托雷斯代尔滤清器的操作
费城的Torresdale过滤厂从特拉华河接收水，并于1907年7月4日运营。最初建造的主要植物包括65 3/4英亩的宽敞床，含有26至36英寸的沙子。有效尺寸范围为0.25至0.35毫米。并且均匀性系数为2。机械类型有120个初步过滤器单元，无需使用凝结剂。这些初步过滤器已清除了60％以上。在原水中的污垢，使得慢砂过滤器的产量使能力从每天的110,000,000加仑增加到每天的210,000,000加仑。有了预先过滤的水，可以以每英亩6,000,000加仑的速度来操作慢砂床，而不是每天3,000,000张。最终床上的运行时间增加了一倍，并且通过使用预过滤器可以实质上降低过滤成本。与预先过滤器的开始几乎是一致的是尼科尔斯砂机的引入，该机器以及作为辅助机构的耙子，在托雷斯代尔（Torresdale）的所有其他清洁方法都取代了。该机器仅由封闭夹克内部的倒圆柱组成。肮脏的沙子以通常的方式喂食，洗涤水，沙子和污垢，而不是去法庭，而是通过机器。 The water strikes the side of the cylinder, the sand drops to the bottom and is allowed to pass through a nozzle and is spread on the filter. About 2 per cent, of the fine sand is carried with the water and dirt to the court, where it is intercepted. The depth of cleaning with the machine may vary from a few inches to 8 or 10 inches. The bacterial efficiency of the Torresdale plant for 1912 average 99.6 per cent. A plant such as the one at Torresdale, without any sedimentation basins, is utterly unable to cope for any prolonged period with water having a turbidity of over 100 when operating the slow-sand filters at a rate of 6,000,000 gallons per acre daily. When such a condition is reached prefilters fail to do their proportion of the work. The final filters choke badly and allow fine silt to pass through them. This choking up necessitates cleaning for 22 hours a day, with from 55 to 58 filter units doing the work of 65, and depending upon hypochloridc to reduce the number of bacteria and destroy the pathogens. Fortunately the periods of turbid water occur but seldom and are of short duration. The pre-filters should be changed and operated like the coal filters at Steelton, or a sedimentation basin should be constructed and alum used to coagulate the water. Even during the very worst period the bacterial efficiency of the Torresdale plant averages over 99.5 per cent. The filters cleaned by the Nichols methods during February, March and April have the longest runs, the length of run decreasing until about June and then remaining constant for the rest of the year. The runs with the Nichols method are longer than those obtained with any other. The average yields, in million gallons per acre, for the tour years from 1909 to 1912, inclusive, were 123, 195, 160 and 126. The longest run in the history of the plant was for 140 days, the quantity of water filtered being 569,000,000 gallons.
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