens the pores and 
 admits air to the organisms at lower depths below the 
 surface. If the land is overdosed, and sewage is per- 
 mitted to flow in any one place too long a time, the 
 aerobic bacteria are destroyed or checked in their active 
 multiplication, and the anaerobic bacteria have to take 
 up the work. But their action is to produce offensive 
 smells, and for this reason stagnant pools give rise to 
 unpleasant odors. The secret then of successful sew- 
 age irrigation is to keen the sewage in motion, apply it 
 in small doses to the most porous land available, at 
 intervals of not less than three or four days, keep this 
 land well stirred between irrigations, and so prevent 
 the bacteria of putrefaction from taking an active inter- 
 est in the process of having a hand in it at all. In 
 short the organic matter should be burned by oxidation 
 and converted into nitrates by the aid of the microbes 
 that are ready and willing to do the work if given a 
 chance. When the process is finally over, and the 
 
62 
 
 organic matter has been resolved into mineral again 
 the bacteria die from inanition, and the effluent water 
 drained out from beneath the irrigated fields, if any, 
 or from sewage filter beds, is pure, and comparatively 
 free from bacteria. In fact, the effluent is often much 
 freer of microbes than the waters of many springs and 
 wells which are regarded as pure. 
 
 The process called "intermittent downward filtra- 
 tion" is merely an artificial concentration of the process 
 which goes on in broad irrigation. Filter beds are 
 prepared with materials which will admit air freely 
 through them when periodically drained out. They 
 are prepared with underdrains, are filled with coke, or 
 burnt ballast, gravel and sand. The coke is preferred 
 by many authorities because it is of itself porous, and 
 presents a greater surface. The bacteria colonize in 
 vast numbers over the surface of the gravel, sand or 
 coke particles, in thin films, and porosity of the filter 
 is desirable because the nitrifying organisms are thus 
 well supplied with air. For complete nitrification, the 
 sewage must be kept in contact with the organisms a 
 short space of time, and then drained out slowly. Such 
 filters, or bacteria beds as they are sometimes called, 
 are used where sufficient land is not obtainable for 
 broad irrigation, or as a method of treatment in cold 
 countries in winter, as an adjunct to the sewage farm. 
 They cost from $5,000 to $9,000 per acre, and are capa- 
 ble of purifying from 50,000 to 100,000 gallons of 
 sewage per acre daily on an average, applied at inter- 
 vals of three or four days. 
 
 A greater rate of filtration, or what is the same 
 thing, a smaller filter for a given unit volume of sew- 
 age will effect a lesser degree of purification, and where 
 the effluent is to be used for irrigation a very moderate 
 amount of clarifying will answer every purpose. A 
 sufficient number of thern are provided to give the 
 necessary capacity and infermittency of use to each, 
 
63 
 dependent upon the degree of purity desired. Fre- 
 quently the surface of the beds is cultivated, and crops 
 of corn or other produce raised upon them during- the 
 growing season. A bed of this sort, if built at the 
 Home, divided into four compartments, and arranged 
 with means of distributing the sewage, to each in turn, 
 would serve to concentrate all the solid matter of the 
 sewage at one point, where it would be chiefly neutral- 
 ized without creating offensive odors. The paper and 
 other light matter can be raked in piles and burned, or 
 it may be worked into the soil by cultivation. The 
 surface of such a coarse-grain filter can be used for 
 growing certain crops as advantageously as an ordi- 
 nary soil. It would remove all the unsightliness of 
 scattered sewage solids over the fields, and the sludee 
 would become so quickly oxidized as to be compara- 
 tively free from odor. The effluent stream flowing 
 from beneath the filter would be almost clear, and un- 
 distineuishable from hydrant water, although loaded 
 with fertilizing nitrites. 
 
 I append a sketch of this filter, which I have esti- 
 mated to cost as follows : 
 
 Excavation 5,680 cubic yards at 20c $1,136.00 
 
 Clay lining 2,080 " " " soc 1,040.00 
 
 Gravel, screened and 
 
 placed 3>6oo 
 
 2-inch drain tile 2,000 feet 
 
 3-inch drain tile 2,000 
 
 6-inch drain tile 700 
 
 6-inch vitrified pipe. . 600 
 8-inch vitrified pipe. . 400 
 
 Sluice gates 16 
 
 Incidentals 
 
 Total $6,500.00 
 
 A filter of smaller size and cost would probably 
 answer every purpose, although the plan is made for 
 one large enough to render the sewage practically 
 potable. 
 
