Computational fluid dynamics modeling and experimental study of continuous and pulsatile flow in flat sheet microfiltration membranes

Research progress in external field intensification of forward osmosis process for water treatment: A critical review

Forward osmosis (FO) is an emerging permeation-driven membrane technology that manifests advantages of low energy consumption, low operating pressure, and uncomplicated engineering compared to conventional membrane processes. The key issues that need to be addressed in FO are membrane fouling, concentration polarization (CP) and reverse solute diffusion (RSD). They can lead to problems about loss of draw solutes and reduced membrane lifetime, which not only affect the water treatment effectiveness of FO membranes, but also increase the economic cost. Current research has focused on FO membrane preparation and modification strategies, as well as on the selection of draw solutions. Unfortunately, these intrinsic solutions had limited success in unraveling these phenomena. In this paper, we provide a brief review of the current state of research on existing external field-assisted FO systems (including electric-, pressure-, magnetic-, ultrasonic-, light- and flow-assisted FO system), analyze their mitigation mechanisms for the above key problems, and explore potential research directions to aid in the further development of FO systems. This review aims to reveal the feasibility of the development of external field-assisted FO technology to achieve a more economical and efficient FO treatment process.

Insights on fouling development and characteristics during different fouling stages between a novel vibrating MBR and an air-sparging MBR for domestic wastewater treatment

Membrane fouling remains a major hindrance to a prevalent application of membrane bioreactor (MBR) for wastewater treatment. Vibrating membrane technology has recently attracted increasing attention in energy-efficient fouling control in MBR compared to air sparging. However, little is known about its fundamental fouling control mechanism and whether the vibrating MBR (VMBR) is a highly effective strategy to control fouling constitutions and fouling sources compared to the conventional air-sparging MBR (ASMBR). This study operated two parallel MBRs with vibrating or air-sparging membrane modules for long-term (215 d) real domestic wastewater treatment. Effects of air sparging and vibration rates on fouling control, fouling development and fouling sources across three fouling stages were comprehensively evaluated. Results showed that the VMBR achieved 70% lower fouling rates compared to the ASMBR due to a remarkable retardation in each fouling stage by membrane vibration. The VMBR significantly reduced over 62.7% of colloid_CL and SMP_CL within the cake layer (CL) to simultaneously alleviate the reversible and irreversible fouling compared to the ASMBR. The comparatively lower dissolved organic matter (DOM) and biopolymer contents in the cake layer of the VMBR resulted in a slower TMP rise. The main DOMs in the foulants of both MBRs were found in the following order: aromatic protein > soluble microbial by-products > other organics. EPS_ML from mixed liquor (ML) contributed more DOMs to form membrane foulant than the SMP_ML in both MBRs. Aromatic proteins and soluble microbial products in the EPS_ML were markedly reduced in the VMBR but increased in the ASMBR in high-shear phase, demonstrating higher effectiveness in fouling control by membrane vibration. This study provided insights into understanding fouling control, fouling development characteristics and fouling mechanisms between the VMBR and ASMBR, which might guide the researchers and engineers to apply novel vibrating MBRs to better control membrane fouling for holistic wastewater treatment in full scale.