Use Of Nanofiltration Membranes Research Articles

Application of nanofiltration to produce water for drinking and industrial needs of urban economy

The issues associated with the operation of reverse osmosis plants at the water intake facilities (WIF) for the treatment of drinking water from groundwater sources are described. Ways of increasing reverse osmosis plants performance are considered. The technology of plants modernisation with the purpose of operational costs reduction and minimisation of concentrate discharges into sewerage system, consisting in replacement of reverse osmosis (RO) membranes with nanofiltration membranes, is provided. The use of nanofiltration membranes reduces the intensity of sedimentation and at the same time the concentrate flow without the sedimentation hazard. Also, nanofiltration membranes make it possible to reduce inhibitor dosage and operation costs respectively. Experimental studies on groundwater treatment and efficiency of the provided technology have been carried out. Rates of sedimentation in each device of the layout, as well as composition of water treated by each device depending on the volume reduction factor K (source water flow to the concentrate flow ratio) for the plant were determined. The feasibility comparative study considered the following parameters of the plant operation, without limitation: inhibitor dosage, membrane types, salt selectivity of membranes, source water volume reduction factor K.

Production of Drinking Water with Membranes with Simultaneous Utilization of Concentrate and Reject Effluent after Sludge Dewatering.

A new technology is described that enables us to completely exclude liquid discharges during production of drinking water from surface sources. The proposed described technological scheme separates the natural water into a stream of purified drinking water and dewatered sludge. The sludge moisture has a value of 80 percent. The experimental program is described to treat the natural water with nanofiltration membranes and to produce a drinking-quality water with recovery value of 0.99 and higher. Concentrate of membrane plant is mixed with the wet sludge and the reject effluent after sludge dewatering is again treated by reverse osmosis membranes and returned back to the sludge thickening tank. Results of experiments to treat reject water after sludge dewatering are presented. The use of nanofiltration membranes provides reduction in the Total Dissolved Solids content (TDS), aluminum, color and oxidation to meet drinking water standards. Experimental plots are presented that can be used to select membrane characteristics and to predict product water chemical composition at each stage of the membrane treatment scheme. Concentrate of membrane treatment plant is mixed with the wet sludge in the thickening tank. The sludge, after the thickening tank, is dewatered using either filter-press or centrifugal equipment. The reject (or fugate), after sludge dewatering, is treated by membrane facility to separate it into deionized water stream and concentrate stream. The deionized water can be mixed with the feed water or drinking water and the concentrate stream is returned back to the thickening tank. Thus, the salt balance is maintained in the thickening tank, whereby all dissolved salts and impurities that are rejected by membranes are collected in the thickening tank, and then are withdrawn together with the dewatered sludge. Based on the results of experimental data processing, balance diagrams of the sludge dehydration process with waste water purification at the membrane plant and with the addition of the membrane plant concentrate to the sludge thickener are presented, according to which all contaminants removed by the membranes are removed together with the sludge.

The Selection of Efficient Antiscalant for RO Facility, Control of Its Quality and Evaluation of the Economical Efficiency of Its Application.

Adsorption of polymeric inhibitor molecules to calcium carbonate crystal surface was investigated. Inhibiting efficiencies of phosphonic acid-based antiscalants are dependent on the amount of adsorbed material on the growing crystal surface. A strong antiscalant even at a small dose provides the necessary rate of adsorption. Comparison of two phosphonic-based antiscalants was made both in laboratory and industrial conditions. A distinguishing feature of the strong antiscalant is the presence of aminotris (metylene-diphosphonic acid) ATMP. Experimental dependencies of antiscalant adsorption rates on the antiscalant dosage values were determined. Emphasis is given to the use of nanofiltration membranes that possess lower scaling propensities. Modernization is presented to reduce operational costs due to antiscalant and nanofiltration membranes. The main conclusion is that control of scaling should be implemented together with the use of nanofiltration membranes.

Nanofiltration as an Efficient Tertiary Wastewater Treatment: Elimination of Total Bacteria and Antibiotic Resistance Genes from the Discharged Effluent of a Full-Scale Wastewater Treatment Plant

Wastewater reuse for agricultural irrigation still raises important public health issues regarding its safety, due to the increasing presence of emerging contaminants, such as antibiotic resistant bacteria and genes, in the treated effluents. In this paper, the potential for a commercial Desal 5 DK nanofiltration membrane to be used as a tertiary treatment in the wastewater treatment plants for a more effective elimination of these pollutants from the produced effluents was assessed on laboratory scale, using a stainless steel cross-flow cell. The obtained results showed high concentrations of total bacteria and target carbapenem and (fluoro)quinolone resistance genes (blaKPC, blaOXA-48, blaNDM, blaIMP, blaVIM, qnrA, qnrB and qnrS) not only in the discharged, but also in the reused, effluent samples, which suggests that their use may not be entirely safe. Nevertheless, the applied nanofiltration treatment achieved removal rates superior to 98% for the total bacteria and 99.99% for all the target resistance genes present in both DNA and extracellular DNA fractions, with no significant differences for these microbiological parameters between the nanofiltered and the control tap water samples. Although additional studies are still needed to fully optimize the entire process, the use of nanofiltration membranes seems to be a promising solution to substantially increase the quality of the treated wastewater effluents.

