AWWA JAW48560

The research described in this article was directed toward achieving a fundamental understanding of detachment of biological particles compared with that of nonbiological particles under fluidization backwash conditions. This study provided insights into the particles' comparative removal and detachment mechanisms as well as the strength and location of their attachment to the surfaces of media grains. The experimental results relate only to bacteria as the biological particles; however, the theory may also be applicable to protozoa. Specific objectives were to compare the detachment of biological particles with nonbiological particles during fluidized bed expansion backwash, calculate theoretically the forces involved in detachment of these groups of particles, and analyze experimental results in terms of a micro-mechanics force model. Includes 50 references, table, figures.