Engineers and Engineering Volume 26

Engineers and Engineering Volume 26

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1909 edition. Excerpt: ...of sand layer is maintained for all runs. I think that this feature is important, for the efficiency is not entirely due to the work done by the top layer or "Schmutzdecke," but also to the sand below it. There is an advantage in addition to this: if for any cause the "Schmutzdecke" is broken, it is more probable that a thick bed will retain the bacteria than a thin one. In any comparison of Philadelphia, with, say, 25 deaths per 100,000 per annum, which is a fairly high estimate, it must be borne in mind that filtered water was not supplied to the entire city until March 1st, so the cases contracted during the first two months of the year will increase the deaths for 1909. For a fair comparison of a year's run with filtered water the record of deaths should run from May 1, 1909, to May 1, 1910, during which period I think the rate will not be over 20 per 100,000. With reference to the possible contamination of the water through leakage into the Torresdale conduit, I might say that I was one of the men sent into the conduit to find how much contamination was getting in. We sampled all the leaks and tested them bacteriologically, and in almost every case the water had a very low count. The water after filtering through the soil above the conduit was almost sterile. After the Torresdale plant had been in operation for six months, I compared results from the filtered water basin with those from Lardner's Point Pumping Station at the lower end of the conduit, and found that, averaging the first six months' run, the water was practically the same at both places. It is my opinion that if there are any leaks they are outward and not inward. The volume in the conduit is displaced twenty-five times a day. The infiltration would...show more

Product details

  • Paperback | 98 pages
  • 189 x 246 x 5mm | 191g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236993535
  • 9781236993533