Reducing operating costs through modernization of reverse osmosis facilities used to produce drinking water

Introduction. The authors address problems of operation of reverse osmosis facilities, used to treat ground water and produce drinking water; they also focus on operating cost reduction strategies. Nanofiltration membranes may reduce operating costs, concentrate consumption, and sedimentation. A smaller antiscalant dosage can also reduce the cost of chemicals. The purpose of this research is to evaluate the ecological and economic efficiency of the new technique.
 Materials and methods. The authors conducted groundwater treatment experiments to reduce groundwater hardness and ammonia content. Scaling rates and the composition of water, produced by each membrane module, were determined in each membrane module depending on coefficient K values.
 Results. The relationships, identified in the course of experiments, enabled the authors to calculate the number of membranes required to reach the designed efficiency value. The design of a membrane facility, tailored to a certain groundwater composition, is presented; membrane models and treatment efficiency values are identified. The use of nanofiltration membranes reduces the operating costs by 40 percent due to the lower consumption of antiscalants, power, and concentrate.
 Conclusions. The research has proven that the replacement of reverse osmosis membranes by nanofiltration membranes at the water treatment facilities in operation ensures a 40–50 percent increase in their production capacity. The water quality remains the same and meets the WHO standards. Also, the concentrate consumption rate goes down 10–20-fold. The authors have also found out that the use of nanofiltration membranes reduces the water hardness and ammonia content at lower pressure values and scaling rates, although the safe operation and higher efficiency are in place. The proposed modernization strategy reduces operating costs by 40–50 percent through membrane replacement without any changes in the membrane design.

ECONOMICAL AND ENVIRONMENTAL BENEFITS OF POINT-OF-USE NaCl BRINE REUSE BY NEW MEMBRANE TECHNOLOGY

Cation exchange water softening is one of the most widely used technologies of water treatment. However, its environmental impact related to discharge of highly concentrated regeneration brine draws more attention as overall quality and availability of water resources decreases. Bearing in mind high levels of reusable NaCl in brine discharge, technology that will reduce the environmental impact and help reuse brine is required. To develop such technology composition of spent brine solution from Na-cation exchanger was investigated and conditioning of such solution with use of nanofiltration membranes of different types under different temperatures, pressures and recovery values was tested. Results show that optimal conditions for NaCl recovery include usage of DuPont (Dow) Filmtec Fortilife XC-N membrane elements at temperature 23-27 °С, pressure of 23-25 bar and recovery of 55-60 %. Under these conditions purity of NaCl in permeate over 90 % and productivity by NaCl of 13.1 kg/h were achieved. Principal technological scheme of the process of membrane conditioning of the spent regeneration solution was proposed that allows achieving reduction of NaCl consumption by 40 % and reduction of NaCl discharge into sewage by 72 % with corresponding economic and environmental benefits.

Economic aspects of landfill leachate treatment using reverse osmosis membranes

Introduction. Landfill leachates contain highly concentrated organic products of waste degradation and mineral salts. Concentrations of organic matter demonstrate high COD values up to 5,000 mg/l, concentrations of ammonium ions reach 2,500 mg/l, while the total salt content may reach 15,000 mg/l. Two to three reverse osmosis treatment stages may be nee­ded to produce the water that meets effective regulations governing the composition of water discharged into the environment. Also, high salt content and COD values dramatically reduce the membrane capacity. The co-authors explored the use of nanofiltration membranes at the first stage of the leachate treatment in an effort to reduce membrane operation costs.
 Materials and methods. The experiments, conducted within the framework of this research undertaking, allowed to identify a change in the concentrations of contaminants, dissolved in the leachates of reverse osmosis and nanofiltration membranes, as well as the reduced capacity of membranes at each stage of treatment. The co-authors have studied the alternative methods that may ensure maximal reduction of the concentrate consumption in the process of leachate treatment. Principal dependencies, derived as a result of the research, enabled the co-authors to identify the concentrate consumption rates depending on the extent of treatment focused on ammonium ions. The co-authors describe the methodology employed to identify the area of membranes at each treatment stage depending on the leachate composition.
 Results. Calculations of operating costs are provided for three compositions of leachates, typical for the Moscow region, depending on the treatment methodology and further recovery of membrane concentrates.
 Conclusions. Nanofiltration membranes can be used at the first stage of the landfill leachate treatment in the case of high COD and salt content. The application of nanofiltration membranes allows to reduce the concentrate consumption rate and cut operating costs. A new technology is developed to split the concentrate into two flows: the flow that has a high organic matter content, and the flow that has a high content of mineral salts, sodium and ammonium chlorides in order to facilitate the recovery of the concentrate.

