The Home Medical Library Volume V Part 3

_An Ideal System for a Country House_

Still another system using pressure tanks is more complete than either of the others, comprising engine, pump, air compressor, a water tank, and also an air tank. It is best described by a recent example constructed from plans and under the direction of the writer. The buildings supplied with water comprise the mansion, the stable, the cottage, and a dairy, and the pumping station is placed near the sh.o.r.e of the lake from which the supply is taken. See Figs. 1 and 2.

[Ill.u.s.tration: FIG. 1.

DIAGRAM OF COMPRESSED AIR TANK SYSTEM.]

[Ill.u.s.tration: FIG. 2.

PRESSURE-TANK PUMPING STATION.

Interior view of pumping station of compressed air-tank system (see plan on opposite page) showing 3,000 gallon water tank, air tank of 150 pounds pressure and 10 horse-power gasoline engine.]

The pump house is about 20 feet by 27 feet, and contains a water-storage tank 6 feet in diameter and 13-1/2 feet long, of a capacity of 3,000 gallons; an air tank of same dimensions as the water tank, holding air under 150 pounds pressure; a 10 horse-power gasoline engine, direct-connected, by means of friction clutch, with an air compressor and also with a triplex pump of 75 gallons capacity per minute.

The water in the tank is kept under 75 pounds pressure, and at the hydrant near the house, located about 100 feet above the pumping station, there is an available pressure of 33 pounds. The last drop of water flows from the water tank under the full pressure of 75 pounds at the pumping station. The suction pipe into the lake is 4 inches and is provided with well strainers to prevent clogging.

The cost of pumping water by this system is quite reasonable. The gasoline engine requires per horse-power per hour about 1-1/4 gallons of gasoline, and at sixteen cents per gallon this makes the cost for 1,000 gallons pumped about five cents. To this expense should, however, be added the cost of lubricating oil, repairs, amount for depreciation, and the small cost for labor in running the engine.

Water pipes forming a distribution system should always be chosen generous in diameter, in order to avoid undue loss of pressure by friction. Where fire hydrants are provided, the size of the water main should not be below four inches. All branches should be controlled by shut-offs, for which the full-way gate valves are used in preference to globe valves. Pipe-line material is usually galvanized, screw-jointed wrought iron for sizes up to four inches.

In conclusion, a word about water purification. Where the quality of the water supply is not above suspicion it may be improved by filtration. A filter should never be installed without the advice of a qualified expert, for there are numerous worthless devices and few really efficient ones. Where a filter is not available, the water used for drinking should be boiled or sterilized if there is the slightest doubt as to its wholesomeness.

CHAPTER III

=Purifying Water by Copper Sulphate=

From the standpoint of the health of the community, the most vital problem is to get pure water. Almost equally important, when comfort and peace of mind is considered, is the procuring of sweet water. The wise owner of a country home looks to the water supply upon which his family is dependent. The careful farmer is particular about the water his stock, as well as his family, must drink. But careless persons const.i.tute the large majority. Most people in the city and in the country pay no attention to their drinking water so long as it "tastes all right."

_Clear Water Often Dangerous_

Some years ago the inhabitants of Ithaca, N. Y., furnished a pitiful example of this foolhardy spirit. For a year previous to the breaking out of the typhoid epidemic, the public was warned, through the local and the metropolitan press, of the dangerous condition of Ithaca's water supply. Professors of Cornell College joined in these warnings.

But the people gave no heed, probably because the water was _clear_ and its taste sweet and agreeable. As was the case in this instance, bacteria are tolerated indefinitely, and it is only an alarming increase in the death rate that makes people careful. Then they begin to boil the water--when it is too late for some of them.

_Bad-Tasting Water not Always Poisonous_

But let the taste become bad and the odor repulsive, and a scare is easily started. "There must be dead things in the water, or it wouldn't taste so horrible," is the common verdict. Some newspaper seizes upon the trouble and makes of it a sensation. The ubiquitous reporter writes of one of "the animals" that it "looks like a wagon wheel and tastes like a fish." With such a remarkable organism contaminating one's drink no wonder there is fear of some dread disease. The water is believed to be full of "germs"; whereas the pollution is entirely due to the presence of algae--never poisonous to mankind, in some cases acting as purifying agents, but at certain seasons of the year imparting a taste and odor to the water that cannot be tolerated.

