------------+----------+----------+---------+----------+--------+----------- Number | | Bacteria. | | |Sulphate of of Days |Turbidity.+----------+---------+ Per cent |Per cent| Alumina Represented.| |Raw Water.|Effluent.|remaining.|removed.|used Grains | | | | | |per Gallon. ------------+----------+----------+---------+----------+--------+----------- 6 | 0.03 | 14,037 | 6217 | 44.29 | 55.71 | 0.00 5 | 0.07 | 4,267 | 680 | 15.93 | 84.07 | 0.24 14 | 0.06 | 2,613 | 170 | 6.50 | 93.50 | 0.35 10 | 0.06 | 2,446 | 113 | 4.62 | 95.38 | 0.44 9 | 0.11 | 7,303 | 234 | 3.20 | 96.80 | 0.55 20 | 0.09 | 6,979 | 220 | 3.15 | 96.85 | 0.65 9 | 0.08 | 5,191 | 130 | 2.50 | 97.50 | 0.75 16 | 0.12 | 8,504 | 242 | 2.84 | 97.16 | 0.83 22 | 0.16 | 8,506 | 99 | 1.16 | 98.84 | 0.96 12 | 0.11 | 11,998 | 246 | 2.05 | 97.95 | 1.05 14 | 0.18 | 18,982 | 423 | 2.23 | 97.77 | 1.16 5 | 0.14 | 13,981 | 224 | 1.60 | 98.40 | 1.23 9 | 0.27 | 19,806 | 325 | 1.64 | 98.36 | 1.34 14 | 0.27 | 16,549 | 324 | 1.96 | 98.04 | 1.45 9 | 0.29 | 12,194 | 96 | 0.79 | 99.21 | 1.54 6 | 0.25 | 13,483 | 51 | 0.38 | 99.62 | 1.65 7 | 0.53 | 24,243 | 220 | 0.91 | 99.09 | 1.72 3 | 0.90 | 20,953 | 602 | 2.88 | 97.12 | 1.90 5 | 0.43 | 25,958 | 307 | 1.19 | 98.81 | 2.19 4 | 0.84 | 21,017 | 228 | 1.09 | 98.91 | 3.71 ------------+----------+----------+---------+----------+--------+----------- These results are shown graphically by Fig. 21. [Illustration: FIG. 21.—BACTERIAL EFFICIENCIES OF MECHANICAL FILTERS.] INFLUENCE OF DEGREE OF TURBIDITY UPON BACTERIAL EFFICIENCY OF MECHANICAL FILTERS.