Combined Effect of Activated Carbon Particles and Non-Adsorptive Spherical Beads as Fluidized Media on Fouling, Organic Removal and Microbial Communities in Anaerobic Membrane Bioreactor.

Daeeun Kwon,Theo Y C Lam,Jeonghwan Kim,Giin-Yu Amy Tan,Minseok Kim,Po-Heng Lee

doi:10.3390/membranes11050365

Daeeun Kwon, Theo Y C Lam + Show 4 more

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https://doi.org/10.3390/membranes11050365

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Abstract

The combined effect of acrylonitrile butadiene styrene (ABS) spherical beads and granular activated carbon (GAC) particles as fluidized media on the performance of anaerobic fluidized bed membrane bioreactor (AFMBR) was investigated. GAC particles and ABS beads were fluidized together in a single AFMBR to investigate membrane fouling and organic removal efficiency as well as energy consumption. The density difference between these two similarly sized media caused the stratified bed layer where ABS beads are fluidized above the GAC along the membrane. Membrane relaxation was effective to reduce the fouling and trans-membrane pressure (TMP) below 0.25 bar could be achieved at 6 h of hydraulic retention time (HRT). More than 90% of soluble chemical oxygen demand (SCOD) was removed after 80 d operation. Biogas consisting of 65% of methane was produced by AFMBR, suggesting that combined use of GAC and ABS beads did not have any adverse effect on methane production during the operational period. Scanning Electron Microscope (SEM) examinations showed the adherence of microbes to both media. However, 16S rRNA results revealed that fewer microbes attached to ABS beads than GAC. There were also compositional differences between the ABS and GAC microbial communities. The abundance of the syntrophs and exoelectrogens population on ABS beads was relatively low compared to that of GAC. Our result implied that syntrophic synergy and possible occurrence of direct interspecies electron transfer (DIET) might be facilitated in AFMBR by GAC, while traditional methanogenic pathways were dominant in ABS beads. The electrical energy required was 0.02 kWh/m3, and it was only about 13% of that produced by AFMBR.

Highlights

Media fluidization is one of the key aspects to determine the performance of anaerobic fluidized bed membrane bioreactor (AFMBR) in the treatment of low strength wastewater such as domestic sewage [1,2,3]
granular activated carbon (GAC) particles that are ground into a smaller size can accelerate the membrane fouling because the particles should be deposited on membrane surface or even within membrane pores due to the formation of very dense cake layers [18,19,20,21]
A direct comparison is difficult, our observation suggests that more biomass can be grown on the GAC particles, probably due to the higher surface area provided, thereby lowering the concentration of extracellular polymeric substance (EPS) in bulk suspension than when only the plastic bead is used

Summary

Introduction

Media fluidization is one of the key aspects to determine the performance of AFMBR in the treatment of low strength wastewater such as domestic sewage [1,2,3]. While GAC particles can be an excellent tool as fluidizing media [15,16,17], the particles can be broken very by frequent collisions due to their weak rigidity during long-term reactor operation. This phenomenon should be more pronounced with larger media size, a higher recirculation rate or mixing intensity through the AFMBR reactor [18]. GAC particles that are ground into a smaller size can accelerate the membrane fouling because the particles should be deposited on membrane surface or even within membrane pores due to the formation of very dense cake layers [18,19,20,21]. Higher specific gravity of the media such as GAC than the bulk wastewater present in the reactor, which is often higher than 2.0, requires more energy needed for the media fluidization than smaller ones

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