Algae--what are they? They are aquatic plants. Algae are not to be confounded with the water vegetation common to the eye and pa.s.sing by the term weeds. Such plants include eelgra.s.s, pickerel weed, water plantain, and "duckmeat"--all of which have roots and produce flowers.

This vegetation does not lend a bad odor or taste to the water. In itself it is harmless, although it sometimes affords a refuge for organisms of a virulent type.

But when the aquatic vegetation of the flowering variety is eliminated from consideration, there still remains a group of water plants called algae. They comprise one-fifth of the known flowerless plants. They are the ancestors of the entire vegetable kingdom. Those whose habitat is the sea number the largest plants known in nature. Certain forms found in the Pacific are supposed to be 800 feet in length; others are reported to be 1,500 feet long. The marine variety are familiar as the brown kelps and the wracks, which are very common along our Northern coast.

_Plants Which Pollute Drinking Water_

The fresh-water algae are usually gra.s.s green in color. This green variety is often seen as a spongy coating to the surface of stagnant pools, which goes by the name of "frog sp.a.w.n" or "pond sc.u.m." One of this description, _Spirogyra_, has done thousands of dollars' worth of damage by smothering the life out of young water-cress plants in artificial beds constructed for winter propagation. When the cress is cut the plants are necessarily left in a weakened condition, and the algae form a thick mat over the surface of the water, thus preventing the growth of the cress plants and oftentimes killing them. The absolute necessity of exterminating these algae led to the perfection of the copper-purification process.

It is, however, a variety of algae not easily detected that contaminates the water. So long as they are in a live, healthy condition they benefit drinking water by purifying it. Indeed, some scientists have attributed the so-called self-purification of a stream entirely to the activities of these plants. Of such, one form, _Chlamydomonas_, is bright gra.s.s green in appearance. But the largest group--the plants which have the worst reputation as polluters of drinking water--are popularly known as the "blue-green algae"

(_Schizophyceae_). The common name tells the color of these plants, although there are exceptions in this respect, some of them showing shades of yellow, brown, olive, chocolate, and purplish red. This variety of algae flourishes in the summer months, since a relatively high temperature and shallow stagnant water favor its germination. If the pond begins to dry up, the death of the organisms takes place, and the result is a most disagreeable, persistent odor which renders the water unfit for drinking purposes. This result is chemically due to the breaking down of highly organized compounds of sulphur and phosphorus in the presence of the large amount of nitrogen contained in these plants. Decomposition is not necessary for some of the blue greens to give off a bad odor, however. A number of them, on account of their oil-content, produce an odor when in a healthy condition that is sometimes likened to raw green corn or to nasturtiums, but usually it cannot be so pleasantly described.

The Department of Agriculture has been able to solve the problem of exterminating algae from water supplies.[1] The department has done more; for it has succeeded in perfecting a method by which a reservoir contaminated with typhoid or other pathogenic bacteria can be purified. The work was begun with an inquiry into the extent of the trouble from algal pollution. Letters were addressed to some five hundred engineers and superintendents of water companies scattered all over the United States. The replies, which came from almost every State in the Union, were burdened with one complaint--"Algae are our worst pest"; and with one prayer--"Come over into Macedonia, and help us."

_A Cheap and Available Remedy for Algae_

Convinced of the need of earnest work, extensive laboratory experiments were inaugurated. The problem presented was this: the remedy must not only be readily available, but it must be cheap, that advantage may be taken of it by the poorest communities, as well as by those owning large reservoirs. Above all, the remedy must be absolutely harmless to man; the poison used to exterminate algae must not in any way affect the water drinkers. A large number of substances were used in the experiments before the final decision rested with copper sulphate. This salt is very poisonous to algae. On the other hand, copper in solution just strong enough to destroy algal growth could not possibly injure man; in fact, the temporary presence of such a small amount of copper in drinking water could not be detected.

_A Practical Demonstration_

The results in the laboratory being successful, the next step was to make a practical demonstration of the value of the method. This was first done in the fall of 1901. At Ben, Va., water cress is grown in large quant.i.ties during the winter, when it is a valuable market crop.

Dams are constructed across a stream in such a manner as to enable the maintenance of a water level not too high for the growth of plants; when a freeze is threatened the plants can be flooded. In the cress beds selected for the experiments the water is obtained from a thermal spring whose temperature throughout the year is about 70 F. This temperature is particularly favorable to the growth of "frog sp.a.w.n."

