Showing papers in "Desalination and Water Treatment in 2012"

Degradation of wastewaters containing organic dyes photocatalysed by zinc oxide: a review

Abstract: Organic dyes are one of the largest groups of pollutants discharged into wastewaters from textile and other industrial processes. Owing to the potential toxicity of the dyes and their visibility in surface waters, removal and degradation of them have attracted considerable attention worldwide. A wide range of approaches have been developed, amongst which the heterogeneous photocatalysis involving zinc oxide (ZnO) emerges as a promising new route for water purification process. For the first time, we attempt to review and summarize the recent research on ZnO photocatalytic systems for organic dyes degradation. The photocatalysis on modified ZnO is also discussed, in particular aiming at enhancing the degradation efficiency and activity in visible region as well as solar irradiation. The effects of key operational parameters on the photocatalytic performance in terms of the degradation and mineralization of dyes are detailed. This review also highlights the utilization of multivariate analysis to d...

A review of draw solutes in forward osmosis process and their use in modern applications

Abstract: Forward osmosis (FO) is one of the emerging membrane technologies which has gained renewed interest recently as a low energy desalination process. The central to FO process is the draw solution (DS) and the membrane because both play a substantial role on its performance. Hence, the selection of an appropriate DS is crucial for the process efficiency. Many DS have been tested so far for a wide range of modern applications and this paper aims to review the various aspects of the DS in the process performance and provides valuable information regarding the selection criteria of suitable DS. Several general DS properties such as the osmotic pressure and the water solubility can affect the process performance. Other intrinsic properties to specific novel DS such as the emerging magnetic nanoparticles (MNPs) can also have an impact on the process efficiency and have to be evaluated. Separation and recovery of the DS are one of the major challenges facing the development of FO process. The recovery pro...

Heat of adsorption, adsorption energy and activation energy in adsorption and ion exchange systems

Abstract: The heat of adsorption, the adsorption energy and the activation energy are of the most important and frequently calculated parameters in adsorption and ion exchange systems. However, in many occasions these parameters are not clearly defined, appropriate calculated or analyzed in the related literature. A characteristic example is the use of different limits used in order to identify a process as physisorption, chemisorption or ion exchange. The present paper aims at clarifying the nature of these parameters and their interrelationship in theoretical basis and to present the paradigm of ion exchange systems involving zeolites and cations as a case study. All basic theoretical issues are presented, analyzed and discussed with the support of a large number of experimental data in order to draw secure conclusions on several critical issues. In total 46 activation energy, 32 adsorption energy and 34 heat of adsorption experimental values are collected and discussed.

Power generation with salinity gradient by pressure retarded osmosis using concentrated brine from SWRO system and treated sewage as pure water

Abstract: Salinity power generation using hollow fiber modules was examined using the pressure-retarded osmosis (PRO) system between pure water and concentrated brine. Pure water and concentrated brine were supplied from a regional sewage treatment facility and sea water desalination (sea water reverse osmosis [SWRO]) plant. To minimize the effect of the concentration polarization near the membrane surface on the pure water side, the number of open ports in the module was increased from 3 to 4 and that modification was found to be effective because non-permeating pure water, which left the module through fourth port, flushed leaked salt from the brine side through the membrane. Our prototype PRO plant got the maximum output power density, 7.7 W/m2 at a 2.5 MPa hydraulic pressure difference and a 38% permeation of pure water into the brine. To remove the organic foulant in the pure water, a low pressure Reverse Osmosis (RO) membrane and coagulation–sedimentation method with ozonation showed good results. Ho...

