Indiana State University - Sycamore Yearbook (Terre Haute, IN)

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THE NORMAL ADVANCE a . 11 ym can be produced practically as pure from a sanitary standpoint, at less than one hundredth of this cost. Also, freshly distilled water is not pleasant to the taste and is condemned by many, though after standing for some time it usually loses some of its disagreeableness. For these reasons it is not thought practicable to supply cities by this means except Where other methods fail. Gibraltar derives her water from huge cisterns filled during the rainy seasons, yet a distillation plant is ready at any time to furn- ish water from the sea. The vessels of the United States navy all use distilled water for two reasons. First, it is pure and sanitary and the physical condition of the men proves its worth. In the second place coal Will furnish enough heat to distill from seven to nine times its own weight of water, hence it is cheaper to carry the coal than water, as all unnecessary weight is cast aside in a ship of war. The second system is known as the English filter bed system. It is the oldest method, and, according to the quality of water produced, is probably the cheapest. It requires no expen- sive machinery and is easily constructed and cared for. In general it is a large shallow reservoir having as its bottom severalvlayers of tiltering material, under Which is a suitable drain to lead the purified product off to a stor- age basin. These reservoirs vary in size from one-half to two acres in area, though the ten- dency at the present time is to have smaller reservoirs and a greater number of them. In warm climates Where there is no danger of freezing they are left open, but in places Where the mean J anuary temperature is below freez- ing, they are usually covered With a cement roof. The method of building these reservoirs varies With local conditions. Some are built of dirt, usually lined With brick, others are built of cement7 Which is probably more commonly used now. The sides are not built straight but are grooved horizontally in many ways to pre- vent the water from washing out a regular course straight down to the outlet. The total depth is regularly not more than ten or twelve feet. The bottom layer is sometimes composed of ordinary drain tile, laid side by side in rows With open joints. It is evident that this would permit of an easy escape of the water. In other plants these are replaced by lines of six- inch pipe laid about one foot apart. The suc- cessive layers of filtering material that are used , by one of the water companies of London are as follows: coarse gravel, nine inches; fine gravel, nine inches; coarse sand, twelve inches; fine sand, thirty-six inches. On top of this the water to be filtered is allowed to stand forty- eight inches deep. These layers, of course, vary much, but in the main are similar to the ones mentioned. The analysis of water may Show that a deeper layer of sand is necessary. The water passes. slowly down through these layers, leaving most of the suspended matter on the surface of the first one. This suspended matter forms a slimy mass called ttzoogloea jelly;y Which gathers bacteria and other impurities not actually suspended in the water. F rom this it Will be seen that a filter bed Which has been in use for some time would do better work than a new one, and this is always the case for this layer of 4tzoogloea jellyh is the main factor in taking out bacteria. This fact gave the build- ers of these plants much trouble at first be- cause they could not make them produce as pure a water as the old ones did. Whenever the layer of slimy material becomes too thick it Will not allow water to pass through; then the reservoirs must be emptied and cleaned. The dirt forms a hard crust Which is easily broken up, lifted 0E the sand layer, and carted away. This must be done about every two weeks, depending upon the amount of sediment in the water. Usually before being run into these reservoirs the water is allowed to stand for some time in a settling tank to take out the heavier particles. The cost of constructing these filter beds varies very much. The probable average cost, however, for the open kind is about forty thousand dollars and for the closed sixty five thousand. The cost of maintaining a plant of this kind is not large, so that the esti- mated cost per million gallons of pure water is from two dollars and hfty cents to four dollars.

