We describe the concept and demonstrate the efficacy of a novel SWNT-MWNT hybrid filter for the removal and inactivation of microbial pathogens from water. The filter is composed of a thin SWNT layer (0.05 mg cm(-2)) on top of a thicker MWNT layer (0.27 mg cm(-2)) supported by a microporous support membrane. The SWNT-MWNT filter exhibits high log removal of several model viruses (MS2, PRD1, and T4 bacteriophages) by depth filtration, which predominantly takes place in the thicker and more uniform MWNT layer. The filter removes all bacteria by a sieving mechanism, with the top SWNT layer providing high levels of inactivation of model bacteria (Escherichia coli K12 and Staphylococcus epidermidis), as well as microbes from river water and treated wastewater effluent. The dual-layer SWNT-MWNT filter lays the framework for new possibilities in point-of-use water filtration.

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a b s t r a c tQuorum sensing inhibition (QSI) has been suggested as a potential solution to suppress the growth of biofilm on solid surfaces using pure enzymes or enzyme producing. In this study, three plant-oriented organic molecules (cinnamaldehyde, CIN; vanillin, VAN; zingerone, ZIN) were applied as QSIs in forward osmosis (FO) membrane system using Pseudomonas aeruginosa PAO1 as a model biofoulant. After 36 h of FO operation, all tested experiments with QSIs exhibited the retarded flux decline, and resulted in the increase in accumulated permeate volume by 5% (CIN), 21% (VAN), and 15% (ZIN) compared with that of control. It was due to the difference in the characteristics of biofilm formed on the membrane surface, that the biomass on the unit area of membrane surface with QSIs was decreased by 68%, 41%, and 15% in the presence of CIN, VAN, and ZIN, respectively. In the absence of QSIs, membrane surface turned more hydrophobic, which hindered the transport of permeate water due to the formation of hydrophobic biofilm, while those in the presence of QSIs possessed similar contact angle compared with that of the virgin membrane. Furthermore, the amount of extracellular polymeric substances per unit area of membrane was reduced significantly in the presence of QSIs. In conclusion, the addition of QSIs can be the economically feasible strategy to mitigate biofouling not only reducing the amount of biofilm on the membrane surface but also modifying properties of biofilm.

This study focused on the physicochemical and biological characteristics of sludge in submerged membrane bioreactors (MBRs), and their roles in the formation of dynamic membrane and membrane fouling. Three lab-scale submerged MBRs with SRT of 20, 40 and 60 days were performed at a constant permeate flux of 9 L/m 2 /h. Better permeability was achieved at longer SRT (40 and 60 days) with higher sludge concentrations because of the formation of dynamic cake layer. At of SRT 20 days, pore blocking and pore narrowing were more significant having lower sludge concentration. It was found that higher microbial concentration had better permeability, resulting in the formation of dynamic membrane. Size of particulates and colloids, and surface properties of microbial floc appeared the major parameters for the formation of dynamic membrane in the submerged MBRs.

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Wastewater treatments such as forward osmosis (FO) can be widely applied to separate or the reject substances from secondary treated effluents. Experimental studies have investigated the influence of membrane fouling and operating conditions. The performance of FO is affected by membrane fouling characteristics, composition of the feed solution and operating conditions. The experiments were performed using an osmotic membrane (FO-4040) to investigate the influences of operating conditions on water flux and reverse salt selectivity. The surfactant content, cross-flow velocity, and pH of the feed solution were systematically investigated for their effects on FO performance. The results showed that higher cross-flow velocities, increase of the pH of the feed solution, and adding surfactant into the feed solution yielded higher water fluxes. Reverse salt selectivity also increased after adding a surfactant to the feed solution but showed no significant increase at higher surfactant concentrations.

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