Reverse Osmosis Concentration Research Articles

Evaluating the advantage of turbulent flow to diminish concentration polarization in Roto-dynamic RO system

Concentration polarization (CP) is the major shortcoming of the reverse osmosis (RO) system for brackish/seawater desalination. The present study aims to understand the effect of induced shear stress, enhanced flow dynamics, and eddy diffusivity on CP, when the flow is turbulent. In roto-dynamic RO system turbulence can be easily generated by controlling the angular speed of the rotor without increasing the feed discharge. We have numerically simulated the salt rejection by the RO membrane and concentration polarization at the seawater salinity of 500 mol/m3 for two different configurations of roto-dynamic RO system when the flow is turbulent. We have used Reynolds stress model (RSM) and eddy viscosity-dependent eddy diffusivity models for salt transport. In turbulent flow regime, eddy diffusion enhances the mixing. In laminar flow regime, salt concentration over the membrane increases by 60%–110% for 70 bar feed pressure. In contrast, the increment of salt concentration is only about 3%–4% once the flow becomes turbulent, leading to 3–4 times higher permeate discharge for roto-dynamic RO system. Thus, it can increase the longevity of the membrane and improve overall performance of the RO module by delaying membrane scaling and fouling.

Separation methods in the food industry: An exploration of reverse osmosis, evaporation and freeze concentration applications

Separation method is broadly used in various industries, mainly in the food industry. Some of the applications include retaining the nutrients and concentrating fruit juices, liquid foods, and milk products. Fundamentally, the concentrated liquid product is achieved by these separation methods. Technology advances daily, impacting food quality characteristics such as flavour, colour, and texture. Production and commercialisation processes are key considerations, from conventional to modern approaches. Hence, this study aims to review the various types of separation methods with their application in food industries which are evaporation, reverse osmosis, and freeze concentration that is separated into two: suspension freeze concentration and progressive freeze concentration

Bipolar membrane electrodialysis for sustainable utilization of inorganic salts from the reverse osmosis concentration of real landfill leachate

Developing an effective resource utilization method for landfill leachate reverse osmosis concentrate (LLRC) remains a challenge because of the high concentrations of inorganic salts and refractory organic compounds. This study applied a bipolar membrane electrodialysis (BMED) to separate inorganic salts from real LLRC while simultaneously reclaiming inorganic acids and bases. The performance of BMED was affected by operating parameters, such as operating voltage, membrane surface flow velocity, and initial acid-base concentration. With optimized operating parameters, the reclaimed acid-base concentrations, desalination rate, and current efficiency were higher with less energy consumption. Ultimately, 0.41 mol/L acids and 0.40 mol/L bases were reclaimed from LLRC. The reclaimed acids contained 88 wt% HCl and 12 wt% HNO3. The reclaimed bases were 52 wt% NaOH and 45 wt% KOH. Furthermore, the concentrations of arsenic and heavy metals were low enough to safely utilize reclaimed products. The electromigration of organic compounds was controlled by protonation. After excluding the fixed costs, the net profit of 1 m3 LLRC treatment by BMED was $27.630, which showed remarkable economic feasibility. Our research offers a new strategy to realize sustainable utilization of inorganic salts from LLRC.

Investigation of foaming behavior in herbal extracts via the characterization of solution environment for reverse osmosis concentration

Foaming can be a challenge in many herbal extract processing, particularly with membrane technology involved. The foaming behavior of saponins and herbal solution containing saponins in the static system were investigated to gain more fundamental understanding on the correlations of foaming behavior- solution environment properties. To identify the cause and effects of foaming behavior under various conditions, foaming ability, foam sizes, as well as the physical properties (i.e. surface tension, zeta potential, viscosity, conductivity and pH) of the saponin solutions were characterized. The surface tension of mimic solution with the presence of saponins, polysaccharides and proteins was measured at 43.21 N/m, similar to the result of Sijunzi Decoction herbal extracts at 40.99 N/m, while other properties differed substantially. Foaming was confirmed to cause pressure drop in the dynamic concentration by reverse osmosis, while the foam height might pose insignificant impact on the magnitude of pressure drop. Significant feed pressure drop from 1.2 MPa to 1.0 MPa was observed in dynamic reverse osmosis concentration test of herbal extracts operated, while the pressure drop was negligible when operated at lower pressure operation (<0.6 MPa) with the same feed flow rate.

