System dynamics modeling and simulation of a coagulation–ultrafiltration process for the treatment of drinking water

Abstract

In this work, a system dynamics (SD) model of a coagulation–ultrafiltration (UF) process was developed using Vensim and validated with experimental data. The SD model includes the basic elements and essential structure of the coagulation–UF process system. Numerical simulations were used to optimize the operating parameters of the SD model. The simulation results demonstrated that the absorption resistance (R_a) contributed a small portion of the total resistance (R_t) (≤15%) in the basic experiment, where the initial permeate flux (J₀) was 35 m³/(m² h). Furthermore, the cake layer resistance (R_c) was the main cause of the total resistance (R_t) within the model. The concentration of coagulant and the removal rate of membrane fouling were positively correlated when the coagulant concentration increased from 20 to 35 mg/L. In addition, the contribution of total resistance to membrane fouling was obtained from the SD model. The membrane fouling rate reached 22.5 Pa/h after 16 backwashing cycles which corresponds to the predicted chemical cleaning time. The SD model presented here can provide guidance in optimizing operating parameters through numerical simulations which eschew the need for large amounts of repeated tests.

Keywords:

• System dynamics modeling
• Coagulation–ultrafiltration process
• Cake layer resistance
• Membrane fouling
• Drinking water treatment

Acknowledgments

This research project was supported by the National Science Foundation, China (project reference No.: 51308390) and the key project of the National Social Science Foundation, China (project reference No.: 13AZD011): The development of city water and river basin water ecological environment protection.