Prediction of rejection properties and performance of nanofiltration membranes based on scaling prognosis in drinking water treatment

Reverse osmosis (RO) and nanofiltration (NF) are widespread for drinking water production from underground water sources; these techniques are used to reduce hardness, iron, fluoride, ammonium, strontium, nitrate, pesticides etc. At the same time, with high efficiency of removing iron, hardness, fluoride, ammonium from source water, nanofiltration membranes are much less exposed to the risk of calcium carbonate precipitation than the traditionally used low-pressure RO membranes. Usually it is important to predict the rejection properties of membranes not only at the launch time of RO/NF unit, but during all operation period and gradual membrane fouling/scaling. The article presents experimental data on determining membrane selectivity (nanofiltration membrane OPMN-K, Russia) for iron. fluoride and ammonium depending on the TDS, water hardness and the amount of calcium carbonate precipitate in the membrane module. Operational guidance has been developed that allow to determine the costs of chemicals for the operation of NF installations depending on the source water quality and membrane type. The above calculations show that the use of nanofiltration membranes instead of reverse osmosis can significantly reduce the cost of operating groundwater treatment facilities.

ECONOMIC AND ENVIRONMENTAL BENEFITS OF NACL BRINE REUSE BY NEW MEMBRANE TECHNOLOGY

Article history:Received 23 April 2019 Accepted 18 May 2019Print 24 June 2019Cation exchange water softening is one of the most widely used technologies of water treatment. However, its environmental impact related to discharge of highly concentrated regeneration brine draws more attention as overall quality and availability of water resources decreases. Bearing in mind high levels of reusable NaCl in brine discharge, technology that will reduce the environmental impact and help reuse brine is required. To develop such technology composition of spent brine solution from Na-cation exchanger was investigated and conditioning of such solution with use of nanofiltration membranes of different types under different temperatures, pressures and recovery values was tested. Results show that optimal conditions for NaCl recovery include usage of Dow Filmtec Fortilife XC-N membrane elements at temperature 23–27 °C, pressure of 23–25 bar and recovery of 55–60%. Under these conditions purity of NaCl in permeate over 90% and NaCl yield of 13,1 kg/h were achieved. Principal technological scheme of the process of membrane conditioning of the spent regeneration solution was proposed that allows achieving reduction of NaCl consumption by 40% and reduction of NaCl discharge into sewage by 72% with corresponding economic and environmental benefits.

Application of polymeric membranes for the purification of solutions containing cationic surfactants.

The aim of the study was to examine physicochemical properties of three cationic surfactants and to evaluate the effectiveness of their removal with the use of polymeric membranes. The experiments were performed in a laboratory scale set-up with the use of Microdyn-Nadir® nanofiltration and ultrafiltration membranes. Cetrimonium bromide (CTAB), benzalkonium chloride (BAC) and Tequat LC90i (TEAQ) were chosen for the test. In the experiments, surfactant solutions in a wide range of concentration were treated (50-3,000 mg L-1). The experimental research included evaluation of the effect of membrane type and solution parameters (surfactant type and concentration, presence of inorganic compounds) on the process efficiency (retention coefficient and permeate flux). It was shown that surfactant removal by means of the pressure-driven membrane processes is an extensive issue and its efficiency depends on many factors. Ultrafiltration and nanofiltration membranes proved to be usable in CTAB removal (separation exceeded 90%); however, the process effectiveness was affected by surfactant concentration, membrane polymer type and membrane pore size. Separation obtained for BAC was on the lower level - the use of nanofiltration membranes brought maximum retention of 70%. TEAQ separation was very high and reached 100% with the use of ultrafiltration membranes. Mineral salt addition led to significant drop in surfactant retention.

