REMOVAL OF BACTERIA IN LABORATORY FILTERS - MODELS AND EXPERIMENTS

Five filtration models were used to predict the effect of particle siz e on removal in several types of laboratory filters (nylon, cellulose and glass fiber). All, models predicted similar trends in removal with particle size, although the capillary-pore model predicted substantia lly lower removals than the other four fibrous filtration models. Thes e models indicated that bacterium-size (approximately 1 mum) particles are removed in filters primarily through the filtration mechanism of particle interception. Based on advertised pore sizes, removal of bact erium-size particles was a function of filter material in the order ce llulose > nylon > glass fiber. The percent of bacteria removed in a ny lon filter (5 mum pore diameter) was similar to removal in GF/C filter s (1.2 mum pore diameter) as a result of a higher sticking coefficient of bacteria with nylon than with glass. The average sticking coeffici ents of three bacteria, Pseudomonas sp. JS6, Pseudomonas fluorescens P 17 and Bacillus pumilus, in glass fiber (GF/C) filters, were 0.01, 0.2 4 and 0.20, respectively. These results indicate that filtration model s can be used to describe particle removal during laboratory filtratio n of water and wastewater samples, and that bacteria have relatively h igh sticking coefficients for filter materials.