Bacteriological Investigations OF THE Iowa State College Sewage. BULLETIN No. 2 By L. R. WALKER. Reprint from Proceedings Iowa Academy of Sciences, 1901 DES MOINES BERNARD MURPHY, STATE PRINTER. 1901. UNIVERSITY OF ILLINOIS LIBRARY BOOK CLASS WlS VOLUME *1 FosPfav.F \ BACTERIOLOGICAL INVESTIGATION OF THE IOWA STATE COLLEGE SEWAGE. V) - - ft L. R. WALKER. INTRODUCTION. As an introduction to the consideration of the Iowa State College sewage, the kinds of sewage, the necessity of disposal, and several of the most important methods with their merits and disadvantages will be discussed. It has been my object in the following paper to bring together the data obtained from the bacteriological analysis of the college sewage, including daily samples from the effluent and weekly samples from the manhole and tank. Together with this data are given the daily temperatures of the air and of the sewage, at the time of taking samples; also, the soil temperatures, which were taken once a week. Besides this data it has seemed desirable to give the methods employed in the determination of the number of bacteria per cubic centimeter of the sewage. And lastly, a partial interpretation of the results obtained, has been attempted, special attention having been given to the percentage of gas producers present in the manhole, tank, and effluent, and to the fluctuations, during the different days and seasons, of the number of bacteria per cubic centimeter in the samples from the manhole, tank, and effluent. The determination of the species of bacteria present in the sewage has not been attempted, only incidentally. From a sanitary point of view there is no question of more vital importance than the proper disposal of sewage. The lack of such disposal brings a multitude of evils, o l O 6 >>o — 2 — which often culminate in prolonged illness, or even death; not only is waste of all kiuds a menace to the public health, but it is also a repulsive sight to the aesthetic tastes of any civilized community. This last factor alone would make sewage disposal a question of considerable importance, as the value of property depends to a consid¬ erable extent upon its attractiveness, and anything which takes away from its good appearance deducts from its market value. The question of sewage disposal is coming to be recog¬ nized by the officers of the state boards of health in the various states. Perhaps, as leaders in this movement, may' be mentioned Massachusetts, Connecticut and Maryland. The State Board of Health of Iowa (14), in its annual report for 1899, called especial attention to the almost utter lack of adequate means of sewage disposal in the small towns and cities of the state, and urges that some action be taken toward securing proper sewage disposal. In considering the question of sewage disposal it may be well to define what is meant by sewage. Sewage, accord¬ ing to Barwise (3), comes from the Anglo-Saxon word seon, which means to flow down and includes the liquid contents of a sewer. Rafter and* Baker (5), however, give sewage as including not only the combined water and waste matters flowing in sewers, but the mixed solids and liquid matter. This latter, it seems, is a better definition as it includes the solid excreta as well as the matter in solution. The kinds of sewage will necessarily vary with the im¬ posed conditions. The most common may well be termed domestic sewage, which contains kitchen slops and all the common refuse of ordinary dwellings. Factory sewage is more complex in most cases, depending, of course, upon the particular kind of factory under consideration. Pack¬ ing house sewage would hardly come in this category, yet it plays a very important part in sewage disposal on ac¬ count of its peculiar constituents. Surface sewage, if such it may be called, is composed chiefly of water, and the washings from the streets, alleys, etc. City sewage being — 3 — essentially a compound of all the above mentioned, with the addition of others not enumerated, make it very com¬ plex and hard to deal with, as the plan adopted must needs be one which takes into account all its peculiarities and treats it accordingly. After what has been written on the subject of the necessity of sewage disposal it seems almost needless to try to add anything new. Yet it may be of interest to make a brief review of the already published facts. That sewage is a source of contamination and disease has long been established, many cases of typhoid fever have been directly traced to the lack of proper sewage disposal or the contamination of drinking water with sewage. Barwise records an outbreak of typhoid fever at Wesleyan Univer¬ sity, Middletown, Conn., in which there is indisputable evidence that it was due to the eating of oysters which had been grown in water contaminated with sewage. He also reports an interesting case of sewage contamination of the water supply at Tees. Bacillus typhosus is not the only pathogenic germ found in sewage as numerous experiments have shown, that Bacillus anthracis , (1) (the Bacteridie du charbon, of the French) not only lives in water but that it maintains its vitality for some time is well know. The spirillum of Asiatic cholera has been known to retain its vitality in the domestic water supply of Berlin from 267 to 882 days. (15). The Bacillus coli-communis and Bacillus cloacae while strictly speaking are not pathogenic are always to be regarded with suspicion when they occur in water as they frequently do. (5). Many disease germs may live in sewage for a short time and be propagated