An examination of the nature of critical flux and membrane fouling by direct observation Neal, Peter Ross en_US 2022-03-21T16:01:07Z 2022-03-21T16:01:07Z 2006 en_US
dc.description.abstract Securing water in the right quantities at the right quality for the right price is a major issue around the world. Membranes are making an increasingly important contribution to meeting this need; however their performance is limited by fouling. This thesis reports on an investigation into the fouling of systems related to water treatment using the Direct Observation Through the Membrane (DOTM). The investigation focused on the measurement of critical flux and observation of particle behaviour under a variety of conditions and for a number of different particles. The range of meanings attributed to critical flux in the literature was analysed and several proposals made for the improved use of the concept. In particular, critical flux determination techniques were classified by whether they measure resistance changes or particle deposition; leading to the definition of Critical Resistance and Critical Deposition Fluxes. In this thesis the deposition definition is used exclusively. The effect of Reynolds number and spacer orientation on critical flux was correlated for spacer-filled channels. The heterogeneous deposition patterns observed with regions of heavy deposition next to areas of little or no deposition. This pattern was related to the local hydrodynamics of spacer cells (a few mm2 in size). The correlations developed for critical flux in spacer-filled channels were adjusted for submicron particle size and incorporated into a SpiralWound Module (SWM) leaf model and then used to simulate the fouling of SWM leaves under a range of operating conditions and operating policies. The Mass Balance technique of critical flux determination was also briefly assessed. The applicability of critical flux criteria to SWM arrays was discussed. Fouling, particle behaviour and critical flux were also investigated in air-sparged systems. The post-cleaning water flux was found to be enhanced when the membrane is fouled in the presence of bubbles. The rate of flux decline was reduced by bubbles. Critical flux increased with air flowrate, and decreased with increased liquid flowrate and concentration. Bubbles caused particles to periodically deposit on the membrane. Particles were observed to stream past the membrane under the influence of back-diffusive forces. Video clips of particulate fouling are provided. en_US
dc.language English
dc.language.iso EN en_US
dc.publisher UNSW, Sydney en_US
dc.rights CC BY-NC-ND 3.0 en_US
dc.rights.uri en_US
dc.subject.other Water -- purification -- membrane filtration -- particle removal; membrane filters -- testing; membrane bioreactors -- testing; fouling; fluid dynamic measurements; membrane separation. en_US
dc.title An examination of the nature of critical flux and membrane fouling by direct observation en_US
dc.type Thesis en_US
dcterms.accessRights open access
dcterms.rightsHolder Neal, Peter Ross
dspace.entity.type Publication en_US
unsw.relation.faculty Engineering
unsw.relation.originalPublicationAffiliation Neal, Peter Ross, Chemical Sciences & Engineering, Faculty of Engineering, UNSW en_US School of Chemical Engineering *
unsw.thesis.degreetype PhD Doctorate en_US
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