A Novel Mass Transfer Model to Describe the Separation Process in Reverse Osmosis of Glucose

Basic and theoretical research on processes such as reverse osmosis (RO) is essential in the fermentation industry to improve production efficiency and reduce cost. Here, we focus on the RO concentration of glucose solutions. We constructed a mathematic model that incorporates various membrane and experimental parameters to characterize the mass transfer process of RO membrane and validated the model output with experimental data. Calculation results were highly consistent with the experimental data, demonstrating that this model can be useful for predicting the RO concentration process.

Precipitation to remove calcium ions from stabilized human urine as a pre-treatment for reverse osmosis.

Concentration of Ca(OH)2 stabilized urine by reverse osmosis (RO) has the potential to cause CaCO3 scaling on the membranes. The aim of this research was to determine whether the addition of carbonate salts could be used to precipitate CaCO3 prior to RO concentration and how to accurately dose the salts. Dosing of NaHCO3 or Na2CO3 reduced the calcium concentration to <0.18 mmol L-1, whilst maintaining a pH > 11. This is the pH threshold for enzymatic urea hydrolysis in urine, but above the operating pH range of most membranes. However, the pH could be decreased by adding an acid. Measuring conductivity as a proxy for the calcium concentration was found to be an effective method to determine the dose of salt required. Simulations with other carbonate-producing salts (KHCO3, MgCO3, and NH4HCO3) were also shown to be effective. However, NH4HCO3 ($0.53 m-3 urine) was the only other salt comparable in cost to NaHCO3 ($0.49 m-3 urine) and resulted in a final pH within the normal operating range of membranes. The addition of NH4HCO3 would add extra N to the urine rather than sodium ions when dosing NaHCO3. The choice of salt will ultimately depend on what liquid fertilizer composition is desired.

Blueberry juice: Bioactive compounds, health impact, and concentration technologies-A review.

Blueberries are a popular fruit with an attractive flavor and color, as well as health benefits. These health benefits have been attributed to the important number of bioactive compounds in blueberries with activities such as antioxidant, antitumor, antimutagenic, and antidiabetic effects and the prevention of cardiovascular diseases. Despite these advantages, blueberries are only obtained fresh in certain seasons; therefore, the food and beverage industry transforms them into jelly, puree, or juice. However, the concentration process could help preserve the bioactive compounds of blueberry byproducts. Concentration technologies focus on the removal of excess water to increase the product stability and reduce storage and transportation costs by causing them to take up less space or as a pretreatment before dehydration. These technologies include evaporation, reverse osmosis, and freeze concentration, and each one has different effects on the efficiency, quality, and nutritional value of the final concentrates. However, freeze concentration and reverse osmosis produce a higher-final quality concentrate than evaporation due to the use of low temperatures, which prevents the loss of thermolabile components such as bioactive compounds. Therefore, this review summarizes the impact of concentration technologies on the bioactive compounds and health benefits of blueberry juice.

Performance evaluation of microbial fuel cell with sewage wastewater and RO concentrate using composite anode made of Luffa aegyptiaca

AbstractMicrobial Fuel Cells (MFCs) are capable of producing bioelectricity using bacteria as catalysts that break down the organic matter present in wastewater (WW). The present work demonstrates the synergistic effect of Luffa aegyptiaca (LA) combined with graphite plate as anode material on voltage generation as well as pollution removal as chemical oxygen demand (COD). Three different feed combinations of WW and Reverse Osmosis (RO) concentrate that is ‐ Experiment‐1 (75:25), Experiment‐2 (50:50), and Experiment‐3 (25:75) have been considered and their performances are compared with the system without LA in the anode. The result shows that low organic loading rate (OLR) and more RO concentration in feed inlet led to more voltage and normalized energy recovery (NER) that is – 530 mV and 19.51 Whkg−1 COD−1, respectively.

