A preliminary comparison between nanofiltration and reverse osmosis membranes for grape juice treatment

Modelling of arsenic (III) removal from aqueous solution using film theory combined Spiegler-Kedem model: pilot-scale study

Arsenic contamination in drinking water is recognized as major health hazard worldwide. As reported in literature, more than 19% Indians are consuming lethal levels of arsenic for drinking purposes. In this work, arsenic (III) removal was studied using HFN300 polyethersulfone nanofiltration membrane in spiral wound configuration. Various membrane parameters such as hydraulic permeability (4.87 L m^-2 h^-1 bar^-1), mass transfer coefficient (0.957*10^-6 m s^-1), reflection coefficient (0.9), and solute permeability (2*10^-9 m s^-1) were estimated using film theory combined Spiegler-Kedem (FTCSK) model. The higher value of reflection coefficient suggested the impervious nature of nanofiltration (NF) membrane used for arsenic (III) solute rejection. The influence of various operating parameters such as transmembrane pressure, initial feed concentration, and feed flowrate on membrane performance was also examined. It was found that arsenic (III) rejection was dependent on pressure and feed concentration. Result showed that more than 96.4% arsenic (III) rejection was achieved for 50 mg L^-1 of feed at optimized conditions. As HFN300 membrane was negatively charged at pH 8 and arsenic (III) was available in neutral solute form, electro-migration was not considered for solute rejection mechanism. Solution diffusion with significant coupling between solute and solvent, steric hindrance effect, convection, and solute-membrane affinity interactions were considered dominant factors for the possible solute rejection mechanism. Rejection efficiency (% R) and permeate flowrate (Q₂) were simulated and compared with experimental results. It was found that simulated results were in excellent agreement with the experimental results. The maximum error obtained was within 10% for both % R and Q₂. This confirms the efficacy of FTCSK model in predicting arsenic (III) removal using NF membrane. The annualized cost per cubic metre of treated water was estimated as 3.32 $/m³. This further confirms the feasibility of using NF process in removing arsenic from contaminated water.

Winery Wastewater Treatment by Microalgae to Produce Low-Cost Biomass for Energy Production Purposes

Even though biofuel production from microalgae has become more and more attractive in recent years, it is limited especially by the high cost of microalgae cultivation. However, microalgae can be grown in wastewater in order to reduce their production cost and, at the same time, the polluting impact of wastewaters. Winery wastewaters, which are abundantly released from the wine making process, have a large pollution impact related to their high loads of total solids, chemical oxygen demand (COD) and polyphenol concentration. In this research work a co-culture of Chlorella vulgaris and Arthrospira platensis was used to treat three different winery wastewaters from different steps of the wine production process, in order to produce low-cost biomass intended for biofuel production. Growth of the co-culture and reduction of wastewater pollutant impact were followed by daily determinations of biomass concentration, COD and polyphenol content. The highest productivities of biomass (0.66 gDry Weight/L·day) and lipids (7.10 ± 0.22 gLipid/100 L·day) were obtained using 20% of second washing winery wastewater after 4 days of treatment. Moreover, COD and polyphenol content of the three different wastewaters were reduced by the co-culture by more than 92% and 50%, respectively. These results suggest that winery wastewaters can be used successfully for the growth of A. platensis and C. vulgaris co-culture in order to obtain inexpensive biomass for energy production purposes.

Combined Osmotic and Membrane Distillation for Concentration of Anthocyanin from Muscadine Pomace

