Application of cell entrapping beads for Quorum Quenching technique in submerged membrane bioreactor

Abstract

Biofouling is unwanted accumulation of microbial population on the membrane surface which limits the use of membrane bioreactor (MBR) in the market. Disruption of the biofilm formation by Quorum Quenching (QQ) by using cell entrapping beads (CEBs) is an approach with great potential to control membrane biofouling as the beads used provide not only mitigating effect on biofilm formation, by interfering Quorum Sensing, but also physical forces to detach the biofilm from the membrane surface. This research aimed to develop QQ-CEB with locally available chemicals in Pakistan and its application to evaluate the QQ effect together with physical and chemical cleaning. Various CEBs were made of different mixtures of sodium alginate and polyvinyl alcohol (PVA) and their quality was tested considering physical and biological aspects. Rhodococcus sp. BH4 and Pseudomonas putida were entrapped in the CEBs and then introduced in MBR as one of biofouling control methods along with standard backwash and chemical backwash. The CEBs made of specific concentration of PVA were proven to be more durable and helpful in mitigating biofouling as compared to that of sodium alginate. An MBR operated with PVA-alginate QQ CEBs together with chemical backwash showed the best performance without deterioration of effluent quality.

Effect of Aeration Intensity on Performance of Lab-Scale Quorum-Quenching Membrane Bioreactor

“…To observe the pure QQ effect that is separated from the physical cleaning effect of QQ-CIBs, comparative operations (vacant bead condition) were added. To observe the effect of aeration intensity on MBR performance, three different air flow rates were selected to be low, medium, and high, i.e., 1.5 L/min, 2.5 L/min, and 3.5 L/min with reference to previous research [ 22 , 34 ]. These air flow rates are equivalent to 3.1, 5.2, and 7.3 m 3 /m 2 /h as specific aeration demand (SAD m , air flow rate per unit surface area of membrane) and estimated to provide the velocity gradient G value of 92, 119, and 140/s, respectively, using the formulas of Mueler et al [ 36 ] and Psoch and Schiewer [ 37 ].…”

“…The design of this setup is shown in Figure 1. The setup consists of a concentrated feed bucket which is placed in a refrigerator at 4 • C. The concentrated feed is transferred to a stirring bucket where it is diluted with tap water to have a similar composition to typical domestic wastewater used in other researches [22,31], as shown in Table S1. The reactors were made of acrylic with the dimensions of 8 cm × 15 cm × 40 cm (L × W × H) to have 4 L of effective mixed liquor volume with 35 cm liquid depth.…”

“…Entrapment of bacterial cells in the media (also referred to as immobilization or encapsulation) has been used to protect specific bacteria from harsh environments before the development of the QQ technique in the MBR research field [ 17 , 18 ]. Bead-type media which entrap bacterial cells have been called cell-entrapping beads [ 13 , 19 , 20 , 21 , 22 ]; however in the study, they were named cell-immobilizing beads (CIB) instead of cell-entrapping beads as to not to cause confusion with the CEB acronym for chemi-cally enhanced backwash. QQ-CIBs made of sodium alginate alone were introduced first and showed great potential to mitigate biofouling due to the synergetic combination of the QQ effect and the physical-cleaning effect [ 13 , 23 ].…”

“…QQ-CIBs made of sodium alginate alone were introduced first and showed great potential to mitigate biofouling due to the synergetic combination of the QQ effect and the physical-cleaning effect [ 13 , 23 ]. However, the sodium alginate beads were not stable in real wastewater [ 18 , 21 , 22 , 24 ]. Because poly vinyl alcohol (PVA) beads were known to have high durability and good mechanical and chemical strength [ 25 ], QQ bacteria were immobilized in PVA-alginate beads for longer use of the CIBs with real wastewater in MBRs [ 24 ].…”

Prolonging the Life Span of Membrane in Submerged MBR by the Application of Different Anti-Biofouling Techniques

“…Quorum quenching (QQ) is a new technique which is used nowadays to mitigate biofouling. It is considered that QQ might be one of the most promising and useful methods in disrupting cell-to-cell communication of the bacteria responsible for biofouling in MBR [ 16 ].…”