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Rotating disk membrane (RDM) module with ultrafiltration (UF) was an effective alternative method to treat alfalfa wastewater and realize protein recovery and agricultural irrigation water production. A scientific investigation has been conducted to comprehend the effect of operation conditions (feed flow rate, shear rate, transmembrane pressure (TMP), and temperature) on alfalfa wastewater treatment with RDM-UF by central composite response surface methodology (CCRSM). First, the filtration behaviors of three types of UF membranes (PES20, UH030P, and PES50) were studied to select the optimized membrane (UH030P). Then, the effects and interactions of four operation conditions were studied and fitting models were established, while data on pollution reduction and protein recovery, membrane fouling behavior, and energy cost evaluation were collected. Furthermore, the optimized operation conditions calculated by CCRSM were Q = 60 L h -1 , γ = 220 × 10 3  s -1 , TMP = 5.61 bar, and T = 25 °C. In addition, the concentration test was conducted with these parameters. This work may contribute to the potential application of RDM for membrane wastewater treatment. Graphical abstract Schematic diagram of UF process for alfalfa wastewater treatment and resource recovery.

Rotating Disk Membrane (RDM) module with ultrafiltration (UF) was an effective alternative method to treat alfalfa wastewater and realize protein recovery and agricultural irrigation water production. The effects of membrane and operational conditions (rotating speed, temperature and transmembrane pressure (TMP)) on filtration behavior were investigated using full recycling tests. High molecular weight cut off (MWCO) membrane, rotating speed, temperature and TMP improved flux behavior and productivity, but reduced separation performance. Moreover, the increases of membrane MWCO, temperature and TMP also led to elevation of irreversible fouling. Then series of concentration tests were conducted at various operational conditions and the filtration behavior was studied. High temperature could improve flux behavior and productivity significantly. Hermia’s blocking model was used to study fouling process, and identify the main fouling mechanism. These results from laboratory-scale tests provide a useful guide for protein recovery and agricultural irrigation water production in alfalfa wastewater treatment and provide a useful guide for UF process operation in industrial scale. [ABSTRACT FROM AUTHOR]

High shear stress is a promising new approach with high potential to assist membrane cleaning. In this study, the effect of shear stress on the permeability recovery of ultrafiltration (UF) membranes fouled by dairy wastewater was investigated. Water rinsing and chemical cleaning are two main cleaning methods. With respect to water rinsing, the effect of shear stress, temperature and cleaning time on cleaning efficiency were studied. Results revealed that shear stress could effectively remove casein micelles and whey protein layer on membrane surface. As for chemical cleaning, the effect of shear stress, temperature, the type of cleaning agent, concentration and cleaning time on cleaning efficiency were studied. Due to the effect of shear stress, the convection diffusivity was enhanced and foam cleaning agent was produced, thus can remove foulants on membrane surface or ones in internal greatly. Response surface methodology was utilized to explain the significance of various operation conditions and optimize the water rinsing and chemical cleaning process. After that, with the optimum results, two long time industrial cleaning processes were conducted and compared. In general, the high shear stress shows high potential for improving membrane cleaning operation and exerting a relevant influence on the overall process efficiency. [ABSTRACT FROM AUTHOR]

Ultrafiltration Dynamic Rotating Module (UF-DRDM) was an effective alternative method to concentrate leaf protein from alfalfa juice. The effects of operation parameters (membrane, rotating speed, temperature and TMP) on filtration behavior were investigated using full recycling tests and concentration tests. Large membrane molecular weight cut off (MWCO), rotating speed, temperature and TMP improved filtration behavior and productivity. Furthermore, high rotating speed produced high shear rate on membrane surface, enhancing separation performance and membrane cleaning efficiency. But, large MWCO, high temperature and high TMP caused terrible separation performance and high irreversible fouling. Then, series of concentration tests were studied. Large MWCO, high rotating speed, high temperature and great TMP could improve filtration behavior of concentration tests. Finally, concentration tests repeated five times were conducted at optimized operation conditions (2000 rpm, 6 bar, 55 °C and US100P) for checking efficiency, stability and sustainability as well its potential application value. These results from laboratory-scale tests show favorable prospects in the alfalfa juice concentration by UF-DRDM. [ABSTRACT FROM AUTHOR]

