Volume 2

Report on water supply and sewerage.

  • Massachusetts. State Board of Health.
Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: Report on water supply and sewerage. Source: Wellcome Collection.

    22/964 (page 8)
    sewage or in the material of which some filters were composed, and, when existing with the other conditions favorable for producing nitrification, large quantities of organic matter could be converted into inorganic and mineral matter. The relations of space occupied by sand, liquid and air, in the example just given of intermittent filtration, obtain only in a coarse sand of quite even grain. In such a sand air may be found, in nearly the quantity indicated, many feet below the surface; and sometimes the application of sewage over the whole surface will force air out through the underdrains at the depth of five or six feet; and a few hours after the application air may move freely through the sand from the underdrains to the surface. These relations differ widely in sands of finer grain and with mixed sands. In some, though completely underdrained, liquid will be held in the lower two feet of a five-feet layer, filling all of the space between the particles of sand, keeping this depth entirely saturated, while the upper three feet in depth may contain from one to two times as much air as water. Still finer material may* remain saturated throughout its whole depth, and give space for air only near the surface, after standing long enough for the liquid there to be evaporated. A few careful series of experiments have been made in laboratories abroad, giving varying and sometimes astonishing results of the purification of sewage by filtration.* But previous to the investiga- tions here presented very little was definitely known anywhere of the conditions most favorable for the purification of sewage by any given material. Whether it would purify at all, and, if at all, how much sewage could be applied, and what periods of intermission were necessary for obtaining a desired quality of effluent, and whether and under what conditions disease-producing germs could be removed, were questions which, at the beginning of these investi- gations, could be determined only by the resulting purification obtained by experiment; that is, by applying sewage through the different seasons of the year, in varying quantities, and with vary- ing periods of intermission, to considerable areas of the various classes of material found in our valleys. The Experiment Station at Lawrence has been arranged, and the experiments have been conducted, for the purpose of determining * For a more detailed account of those experiments, and a general statement of the results of irrigation and of intermittent filtration in purifying sewage up to the time of beginning these investigations, see nineteenth annual report of the State Board of Health of Massachusetts, pp. 37-41.