Impact of combined oil-in-water emulsions and particulate suspensions on ceramic membrane fouling and permeability recovery

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

Enhancing Oil Removal from Water using Ferric Oxide Nanoparticles Doped Carbon Nanotubes Adsorbents

Oil contaminated water is one of the challenges in water resources management. It is crucial to remove the oil droplets from water in order to meet the discharge regulations set by the environmental authorities. Carbon nanotubes (CNTs) have generated a lot of attention as a new type of adsorbent due to their exceptionally high adsorption capacity for oil–water separation. The high hydrophobicity of CNTs makes them good candidates to enhance the de-oiling process from wastewater. In this study, we have reported the synthesis and evaluation of novel iron-oxide/CNTs nanocomposites for oil–water separation. The CNTs were doped with different loadings of iron oxide nanoparticles using a wet impregnation technique. The synthesized nanocomposite nanomaterials were characterized using field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (TEM), Brunauer, Emmett and Teller (BET) technique, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The effect of adsorption parameters, including, adsorbent dosage, contact time, and agitation speed on the oil removal efficiency were optimized using batch experiments. The sorption capacities of doped CNTs were found to be greater than 7 g/g for gasoline oil. The doped CNTs reached maximum sorption capacity after only 15 min providing one of the fastest minimum contact times reported of all oil sorbent materials. The loading of Fe2O3 nanoparticles on the negative surface of CNT decreases the negative sign and magnitude of the zeta potential by overcoming the repulsive effects of the electrical double layers to allow the finely sized oil droplets to form larger droplets through coalescence. Therefore increasing percentage of the Fe2O3 on the surface of CNT increased the removal of the emulsified oil from the water

Inorganic Membranes: Preparation and Application for Water Treatment and Desalination

Inorganic membrane science and technology is an attractive field of membrane separation technology, which has been dominated by polymer membranes. Recently, the inorganic membrane has been undergoing rapid development and innovation. Inorganic membranes have the advantage of resisting harsh chemical cleaning, high temperature and wear resistance, high chemical stability, long lifetime, and autoclavable. All of these outstanding properties made inorganic membranes good candidates to be used for water treatment and desalination applications. This paper is a state of the art review on the synthesis, development, and application of different inorganic membranes for water and wastewater treatment. The inorganic membranes reviewed in this paper include liquid membranes, dynamic membranes, various ceramic membranes, carbon based membranes, silica membranes, and zeolite membranes. A brief description of the different synthesis routes for the development of inorganic membranes for application in water industry is given and each synthesis rout is critically reviewed and compared. Thereafter, the recent studies on different application of inorganic membrane and their properties for water treatment and desalination in literature are critically summarized. It was reported that inorganic membranes despite their high synthesis cost, showed very promising results with high flux, full salt rejection, and very low or no fouling

Evaluation of the current state and perspective of wastewater treatment and reuse in Qatar

In Qatar, many freshwater resources have already been depleted due to the overconsumption as a result of the population and economic growth. Moreover, due to the lack of sufficient sewage treatment infrastructure, Qatar is facing a daily problem in treating the wastewater. Dumping untreated sewage effluents (SE) contaminates groundwater resources and worsens the current water status in the country. On the other hand, treated SE (TSE), which is estimated at about 0.75 million m3/d, could be one of the main sources of fresh water which can be used in agriculture and industry and even as a source of drinking water in Qatar. Qatar uses only about 27% of TSE in growing fodder (25 million m3/y) and landscape irrigation (1 million m3/y) while about 73% of the total TSE is discharged to septic lagoons to dry or percolate into groundwater (70 million m3/y) and runoff (0.5 million m3/y). Qatar can better utilize its TSE in several applications by further treating the produced TSE. In this paper, a review on the current state and a perspective into the wastewater treatment and reuse in Qatar is presented. Moreover, the main aspects, which should be considered while making a decision on reusing the treated SE in Qatar, are also addressed.Scopu

Effect of operational parameters on distillate flux in direct contact membrane distillation (DCMD): Comparison between experimental and model predicted performance

Membrane distillation (MD) is a thermally driven process where hydrophobic membranes are used to separate saline hot feed solution and cold stream of water and allow water to evaporate due to temperature difference. This work presents a single stage DCMD process using rejected brine from Qatari desalination plants as a feed to augment the production of fresh water. An experimental and theoretical study of a direct contact membrane distillation unit is presented. The work aims to provide a detailed analysis of the simultaneous heat and mass transfer in such systems. The impact of a number of experimental conditions on the performance of the system is presented and compared to simulated results. The predictive models took into account the varying operating conditions (such as temperature, flow rate, flow modes and regimes, etc.). In the formulation of this predictive model, the active membrane area of the MD system was divided into n elements, which are treated as hot and cold control volumes that are related to each other through simultaneous mass and heat transfer. The model presented in this work was in good agreement with the experimental results. The model was able to predict the flux and temperature polarization and was applicable to a large range of experimental conditions and variables.Qatar University and ConocoPhillips GWSC for their financial support of this work under grants QUST-CENG Fall 12/13-22 and QUEX-CWT-11/12-5 respectively.Scopu

A predictive model for the assessment of the temperature polarization effect in direct contact membrane distillation desalination of high salinity feed