Treatment of electroplating wastewater using the freezing method

Wastewater produced from washing can be concentrated and reused in an electroplating bath to produce a cleaner product. Predominant methods of concentrating wastewater from electroplating washing include reverse osmosis and evaporation concentration. However, reverse osmosis cannot treat strongly acidic (pH < 2) or strongly alkaline (pH > 12) wastewaters, and the scope of its application is narrow, while evaporation uses high quantities of energy and is costly. In contrast, freezing electroplating washing wastewater incurs low cost and can be used for treating washing wastewater from various electroplating processes. In this study, supercooled water dynamic ice making (SWDIM) technology was applied for the first time to freeze and crystalize electroplating washing wastewater, followed by centrifugal separation to separate solid and liquid phases. Freezing treatment was performed on the washing water from the acid copper process (pH = 1.15), nickel plating process (pH = 5.1), and zincate zinc plating process (pH = 13.2). The results show that after primary freezing and centrifugal dehydration, the solute removal rate of ice melt water exceeded 90%, which can meet the requirements of the primary washing tank to supplement the washing water. After secondary freezing and centrifugal dehydration, the concentrated wastewater (approximately 0.14 vol of the original wastewater) can be produced, further evaporated and concentrated 2.8 times, and reused for the electroplating bath.

Impact of sterilization and storage on the properties of concentrated skim milk by cryoconcentration in comparison with vacuum evaporation and reverse osmosis concentration

AbstractThe aim of this study was to compare the impact of sterilized skim milk after being concentrated by three concentration techniques; namely cryoconcentration, vacuum evaporation, and reverse osmosis. To achieve this objective, skim milk was concentrated up to 18% total dry matter by cryoconcentration, vacuum‐evaporation and reverse osmosis, heat sterilized, and stored during 3 months. The obtained results showed that the surface net charge of the proteins in milk concentrated by vacuum evaporation decreased during storage, while that of the other milks remained stable. The levels of free amino acids decreased as a function of the storage time for the three skim milk samples with a higher rate for the vacuum evaporated milk. Thiol groups were affected by sterilization, but remained stable during storage. After sterilization, the consistency coefficient of milk increased by 8.6, 2.25, and 2.35 times for evaporated milk, concentrated by reverse osmosis, and cryoconcentrated, respectively. This result indicated a more stability of sterilized cryoconcentrated skim milk in comparison with the other skim milk samples which showed a tendency to age thickening.Practical ApplicationsThe findings of this research work can be applied by the dairy industry to produce concentrated skim milk following a cryoconcentration procedure. This subzero concentrating technique can substitute vacuum evaporation and reverse osmosis. The advantage of cryoconcentration, as used in this work, is its low energy consumption and high product quality. Indeed, because of the low latent heat of freezing of water in comparison with its latent heat of vaporization (seven times lower), cryoconcentration is an effective energy saving technology. Thus, the dairy processing industry can exploit the advantages of cryoconcentration to develop novel dairy foods and to save energy.

A Mathematical Modeling of the Reverse Osmosis Concentration Process of a Glucose Solution

A mathematical modeling of glucose–water separation through a reverse osmosis (RO) membrane was developed to research the membrane’s performance during the mass transfer process. The model was developed by coupling the concentration–polarization (CP) model, which uses one-dimensional flow assumption, with the irreversible thermodynamic Spiegler–Kedem model. A nonlinear parameter estimation technique was used to determine the model parameters Lp (hydraulic permeability constant), σ (reflection coefficient), and Bs (solute transport coefficient). Experimental data were obtained from the treatment of a pre-treated glucose solution using a laboratory-scale RO system, and studies on the validation of the model using experimental results are presented. The calculated results are consistent with the experimental data. The proposed model describes the RO membrane concentration process and deduces the expression of k (mass transfer coefficient in the CP layer). The verification shows that the expression of k well-describes the reverse osmosis mass transfer of a glucose solution.

