Assisted reverse electrodialysis : a novel technique to decrease reverse osmosis energy demand

Assisted reverse electrodialysis (ARED) was introduced as a pre-desalination technique for seawater reverse osmosis (RO) for drinking water production. ARED is comparable to an additional applied pressure along the osmotic pressure in pressure assisted osmosis; a small voltage is applied in the same direction as the open cell voltage to increase the desalination speed compared to reverse electrodialysis (RED). This decreases the required membrane area. The concentration of the dilute compartment increases significantly during ARED operation due to the increased speed of desalination. This results in an overall decrease in total cell resistance. Although the energy demand for ARED is higher than for RED, the ARED-RO process still achieves a decrease in overall energy requirements at higher RO recoveries when compared to stand-alone RO. However, ion-exchange membrane prices will have to come down to 1-10 €/m² for the ARED-RO hybrid to become economically viable at current energy prices

Influence of osmotic energy recovery/osmotic dilution on seawater desalination energy demand

Supplying fresh, potable water to an ever increasing world population is becoming a major challenge. One possibility is to produce fresh water from seawater by Reverse Osmosis (RO), a process that is very energy intensive. To reduce the energy demand of this process, osmotic dilution (OD)/osmotic energy recovery (OER) systems can be used as pre-treatment. Both Reverse Electrodialysis (RED) and Pressure Retarded Osmosis (PRO) and their non energy-producing counterparts short-circuited RED/ Forward Osmosis (scRED/FO) and assisted RED/FO (ARED/AFO) were modelled as OD/OER devices for RO, in a thermodynamic way. Different mixing ratios of impaired versus salt water (0.5, 1 and 2) were compared at a realistic RO recovery of 50%. A realistic approach for the RED/PRO-RO hybrid process was also modelled incorporating some major losses, to gain a more realistic insight into its possibilities. The thermodynamic modelling revealed that a significant reduction of the SEC is possible with all hybrid processes. The reduction in SEC is less for the non energy-producing systems, but these have the added advantage of requiring a lower membrane area to achieve a similar extent of seawater dilution. From preliminary results of the more realistic modelling, it seems that RED-RO scores better when losses are incorporated. Further thermodynamic and realistic modelling will focus on different RO recoveries, capital cost calculations based on membrane requirements and sensitivity analysis of the different parameters implemented

The Combination of Coagulant Aid, Ion Exchanger, and Reverse Osmosis (RO ) on Brackish Water Treatment

The high content of chloride salts, and other dissolved salts such as; SO42-, Na+, and the presence of coliform criteria lead to non-compliance of brackish water as clean water. Decreasing of the content of water’s parameters in brackish water can be done by treatment of Coagulant Aid and Ion Exchanger that followed serially by membrane technology reverse osmosis (RO). The flowing process of treatment in this study are : coagulant aid, filtration using sediment polipropylena (SPP), and absorption using manganese greensand, then continued by Ion Exchanger using synthetic resin anion and cation resin. As a finishing treatment is filtration micro using membrane of Reverse Osmosis (RO). The combination of coagulant aid, ion exchangers and reverse osmosis (RO) water treatment brackish obtained on removal parameters: Chloride of 2028 ppm, Turbidity 2.74 NTU scale, color 45 units PtCo, Iron 0.22 ppm, Total Disolved Solid (TDS) 3366 ppm, Total Hardness 621.43 mg/L,  CaCO3, Organic Substances 19.84 mg/L KMnO4, Fluoride 0.62 ppm, Nitrate 0.06 ppm,  Nitrite 0.64, Zinc 0.08 ppm, Sulfate 40.46 ppm, and Detergent at 0.12 mg/L LAS. Processing brackish water based on RO membrane techno combined with coagulant aid  and ion exchanger are able to fulfill all of clean water requirements parameters Keywords: brackish water, coagulant aid, ion exchanger, reverse osmosis (RO

Treatment of Wastewater Using Reverse Osmosis for Irrigation Purposes

This work investigates the performance of reverse osmosis (RO) for the reclamation of treated sewage effluent (TSE) to be used as irrigation water for food crops. The feed water used in this study was a real sample of ultra-filtered tertiary treated sewage effluent (TSE). Reverse osmosis (RO) was evaluated using the following experimental conditions applied pressure (10 - 20) bar, flow rate 3.5 LPM and (BW30LE) membrane. The performance of RO was evaluated according to the water flux and rejection of dissolved solids. The final water quality was compared with irrigation water standards. The results reported in this study show that reverse osmosis (RO) is capable of reclaiming treated sewage effluent (TSE) to be used as irrigation water for food crops. The maximum average flux was 77.7 LMH achieved using a feed pressure of 16 bar. The permeate water generated using RO had high quality which met the irrigation standards for food crops.This research is made possible by graduate sponsorship research award (GSRA6-1- 0509-19021) from Qatar National Research Fund (QNRF). The statements made herein are solely the responsibility of the authors

