Conventional Reverse Osmosis Process Research Articles

Cost-based optimization, feasibility study, and sensitivity analysis of forward osmosis/crystallization/reverse osmosis with high-temperature operation for high-salinity seawater desalination

Seawater desalination plants using reverse osmosis (RO) in high temperature and high-salinity conditions, such as in the Middle East, face challenges such as limited achievable recoveries and high energy costs. This study evaluated the economic feasibility under seawater and high-salinity conditions by introducing a forward osmosis/crystallization/reverse osmosis (FO/Cry/RO) hybrid process. The optimization results were then used to compare the specific water cost (SWC), specific energy consumption (SEC), recovery, and permeate quality of the hybrid process with two different draw solutes and a conventional seawater RO process. In addition, a sensitivity analysis was conducted to determine how individual process parameters and operating conditions affect the economic feasibility of the proposed process under seawater and high-salinity conditions. The FO/Cry/RO hybrid process achieved a higher recovery with a lower SWC and SEC as the feed concentration increased compared to the conventional RO process. Utilizing waste heat further increased the economic advantages of the proposed process. In addition, much higher permeate quality can be obtained depending on the type of draw solute. The results of this study revealed that the proposed hybrid system outperformed the conventional RO process in terms of both energy efficiency and cost-effectiveness for seawater desalination under high-temperature and high-salinity conditions.

Optimization of Integrated Forward – Reverse Osmosis Desalination Processes for Brackish Water

Reverse Osmosis (RO) is a membrane desalination process which considered to be an efficient technology for desalination. However, the performance of RO process is facing some challenges; the most important of them are the energy consumption and fouling problem due to external concentration polarization (ECP). Forward osmosis (FO) is an osmotic-driven membrane desalination process, it exhibits lower energy consumption than pressure driven process like RO. It has been suggested to be coupled with RO in order to reduce salinity and the energy consumption. For this objective, a mathematical model has been designed to optimize the operational conditions for FO, RO and FO-RO hybrid system. Firstly, an individual FO experiment has been conducted using urea and sodium chloride as draw solutions to evaluate the FO performance in both agriculture waste treatment and desalination. Then, a modeling approach of an individual FO process has been investigated with considering water flux, solute flux and concentration polarization. In addition, the performance of FO-RO integrated system was compared with conventional RO process in terms of energy consumption, permeate quantity, quality and solute flux. The results of modeling calculations showed that the feed solution concentration, draw solution concentration and concentration polarization are very important factors that affect the overall performance. In addition, it indicated a good performance of individual FO process. Moreover, it revealed increase in both water productivity and permeate quality and a significant decline in energy consumption upon using the efficient FO-RO hybrid system to about 0.9 kWh/m3. Consequently, it offered high energy saving ranged between 87.57% and 87.81%, which confirmed that FO/RO integrated system is more energy efficient than the RO process only.

Preparation and Characterization of Pore Filled Hybrid Composite Membrane Composed of Cation Exchange Materials and Polyethylene Support.

This study investigated ion exchange membranes for application to seawater desalination processes. This can provide better energy efficiency than the conventional reverse osmosis process. In this experiment, the problem of decreasing ion exchange performance when the ion exchange composite membrane was prepared could be improved through nanoparticles. The nanoparticle added ion exchange hybrid membrane showed ion exchange capacity similar to that of the conventional pristine film. In addition, the polymer having a high ion exchange capacity has poor mechanical strength, but has excellent mechanical strength of 30 MPa or more by the introduction of a polyethylene support.

Cost-based feasibility study and sensitivity analysis of a new draw solution assisted reverse osmosis (DSARO) process for seawater desalination

In this study, a newly devised seawater desalination process, namely, the draw solution assisted reverse osmosis (DSARO) process, is proposed. A mathematical model for the DSARO process was developed and energy consumption and economic evaluation models were constructed to assess the feasibility of the DSARO process compared to the conventional reverse osmosis (RO) process. This work presents a characterization of important variables and the research on the effects of these variables. Compared to the conventional RO process, the DSARO process could have a 10% lower specific water production cost. The operating pressures required to reach 40% of overall recovery were approximately 35bar in the 1st RO process, and 30bar in the 2nd RO process. Due to its operating pressure being lower than the conventional RO process, the capital and membrane replacement costs could be reduced. The required conditions in the 1st RO membrane to drive the DSARO process were that the membrane structure parameter must be lower than 0.13mm, and the maximum operating pressure should be higher than 35bar. Even though these conditions are not available commercially at present, they could be attained based on the best available membrane technology in the literature.

