Integrated Membrane Process Research Articles

Improving Specific Activity of Aspergillus carbonarius Polygalacturonase Using Polymeric Membranes

Microfiltration (MF) and ultrafiltration (UF) membranes were screened for improving the specific activity of polygalacturonases (PG) in the culture broth of Aspergillus carbonarius obtained after submerged fermentation. While 200 and 450 nm MF membranes eliminated some of the larger non-enzymatic proteins, 50 kDa UF membrane exhibited a marginal selectivity between the enzyme and other smaller proteins. The 450 nm MF and 50 kDa UF membranes selected were further evaluated under different process conditions for an integrated membrane process. The process efficacy of three different schemes was also studied for enzyme purification. A two-stage membrane process employing MF followed by UF improved the enzyme-specific activity (5,590 U/mg) by 4.69-fold eliminating the larger and smaller non-enzymatic proteins as well as non-protein impurities with a recovery of 76% enzymes, besides resulting in higher productivity. Thus, adoption of integrated membrane process with appropriate selection of membranes could result in high recovery of enzymes with improved specific activity.

Laboratory Studies on Membrane Deoiling of Lecithin

AbstractDeoiling of lecithin using a nonporous membrane was examined in a favorable solvent (hexane) medium with soy and rice bran lecithins. During the membrane process, the acetone insoluble (AI) content of soy lecithin increased from 63.2 to 81.0% in a single step batch operation. The membrane exhibited an excellent selectivity since phospholipid (PL) reverse micelles formed in the system were rejected almost completely due to low solubility probably aided synergistically by size exclusion. Diafiltration achieved greater oil removal from lecithin as reflected in terms of higher AI and PL contents in the deoiled lecithin. In discontinuous diafiltration, the PL content increased from 33.3 to 85.5% in rice bran lecithin (150% dilution to feed) and 56.6 to 85.7% in soy lecithin (200% dilution), respectively. The simulated continuous diafiltration run showed slightly greater PL content in soy lecithin (91.3%) compared to discontinuous diafiltration (89.7%) besides offering higher productivity. The membrane showed a color reduction of ~60% in soy lecithin but there was no improvement in rice bran lecithin due to the retention of degradation products. The proposed integrated membrane process with nonporous (deoiling) and nanofiltration (solvent recovery) membranes could be an attractive preposition besides being an acetone free process.

On the development of an integrated membrane process with ionic liquids for the kinetic resolution of rac-2-pentanol

A membrane bioreactor containing a supported liquid membrane based on ionic liquids was successfully applied to the kinetic resolution of rac-2-pentanol catalysed by a commercial immobilized Candida antarctica lipase B (Novozym 435). Variables affecting the performance of the above bioreactor were studied. First of all, six ionic liquids were tested for use as liquid membrane phase supported in a Nylon membrane for the selective transport of the compounds involved in the reaction. The most suitable liquid membrane phase for the selective separation of the target compounds was found to be [bmim +][BF 4 −]. The influence of the water content of the medium on the synthetic activity, selectivity and enantioselectivity of the enzyme was then analysed in order to establish the optimal amount of water. Finally, the integrated reaction/separation process for the resolution of rac-2-pentanol was carried out at the optimal conditions found, using vinyl propionate and vinyl butyrate as acyl-donors. The greatest efficiency was achieved with the longest vinyl ester, vinyl butyrate.

A new integrated membrane process for the production of concentrated blood orange juice: Effect on bioactive compounds and antioxidant activity

The production of high quality concentrated blood orange juice according to a new integrated membrane process, alternative to thermal evaporation, was evaluated in terms of preservation of the total antioxidant activity and of the bioactive antioxidant components of the juice (ascorbic acid, anthocyanins, hydroxycinnamic acids, flavanones). The process was based on the initial clarification of freshly squeezed juice by ultrafiltration (UF); the clarified juice was successively concentrated by two consecutive processes: first reverse osmosis (RO), used as a pre-concentration technique (up to 25–30 °Bx), then osmotic distillation (OD), up to a final concentration of about 60 °Bx. During the concentration process of the liquid fractions, a slight decrease of total antioxidant activity (TAA) was observed (−15%), which was due to the partial degradation of ascorbic acid (ca. −15%) and anthocyanins (ca. −20%). Nevertheless, this degradation was lower than that observed with thermally concentrated juice: TAA, −26%; ascorbic acid, −30%, anthocyanins, −36%. The possibility to operate at room temperature allowed reduction in thermal damage and energy consumption. On the basis of these results, the integrated membrane process may be proposed as a valuable alternative to obtain high quality concentrated juice, as the final product still showed a very high antioxidant activity and a very high amount of natural bioactive components, showing a brilliant red colour and a pleasant aroma, characteristics that were significantly lost during traditional thermal evaporation.

