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 constitute 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 algæ—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.
Algæ—what are they? They are aquatic plants. Algæ are not to be confounded with the water vegetation common to the eye and passing by the term weeds. Such plants include eelgrass, 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 algæ. 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 algæ are usually grass 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 spawn" or "pond scum." 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 algæ 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 algæ led to the perfection of the copper-purification process.
It is, however, a variety of algæ 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 grass 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 algæ" (Schizophyceæ). 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 algæ 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 algæ 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—"Algæ are our worst pest"; and with one prayer—"Come over into Macedonia, and help us."
A Cheap and Available Remedy for Algæ
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 algæ 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 algæ. 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 quantities 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 spawn." After the cress was cut for market, the algæ 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 algæ 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 algæ 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 algæ 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 algæ 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 pronounced than in the laboratory. In fact, it developed that the solution necessary to kill algæ 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 quantity of copper sulphate for destroying algæ, 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. Assuming that 59° F. is the average temperature of reservoirs during the seasons when treatment is demanded, the quantity 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 quantity 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 algæ which are listed. The formulæ 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.
More important still, there is an absolute need of the services of some expert on the ground. While an algologist is a functionary not generally employed by water companies—in fact, a man trained in the physiology of algæ is difficult to find—nevertheless, it is highly important, as the department views it, to have the coöperation of an expert versed to some extent in the biological examination of drinking water. In other words, the copper cure is not a "patent medicine," with printed directions which any person could follow. Intelligence and care are absolutely essential in the use of this treatment. Furthermore, each case must be treated as a distinct and separate case, as a physician would treat a patient.
Actual Purification Simple
Suppose, however, an owner of a country place, which is dependent upon a fresh-water pond for its water supply, finds that his drinking water is contaminated, that the taste and odor are such as to render the water unfit for use. There is no reason why he should not treat the supply, provided he is properly careful. When the nature of the polluting organism is definitely determined and the average temperature of the water observed, then the necessary formula can be decided upon. First, of course, the pond must be plotted, the depth found, and the capacity computed. The department will willingly furnish data for this purpose, together with blanks upon which to submit details as to contaminating organisms and water temperature, to any applicant. Once the proper solution is determined upon, the actual work of purification is most simple. In the following directions the department outlines the most practicable method of introducing the copper sulphate into a water supply:
Directions for the Copper Cure
"Place the required number of pounds of copper sulphate in a coarse bag—gunny sack or some equally loose mesh—and, attaching this to the stern of a row-boat near the surface of the water, row slowly back and forth over the reservoir, on each trip keeping the boat within ten to twenty feet of the previous path. In this manner about a hundred pounds of copper sulphate can be distributed in one hour. By increasing the number of boats, and, in the case of deep reservoirs, hanging two or three bags to each boat, the treatment of even a large reservoir may be accomplished in from four to six hours. It is necessary, of course, to reduce as much as possible the time required for applying the copper, so that for immense supplies, with a capacity of several billion gallons, it would probably be desirable to use a launch, carrying long projecting spars to which could be attached bags containing several hundred pounds of copper sulphate.
"The substitution of wire netting for the gunny-sack bag allows a more rapid solution of the sulphate, and the time required for the introduction of the salt may thus be considerably reduced. It is best to select as warm a day for treatment as circumstances will permit."
Cost of the Treatment
Not difficult, one would say. No—when the proper solution is determined; to reach that determination is the difficulty. That the method can be tried "at home" is proved by the results obtained by the owner of a country home in the vicinity of New York. Tired of consulting engineers, who looked at his water supply, informed him that they could do nothing, and then charged him a big fee (to one he paid $250), this owner resorted to the copper-sulphate treatment. The cure cost the man just $2—but let his letter to the department tell the story:
"My place in the country is located at Water Mill, in the township of Southampton, in Long Island. I purchased it in April, 1902, and was largely influenced in selecting this piece of land by the beauty of a pond which bounds it on the east. This little body of water covers about two acres, is fed by numerous springs, and discharges into Mecox Bay, the southern boundary of the land. When I bought the place the pond was filled with clear water. About the middle of the following June algæ began to show, and in August the surface was almost entirely covered by the growth. The odor was offensive, and myriads of small insects hovered over the masses of algæ much of the time. I consulted two engineers interested in the storage of water, and they told me that nothing could be done. The condition was so objectionable that I planned to plant a thick hedge of willows along the bank to shut off the view of the pond from the house.... I examined the pond on June 15th and found large masses of algæ covering an area several hundred feet in length and from twenty to forty feet in width. No microscopical examination was made of the growth, but I was informed that it seemed to be largely composed of filaments of Spirogyra and other Confervæ. On June 18th the treatment was begun.... In one week the growth had sunk and the pond was clear water. I examined the pond September 15th and found it still clear.
