Forward Osmosis Process for the Treatment of Wastewater from Textile Industries

The research aims to use a new technology for industrial water concentrating that contains poisonous metals and recovery quantities from pure water. Therefore, the technology investigated is the forward osmosis process (FO). It is a new process that use membranes available commercial and this process distinguishes by its low cost compared to other process. Sodium chloride (NaCl) was used as draw solution to extract water from poisonous metals solution. The driving force in the FO process is provided by a different in osmotic pressure (concentration) across the membrane between the draw and poisonous metals solution sides. Experimental work was divided into three parts. The first part includes operating the forward osmosis process using TFC membrane as flat sheet for NaCl. The operating parameters studied were: draw solutions concentration (10 – 95 g/l), draw solution flow rate (12-36 I/h), temperature of draw solution (30 and 40°C), feed solution concentration (10 -210 mg/l), feed solution flow rate (10 -50 l/h), temperature of feed solution (30 and 40°C) and Pressure (0.4 bar). The second part includes operating the forward osmosis process using CTA membrane as flat sheet for NaCl. The operating parameters studied were: draw solution concentration (15 – 95 g/l), feed solution concentration (10-210 mg/l). Constant temperature was maintained at 30°C. The last part includes operating the reverse osmosis process using TFC membrane as spiral wound module in order to separate NaCl salt from draw solution and obtain on pure water so as to usefully in different uses and also obtain on solution of NaCl concentrate which was recirculated to forward osmosis process. It is then used as draw solution. The operating parameter studied was: feed solution flow rate (15-55 l/h). The experimental results show that the water flux increases with increasing draw solution concentration, feed solution flow rate, temperature of draw solution and decreases with increasing feed solution concentration, draw solution flow rate and temperature of feed solution. The experiments also show that CTA membrane gives higher water flux than TFC membrane for forward osmosis operation.

In this study, the feasibility of Forward–Reverse osmosis processes was investigated for treating the oily wastewater. The first stage was applied forward osmosis process to recover pure water from oily wastewater. Sodium chloride (NaCl) and magnesium chloride (MgCl2) salts were used as draw solutions and the membrane that was used in forward osmosis (FO) process was cellulose triacetate (CTA) membrane. The operating parameters studied were: draw solution concentrations (0.25 – 0.75 M), oil concentration in feed solution (FS) (100-1000 ppm), the temperature of FS and draw solution (DS) (30 - 45 °C), pH of FS (4-10) and the flow rate of both DS and FS (20 - 60 l/h). It was found that the water flux and oil concentration in FS increase by increasing the concentration of draw solutions, the flow rate of FS and the temperature for a limit (40oC), then, the water flux and oil concentration decrease with increasing the temperature because of happening the internal concentration polarization phenomenon. By increasing the oil concentration in FS and the flow rate of the DS, the water flux and oil concentration in FS decreased, while it had a fluctuated behavior with increasing pHof oily wastewater. It was found also that MgCl2 gives water flux higher than NaCl. So the values of resistance to solute diffusion within the membrane porous support layer were 55.93 h/m and 26.21 h/m for NaCl and MgCl2 respectively. The second stage was applied reverse osmosis process using polyamide (thin film composite (TFC)) membrane for separating the fresh water from a diluted (NaCl) solution using different parameters such as draw solution concentration (0.08–0.16 M), feed flow rate (20–40 l/h).

The present work aims to study forward osmosis process using different kinds of draw solutions and membranes. Three types of draw solutions (sodium chloride, sodium formate, and sodium acetate) were used in forward osmosis process to evaluate their effectiveness with respect to water flux and reverse salt flux. Experiments conducted in a laboratory-scale forward osmosis (FO) unit in cross flow flat sheet membrane cell. Three types of membranes (Thin film composite (TFC), Cellulose acetate (CA), and Cellulose triacetate (CTA)) were used to determine the water flux under osmotic pressure as a driving force. The effect of temperature, draw solution concentration, feed and draw solution flow rate, and membrane types, were studied with respect to water flux. The results showed an increase in water flux with increasing feed temperature and draw solution concentrations In addition, the flux increased with increasing feed flow rate while the flux was inversely proportional with the draw solution flow rate. The results showed that reverse osmosis membranes (TFC and CA) are not suitable for using in FO process due to the relatively obtained low water flux when compared with the flux obtained by forward osmosis membrane (CTA). NaCl draw solution gave higher water flux than other draw solutions and at the same time, revealed higher reverse salt flux.

