Inhibition of biofilm formation on FO membrane surface by plant-oriented organic molecules

Quorum 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.