Water Disinfection by Immobilized Photosensitizers

Anton Valkov,Kate Raik,Marina Nisnevitch,Faina Nakonechny,Yamit Mualem-Sinai

doi:10.3390/w11010026

Abstract

Fresh water shortage has become a global problem. A partial solution for this problem is the use of treated and disinfected wastewater for irrigation. However, most existing wastewater disinfection methods are based on the use of aggressive chemicals or power-consuming physical processes. Photodynamic eradication of waterborne bacteria by immobilized photosensitizers may be a good alternative to conventional methods. In the present work, the photosensitizers Rose Bengal sodium salt, Rose Bengal lactone, methylene blue, and hematoporphyrin were immobilized in polyethylene or polypropylene using a “green” method of co-extrusion, without addition of any chemicals, yielding polymeric strips and beads containing the photosensitizers. The antibacterial efficiency of these immobilized photosensitizers was tested against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli in batch and continuous regimes upon illumination with a white luminescent lamp. All examined photosensitizers demonstrated a good ability to decrease the bacterial concentration, up to their total eradication. Immobilized photosensitizers are proposed for batch or continuous disinfection of wastewater after secondary treatment.

Highlights

Use of treated and disinfected wastewater for irrigation can be a good solution for conserving drinking water in areas with limited natural water resources
We have previously reported inclusion of PSs into a polymeric film by mixing solutions of PSs in chloroform with solutions of polystyrene, polycarbonate or poly(methyl methacrylate) in the same solvent, with subsequent air evaporation of the latter
Thermal stability of Rose Bengal lactone (RBL), Rose Bengal (RB), and methylene blue chloride·3H2 O (MB) was tested by the TGA-DSC method and decomposition temperatures were determined from TGA thermal curves and data on HP was obtained from literature [29]

Summary

Introduction

Use of treated and disinfected wastewater for irrigation can be a good solution for conserving drinking water in areas with limited natural water resources. Existing methods of bacterial eradication in wastewater involve the use of aggressive chemicals, such as chlorine-based compounds and ozone, or power-consuming physical methods, such as UV radiation. Photodynamic treatment with the help of photosensitizers may comprise an alternative approach to wastewater disinfection [1,2]. Photosensitizers (PSs) are colored compounds which are excited under illumination by visible light and can either transfer their excitation energy or exchange an electron with other substances [3]. PSs can respectively follow two pathways, named Type I and Type II reactions.

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