After the cress was cut for market, the algae frequently developed so rapidly as to smother the life out of the weakened plants. When this occurred, the practice was to rake out both water cress and algae and reset the entire bed. This was not only expensive; half the time it failed to exterminate the pest. It was, therefore, most desirable to devise a method of ridding the bed of algal growth without injuring the cress.

_The Copper-sulphate Method Tested_

Here the copper-sulphate method was put to a practical test. At the outset a strong solution was sprayed on the algae which coated the surface of the pond. This only killed the algal growth with which the particles of copper came in contact and left the main body of algae unaffected. Then trial was made of dissolving the copper directly in the water, and the result was most satisfactory. The solution used was that of 1 part of copper to 50,000,000 parts of water.

Growers need have no trouble in the future. They need have no fear of employing the method, as the copper solution required for killing the algae could not possibly injure water cress, provided ordinary care is used in the work. As to the frequency of treatment required, one or two applications a year will generally be found sufficient, as this letter, received from the manager of the Virginia company, goes to show:

"The 'moss' has given me no trouble at all this winter; in fact, I have for six months had to resort to the copper sulphate only once....

All the conditions were favorable last fall and early winter for a riot of 'moss,' but it did not appear at all until just a few days ago, and then yielded to treatment much more readily than it did when I first began to use the copper." This letter was written over three years after Dr. Moore made his experiment in these cress beds.

Satisfied with the results attained in exterminating algal growth in water-cress beds, attention was next given to reservoirs. Some fifty water supplies were treated during the summer of 1904, and in every case success attended the copper cure. In one respect the results were surprising. It was found that in practice the copper-sulphate method worked better than in theoretic experimentation; results in large reservoirs were more p.r.o.nounced than in the laboratory. In fact, it developed that the solution necessary to kill algae in the laboratory must contain from five to twenty times as much copper as that contained in a solution which will exterminate algal growth in its natural habitat. This is not easily explained, if it can be explained at all. The test reason advanced is that only the most resistant organisms stand transplanting to an artificial environment. But, after all, the important point is that the new method works better in practice than was expected.

_A Prescription for the Copper Cure_

Thus the department is able to announce that the process is no longer in the experimental stage, and also to say what conditions must be known in determining the proper quant.i.ty of copper sulphate for destroying algae, together with a prescription for the copper cure.

Here it is, for the benefit of careful persons who will use the method with proper intelligence: "The importance of knowing the temperature of the contaminated water is second only to the necessity of knowing the organism present. With increase of temperature the toxicity of a given dilution increases, and _vice versa_. a.s.suming that 59 F. is the average temperature of reservoirs during the seasons when treatment is demanded, the quant.i.ty of copper should be increased or decreased approximately 2.5 per cent for each degree below or above 59 F.

"Similar scales should be arranged for the organic content and the temporary hardness of the water. With the limited data at hand it is impracticable to determine these figures, but an increase of 2 per cent in the quant.i.ty of copper for each part per 100,000 of organic matter and an increase of 0.5 to 5 per cent in the proportion of copper for each part per 100,000 of temporary hardness will possibly be found correct. The proper variation in the increase due to hardness will depend upon the amount of dissolved carbon dioxide; if very small, 5 per cent increase is desirable; if large, 0.5 per cent is sufficient."

The information in this prescription is to be used in connection with a table[2] published by the Department of Agriculture. This table gives the number of parts of water to one part of copper sulphate necessary to kill the various forms of algae which are listed. The formulae vary from 1 part of copper to 100,000 parts of water, necessary to destroy the most resistant and very rare forms (three of these are listed), to 1 part of copper in 25,000,000 parts of water, which is a sufficiently strong solution to exterminate _Spirogyra_, the cress-bed pest. By far the majority of forms do not require a solution stronger than that of 1 part of copper to 1,000,000 parts of water.

_What the Agricultural Department is Doing_

It is true that the department is not now holding out, directly, a helping hand to the owner of a country place, or to the farmer, in this campaign of purifying drinking water. In the first place, the greatest good of the greatest number demands that large reservoirs, which supply a great number of people with drinking water, ought to be considered first. Such supplies, moreover, are most frequently contaminated. Where fifty reservoirs were treated last summer, ten times that number will be "cured" this summer. It will be readily seen, therefore, that in conducting such a large number of experiments--considering preliminary reports, prescribing for treatment, and keeping proper account of results--the department, with a limited force and limited facilities, has its hands more than full.