Biological removal of sulfamethoxazole and 17 α-ethinylestradiol and the impact of ozone on biodegradability, estrogenicity and toxicity
Notice bibliographique
Résumé
The potential development of antibacterial resistance and endocrine disruption has led to increased research investigating the removal of antibiotics like sulfamethoxazole (SMX) and estrogens like 17alpha-ethinylestradiol (EE2) during biological wastewater treatment (activated sludge). Lab-scale studies have been carried out by researchers using activated sludge samples and bacterial isolates to investigate the biodegradability of these pharmaceutical compounds with varying and sometimes contradictory results. Both SMX and EE2 can react quickly with ozone (O₃) thus the implementation of O₃ as a final disinfection step during wastewater (WW) treatment may also result in the removal and transformation of these pharmaceutical compounds. However, the identification and characteristics of the ozonation by-products formed as a result of this treatment has yet to be fully explored. Ozone has also been predicted to increase WW biodegradability, suggesting its potential as a pre-treatment to activated sludge. The work presented in this thesis proposes an innovative way to evaluate changes in biodegradability and investigate the potential impact of transformation products. The use of controlled mixtures of pure bacterial cultures to model the biodegradation of SMX and EE2 at lab-scale was studied. This approach ensures a consistent microbial population that can be precisely repeated throughout a set of experiments, allowing the direct comparison of results, which is not possible using activated sludge samples due to their variable composition. The results showed that specific individual bacteria (R. equi and R. rhodocrous) were capable of successfully degrading SMX and EE2, however when they were combined with other bacteria to form mixtures there were no additive or synergistic effects observed. Using the controlled bacterial mixtures to model the biodegradation of SMX and EE2 separately, we were able to investigate the effects of the addition of an excess carbon source as well as ozone pre-treatment on the biodegradability of these compounds. The results demonstrated that there were no overall trends of co-metabolism of either compound with the excess carbon source and that slight differences in the bacterial composition of the mixture used (±1 to 2 bacterial strains) can alter the degradation trends observed (i.e. rate of compound removal). In general, ozonation increased the biodegradation of SMX by the bacterial mixtures; however the removal of EE2 was decreased. This was explained by the formation of an ozonation by-product that was preferentially biodegraded over EE2. We also investigated the ozone by-products formed after the complete disappearance of EE2. Two of these by-products were identified as open phenolic ring structures, suggesting a decrease in estrogenic activity. Using the YES assay these by-products were determined to be significantly less estrogenic than EE2, however they were observed to be more toxic to male fetal rats (15.5. days post-conception) demonstrating a greater negative impact on testosterone secretion. This emphasizes that a better understanding of emerging treatments such as ozonation is necessary before applying them in water treatment since the by-products may exhibit a greater toxic effect than the untreated parent compound.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».