Integrated Membrane Process for the Recovery of Chromium Salts from Tannery Effluents

Conventional chrome tanning in leather production produces spent liquors containing significant amounts of chromium and other polluting substances, both organic and inorganic. The aim of this study was to identify a technically viable method for recovering chromium salts from spent tanning liquors. For this purpose, an integrated process based on a preliminary ultrafiltration (UF) treatment of the spent liquor followed by a nanofiltration (NF) treatment of the UF permeate was studied on the laboratory scale. The UF process permitted a marked reduction of suspended solids and fat substances to be obtained. A tanning solution with a chromium(III) concentration of about 10 g/L was obtained in the NF process. The concentrated chromium solutions were used in experimental trials of chrome tannage performed on pickled sheepskins (experimental group). Their properties were compared with those of skins (control group) treated with the conventional method using basic chromium sulfate powder. The NF retentate seems to guarantee improved characteristics of the tanned skins with respect to the control group. Furthermore, a higher percentage of chromium depletion was observed for the tanning operation performed with the NF retentate. The process also permitted the reuse of the NF permeate in the pickling step because of its high content of chlorides.

Chemical and operational aspects in running the polymer assisted ultrafiltration for separation of copper(II)–citrate complexes from aqueous media

The polymer assisted ultrafiltration (PAUF) process for treatment of wastewaters containing metal ions chelated with citric acid has been studied giving particular attention to the chemical and operational aspects. The polyethylenimine (PEI) polymer bound quantitatively the copper(II)–citrate chelate at pH 5.5 forming the ternary PEI–Cu–citrate complex as discussed considering the stability constants. The ternary complex was separated by UF membranes producing a permeate with very low metal concentration. Best performance was obtained with the Iris 30 membrane (permeate flux 167.4 L h −1 m −2; rejection 98.8%) by operating at 4 × 10 5 Pa (4 bar). The limiting concentration (maximum retentate concentration for obtaining a copper(II) concentration in the permeate lower than 1.3 mg L −1 corresponding to 2.04 × 10 −5 mol L −1), was 250 mg L −1 (3.93 × 10 −3 mol L −1) for Iris 30 membrane and 400 mg L −1 (6.29 × 10 −3 mol L −1) for Iris 10 membrane by operating with both constant trans-membrane pressure and constant permeate flow rate modes. The polymer regeneration was carried out with good results by operating with the diafiltration method and using both the membranes, but the Iris 30 membrane, operated at 4 × 10 5 Pa (4 bar), performed a little better owing to the higher flux. The copper ion present in the diafiltration permeate was recovered by oxidising the citrate in a membrane photoreactor. The obtained results permitted to draw an integrated membrane process combining complexation–UF–diafiltration–photocatalysis to treat metal containing wastewaters (e.g. washing water from soil remediation) for obtaining water recyclable in the process itself or safely discharged, recycling the polymer and recovering the metals.

Integrated membrane systems for seawater desalination: energetic and exergetic analysis, economic evaluation, experimental study

Currently over 12,500 industrial desalination plants, with an average production rate of 22.8 million m 3/d, are operating worldwide to alleviate water shortage problem. In this contest, pressure driven membrane operations are today largely utilized. They compete successfully with the more traditional thermal systems due to their lower energy consumption. However, critical issues still remain open: improvement of water quality and plant global recovery factor, reduction of desalted water cost and brine disposal problem. Recent developments make realistic to affirm that integrated membrane systems might offer one of the most reliable solution to solve these problems and also a sustainable development of desalination processes. Integrated membrane processes represent an attractive opportunity because of the synergic effects that can be reached, the simplicity of these units, the possibility of advanced levels of automation and remote control. In this logic well fit in also temperature driven membrane operations, such as membrane distillation and membrane crystallization: they allow increasing fresh water recovery factor, recovery of the crystals naturally present in the concentrated streams of the desalination plants, reduction of brine disposal cost and its negative environmental impact. In this work seven flow sheets for seawater desalination have been proposed, analysed and compared. In each of them different membrane units have been integrated in pre-treatment and post-treatment stages for reaching the process intensification goals, overcoming the limits of the single units and, thus, improving the performance of the overall desalination process.