Exploring the differences between forward osmosis and reverse osmosis fouling

A comparison of alginate fouling in forward osmosis (FO) with that in reverse osmosis (RO) was made. A key experimental finding, corroborated by membrane autopsies, was that FO is essentially more prone to fouling than RO, which is opposite to a common claim in the literature where deductions on fouling are often based solely on the water flux profiles. Our theoretical analysis shows that, due to a decrease in the intensity of internal concentration polarization (ICP), and thus an increase in the effective osmotic driving force during FO fouling tests, the similarity of experimental water flux profiles for FO and RO is in accordance with there being greater fouling in FO than RO. The specific foulant resistance for FO was also found to be greater than that for RO. Possible explanations are discussed and these include the influence of reverse solute diffusion from draw solution. Whilst this explanation regarding specific foulant resistance is dependent on the draw solution properties, the finding of greater overall foulant accumulation in FO is considered to be a general finding. Additionally, the present study did not find evidence that hydraulic pressure in RO plays a critical role in foulant layer compaction. Overall this study demonstrated that although FO has higher fouling propensity, it offers superior water flux stability against fouling. For certain practical applications this resilience may be important

Process optimization for an integrated reverse osmosis—pressure retarded osmosis pilot-scale system operated on Humboldt Bay, CA

Pressure retarded osmosis (PRO) is an emerging osmotic power technology that could mitigate the major challenges faced by seawater reverse osmosis desalination (RO): brine disposal and high energy consumption. The primary focus of this paper is process optimization for a linked seawater reverse osmosis (RO) and pressure retarded osmosis (PRO) water purification system. PRO generates power by using osmosis to “pump” water through a membrane from low pressure and low concentration to high pressure and high concentration (RO brine). This commercial-scale pilot effort explores process optimization for pressure retarded osmosis as an industrial process rather than theoretical or experimental process. To achieve this purpose, a linked seawater desalination and pressure-retarded osmosis system was built on Humboldt Bay, CA, with assistance from Cal Poly Humboldt, CA DWR, and the Humboldt Bay Harbor Commission. This study explored the lowest net specific energy consumption (SECnet) for producing freshwater from seawater in the first U.S. RO-PRO pilot-scale facility employing commercially-available components. The lowest SECnet was found by adjusting and testing six operating variables: RO yield rate, PRO operating pressure, PRO dilution rate, PRO feed solution flow rate, and PRO draw solution flow rate. Each variable was tested independently to narrow the range of optimal values. Findings conclude that energy losses in the RO-PRO system approximately equal the amount of potential energy that can be gained using PRO membranes available in 2017. Increasing membrane performance and optimizing module membrane spacers for PRO could significantly increase potential energy recovered by PRO in an RO-PRO system

ANALISA PERILAKU DAYA BELI MASYARAKAT SURABAYA TERHADAP PRODUK AIR REVERSE OSMOSIS (RO) DENGAN MENGGUNAKAN METODE WILLINGNESS TO PAY (WTP) (Studi Kasus Masyarakat Surabaya)

Dunia semakin menyadari bahwa krisis lingkungan yang terjadi dewasa ini membutuhkan perhatian ekstra, tak mudah mendapatkan air tanah yang memenuhi syarat kesehatan. Salah satu solusi yang paling masuk akal mengatasi problem air bersih adalah dengan memanfaatkan teknologi ultraviolet (UV) dan Reverse Osmosis (R.O) yang biasa disebut air R.O. Untuk daerah Surabaya, informasi yang terkait dengan masalah keamanan penggunaan air R.O belum tersampaikan secara benar ke Masyarakat. Sehubungan dengan permasalahan diatas, maka permasalahan yang muncul berapakah nilai WTP masyarakat terhadap air Reverse Osmosis (RO), dan berapakah nilai WTP masyarakat apabila ada skenario jumlah air Reverse Osmosis (RO) banyak dan mudah dijangkau oleh warga, serta faktor – faktor apakah yang berpengaruh dan besar pengaruh tersebut nilai WTP masyarakat. Nilai WTP Masyarakat terhadap air R.O (Reverse Osmosis) adalah pada rentang nilai antara Rp 5.772,73 hingga Rp 8.733,33. Nilai WTP tidak terlalu banyak berubah dengan adanya skenario jumlah air R.O (Reverse Osmosis) banyak dan mudah dijangkau meskipun probabilitas WTP mengalami sedikit peningkatan, dimana nilai WTP skenario tidak berbeda jauh dengan nilai WTP initial. Pergeseran ini disebabkan dengan skenario tersebut maka daya beli masyarakat di daerah Surabaya barat semakin tinggi, hal ini sesuai dengan pengaruh positif pendapatan yang tinggi terhadap nilai WTP. Faktor yang berpengaruh positif terhadap WTP adalah usia, jenis pekerjaan, pendapatan, ratarata pembelian dan kandungan air minum. Sedangkan yang berpengaruh negatif adalah jenis kelamin dan pendidikan. Berdasarkan faktor – faktor yang ada maka di butuhkan pengembangan informasi air R.O (Reverse Osmosis) dan meningkatkan manajemen pemasarannya, khususnya daerah Surabaya Barat