Water is crucial for enhancing the yield of agricultural land to meet the growing demand. Forward osmosis (FO) is a developing technology that utilizes the natural osmotic gradient of solutions. In this study, fertilizer drawn FO setup was considered by using potassium chloride (KCl) as the draw solution (DS) for treating textile wastewater as the feed solution (FS). This study investigated the effects of FS temperature, pH, and FS and DS concentrations. The performance investigation involved the study in terms of water flux, reverse salt flux, and specific reverse salt flux. DS and FS properties, osmotic potential, and temperature played a vital role in the performance. At 30°C FS temperature, the highest water flux (5.5 LMH) was observed. Reverse salt flux increased due to the increase in solute diffusivity. The highest value of water flux was obtained at a DS of 1.150 M and FS of 1000 mg/L. The permeation of water improved due to the difference in DS and FS concentrations at pH values above 7. The results of this study suggest that KCl as DS has a higher potential for the treatment of textile wastewater at a temperature of 30°C. Additionally, the functional groups attached to the FO membrane were identified through Fourier-transform infrared (FTIR) spectroscopic study. PRACTITIONER POINTS: Treatment of textile wastewater with the use of fertilizer draw solution (KCl) by forward osmosis process as carried out. The performance was assessed in terms of water flux, reverse salt flux, and specific reverse salt flux. The effects of feed and fertilizer draw solution concentrations; pH and temperature were evaluated on the performance of FO process.

Evaluation of forward osmosis as a pretreatment process for multi stage flash seawater desalination

This dissertation studies the feasibility and efficiency of utilizing forward osmosis membrane technology to treat heavy metal contaminated water. Arsenic is selected to be the target heavy metal. The evaluation of forward osmosis(FO)process efficiency is based on two important membrane parameters, which are water flux and rejection rate. Water flux is the indicator of production rate or treatment efficiency in quantity aspect. Rejection rate represents the product water quality in terms of the percentage of target heavy metal rejected by the membrane. The major objective of this dissertation is to find optimal draw solution and membrane type to achieve maximum arsenic removal efficiency (rejection rate), at the same time, maintain high water flux.
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\nSeveral sub-projects with individual experiment are derived from the main objective to test out the performance of different membranes and draw solutions. The relationship between draw solution concentration and water flux is analyzed as well. Cellulose triacetate (CTA) membrane and thin film composite (TFC) membrane as two types of commonly available polymer membrane are used for the experiments. In total, four types of inorganic and organic solutes are included in the comparison of draw solution performance. Lab-scale FO system and one unit of membrane module are adopted for conducting the experiments.
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\nThe result shows that using sodium chloride as draw solution and TFC membrane yields the largest flux. For the aspect of rejection rate, both CTA membrane and TFC membrane can reach almost 100% treatment efficiency. The rejection rates obtained in this study fall in the range of 96.7% to 99.9%. The results of this study proved that forward osmosis membrane process has the potential of industrial application in treating heavy metal contaminated water such as industrial wastewater and landfill leachate.

The research aims to apply the novel forward osmosis (FO) process to recover pure waterfrom contaminated water. Phenol was used as organic substance in the feed solution, while sodiumchloride salt was used as draw solution. Membranes used in the FO process is the cellulosetriacetate (CTA) and polyamide (thin film composite (TFC)) membrane. Reverse osmosis processwas used to treatment the draw solution, the exterior from the forward osmosis process. In the FOprocess the active layer of the membrane faces the feed solution and the porous support layer facesthe draw solution and this will show the effect of dilutive internal concentration polarization andconcentrative external concentration polarization.In the FO process was a run-time for five hours, and the concentration of phenol 100 and1000 mg/l, and for the NaCl the concentration was 10000 and 30000 mg/l. It was found thatrecovery percent increases with increasing time, while water flux through membrane decreases withincreasing time. Also, it was found that recovery and water flux increases with increasing drawsolution concentration, on the contrary, water flux and the percentage of recovery decreases withincreasing the concentration of phenol (feed solution). Increase in draw solute (NaCl) concentrationhas more effect on the water flux in FO process compared with increase in the concentration ofphenol. Outlet phenol concentration increases with time, while the outlet salt concentrationdecreases with increasing the time. The results showed that the cellulose triacetate membrane gavethe highest recovery ratio from the thin film composite membrane. The highest recovery wasreached in five hours is 51.33%, while using CTA membrane recovery rate increase, by 23%compared with TFC membrane. The value of the resistance to solute diffusion within the membraneporous support layer is 36.83 h/m. Reverse osmosis is perfect method for removal of dissolved saltsfrom water, thus its suitable process for reducing the content of NaCl in draw solution; therefore thesodium chloride rejection percentage was 91.6 – 96 % for polyamide membrane (TFC). Within twohours of work of the reverse osmosis system the recovery percentage of pure water is 58%.

