Orange juice ultrafiltration: characterisation of deposit layers and membrane surfaces after fouling and cleaning

Monitoring Membrane Fouling Using Fluid Dynamic Gauging: Influence of Feed Characteristics and Operating Conditions

Recent studies on membrane fouling have made considerable progress in reducing its adverse effects. However, a lack of comprehensive studies focusing on the underlying fouling mechanisms remains. This work aims to address a part of this gap by investigating the influence of feed suspension chemistry and operating conditions on the fouling characteristics of microcrystalline cellulose. Fluid dynamic gauging (FDG) was employed to monitor the properties of fouling layers under varied conditions. FDG results revealed that the cohesive strength of fouling layers increased in the direction towards the membrane, which can be associated with the higher compressive pressures exerted on foulants deposited near the surface. At lower pHs and higher ionic strengths, reduced electrostatic repulsions between particles likely resulted in particle agglomeration, leading to the formation of thicker cakes. In addition, thicker cake layers were also observed at higher feed concentrations, higher operating transmembrane pressures, and longer filtration times. The cross-flow velocity influenced the resilience of fouling layers significantly, resulting in thinner yet stronger cake layers in the transition and turbulent flow regimes. These findings regarding the influence of feed characteristics and operating conditions on the fouling behavior can be beneficial in developing effective antifouling strategies in membrane separation processes.

Long-Term Performance of Ultrafiltration Membranes: Corrosion Fouling Aspect

The past decade has seen a rise in the importance of the ultrafiltration (UF) technique in the separation of various complex solutions. However, the fouling phenomenon is the main limitation to faster process development. To the best of the authors' knowledge, the present paper is the first to aim to identify the role of corrosion fouling in long-term UF. For this purpose, polyvinylidene fluoride (PVDF) and polyethersulfone (PES) membranes were used. The investigations were carried out with the use of both pilot-scale and laboratory-scale units. Results obtained in the present study have clearly demonstrated that the oil concentration has a significant impact on the process performance. Indeed, it has been noted that a reduction in oil concentration from 160 to 100 mg/L resulted in an increase in the PVDF membrane flux from 57 to 77 L/m²h. In addition, it has been shown that the feed temperature has a significant influence on the UF performance. Importantly, it has been shown that corrosion fouling is of vital importance in UF membranes. Indeed, corrosion products such as iron oxides contaminated the membrane surface leading to an irreversible decrease in the UF process performance. In addition, it has been found that repeating the chemical cleaning of the membrane units significantly reduced the intensity of the fouling phenomenon. However, the complete elimination of its effects was not achieved. Therefore, it has been indicated that cleaning agents recommended by membrane manufacturers do not remove corrosion products deposited on the membrane surface. Undoubtedly, the obtained results can be used in the design of UF units leading to the extension of membrane installation lifetime.