Browsing by Author "Qiblawey, Hazim"

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    Ceramic membrane filtration of produced water: impact of membrane module
    (Elsevier, 2016-04-01) Zsirai, T.; Al-Jaml, A. K.; Qiblawey, Hazim; Al-Marri, M.; Ahmed, A.; Bach, S.; Watson, S.; Judd, Simon J.
    Produced water (PW) generated from oil exploration requires rigorous removal of suspended matter (free oil and particulate solids) as tertiary treatment (downstream of hydrocyclone and gas flotation) if it is to be re-injected into low-permeability reservoirs. The viability of membrane filtration for this duty is largely dependent on sustaining a high membrane flux to minimise the process footprint. A pilot-scale study of PW filtration using crossflow multi-channel ceramic membrane technology has been conducted to identify the appropriate membrane characteristics for sustaining the flux whilst maintaining the required treated water quality. Membranes based on two materials (silicon carbide, SiC, and titanium dioxide, TiO2) and two different pore sizes were challenged with real PW samples taken from oil platforms operating on the Arabian Gulf. The membranes were characterised according to the overall permeability decline rate and the end permeability. Results suggest that SiC membranes outperform TiO2 ones with respect to sustainable permeability under the same operating and maintenance conditions. The SiC microfiltration membrane provided anomalously high permeabilities but also the highest fouling propensity. Results suggest that whilst the high fluxes (1300–1800 L m−2 h−1) are attainable for the technology, this is contingent upon the application of an effective chemical clean.
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    Cleaning of ceramic membranes for produced water filtration
    (Elsevier, 2018-03-09) Zsirai, T.; Qiblawey, Hazim; Buzatu, Pompilia; Al-Marri, M.; Judd, Simon J.
    The application of ceramic microfiltration membranes to the tertiary treatment of produced water from an Arabian Gulf oilfield has been studied using a dedicated pilot plant. Studies were based on a previously published protocol in which the retentate stream was recycled so as to successively increase the feed concentration throughout the experimental run. Chemical cleaning in place (CIP) was applied between each run and the flux and permeability recovery recorded for various cleaning protocols studied, the CIP being based on the combination of caustic soda (NaOH) and citric acid. Surface analysis of the membrane, and specifically its hydrophilicity, was also conducted. Results indicated the main influencing factor on permeability recovery from the CIP to be the employment of backflushing during the CIP itself. A final flux of 700 L m−2 h−1 was sustained through the application of 6 wt% NaOH with 6 wt% citric acid combined with backflushing at approximately twice the rate of the filtration cycle flux. A consideration of the impact of this flux value on the viability of two commercially-available ceramic membrane technologies indicated the footprint incurred to be slightly lower than that of the upstream induced gas flotation technology and corroborated a previously published estimate. The flux was sustained despite surface analysis indicating a loss of the innate hydrophilicity of the ceramic membrane.
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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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    Comparative power demand of mechanical and aeration imposed shear in an immersed membrane bioreactor
    (Elsevier, 2017-09-12) Buzatu, Pompilia; Nasser, M. S.; Qiblawey, Hazim; Judd, Simon J.
    The power demanded for the application of mechanically-imposed shear on an immersed flat sheet (iFS) membrane bioreactor (MBR) has been compared to that of conventional membrane air scouring. Literature correlations based on the Ostwald model were used to define the rheological characteristics of an MBR sludge. The correlation of specific power demand (, in Watts per m2 membrane area) with shear rate γ in s-1 was developed from first principles through a consideration of the force balance on the system in the case of mechanically-imposed shear. The corresponding aeration imposed shear correlation was interpreted from literature information. The analysis revealed the energy required to impose a shear mechanically through oscillation (or reciprocation) of the membrane to be between 20 and 70% less than that demanded for providing the same shear by conventional aeration of the immersed membrane. The energy saving increases with decreasing shear in accordance with a power demand ratio (aeration:mechanical) of 1400γ-1.4 for a specific sludge rheology. Whilst the absolute value is dependent on the sludge rheology, the aeration:mechanical power demand ratio is determined by the difference in the two exponents in the respective correlations between and γ. Consequently, aeration-imparted shear becomes energetically favoured beyond some threshold shear rate value (∼180 s-1, based on the boundary conditions applied in the current study). The outcomes qualitatively corroborate findings from the limited practical measurement of energy demand in MBRs fitted with reciprocating immersed membranes.