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10 THE NORMAL ADVANCE of it as Horace did from his more simply-tilled acres. We trust that Horace did a little hoeing and farming himself, and that his verse is not all fraudulent sentiment. In order to enjoy . agriculture, you do not want too much of it, and you want to be poor enough to have a little inducement to work moderately yourself. Hoe while it is spring and enjoy the best anticipa- tions. It is not much matter if things do not turn .out well. DEPARTMENT OF SCIENCE Artificial Purification of Water ELMER A. ROW Pure water is becoming more and more recog- nized as a necessity for the preservation of life and health. This conviction has been growing from the time of the earliest ancient peoples, and is every day becoming a question not alone for the chemist, but for the consumer as well. Pliny, a recognized ancient historian, devoted much space to the discussion of pure water, and other writers did likewise. Conditions in those times were not any different in regard to the quantity of water at hand than they are at the present time. Rome built nearly four hundred miles of aqueducts which supplied her population with fresh pure water from the mountains, instead of the Tiber river. TheSe must have been built at an enormous expense, many times greater than that of installing a modern filter plant, yet the Romans recognized their value, and what Rome saw the necessity of she generally obtained. Traces of the im- mense cisterns, eighteen in number, may still be seen at Carthage, which drew her water supply from springs nearly fifty miles away. This demand has grown through centuries until now we must have water, purified not only by nature, but also by mechanical means until we know absolutely that we are drinking pure water. But why be so exacting as to the quality of naturels beverage? By far the greater per cent of cases of our most dreaded fever, typhoid, may be traced directly to the presence of the Bacillus Typhosus in the water supply from which the patient used. In a great many instances the great outbreaks of cholera and plague in the far East were check- ed only when a supply of pure water was made available. These facts alone are sufficient to demand pure water for our future use. The increased demand together with the increased population has lessened the reserve supply and so has made artificial purification necessary. There are three chief methods of purifying water7 namely, distillation, pure filtration and the formation of a precipitate in the water, which is afterwards filtered off. Beside these there are various other methods which if prac- ticable have never been extensively applied. These include the aeration process, Electrolytic process and diiferent kinds of household lilters, some of which may yet be much used. The iirst three named7 however, are the ones which are used extensively and of which a brief descrip- tion will be given. The distillation process is the one which is used where absolutely pure water from a chemical standpoint is required. The method varies, but in the main consists of evaporating the raw water andipassing the steam through a coil which is kept cool by the surrounding water. From this the pure water passes into a reservoir. On account of the use to which this water is put, the ordinary apparatus for this method is a small still known as a whisky still, capable of producing from ten to twentwaive gallons per day. The use of this system is not nearly so extensive as that of the other sys- tems, principally on account of the expense at- tached to it. It is estimated that it costs about twelve hundred and fifty dollars per million a gallons, while by the other two processes water

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12 Our next question would probably be, cWVhat are the results to be obtained ?ll Here are a few concrete examples selected from a large number of similar ones. At the Massachusetts experi- ment station the average number of bacteria per cubic centimetre of raw water was 5621, of filtered water 21. The plant at Albany, New York, removes an average of over ninety-nine per cent of the bacteria. The average yearly death rate from typhoid feyer before the in- troduction of this system in Albany was 85, afterwards it was 39. Filtered water was first used in Hamburg in May, 1893. The number of deaths from typhoid fever per one hundred thousand population in 1891 was 23, in 1892, 34; in 1893, 18; in 1894, 6 and in 1895, 9. These figures show for themselves what was done in these few instances. Many other cases of equal value are on record. The system just described has a worthy rival in a comparatively new method known as the American filter system, since its use is prac- tically confined to America. The English sys- tem is used in Europe and in a few cities of America, but the principal objection to it, in accordance with the Yankee idea of nearly all industrial life of Europe, is that it is too slow. Briefly the system, which is the one used in our own city of Terre Haute, consists of form- ing a precipitate, by chemical means, of part of the suspended matter and this in turn gath- ers up practically all of the impurities in the water in much the same way that the white of an egg clears coffee. This is then strained 0H by running the water through a sand filter by mechanical means. The chemical used as a basis for this is common alum or better, alu- minium sulphate. This, on being added to the raw water in small quantities, about one grain per gallon, is acted upon by the carbonates found in nearly all water and decomposed. Aluminium hydrate, a white jelly-like precipi- tate is the result. This acts just as the cczoo- gloea jelly? gathering up both organic matter and bacteria. This is practically the only re- spect in which it is diiferent from the English system, because it forms its own coagulate in- THE NORMAL ADVANCE stead of waiting for the water to form it. The process is much more rapid for it works per- haps one hundred times as rapidly as the old method. The filters in use with this system are nothing more than steel or wooden tanks which have about siX feet of sand in the bottom. They are from eight to twelve feet across and from twelve to fifteen feet in height. These are placed in groups or rows so that as many of them may be used as are necessary to furnish the required amount of water. The coagulate is introduced before the water reaches the settling basin. The settling basin is nothing more than a large shallow tank into which the raw water is pumped and allowed to settle for some time be- fore flowing down to the filters. As the water is pumped into this the alum is added. This al- lows the worst part of the refuse to settle and thus lightens the work of the filter. The water in these filters is sometimes placed under pres- sure direct with the service mains. This seems to be practical for a small plant, but not for a large one. Hence, all large plants have open filters and a storage tank from which the water is pumped into the mains. The amount of alum varies with the turbidity of the water. Too large a quantity of it would probably be injurious to the health. In general the cost of the chemical prohibits this, and careful atten- tion is usually given that no more is used than is necessary. The aluminium hydrate also unites with the coloring matter in the water, and renders the product clear. The cost of installing a plant of this kind is greater than that of installing an English filter bed, on account of some expensive patents on the machinery required. The average cost of liltering the water, after the system is work- ing, is about the same as that of the other sys- tem. The relative merits of the two systems are much in doubt, as both maintain practically the same degree of efficiency at about the same cost. The two processes just mentioned are prac- tically the only ones in general use. Other methods have been devised, a few of which will be mentioned. The Anderson process sends the;