Membrane Fouling Mitigation with Water Hammer

Membrane technology has proven to become a prolific separation technique in many industries. However, its widespread application has been limited by fouling. Fouling results in a decline in membrane performance and requires regular chemical cleaning to sustain the operation. This thesis focuses on the development of a new approach to mitigate fouling by subjecting a membrane to water hammer. The water hammer was generated by a solenoid valve installed at the retentate side of a cross-flow ultrafiltration unit. With this configuration, we hypothesize that the backpressure generated from the water hammer effect (WHE) could promote shear at the membrane surface, thus alleviating the fouling. With emphasis on dairy industry application, ultrafiltration (UF) experiments were carried out with whey protein concentrate solutions under various operating parameters to determine the permeate flux improvement by the applied water hammer. Up to 84% permeate flux enhancement was obtained with water hammer. The ability of the water hammer to ease membrane fouling decreased with increase in transmembrane pressure (TMP) and feed concentration. Subsequently, the effect of water hammer shear on the integrity of whey protein was investigated by measuring the whey particle size and protein concentration in the feed, retentate, and permeate. The protein content of the permeates of UF experiments (WHE and NO WHE) were comparable indicating no significant difference in the permeation process due to water hammer. The retentates, however, showed significantly higher protein concentration (2 to 4 times) for WHE experiments due to greater detachment of foulants from the membrane. Studies with hydrophobic microfiltration (MF) membranes revealed the influence of particlemembrane interactions on water hammer fouling control. Water hammer was effective in removing loosely attached foulants, which was later confirmed with membrane surface scanning electron microscope (SEM) and scanning probe microscopy (SPM) imaging. Analysis of the critical mechanisms involved in the flux improvement was done by modelling the increase in shear stress at the membrane surface due to water hammer. The variables affecting degree of fouling mitigation by water hammer technique were identified as the operating conditions, viscosity of the liquid, valve closing duration and frequency, boundary layer thickness and type of foulant. Water hammer was also studied on hollow fibre membrane modules at different crossflow velocities to determine the influence of WHE intensity with fouling mitigation. In addition to whey protein concentrate (WPC), silica particles were also used as feed to analyse the fouling control characteristics on different solute types. The axial foulant distribution was analysed in detail to study the mechanism of water hammer mitigation technique along the length of the fibre. The results showed thinner cake layers for silica and WPC on water hammer operated membranes. The type of cake and its removal rate was determined by the solute properties and solute-membrane interaction. The contribution of water hammer shear in fouling removal reduced while that of crossflow shear increased at high CFV. Finally, the periodic water hammer shear was able to reduce and even out the foulant distribution along the length of hollow fibres (especially at the retentate section) enabling better flux.

Name thesis:degree_name

PhD

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Chemical and Materials Engineering

Grantor dc:publisher

ResearchSpace@Auckland

Year dc:date.issued

2023

Author dc:creator

• Aslam, Mohamed

Advisor dc:contributor.advisor

• Wicaksana, Filicia

Statement dc:rights

• Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Licence dc:rights.uri

• https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm

Handle dc:identifier.uri

https://hdl.handle.net/2292/64597

OAI identifier oai:identifier

oai:researchspace.auckland.ac.nz:2292/64597