Concentration of clarified kiwifruit juice by osmotic distillation

This study was undertaken in order to evaluate the potential of the osmotic distillation (OD) process for concentrating clarified kiwifruit juice on laboratory scale, taking into account the impact on the product quality especially in terms of ascorbic acid content and total antioxidant activity (TAA). The performance of the OD process in terms of flux and concentration factor was also evaluated. The clarified juice, with an initial TSS content of 9.4°Brix, was concentrated up to final values of 66.6°Brix, by using a laboratory bench plant equipped with a Liqui-Cell ® Extra-Flow 2.5 × 8 in. membrane contactor realised with polypropylene hollow fiber membranes. Calcium chloride dihydrate at 60 w/w% was used as stripping solution producing an initial evaporation flux of about 1.3 kg/m 2 h. The experimental data indicates that at low total soluble solids (TSS) concentration the evaporation flux decay is more attributable to the dilution of the stripping solution while, starting from a TSS value of 35°Brix, the evaporation flux depends mainly on juice viscosity and, consequently, on juice concentration. The analytical measurements showed that the OD process has no influence on the acid ascorbic content independently by the concentration degree achieved, while in the retentate at 66.6°Brix obtained by thermal evaporation a reduction of 87% of Vitamin C was observed with respect the clarified juice. Also the TAA of the clarified juice was maintained constant during the osmotic distillation process while a reduction of 50% of this activity was detected in the retentate samples coming from the thermal treatment. On the basis of the experimental results an integrated membrane process for the clarification and concentration of kiwifruit juice was proposed.

Integrated membrane process for the concentration of anthocyanin

Many natural colorants, which have been extracted from plant/vegetable sources, have more than 90% water in addition to the low tinctorial strength. Membrane technologies offer the potential of pigment concentration. In view of this, an attempt has been made to concentrate anthocyanin, a natural red colorant from red radish using integrated membrane process, which involves ultrafiltration (UF), reverse osmosis (RO) and osmotic membrane distillation (OMD). The effect of anthocyanin concentration on water flux in each process was studied. Comparison of UF, RO and OMD was made when they are operated individually and in combination with each other. It was observed that, the integrated membrane processes have the advantages of achieving higher concentration of anthocyanin compared to that of the individual membrane processes. Final concentration of 26 °B (from 1 °B) was achieved; which resulted an increase in the concentration of anthocyanin from 40 mg/100 ml to 980 mg/100 ml.

Integrated membrane process for the production of highly nutritional kiwifruit juice

The aim of this study has been to design, on a laboratory scale, an integrated membrane process for the production of concentrated kiwi juice and its aroma recovery. Fresh depectinised kiwifruit juice was clarified by the ultrafiltration (UF) process. The clarified juice was concentrated by osmotic distillation (OD), as an alternative to the traditional vacuum evaporation, up to a total soluble solids (TSS) content higher than 60 °Brix at 25°C. Pervaporation (PV) runs were carried out before and after each membrane unit operation in order to identify the best configuration giving the minimal loss of aroma compounds. For the majority of the aroma compounds detected, the enrichment factor in the permeate of the fresh juice was higher than the clarified and concentrated juice. This result suggests the use of PV for the removal and enrichment of aroma compounds directly from the fresh juice, before any concentration process. The effect of UF and OD on the total antioxidant activity (TAA) and ascorbic acid content of the kiwifruit juice was also evaluated. On the basis of the obtained results, an integrated membrane process scheme for the production of highly nutritional kiwifruit juice has been proposed.

