THE EAST PROVIDENCE FILTER.

THE EAST PROVIDENCE FILTER.

机械过滤可能是本身的价值ldom shown more clearly than at East Providence, R.I. Up to the end of November it had been twenty months in use, during which time the water was collected once a month and analysed under the direction of the State board of health. The initial test was from March 10 to August 2, 1899, when one grain of sulphate of alumina per gallon was used. The average removal of bacteria was 99.2 per cent. From April 1900 to November, 1901, Inclusive the bacterial results varied from 81.54 per cent. to 100 per cent.—the first occurring only once on July 6, 1900—the next lowest being 81.64 ou June 5, 1901; the second, twice, on May 1, 1901, and November 4, in the same year. On the other occasions the reductions was as high as 99.93 to 95.29. Whereas, also, the number of bacteria in the raw water was as high as 40,920 per cubic centimetre on March 6, 1901, it was reduced by filtration to 235—a reduction of 99.43 per cent., while on October 2, 1901, the reduction was from 1,426 to 1 or 99,930 percent. The color, also, which on June 5, 1901, was .95 in the raw water was .08 in the filtered—a reduction of 92 per cent, with one grain of sulphate of alumina used per gallon, and, on June 6, 1900, was reduced to .23 in the filtered water from .94 in the raw water, or 76 per cent., .075 of a grain of sulphate of alnmnia having been used. On August 7, 1901, the raw water’s color was .29; in the filtered water it was .00—a reduction of 100 per cent, with one grain of sulphate of alumina. E'rom August, 1900, to November, 1901, inclusive, one grain of sulphate of alumina being used per gallon, with an average bacterial reduction (including the low reductions of June 5 and July 3, 1901 of 99.23 per cent.) omititing these two months, it was 99 40 per cent. Between the same months (March, 1901 being omitted 40,920 bacteria per cubic centimetre in the raw water, reduced to 235, or 99.43 percent, in the filtered), the average number of bacteria per cubic centimetre was 709; in the filtered water, 10. As was shown last week by Mr. Edmund B. Weston, consulting engineer, the “average removal of color during the sixteen months that one grain of alumina per gallon was used was 90 per cent, ranging from 83 per cent, to 100 per cent.” The average bacterial reduction from April to June inclusive, when only three-fourths of a grain of sulphate of alumina was used, was 95.26 per cent. The average removal of color during the same period,and with the same amount of sulphate of alumina used per gallon, was 83 per cent., ranging from 76 to 91 per cent. The bacteriological results, therefore, where one grain of sulphate of alumina per gallon was used were very satisfactory, as the average number of bacteria in the raw water (leaving out those of March 1901) was only slightly above 700. From another point of view, also, the bacteriological results were of a high order, since in the filtered water,with one grain of sulphate of alumina used per gallon it was not above 24. and, leaving out March, 1901, only 10. It will be noticed that the amount of coagulant employed was very small—.075 of a grain for four months and one grain for the remaining sixteen. Sometimes it will run as high as five grains or even more per gallon. That amount, however, is exceptional and is used only in the case of quite turbid and highly colored water with vegetable matter, such as was not the case at East Providence, an illustration of whose filter appears elsewhere in this impression.

机械过滤可能是本身的价值ldom shown more clearly than at East Providence, R.I. Up to the end of November it had been twenty months in use, during which time the water was collected once a month and analysed under the direction of the State board of health. The initial test was from March 10 to August 2, 1899, when one grain of sulphate of alumina per gallon was used. The average removal of bacteria was 99.2 per cent. From April 1900 to November, 1901, Inclusive the bacterial results varied from 81.54 per cent. to 100 per cent.—the first occurring only once on July 6, 1900—the next lowest being 81.64 ou June 5, 1901; the second, twice, on May 1, 1901, and November 4, in the same year. On the other occasions the reductions was as high as 99.93 to 95.29. Whereas, also, the number of bacteria in the raw water was as high as 40,920 per cubic centimetre on March 6, 1901, it was reduced by filtration to 235—a reduction of 99.43 per cent., while on October 2, 1901, the reduction was from 1,426 to 1 or 99,930 percent. The color, also, which on June 5, 1901, was .95 in the raw water was .08 in the filtered—a reduction of 92 per cent, with one grain of sulphate of alumina used per gallon, and, on June 6, 1900, was reduced to .23 in the filtered water from .94 in the raw water, or 76 per cent., .075 of a grain of sulphate of alnmnia having been used. On August 7, 1901, the raw water’s color was .29; in the filtered water it was .00—a reduction of 100 per cent, with one grain of sulphate of alumina. E'rom August, 1900, to November, 1901, inclusive, one grain of sulphate of alumina being used per gallon, with an average bacterial reduction (including the low reductions of June 5 and July 3, 1901 of 99.23 per cent.) omititing these two months, it was 99 40 per cent. Between the same months (March, 1901 being omitted 40,920 bacteria per cubic centimetre in the raw water, reduced to 235, or 99.43 percent, in the filtered), the average number of bacteria per cubic centimetre was 709; in the filtered water, 10. As was shown last week by Mr. Edmund B. Weston, consulting engineer, the “average removal of color during the sixteen months that one grain of alumina per gallon was used was 90 per cent, ranging from 83 per cent, to 100 per cent.” The average bacterial reduction from April to June inclusive, when only three-fourths of a grain of sulphate of alumina was used, was 95.26 per cent. The average removal of color during the same period,and with the same amount of sulphate of alumina used per gallon, was 83 per cent., ranging from 76 to 91 per cent. The bacteriological results, therefore, where one grain of sulphate of alumina per gallon was used were very satisfactory, as the average number of bacteria in the raw water (leaving out those of March 1901) was only slightly above 700. From another point of view, also, the bacteriological results were of a high order, since in the filtered water,with one grain of sulphate of alumina used per gallon it was not above 24. and, leaving out March, 1901, only 10. It will be noticed that the amount of coagulant employed was very small—.075 of a grain for four months and one grain for the remaining sixteen. Sometimes it will run as high as five grains or even more per gallon. That amount, however, is exceptional and is used only in the case of quite turbid and highly colored water with vegetable matter, such as was not the case at East Providence, an illustration of whose filter appears elsewhere in this impression.