Degradation of phenol and chlorophenols by sunlight and microbes in estuarine water

Microbial and photochemical degradation of phenol and chlorophenol in natural waters is discussed. Surface water samples were collected during high tide periods from Skidaway river. Radiolabelled compounds, including phenol, p-chlorophenol, 2,4-dichlorophenol and 2,4,5-trichlorophenol, dissolved in acetone, were added to water samples. Covered flasks were used to study dark reactions. Reactions due solely to photolysis were studied by replicate experiments with flasks containing formaldehyde. Compound transformation was determined by liquid/liquid extraction and thin layer chromatography, followed by determination of radioactivity with a liquid scintillation counter. Mineralization was determined by measurement of evolved radiolabelled carbon dioxide. Microbial biomass and activity measurements were also determined. Results presented showed that photolysis was the primary transformation process for the polychlorinated phenols. Measured photolysis rates for dichlorophenol were 20-80 per cent higher in estuarine water than in distilled water indicating a photosensitized reaction. During incubation periods up to 3 days, no microbial degradation of polychlorinated phenols was observed. The photoproducts of polychlorinated phenols were found to be rapidly degraded by microbes. Microbial degradation was found to be the major process for transformation of phenol and p-chlorophenol. Measured winter photolysis rates and microbial degradation rates were found to be lower than corresponding summer values.