These tests were made by the author of a set of Jewell filters at Lorain, Ohio. The filters were six in number, each 17 feet in diameter, having an effective filtering area of 226 square feet each, or 1356 square feet in all. The construction of the filters was in all respects similar to the Jewell filter used at Louisville. The raw water was from Lake Erie, and during the examination was always comparatively clear, but contained considerable numbers of bacteria. The problem was thus entirely one of bacterial efficiency. The question of clarification hardly presented itself. Although the water became turbid at times it did not approach in muddiness the condition of the Ohio River water, and an amount of coagulant sufficient for a tolerable bacterial efficiency in all cases was more than sufficient for clarification.
A summary of the results obtained is as follows:
| Week Ending 6:00 P.M. |
Average Rate of Filtration, Gallons per Sq. Ft. Min. |
Sulphate of Alumina, Grains per Gallon. |
Bacteria in Lake Water. |
Bacteria in Effluent. |
Bacterial Efficiency per cent. |
|---|---|---|---|---|---|
| June 19 | 1.06 | 2.58 | 1441 | 16 | 98.9 |
| 26 | 1.10 | 2.50 | 385 | 6 | 98.4 |
| July 3 | 1.11 | 2.27 | 367 | 9 | 97.5 |
| 10 | 1.28 | 1.07 | 154 | 14 | 90.9 |
| 17 | 1.14 | 0.94 | 189 | 26 | 86.3 |
| Average | 1.14 | 1.83 | 507 | 14 | 96.4 |
| The average bacterial efficiency was 96.4 per cent with 1.83 grains of sulphate of alumina per gallon. | |||||