there. Thus it can be readily seen that polluted water is a possible source for almost any bacteriological disease. It is a fact of common observation that sewage pollution of streams is detrimental to the fish it contains, and indeed cases are recorded where the entire fish life of a stream for a given distance has been destroyed by sewage pollution. A case of this kind happened in our own state a few years ago at Marshalltown. — 4 —- If no diseases were produced by unpurified sewage, the stench arising from it would be sufficient reason for urging its purification. In this connection it may be well to state that Dr. L. P. Kinnicutt, (15) of Polytechnic, Boston, in a paper, “Sewer Air and Mistaken Ideas Regarding It,” main¬ tains with a considerable force of reason that it is not as harmful as commonly believed, but even this does not do away with the fact that it is decidedly disagreeable. Now that we have noticed some of the reasons for sew¬ age purification it may be well to investigate some of the various means by which it may be accomplished. In a short paper it is impossible to go into details of all the various systems or indeed to even consider them all. So this paper will be confined to the treatment of the follow¬ ing systems: Natural dilution, sewage farming, chemical precipitation, filtration both continuous and intermittent, the septic tank, and the combination of several of these systems into combined systems. The natural dilution of sew T age can hardly be called a system, and yet it is the only means employed in the vast majority of cases. It is nothing more or less than the allow¬ ing of sewage, to flow into the natural waterways, seas, etc. In this way the concentrated sewage becomes diluted (hence the derivation of the name applied) and nature does the rest. If it were not for the fact that the majority of towns and cities draw their water supply from the rivers on which they are situated, in some few cases it might do very well. A great many factors must be considered in determining the effectiveness of natural dilution, among which the most important are the rapidity of the stream and the volume of water that it carries. As all the rivers in Iowa are relatively small and unimportant this method cannot be considered as sufficient in itself in this state. The system of sewage farming has been employed quite extensively in various places, but is not commonly consid¬ ered as a success. The method employed is similar to that used in .irrigation. The sewage is allowed to flow through a system of trenches provided with flood gates so that the flow can be controlled. The theory is, and it is correct, that the — 5 — plants of the fields to which this is applied will, finally incorporate it into their own tissues after it has been decom¬ posed by bacteria. As can be readily seen such a system must have several serious disadvantages. First, granting that sewage farming will purify the sewage, which no doubt can be done to a greater or less extent owing to the imposed conditions it is still doubtful whether or not it could be carried on successfully in a great majority of cases. In the first place the land must be of such a character as to per¬ mit of the irrigation system; secondly, if the sewage were applied continuously, it would be disastrous to the crops, killing them out as well as preventing the nitrification of the sewage by limiting the supply of oxygen to the soil. In the third place, the amount of desirable land required would in many cases be very expensive if it could be obtained at all. Mr. B. S. Brundell, M. Inst. C. E., who has constructed many sewer farms, among them a farm at Dorchester, Eng¬ land, which is one of the most successful from a sanitary point of view, wrote as follows: “Sewage if properly ap¬ plied to land may be purified, but the operation is not prof¬ itable. That is to say, sewage farming cannot, save in ex¬ ceptional instances, be made to pay.” Mr. Brundell also brings up the additional factor of cold winter weather and seriously doubts whether or not the system could be suc¬ cessfully used in cold countries on account of the protracted cold winter. A very good short account of the Berlin, Ger¬ many, sewage farm is given by Barwise. Chemical precipitation was an effort made on the part of some to entirely purify sewage by the addition of chemi¬ cals. The principal precipitants used are lime, iron, alumi¬ num hydrate, alum, and copperas. Although the chemicals used for this purpose are almost innumerable, results tend to show that only the solid matter in suspen¬ sion is removed, while the sewage is deodorized for the time being. Extensive experiments with chemical pre¬ cipitation of sewage were made by Mr. Bibden in England as well as by the Massachusetts State Board of Health in America under the supervision and charge of Allen Hazen. The cost of constructing a plant for the chemical precipi- I — 6 — tation of sewage is considerable, besides there is left on hand a sludge which must be disposed of. This would not be a serious drawback if it were valuable as a fertilizer, but chemical analysis seem to show the contrary to be true. On the whole, chemical precipitation is not re¬ garded with favor by the majority of experts. Filtration is the 'application of raw or precipitated sewage to beds composed of various substances, either continuously or intermittently. In 1870 the first report of the royal commission on the best means of preventing the pollution of rivers was made. In regard to the filtration method it contained the