Sweep flocculation as a second form of charge neutralisation—a review

Abstract: The coagulation/flocculation (C/F) processes are mainly due to charge neutralisation (CN) and sweep flocculation (SF) mechanisms. However, the SF mechanism has also its CN property moreover than its well-known weighting characteristic. On this weighting characteristic, the literature has usually focused without taking in consideration the SF’s CN property. This review discusses the implicated mechanisms in destabilisation of colloids and aggregation of flocs. Colloids are very small particles that have extremely large surface area. The consequence of this smallness in size and mass and largeness in surface area is that in colloidal suspensions: gravitational effects are negligible and surface phenomena predominate. Hence, during C/F process, colloids are removed by CN and SF mechanisms which act on the anionic charge of the colloid by its neutralisation prior to its removal by sedimentation/filtration. The sweep flocs can be described as large aggregates of Al(OH)3/Fe(OH)3 that are formed when Al...

Characterization of bio-char from pyrolysis of wheat straw and its evaluation on methylene blue adsorption

Abstract: Bio-char, a by-product from the slow pyrolysis of wheat straw, was characterized and investigated as an adsorbent for the removal of cationic dye, methylene blue (MB) from solution. Elemental analysis, Fourier transform infrared spectrum, X-ray diffraction, and pH of point of zero charge (pHpzc) were presented. Adsorption studies were performed at different pH, salt concentration, contact time and dye concentration in the batch mode. The results showed that there were—OH and other functional groups on the surface of bio-char and the pHpzc of the bio-char was 7.8. The value of solution pH 8–9 was best for the MB adsorption quantity. Salt that coexisted in solution was not favored in MB adsorption. The equilibrium data were modeled with Langmuir, Freundlich, and Sips equations. Overall, the data were best fitted with the Sips model. The maximal adsorption capacity from the Sips model was 12.03 ± 0.41 mg/g at 293 K. Thermodynamic parameters were calculated and the results show that the process was s...

Modification of activated carbon by the alkaline treatment to remove the dyes from wastewater: mechanism, isotherm and kinetic

Abstract: The present paper investigates the surface modification of activated carbon (AC) by alkaline (NaOH) and dye removal ability of the surface modified activated carbon (SMAC). Acid Red 14 (AR14) and Acid Blue 92 (AB92) were used as the dye models. The surface characteristics of SMAC were investigated using the Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and surface area. The possible mechanism of the adsorption process and dye interaction with SMAC surface was analyzed. The effects of adsorbent dosage, initial dye concentration, and pH on the dye removal were investigated. The isotherm and kinetic of dye adsorption were studied. The adsorption isotherm of the dyes onto AC and SMAC followed Langmuir and Freundlich isotherms, respectively. The kinetic of dyes onto both AC and SMAC followed pseudo-second-order kinetic model. The results indicated that the alkaline (NaOH) treatment of AC was an efficient method to modify the AC. The maximum adsorption capacity (Q max) of AR14 ...

Direct contact membrane distillation for seawater desalination

Abstract: Membrane distillation (MD) is a non-isothermal membrane separation process. It is based on the phenomenon that pure water in its vapor state can be extracted from aqueous solutions, with vapor passing through a hydrophobic microporous membrane when a temperature difference is established across it. In this work, three commercially available hydrophobic microporous membranes were used for seawater desalination via direct contact MD. The effects of pertinent operating parameters on the permeation flux have been studied. A plate and frame module was used for seawater desalination. Long-term performance evaluation was carried out to evaluate the process as a stand-alone desalination alternative. The results indicated that polytetrafluoroethylene membrane had the best performance when a hot feed temperature of 80°C with 800 ml/min flow rate was used. At optimum condition a 99.99% salt rejection was achieved.

Modelling the Reverse ElectroDialysis process with seawater and concentrated brines

Abstract: Technologies for the exploitation of renewable energies have been dramatically increasing in number, complexity and type of source adopted. Among the others, the use of saline gradient power is one of the latest emerging possibilities, related to the use of the osmotic/chemical potential energy of concentrated saline solutions. Nowadays, the fate of this renewable energy source is intrinsically linked to the development of the pressure retarded osmosis and reverse electrodialysis technologies. In the latter, the different concentrations of two saline solutions is used as a driving force for the direct production of electricity within a stack very similar to the conventional electrodialysis ones. In the present work, carried out in the EU-FP7 funded REAPower project, a multi-scale mathematical model for the Salinity Gradient Power Reverse Electrodialysis (SGP-RE) process with seawater and concentrated brines has been developed. The model is based on mass balance and constitutive equations collecte...