Forward osmosis (FO) is an emerging membrane separation technology. It is different from the well-studied pressure-driven membrane separation processes. The FO process is based on water transport under an osmotic pressure difference across a semi-permeable membrane. The distinct operating conditions lead to unique technical challenges during the exploitation of FO technology. According to a comprehensive literature investigation, one of the stringent barriers is lacking of effective FO membranes. The objectives of this research were to develop high performance FO membranes, and furthermore, to systematically study the mass transport and the governing mechanisms in FO process. Thin film composite (TFC) FO membranes with a tailored support structure were developed in this study. The membranes consisted of a highly porous substrate with finger-like pore structure, which was prepared via phase inversion, and a polyamide rejection layer synthesized by interfacial polymerization. The TFC FO membranes had small structural parameters due to the thin cross-section, low tortuosity, and high porosity of the substrates. The membrane rejection layers exhibited superior separation properties (higher water permeability and excellent selectivity) relative to commercial FO membranes. Under FO testing conditions, these membranes achieved high water flux while maintaining relatively low solute reverse diffusion. Comparison of the synthesized TFC FO membranes with commercial FO and reverse osmosis (RO) membranes revealed the critical importance of the substrate structure, with a straight finger-like pore structure preferred over a spongy pore structure to minimize internal concentration polarization (ICP), a unique and critical problem resulting in low water flux in the osmotically driven membrane processes. In addition, membranes with high water permeability and excellent selectivity are preferred to achieve both high FO water flux and low solute flux. The results proved that TFC membranes with a tailored porous substrate and rejection layer are promising for FO applications. In the study of polyamide rejection layer synthesis, the influence of monomer concentrations (i.e., m-phenylenediamine (MPD) and trimesoyl chloride (TMC) concentrations) on the membrane separation properties as well as the FO performance was systematically investigated. A strong trade-off between the water permeability and salt rejection of the membranes was observed, where reducing the MPD concentration or increasing the TMC concentration may result in a higher membrane permeability but a lower salt rejection. In FO tests, membranes with poor salt rejection had severe solute reverse diffusion, which enhanced the severity of ICP. It was found that the FO water flux was governed by both the membrane water permeability and solute rejection. For a membrane with higher water permeability but lower solute rejection, the reduced membrane frictional resistance was compensated simultaneously by the more severe solute-reverse-diffusion-induced ICP. The net effect on the FO water flux depends on the competition of these two opposing mechanisms. Under conditions where solute reverse diffusion may cause severe ICP (e.g., high draw solution concentration and high water flux level), membranes need to be optimized to achieve a high salt rejection even if this is at the expense of lower water permeability. In view of the importance of the water permeability and salt permeability on FO performance, a systematic comparison study of prevailing semi-permeable FO membranes with nanofiltration (NF)-like and RO-like separation properties in terms of flux performance and fouling behavior was conducted. Due to the crucial influence of solute reverse diffusion on FO water flux, the high-rejection RO-like FO membranes generally performed better than the NF-like counterparts in sodium chloride based FO tests. On the other hand, the high permeability of NF-like FO membranes could achieve higher water flux, when proper draw solutes were used to minimize draw solute leakage. Fouling tests suggested that the NF-like TFC FO membranes tended to be more fouling resistant due to their relatively smooth membrane surface. This work further elucidated the major mechanisms that govern the FO performance. These mechanisms were summarized as a frictional resistance loss mechanism (MR), solute-reverse-diffusion-induced ICP (MICP-Js), concentration of feed solutes (concentrative ICP or MICP-feed in the active-layer-facing-draw-solution orientation) and dilution of draw solutes (dilutive ICP or MICP-draw in the active-layer-facing-feed-solution orientation). These mechanisms are related to the properties of membrane, draw and feed solutions. This work led to a set of systematic criteria for the selection of FO membranes, draw solution and optimization of other operating conditions, of which the practicability was demonstrated in potential FO applications.

