POLYMER-IMMOBILIZED PHOTOSENSITIZERS FOR WASTEWATER DISINFECTION

The problem of amount and quality of fresh water in areas with limited natural water resources raises the necessity of treatment and disinfection of wastewater for further irrigation. Existing methods of wastewater disinfection are based on the use of aggressive chemicals such as hypochlorites, chlorine dioxide, and ozone, or on power-consuming physical methods such as UV radiation. A good alternative to these methods may involve the use of photosensitizers immobilized onto a solid phase. This approach is based on excitation of photosensitizers by visible light followed by energy transfer from molecules of the photosensitizers to the oxygen dissolved in the wastewater. This leads to the production of reactive oxygen species which cause direct and indirect irreversible damage to cellular components of bacteria and induce cell death. In the present work the antimicrobial activity of immobilized photosensitizers in polymers was tested against Gram-positive S. aureus. Two water-soluble photosensitizers (Rose Bengal sodium salt and methylene blue) and two water-insoluble compounds (hematoporphyrin and Rose Bengal lactone) were immobilized by dissolution in a melted polyethylene by a method of extrusion to yield rods having 3 mm in a diameter and 3-5 mm beads. All four photosensitizers were found to be effective in eradication of bacteria in a batch regime under illumination with a white luminescent lamp or sunlight. The use of the immobilized photosensitizers allows to remove them easily at the end of the treatment, to reuse them and to apply for continuous disinfection of wastewater.