Sewage disposal . Fig. 36. Plan of Worcester Chemical Precipitation Plant. the basins, the water is drawn off by means of floating arms, andthe sludge allowed to flow by gravity, each basin containing acentral sludge channel, to the sump well (P). From the sumpwell it is pumped to the storage tank (MM) by means of aShone ejector, and 30 to 50 lbs. of lime in the form of milk of lime TREATMENT OF SEWAGE AT WORCESTER, MASS. 127 are added. The sludge is allowed to settle in the storage tanksand the clear liquid, 15 to 25 per cent of the total volume of thesludge, is drawn off on to sand filter be
Sewage disposal . Fig. 36. Plan of Worcester Chemical Precipitation Plant. the basins, the water is drawn off by means of floating arms, andthe sludge allowed to flow by gravity, each basin containing acentral sludge channel, to the sump well (P). From the sumpwell it is pumped to the storage tank (MM) by means of aShone ejector, and 30 to 50 lbs. of lime in the form of milk of lime TREATMENT OF SEWAGE AT WORCESTER, MASS. 127 are added. The sludge is allowed to settle in the storage tanksand the clear liquid, 15 to 25 per cent of the total volume of thesludge, is drawn off on to sand filter storage tanks are provided with vertical bar screens (L). Fig. 37. Birds-eye view of Worcester Chemical Precipitation Plant. with half-inch openings, and the screened sludge is pumped bypower plunger pumps into the filter presses under 80 poundspressure per square inch. The liquor is conducted to sand filter beds, and the sludgecake, containing 70 per cent water, is hauled by motor cars toan isolated valley three-quarters of a mile from the press house. The removal of the suspended organic matter by the aboveprocess, measured by albuminoid nitrogen, has in the past aver-aged about 85 to 90 per cent, which is roughly 50 per cent of thetotal organic matter in the sewage; but in 1916 the purificationamounted only to 71 per cent of the suspended, or 38 per cent ofthe total nitrogen, on account of a great excess of iron sulphate inthe sewage and a shortage of lime. The cost of chemical treat-ment in 1916 was $ per million gallons and the cost of sludgepressing $ per million gallons. The sewage to be purified by intermittent filtration, 5
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisherlondo, bookyear1919