Bioactive anthocyanins from aqueous extracts of muscadine grape pomace were concentrated using osmotic distillation (OD) and direct contact membrane distillation (DCMD) using polypropylene (PP) and poly(ethylene chlorotrifluoroethylene) (ECTFE) membranes. The driving force for OD is created by using a high concentration brine solution while the driving force for DCMD is generated by elevating the feed temperature relative to the permeate temperature. The brine concentration used was 4 M. The lowest fluxes were obtained for OD. Given the temperature sensitive nature of anthocyanins, the maximum temperature difference during DCMD was limited to 30 °C. The feed temperature was 40 °C and the permeate at 10 °C. Consequently, the maximum flux during DCMD was also limited. A combination of OD and DCMD was found to give the highest fluxes. High-performance liquid chromatography (HPLC) and HPLC-electrospray mass spectrometry were used to identify and quantify anthocyanins, cyanidin-3,5-O-diglucoside, delphinidin-3,5-O-diglucoside, petunidin-3,5-O-diglucoside, peonidin-3,5-O-diglucoside, and malvidin-3,5-O-diglucoside. The results obtained here suggest that, though water fluxes for DI water feed streams for PP and ECTFE membrane were similar, the fluxes obtained for the two membranes when using muscadine pomace extracts were different. Concentration factors of close to 3 was obtained for anthocyanins. Membranes also showed slightly different performance in the concentration process. Membrane surfaces were analyzed using scanning electron microscopy and Fourier-transformed infrared spectroscopy. The results suggest that adsorption of these anthocyanins on the membrane surface lead to performance differences. In an actual operation, selection of an appropriate membrane and regeneration of the membrane will be important for optimized performance. PRACTICAL APPLICATIONS: Anthocyanins are valuable therapeutic compounds, which are found in the solid residue left following fruit juice pressing. However, recovery and concentration of these therapeutic compounds remains challenging due to their stability. Here, a novel membrane-based unit operation has been investigated in order to concentrate the anthocyanins that have been extracted into aqueous solutions. The unit operation investigated here use mild processing conditions. Insights into the factors that need to be considered when optimizing of the unit operation for commercialization are discussed.

Anthocyanin Retention of Cranberry (Vaccinium macrocarpon) Juice Subjected to Different Nanofiltration Conditions

The aim of this work was to evaluate the retention of anthocyanin during a nanofiltration process of cranberry juice. Nanofiltration membranes, HC-50P DDS with an effective area of 0.36 m2 in a plate/frame nanofilter system, DDS Lab Module, were used for the experiments. Juice feed flow rate varied from 1.0 to 12.0 L min−1 at transmembrane pressures between 20 and 40 bar (2026 and 4052 kPa). Permeate flux reached a maximum value of 41.3 L h−1 m−2 at a pressure of 40 bar and a feed rate of 12 L min−1, showing a direct dependency on these two parameters. Retention coefficients of anthocyanin of 0.94 to 0.99 corresponding to percentage recovery between 93 and 99% were obtained. Total anthocyanin content increased to values between 237 and 287 mg L−1 from original concentration of 82 to 97 mg L−1 in feed solution. Total soluble solids were also retained on the nanofilter. Both anthocyanin retentate and permeate obtained by nanofiltration could be potential functional ingredients for the food and nutraceutical industry.

Membrane processing technology in the food industry: food processing, wastewater treatment, and effects on physical, microbiological, organoleptic, and nutritional properties of foods

Membrane processing technology (MPT) is increasingly used nowadays in a wide range of applications (demineralization, desalination, stabilization, separation, deacidification, reduction of microbial load, purification, etc.) in food industries. The most frequently applied techniques are electrodialysis (ED), reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF). Several membrane characteristics, such as pore size, flow properties, and the applied hydraulic pressure mainly determine membranes' potential uses. In this review paper the basic membrane techniques, their potential applications in a large number of fields and products towards the food industry, the main advantages and disadvantages of these methods, fouling phenomena as well as their effects on the organoleptic, qualitative, and nutritional value of foods are synoptically described. Some representative examples of traditional and modern membrane applications both in tabular and figural form are also provided.

Treatment of winery wastewater by physicochemical, biological and advanced processes: a review

Winery wastewater is a major waste stream resulting from numerous cleaning operations that occur during the production stages of wine. The resulting effluent contains various organic and inorganic contaminants and its environmental impact is notable, mainly due to its high organic/inorganic load, the large volumes produced and its seasonal variability. Several processes for the treatment of winery wastewater are currently available, but the development of alternative treatment methods is necessary in order to (i) maximize the efficiency and flexibility of the treatment process to meet the discharge requirements for winery effluents, and (ii) decrease both the environmental footprint, as well as the investment/operational costs of the process. This review, presents the state-of-the-art of the processes currently applied and/or tested for the treatment of winery wastewater, which were divided into five categories: i.e., physicochemical, biological, membrane filtration and separation, advanced oxidation processes, and combined biological and advanced oxidation processes. The advantages and disadvantages, as well as the main parameters/factors affecting the efficiency of winery wastewater treatment are discussed. Both bench- and pilot/industrial-scale processes have been considered for this review.