A Rotary Spacer System for Energy-Efficient Membrane Fouling Control in Oil/Water Emulsion Filtration.

Membrane fouling deteriorates membrane filtration performances. Hence, mitigating membrane fouling is the key factor in sustaining the membrane process, particularly when treating fouling-prone feed, such as oil/water emulsions. The use of spacers has been expanded in the membrane module system, including for membrane fouling control. This study proposed a rotating spacer system to ameliorate membrane fouling issues when treating an oil/water emulsion. The system's effectiveness was assessed by investigating the effect of rotating speed and membrane-to-disk gap on the hydraulic performance and the energy input and through computational fluid dynamics (CFD) simulation. The results showed that the newly developed rotary spacer system was effective and energy-efficient for fouling control. The CFD simulation results proved that the spacer rotations induced secondary flow near the membrane surface and imposed shear rate and lift force to exert fouling control. Increasing the rotation speed to an average linear velocity of 0.44 m/s increased the permeability from 126.8 ± 2.1 to 175.5 ± 2.7 Lm-2h-1bar-1. The system showed better performance at a lower spacer-to-membrane gap, in which increasing the gap from 0.5 to 2.0 cm lowered the permeability from 175.5 ± 2.7 to 126.7 ± 2.0 Lm-2h-1bar-1. Interestingly, the rotary system showed a low energy input of 1.08 to 4.08 × 10-3 kWhm-3 permeate when run at linear velocities of 0.27 to 0.44 ms-1. Overall, the findings suggest the competitiveness of the rotary spacer system as a method for membrane fouling control.

Studies on a new stainless steel mesh dynamic membrane for wastewater treatment.

In this study an innovative dynamic membrane bioreactor (DMBR) was implemented from a stainless-steel mesh filter, which was used as a support material, and activated sludge used as an adsorption and filtration interface containing particulate organics. This work indicated that DMBR can achieve rapid solid-liquid pollutants separation. The activated sludge in the aeration tank quickly formed a thin dynamic membrane layer on the filter. The layer was automatically regenerated as the sludge traveled through the reactor. The experimental results for the new DMBR showed good biodegradability in sewage treatment when the activated sludge concentrations ranged between 3000 and 7000 mg/L. Excellent adsorption and filtration performance were also achieved. This dynamic membrane layer significantly improved the effluent quality. The average removal rates were 92.2% and 91.5% for Chemical Oxygen Demand (COD) and Total Phosphorus (TP), respectively. The sewage treatment index was better than the current standard activated sludge process.

Microalgae fractionation using steam explosion, dynamic and tangential cross-flow membrane filtration.

In this study, the microalga Nannochloropsis gaditana was subjected to acid catalysed steam explosion treatment and the resulting exploded material was subsequently fractionated to separate the different fractions (lipids, sugars and solids). Conventional and vibrational membrane setups were used with several polymeric commercial membranes. Two different routes were followed: 1) filtration+lipid solvent extraction and 2) lipid solvent extraction+filtration. Route 1 revealed to be much better since the used membrane for filtration was able to permeate the sugar aqueous phase and retained the fraction containing lipids; after this, an extraction required a much lower amount of solvent and a better recovering yield. Filtration allowed complete lipid rejection. Dynamic filtration improved permeability compared to the tangential cross-flow filtration. Best membrane performance was achieved using a 5000Da membrane with the dynamic system, obtaining a permeability of 6L/h/m2/bar.

Vibrating membrane filtration as improved technology for microalgae dewatering.

The effect of shear-enhanced filtration by vibratory process in microalgae dewatering is presented in this paper. The aim of this research was to investigate the technical performance and improvement of vibrating membrane filtration compared with conventional tangential cross-flow filtration in microalgae concentration. An industrial-scale available commercial set-up was used. Several membrane materials as polyethersulfone, polyacrylonitrile, etc., and mean pore sizes (from 7000Da to 0.2µm) were tested and compared in both filtration set-ups. Experiments were carried-out with Nannochloropsis gaditana and Phaeodactylum tricornutum microalgae. It has been demonstrated that, even if the choice of the membrane depends on its cut-off, its material and the type of microalgae filtrated, dynamic filtration is always the best technology over a conventional one. If with conventional filtration permeability values were in the vicinity of 10L/h/m(2)/bar in steady state phase, with dynamic filtration these values increased to 30L/h/m(2)/bar or more.