Bacteria examinations of the river water extending over about three months in the summer, when the bacteria are the most numerous, show the maximum number of bacteria per cubic centimeter of 16,000 and a minimum of 2,300, and an average of 8,000 per cubic centimeter. After filtration in the effluent water there was found a maximum of 300, a minimum of 21 and an average of no per cubic centimeter. The maximum bacterial efficiency of the filter was found to be 99.4 percent, its minimum 96 percent, and its average 98.2 percent.