Cost and energy requirements of hybrid RO and ED brine concentration systems for salt production

A new concept to concentrate seawater up to 200 g/kg for producing vacuum salt using a reverse osmosis (RO) system hybridized with an electrodialysis (ED) system is presented. The RO system operates up to pressures of 120 bar and concentrates seawater up to 120 g/kg with the ED system concentrating RO brine to 200 g/kg. A parametric analysis to minimize the specific cost of brine concentration was conducted. Parameters varied were: the degree of RO-ED hybridization, ED current density, electricity prices and water prices. Optimal hybrid RO-ED designs reduced brine concentration costs by 33–70% over standalone ED systems, with revenue generated from water co-production further subsidizing costs by 1–6%. Optimizing ED current density reduced costs the most. Including a crystallizer, the total reduction in production cost over a standalone ED-crystallizer system was 19–55%, with the production cost for a typical case being $111/tonne-salt. The proposed RO-ED-crystallizer (REC) systems were found to be techno-economically feasible in Cyprus, Japan, Kuwait, Saudi Arabia, and the USA. At a road transportation distance of 735 km, REC based seawater vacuum salt was competitive with conventional vacuum salt. REC systems may open up the potential of small-scale decentralized salt production.

Treatment of landfill leachate RO concentration by Iron–carbon micro–electrolysis (ICME) coupled with H2O2 with emphasis on convex optimization method

ABSTRACTA combined technology between Iron-carbon micro-electrolysis (ICME) and H2O2 using scrap iron and granular active carbon was extensively investigated and optimized (three main independent parameters chosen) for chemical oxygen demand (COD) removal of landfill leachate reverse osmosis (RO) concentration by batch experiments. A regression quadratic equation was developed to model the outcome using central composite design (CCD) coupled with response surface methodology. A global optimization method–the convex optimization was applied to determine the optimal parameters. Under optimal parameters determined as C/Fe (Surface area) of 717143.8, H2O2 concentration of 1687.6 mg/L and pH of 3.8, the corresponding COD removal efficiency was up to 86.9%. Consequently, the COD in the effluent was less than 300 mg/L. The treated water can meet the level B standards of Wastewater Quality Standards for Discharge to Municipal Sewers (CJ 343—2010).

An environmentally friendly process for the production of extracts rich in phenolic antioxidants from Olea europaea L. and Cynara scolymus L. matrices

A sustainable extractive technology followed by membrane separation methods was applied to Olea europaea L. (leaves and pitted olive pulp) and Cynara scolymus L. by-products (leaves and stems), to obtain different standardized commercial extracts for application in the functional food industry, pharmaceutical and cosmetic fields. The entire treatment, PCT registered, consists of water extraction of the aforementioned vegetal material and the following steps of fractionation: (1) microfiltration (only for Olea); (2) ultrafiltration (only for Cynara); (3) nanofiltration (only for Olea); (4) reverse osmosis and final concentration by evaporation at low temperature or spray-dried technique. Thanks to these steps, different fractions enriched with phenolic compounds that have an economic value can be obtained. These fractions were characterized and quantified by HPLC/DAD-ESI/MS and then tested for their antiradical and antioxidant properties. The EC50 values by DPPH test were 6.76 × 10−3 mM for the Olea green leaves (GL) soft extract, 5.44 × 10−3 mM for the Olea dried leaves (DL) soft extract, and 1.22 × 10−3 mM in the case of the Olea OH-Tyr soft extract. The EC50 value of the Cynara GL soft extract was 3.25 × 10−3 mM. The ORAC results were 3632 ± 110.7 µmoL TE/g for OH-Tyr Olea soft extract, 1410 ± 62.1 µmoL TE/g for GL Olea soft extract, and finally 760 ± 12 µmoL TE/g for GL Cynara soft extract, confirming the highest antioxidant activity of hydroxytyrosol.

