Coagulation perikinetic

In summary, polymeric flocculants generally increase peri-kinetic flocculation rates compared with perikinetic coagulation rates. This is not necessarily true for orthokinetic flocculation, and experimental results in the literature are seemingly in conflict. Collision rate theory predicts that the polymer adsorption step may become rate limiting in orthokinetic flocculation. The present study was designed to elucidate the relationship between polymer adsorption rates and particle flocculation rates under orthokinetic conditions. 

The ratio of perikinetic adsorption halftime to perikinetic coagulation halftime is given by... 

The ratio of the probability of a collision induced by a fluid velocity gradient (dv/dx) (i.e., orthokinetic coagulation) to the collision probability under the influence of Brownian motion (perikinetic coagulation—what we have considered so far) has been shown to be (Probstein 1994)... 

Perikinetic Coagulation. The concentration of small silica colloids (Ludox LS d = 15 m/ ) used in these studies was between 0.18 gram/liter and 0.43 gram/liter (36.5 — 86.0 meter2/liter or 5.0-11.5 X 1013 par-ticles/ml.). The dispersion, contained in a spectrophometric cell, was... 

B) Relative colloid stability as a function of the total concentration of coagulant added, Ct, at constant pH—obtained from the measurement of perikinetic coagulation rates according to Equation 3. (Ludox LS = 0.3 gram/liter)... 

Perikinetic Coagulation. If colloidal particles are of such dimensions that they are subject to thermal motion, the transport of these particles is accomplished by this Brownian motion. Collisions occur when one particle enters the sphere of influence of another particle. The coagulation rate measuring the decrease in the concentration of particles with time, N (in numbers/ml.), of a nearly monodisperse suspension corresponds under these conditions to the rate law for a second order reaction (15) ... 

To improve perikinetic coagulation by physical parameters, if possible at all, we are confined to adequate and immediate homogenization of coagulant with the raw water treated. If we do wish to control the coagulation in the perikinetic region better, optimatization of the process chemical parameters is the only practical way of doing it. The collision efficiency factor Op must be as far from 0 as possible, or better, as close to 1 as possible. 

In conventional technologies of purification featuring sedimentation or clarification as tjie first separation stage, perikinetic coagulation is usually only the first step of aggregation reactions. If chemical requirements to maximize flp of raw water are not entirely met, higher flocculation intensity or time is needed. 

Figure 5.20 Illustration of an aggregate-size distribution function, f x), as a function of reduced aggregation number (x) in a suspension undergoing rapid (perikinetic) coagulation. (Adapted from fitting Equation 5.19 to experimental data reported by Gregory [79].)...

This simple model suggests that (k ) depends very Strongly on the radius. The ratio between the rate constants of orthokinetic and perikinetic coagulation is then given as follows ... 

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