Gravity-driven membrane system for secondary wastewater effluent treatment: Filtration performance and fouling characterization

Abstract

Gravity-driven membrane (GDM) filtration is one of the promising membrane bioreactor (MBR) configurations. It operates at an ultra-low pressure by gravity, requiring a minimal energy. The objective of this study was to understand the performance of GDM filtration system and characterize the biofouling formation on a flat sheet membrane. This submerged GDM reactor was operated at constant gravitational pressure in treating of two different concentrations of secondary wastewater effluent. Morphology of biofilm layer was acquired by an in-situ and on-line optical coherence tomography (OCT) scanning in a fixed position at regular intervals. The thickness and roughness calculated from OCT images were related to the variation of flux, fouling resistance and permeate quality. At the end of experiment, fouling was quantified by total organic carbon (TOC) and adenosine tri-phosphate (ATP) method. Confocal laser scanning microscopy (CLSM) was also applied for biofouling morphology observation. The biofouling formed on membrane surface was mostly removed by physical cleaning 2 confirmed by contact angle measurement before and after cleaning. This demonstrated that fouling on the membrane under ultra-low pressure operation was highly reversible. The superiority and sustainability of GDM in both flux maintaining and long-term operation with production of high quality effluent was demonstrated.

Evaluation of membrane fouling mitigation strategies in an algal membrane photobioreactor (AMPBR) treating secondary wastewater effluent

“…A similar trend was observed for the biomass roughness, with the highest value for APMBRRLX (0.58), followed by the APMBRBW (0.43) and APMPBRCT (0.27). The behavior of the biomass formed with no control strategy (APMPBRCT) is in agreement with results reported in previous studies on membrane performance without applying physical cleaning showing a decrease in roughness and a tendency towards more compact and dense morphology at early stages (Pathak et al, 2018;Wang et al, 2017). A different trend was found for the APMBRBW and APMBRRLX, showing a constant and higher value in relative roughness during the whole period of observation.…”

Biocarriers facilitated gravity-driven membrane (GDM) reactor for wastewater reclamation: Effect of intermittent aeration cycle

“…Previous studies have shown that the GDM systems could potentially treat greywater/municipal wastewater, but with a relatively low permeability (30-70 L/m 2 h/bar), which is dependent on the wastewater quality such as organic concentrations (Ding et al 2016, Ding et al 2017a, Ding et al 2017b, Jabornig and Podmirseg 2015, Wang et al 2017). In addition, the GDM systems could not fully remove dissolved organic substances, such as humic substances, building blocks, and low molecular weight substances (Ding et al 2018a, Wu et al 2019.…”

Fouling Monitoring in Membrane Filtration Systems

“…The possibility of capturing a fouling morphology change has been exploited by several authors. Some tests were focused on evaluating the change of morphologies linked to the change of the feed [38,39]. Experiments are often performed in membrane flowcells and compared to a control.…”