Pressure retarded osmosis for power generation and seawater desalination: Performance analysis

Forward osmosis (FO) is a membrane process that occurs when solutions of different osmotic pressures are separated by a membrane which is selectively permeable to water. It is a process that drives water permeation across the membrane spontaneously even in the absence of hydraulic pressure difference across the membrane. FO has attracted lots of attention over the last decade and has been explored as a potential alternative to desalination, wastewater treatment and liquid food processing. Significant progress has been made in the development of high-performance FO membranes with high water flux and low reverse solute flux, particularly cellulosic membranes, thin-film composite (TFC) membranes and polyelectrolyte-based membranes. Yet, a few major challenges continue to hamper the widespread implementation of the process in the industry, mainly internal concentration polarization, reverse solute diffusion, membrane fouling, mechanical durability and draw solution regeneration. Most of these challenges are associated with membrane characteristics, which has significantly limited the efficiency of the FO process. To address these challenges, firstly, hollow fiber ultrafiltration membranes were fabricated from polyethersulfone (PES) via a non-solvent induced phase separation (NIPS) process and were used as substrates to prepare inner-selective TFC hollow fiber membranes via an interfacial polymerization (IP) process. The effect of the hollow fiber substrate fabrication conditions on the properties of the substrate and TFC membranes were briefly investigated. The FO performance of the TFC membranes were characterized by using 0.5 M NaCl and DI water as the draw and feed solutions. when the membrane was operated in the active layer-facing-feed solution (AL-FS) and active layer-facing-draw solution (AL-DS) configurations, water flux as high as 41.2 L/m2/h and 74.9 L/m2/h were achieved, while specific reverse solute flux were 0.11 g/L and 0.10 g/L, respectively. Subsequently, a novel double-skinned hollow fiber TFC FO membrane has been successfully fabricated. The FO membrane consisted of a one-step dual-layer substrate and a thin inner selective layer formed via the IP process. The substrate comprises a dense ultrafiltration (UF) outer layer and a relatively porous UF inner layer, both of which were constructed from PES by using a dual-layer co-extrusion technique. The fouling resistance of the double-skinned hollow fiber membrane was evaluated under various testing conditions to verify the viability of double-skinned hollow fiber membranes as a solution to membrane fouling in the FO process. Compared to the commercial and reported double-skinned FO membranes, the FO membrane developed in this thesis exhibited a higher permeate flux with humic acid solution as a feed solution. Furthermore, the double-skinned FO membrane was applied in concentrating activated sludge using 0.5 M NaCl as a draw solution. A permeate flux at 5.4 L/m2/h was achieved after 5-hour operation, which was higher than, or comparable to, those of the reported FO membranes. Membrane autopsies and foulant analysis suggested that the dense UF skin layer helped to reject larger-sized organic foulants (> 300 Da), which shed light on the importance of fabrication features and promising application of the double-skinned hollow fiber TFC FO membrane in sludge concentration. On the other hand, a series of characterization revealed that TFC hollow fiber membranes may experience significant compaction during the FO process despite the lack of applied pressure. Three TFC hollow fiber membranes were fabricated with varied water permeability to study the effect of the osmotic pressure on the TFC membranes. The TFC membranes were continuously tested in FO experiments for 24 h using DI water as feed and varied concentration of NaCl solutions as draw solutions, and their performances were evaluated again using fresh feed solutions. At the end of the FO experiments, all TFC membranes experienced water and salt flux decline to different extents. Visible changes in the cross-sectional morphology and surface topography of the TFC membranes were observed. These observations suggested that the occurrence of membrane compaction is strongly associated with the characteristics of the hollow fiber substrates that were used to prepare the TFC membranes and may be attributed to “negative pressure” build-up within the support layer of the TFC membranes.

Mathematical approach for improved performance of flat-sheet forward osmosis membrane

Boron transport through polyamide-based thin film composite forward osmosis membranes

The present work aims to study the possibility of utilization a forward osmosis desalination process as an alternative method to extract water from brine solution rejected from reverse osmosis process. Experiments conducted in a laboratory–scale forward osmosis (FO) unit in cross flow flat sheet membrane cell yielded water flux ranging from (0.0315 to 0.56 L/m2 .min) when using CTA membrane,and ranging from (0.419 to 2.785 L/m2 .min) for PA membrane under 0.4 bar. Two possible membrane orientations were tested. Sodium chloride with high concentrations was used as draw solution solute. The effect of membrane orientation on internal concentration polarization (ICP) was studied. Two regimes of ICP; dilutive and concentrative were described and characterized and their governing equations were applied. Also the effect of draw and feed solution concentrations and flow rate were studied. It was found that the experimental water flux were lower than the theoretical water flux. Using of PA membrane under pressure was resulted in a higher flux of desalinated water than when CTA used alone without pressure under the same operating conditions.

Desalination by ammonia–carbon dioxide forward osmosis: Influence of draw and feed solution concentrations on process performance

Influence of the process parameters on hollow fiber-forward osmosis membrane performances