Production of process water using integrated membrane processes

AbstractApplication of ultrafiltration, nanofiltration, reverse osmosis, membrane distillation, and integrated membrane processes for the preparation of process water from natural water or industrial effluents was investigated. A two-stage reverse osmosis plant enabled almost complete removal of solutes from the feed water. High-purity water was prepared using the membrane distillation. However, during this process a rapid membrane fouling and permeate flux decline was observed when the tap water was used as a feed. The precipitation of deposit in the modules was limited by the separation of sparingly soluble salts from the feed water in the nanofiltration. The combined reverse osmosis—membrane distillation process prevented the formation of salt deposits on the membranes employed for the membrane distillation. Ultrafiltration was found to be very effective removing trace amounts of oil from the feed water. Then the ultrafiltration permeate was used for feeding of the remaining membrane modules resulting in the total removal of oil residue contamination. The ultrafiltration allowed producing process water directly from the industrial effluents containing petroleum derivatives.

Technical and economical evaluation of an integrated membrane process capable both to produce an aroma concentrate and to reject clean water from shrimp cooking juices

Seafood industries generate effluents with a high organic polluting load. Among these, cooking juices contain potentially valuable aromas. Previous works have shown that a two-step integrated membrane process, combining a desalination by electrodialysis and a concentration by reverse osmosis, was technically feasible to recover natural marine aromas. This paper is focussed on a method allowing to estimate the membrane surface area needed to process a cooking juice with given characteristics (volume, concentrations of mineral and organic matter…) and then to estimate the process earning power. In the case of shrimp cooking juice concentration, such a process seems economically interesting as the pay-back time was shown to be inferior to three years.

Development of an integrated membrane process for water reclamation

An integrated membrane process (IMP) comprising a membrane bioreactor (MBR) and a reverse osmosis (RO) process was developed for water reclamation. Wastewater was treated by an MBR operated at a sludge retention time (SRT) of 20 days and a hydraulic retention time (HRT) of 5.5 h. The IMP had an overall recovery efficiency of 80%. A unique feature of the IMP was the recycling of a fraction of RO concentrate back to the MBR. Experimental results revealed that a portion of the slow- and hard-to-degrade organic constituents in the recycle stream could be degraded by an acclimated biomass leading to an improved MBR treatment efficiency. Although recycling concentrated constituents could impose an inhibitory effect on the biomass and suppress their respiratory activities, results obtained suggested that operating MBR (in the novel IMP) at an F/M ratio below 0.03 g TOC/g VSS.day could yield an effluent quality comparable to that achievable without concentrate recycling. It is noted in this study that the novel IMP could achieve an average overall TOC removal efficiency of 88.940% and it consistently produced product water usable for high value reuse applications.

Clarification and concentration of melon juice using membrane processes

Melon juice obtained from fruits discarded by exporters was first clarified by crossflow microfiltration and then concentrated by osmotic evaporation (OE). The resulting clarified melon juice was highly similar to the initial juice, except for insoluble solids and carotenoids, which were concentrated in the retentate. Average permeation flux was relatively high (about 80 L h −1 m −2), with continuous extraction of retentate at a volumetric reduction ratio of 3. After concentration of the clarified melon juice to as much as 550 g kg −1 of total soluble solids using a continuous feed-and-bleed procedure of OE, we found that almost the entire composition of the product was preserved. This integrated membrane process permitted two valuable products to be obtained: a clarified concentrate of melon juice that had not undergone any thermal treatment, and a glowing-orange retentate that was enriched in provitamin A. Industrial relevance The increasing quality demand for fresh fruits results in an increase in rejected melons. Juice processing could overcome the product losses occurring but thermal sensitivity of melon juice flavour prohibits conventional thermal processing. Interestingly this paper attempts to use membrane processes for microbial stabilisation and concentration. The authors present a novel way of using permeate (clear juice) as well as retentate (pulpy juice). Enzyme activities in the products during and after processing may need some attention prior to industrial application of the process.

