Harvesting of Scenedesmus acuminatus using ultrafiltration membranes operated in alternative feed directions

Numerical and experimental investigation of ultrasound effects on filtration process in wire-wrapped filter tube

Refinery filtration processes often face challenges related to rapidly increasing permeate pressure differentials and the consequent need for frequent back-flushing. This study investigates the impact of high-intensity immersed sonotrode ultrasound device on flow patterns to address these issues, both numerically and experimentally. Numerical simulations reveal that ultrasound promotes axial circular mixing of the bulk fluid, increasing average flow velocities around the filter tube from 5.11 × 10-5 m/s to 8.76 × 10-3-6.09 × 10-2 m/s, thereby facilitating cleansing of filter tube surfaces. Additionally, high-frequency pressure fluctuations contribute to enhancing the filtration process during positive pressure phases, while robust online back-flushing effects are generated during negative pressure phases. Although the wire-wrapped filter tube attenuates ultrasound energy as it penetrates the tube gaps, ultrasound still induces turbulent mixing inside and outside the filter tubes, aiding in the removal of impurities from the gaps. The utilization of ultrasound is demonstrated to not inflict harm on upstream and downstream facilities. Experimental results demonstrate that ultrasound-assisted filtration with 600 W and 1000 W power inputs reduces filtration pressure differences by 18 % and 73 %, respectively, affirming ultrasound's effectiveness in mitigating and preventing blockages, highlighting its significance for industrial applicability.

Membrane-Based Harvesting Processes for Microalgae and Their Valuable-Related Molecules: A Review

The interest in microalgae production deals with its role as the third generation of feedstock to recover renewable energy. Today, there is a need to analyze the ultimate research and advances in recovering the microalgae biomass from the culture medium. Therefore, this review brings the current research developments (over the last three years) in the field of harvesting microalgae using membrane-based technologies (including microfiltration, ultrafiltration and forward osmosis). Initially, the principles of membrane technologies are given to outline the main parameters influencing their operation. The main strategies adopted by the research community for the harvesting of microalgae using membranes are subsequently addressed, paying particular attention to the novel achievements made for improving filtration performance and alleviating fouling. Moreover, this contribution also gives an overview of the advantages of applying membrane technologies for the efficient extraction of the high added-value compounds in microalgae cells, such as lipids, proteins and carbohydrates, which together with the production of renewable biofuels could boost the development of more sustainable and cost-effective microalgae biorefineries.

Improved Nylon 6,6 Nanofiber Membrane in A Tilted Panel Filtration System for Fouling Control in Microalgae Harvesting

The competitiveness of algae as biofuel feedstock leads to the growth of membrane filtration as one of promising technologies for algae harvesting. Nanofiber membrane (NFM) was found to be efficient for microalgae harvesting via membrane filtration, but it is highly limited by its weak mechanical strength. The main objective of this study is to enhance the applicability of nylon 6,6 NFM for microalgae filtration by optimizing the operational parameters and applying solvent vapor treatment to improve its mechanical strength. The relaxation period and filtration cycle could be optimized to improve the hydraulic performance. For a cycle of 5 min., relaxation period of ≤2 min shows the highest steady-state permeability of 365 ± 14.14 L m⁻² h⁻¹ bar⁻¹, while for 10 min cycle, 3 min. of relaxation period was found optimum that yields permeability of 402 ± 34.47 L m⁻² h⁻¹ bar⁻¹. The treated nylon 6,6 NFM was also used to study the effect of aeration rate. It is confirmed that the aeration rate enhances the steady-state performance for both intermittent and continuous mode of aeration. Remarkably, intermittent aeration shows 7% better permeability than the full aeration for all tested condition, which is beneficial for reducing the total energy consumption.