Transparent exopolymeric particles (TEP) formed from calcium and alginate blocks and their effects on membrane fouling

• Main Author: Toh, Helen Jiahui
• Other Authors: Liu Yu
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/61172
• Institution: Nanyang Technological University

Membrane fouling has always been a major challenge faced in the membrane technology. Recently, the abundance of the highly sticky Transparent Exopolymeic Particles (TEP) in surface water was found to be a potential foulant in the membrane system (Berman and Holenberg, 2005). In addition, the water chemistry of the feed solution such as calcium concentration can also influence the extent of membrane fouling. While Sodium Alginate is commonly used as the model foulant in membrane fouling studies, there is very limited information available on the fouling tendency with regards to the alginate blocks in the presence of Ca2+ ions in membrane filtration. In order to understand the fouling behaviour, the effects of TEP on membrane fouling with Ca2+ ion were studied using MG-, MM- and GG- blocks separated from sodium alginate. TEP was determined using UV–Vis spectrophotometer (Passow and Alldredge et al., 1995) and Field Emission Scanning Electron Microscopy (FESEM) quantitatively and qualitatively. Results showed highest TEP formation in GG block and least TEP formation in MG block in the presence of Ca2+ ion. Liquid Chromatography – Organic Carbon Detection (LC-OCD) analysis of the alginate blocks further indicated that GG block has the highest composition of the large particles (>20000 Da) while MM and MG block comprises mainly of the smaller particles (~1000 Da) with MG block consisting the least amount of the TEP particles. Cross flow ultrafiltration was carried out to investigate the membrane fouling behaviours in 1 mM of Ca2+ ion using solutions of alginate blocks as the feed solution. Results showed the severest flux decline with lowest final flux in the filtration of GG block and the least flux decline with highest final flux in the filtration of MG block which coincided with the results obtained from the TEP level determination. Fouling mechanisms were proposed to explain the fouling behaviours of the alginate fractions which was essentially associated with the TEP size distribution. This study provided insights into the effect of Ca2+ ion on alginate blocks associated to membrane fouling. It also further suggested that the membrane fouling would be related to the molecular structure and the physical properties of the alginate blocks which explained the different interactions of alginate blocks with the Ca2+ ion.