 " $1 
 
 3,600 . 00 
 
 " 3c 
 
 60.00 
 
 " 3;^c 
 
 70.00 
 
 " IOC 
 
 70.00 
 
 " 17c 
 
 102.00 
 
 " 22c 
 
 88.00 
 
 " $3 
 
 48.00 
 
 
 276.00 
 
64 
 
 If this were located in the field below the present 
 terminus of the Hospital sewer, and all the sewage 
 brought to this point in pipes, there would need to be 
 laid about 2,700 feet of 6-inch sewer to make all con- 
 nections, the cost of which would be about $900. The 
 entire cost of the improvement would therefore foot 
 up $7,400. The cost of operation would be practically 
 nil, as the garden force would be able to attend to the 
 filter without appreciable extra labor. 
 
 Oxidation of Sewage by Forced Aeration. 
 
 In 1894, Colonel Geo. E. Waring invented a process 
 of destruction of sewage by forced aeration, supplying 
 a draft of air by means of fans or blowers to filter 
 beds, constructed and operated similarly to the ones 
 above described, except that they are of much smaller 
 size, and arranged as a series of concrete tanks. This 
 process is in operation at four places in the United 
 States, and the patents upon it are controlled by D. A. 
 Tompkins & Co., of Charlotte, N. C, who estimate that 
 a plant to clarify 150,000 gallons daily will cost $4,000 
 to $6,000, and the operating expense will be covered 
 by the cost of running a fan driven by an eight-horse 
 dynamo, and a man to look after the valves about four 
 times a day. They write that such a plant will remove 
 absolutely all smell and taste, leaving the effluent a 
 slightly milky color, and fully charged with all the 
 mineral fertilizers contained in the sewage, puttinf it 
 in a most desirable form for irrigation. Personally I 
 know nothing of this method of treatment, but under- 
 stand that it merely does the work of the coarse-grained 
 filter, at somewhat greater operating expense. The 
 principle is the same, air being blown through the 
 gravel of the filter from the bottom after the sewaee 
 is drained out, to promote the action of the nitrifving 
 organisms more rapidly and enable a smaller filter to 
 do the work. The entire space occupied by the con- 
 
65 
 
 Crete or brick tanks woukl b'e 60 to 70 feet square, for 
 a iSo,ooo-gallon plant. 
 
 Chemicai, Precipitation. 
 
 Either of the processes above described are prefer- 
 able to the chemical precipitation of the sewage, for 
 which the plant and buildings would cost in the neip-h- 
 borhood of $10,000, and the operating expense would 
 be $8.00 to $10.00 per day. 
 
 Mr. John W. Alvord, M. Am. Soc. C. E.. the dis- 
 tinguished sanitary specialist of Chicago, writes to the 
 author under date of May 29th, 1899, as follows: 
 
 "In the light of our recent success with reduction 
 (septic) tanks and bacteria beds, I certainly regard 
 chemical treatment of sewage as out of date, especially 
 in the vicinity of soils or conditions of climate where 
 broad irrigation is practicable, as in Southern Cali- 
 fornia." 
 
 Septic Tank Treatment oe Sewage. 
 
 One of the most interesting of the newer processes 
 devised for the treatment of sewage is known as the 
 septic or reduction tank system. This was first tried 
 on a large scale in Exeter, England, where it has been 
 in use about three years. 
 