The use of nanofiltration membranes for the fractionation of polyphenols from grape pomace extracts

Filtration experiments in batch concentration mode (with recycling of the retentate stream) of grape pomace extract were performed in laboratory filtration membrane equipment by using nine commercial nanofiltration (NF) membranes with an approximate molecular weight cut-off (MWCO) of 1000‒150 Da. The filtration experiments of the selected pomace extract were performed by modifying the most important operating variables: transmembrane pressure, tangential velocity, temperature, and the nature and MWCO of the membranes. The evolution of the cumulative permeate volumes and permeate fluxes with processing time was analyzed till a volume reduction factor (VRF) of 10 was reached. The effect of the mentioned operating conditions was discussed. The effectiveness of the filtration treatments was determined by the evaluation of the rejection coefficients for several families of polyphenols. Membranes possessing MWCO between 1000 and 500 Da were able to quantitatively recover polymeric proanthocyanidins in the concentrate stream and separate them from phenols that passed through the membrane into the permeate stream. On the other hand, the 600 to 300 Da membranes could also be used for the fractionation of monomeric phenolic families. The membranes were able to partially remove the anthocyanin fragments of phenolic acid derivatives and flavonols in the concentrate stream and at the same time.

Nanocomposite membranes of polydopamine/electropositive nanoparticles/polyethyleneimine for nanofiltration

Nanocomposite membranes (NCMs) provide inspiration to combine the superiorities of inorganic nanomaterials and polymeric matrices for outstanding nanofiltration performance. Herein, novel NCMs have been fabricated via co-deposition of polydopamine (PDA), polyetheylenimine (PEI) and electropositive gold nanoparticles (GNPs) followed by crosslinking. The GNPs distribute in the formed selective layer uniformly without obvious aggregation due to their good dispersion and compatibility with the positively charged PDA/PEI matrix. Thus the selective layer remains defect-free and the surface potential is enhanced by the positively charged GNPs. These endow the NCMs with high retention ratio (> 90%) for bivalent cations, such as Mg2+, Ca2+, and various heavy metal ions. Meanwhile, the permeate flux of the NCMs doubles compared with the PDA/PEI co-deposited nanofiltration membranes (NFMs) attributed to the hydrophilicity of the embedded GNPs and the loosened selective layer structures. The compact resistance and the structural stability of the NCMs are also improved effectively in contrast with the PDA/PEI ones, which are of significant importance for the practical use of NFMs. Moreover, the quaternary amine moieties on GNPs improve the antibacterial activity of NCMs against S. aureus and E. coli.

Use of nanofiltration membranes to concentrate and recover leached aluminum from acidified water treatment sludge

Use of nanofiltration membranes to concentrate and recover leached aluminum from acidified water treatment sludge

Use of nanofiltration membranes to concentrate and recover leached aluminum from acidified water treatment sludge

Use of nanofiltration membranes to concentrate and recover leached aluminum from acidified water treatment sludge

Separation of Xylose From Glucose Using Thin Film Composite (TFC) Nanofiltration Membrane: Effect of Pressure, Total Sugar Concentration and Xylose/Glucose Ratio

Xylose is an abundant raw material coexists with other sugars that can be turned into useful products, such as ethanol, xylitol and 2, 3-butanediol by microorganism such as yeasts, bacteria, and mycelial fungi. However, more than 80 % of the production cost of these products comes solely from the production of xylose. Presently, the separation of xylose from hemicellulose hydrolysate relies on chromatographic separation alone. The use of nanofiltration membrane may offer alternative in recovering xylose due to the differences in size compared to other sugars. The aim of this study is to evaluate the ability of membrane developed by interfacial polymerization reaction between triethanolamine (TEOA) (6 % w/v) and tri-mesoyl chloride (TMC) (0.15 % w/v) as monomers on polyethersulfone (PES) microporous substrate to separate xylose from glucose. In this study, factors affecting the process, namely pressure, concentration of total sugars in solution, and composition of monosaccharides in total sugar, were investigated using two-level factorial analysis. The experiment was performed using Amicon Milipore stirred cell (Model 8200) with constant stirring speed at 300 rpm and temperature at ambient. The glucose and xylose concentration was quantified using high performance liquid chromatography (HPLC). It is found that the developed nanofiltration membrane has the ability to separate xylose from glucose.The analysis of the experimental response revealed that the total sugar concentration and composition ratio of xylose: glucose had significant interactive effect on xylose separation factor. Overall from the present study, it can be concluded that nanofiltration has high potential to replace currently in use chromatographic method in xylose separation.