Comparative performance of non-dispersive solvent extraction using a single module and the integrated membrane process with two hollow fiber contactors

Hollow fiber non-dispersive solvent extraction (HFNDSX) was carried out with one module (batch process) using (0.562 M) 18% LIX79/ n-heptane by passing Ag(CN) 2 − alkaline feed through the tube side and organic extractant through the shell side in counter-current mode. Similarly, stripping was done by passing NaOH through the tube side and loaded organic through the shell side using the same module after washing (in batch operation). On the other hand, in the integrated membrane process (IMP), non-dispersive solvent extraction of silver cyanide and stripping of silver cyanide from organic complex were performed simultaneously using two hollow microporous hydrophobic polypropylene fiber contactors each for extraction and stripping, respectively. The overall mass transfer coefficient obtained in the integrated process was observed to be greater than the values of the mass transfer coefficient ( K Ag E ) obtained with the single module (no stripping). The various hydrodynamic and chemical parameters, such as linear flow velocity of the feed aqueous phase (3.07 cm/s ≥ υ f ≥ 0.92 cm/s), linear flow velocity of the organic phase (1.18 cm/s ≥ υ f ≥ 0.39 cm/s), NaCN concentration in the feed, pH variation in the aqueous feed and NaOH concentration in the stripping phase, were optimized in the single module. Some selective experiments were performed with two modules in order to compare the performance of IMP with that of HFNDSX. The mass transfer coefficients were calculated under different hydrodynamic and chemical conditions with a single module, and rate-controlling steps in extraction and stripping were identified. Similarly, the mass transfer coefficients were evaluated using IMP and attempts were made to solve operational problems with HFNDSX using a single module in counter-current mode.

Production of concentrated kiwifruit juice by integrated membrane process

The concentration of fruit juices is industrially performed in order to reduce storage, packaging, handling and shipping costs. This paper describes the research efforts to develop and optimise an integrated membrane process, on laboratory scale, for the production of concentrated kiwifruit juice as alternative to the traditional vacuum evaporation. Fresh depectinated kiwifruit juice was previously clarified by ultrafiltration (UF) process. In experimental tests performed according to the total recycle mode the effect of transmembrane pressure, axial flow-rate and temperature on permeate fluxes were studied. Clarified kiwifruit juice was produced in experimental tests carried out according to the batch concentration mode working in optimal operating and fluid dynamic conditions. The osmotic distillation (OD) process was used to concentrate the clarified juice up to a total soluble solids (TSS) content higher than 60 °Brix at 25 °C. The effect of various operating parameters on vapour flux was studied. An average evaporation flux of almost 1 kg/m 2 h was obtained using a calcium chloride dihydrate at 60 w/w% as brine solution. The effects of UF and OD processes on the total antioxidant activity (TAA) and other analytical parameters of the kiwifruit juice were also studied. A little reduction of the TAA was measured during the membrane treatment; vitamin C content was well preserved in the concentrated juice. On the basis of the results obtained on laboratory scale an integrated membrane process scheme for the clarification and the concentration of kiwifruit juice is proposed.

Effect of feed pH on an integrated membrane process for the reclamation of a combined rinse water from electroless nickel plating

This study explored the effect of feed pH on an integrated membrane process of ultrafiltration/reverse osmosis (UF/RO) for the reclamation of spent rinse water from an electroless nickel-plating operation. Feed pH in the range of 2.54–6.64 was investigated. For UF pre-treatment, the experimental results showed that iron was not rejected by UF membrane when feed pH was below 3.68. However, when feed pH was raised to 3.68, iron rejection increased significantly and reached 98.7% at pH 6.64. For the RO process, it was found that for a particular wastewater containing weak acids and weak bases in this study, permeate pH was higher than the feed pH when the feed pH was low, but lower than the feed pH when the feed pH had reached 6.64. The critical point at which permeate pH would be equal to feed pH was about 6. This observation has not been reported previously. An attempt at explaining the observation was offered. The results showed that concentration of all measured contaminants in RO permeate decreased with an increase in feed pH. As a consequence, the permeate conductivity decreased with increasing feed pH. The membrane flux decreased with increasing feed pH. Total organic carbon (TOC) rejection increased with increasing feed pH due to the enhanced electrostatic repulsion between the negatively charged membrane surface and the negatively charged HOCH 2CO 2 −. Moreover, the caustic soda consumption used for neutralization could be reduced by 39% in the integrated membrane process if the feed pH was set at 3.68 instead of 6.64. It was concluded that pH of the feed had a significant effect on the integrated membrane UF/RO process and the optimum pH of feed water for the treatment was in the range of 3.7–5.6.

