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.

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