Micellar enhanced ultrafiltration is a promising technology for removing trace amounts of organic pollutants in wastewater, but membrane fouling caused by Gemini micelles is a significant problem restricting its industrial application. In this study, a flat sheet ultrafiltration membrane with four types of Gemini surfactant systems and various feed concentrations was used to treat phenol wastewater, while the flux behavior and fouling mechanism were investigated. The optimal permeate flux of phenol decreased in the sequence as follows: CG 12 > CG 16 > CG 12 − Brij35 > CG 16 − Brij35. In order to study the rate of membrane fouling, a developed liner regression method was utilized to help determine the threshold flux, as well the degree of concentration polarization and membrane fouling. Furthermore, limiting flux was investigated to avoid extensive cake layer formation. Threshold flux and limiting flux strongly depended on the feed concentration and the type of micelles. The threshold flux reduced gradually with feed concentration, due to the increased fouling rate and presence of irreversible fouling. Owing to the effect of charge density and hydrophobicity of micelles, CG 12 exhibited the highest threshold flux and limiting flux. Flux-TMP relation was divided into three regions for analyzing the corresponding changes of permeate flux, filtration resistance and conceptual particle deposition model. Besides, fouling mechanism of MEUF was discussed. This study provides a guideline for analyzing membrane fouling and seeking an optimum operation strategy for controlling fouling in membrane water treatment. [ABSTRACT FROM AUTHOR]

A systematic study has been conducted to have an insight into the separation efficiency of phenol with the help of Gemini surfactants and conventional nonionic surfactant in their single and mixed systems using micellar-enhanced ultrafiltration (MEUF). A flat sheet membrane with a total effective area of 0.08 m2and a molecular weight cut-off of 10 kDa, was selected in this investigate. The effects of feed component (surfactant concentration for single surfactant system and mixed ratio for mixed surfactant system) on solubilization and filtration efficiency were researched. Some related parameters were used to estimate the performance of various surfactant systems, such as distribution coefficient (D), the phenol concentration in micellar phase (Pm), the surfactant concentration in micellar phase (Sm), the micelle loading (Lm), and the equilibrium distribution constant (K). With the increase of feed surfactant concentration or the addition of nonionic surfactant, the degree of solubilization of phenol enhances, leading to the decrease of permeate concentration and the augment of retentate concentration. Consequently,D,Pm, andSmincreases. The addition of nonionic surfactant has positive effects to recounterbalance the interior structure and improve the micellar solubilization power for phenol. Both the single and mixed C12-2-16systems have higherD,Pm, andSmvalues than these of C12-2-12, due to the longer length alkyl chain and more optimized structure.LmandKare the significant indicators for evaluating the effectiveness of dissolving phenol. Irreversible fouling was almost eliminated with a series of cleaning solution in a short time. There results from the laboratory-scale experiments could be very useful in selection of the suitable surfactant systems for raising efficiency and could serve as valuable guide for MEUF in industrial application. [ABSTRACT FROM PUBLISHER]

Shear-enhanced ultrafiltration is considered as an important membrane technology that can contribute to pre-treat dairy wastewater and recycle valuable components such as milk proteins. However, to be efficient, it necessitates the establishment of proper methods for the assessment of membrane fouling. Four membrane blocking models proposed by Hermia were used to quantify and assess the membrane fouling of shear-enhanced filtration observed in dairy wastewater treatment. The experiments were performed with various shear rates, mean transmembrane pressure (TMP), temperature and membrane types. Good agreement between complete pore blocking model and experimental data was found, confirming the validity of the Hermia models for assessing the membrane fouling of shear-enhanced filtration system and that only some “sealing” of membrane pores occurs which is due to the high speed shearing effect. Furthermore, the increments of shear rate, TMP, and temperature can decrease the degree of “sealing” of membrane pores and improve filtration performance. In addition, a three-step membrane cleaning mode has achieved very satisfying results in subsequent membrane cleaning. This work confirms that, unlike traditional filtration mode (dead-end and cross flow filtration), high shear dynamic filtration possesses a low degree of membrane fouling and a higher membrane permeability recovery after cleaning. [ABSTRACT FROM AUTHOR]

