Excerpt from The Sanitary Significance of Bacteria in the Air of Drains and Sewers

Ummotwbwmhhmfiiem bird-nu. Wmmmmmmmwmin the stream to efiect the union. Under such condition there results a self purification of a very satisfactory type, as far as the chemical constituents are concerned. Disease bacteria on the other hand, although they do die out in water, decrease slowly and uncertainly, so that bacterial self-purifica tion cannot be relied on to make polluted water potable. Even chemical self-purification has its rather narrow limits. The fate of the sewage changes entirely when its volume exceeds the maximum which may be absorbed by a given stream, roughly stated as one part of sewage to fifty parts of water. When that limit is exceeded, when the limit of available oxygen for the oxidation of organic matter is passed, then the conditions of putrefaction are set up. It is like Mr. Micawber's philosophy: Annual income twenty pounds, annual expenditures nineteen ought and six, result happiness. Annual income twenty pounds, annual expenditures twenty pounds ought and six, result misery. Up to a certain point everything goes well, but beyond that point, conditions are totally changed and ih stead of a self-purifying stream you find a foul septic tank. Dilution then the discharge of sewage into water - is limited by the volume of sewage in relation to the body of water into which it is to discharge. On the sea coast the conditions for purification by dilution are ideal; and with large rivers like the Mississippi this method may be followed very satisfactorily. In smaller streams we get the septic tank condition of which I have spoken. In Massachusetts alone there are at least seven rivers so polluted as to become a public nuisance for a part of their course. Most serious of all, when such a condition as this is reached, there is often so deep a deposit of decomposing sludge in the bed of the stream that after the removal of all fresh pollution it remains as foul and unsightly as before. Nothing but expensive dredging operations will suffice to restore a stream so desecrated to its pristine purity. I beg you to take warning from our more thickly settled commonwealth and avoid while you may such problems as we now find before us in the Neponset and the Blackstone rivers.

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