Abstract
The photosensitizers Rose Bengal (RB) and methylene blue (MB), when immobilized in polystyrene, were found to exhibit high antibacterial activity in a continuous regime. The photosensitizers were immobilized by dissolution in chloroform, together with polystyrene, with further evaporation of the solvent, yielding thin polymeric films. Shallow reservoirs, bottom-covered with these films, were used for constructing continuous-flow photoreactors for the eradication of Gram-positive Staphylococcus aureus, Gram-negative Escherichia coli and wastewater bacteria under illumination with visible white light using a luminescent lamp at a 1.8 mW·cm−2 fluence rate. The bacterial concentration decreased by two to five orders of magnitude in separate reactors with either immobilized RB or MB, as well as in three reactors connected in series, which contained one of the photosensitizers. Bacterial eradication reached more than five orders of magnitude in two reactors connected in series, where the first reactor contained immobilized RB and the second contained immobilized MB.
Highlights
A deficiency in freshwater resources leads to serious water quality and quantity problems in the Middle East region
In our previous works we described a series of batch experiments in which the photodynamic antibacterial activity of Rose Bengal (RB) and methylene blue (MB) was studied when these photosensitizers were in a free form, encapsulated into liposomes or immobilized in polymers [28,29,30,31,32,33,34,35,36,37]
In the present work we report the continuous photoeradication of Gram-positive Staphylococcus aureus, Gram-negative E. coli and wastewater coliform bacteria by MB and RB immobilized in polystyrene
Summary
A deficiency in freshwater resources leads to serious water quality and quantity problems in the Middle East region. PS in solutions demonstrated high efficiency in killing fecal coliforms and streptococci, it should be noted that use of PS in solutions is problematic, due to the need for constant addition of PS to the treated wastewater and the necessity of removing the PS after the treatment These problems can be solved by immobilization of the PS onto a solid phase. Attempts to apply immobilized PS for wastewater disinfection and for production of antibacterial surfaces were described by Jiménez-Hernández et al [22], Bonnett et al [23], Villén et al [24], Manjón et al [25,26], Sabbahi et al [10], and Cahan et al [27] For this purpose, PS were attached onto solid supports, such as chitosan, polyester isophtalic resin, porous poly(dimethylsiloxane) (silicone), cationic nylon, polyethylene, poly(vinylidene difluoride), and cellulose membranes by adsorption, dissolution and casting, covalent bonding or by an electrostatic interaction. In the present work we report the continuous photoeradication of Gram-positive Staphylococcus aureus, Gram-negative E. coli and wastewater coliform bacteria by MB and RB immobilized in polystyrene
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