following: “The process of filtration through sand, chalk, or cer¬ tain kinds of soil, if properly carried out, is the most effective means for the purification of sewage. In con¬ tinuous filtration the sewage is applied to the beds indef¬ initely without giving them time to rest. This was found to be unsuccessful so a system of allowing the beds to rest at stated periods was tried and found to be highly success¬ ful. This latter method is known as the intermittent fil¬ tration of sewage. This system of filtration recognizes the fact that the active agents in the purification of sewage are minute plants; variously named microbes, mi¬ cro-organisms, germs, bacteria, etc. Bacteria is the name now commonly accepted and used in scientific writings and discussions. Certain species of bacteria have the power of breaking up the complex organic compound of sewage into simpler inorganic harmless compounds. This process is commonly spoken of as nitrification and the bacteria as nitrifying organisms, because the chief inorganic substances formed them are nitrites and nitrates. There are other species of bacteria however that decompose organic materials into various gases, hydrogen (H), carbon dioxide (C0 2 ), marsh gas (CH 4 ), nitrogen (N), ammonia (NH 3 ),etc. Gas-produc¬ ing bacteria will be spoken of again in connection with the septic tank. Filter beds, as those used for filtration of sewage are called, are composed o*f various materials: sand, gravel, -7 — coke breeze, chalk, clinkers, clay, cinders, ballast, etc Experiments with different materials have been tried at various places. The Massachusetts State Board of Health has probably done the most work along this line in . America. Dibden and Thudicum of England, however, are the pioneers in this line of investigation. There is no small amount of discussion as to the relative merits of the vari¬ ous substances used as fillers in filter beds. But no matter what the material, the object to be obtained in all cases is the same, namely, a substance that will serve as a resting place for the gelatinous masses of bacteria. Any substance that will do this and still be porous enough to admit of complete aeration may be termed a successful filler. For plans of beds, materials used, dimensions, etc., no better information can be obtained than that in the Mas¬ sachusetts State Board of Health reports, and for the plans and specifications of the Iowa State College Sewage Plant by Prof. Marston (19). There remains yet the septic tank. It is a tank in which the sewage is retained for a limited time in order to allow the anaerobic bacteria to work. Two kinds have been employed, the open and the closed. Most experimenters along these lines are now of the opinion that one is as effective as the other, on account of the scum (composed essentially of bacteria) that covers the sewage in the tank. According to L. P. Kinnicutt (16) the following changes are due to anaerobic bacteria in a septic tank. First, the decom¬ position of cellulose and allied substances, and the formation of marsh gas. Second, the decomposition of complex nitrogenous organic matter, with the production of am¬ monia, hydrogen and odoriferous substances. Third, the removal of oxygen from nitrates with simultaneous oxida¬ tion of organic matter. As has been stated before, the filter bed gives an excel¬ lent opportunity for the action of aerobic bacteria, to which, according to Kinnicutt, the following changes are due: The conversion of urea, and similar substances into ammonium salts, and the conversion of ammonium salts — 8 — into nitrates. This being the case the question at once arises, why would not the system of intermittent filtration and of the septic tank work well together. Experience has taught that they do and it is to a'system of this kind that the remainder of this paper will be devoted, taking as a. basis the sewage system of the Iowa State College. Great credit is due Prof. Marston, who introduced this system in Iowa. TABULATED BACTERIOLOGICAL RESULTS. TEMPERATURE. September i.. September 2.. September 3.. September 4. September 5.. September 5.. September 5.. September 6.. September 7.. September 8.. September 9.. September 10.. September n.. September 12.. September 12.. September 12.. September 13.. September 14.. September 15.. September 16.. September 17.. September 18.. September 19.. Septemper 19.. September 19.. September 20.. September 21.. September 22.. September 23.. September 24.. September 25.. September 26.. September 27.. September 27.. September 27.. September 28.. September 29.. September 30.. Orfnhpr t W. E. 2,400 4,800 880 1,320 600 E. E . W. E. E. E. YV. E... 9,000,000 Tank. 1,800.000 E. E . 1,920 1,840 1, 560 1,420 3.800 3,640 2,160 W. E. W. E .. E. E. W. E . W. E. E. E Manhole. 8,600 00c Tank .. 2,050.000 E. E 2,400 3.600 2,760 3 , 96 o 3 , 78 o 2,920’ 4,080 W. E E. E .. W. E... W, E W. E .. W E .. M anhnlfi 7,260,000 Tank 2,170.(00 W E 3,660 2, 520 2,760 5,400 9,000 9,120 8,040 8,160 YV E . W E W E W E W E W E . E E M anhnlp 9,600,000 Tank 6,960,000 E E 4,400 4,100 3,800 3 , 76 o 3,720 3,720 E E E E .. OO OO LT» O 8 3,245,000 3,660 E E (Trfnhpr o E E Orfnhpf ^ E E Orfnhpr 3 M anhnlp 4,800,000 Oct^her 3 T ank 4,200,000 Orfnhpr | E E 5,160 4,820 5,040 5,880 5 , 4 oo 6,120 7.280 Orfnhpr ^ E E Orfnhpr h W E O^fnhpf 7 W E Orfnbpf & W E Opfnhpf Q E E Ocfohpr in YV E ()pfnh^r t n Manhnlp 6,480,000 Opfnhpf in l^nk 4,618,000 October T T E E 4,200 4,080 October 12. E. E . BACTERIOLOGICAL RESULTS —Continued. D.ATE. From. TEMPERATURE. Manhole. Tank. c