Biofilm control in water by a UV-based advanced oxidation process

Abstract

An ultraviolet (UV)-based advanced oxidation process (AOP), with hydrogen peroxide and medium-pressure (MP) UV light (H₂O₂/UV), was used as a pretreatment strategy for biofilm control in water. Suspended Pseudomonas aeruginosa cells were exposed to UV-based AOP treatment, and the adherent biofilm formed by the surviving cells was monitored. Control experiments using H₂O₂ or MP UV irradiation alone could inhibit biofilm formation for only short periods of time (<24 h) post-treatment. In a H₂O₂/filtered-UV (>295 nm) system, an additive effect on biofilm control was shown vs filtered-UV irradiation alone, probably due to activity of the added hydroxyl radical (OH•). In a H₂O₂/full-UV (ie full UV spectrum, not filtered) system, this result was not obtained, possibly due to the germicidal UV photons overwhelming the AOP system. Generally, however, H₂O₂/UV prevented biofilm formation for longer periods (days) only when maintained with residual H₂O₂. The ratio of surviving bacterial concentration post-treatment to residual H₂O₂ concentration played an important role in biofilm prevention and bacterial regrowth. H₂O₂ treatments alone resulted in poorer biofilm control compared to UV-based AOP treatments maintained with similar levels of residual H₂O₂, indicating a possible advantage of AOP.

Keywords:

• advanced-oxidation
• biofilm
• biofouling
• disinfection
• ultraviolet
• water-treatment

Acknowledgements

This research is sponsored by the MAGNET Program of the Office of the Chief Scientist of the Ministry of Industry, Trade & Labor, Grant no. 2668. The authors acknowledge Atlantium Technologies Ltd and especially Dr Tali Harif and Dr Vladimir Glukhman for their fruitful collaboration and insights on UV, and thank Dr Alex Barbul, from the IDRFU (Inner Departmental Research Facility Unit), Tel-Aviv University, for his kind assistance with the confocal microscopy.