Search

In order to reduce scaling in a multistage flash (MSF) desalination plant, the brine reject can be diluted using forward osmosis (FO) before recycling. In this FO process, the brine is used as the draw solution (DS) and seawater is used as the feed solution (FS). However, the FO process suffers from low water flux owing to membrane fouling. The water flux in FO can be enhanced by reducing the foulant concentration in the FO feed solution (FS). Thus, in this paper seawater, multimedia sand filtered seawater, and ultrafiltrated seawater is being used as feed solution for the FO process. The flowrate of the feed solution was kept constant at 2.0 L/min. However, the flowrate of the draw solution (DS) were tested at 2.0 and 0.8 L/min. When the flowrate of the DS was 0.8 L/min, the highest initial flux of 44.1 L/m2 h were obtained using ultrafiltrated seawater as FS. After the initial run, the membrane was cleaned and during the second run, 83% of the initial flux was recovered using the ultrafiltrated seawater as FS. For ultrafiltrated seawater, the water recovery rate and specific energy consumption was 36.2% and 0.065 kWh/m3, respectively. [ABSTRACT FROM AUTHOR]

In this study, dewatered construction water was used for the first time as the feed solution in a combined pretreatment-forward osmosis process to dilute seawater (i.e. draw solution) for further desalination. It was found that at a feed solution and a draw solution flow rate of 2.2 L min −1 gave the optimum membrane flux with minimal fouling effects. The addition of a spacer in the membrane feed side was effective at low flow rates (0.8 and 1.5 L min −1 ). The feed solution was then pretreated using two methods: settling and multimedia filtration and used in the forward osmosis unit at a low flow rate of 0.8 L min −1 using a spacer at the feed side. Results revealed a significant increase in the forward osmosis membrane flux by 64.3% when multimedia filtration was carried out with a flux reduction of 7.7%. While the settling method achieved only 13.5% increase in the permeate flux and 12.5% flux reduction. The multimedia filtration process removed most of the particles that would cause fouling which resulted in an elevated and more consistent membrane flux. Results also showed that the water flux was 1.3 times higher when the membrane's active layer was facing the draw solution than when it was facing the feed solution. Cost analysis showed that forward osmosis treatment of dewatered construction water was 7.88 $.day −1 and it was slightly cheaper when the forward osmosis operates in the pressure retarded osmosis mode. [ABSTRACT FROM AUTHOR]

Forward osmosis is considered as the least energy intensive membrane process since it operates based on the osmotic pressure gradient. However, it is still considered as immature technology mainly due to the elevated cost for draw solution regeneration. Nevertheless, magnetic nanoparticles could be considered as a sustainable draw solute for forward osmosis due to high osmotic pressure and easy regeneration using magnetic force, but a significant development is still needed before implementing it for wastewater treatment and desalination. Herein, we analyzed the performance of the available magnetic nanoparticles draw solute and identified the challenges facing the use of magnetic nanoparticles as draw solute in the forward osmosis process. We first highlight the common synthesis methods of magnetic nanoparticles, and basics for generation of osmotic pressure using magnetic nanoparticles. Then, we analyzed the performance and limitations of available magnetic nanoparticles that were used as draw solute in the forward osmosis process. Later, we assessed the toxicity level of the magnetic nanoparticles and explored the regulations of using magnetic nanoparticles in the water treatment industry. Finally, new avenues of research were proposed to make magnetic nanoparticles draw solution more effective when applying it in desalination and wastewater treatment process. [Display omitted] • Magnetic nanoparticle is a promising draw solute for forward osmosis. • The impact of magnetic nanoparticles coating type on water flux was analyzed. • The toxicity of the MNPs and limitations of existing water treatment standards. • State-of-the-art MNPs draw solute were assessed with suggestions for future research. [ABSTRACT FROM AUTHOR]

The effect of the membrane orientation, feeds flow rate, feeds temperature, and combining effect of both temperature and flow rate on the membrane flux was investigated in order to enhance the performance of forward osmosis (FO) process. Results from experimental work demonstrated that the concentrative internal concentration polarization (CICP) could be mitigated by increasing the feed solution flow rate and using a spacer. On contrary, the severity of dilutive internal concentration polarization (DICP) phenomena was aggravated by increasing the draw solution flow rate. It was also found that when increasing the draw solution (DS) temperature from 20 °C to 26 °C the flux increased linearly and then started decreasing when temperature increased over 26 °C due to the development of a temperature gradient. The experimental results also showed that the membrane flux increased by 93.3% due to temperature increase from 20 to 26 °C and the flow rate from 1.2 to 3.2 L/min using a 0.5 M NaCl solution as the draw solution and distilled water as the feed solution (FS). [ABSTRACT FROM AUTHOR]

