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Browsing by Author "Ryan, Christopher Charles"

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    Photolysis and digestion as polishing steps for the removal of antibiotics from municipal wastewater treatment plant effluent and biosolids.
    (2009-10) Ryan, Christopher Charles
    The degradation of five pharmaceuticals and personal care products, tetracycline, triclosan, tylosin, sulfamethoxazole, and trimethoprim was examined. The photolysis of these compounds was studied in pure water, wastewater treatment plant effluent, and natural waters. The biodegradation of the substances, excluding tetracycline, was examined during both aerobic and anaerobic sludge digestion. Tetracycline, triclosan, and tylosin were shown to degrade rapidly under both natural and simulated sunlight. Sulfamethoxazole and trimethoprim did not photodegrade as rapidly as the other compounds. These two compounds, however, did degrade more quickly in wastewater treatment plant effluent than in pure water or natural water. This observation indicated indirect photolysis was an important loss process for these compounds in the effluent. The cause of indirect photolysis was shown to be both triplet-excited dissolved organic matter and hydroxyl radicals reacting with the sulfamethoxazole and trimethoprim. During aerobic digestion, trimethoprim degraded in the room temperature, 45 °C, and 55 °C digesters, and in the 35 °C digester during anaerobic digestion. Degradation did not occur in the 35 °C aerobic digester. Tylosin degraded during aerobic digestion in the 35 °C and 55 °C digesters. Degradation did not occur in the room temperature aerobic digester or in the 35 °C anaerobic digester. Sulfamethoxazole was not detected in any of the digester samples, despite being spiked in initially. Triclosan concentrations in the digester samples were always at least an order of magnitude higher than expected based on amount spiked in, indicating that a large amount of the compound was present in the digester sludge prior to spiking.