Quorum Quenching (QQ) bacteria such as Rhodococcus sp. BH4 and Pseudomonas putida have excellent anti-biofouling potential as they disrupt Quorum Sensing (QS) system and inhibit biofilm formation on membranes. Cell Entrapping Beads (CEBs) in which the QQ bacteria are immobilized is one of the most effective methods to mitigate membrane biofouling in MBR. The CEBs are very crucial as they mainly protect QQ bacteria from harsh environment of the sludge for better QQ effect and help in physical cleaning of membranes in a submerged MBR. Previously simple sodium alginate (SA) beads were used but it was found that their durability was very low in real wastewater. Polyvinyl Alcohol (PVA) is a better alternative due to its higher durability, chemical stability and low cost. Several brands of PVAs with different polymerization degrees were used here and small amount of SA was added to avoid agglomeration of PVA beads. Concentrations of SA/PVA were varied and different temperature of cross-linking solution also was examined. Then quality of the beads was evaluated on physical and biological aspect. It was found that a PVA of 2,270 polymerization degree with 8% mixed in 1% SA makes the most stable CEBs. A certain brand of SA didn’t prevent agglomeration of CEBs while a specific brand of SA did even at lower concentrations. Temperature of cross-linking solution also was found to have significant effect on internal structure of beads. The quality of CEBs made by the best method found in this research was confirmed through series of tests, i.e. freeze drying, scanning electron microscopy, activity test after immobilization of QQ bacteria in the beads.

Biofouling is one of the main drawbacks of membrane bioreactors (MBRs). Among the different methods, the quorum-quenching (QQ) technique is a novel method as it delays biofilm formation on the membrane surface through disruption of bacterial cell-to-cell communication and thus effectively mitigates membrane biofouling. QQ bacteria require a certain concentration of dissolved oxygen to show their best activities. Despite the importance of the amount of aeration, there have not been enough studies on aeration condition utilizing the separate determination of pure QQ effect and physical cleaning effect. This research aimed to find the optimum aeration intensity by separation of the two effects from QQ and physical cleaning. Three bead type conditions (no bead, vacant bead, and QQ beads) at three aeration intensities (1.5, 2.5, and 3.5 L/min representing low, medium, and high aeration intensity) were applied. From the results, no QQ effect and small QQ effect were observed at low and high aeration, while the greatest QQ effect (48.2% of 737 h improvement) was observed at medium aeration. The best performance was observed at high aeration with QQ beads having a 1536 h operational duration (303% improvement compared to the no bead condition); however, this excellent performance was attributed more to the physical cleaning effect than to the QQ effect.

This work presents the dynamic modeling of drying behavior of polymer solutions in an infrared-convective oven. Two study cases were considered for the drying process. The first one deals with the drying of a coated polymer solution on a fixed substrate while the second one includes drying of the same solution on a moving substrate in an infrared (IR) oven. Both models involve simultaneous heat and mass transfer equations that describe changes in the solvent concentration and the polymer temperature during the drying process. The set of partial differential equations (PDEs) arising from the mass and energy balances constitute a highly nonlinear system due to inter-dependence of the thermodynamic and transport properties of polymer solutions. The models were numerically solved and were validated using published experimental data. The models were employed to simulate the drying of a polyvinyl acetate coating (in toluene) on a polyester substrate. Results obtained from the derived model demonstrated the importance of parameters such as web velocity, heater temperature, and inlet air velocity in the IR drying process. In general, high temperature and air velocity cause rapid drying of the polymer coating, while high substrate velocity resulted in drying. This model can be applied on any industrial applications that include continuous IR drying process of polymer-coated layers to predict the drying behavior of the coated product.