In this study, bare iron oxide nanoparticles were synthesized using a co-precipitation method and used as a draw solute in forward osmosis. The synthesis conditions of the nanoparticles were optimized using the Box-Behnken method to increase the water flux of the forward osmosis process. The studied parameters were volume of ammonia solution, reaction temperature, and reaction time. The optimum reaction conditions were obtained at reaction temperature of 30 °C, reaction time of 2.73 h and 25.3 mL of ammonia solution. The water flux from the prediction model was found to be 2.06 LMH which is close to the experimental value of 1.98 LMH. The prediction model had high correlation factors (R2 = 98.82%) and (R2adj = 96.69%). This study is expected to be the base for future studies aiming at developing magnetic nanoparticles draw solution using co-precipitation method. [ABSTRACT FROM AUTHOR]

Municipal treated wastewater could be considered as a water source for food crop irrigation purposes. Enhancing the quality of treated wastewater to meet irrigation standards has become a necessary practice. Nanofiltration (NF) was used in the first stage to produce permeate at relatively low energy consumption. In the second stage, two membrane combinations were tested for additional water extraction from the brine generated by the NF process. The simulation results showed that using a hybrid forward osmosis (FO)–reverse osmosis (RO) system is more efficient than using the RO process alone for the further extraction of water from the brine generated by the NF process. The total specific energy consumption can be reduced by 27% after using FO as an intermediate process between NF and RO. In addition, the final permeate water quality produced using the hybrid FO-RO system was within the allowable standards for food crops irrigation. [ABSTRACT FROM AUTHOR]

The forward osmosis (FO) process is an emerging technology that has been considered as an alternative to desalination due to its low energy consumption and less severe reversible fouling. Artificial neural networks (ANNs) and response surface methodology (RSM) have become popular for the modeling and optimization of membrane processes. RSM requires the data on a specific experimental design whereas ANN does not. In this work, a combined ANN-RSM approach is presented to predict and optimize the membrane flux for the FO process. The ANN model, developed based on an experimental study, is used to predict the membrane flux for the experimental design in order to create the RSM model for optimization. A Box–Behnken design (BBD) is used to develop a response surface design where the ANN model evaluates the responses. The input variables were osmotic pressure difference, feed solution (FS) velocity, draw solution (DS) velocity, FS temperature, and DS temperature. The R2 obtained for the developed ANN and RSM model are 0.98036 and 0.9408, respectively. The weights of the ANN model and the response surface plots were used to optimize and study the influence of the operating conditions on the membrane flux. [ABSTRACT FROM AUTHOR]

Artificial neural networks (ANN) are black box models that are becoming more popular than transport-based models due to their high accuracy and less computational time in predictions. The literature shows a lack of ANN models to evaluate the forward osmosis (FO) process performance. Therefore, in this study, a multi-layered neural network model is developed to predict the permeate flux in forward osmosis. The developed model is tested for its generalization capability by including lab-scale experimental data from several published studies. Nine input variables are considered including membrane type, the orientation of membrane, molarity of feed solution and draw solution, type of feed solution and draw solution, crossflow velocity of the feed solution, and the draw solution and temperature of the feed solution and the draw solution. The development of optimum network architecture is supported by studying the impact of the number of neurons and hidden layers on the neural network performance. The optimum trained network shows a high R2 value of 97.3% that is the efficiency of the model to predict the targeted output. Furthermore, the validation and generalized prediction capability of the model is tested against untrained published data. The performance of the ANN model is compared with a transport-based model in the literature. A simple machine learning technique such as a multiple linear regression (MLR) model is also applied in a similar manner to be compared with the ANN model. ANN demonstrates its ability to form a complex relationship between inputs and output better than MLR. • Neural networks to predict the permeate flux for lab-scale forward osmosis process • Low number of hidden layers and high number of neurons result in an accurate model. • A high R2 value of 97.3% shows the training efficiency of the model. • Model validation using published studies with an R2 of 82.1% • Neural network model performs better than multiple linear regression. [ABSTRACT FROM AUTHOR]

Organic fouling in the forward osmosis process is complex and influenced by different parameters in the forward osmosis such as type of feed and draw solution, operating conditions, and type of membrane. In this article, we reviewed organic fouling in the forward osmosis by focusing on wastewater treatment applications. Model organic foulants used in the forward osmosis literature were highlighted, which were followed by the characteristics of organic foulants when real wastewater was used as feed solution. The various physical and chemical cleaning protocols for the organic fouled membrane are also discussed. The study also highlighted the effective pre-treatment strategies that are effective in reducing the impact of organic fouling on the forward osmosis (FO) membrane. The efficiency of cleaning methods for the removal of organic fouling in the FO process was investigated, including recommendations on future cleaning technologies such as Ultraviolet and Ultrasound. Generally, a combination of physical and chemical cleaning is the best for restoring the water flux in the FO process. [ABSTRACT FROM AUTHOR]