Removal of textile dyes from aqueous solutions with eco-friendly biosorbent

Abstract: Inexpensive and eco-friendly biosorbent wheat bran has been successfully utilized for the removal of textile dyes from aqueous solutions. Remazol Red F3B (Reactive red 180) was initially used as a model textile dye. The effects of contact time, pH, initial dye concentration, biosorbent dose and temperature were investigated. The optimum biosorption conditions were found as following: contact time 4 h, initial pH 2.0, initial dye concentration 200 mg/l, biosorbent dose 0.25 g and temperature 20°C. The results indicate that acidic pH supported the biosorption of dyes on the wheat bran. The biosorption capacity was 39.42 mg/g for this dye. Using optimum biosorption conditions, five other dye types with reactive, direct and acidic structures were also investigated for biosorption capacity. The Langmuir and Freundlich models were evaluated using the experimental data and the experimental results showed that the Langmuir equation fit better than the Freundlich equation. Different thermodynamic paramete...

Recent developments and future challenges of forward osmosis for desalination: a review

Abstract: This article focuses on the recent developments of forward osmosis (FO) for desalination and the challenges it faced. Issues discussed include membrane, configuration, draw solution, integration with post-treatment, and energy and economic evaluation. In spite of the potential advantages of FO, there exist a number of technical barriers that impede FO’s application for water desalination. Further membrane development is needed to give high water flux, low reverse solute flux and material stability over the operating pH range. It is currently not economically viable to use NaCl as the draw solute for municipal scale FO desalination in view of the solute loss through the membrane. Progress in post-treatment is also needed, because FO cannot stand as a single process, but has to be integrated with a post treatment to regenerate draw solution and produce desalinated water that meets the required standards. A FO–RO process is technically feasible, but economically unviable due to energy consideration....

Kinetics of the batch adsorption of methylene blue from aqueous solutions onto rice husk: effect of acid-modified process and dye concentration

Abstract: In this study, adsorption of methylene blue (MB) dye onto clean rice husks (CRH) and acid-modified CRH was investigated with respect to the contact time, MB concentrations, acid concentrations and acid types used in the acid modification processes. The results indicate that the acid modification process reduces the MB sorption efficiency from 98% for CRH to 67% for NRH (nitric acid treated rice husk), 59% for HRH (hydrochloric acid treated rice husk) and 55% for SRH (sulfuric acid treated rice husk). In order to investigate the adsorption mechanisms, four kinetic models, i.e., pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models were fit to the experimental results. The characteristic parameters and correlation coefficients for each kinetic model were determined. The fits of the kinetic results from the kinetic equations were compared with the experimental data. The results indicate that the acid modification process changes the MB adsorption mechanism. Langmuir, Fr...

The biofilm membrane bioreactor (BF-MBR)—a review

Abstract: Membrane bioreactors (MBR) based on the activated sludge process is a relatively new technology, with implementation worldwide increasing over the last 20 y. In parallel to commercial development, a lot of research work has been done in fundamental studies, development and optimization of this technology. Although the main focus has been on activated sludge processes, several research groups have been investigating biofilm based MBR systems. The biofilm processes have several advantages over activated sludge process and can be used as complementary, assisted to activated sludge MBR (aBF-MBR) or self standing, pure biofilm based MBRs (pBF-MBR). This article reviews the status of MBR technology with biofilm implementations for wastewater treatment, excluding membrane aerated/supported biofilm reactors (MABR). Reports published within the last 10 y are reviewed with respect to aBF-MBR and pBF-MBR studies, highlighting advantages proposed of this approach over activated sludge MBRs, identifying perfo...

