Dr. H. A. Elliot, Barnet. This matter of filtration of water, gentlemen, is a thing that has never engaged my attention in the least; having been living in a town which has, I believe the best record for pure water, according to analysis, so that I never have looked up the matter very much, but I am convinced from the very able papers this afternoon, that we have polluted water, and I am sure we have had some experience in a neighboring town. When a member of my family goes to that town, he takes a vial of pure water, and by wrapping paper around it, he can carry it along, and take a swig from that when he is thirsty, and people would think it was coffee. I refer to St. Johnsbury. We have polluted water supplies, and I gather from what the able men have said this afternoon, that filtration is a practical method of purifying such water. I heartily agree with Professor Votey that in case this method is installed, it must be looked after scientifically, otherwise it becomes worse than useless. I am sure in some places in Vermont, good water can be obtained without using filtered water. I hope in most cases it can be done. Perhaps in the larger cities this would not be possible. Dr. Caverly. The secretary has just received a paper from Dr. Doty of New York on this important and recent work in connection with the purification of water by the use of copper, and we will ask him to read it. Dr. Holton. The state board of Massachusetts have been experimenting with this matter of using copper to purify water, and what would be the effect upon the water afterward, and they are now preparing a statement in regard to the experiments. This board knew that Dr. Doty had given considerable time and attention to this and installed systems and made experiments in reference to it, and on seeing him two months ago, he said he would come and try and discuss this subject unless something prevented. I received a telegram from him that a ship had just come in from South America, and with it a case of yellow fever, and he didn't dare to leave the city, as he feared there might be more, but would send his paper on the subject. THE USE OF COPPER IN THE PURIFICATION OF WATER. BY ALVAH H. Dory, M. D., QUARANTINE, STAten Island, N. Y. The purification of water supplies is an exceedingly important and frequently a very difficult problem for consideration on the part of public health officers. Practically it relates first, to the removal of the offensive odor and taste which frequently occur in reservoir water, and which is as a rule due to the presence of a vegetable growth known as algæ. This is usually described as having a fishy odor and smell and often erroneously attributed to the presence of dead fish. The most expensive and drastic means are often taken to remove this unpleasant condition even to the extent of rebuilding old reservoirs or constructing new ones. Second, the purification of drinking water relates to the destruction of pathogenic organisms which are presumed to be present in reservoirs. The investigation of Dr. George T. Moore, of the United States department of agriculture, has shown that minute doses of sulphate of copper if properly distributed in the water will destroy the algæ, clarify the water and remove the offensive taste and odor caused by the presence of this growth. Those who have not had actual experience in this direction will hardly appreciate the great value as well as the simplicity of this method, which constitutes an exceedingly important and practical contribution to the subject of water purification. Dr. Moore's conclusions are that copper even in very minute doses has a toxic effect on the algal growth and precipitates it. He recommends for this purpose sulphate of copper in the strength of from one to one million or even in smaller proportions. When employed for this purpose the copper should be placed in a bag made of some coarse and rather loose texture such as coffee sacking, etc., and attached to a cord which is fastened to the stern of a small boat, or held in the hand of the operator, while the boat is slowly propelled about the reservoir until the copper is entirely dissolved. It is essential that the bag be held not too far below the surface of the water and the copper so far as possible be evenly distributed. Inasmuch as the algal growth includes small sac containing an offensive oil, and as the copper tends to rupture these sacs, the offensive odor and taste of the water is at first increased, but exceedingly satisfactory results are quite sure to follow in three or four days. In connection with this subject it is necessary to consider how far or to what extent sulphate of copper can be employed in the manner above described without injury to those using the water. If it is on the basis of one to one million parts of water, it would amount to about one pound of sulphate of copper, apothecaries weight (i, e. twelve ounces of 480 grains each) for every 100,000 gallons of water in the reservoir. I am satisfied that this proportion in drinking water need receive no serious consideration inasmuch as the use of one pound of copper to 100,000 gallons of water con stitutes only about one grain of copper to every sixteen gallons of water, and as a person does not ordinarily drink more than a gallon of water in twenty-four hours, there would be only one-sixteenth of a grain taken during that period. This amount would only be present provided the copper remained in solution in the water. As a matter of fact it does not, as immediately after the introduction of the copper it forms a mechanical and chemical combination with organic and other matter in the water and is precipitated. In my own experiments with copper, I have found that where much larger amounts were used (five to twelve