In this study, treated wastewater and Multi-Stage Flash (MSF) brine were integrated into the Forward Osmosis (FO) system using pressure stimuli-responsive Nanofiltration (PSRNF) membranes to dilute magnesium, calcium, and sulfate MSF plant brine reject. The deposition of magnesium sulfate and calcium sulfate in the heat exchanger is one of the main issues affecting the performance and efficiency of MSF thermal desalination plants. Reducing the concentration of the divalent ions can minimize scale formation and deposition to a level that allows the MSF plant to operate at high top brine temperature (TBT) and without scale problems. The PSRNF membranes were chosen in the FO process because of their high water permeability, rejection of divalent and monovalent ions, small structure parameter (S), and inexpensiveness compared to commercial FO membranes. Three PSRNF membranes were tested in the FO process with the feed solution facing the active membrane layer to avoid active layer delamination. Although the PSRNF membrane exhibited negligible water flux at 0 bar, it increased when a 2–4 bar was applied to the feed solution. The wastewater temperature was set at 25 °C while 40 °C was the brine operational temperature to mimic the field situation. A maximum average water flux of 39.5 L/m2h was recorded at 4 bar feed pressure when the PSRNF membrane was used for the brine dilution, achieving up to 42% divalent ions dilution at 0.02 kWh/m3 specific power consumption. The average water flux in the PRSNF membrane was 35% higher than that in the commercial TFC FO membrane. Notably, the PSRNF membrane is ten times cheaper than commercial FO membranes. Notably, the PSRNF membrane is ten times cheaper than commercial FO membranes, achieving substantial cost reductions and pioneering advancements in FO purification technology. • PSRNF was applied to dilute the MSF's brine reject using a wastewater feed solution. • PSRNF water flux increased exponentially when feed pressure increased from 0 to 4 bar. • The PSRNF membrane achieved 30% higher water flux than the commercial TFC FO membrane. • The energy required to dilute wastewater by the PSRNF membrane at 4 bar was 0.02 kWh/m3. • The PSRNF membrane cost is 10 times cheaper than the commercial TFC and CTA FO membranes. [ABSTRACT FROM AUTHOR]

Forward osmosis is the least energy intensive water treatment membrane process, however, designing a sustainable draw solute is still a critical research necessity. In this work, we developed Poly(amidoamine) dendrimer coated magnetic nanoparticles (PAMAM-MNPs) to be used as a draw solute in the forward osmosis process. Poly(amidoamine) dendrimer was selected due to its highly branched tree-like structure, diverse types of terminal groups, and ability to induce high osmotic pressure. The synthesized MNPs had a crystalline structure of a single-phase magnetite, spherical shape with an average size of 11.8 nm for bare MNPs, and 17.1 nm for PAMAM-MNPs. The performance of the synthesized MNPs as draw solute was tested using a bench scale forward osmosis setup. The average water flux obtained was 12.9 LMH during the first running cycle and decreased with time due to the dilution of draw solution. The MNPs were easily recovered using a permanent magnet and reused as draw solute for multiple cycles. The average water decreased by almost 25 % after four running cycles due to membrane fouling. This study highlighted the performance and limitations of using a newly developed dendrimer coated MNPs draw solute in the forward osmosis process. [Display omitted] • Poly(amidoamine) dendrimer coated magnetic nanoparticles was used as draw solute. • Poly(amidoamine) dendrimer has a highly branched tree-like structure. • The average water flux obtained was 12.9 LMH during the first cycle. • A full recovery of the magnetic nanoparticles was achieved using permanent magnet. • Membrane fouling when using magnetic nanoparticles as draw solute was evaluated. [ABSTRACT FROM AUTHOR]

[Display omitted] • FO is an economical pretreatment process for MSF compared to NF. • Technical and economical evaluation was done at a pilot scale for the FO process. • The maximum recovery rate of the FO process was 27% • The rejection rate for scaling ions exceeded 92% • The water production cost of the FO process was 0.48 $/m3. Thermal desalination processes suffer from the formation of scalants on the heat exchangers of the evaporator unit which negatively affect the process efficiency. This study evaluated the technical and economic feasibility of a pilot-scale forward osmosis (FO) process for the pretreatment of seawater to remove scaling ions before the multi-stage flash (MSF) process. A commercial hollow fiber FO membrane module was used in the pilot plant. The FO pilot plant used real seawater as feed solution and real MSF brine as draw solution. A maximum recovery rate of 27.7 % was achieved using a pressure gradient of 1.0 bar with the feed solution flowing through the membrane bore side and the draw solution flowing through the shell side with a temperature of 40 °C for both feed and draw streams. The FO membrane showed high rejection for scaling ions, where the rejection rate was almost 99 %, 96 %, and 92 % for sulfate, calcium, and magnesium, respectively. The specific power consumption of the FO process was about 0.01 kWh/m3. It was found that the water production cost for the FO process was almost 0.48 $/m3. The sensitivity analysis shows that the water production cost is highly sensitive to the water flux, especially at the lower range of water flux and high membrane cost. FO pretreatment provides a promising and economical solution for mitigating the scaling issue in MSF desalination plants. [ABSTRACT FROM AUTHOR]