Biofilm control in water by advanced oxidation process (AOP) pre-treatment: effect of natural organic matter (NOM)

The main goal of this study was to examine the influence of natural organic matter (NOM) on the efficiency of H?O?/UV advanced oxidation process (AOP) as a preventive treatment for biofilm control. Pseudomonas aeruginosa PAO1 biofilm-forming bacteria were suspended in water and exposed to various AOP conditions with different NOM concentrations, and compared to natural waters. H?O?/UV prevented biofilm formation: (a) up to 24 h post treatment - when residual H?O? was neutralized; (b) completely (days) - when residual H?O? was maintained. At high NOM concentrations (i.e. 25 mg/L NOM or 12.5 mg/L DOC) an additive biofilm control effect was observed for the combined H?O?/UV system compared to UV irradiation alone, after short biofilm incubation times (<24 h). This effect was H?O? concentration dependent and can be explained by the high organic content of these water samples, whereby an increase in NOM could enhance (?)OH production and promote the formation of additional reactive oxygen species. In addition, maintaining an appropriate ratio of bacterial surviving conc.: residual H?O? conc. post-treatment could prevent bacterial regrowth and biofilm formation.