grains for each gallon of water experimented with) no trace of it could be found in the water at the end of twenty-four hours after a careful chemical examination. Therefore, I believe that copper in minute doses, as Dr. Moore suggests, for the removal of the offensive odor and taste in reservoir water, usually due to the presence of algæ is absolutely harmless and is followed by the most satisfactory results. I do not believe however that sulphate of copper can safely be depended upon for the disinfection of reservoir water presumed to contain pathogenic organisms particularly the typhoid bacilli. As a matter of fact there are but few instances recorded where typhoid bacilli have been detected in drinking water. An abrupt and general outbreak of this disease in a community and in the absence of some known cause for it, justifies us in suspecting that the water supply if a common one is responsible for the outbreak, although the organism cannot be found in the water. Unfortunately laboratory experiments cannot accurately determine the value of sulphate of copper in the disinfection of reservoir water inasmuch as in the latter we are dealing with factors which are not present in experimental work; for instance, the uncertainty as to the exact character of the media which presumably contains the organism. Reservoirs are constantly receiving water which is not always of a certain standard and there is a constant variation in the amount of organic and other matter. This alone would tend to show that the value of copper in the disinfection of reservoir water in the manner already referred to is at least questionable as we are dealing with copper in exceedingly minute doses, which probably is promptly neutralized and rendered useless by the different constituents of the water. As the result of my own experiments made with typhoid bacilli in distilled water, tap water, sewer water and broth, it was very soon apparent that the germicidal value of sulphate of copper diminished as the organic matter increased. The danger of employing sulphate of copper for the disinfection of reservoir water in the presence of typhoid fever, lies in the fact that it would probably be depended upon to destroy all organisms present; possibly nothing further would be done. Whereas, our first duty should be to discover the origin of infection. We know this is probably not in the reservoir, but in one of its tributaries. The most exhaustive inspection is often necessary to determine the origin which is frequently due to the presence of mild, ambulant or unrecognized cases, which have escaped detection or have been mistaken for some other disease. Until we have discovered this or have made every effort to do so, we have not as health officials fulfilled our duty to the public. After the origin of infection has been discovered and isolation, quarantine, disinfection, etc., have been carried out the treatment of the reservoir water should be given proper attention; at this time the use of sulphate of copper may be considered. However, I am certain that it cannot be depended upon to destroy the pathogenic organisms presumed to be present in reservoir water and to prevent the transmission of infectious disease. I believe that other means to obtain this result are imperative. My experiments with sulphate of copper, alone, and in combination with lime, have produced some very interesting results particularly as to the value of these agents as a deodorant. The experiments referred to, which were published in the New York Medical Record, January 21, 1905, showed that although copper and lime used alone were efficient deodorants, the results were far more pronounced when used in combination in the proportion of one pound of sulphate of copper (blue vitrol) and one pound of calcium oxide, commonly known as "rock or unslaked lime," to ten gallons of water. The results obtained by the use of this mixture in deodorizing decomposed organic matter, offensive vaults, cess-pools, garbage heaps, etc., showed it to be the most valuable and practical deodorant which we possess for these purposes. One gallon of this mixture was sufficient to deodorize at least twenty-five or thirty gallons of offensive fluid. Its action is rapid and permanent, it is practically harmless, cheap and easily made. In preparing the mixture, it is advisable to first dissolve the copper by placing it in a bag made of some coarse material and suspend it just below the surface of the water; in this way it is dissolved much more rapidly than when the copper is thrown to the bottom of the receptacle and stirred. Six or eight gallons of water may be used to dissolve the copper leaving the remainder of the ten gallons of water to prepare the lime, which is done by placing the latter dry, in a pail, or other receptacle and gradually adding water and stirring until the "steaming," or "slaking" is completed. The copper and lime may then be mixed together; a precipitate takes place, and therefore stirring is always necessary before using the stock solution. In a well covered receptacle this may be kept indefinitely. Dr. Holton. You will find an article on this subject in the Medical Record of January 21, last. This seems to me a matter of great importance. I had a long talk a few weeks ago with Dr. Moore, and he cited many instances where this method of purification has been used within the last two years, with no unpleasant effect. He said that he was not prepared to say that it would destroy pathogenic organisms. The proportion used is, one pound of blue vitrol to about ten million gallons of water. I think Dr. Stone, the director of the Laboratory has made some original experiments very much in line with those experiments of Dr. Doty's, and I think he would allow us to call on him. |