Control of Membrane Biofouling in MBR for Wastewater Treatment by Quorum Quenching Bacteria, Pseudomonas sp. 1A1

Abstract

Recently, interspecies quorum quenching by bacterial cell has been elaborated and proved to be more efficient and economic than enzymatic quorum quenching for the biofouling control in membrane bioreactor (MBR) for wastewater treatment. However, since the activated sludge of MBRs have diverse characteristics according to the source of wastewater, it is necessary to secure diverse species of quorum quenching bacteria to apply them widely and efficiently to MBRs with diverse feed sources. The purpose of this study is to isolate and characterize quorum quenching bacteria from a lab-scale MBR and to find optimum environment for each quorum quenching bacterium. A quorum quenching Pseudomonas sp. 1A1 was chosen among isolates as a representative bacterium which produces a quorum quenching enzyme extracellularly. The AHL degradation efficiency of Pseudomonas sp.1A1 was compared with that of Rhodococcus sp. BH4 which has been reported to produce a quorum quenching enzyme intracellularly. Both bacteria were encapsulated in microporous MF (pore size, 0.4 μm) and UF(pore size, 0.03μm) hollow fiber membranes, respectively. The microbial encapsulated vessel was submerged into a continuous MBR together with a filtration membrane to test its efficiency in the biofouling inhibition. By monitoring the change in transmembrane pressure (TMP), the Pseudomonas sp. 1A1 producing an extracellular quorum quenching enzyme was confirmed to be as efficient in biofouling control as the Rhodococcus sp. BH4 producing an intracellular quorum quenching enzyme. However, the quorum quenching efficiency of Pseudomonas sp 1A1 was different dependent on the porosity of vessel (i.e., MF or UF hollow fiber) in which this bacterium was entrapped. It could be explained by the mass transfer of signal molecules and enzymes through the pores of vessel.