AWWA QTC97011

A population balance model has been developed to simulate the kinetics of flocculation in turbulent flow. The model was used to predict the floc size distribution in three square flocculation reactors with two impeller types (Rushton turbine and A310 fluid foil impeller) at constant average velocity gradient G=40 S-1. The model includes a term in the breakup part of the population balance rate equation that represents the turbulence intensity generated in the impeller discharge zone. Reinforcing the photographic results of the floc size distribution, the population balance model predicts the shift in the particle size distribution from larger particles to smaller particles with increasing tank size. The model is also effective at predicting the shift in the particle size distribution from larger particles to smaller particles when the impeller is switched from the A310 foil impeller to the Rushton turbine. The results from model simulations confirm that the steady state floc size distribution is limited by the turbulence intensity in the impeller discharge zone. These results suggest that steady state floc size distribution is not a function of the average intensity of the turbulent motion throughout the reactor volume as suggested in models based on G.

Product Details

Published:

01/01/1997

ISBN(s):

0898679583

Number of Pages:

17

File Size:

1 file