Osmotic versus conventional membrane bioreactors integrated with reverse osmosis for water reuse: Biological stability, membrane fouling, and contaminant removal

© 2016 This study systematically compares the performance of osmotic membrane bioreactor – reverse osmosis (OMBR-RO) and conventional membrane bioreactor – reverse osmosis (MBR-RO) for advanced wastewater treatment and water reuse. Both systems achieved effective removal of bulk organic matter and nutrients, and almost complete removal of all 31 trace organic contaminants investigated. They both could produce high quality water suitable for recycling applications. During OMBR-RO operation, salinity build-up in the bioreactor reduced the water flux and negatively impacted the system biological treatment by altering biomass characteristics and microbial community structure. In addition, the elevated salinity also increased soluble microbial products and extracellular polymeric substances in the mixed liquor, which induced fouling of the forward osmosis (FO) membrane. Nevertheless, microbial analysis indicated that salinity stress resulted in the development of halotolerant bacteria, consequently sustaining biodegradation in the OMBR system. By contrast, biological performance was relatively stable throughout conventional MBR-RO operation. Compared to conventional MBR-RO, the FO process effectively prevented foulants from permeating into the draw solution, thereby significantly reducing fouling of the downstream RO membrane in OMBR-RO operation. Accumulation of organic matter, including humic- and protein-like substances, as well as inorganic salts in the MBR effluent resulted in severe RO membrane fouling in conventional MBR-RO operation

Unlocking High-Salinity Desalination with Cascading Osmotically Mediated Reverse Osmosis: Energy and Operating Pressure Analysis

Current practice of using thermally driven methods to treat hypersaline brines is highly energy-intensive and costly. While conventional reverse osmosis (RO) is the most efficient desalination technique, it is confined to purifying seawater and lower salinity sources. Hydraulic pressure restrictions and elevated energy demand render RO unsuitable for high-salinity streams. Here, we propose an innovative cascading osmotically mediated reverse osmosis (COMRO) technology to overcome the limitations of conventional RO. The innovation utilizes the novel design of bilateral countercurrent reverse osmosis stages to depress the hydraulic pressure needed by lessening the osmotic pressure difference across the membrane, and simultaneously achieve energy savings. Instead of the 137 bar required by conventional RO to desalinate 70 000 ppm TDS hypersaline feed, the highest operating pressure in COMRO is only 68.3 bar (−50%). Furthermore, up to ≈17% energy saving is attained by COMRO (3.16 kWh/m3, compared to 3.79 kWh/m3 with conventional RO). When COMRO is employed to boost the recovery of seawater desalination to 70% from the typical 35–50%, energy savings of up to ≈33% is achieved (2.11 kWh/m3, compared to 3.16 kWh/m3 with conventional RO). Again, COMRO can operate at a moderate hydraulic pressure of 80 bar (25% lower than 113 bar of conventional RO). This study highlights the encouraging potential of energy-efficient COMRO to access unprecedented high recovery rates and treat hypersaline brines at moderate hydraulic pressures, thus extending the capabilities of membrane-based technologies for high-salinity desalination

Comparison of fouling propensity between reverse osmosis, forward osmosis, and membrane distillation

Resistance to fouling is often cited as an advantage of emerging desalination technologies such as forward osmosis and membrane distillation over the widely-used reverse osmosis process. However, the nature and magnitude of differences in fouling behavior between these three processes are not well characterized. This study directly compares the fouling and scaling behavior of reverse osmosis (RO), forward osmosis (FO), and direct contact membrane distillation (MD) in the same membrane module under identical hydrodynamic conditions (flux and cross-flow velocity). Fouling experiments were conducted using calcium sulfate as a model inorganic foulant and alginate as a model organic foulant. Although all three processes tolerated some degree of feed supersaturation for 36 h without inorganic fouling (scaling), FO exhibited the greatest scaling resistance, withstanding a feed of 33 ± 2 mM CaSO₄ (approximately twice saturation) without significant flux decline. Scaling occurred at similar concentrations at the membrane between MD and RO; however, while MD tolerated a more concentrated bulk feed due to reduced concentration polarization, flux decline after fouling was considerably more severe in MD. In contrast, MD tolerated organic fouling much better than FO or RO: despite accumulating a similar quantity of alginate gel over 18 h of operation, flux declined only 14% in MD versus 46–47% in RO and FO. These results are explained with respect to differences in temperature, membrane materials, and transport mechanisms between the three processes. Although FO and MD each exhibited superior resistance to one type of foulant, neither process outperformed RO in resistance to both organic and inorganic fouling. These findings inform a more nuanced approach to process selection for the treatment of complex water sources. Keywords: Desalination; Forward osmosis; Fouling resistance; Membrane distillation; Reverse osmosi