PM03 Treatment or Removal of Emerging Contaminants
Exhibit Hall
8:00 AM - Monday
(PM020) Assessing the microbial toxicity of pentachlorophenol-contaminated water after treatment with UV radiation and TiO2 photocatalyst.
Kim, J1, Cho, I1, Zoh, K1, Choi, K1, 1 Seoul National University, Seoul, Korea
ABSTRACT- Degradation efficiency of pentachlorophenol (PCP) by using direct UV photolysis and TiO2 photocatalysis was evaluated with both chemical analyses and acute toxicity assessment employing luminescent bacteria Vibrio fischeri. PCP has been widely used as fungicide, bactericide, insecticide and wood preservative in agriculture and many industries, and its ecological hazard is well-known. The acute toxicity to the microbe was reduced by >60% when applying UV alone, and was completely removed when treated with UV-TiO2 combinations. Toxicity reduction pattern determined with the Microtox Assay generally corresponds with the chemistry data: However, it should be noted that toxicity was greater than expected by the chemistry data. Formation of tetrachlorobenzoquinone, a toxic degradation byproduct, could not explain observed microbial toxicity. These observations are probably due to the presence of unidentified toxic PCP byproducts, which may include polychlorinated dibenzodioxins and polychlorinated dibenzofurans. When Microtox results were compared between different exposure time, i.e., 5 min and 15 min, an interesting pattern was noted with UVA-TiO2 treatment. While no microbial toxicity was observed with 5 min exposure, an EC50 value of 45.4% was estimated with 15 min exposure, which was not observed in UVB-TiO2 exposure. This result suggests the presence of unknown toxic degradation products are generated in the later stage of treatment. Based on this study, TiO2 photocatalyst, together with UVB photolysis could improve the removal of both PCP and its toxic derivatives in more efficient way. The Microtox Assay is promising and economical method for monitoring efficiency of wastewater treatment options.
Key words: pentachlorophenol, Vibrio fischeri, UV, TiO2