Photocatalytic treatment of toxic organics in wastewater: Toxicity of photodegradation products

The tested compounds, methyl vinyl ketone, pentachlorophenol and 2,4-dichlorophenol, inhibited the respiratory activity of activated sludge. Detoxification of these compounds was achieved by exposing the compounds (75 mg/l) to sunlight with the addition of TiO 2 (1000 mg/l), which acts as a photocatalyst. Ultraviolet absorption spectra of the photocatalytically treated samples were deprived of the characteristic peaks showing that the compounds have undergone photoxidation. Prior to complete detoxification of pentachlorophenol and 2,4-dichlorophenol there was an increased inhibition of the activity of the activated sludge, indicating the photocatalytic generation of intermediary toxic products.