Browsing by Author "Nasser, Mustafa"

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    Clogging vs. fouling in immersed membrane bioreactors
    (Elsevier, 2018-07-09) Buzatu, Pompilia; Qiblawey, Hazim; Odai, A.; Jamaleddin, J.; Nasser, Mustafa; Judd, Simon J.
    Whilst the fouling of MBR membrane surfaces has been very extensively explored by the academic community, there is an increasingly widespread recognition by practitioners of the issue of clogging of membrane channels with sludge solids, sometimes termed “sludging”. The study undertaken has quantified this phenomenon using a bespoke test cell allowing a flat sheet membrane channel to be viewed directly during operation and the accumulated solids determined by digital image processing. Sludging behaviour has then been correlated both with the sludge properties, from sludge samples taken from both an industrial and municipal MBR, and the permeability decline rate data. The work has revealed the expected trends in fouling propensity, as quantified by the exponent n of the Δp/Δt = m.exp(nJ) correlation from classical flux-step tests. With zero membrane aeration the industrial samples exhibited sludging, the filling of the complete thickness of the membrane channel with sludge solids, whereas for municipal sludge the solids formed a cake layer which did not fill the channel. In the absence of sludging the permeability decline followed the expected pattern of increasing at the elevated soluble COD and capillary suction time values of the industrial sludge, compared with municipal sludge at the same solids concentration range (8–12 g.L−1). However, there was no evident correlation between fouling (permeability decline without sludging) and sludging: incipient sludging did not appear to influence permeability, though can be assumed to negatively impact on long-term operation, or relate to the sCOD concentration. Sludging instead appeared to depend on the sludge physical properties, and primarily the viscosity: sludge samples at high viscosities were found to exhibit a different air-scour pattern to that at normal MLSS concentrations. Outcomes suggest that sludging is caused by rheological conditions promoting bubble coalescence and bubble stream constriction, reducing the exposure of the membrane surface to scouring air.
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    Impact of combined oil-in-water emulsions and particulate suspensions on ceramic membrane fouling and permeability recovery
    (Elsevier, 2018-11-03) Abdalla, Mays; Nasser, Mustafa; Fard, Ahmad Kayvani; Qiblawey, Hazim; Benamor, Abdelbaki; Judd, Simon J.
    The application of crossflow ceramic microfiltration (CFCMF) to the removal of emulsified oil from a simple analogue of raw produced water (PW) arising from oil exploration has been studied. Outcomes relate to surfactant-stabilised oil-in-water (o/w) emulsions both as a discrete emulsion and in combination with a colloidal suspension of particulate solids (bentonite). The impact on both fouling during the filtration cycle and residual fouling of the ZrO2-TiO2 membrane, following aggressive caustic-acid chemical cleaning applied between six sequential 30-min filtration runs, was investigated. Results showed the addition of suspended solids to the o/w emulsion to be extremely deleterious to sustaining both the permeability and selectivity of the membrane. The addition of 1500 mg·L−1 of bentonite to a 10 vol.% emulsion resulted in a permeability decrease of 3.5–5 times over that recorded for the emulsion, and 8–36 times lower than that of the bentonite suspension. Oil passage through the microfiltration membrane (0.45 μm pore size) was concomitantly increased six-fold. Tests performed to assess the cleanability of the membrane demonstrated similar differences between the three feed liquids. The permanent fouling of the membrane by the combined emulsion/suspension reduced its permeability by a factor of 16 over that attained for the emulsion-fouled membrane, or 25 times less than the residual permeability of the membrane challenged with the suspended particles. Moreover, the residual permeability of the emulsion/suspension-fouled membrane was still in decline following the sixth run. The results emphasise the importance of considering possible particle-emulsion interactions in studying membrane filtration of PW analogues.