| Summary: | 博士 === 國立臺灣大學 === 環境工程學研究所 === 99 === Pharmaceuticals are widely used not only for curing human and animal diseases, but also in farming and aquaculture. Depending on the nature of the pharmaceuticals, parent compounds and metabolites of pharmaceuticals are excreted via urine and feces. Most of wastewater is typically treated by wastewater treatment plants (WWTPs). Since the existing domestic WWTPs are not specially designed for pharmaceuticals removal, their removal in WWTPs is often incomplete, and the degree of removal varied broadly from nearly complete to very little. In general, the removal of pharmaceuticals increases with the increase of solid retention time. Immobilized cell biological process is one of the biological treatment technologies with longer sludge retention time and combination of aerobic and anaerobic process that has excellent potential for carbon and nitrogen removal.
The aims of this study were to: 1) investigate treatability of eight selected pharmaceuticals (four antibiotics: sulfamethoxazole, sulfadimethoxine, sulfamethazine and trimethoprim and four non-steroidal anti-inflammatory drugs (NSAIDs): acetaminophen, ibuprofen, naproxen and ketoprofen) with various influent concentrations by up-flow immobilized cell bio-process at a constant operation, 2) evaluate potential elimination mechanism (bio-degradation, bio-sorption, hydrolysis and volatilization) and their kinetics using batch experiment, and 3) study sorption/desorption capacity and solid-liquid partitioning coefficient by batch experiment.
These removal efficiencies are good and steady even at high initial concentrations, removal rate ranging from 0.5 µg/g-sludge/day (at 5 µg/L) to 12.3 µg/g-sludge/day (at 100 µg/L) for acetaminophen and ibuprofen, 0.6 ~ 1.6 µg/g-sludge/day (at 5 ~ 15 µg/L) for ketoprofen and naproxen, 0.2 ~ 0.9 µg/g-sludge/day (at 2 ~ 10 µg/L) for sulfonamide antibiotics, and 0.1 µg/g-sludge/day (at 1 µg/L) for trimethoprim.
In the batch experiment, bio-degradation and bio-sorption were found to be the dominant elimination routes, while volatilization and hydrolysis can be ignored for all target pharmaceuticals. Based on the batch experiment results, acetaminophen was characterized by significant biodegradability and sorption, resulting in 100% removal in 8 days via sorption and > 25% removal by bio-degradation within 2 days. Sulfamethoxazole, sulfadimethoxine, ibuprofen and naproxen were fairly well biodegraded (> 40% removal) and hardly sorbed (< 40% removal) to the bio-carriers. Sulfamethazine and ketoprofen were slowly biodegraded and weakly sorbed, resulting in removal of 23% and 28% by bio-degradation and 20% and 18% by sorption. The fate of trimethoprim was characterized by low biodegradability (27%) and medium sorption (47%). Based on pseudo-first bio-sorption-degradation kinetic rate constants of target pharmaceuticals, acetaminophen and ibuprofen are readily bio-sorption-degradable substances, followed by sulfamethoxazole, sulfadimethoxine, naproxen and trimethoprim are slowly, while sulfamethazine and ketoprofen are hardly bio-sorption-degradable pharmaceuticals. Moreover, the time required for 90% removal (t90) via bio-sorption-degradation for acetaminophen and ibuprofen were 2.1 and 2.6 days, followed by sulfamethoxazole, sulfadimethoxine, trimethoprim and naproxen (7.2 ~ 14.3 days), while sulfamethazine and ketoprofen were persistent in immobilized cell system due to their longer t90 of 2.2 ~ 13.3 days.
In the sorption/desorption experiment, acetaminophen, sulfamethoxazole and sulfadimethoxine were characterized by strong sorption and weak desorption. A phenomenon of moderate sorption and well desorption was observed for sulfamethazine, trimethoprim and naproxen. Both ibuprofen and ketoprofen were weakly sorbed and strongly desorbed.
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