COMPARISON OF SEDIMENTATION AND DISSOLVED AIR FLOTATION MODELING FOR CRYPTOSPORIDIUM REMOVAL

Han, Moo-Young; Kim, Won-Tae

Environmental Engineering Research 2000;5(3): 151-156.

Moo-Young Han^†, and Won-Tae Kim

School of Civil, Urban and Geosystem Engineering, Seoul National University, Seoul 151-742, Korea

Corresponding Author: Moo-Young Han ,

Received: June 9, 2000; Accepted: September 8, 2000.

ABSTRACT

Removal mechanisms for Cryptosporidium oocysts by sedimentation and dissolved air flotation (DAF) were investigated and compared using mathematical modeling. A set of trajectory analyses was performed for each process to estimate the collision efficiency of Cryptosporidium oocysts and other particles (i.e., floe particle or bubble). The sensitivity of a removal efficiency factor to major parameters of the treatment system was investigated for each process. Trajectory analysis modeling suggested that DAF is a better treatment option than sedimentation for the removal of Cryptosporidium. In sedimentation, floe size and floe zeta potential did not affect the collision efficiency. In DAF, the collision efficiency factor greatly increased when the sign of the zeta potential of bubbles and Cryptosporidium oocysts was opposite. This theory could explain the current practice in DAF which emphasizes the importance of pretreatment. These theoretical predictions agreed well with experimental data obtained by others. An optimum bubble size tor DAF was suggested. In addition, an improved DAF process using a positively charged bubble was proposed based on the theoretical analyses.