"The use of the sulphate of copper converted an offensive insect-breeding pond into a body of beautifully clear water. The pond was full of fish, but the copper did not seem to harm them."
Effect of Copper Sulphate on Fish
Native trout were not injured when the large reservoir at Cambridge, N. Y., was purified by the copper treatment. A slightly different result, in this respect, was reported from Elmira, N. Y., however. Part of the report is as follows:
"The effect of the copper-sulphate treatment on the different animal life was as follows: numerous 'pollywogs' killed, but no frogs; numerous small (less than two inches long) black bass and two large ones (eight inches long) killed; about ten large 'bullheads' were killed, but no small ones; numerous small (less than two inches long) 'sunfish' were killed, but no large ones.
"The wind brought the dead fish to the corners of the reservoir, and it was very little trouble to remove them. No dead fish were seen twenty-four hours after completion of the treatment."
The injury done by copper sulphate to fish is a more serious matter than was at first supposed. Brook trout are, apparently, the least resistant to the salt. A Massachusetts trout pond stocked with eight-inch trout lost forty per cent as a result of the introduction of a strong solution of copper sulphate. The Bureau of Fisheries is working in conjunction with the Division of Plant Physiology in this matter, and it is hoped to secure reliable information. In the meantime, owners of ponds stocked with game fish would do well to take great care before resorting to the copper cure for algæ—that is, if they hesitate to lose a part of the fish.
Water May be Drunk During Treatment
When a pond or reservoir is treated with the proper amount of copper sulphate to remove algæ—except in the case of the few very resistant forms requiring a stronger solution than 1 part of copper to 1,000,000 parts of water—there is no need of discontinuing the use of the water supply during treatment; the water may be drunk with impunity. But when water known to be polluted with pathogenic bacteria is sterilized by means of copper sulphate in strong solution, it is just as well to discontinue the use of the water for drinking purposes for not more than twenty-four hours. Even then, this is an overcareful precaution rather than a necessity.
Experiments conducted with great care and thoroughness demonstrate that at room temperature, which is near the temperature of a reservoir in summer, a solution of 1 part of copper to 100,000 parts of water will destroy typhoid bacteria in from three to five hours. Similar experiments have proved that a copper solution of like strength is fatal to cholera germs in three hours, provided the temperature is above 20° F. As was the case with algæ, bacteria were found to be much more sensitive to copper when polluting water than when grown in artificial media.
The Use of Copper Tanks
The toxic effect of metallic copper upon typhoid bacteria in water gives some hints as to prevention of the disease by the use of copper tanks. This should not altogether take the place of the boiling of the water; it is useful in keeping it free from contamination, although water allowed to stand in copper receptacles for a period of from twenty-four to forty-eight hours at room temperature would be effectively sterilized, no matter what its contamination and no matter how much matter it held in suspension. But in order to insure such results the copper must be kept thoroughly clean. This polishing is not, as was popularly supposed, to protect the consumer from "copper poisoning," but to prevent the metal from becoming so coated with foreign substances that there is no contact of the copper with the water, hence no antiseptic quality.
Dr. Henry Kreamer, of Philadelphia, proved that within four hours typhoid germs were completely destroyed by the introduction into the polluted water of copper foil.
"Granting the efficiency of the boiling of water for domestic purposes, I believe that the copper-treated water is more natural and more healthful.... The intestinal bacteria, like colon and typhoid, are completely destroyed by placing clean copper foil in the water containing them.
"Pending the introduction of the copper treatment of water on a large scale, the householder may avail himself of a method for the purification of drinking water by the use of strips of copper foil about three and one-half inches square to each quart of water, this being allowed to stand overnight, or from six to eight hours at the ordinary temperature, and then the water drawn off or the copper foil removed."
Although a splendid antiseptic, copper in weak solution is not harmful, no more so than the old copper utensils used by our forefathers were harmful. Undoubtedly they were of benefit, and the use of them prevented the growth of typhoid and other bacteria. People of to-day might well go back to copper receptacles for drinking water.
FOOTNOTES:
[1] For published reports of the work, see Bulletins 64 and 76, Bureau of Plant Industry, U. S. Department of Agriculture; reports prepared by Dr. George T. Moore and his assistant, Mr. Karl F. Kellerman.
[2] See Bulletin No. 76, supra.