 While the system is regarded as still in the experi- 
 mental stage it has attracted ereat attention and inter- 
 est among the sanitary engineers of the world, who 
 are inclined to regard it as olTering great promise. The 
 process consists of conducting the sewage to a long 
 tank, made air-tight and dark, through which it passes 
 very slowly, emerging at the far end in liquid form. 
 In this tank the work of reduction is done by anaerobic 
 bacteria, the solids in suspension are retained and 
 changed to gas and liauid, while the mineral matter is 
 precipitated to the bottom as an inert, inoffensive ash. 
 The Exeter tank treated 65,000 gallons daily for 22 
 
66 
 months without givinp- any sign of requiring the 
 removal of the deposit. It is located in a thickly 
 settled part of the city and gives no offense. The tank 
 forms marsh gas, and nitrogen gas, but shows no trace 
 of sulphuretted hydrogen. The gas is innocuous and 
 could only be detected by applying a light. It has 
 been used for months for lighting the works and the 
 public baths in the vicinity, using incandescent burners. 
 The flame is odorless and almost without color. The 
 tank is 64 feet 10 inches long, 18 feet wide, and 7 feet 
 to 7 feet 9 inches deep, having a capacity of 6=;, 000 
 gallons. For further purification the effluent from the 
 tank is passed through filter beds, where nitrifying 
 organisms complete the work. The advantage of this 
 process seems to be in the ease with which all the 
 troublesome solids or sludge is disposed of. Every- 
 thing enters at one end, while at the other there issues 
 a continuous stream of fluid, with but slight flocculent 
 particles of dark color, distributed through it. 
 
 Similar reduction tanks have been constructed near 
 Chicago within the past year or two by Mr. J. W 
 Alvord. in connection with coarse-grain filters, with 
 satisfactory results thus far. 
 
 At Champaign, 111., a septic tank of practicallv the 
 same design was built for the treatment of about 300,- 
 000 ?allons of sewage daily, and is reported to work 
 satisfactorily. It was planned and constructed by /f. 
 N. Talbot, M. Am. Soc. C. E., Professor of Sanitary 
 Engineering at the University of Illinois, and was 
 made 45 feet long, 16 feet wide, with a central division 
 wall, forming two tanks in one, and carries five feet 
 depth of sewage. Partitions or baffle boards reach 
 down into the sewage from the top to within two to 
 two and one-half feet of the bottom, which hold back 
 the floating crust of excrement (that forms to the 'depth 
 of several inches on the surface, ) from moving toward 
 the outlet. The fluids from the tank are permitted to 
 
67 
 escape through a slotted pipe, placed some depth helow 
 the surface, the pipe discharging outside over a weir 
 that controls the level of the sewaee inside within a 
 range of less than two inches. The deposit on the 
 bottom of the tank, which mav be removed once every 
 year or two, is described by Professor Talbot in a pri- 
 vate letter to the author as — 
 
 "a thick, black silt-like material containing about 60 per 
 cent water, 35 per cent inorganic matter, and S per cent 
 organic matter. The inorganic compounds are so stable 
 that after removal they do not seem to give off any 
 particul-ar odor, although at the time of cleaning out 
 the tank and around the pit in which the sludge is 
 discharged, there is an odor similar to that of dirty 
 water, but I do not think it could be , noticed 300 feet 
 away. At other times there is no perceptible odor in 
 the neighborhood of the tank, though it must be borne 
 in mind that the effluent discharges into a stream under 
 water. By putting one's nose close to the end of the 
 effluent sewer where the air current comes out of the 
 sewer, a slightly musty, swamp-like odor may be 
 detected. I have had a bottle of the effluent in my 
 office for five months and have not at any time found 
 any odor which indicated a decomposition. There has 
 been a slight growth of greenish algae in the bottle 
 similar to that which is found about horse-troughs 
 supplied with good well water. A rough deter- 
 
 mination of the ordinary bacterial content showed that 
 90 per cent of the bacteria of the sewage were taken 
 Qut . The sludge taken care of seems to amount 
 
 to about four cubic feet of dry matter per million 
 gallons of sewage treated, a quantity not over one-fifth 
 of that required to be discharged by the chemical pro- 
 cess." 
 
