MEASUREMENT OF BACTERIAL COLLISION EFFICIENCIES IN POROUS-MEDIA

A new method, utilizing radiolabeled (H-3-leucine) cells and 1-cm colu mns packed with 40-mu m borosilicate glass beads was used to estimate bacterial collision efficiency by directly measuring the retention of cells in porous media. At a fractional retention of 0.051 (n = 3), the coefficient of variation was 0.037, permitting meaningful estimation of collision efficiencies as low as 3 x 10(-5). Collision efficiency w as a function of the ionic strength and species identity; alpha increa sed from 1.6 x 10(-3) to 1.4 x 10(-2) for A. paradoxus in 10(-5) and 1 0(-3) M NaCl solutions, respectively, and from 8.9 x 10(-3) to 6.2 x 1 0(-2) for P. fluorescens in the same solutions. Results were not sensi tive to test parameters such as velocity, volume filtered and rinse vo lume. The new procedure provides a convenient, reliable, accurate meth od for estimating low-end biocolloid collision efficiencies in porous media. In the range alpha < 0.01, the method is economical, significan tly faster, and much more reliable than other published procedures. It s application may accelerate efforts to establish functional relations hips between biocolloid collision efficiency and governing physical-ch emical variables.