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1. Monitoring and Characterization of Milk Fouling on Stainless Steel Using a High-Pressure High-Temperature Quartz Crystal Microbalance with Dissipation

   https://doi.org/10.1021/acs.langmuir.2c00419  

   Huellemeier, Holly A. ; Eren, Necla M. ; Payne, Taylor D. ; Schultz, Zachary D. ; Heldman, Dennis R. ( October 2022 , Langmuir)

   Fouling at interfaces deteriorates the efficiency and hygiene of processes within numerous industrial sectors, including the oil and gas, biomedical device, and food industries. In the food industry, the fouling of a complex food matrix to a heated stainless steel surface reduces production efficiency by increasing heating resistance, pumping requirements, and the frequency of cleaning operations. In this work, quartz crystal microbalance with dissipation (QCM-D) was used to study the interface formed by the fouling of milk on a stainless steel surface at different flow rates and protein concentrations at high temperatures (135 °C). Subsequently, the QCM-D response was recorded during the cleaning of the foulant. Two phases of fouling were identified. During phase-1, the fouling rate was dependent on the flow rate, while the fouling rate during phase-2 was dependent on the flow rate and protein concentration. During cleaning, foulants deposited at the higher flow rate swelled more than those deposited at the lower flow rate. The composition of the fouling deposits consisted of both protein and mineral species. Two crystalline phases of calcium phosphate, β-tricalcium phosphate and hydroxyapatite, were identified at both flow rates. Stratification in topography was observed across the surface of the QCM-D sensor with a brittle and cracked structure for deposits formed at 0.2 mL/min and a smooth and close-packed structure for deposits formed at 0.1 mL/min. These stratifications in the composition and topography were correlated to differences in the reaction time and flow dynamics at different flow rates. This high-temperature application of QCM-D to complex food systems illuminates the initial interaction between proteins and minerals and a stainless steel surface, which might otherwise be undetectable in low-temperature applications of QCM-D or at larger bench and industrial scales. The methods and results presented here have implications for optimizing processing scenarios that limit fouling formation while also enhancing removal during cleaning. 

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2. Process- and Product-Related Foulants in Virus Filtration

   https://doi.org/10.3390/bioengineering9040155  

   Isu, Solomon ; Qian, Xianghong ; Zydney, Andrew L. ; Wickramasinghe, S. Ranil ( April 2022 , Bioengineering)

   Regulatory authorities place stringent guidelines on the removal of contaminants during the manufacture of biopharmaceutical products. Monoclonal antibodies, Fc-fusion proteins, and other mammalian cell-derived biotherapeutics are heterogeneous molecules that are validated based on the production process and not on molecular homogeneity. Validation of clearance of potential contamination by viruses is a major challenge during the downstream purification of these therapeutics. Virus filtration is a single-use, size-based separation process in which the contaminating virus particles are retained while the therapeutic molecules pass through the membrane pores. Virus filtration is routinely used as part of the overall virus clearance strategy. Compromised performance of virus filters due to membrane fouling, low throughput and reduced viral clearance, is of considerable industrial significance and is frequently a major challenge. This review shows how components generated during cell culture, contaminants, and product variants can affect virus filtration of mammalian cell-derived biologics. Cell culture-derived foulants include host cell proteins, proteases, and endotoxins. We also provide mitigation measures for each potential foulant. 

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3. Dynamic monitoring and proactive fouling management in a pilot scale gas-sparged anaerobic membrane bioreactor

   https://doi.org/10.1039/d0ew00608d  

   Lim, Kahao ; Evans, Patrick J. ; Utter, Joshua ; Malki, Mo ; Parameswaran, Prathap ( October 2020 , Environmental Science: Water Research & Technology)

   null (Ed.)