CFD analysis of the fluid flow behavior in a reverse electrodialysis stack

Abstract: Salinity Gradient Power by Reverse Electrodialysis (SGP-RE) technology allows the production of electricity from the different chemical potentials of two differently concentrated salty solutions flowing in alternate channels suitably separated by selective ion exchange membranes. In SGP-RE, as well as in conventional ElectroDialysis (ED) technology, the process performance dramatically depends on the stack geometry and the internal fluid dynamics conditions: optimizing the system geometry in order to guarantee lower pressure drops (ΔP) and uniform flow rates distribution within the channels is a topic of primary importance. Although literature studies on Computational Fluid Dynamics (CFD) analysis and optimization of spacer-filled channels have been recently increasing in number and range of applications, only a few efforts have been focused on the analysis of the overall performance of the process. In particular, the proper attention should be devoted to verify whether the spacer geometry optimi...

Prediction of optimum adsorption isotherm: Comparison of chi-square and Log-likelihood statistics

Abstract: A comparison of chi-square (X 2) and Log-likelihood (G 2) statistics of 19 adsorption isotherm models—seven two-parameter models (Langmuir, Freundlich, Dubinin–Radushkevich, Temkin, Jovanovic, Harkins–Jura and Halsey) and 12 three-parameter models (Koble–Corrigan, Langmuir–Freundlich, Toth, Redlich–Peterson, Radke–Prausnitz (three models), Fritz–Schlunder, Jossens, Khan, UNILAN, Vieth–Sladek) have been applied to the experiment of two dyes (Acid Blue 113, Acid Black 1) sorption onto Granular PineCone derived Activated Carbon (GPAC) and three dyes (Acid Blue 80, Acid Red 114, Acid Yellow 117) sorption onto Granular Activated Carbon type Filtrasorb 400 (GAC F400). The study has focused on the assessment of the adequacy and goodness of the fitted models, using two well-known—X 2 and G 2—statistics. The results showed that G 2 could be better than X 2 statistic when the number of model parameters is three.

Adsorption of congo red onto activated carbons having different surface properties: studies of kinetics and adsorption equilibrium

Abstract: To enhance congo red (CR) removal from aqueous solution, activated carbons prepared from date pits and modified by oxidation with nitric acid followed by heat treatment in a nitrogen atmosphere were tested. Kinetic and equilibrium adsorptions data of CR from aqueous solution were carried out, showing that the elimination of oxygen surface groups from activated carbon by heat treatment enhanced the adsorption capacity. The adsorption followed pseudosecond order kinetics. The experimental isotherms were analysed with two and three parameters equations (Freundlich, Langmuir, and Redlich–Peterson) using non-linear regression. The results showed that the Langmuir and Redlich–Peterson isotherms best-fit the equilibrium data, with maximum adsorption capacity of 105 mg/g calculated from Langmuir equation. The mechanism adsorption of this anionic dye on activated carbons involved electrostatic and dispersive interactions.

Photocatalytic removal of Cr(VI) and Ni(II) by UV/TiO2: kinetic study

Abstract: In this study, photocatalytic removal of Cr(VI) and Ni(II) by illuminated TiO2 was investigated with variation of solution pH, contact time, TiO2 dosage and initial Cr(VI) and Ni(II) concentration. From the photocatalytic reaction, near complete elimination of Cr(VI) and Ni(II) occurred from the adsorption of Cr(VI) and Ni(II) on the surface of TiO2 as well as reduction of Cr(VI) and Ni(II) to Cr(III) and Ni(0), respectively. Reduction was recognized as a significant elimination process for the treatment Cr(VI) and Ni(II) from wastewater. Removal of Cr(VI) decreased with increasing pH while removal of Ni(II) increased with increasing pH. TiO2 dosage was also an important parameter for the removal of Cr(VI). As the TiO2 dosage increased up to 1 g l−1, removal of Cr(VI) and Ni(II) was continuously enhanced.