Removal of Giardia and Cryptosporidium in drinking water treatment: a pilot-scale study

Giardia and Cryptosporidium have emerged as waterborne pathogens of concern for public health. The aim of this study is to examine both parasites in the water samples taken from three pilot-scale plant processes located in southern Taiwan, to upgrade the current facilities. Three processes include: conventional process without prechlorination (Process 1), conventional process plus ozonation and pellet softening (Process 2), and integrated membrane process (MF plus NF) followed conventional process (Process 3). The detection methods of both parasites are modified from USEPA Methods 1622 and 1623. Results indicated that coagulation, sedimentation and filtration removed the most percentage of both protozoan parasites. The pre-ozonation step can destruct both parasites, especially for Giardia cysts. The microfiltration systems can intercept Giardia cysts and Cryptosporidium oocysts completely. A significant correlation between water turbidity and Cryptosporidium oocysts was found in this study. The similar results were also found between three kinds of particles ( Φ=3–5,5–8 and 8– 10 μm ) and Cryptosporidium oocysts.

Conventional versus advanced treatment for eutrophic source water

The Cheng Ching Lake Water Works in southern Taiwan draws its raw water from an eutrophic lake. There are taste and odor problems in the finished water because the conventional treatment processes currently used cannot completely remove the metabolites of algae or other microorganisms. Consumers also complain about the high levels of hardness in the water. To improve the organoleptic properties of the finished water by upgrading the treatment processes, a pilot‐scale study was conducted. Three processes were compared side by side: a conventional process without prechlorination (process 1); a conventional process plus ozone, granular activated carbon, and pellet‐softening (process 2); and an integrated membrane process (ultrafiltration plus nanofiltration) following a conventional process (process 3). Results showed that process 3 produced water with the best quality, whether dissolved organics, biostability, or organoleptic parameters were concerned. The second‐best results occurred with process 2, which produced water with high biostability and aesthetic quality. The study also found that simply avoiding prechlorination significantly improved the biostability of the finished water when compared with that of conventional processes.

Clarification and concentration of citrus and carrot juices by integrated membrane processes

The use of integrated membrane processes for the clarification and the concentration of citrus (orange and lemon) and carrot juices is proposed as an alternative to the traditional techniques of the agro-food industry. The ultrafiltration (UF) process was studied on a pilot plant unit to clarify the raw juice. A limpid phase was produced in this step and it was used for concentration by successive membrane treatments. The reverse osmosis (RO) process, performed on a laboratory plant unit, was used to preconcentrate the permeate coming from the UF step up to 15–20 g TSS/100 g. A final osmotic distillation (OD) step yielded a concentration of the retentate coming from the RO up to 60–63 g TSS/100 g at an average throughput of about 1 kg h m −2. This laboratory unit was mainly used to develop operational parameters for the design of a full-scale plant and, secondly for the production of sample concentrates for their testing and evaluation. The results obtained in the experimental tests concerning the identification of membrane modules, the operating and fluid-dynamic conditions and cleaning procedures of membrane modules, are reported and discussed. The performance of the membrane modules was evaluated on the basis of productivity, quality of the product (evaluation of the antioxidant activity) and fouling characteristics. On the blood orange juice samples it was demonstrated that the total antioxidant activity (TAA) of juices concentrated by evaporation is lower than that of the fresh juice. During the UF process TAA was maintained, with respect to the fresh juice, both for the permeate and for the retentate. A little decrease of the TAA was observed in the RO treatment, probably on account of the high pressure employed during the process. After this step the subsequent concentration treatment by OD did not induce any significant changes to TAA independently from the final concentration obtained. Moreover, the juices concentrated by membrane technology retained their colour and large part of their aroma which is on the contrary lost during thermal concentration. According to the results obtained, it is possible to suggest an integrated membrane process that, starting from the raw juice, yields concentrated juices of high quality and high nutritional value. The residual fibrous phase coming from the UF process could be submitted to a stabilising treatment and reused for the preparation of beverages enriched in fibres. Advantages are in terms of: reduction of clarification times, simplification of the clarification process, increasing of clarified juice volumes, the possibility of operating at room temperature and preserving the juice freshness, aroma and nutritional value, improvement of the quality of the final product through the removal of extraneous substances and improvement of the production processes.