Zero Waste Membrane Technology for Whey Processing

Objectives: The study is currently significant insofar as it considers reprocessing of secondary resources represented by milk whey generated in bulk in the course of curd and cheese production. Methods: Zero waste method of whey reprocessing has been experimentally justified employing two stages of baromembrane technology: ultrafiltration at the first stage to recover macromolecular components followed by reverse osmosis concentration of lactose applying modern domestically produced membranes. Findings: The materials and methods for investigating the processes of ultrafiltration and reverse osmosis concentration of whey have been described. Proprietary solution has been suggested for whey ultrafiltration without its preliminary treatment using ceramic membranes of CUFE Type (ceramic ultrafiltration elements) (0.01). Optimum operating parameters for the processes of ultrafiltration and reverse osmosis concentration of whey have been experimentally established and verified in the workshop environment. A technological process for zero waste whey processing has been developed. The results of the experimental investigations have been discussed and the relevant conclusions have been made. Applications/Improvements: CUFE (0.01) ceramic membrane can be recommended as the most preferable technical solution for separating whey without any preliminary treatment during UF process. Recommendations are given for RO process conditions.

Olive mill wastewater concentration by two-stage reverse osmosis in tubular configuration, in a scheme combining open and tight membranes

A novel concept for olive mill wastewater (OMWW) concentration, involving the combination of open and tight reverse osmosis (RO) membranes in tubular configuration, was studied. The OMWW, prior to RO concentration, was clarified in two successive steps: passing through a coarse rotating finisher and by ceramic microfiltration, in order to remove suspended matter and facilitate the RO concentration. The clarified raw material was then concentrated using the tubular PCI UK AFC40 RO membrane. A parametric study was conducted to investigate the effect of main process parameters on permeation flux. The permeation flux of AFC40 RO membrane was found to reach consistently high values without substantial membrane fouling problems. Furthermore, the parametric study proved that the flux was linearly increased by increasing the transmembrane pressure, and exponentially decreased by increasing the OMWW mass concentration factor. In most cases, the permeation flux increased with increasing flow velocity. The effect of temperature on permeation flux was depended on both transmembrane pressure and flow velocity. The AFC40 permeate content of total dissolved solids (TDS) was approximately 0.6%, which accounts for roughly 15% of the TDS in the initial OMWW solution. The AFC40 permeate was, therefore, further concentrated using the AFC99 PCI UK tight RO membrane, aiming to obtain a permeate suitable for disposal to natural resources, whilst simultaneously reclaiming valuable antioxidants by mixing the two retentates of AFC40 and AFC99 membranes. The results of this study show that the proposed two-stage RO scheme may be potentially applied in a commercial scale and contribute towards processing of OMWW to produce liquid antioxidant and water suitable for disposal to natural resources.

Effect of reverse osmosis concentration coupled with drying processes on polyphenols and antioxidant activity obtained from Tectona grandis leaf aqueous extracts

Tectona grandis leaf extracts obtained at pilot scale processes (ultrasound-assisted extraction, cross-flow microfiltration, reverse osmosis concentration) contains phenolic compounds that exhibit antioxidant properties. The final reverse osmosis concentrate extract presented higher content of polyphenol (21,080±117μmolg−1 GAE) and antioxidant capacity (8490±29μmolg−1 TE) comparatively to crude extract (1300±12μmolg−1 GAE for polyphenol and 430±2μmolg−1 TE for antioxidant activity) or cross flow microfiltration extract (1170±10μmolg−1 GAE for polyphenol and 400±10μmolg−1 TE for antioxidant). The concentration factors of polyphenol and antioxidant capacity were 18 and 21, respectively. High-performance liquid chromatography (HPLC) coupled to electrospray ionization mass spectrometry (ESI-MS) detection negative ion mode has been used to identify and characterized polyphenols in the concentrate extract of T. grandis leaves. Seven phenolic acids and flavonoids were characterized. Verbascoside (phenolic acid) was described as the most abundant phenolic compounds in this concentrate extract. Two drying technologies (freeze-drying and spray-drying) were used to obtained stable powder from concentrate extract. The effect of these drying technologies on phenolic compounds and antioxidant activity were studied. Freeze-drying presented a good recovery of phenolic compounds and antioxidant capacity. This drying technology could be used for preservation of T. grandis extract.