Temperature polarization is one of the major sources responsible for flux drop in membrane distillation systems due to the reduction in the driving force across the membrane. The present study offers a predictive model developed for the estimation of the temperature polarization coefficient across the membrane taking into consideration the simultaneous heat and mass transfer phenomena. The uniqueness of the developed model is its ability to predict the intermediate temperatures (temperatures along the flow path of the membrane sheet) which can be used to estimate the local flux and local temperature polarization coefficients as opposed to the methods used by others which estimate the TPC, using the average bulk temperatures, resulting in a tool that enables the estimation of the temperature polarization coefficient (TPC) at different operating conditions. It was found that higher feed temperatures result in higher temperature polarization effect and hence a lower TPC. It was also observed that TPC increases with feed flow rate. The highest TPC value of 0.82 was achieved for a flow rate of 3. L/min and a feed-permeate temperature system of 60-20. The use of flow promoters further enhances the performance of the DCMD system and was reflected on increasing the TPC values (0.66 for a spacer filled channel compared to 0.47 for a spacer free operation) at 1.5. L/min flow condition with 70-30 temperature system. The axially integrated local flux values predicted by the model were in good agreement with the experimentally measured fluxes.Qatar University and ConocoPhillips GWSC for their financial support of this work under grants QUST-CENG Fall 12/13-22 and QUEX-CWT-11/12-5 respectivelyScopu

Reducing Flux Decline and Fouling of direct Contact Membrane Distillation by Utilizing Thermal Brine from MSF Desalination Plant

Fouling and scaling is one of the major challenges in membrane distillation process. This study investigates the utilizing of thermal rejected brine produced from multi-stage flash distillation (MSF) to minimize fouling and scaling on membranes in direct contact membrane distillation (DCMD) settings. The effect of operating parameters on permeate flux and the extent of scaling during long time operation was considered and compared when real seawater and reject thermal brine were used. The deposit morphology of scaling was observed using different analytical methods, including scanning electron microscopy and contact angle measurement. Thermal brine showed enhanced performance in terms of flux and scaling compared to seawater. It was found that flux is reduced by 8% compared to 12-20% when the feed to the DCMD was brine was used as compared to seawater. In addition, thermal brine feed showed better anti-fouling behavior compared to the fresh seawater which contains different organic and inorganic contaminants.Furthermore, utilizing waste heat contained in the thermal brine to raise the temperature of the feed was advantageous in increasing the energy efficiency of DCMD process.The authors would like to express their gratitude to Qatar University and ConocoPhillips GWSC for their financial support of this work under grants QUST-CENG Fall 12/13-22 and QUEX-CWT-11/12-5 respectively

Enhanced Adsorption of Selenium Ions from Aqueous Solution Using Iron Oxide Impregnated Carbon Nanotubes

The aim of this research was to investigate the potential of raw and iron oxide impregnated carbon nanotubes (CNTs) as adsorbents for the removal of selenium (Se) ions from wastewater. The original and modified CNTs with different loadings of Fe2O3 nanoparticles were characterized using high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffractometer (XRD), Brunauer, Emmett, and Teller (BET) surface area analyzer, thermogravimetric analysis (TGA), zeta potential, and energy dispersive X-ray spectroscopy (EDS). The adsorption parameters of the selenium ions from water using raw CNTs and iron oxide impregnated carbon nanotubes (CNT-Fe2O3) were optimized. Total removal of 1 ppm Se ions from water was achieved when 25 mg of CNTs impregnated with 20 wt.% of iron oxide nanoparticles is used. Freundlich and Langmuir isotherm models were used to study the nature of the adsorption process. Pseudo-first and pseudo-second-order models were employed to study the kinetics of selenium ions adsorption onto the surface of iron oxide impregnated CNTs. Maximum adsorption capacity of the Fe2O3 impregnated CNTs, predicted by Langmuir isotherm model, was found to be 111 mg/g. This new finding might revolutionize the adsorption treatment process and application by introducing a new type of nanoadsorbent that has super adsorption capacity towards Se ions

Inorganic Membranes: Preparation and Application for Water Treatment and Desalination

Inorganic membrane science and technology is an attractive field of membrane separation technology, which has been dominated by polymer membranes. Recently, the inorganic membrane has been undergoing rapid development and innovation. Inorganic membranes have the advantage of resisting harsh chemical cleaning, high temperature and wear resistance, high chemical stability, long lifetime, and autoclavable. All of these outstanding properties made inorganic membranes good candidates to be used for water treatment and desalination applications. This paper is a state of the art review on the synthesis, development, and application of different inorganic membranes for water and wastewater treatment. The inorganic membranes reviewed in this paper include liquid membranes, dynamic membranes, various ceramic membranes, carbon based membranes, silica membranes, and zeolite membranes. A brief description of the different synthesis routes for the development of inorganic membranes for application in water industry is given and each synthesis rout is critically reviewed and compared. Thereafter, the recent studies on different application of inorganic membrane and their properties for water treatment and desalination in literature are critically summarized. It was reported that inorganic membranes despite their high synthesis cost, showed very promising results with high flux, full salt rejection, and very low or no fouling