Control of biofilm thickness in membrane biofilm reactor by using quorum quenching method

Membrane biofilm reactor (MBfR) is advanced a treatment technology that has the potential for widespread use for drinking water and wastewater treatment in the future. MBfR is considered as a remarkable technology in terms of providing gas transfer by diffusion through membrane fibers and providing an effective surface for biofilm growth. The main problem of MBfR systems is the uncontrolled increase of biofilm thickness on the membrane surface. Excess biomass accumulation on the membrane surface with the increase in biofilm thickness causes non-uniform gas transfer and consequently the system performance decreases. Therefore, rapid biofilm formation on the membrane surface is one of the main factors restricting the use of MBfR systems in the drinking water and wastewater treatment plants. In this study, it is expected to overcome this problem by "Quorum quenching (QQ)" allowing control of biofilm. In the study, biofilm thickness on the membrane surface was kept under the control by using method of QQ in the MBfR based on oxygen (O2-MBfR). For this purpose, firstly biofilm thickness using of a single isolated QQ bacteria was kept to an optimum level and the sustainability of system performance was investigated. In the second stage, bacterial isolation with QQ activity was performed in different media. Species exhibiting the highest QQ activity were added to the alginate capsules immobilized by reactors. Within the scope of thesis study, QQ activity and effect on the O2-MBfR performance, biofilm structure and microbial community changes in biofilm was studied in detail. The main objective here is to investigate the effect of the system on performance by controlling the biofilm thickness in the O2-MBfR system by QQ applications rather than the treatment performance. The results of the study obtained for the Rhodococcus sp. BH4 bacterium showed that the biofilm thickness on the membrane surface was effectively maintained, especially at 12 h hydraulic retention time (HRT), 6 psi O2 gas pressure and 15 ml QQ bead concentration. The species with the highest QQ activity as a result of bacterial isolation can be listed Bacillus methylotrophicus, Klebsiella pneumoniae, Lysinibacillus fusiformis, Achromobacter xylosoxidans.