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Página 67 - Thus, whether we examine the organic pollution of a river at different points of its flow, or the rate of disappearance of the organic matter of sewage when the latter is mixed with fresh water and violently agitated in contact with air, or finally the rate at which dissolved oxygen disappears in water polluted with 5 per cent, of sewage, we are led in each case to the inevitable conclusion that the oxidation of the organic matter in sewage...
Página 69 - if sewage-matter be mixed with twenty times its bulk of ordinary river-water, and flow a dozen miles, there is not a particle of that sewage to be discovered by chemical means"; secondly, because of the feeling that to be in any way prejudicial to health, a water must contain enough animal matter to be recognized readily by chemical tests, — enough, in fact, to be expressed in figures. The first of these opinions has been disproved by the experiments of the Rivers Commission, in England, who have...
Página 67 - ... we are led in each case to the inevitable conclusion that the oxidation of the organic matter in sewage proceeds with extreme slowness even when the sewage is mixed with a large volume of unpolluted water, and that it is impossible to say how far such water must flow before the sewage matter becomes thoroughly oxidized. It will be safe to infer, however, from the above results, that there is no river in the United Kingdom long enough to effect the destruction of sewage by oxidation.
Página 68 - I should say, that it is simply impossible, that the oxidizing power acting on sewage, running in mixture with water over a distance of any length, is sufficient to remove its noxious quality. I presume that the sewage can only come in contact with oxygen from the oxygen contained in the water, and also from the oxygen on the surface of the water ; and we are aware that ordinary oxygen does not exercise any rapidly oxidizing power on organic matter. I believe that an infinitessimally small quantity...
Página 70 - A part has been converted into gaseous products of decomposition as the offensive odors observed during the decay will testify, but another portion has been carried off by the stream as soluble nitrogenous organic matter. This nitrogenous matter would be detected a short distance away with greater or less ease according to the volume of water present, and in a stream of large size or in a lake, at no very great distance from the source of contamination, it would be impossible to discover any offensive...
Página 68 - I believe that an infinitesimally small quantity of decaying matter is able to produce an injurious effect upon health. Therefore, if a large proportion of organic matter was removed by the process of oxidation, the quantity left might be quite sufficient to be injurious to health. With regard to the oxidation, we know that to destroy organic matter the most powerful oxidizing agents are required ; we must boil it with nitric acid and chloric acid and the most perfect chemical agents. To think to...
Página 67 - It is evident, that so far from sewage mixed with twenty times its volume of water being oxidized during a flow of ten or twelve miles, scarcely two-thirds of it would be sO destroyed in a flow of 168 miles at the rate of one mile per hour, or after the lapse of a week.
Página 86 - With our present knowledge we have no evidence that sand nltration can be regarded as an efficient means of purification of polluted water; although it may, if properly carried out, lessen the liability of ill effects. 3. All visible suspended particles, and an appreciable proportion of organic matter actually in solution, may be removed by properly conducted filtration through sand. 4. For the present, at any rate, it will be best to regard artificial filtration mainly as a means for the removal...
Página 30 - A water suitable for domestic supply must be free from all substances which are known to produce an injurious effect on the human system, or which are suspected with good reason or on good authority to produce such an effect. 2. The water should be, as far as practicable, free from all substances and from all associations which offend the general aesthetic sense of the community, and thus affect the system through the imagination, even if there is good reason to suppose that it is in itself perfectly...
Página 73 - ... been found that these organisms retain their vitality in spite of very varied conditions, and through very considerable changes of temperature. One would not assert that the drainage from a single house would contaminate the water of a large river like the Merrimack so as to make it unfit for domestic use, yet we must beware how we depreciate the effect of sewagematter, even in a large stream.

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