Environmental and technical improvement of a grape must concentration system via a life cycle approach

Irregularities in grape yields can often affect wine production both quantitatively and qualitatively. Hence concentration systems, such as those based on reverse osmosis, are often employed to overcome such problems. The present study illustrates the results of a life cycle assessment approach implemented as means to improve the existing performance and sustainability of a specific industrial reverse osmosis concentration system used in a southern Italian winery to concentrate a specific must. The application of lifecycle approaches to reverse osmosis must concentration is sparsely documented in scientific literature with little or no specific data. The life cycle assessment of this study, developed using large amounts of inventory data and other novel information gathered from industrial testing, has highlighted the use phase as the most impacting one due to the energy consumption during the concentration operations and due to the membrane cleaning operations. In view of these results, the machine setup was improved and tested by varying the feed-flow velocity and the resulting new setup re-assessed via a life cycle approach. The final results exhibit the relationship between permeate production and feed flow velocity that does not appear to have been sufficiently investigated in other work found in literature regarding wine must. Specifically, the curve fitted to the experimental readings indicates that the maximum performance of the reverse osmosis system under analysis is achieved with a feed-flow velocity of approximately 2 m/s. Furthermore the new optimised setup of the machine lowered the environmental profile of all impact categories within a range from a minimum of 25.3% to a maximum of 26.7%, due to lower energy consumption, higher permeate production and reduced cleaning operations for the membranes. Concurrently to the environmental optimisation a technical improvement was identified, namely the substitution of the over-dimensioned piston pump, together with a potential reduction of purchase, running and labour costs of the optimised reverse osmosis system. Overall the study highlights the utility of analysing industrial machinery, such as reverse osmosis must concentration systems, from a life cycle analysis perspective, that can bring about not only environmental sustainability improvements but also technical and economic developments.

Ecotoxicology of Highly Treated Mine Waters: Lessons from an Australian Mine

Mining operations commonly treat mine water prior to discharging it to the environment. Results of biological toxicity tests and Toxicity Identification Evaluations have shown that environmental risks can still exist for these highly treated waters. We present examples for mine waters that were treated using high density sludge–microfiltration–reverse osmosis and brine concentration processes. While such treatment substantially reduces the primary toxicity of the water, three key factors that could affect environmental consequences may arise or persist: (1) residual contaminants may still be at toxic concentrations, (2) the bioavailability of residual contaminants may increase, and (3) the treated water may be nutrient or major ion deficient. Appropriate strategies for the management of these treated waters should consider that toxicity or other water quality risks may still exist and that these will differ from those of the untreated water.

Technique of Instantaneous Ultrasonic Extraction and Reverse Osmosis Concentration on Polyphenols of Chinese Herbs

Polyphenol is a kind of active compound widely existed in many Chinese herbs, easily destroyed by oxygen and heat. Extraction and concentration are key steps to protect it from destruction, and the costly energy consumption steps in the process of herbs. In order to save energy and improve polyphenol quality, instantaneous ultrasonic extraction (IUE) and reverse osmosis (RO) concentration are evaluated in this paper. IUE and RO were used to extract polyphenol separately from herbs of Phyllantuus urinaria L, leaves of Camellia sinensis L and root of Salvia miltiorrhiza Bunge. Gallic acid, EGCG and Tanshinol, the main components of polyphenols, were determined by HPLC. Their content and energy consumption were compared to that by same time water boiling (10min) or 60min ultrasonic extraction and vacuum concentration. IUE increased 1-3 times or 1-5 times polyphenol content and saved 1 or 6 times energy consumption more than the same time water boiling or 60min ultrasonic extraction. Compared with vacuum vaporization to the same solid matter content (15%), RO increased 2 times polyphennol content and consumed 1/10 times energy and 1/5 times time. Combination of IUE and RO shortens process time, significantly improves polyphenol quality and saves energy. It will be the beneficial method for polyphenol extraction and concentration of Chinese herbs.