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

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.