Abstract
A series of filtration experiments was performed systematically to investigate physical and chemical factors affecting the efficiency of backwashing during microfiltration of colloidal suspensions. In this study, all experiments were conducted in dead-end filtration mode utilizing an outside-in, hollow-fiber module with a nominal pore size of 0.1 μm. Silica particles (mean diameter = 0.14 μm) were used as model colloids. Using a flux decline model based on the Happel's cell for the hydraulic resistance of the particle layer, the cake structure was determined from experimental fouling data and then correlated to backwash efficiency. Modeling of experimental data revealed no noticeable changes in cake layer structure when feed particle concentration and operating pressure increased. Specifically, the packing density of the cake layer (1-cake porosity) in the cake layer ranged from 0.66 to 0.67, which corresponds well to random packing density. However, the particle packing density increased drastically with ionic strength. The results of backwashing experiments demonstrated that the efficiency of backwashing decreased significantly with increasing solution ionic strength, while backwash efficiency did not vary when particle concentration and operating pressure increased. This finding suggests that backwash efficiency is closely related to the structure of the cake layer formed during particle filtration. More densely packed cake layers were formed under high ionic strength, and consequently less flux was recovered per given backwash volume during backwashing.
| Original language | English |
|---|---|
| Pages (from-to) | 257-268 |
| Number of pages | 12 |
| Journal | Desalination |
| Volume | 173 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - 2005 Mar 20 |
Bibliographical note
Funding Information:The authors would like to acknowledge the American Water Works Association Research Foundation (AwwaRF) for financial support. Additional funding for this project was provided by Brain Korea 21 (BK21). Furthermore, SK Chemicals and Nissan Chemical Industries, Ltd., respectively provided the hollow-fiber MF module and model silica colloids used throughout this study.
Keywords
- Backwashing efficiency
- Cake layer structure
- Colloidal fouling
- Microfiltration
- Water treatment
ASJC Scopus subject areas
- General Chemistry
- General Chemical Engineering
- General Materials Science
- Water Science and Technology
- Mechanical Engineering