Status of adsorptive removal of dye from textile industry effluent

Abstract: Textile industry is the key user of dyes and hence the prime source of water pollution, which risks aquatic as well as human life. There are various physical, chemical, and biological methods for dye removal, but most convincing is adsorption due to its simplicity. The extensive research has been carried out in this field which has brought a wide range of adsorbents in reach of industries. Freshly obtained off beat adsorbents in addition to direct one present have been used. The present paper aims at the broad classification of adsorbents recently introduced to the arena. The division of adsorbents comprises conventional means like activated carbon (commercial and derived), zeolite, and other nonconventional adsorbents as natural material, wastes, or even especially designed adsorbents, which are inexpensive and clean to use. Also, the investigations done regarding adsorption lately have been compared with respect to their results. The efficacy of each operation is under grave discussion. Up to 9...

UV-assisted photocatalytic synthesis of TiO2-reduced graphene oxide with enhanced photocatalytic activity in decomposition of sarin in gas phase

Abstract: TiO2-reduced graphene oxide (RGO) composite are successfully prepared by UV-assisted photocatalytic reduction of graphite oxide by TiO2 nanoparticles in ethanol. These nanocomposites prepared with different ratios of graphene oxide (GO) were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectroscopy, UV–vis absorption spectrophotometer (UV–vis), and X-ray photoelectron spectroscopy. Photocatalytic degradation of nerve agent, isopropyl methylphosphonfluroride, Sarin (GB) as a real Chemical Warfare Agent on nanocomposites have been studied using Gas chromatography/mass spectrometry analysis in ambient atmosphere. RGO-TiO2 nanocomposites exhibited much higher photocatalytic activity than TiO2 for degradation of GB under visible light irradiation.

Decolorization of Sunzol Black DN conc. in aqueous solution by Fenton oxidation process: effect of system parameters and kinetic study

Abstract: The decolorization of Sunzol Black DN conc. (SBDN) in aqueous solution by Fenton oxidation process was studied. The effects of different reaction parameters such as initial hydrogen peroxide concentration ([H2O2]o), initial Fe2+ concentration ([Fe2+]o), pH, temperature and the initial SBDN concentration ([SBDN]o) on the decolorization of the SBDN dye have been investigated. The optimal reaction conditions were experimentally determined and it was found to be [H2O2]o = 4 mM, [Fe2+]o = 0.05 mM, pH = 3.5 and [SBDN]o = 100 mg/l at temperature 30°C. Under optimal condition, 94.5% decolorization efficiency of dye in aqueous solution was achieved within 90 min of reaction. The decolorization kinetics of SBDN by Fenton oxidation process followed the second-order reaction kinetics, and the apparent activation energy, was found to be 38.582 kJ/mol.

Oxidized multiwalled carbon nanotubes for the removal of methyl red (MR): kinetics and equilibrium study

Abstract: Oxidized multiwalled carbon nanotubes (MWCNT) were used for the removal of methyl red (MR) from aqueous solutions. The effects of variables, such as initial solution pH, initial dye concentration, temperature, and sorption time, on MR removal were studied and optimized. Fitting the experimental equilibrium data to various investigated isotherm models, such as Langmuir, Freundlich, Tempkin, and Dubinin–Radushkevich (D–R) models, showed the suitability of the Langmuir model with the highest correlation coefficients. The calculated thermodynamic parameters indicated that the removal of MR by MWCNT is an entropy-driven and endothermic process. The experimental data were analyzed by different kinetic models, such as pseudo-first order, pseudo-second order, and Elovich and intraparticle diffusion models. It was found that the second-order equation and intraparticle diffusion models are the rate-limiting factor and control the kinetic of the adsorption process.