Abstract: Comprehensive studies were carried on the micellar-enhanced ultrafiltration of phenol for the treatment of phenol wastewater with the help of cationic Gemini surfactant (CG) and Polyethersulfone (PES) flat sheet membranes of a molecular weight cut-off of 10kDa. The effects on the retention (phenol and surfactant), permeate flux and secondary resistance of various factors in the practical application of GMEUF were investigated including feed CG concentration, mole fraction of nonionic surfactant, electrolyte concentration and temperature, respectively. The results presented that the retention of phenol kept evidently increasing with the augment of the feed CG concentration and mole fraction of nonionic surfactant. On the contrary, electrolyte concentration and temperature had a negative influence on the phenol retention. Besides, the addition of feed CG concentration and mole fraction of nonionic surfactant led to the decrement of the permeate flux and enhancement of secondary resistance significantly. These results demonstrated that CG surfactant with exceptional structure had brightly application prospect for the treatment of phenol wastewater in micellar-enhanced ultrafiltration. [Copyright &y& Elsevier]

Abstract: Comprehensive studies were conducted on the phenol wastewater ultrafiltration (UF) with the help of various concentrations of cationic Gemini surfactant (N1-dodecyl-N1,N1,N2,N2-tetramethyl-N2-octylethane-1,2-diaminium bromide, CG), conventional cationic surfactant (dodecyl trimethyl ammonium bromide, DTAB), anionic surfactant (sodium dodecyl sulfate, SDS) and nonionic surfactant ((dodecyloxy)polyethoxyethanol, Brij35). A flat sheet module with polyethersulfone (PES) membrane was employed in this investigation. The effects of feed concentration (phenol and surfactant) on the retention of phenol and surfactant, permeate flux and membrane fouling by micelles were evaluated. The distribution coefficient (D), the loading of the micelles (L m ) and the equilibrium distribution constant (K) were also utilized to estimate the micellar-enhanced ultrafiltration ability for phenol. Scanning electron microscope (SEM), Fourier transform infrared spectrometer with attenuated total reflectance accessory (ATR-FTIR) and mercury porosimeter were applied to analyze membrane surface morphology, membrane material characteristics and membrane fouling for the original and fouled membranes. Based on the above analysis, the performance of the selected Gemini surfactant was proved superior in the following aspects: retention of phenol/surfactant (peak value is 95.8% for phenol retention), permeate flux and membrane fouling with respect to other conventional surfactants possessing equal alkyl chain length. These results demonstrated that CG surfactant with exceptional structure has favorable prospects in the treatment of phenol wastewater by the micellar-enhanced ultrafiltration. [Copyright &y& Elsevier]

An integrated peroxymonosulfate (PMS)-assisted electrolytic oxidation/coagulation (EO/EC) and ceramic ultrafiltration (UF) process was applied for antibiotic removal in surface water. Stable permeation was achieved in the case of surface water containing sulfamethazine (SMZ) (0–800 μg/L), and the optimum conditions appeared to be an electrical current (I) of 0.2 A, electrolysis time of 60 s, pH 7.5 (nearly 0.56 mg/L Fe2+, considering the pH value of the initial solution) and PMS dosage of 100 μM. During the PMS activation process, SMZ and organic matter were degraded by sulfate radicals (SO 4 ·-) or hydroxyl radicals (·OH), which was confirmed by electron paramagnetic resonance spectroscopy (EPR), and scanning electron microscopy (SEM) and X-ray energy-dispersive spectroscopy (EDS) indicated that the ceramic UF membrane could effectively retain coagulants containing C, S and Fe. Moreover, PMS-assisted electro-oxidation/coagulation pretreatment could generate larger coagulated aggregates (206–275 μm) regardless of the humic acid (HA) (0–20 mg/L) and kaoline particle (0–100 mg/L) content of surface water, thus significantly decreasing the fouling rate. In particular, this process could achieve stable permeation and retain better filtration performance in the case of high antibiotic and organic matter contents in real surface water treatment. This electrically powered process could be used to treat micro-polluted water in remote regions. Image 1 • PMS-assisted electro-oxidation/coagulation combined with a ceramic UF was applied for micro-polluted surface water treatment. • EO/EC could offer a good effluent for sulfamethazine degradation. • Humic-like substance with larger MWs could cause membrane fouling. • PMS-assisted EO/EC pretreatment could enhance ceramic UF membrane fouling control. [ABSTRACT FROM AUTHOR]