Abstract
Bacterial quorum quenching (QQ) media with various structures (e.g., bead, cylinder, hollow cylinder, and sheet), which impart biofouling mitigation in membrane bioreactors (MBRs), have been reported. However, there has been a continuous demand for membranes with QQ capability. Thus, herein, we report a novel double-layered membrane comprising an outer layer containing a QQ bacterium (BH4 strain) on the polysulfone hollow fiber membrane. The double-layered composite membrane significantly inhibits biofilm formation (i.e., the biofilm density decreases by ~58%), biopolymer accumulation (e.g., polysaccharide), and signal molecule concentration (which decreases by ~38%) on the membrane surface. The transmembrane pressure buildup to 50 kPa of the BH4-embedded membrane (17.8 h ± 1.1) is delayed by more than thrice (p < 0.05) of the control with no BH4 in the membrane’s outer layer (5.5 h ± 0.8). This finding provides new insight into fabricating antibiofouling membranes with a self-regulating property against biofilm growth.
Highlights
Over the past 30 years, membrane bioreactor (MBR) markets have rapidly grown with tremendous increases in the number and capacity of operating membrane bioreactors (MBRs) worldwide [1]
The cross-section of the BH4-free layered membrane is shown in black, and empty pores exist in the hydrogel layer as observed by the CLSM and scanning electron microscope (SEM) images, respectively (Figure 3b)
The result demonstrates that live BH4 strains were successfully immobilized into the outer layer of the hydrogel–polysulfone composite membrane
Summary
Over the past 30 years, membrane bioreactor (MBR) markets have rapidly grown with tremendous increases in the number and capacity of operating MBRs worldwide [1]. The biofouling caused by microbial adhesion and growth on the membrane surface limits the proliferation of MBRs, which must be overcome [2]. Several approaches have been performed to minimize the biofouling phenomena during MBR operations. Some of the most popular techniques used so far are intensive aeration and periodic maintenance cleaning (i.e., chemically enhanced cleaning) [3,4]. Approximately 50% of the total energy required for MBRs is consumed by membrane aeration [5]. Maintenance cleaning with active chlorine helped to delay membrane fouling, biofouling seemed to inevitably occur in MBRs [4], possibly due to the biofilm formation of chlorineresistant bacterial species [6,7]. Neither physical nor chemical methodologies have been found to be sufficient in controlling MBR biofouling. It was assumed that biological methods, which can regulate microbial interactions, may open a new horizon in biofouling mitigation as reported in microbial signaling pathways [8]
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