Modeling of flocculation systems using particle size distribution.

摘要

Scope and method of study. A study was conducted to model the flocculation process. Incorporated into the collision frequency functions of the model are terms to account for hydrodynamic interactions, floc density, floc shape, floc break-up and effective velocity gradient. The model predictions for particle size distribution are compared to the measured particle size distribution from two actual treatment plant and a batch reactor. In order to assess input parameters contribution to uncertainty in the model's predictions and obtain a safety factor, sensitivity analysis and Monte Carlo simulation were performed.; Findings and conclusions. Improvements in a flocculation model were made by incorporating several factors which affect flocculation performance. The modified model matched the measured results for high concentration without the collision efficiency factor. However, the modified model underestimated flocculation rate for low particle concentration. The modified model predicted well the particle size distribution, measured by an automatic image analyzer, results obtained under G = 22 sec{dollar}sp{lcub}-1{rcub}{dollar} but overestimated the particle size distribution under G = 60 sec{dollar}sp{lcub}-1{rcub}.{dollar} The sensitivity analysis indicated that the particle size distribution and the relationship between the particle size and density were the major contributors to uncertainty in the flocculation model. The Monte Carlo simulation applied to the modified model showed that the model output could be represented by a normal distribution. A safety factor was calculated from the model output mean and confidence interval.