Augmentation of the basin type solar still using photovoltaic powered turbulence system

Abstract: The present paper concerns with enhancing productivity of basin type solar still through experimental investigation. Therefore, two solar stills are designed and constructed to study the performance of two suggested solar desalination systems. The first one is a conventional still and the second is a modified still uses a rotating fan with a vertical shaft. A DC-motor powered by a small photovoltaic (PV) system is used to rotate the fan. The influence of the rotational speed of the fan and the depth of saline water on the performance of the still is investigated experimentally. The experiments were conducted with fan rotational speeds of 30, 35, 40 and 45 rpm and saline water depths of 1, 3, 5 and 7 cm. The results indicate that the daily productivity of still increases with increasing rotational speed of the fan and the maximum difference of daily productivity between fan and conventional solar stills is achieved at depth of saline water of 3 cm (with rotation). Also it is found that using rotat...

Adsorption of Fe(II) ions from aqueous phase by chitosan adsorbent: equilibrium, kinetic, and thermodynamic studies

Abstract: The aim of present study was to investigate the adsorption properties of chitosan for the removal of Fe(II) ions from aqueous phase in a batch equilibrium system. The effects of adsorbent dose, initial pH, concentration, and temperature of the solution on adsorption were investigated. Adsorption experiments were carried out at initial concentration range of 10–50 mg l−1 in a temperatures range of 20–40°C. The adsorption isotherm data were well fitted with Langmuir–Freundlich model. The kinetics of Fe(II) on chitosan followed the nonlinear form of pseudo-first-order model and the model parameters were confidently recovered. The examination of kinetic data also revealed that the adsorption rate was dominated by intraparticle diffusion mechanism. The calculated negative values of standard Gibbs free energy and enthalpy changes confirmed the spontaneous and exothermic nature of Fe(II) adsorption on chitosan adsorbent. Finally, chitosan showed to be a good potential adsorbent for removing Fe(II) ion f...

Annual performance of evacuated tubular collector integrated solar still

Abstract: Evacuated tubular collector (ETC) and solar still (SS) are two solarthermal technologies for heating and purification of water, respectively. ETC stores water at high temperature whereas SS requires heated water for increased evaporation as well as yield. In this paper, an active solar thermal system “evacuated tubular collector integrated solar still (EISS)” (ETC and SS are integrated together) has been analyzed for its annual (January–December 2008) experimental performance for the composite climatic condition of New Delhi, India. The EISS system has been designed to recover the heat loss (which occurs from the ETC’s hot water during off-sunshine hours) in the form of distilled water by evaporation–condensation process in SS. Hence, the EISS system provides both hot water as well as potable (distilled) water. The main purpose of the present analysis is to develop a thermal model of EISS, its validation with experimental results, economic analysis, and to compare the performance of EISS with the...

Removal of lead (II) ions from aqueous solution by using crosslinked chitosan-clay beads

Abstract: A simple and effective biodegradable material known as chitosan-clay composite beads were prepared to remove Pb(II) ions from aqueous solution. For this purpose, various important parameters such as contact time, pH and temperature were examined on the adsorption of Pb(II) ions onto crosslinked chitosan-clay composite beads. Maximum adsorption capacity of Pb(II) was observed at pH 4.5 and 25°C and calculated as 7.93 mg/g according to Langmuir isotherm model. Thermodynamic parameters namely ΔG°, ΔH° and ΔS° of the Pb(II) adsorption process have been calculated as 7.889 kJ/mol, −15.131 kJ/mol and −0.0785 kJ/molK respectively. EDTA was the best eluent for the desorption of Pb(II) ions from the crosslinked chitosan-clay beads. Scanning electron microscope (SEM) was used to characterize the surface morphology of the crosslinked chitosan-clay beads.

Photocatalytic removal of Cr(VI) with illuminated TiO2

Abstract: The effect of dissolved oxygen on the photocatalytic reduction of Cr(VI) with illuminated TiO2 was studied in this work with variation of the solution pH, contact time, and initial Cr(VI) concentration. Oxygen or nitrogen gas was used as a purging gas. Overall, the removal efficiency of Cr(VI) decreased as the solution pH increased. The removal of Cr(VI) by UV/TiO2 increased by decreasing the solution pH because of the increased potential difference between the conduction band of TiO2 and Cr(VI)/Cr(III) as well as the anionic-type adsorption of Cr(VI) onto the TiO2 surface. The removal efficiency of Cr(VI) increased in purging of nitrogen gas compared to that of oxygen gas because of less competition between dissolved oxygen and Cr(VI) in the reaction with the electron in the conduction band of TiO2. The reduction pattern was better described by the first-order kinetic model.

