Fouling of membranes by biological macromolecules

• Main Author: Tan, Chia Wen.
• Other Authors: Tang Chuyang
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Environmental engineering::Water treatment
• Online Access: http://hdl.handle.net/10356/38945
• Institution: Nanyang Technological University

Fouling of NF270, NF90 and XLE membranes by macromolecules, represented by three model protein foulants (lysozyme, Bovine Serum Albumin (BSA) and binary protein mixture (BSA-LYZ)), has been examined in this study. Effects of hydrodynamic conditions (initial flux and cross-flow velocity) and feed solution composition (pH, ionic strength and calcium ions) on protein fouling were observed. Bench-scale cross-flow test unit was employed with baseline electrolyte of 10mM NaCl (unless otherwise specified) and foulant concentration 20mg/L at constant room temperature (26°C) for the fouling tests. Flux throughout the seven-day fouling experiment was recorded by data-logger to a computer terminal. Mass deposition of fouled membranes was evaluated by UV-absorbance method with UV-Visible Spectrometer at the end of fouling runs. In addition, salt rejection of NF270 membranes was calculated. From this study, significant flux decline was observed with initial flux higher than limiting flux. Higher pH of feed solution also promised greater flux decline and foulant deposition on NF270 with lysozyme as model foulant. On the other hand, higher ionic strength (100mM) and presence of Calcium (Ca2+) did not have significant impact on flux decline and lysozyme deposition on NF270. However, both seemed to reduce salt rejection of NF270. Under comparison, binary protein mixture (BSA-LYZ) resulted in most severe fouling. Nevertheless, an overall improvement for salt rejection was observed for all three model foulants. Finally, flux decline trends for XLE, NF90 and NF270 were found to converge ultimately which was likely due to foulant-deposited-foulant interactions rather than interactions between foulant and membranes.