COLLISION EFFICIENCY FACTOR IN BROWNIAN COAGULATION (ALPHA-BR) INCLUDING HYDRODYNAMICS AND INTERPARTICLE FORCES

In order to realistically model the behavior of Brownian particles in water, collision efficiency factor in Brownian coagulation (alpha Br) should be included. alpha Br is calculated by solving the diffusion eq uation including the detailed mathematical description of hydrodynamic s and interparticle forces. alpha Br is found to be a function of seve ral parameters: particle size and ratio, Hamaker constant, ionic stren gth of liquid, surface potential of particle. Ionic strength and surfa ce potential significantly affect alpha Br. The graphical plane of ion ic strength and surface potential is divided into two regions by a cur ve: above this curve, no coagulation is expected, however, below this curve, coagulation is expected. ci Br values in this region are the sa me as those predicted for no electric repulsion. The model qualitative ly explains the change of coagulation efficiency at estuary or water t reatment plant. Better prediction of suspensions at both stabilized an d destabilized system can be made possible incorporating the collision efficiency factors of the other coagulant mechanisms such as differen tial sedimentation and fluid shear. (C) 1997 IAWQ. Published by Elsevi er Science Ltd.