Techno-economic analysis of combined concentrating solar power and desalination plant configurations in Israel and Jordan

Abstract: Combined concentrating solar power (CSP) and desalination plants represent a realistic future option for the production of electricity and fresh water for countries of the world’s sunbelt. In this paper, parabolic trough power plants for electricity production have been analysed in combination with multi-effect distillation (MED) and ultrafiltration/reverse osmosis (RO) desalination plants for two sites in Israel (Ashdod) and Jordan (Aqaba). Both RO and MED desalination plants were designed for a fresh water production capacity of 24,000 m3/d. The power block of the CSP plant was selected to meet the steam consumption of the MED plant at the design point, which led to a gross electrical power generation capacity of the power block of 42 MWel. Due to the low availability and generally high cost of coastal land, the CSP + RO plant consists of two separate units. It was assumed that the CSP plant is located at an inland location where there is land available. The RO plant is located at the sea, whil...

On the concept of the future drinking water treatment plant: algae harvesting from the algal biomass for biodiesel production—a review

Abstract: It is well established that the drinking water treatment has several disadvantages such as it may rupture the algae, thereby releasing the taste- and odour-producing oils before the whole algae are removed from the treatment system. This review aims to present the concept of algae recovery instead of its removal in drinking water treatment plant. Control of algae in water supplies and some coagulation/flocculation and electrolysis experiments as harvesting methods are discussed. In fact, algae recovery instead of its removal in water treatment plant is a promising perspective and a suitable issue when the surface water comes from dams where algae blooms occur frequently. Micro-algae are a sustainable energy resource with great potential for CO2 fixation. The micro-algae could be grown in photo-bioreactors or in open ponds. A new interesting field of research would be fast and simultaneous algal biodiesel production with drinking water treatment in the biodiesel production/water treatment plant wi...

CFD simulation of channels for direct and reverse electrodialysis

Abstract: Flows within very thin channels, typically filled with spacers, can be often encountered in many processes such as electrodialysis (ED) and reverse electrodialysis (RED). Although the ED and the RED processes have been studied for a long time, the optimization of the fluid dynamics within the channels is still an open problem. In the present work, realized within the EU-FP7 funded REAPower project, computational fluid dynamics simulations were carried out in order to predict the fluid flow field inside a single ED/RED channel. Some different configurations were tested which includes: an empty channel, a channel provided with a spacer, and a channel filled with a purposely manufactured fiber porous medium. Two types of spacers were investigated: (1) a commercial type made of woven perpendicular filaments and (2) an overlapped perpendicular filament spacer. A sensitivity analysis concerning computational grid size and topology was performed. For the cases investigated, adopting the hybrid grids mai...

Oily wastewater treatment using mullite ceramic membrane

Abstract: This paper presents performance of a microfiltration (MF) ceramic membrane for treatment of oily wastewaters. Mullite MF membranes were synthesized from kaolin clay. The effects of different operating parameters such as pressure (0.5–4 bar), volumetric flow rate (0–2 m/s), temperature (15–55°C), oil concentration (250–3000 ppm) and salt concentration(0–200 g/l) on permeate flux (PF), fouling resistance (FR), fouling and rejection (R) were investigated. In order to determine the best operating conditions, 250–3000 ppm condensate gas in water emulsions were employed as synthetic feed. The rejection of total organic carbon (TOC) for the synthetic feeds was found to be more than 94%. The results show that by increasing temperature and pressure, the PF increases. Also, by increasing oil content and salt concentration, the membrane is fouled rapidly and the PF decreases. At low salt concentration (0–25 g/l), PF increases with increasing salt concentration, but at high salt concentration (25–200 g/l), i...