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In comparison to alternative advanced wastewater treatment technologies, the main problem associated with membrane bioreactor (MBR) technology, which has become prominent in recent years, is biofouling. Within these systems, biofouling is typically the result of a biofilm layer resulting from bacterial gathering. One biological system that can be employed to interrupt the process of bacterial gathering is called 'Quorum Quenching (QQ)'. Existing QQ applications can be classified using three main types: 1) bacterial/whole-cell applications, 2) direct enzyme applications, and 3) natural sourced compounds. The most common and widely recognized applications for membrane fouling control during MBR operation are bacterial and direct enzyme applications. The purpose of this review was to identify and assess biofilm formation mechanism and results, the suggestion of the QQ concept and its potential to control biofilm formation, and the means by which these QQ applications can be applied within the MBR and present QQ MBR studies.

Aquaporins have high water permeability and selectivity, which make them attractive to use in membrane applications for water purification and desalination. Due to their hydrophobic nature, they have to be embedded in cell membrane-like structures such as liposomes to form proteoliposomes. In this study, the effects of aquaporin Z (AqpZ) addition on liposome characteristics and behavior were investigated by evaluating the adsorption of proteoliposomes onto gold as reference substrate, polysulfone (PS) and polyacrylonitrile (PAN) spin-coated sensor surface as common nanofiltration membrane material by quartz crystal microbalance with dissipation. AqpZ incorporation into liposomes did not significantly change mean liposome diameter and surface charge, but the water permeability was increased up to almost sixfold. The results of viscoelastic modeling showed a stiffer membrane structure for the lipid bilayer of proteoliposomes compared to that of liposomes. Although liposomes and proteoliposomes were found to be adsorbed successfully on negatively charged PS and neutral PAN surfaces, the interaction strength and adsorption rate were found to be different for polymers with different surface properties, indicating the importance of the polymer for the stabilization of proteoliposomes. Findings of this study offer valuable information about the incorporation of proteoliposomes in membrane structures for the fabrication of nanofiltration membranes.

In this study, the dominant and representative bacteria of activated sludge before and after the addition of different nanomaterials (NMs) (multiwalled carbon nanotube, MWCNT, silicon dioxide nanoparticle, nSiO 2 , titanium oxide nanoparticle, nTiO 2 , aluminum oxide-nanoparticle, nAl 2 O 3 , and silver nanoparticle, nAg) were separately isolated, enumerated, and identified. In total, 17 different representative isolates were identified by using 16S rDNA gene sequence analysis. The effects of NMs on the growth (viable counts), biological oxygen demand (BOD) removal performances, respiration mechanism, and extracellular polymeric substances (EPS) production of bacteria were also investigated. Both BOD removal capacity and respiration rate of bacterial medium decreased after NMs exposure. Most toxic NMs were MWCNT (46.15%) and nAg (42.30%) related with BOD removal capacity and nAg (62%) and nTiO 2 (56%) for respiration mechanism. Therefore, the protein content of soluble EPS (sEPSp) increased with addition of nAg, nTiO 2 , and nAl 2 O 3 . NMs also have negative effect on the structure of community of activated sludge in both diversity and density.