Forward osmosis desalination from laboratory to market

A two-step forward osmosis (FO) desalination process combining both FO and reverse osmosis (RO) systems has been developed by the Centre for Osmosis Research and Applications at the University of Surrey and commercialised by Modern Water plc. In the FO + RO process seawater was used as feed water (FW) and a concentrated aqueous solution was used as a draw solution (DS). By taking advantage of natural osmosis, pure water is transferred from the FW to the DS and then recovered from the DS by the RO process utilising low resistance membranes, and hence lower specific energy consumption (SEC). This paper presents results of FO experiments conducted on flat sheet membrane using a bench-scale rig. The osmotic agent investigated in this study was magnesium sulphate, which is non-toxic, and highly soluble in water. Furthermore experiments were carried out on the RO pilot in order to regenerate the DS for reuse in the FO process and produce clean water. This paper also presents some pilot plant results and data from commercial plants in Oman and Gibraltar. The data demonstrates the efficiency of the FO + RO compared with the conventional RO process in terms of SEC and membrane fouling performance.

Two-stage FO-BWRO/NF treatment of saline waters

AbstractTwo-stage forward osmosis (FO)–reverse osmosis (RO)/BWRO and conventional RO/BWRO processes were evaluated for saline water treatment. Three different salts, NaCl, MgCl2 and MgSO4, were used as a draw solution. The performance of FO, RO and BWRO regeneration processes was simulated using predeveloped software. The simulation results showed that the water and solute flux across the FO membrane decreased with increasing the FO recovery rate. The highest water flux was in case of 1.2 mol NaCl draw solution for seawater desalination. The total power consumption for seawater desalination was lower in the RO process than in the FO–RO process. However, as the RO recovery rate increased, the difference in total power consumption between the conventional RO process and 0.65 mol MgCl2 FO–RO processes was insignificant. In case of brackish water desalination, the lowest specific power consumption and permeate TDS were in case of the conventional BWRO process and then followed by 0.32 mol MgSO4, 0.22 mol MgCl...

Industrial and brackish water treatment with closed circuit reverse osmosis

Abstract Closed Circuit Desalination (CCD™) technology is an emerging platform for reverse osmosis (RO) water treatment and desalination. It lowers the feed pressure requirement, improves the membrane performance, increases the operational flexibility, and eliminates the need for energy recovery devices using only standard RO equipment. For industrial water treatment and brackish water desalination applications, CCD technology achieves maximum recovery in single-stage units while saving energy. Alternately, a CCD unit can be added to a conventional RO process to concentrate brine and raise recovery. Over 97% recovery has been demonstrated in a single-stage operation. The recovery rate of a CCD unit can be adjusted at the control panel without modification of system hardware, limited only by the scaling characteristics of the feedwater. Maximum recovery operation and high flexibility have significant cost-cutting implications for industrial water treatment and inland brackish desalination, where both feedwater supply costs and brine disposal fees can be significant. CCD systems also demonstrate excellent resistance to fouling and scaling. Cross-flow supplied by a circulation pump washes the membranes, and salinity cycling disrupts and greatly reduces the scaling and fouling. Short membrane arrays and high cross-flow allow the CCD process to operate at higher average fluxes than conventional RO processes, without exceeding the membrane manufacturer’s flow or recovery specifications. This paper describes the design and modeling of high-recovery CCD processes and compares the measured and calculated specific energy consumption levels to validate modeling methods and tools. Two brackish water RO cases are considered: one using Desalitech’s seawater reverse osmosis–CCD (SWRO-CCD) process and the other using its hybrid plug flow desalination–SWRO–CCD (PFD-SWRO-CCD) process. CCD systems are compared favorably to conventional RO trains modeled with the same feedwater, high-pressure pumps, and membranes operating at the same average flux and overall recovery percentage.

Microporous Silica Based Membranes for Desalination

This review provides a global overview of microporous silica based membranes for desalination via pervaporation with a focus on membrane synthesis and processing, transport mechanisms and current state of the art membrane performance. Most importantly, the recent development and novel concepts for improving the hydro-stability and separating performance of silica membranes for desalination are critically examined. Research into silica based membranes for desalination has focussed on three primary methods for improving the hydro-stability. These include incorporating carbon templates into the microporous silica both as surfactants and hybrid organic-inorganic structures and incorporation of metal oxide nanoparticles into the silica matrix. The literature examined identified that only metal oxide silica membranes have demonstrated high salt rejections under a variety of feed concentrations, reasonable fluxes and unaltered performance over long-term operation. As this is an embryonic field of research several target areas for researchers were discussed including further improvement of the membrane materials, but also regarding the necessity of integrating waste or solar heat sources into the final process design to ensure cost competitiveness with conventional reverse osmosis processes.