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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.
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    The impact of mechanical shear on membrane flux and energy demand
    (Elsevier, 2016-06-10) Zsirai, T.; Qiblawey, Hazim; A-Marri, M. J.; Judd, Simon J.
    The use of forced mechanical shear for both disc membranes (rotating and vibrating disc filtration, RDF and VDF respectively) and hollow fibres (vibrating HF membranes, VHFM) is reviewed. These systems have been extensively studied and, in the case of the disc membranes, have reached commercialisation and proven effective in achieving transmembrane pressure (TMP) control for various challenging feed waters. The effects of operating conditions, namely shear rate as enhanced by rotation and vibration speed and TMP, and feed water quality on the filtration flux and specific energy consumption are quantified as part of the review. A new relationship is revealed between the two empirical constants governing the classical relationship between membrane flux and shear rate, and a mathematical correlation proposed accordingly. A study of available information on energy reveals that operation at lower shear rates (i.e. rotation or vibration speeds) and more conservative fluxes leads to lower specific energy demands in kWh m−3 permeate, albeit with a larger required membrane area.
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    The impact of mechanically-imposed shear on clogging, fouling and energy demand for an immersed membrane bioreactor
    (MDPI, 2018-11-10) Judd, Simon J.; Odai, Albert; Buzatu, Pompilia; Qiblawey, Hazim
    The impact of the application of mechanically-imposed shear on the propensity for fouling and clogging (or “sludging”—the agglomeration of sludge solids in the membrane channel) of an immersed flat sheet (iFS) membrane bioreactor (MBR) was studied. The bench-scale test cell used contained a single flat sheet fitted with a crank and motor to allow the membrane to be oscillated (or reciprocated) vertically at a low rate (20 RPM). The membrane was challenged with sludge samples from a local MBR installation treating petroleum industry effluent, the sludge having previously been demonstrated as having a high sludging propensity. Sludging was measured by direct visual observation of membrane surface occlusion by the agglomerated solids, with fouling being notionally represented by the rate of transmembrane pressure increase. Results demonstrated membrane reciprocation to have a more beneficial impact on sludging amelioration than on suppressing fouling. Compared with the stationary membrane, sludging was reduced by an average of 45% compared with only 13% for fouling suppression at the reference flux of 15 L·m−2·h−1 applied. The specific energy demand of the mechanical shear application was calculated as being around 0.0081 kWh·m−3, significantly lower than values reported from a recent pilot scale study on a reciprocated immersed hollow fibre MBR. Whilst results appear promising in terms of energy efficiency, it is likely that the mechanical complexity of applying membrane movement would limit the practical application to low flows, and a correspondingly small number of membrane modules.
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    Industrial effluent treatment with immersed MBRs: treatability and cost
    (IWA Publishing, 2019-09-17) Qiblawey, Hazim; Judd, Simon J.
    A comprehensive OPEX analysis for both municipal and industrial wastewaters has been conducted encompassing energy, critical component (membrane) replacement, chemicals consumption, waste disposal and labour. The analysis was preceded by a review of recent data on industrial effluent treatability with reference to published COD removal data for four effluent types: food & beverage, textile, petroleum and landfill leachate. Outcomes revealed labour costs to be the most significant of those considered, contributing 50% of the OPEX for a 10,000 m3/day capacity municipal wastewater treatment works. An analysis of the OPEX sensitivity to 12 individual parameters (labour cost, flux, electrical energy cost, membrane life, feed COD, membrane cost, membrane air scour rate, chemicals cost, waste disposal cost, mixed liquor suspended solids (MLSS) concentration, recirculation ratio, and transmembrane pressure) revealed OPEX to be most sensitive to labour effort and/or costs for all scenarios considered other than a large (100,000 m3/day capacity) works, for which flux and electrical energy costs were found to be slightly more influential. It was concluded that for small-to-medium sized plants cost savings are best made through improving the robustness of plants to limit manual intervention necessitated by unforeseen events, such as electrical/mechanical failure, foaming or sludging.