Colloid filtration in fluidized beds.

Particle transport and capture are essential for the successful treatment by fluidized-bed biofilm processes of wastewaters containing suspended organic matter. Small-scale, once-through, fluidized-bed filters were utilized to analyze the transport mechanisms and effects of collector surface chemistry on the removal of ferric-hydroxide flocs by fluidized granular activated carbon collectors. Experimental results demonstrated that the mechanisms of diffusion, gravity sedimentation, and interception acted according to theory to provide particle transport to the surface; that gravity sedimentation was the dominant mechanism under the conditions studied and was not affected by the upward water velocity; that the inertial mechanism was unimportant; that not having strictly laminar conditions did not invalidate use of the mechanistic model; that conditioning of the carbon surface greatly affected the cohesion efficiency; and that expansion of the bed by greater superficial flow velocities caused suspended-particle removal efficiencies to decline.