   This study examines membrane performance data of a pilot-scale gas-sparged anaerobic membrane bioreactor (AnMBR) over its 472 day operational period and characterizes the foulant cake constituents through a membrane autopsy. The average permeability of 336 ± 81 LMH per bar during the first 40 days of operation decreased by 92% by the study's conclusion. While maintenance cleaning was effective initially, its ability to restore permeability decreased with time. Wasting bioreactor solids appeared to be effective in restoring permeability where chemical cleans were unable to. The restoration mechanism appears to be a decrease in colloidal material, measured by semi-soluble chemical oxygen demand (ssCOD), rather than bioreactor total solids concentration. This is further supported through the use of fluorometry during AnMBR operation, which showed an increase in tyrosine-like compounds during heavy fouling conditions, suggesting that proteinaceous materials have a large influence on fouling. This was corroborated during membrane autopsy using Fourier transform infrared spectroscopy (FTIR). FTIR, scanning electron microscopy with energy dispersive X-ray spectroscopy, and transmission electron microscopy were used to characterize inorganic scalants and predominantly found phosphate salts and calcium sulfate. Fundamentally characterizing foulants and introducing novel and dynamic monitoring parameters during AnMBR operation such as ssCOD and fluorometry can enable more targeted fouling control. 

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4. Nanoparticle filtration through microporous ECTFE membrane in an alcoholic solution

   https://doi.org/https://doi.org/10.1016/j.seppur.2018.08.022  

   Na Yao, Boris Khusid ( October 2018 , Separation and purification technology)

   Organic solvent filtration is an important industrial process. It is widely used in pharmaceutical manufacturing, chemical processing industry, semiconductor industry, auto assembly etc. Most of the particle filtration studies reported in open literature dealt with aqueous suspension medium. The current work has initiated a study of cross-flow solvent filtration behavior of microporous ethylene chlorotrifluoroethylene (ECTFE) membranes using 12 nm silica nanoparticles suspended in an aqueous solution containing 25% ethanol. In the constant pressure mode of operation of cross-flow microfiltration (MF), permeate samples were collected at different time intervals. The permeate particle size distribution (PSD) results for different experiments were identical. Particle agglomerates having less than 100 nm size can pass through the membrane; some fouling was observed. The governing fouling mechanisms for tests operated using 3.8×10−3 kg/m3 (3.8 ppm) at 6.9×103 Pag and 1.4×104 Pag were pore blocking. For tests conducted using 3.8×10−3 kg/m3 (3.8 ppm) at 27.6×103 Pag (4 psig) and 1.9×10−3 kg/m3 (1.9 ppm) at 6.9×103, 13.8×103 and 27.6×103 Pag (1, 2 and 4 psig), the mechanism was membrane resistance control. Less particles got embedded in membrane pores in experiments operated using suspensions with lower or higher particle concentrations with a higher transmembrane pressure. This is in good agreement with the values of the shear rate in the pore flow and scanning electron microscope images of the membrane after MF. In the dead-end mode of operation of solvent filtration using methanol, ethanol and 2-propanol, the permeate flux behavior follows Jmethanol > Jethanol > J2-propanol at all testing pressures. The values of permeance (kg/m2-s-Pa) determined from the slope of the linear plot of filtration flux vs. the applied pressure difference across the membrane, were 3.9×10−4, 2.3×10−4 and 3.0×10−5 for methanol, ethanol and 2-propanol, respectively. Further exploration was made on solvent sorption results reported earlier. The critical temperature of selected solvents shows a better correlation with solvent sorption rather than the solubility parameter. 

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5. Mechanical Vibration for the Control of Membrane Fouling in Direct Contact Membrane Distillation

   https://doi.org/10.3390/sym11020126  

   Huang, Frank ; Medin, Carolyn ; Arning, Allie ( February 2019 , Symmetry)

   One of the biggest challenges for direct contact membrane distillation (DCMD) in treating wastewater from flue gas desulfurization (FGD) is the rapid deterioration of membrane performance resulting from precipitate fouling. Chemical pretreatment, such as lime-soda ash softening, has been used to mitigate the issue, however, with significant operating costs. In this study, mechanical vibration of 42.5 Hz was applied to lab-scale DCMD systems to determine its effectiveness of fouling control for simulated FGD water. Liquid entry pressure and mass transfer limit of the fabricated hollow fiber membranes were determined and used as the operational constraints in the fouling experiments so that the observed membrane performance was influenced solely by precipitate fouling. Minimal improvement of water flux was observed when applying vibration after significant (~16%) water-flux decline. Initiating vibration at the onset of the experiments prior to the exposure of foulants, however, was promising for the reduction of membrane fouling. The water-flux decline rate was reduced by about 50% when compared to the rate observed without vibration. Increasing the module packing density from 16% to 50% resulted in a similar rate of water-flux decline, indicating that the fouling propensity was not increased with packing density in the presence of vibration. 

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