Sugar concentration and detoxification of clarified biomass hydrolysate by nanofiltration

Development of efficient unit operations is critical in order to design economically viable processes for conversion of lignocellulosic biomass into chemicals and fuels. Here the use of nanofiltration membranes for concentration of sugars in a lignocellulosic biomass hydrolysate has been explored. In addition, simultaneous removal of compounds such as acetic acid, 5-(hydroxymethyl)furfural and furfural which are inhibitory to the microorganisms used in the subsequent fermentation step has also been investigated. Dead-end filtration experiments have been used to test a number of commercially available nanofiltration membranes under a range of operating conditions. Model feed streams as well as real hydrolysates have been tested. The results obtained here indicate that both concentration of sugars and removal of hydrolysis degradation products are feasible. However careful selection of the membrane and operating conditions are essential. The introduction of a nanofiltration step for concentration of sugars and removal of hydrolysis degradation products could enable the development of a continuous process for biomass hydrolysis.

Concentration of biologically active compounds extracted from Ilex paraguariensis St. Hil. by nanofiltration

The aim of this study was to characterise the bioactive compounds in mate (Ilex paraguariensis St. Hil) extract and in concentrated mate extract obtained by nanofiltration (NF). Also, the impact of NF on the antioxidant activity of both mate extracts was evaluated in vitro and using eukaryotic cells of Saccharomyces cerevisiae (yeast assay). The results showed a significant increase in the contents of total phenolics (338%), chlorogenic acid (483%), theobromine (323%), caffeine (251%), chlorophyll (321%), condensed tannins (278%) and saponins (211%) in the concentrated mate extract. The concentrated mate extract showed higher in vitro antioxidant activity than the mate extract. According to the results obtained, it can be stated that the use of nanofiltration membrane is a valid approach for the concentration of biologically active compounds in aqueous extract of mate.

Experimental study of dye removal from industrial wastewater by membrane technologies of reverse osmosis and nanofiltration

Currently, biological method has been utilized in the treatment of wastewater -containing synthetic dyes used by textile industries in Iraq. The present work was devoted to study the operating feasibility using reverse osmosis (RO) and nanofiltration (NF) membrane systems as an alternative treatment method of wastewater discharged from Iraqi textile mills. Acid red, reactive black and reactive blue dyes were selected, based on the usage rate in Iraq. Effects of dye concentration, pH of solution, feed temperature, dissolved salts and operating pressure on permeate flux and dye rejection were studied. Results at operating conditions of dye concentration = 65 mg/L, feed temperature = 39°C and pressure = 8 bar showed the final dye removal with RO membrane as 97.2%, 99.58% and 99.9% for acid red, reactive black and reactive blue dyes, respectively. With NF membrane, the final dye removal were as 93.77%, 95.67%, and 97% for red, black and blue dyes, respectively. The presence of salt (particularly NaCl) in the dye solution resulted in a higher color removal with a permeate flux decline. It was confirmed that pH of solution had a positive impact on dye removal while feed temperature showed a different image. A comparison was made between the results of dye removal in biological and membrane methods. The results showed that membrane method had higher removal potential with lower effective cost. The present study indicates that the use of NF membrane in dye removal from the effluent of Iraqi textile mills is promising.

O21 Fractionnement alimentaire, satiété et métabolisme

Nanofiltration (NF) is a pressure-driven membrane operation with separation characteristics between those of reverse osmosis and ultrafiltration widely used for several applications such as water softening and wastewater treatment. With the increased demand for products with greater nutritional value and environmentally friendly processing procedures, NF has become a reliable and technoeconomically attractive operation in the food processing industry for the fractionation, concentration, and purification of different products and byproducts.In this chapter an overview of NF applications in some selected areas of food processing, such as fruit juice clarification, and the dairy, sugar, and wine industries, is given in the light of the recent developments on pilot and large scale investigations. Recent advances on the use of NF membranes for the recovery of functional compounds from agro-food byproducts are also included. Key advantages which can be achieved in both stand-alone and integrated systems over conventional technologies are analyzed and discussed.

Selectivity of polyamide nanofiltration membranes for cations and phosphoric acid

The results shown in this paper are part of a study to investigate the use of nanofiltration membranes for the recycling of phosphorus from sewage sludge. It especially contains the results of an experimental study about the influencing factors pressure, pH and feed composition on the selectivity of nanofiltration membranes for phosphoric acid and multivalent cations. For the use of pretreated sewage sludge an effective pressure of 11 bar could be identified as an effective operational point. The selectivity turned out to increase with decreasing pH which was studied in a pH-interval of pH 1–4. An increasing concentration of multivalent cations in the feed solution had a negative effect on the permeability of phosphoric acid. Accordingly it could be observed that the nanofiltration worked significantly more effective with sewage sludge ash eluates of the concentration 10 g/l than eluates of the concentration 100 g/l.