 Sketch No. 2, attached herewith, shows a design of 
 a septic tank for the treatment of the sewage of the 
 Home, which appears to me of proper proportions. I 
 estimate the cost as follows : 
 
68 
 
 Excavation, 450 cu. yds. at 20c $ 90.00 
 
 Concrete walls and bottom, 3,000 cu. ft. at 30c. . goo. 00 
 
 Concrete and iron cover, 1,000 sq. ft. at soc. . . . 500.00 
 
 Pipe, weir, valves, etc 310.00 
 
 Total $1,800.00 
 
 Pipe for connecting all the main sewers to the 
 
 tank 900.00 
 
 Total cost $2,800.00 
 
 While the evidence obtainable regarding the effi- 
 ciency of the septic tank system is all favorable to its 
 success, and its use is rapidly extending, it must be 
 borne in mind that, as before remarked, it is still 
 regarded as in the experimental stage. Its cheapness 
 and apparent simplicity are all in its favor as compared 
 vi^ith other systems, and I am inclined to recommend 
 its trial notwithstanding a possible doubt of its effect 
 in reducing the fertilizing value of the effluent sewage. 
 Its action appears to be in the direction of removing 
 the nitrates, which afford most of the desirable plant 
 food, although the effluent from it would unquestion- 
 ably be richer in fertilizing elements than clear water. 
 
 Summarizing the various plans of disposal discussed 
 in this report, the estimates of cost appear as follows : 
 
 Ocean Outfall Plans: 
 
 Connection with Santa Monica sewer system. .. .$20,000 
 Fixed charges of $800 per annum, capitalized at 
 
 S per cent 16,000 
 
 Total $36,000 
 
 (The cost of maintaining main sewer, attending to 
 reservoir discharge, cleaning, etc., is neglected in making 
 this comparison.) 
 
 Independent outfall by Northern route $50,000 
 
 Independent outfall by Southern route 62,000 
 
 Disposal on Home Grounds : 
 
 Intermittent filtration in coarse-grain filters 7,400 
 
69 
 Oxidation by forced aeration, first cost. .$ 6,000 
 Capitalization of operating expense at 
 
 5 per cent 7,300 
 
 13,300 
 
 Chemical precipitation, first cost $10,000 
 
 Capitalization of operating expense at 
 
 S per cent 58,400 
 
 68,400 
 
 Septic tank 2,800 
 
 Considering all the conditions, I make the following 
 recommendations : 
 
 That the kitchen sewer be joined by a direct line 
 from the tunnel to the present terminus of the main 
 barracks sewer, and that at this point a septic tank be 
 constructed at a cost not to exceed $2,800, including 
 the pipe connections, to be used experimentally for the 
 treatment of the portion of the sewage uniting at that 
 points ; 
 
 That the effluent from the tank be liberally diluted 
 with fresh water and applied to the fields in irrigation ; 
 
 That the importance of the proper care of the sewage 
 be recognized by the appointment of a sewer inspector 
 of more than ordinary intelligence, whose duty it shall 
 be to see that the sewers are kept properly flushed, all 
 the manholes kept clear of floating solids, and that all 
 offensive places on the farm be eliminated ; 
 
 That the distribution of the sewage shall be made 
 intermittently, and that no portion of the soil be per- 
 mitted to become "sewage sick" by over-dosing, and 
 
 That all the ditches be kept clean and the ground 
 stirred and cultivated after each irrigation. By atten- 
 tion to these details there should never arise the slight- 
 est cause of complaint, and the sewage of the Home 
 can be forever cared for on the Home Grounds, without 
 the least danger of epidemics, offensive odors, or the 
 contamination of the neighboring water supply. 
 
 The need of a careful patrol system was illustrated 
 on the 6th inst., when I found the Hospital sewer 
 
7o 
 choked and overflowing at a manhole in the alfalfa 
 field. This should never occur, or if it did occur the 
 remedy should be promptly applied and the sewer 
 inspector held responsible for the perfect condition of 
 the system at all times. Other Departments of the 
 Home are managed with military precision, and order 
 and cleanliness are everywhere apparent. In this, one 
 of the most important of all the economies of the Insti- 
 tution, there is an apparent lack of intelligent super- 
 vision and careful attention, which should be promptly 
 reformed. 
 
 Trusting I have made my views clear on this subject, 
 I beg to remain, Dear Sir, 
 
 Faithfully Yours, 
 
 JAMES D. SCHUYLER. 
 Consulting Hydraulic Engineer.