| lthough slow sand filters have been used for two centuries, a fundamental understanding of particle removal mechanisms has not been developed. Numerous hypotheses of slow sand filter particle removal mechanisms have been suggested, however, none of the hypotheses have been verified. The purpose of this research was to identify and verify the bacteria removal mechanism(s) in slow sand filters.;By measuring E. coli concentration as a function of depth, it was determined that removal of E. coli occurred primarily in the top few centimeters of the filter medium. The addition of biological poisons provided strong evidence that a predator was removing the bacteria, and the lack of E. coli removal when Cayuga Lake water was first filtered through a 0.2 ;Bench scale slow sand filters and appurtenances were constructed to test the effects of various amendments and feed modifications on bacteria removal. The filtration apparatus was also designed for sample collection as a function of depth. In most experiments the water was obtained from a raw water tap at Bolton Point Water Treatment Plant on Cayuga Lake. A pure culture of Escherichia coli was added to the raw water in all experiments so that E. coli removal through the filter columns could be measured. In different experiments the raw water was modified by the addition of biological poisons, by the addition of a pure culture of Pseudomonas putida, and by filtration through a 0.2... |
