Notice bibliographique
Résumé
This thesis investigates the idluence of sludge retention tirne (SRT) on surface properties and interparticle interactions of sludge flocs, and the role of surface properties and interparticle interactions in bioflocculation, compaction and stability.Four laboratory-scale sequencing batch reactors (SBRs) were operated in parallel at different SRTs (4 to 20 days) for two years.Surface properties of sludge flocs were examined by a number of state-of-the-art techniques, including physicochemical extraction, chemical analyses and ~Itrafiltration of extracellular polymeric substances (EPS), contact angle measurement (hydrophobicity) and colloidal titration (surface charge).Interparticle interactions (electrostatic, ionic interactions and hydrogen bonds) and the stability of sludge flocs at differmt SRTs were evaluated in batch expenments by manipulating the water chemistry of the surrounding solutions.At al1 SRTs, proteins and carbohydrates were the dominant components of EPSI followed by a small amount of DNA.Acidic polysaccharides were not detected in the EPS.Molecular weights of proteins, carbohydrates and DNA in the EPS covered a broad range, fkom less than 1,000 daltons to more than 100,000 daltons.The majority (>85%) of EPS components had molecular weights larger than 10,000 daltons.The total amount of EPS was independent of the SRT.The ratio of proteins to carbohydrates in the EPS, however, increased fiom 1.5 (c0.9) at an SRT of 4 days to 5.1 ( 2 1.5) at an SRT of 12 days, and then reached an almost constant value of 4.5 (I 1.9) at SRTs from 16 to 20 days.A larger arnount of EPS was associated with a higher sIudge volume index (SVI), but no significant correlation was found between the amount of EPS and effluent suspended solids (ESS).Sludge surfaces were more hydrophobic (a higher value of water contact angle) and less negatively charged at higher SRTs (16 and 20 days) than those at lower SRTs (4 and 9 days).The contact angle values were strongly correlated to the surface charge density.A change in the proportion of EPS components provides partial explanations for changes in hydrophobicity and surface charge with respect to the SRT.A higher contact angle and lower surface charge were associated with a lower level of ESS.There was no correlation, however, either between the SV1 and contact angle or between the SV1 and surface charge.Changes in dissociation constants of sludge flocs in batch experiments indicated that electrostatic interactions were involved in disruptinp the stability of sludge flocs, and ionic interactions and hydrogen bonds were present to compensate for the negative influence of electrostatic interactions on the stability of sludge flocs and to keep flocs together.Ionic interactions and hydrogen bonds were two dominant forces that maintained the stability of sludge flocs at lower SRTs: while other mechanisms, such as physicai enmeshment and hydrophobic interactions.were likely more important than ionic interactions and hydrogen bonds in controlling the stability of sludge flocs at higher SRTs.Sludge flocs at higher SRTs (16 and 20 days) were structurally more stable than those at lower SRTs (4 and 9 days).In summary, the results from this study demonstrate that it is possible to operationally and chemically manipulate surface properties and interparticle interactions of sludge flocs for effective floc separation.A transition in floc surface properties \vas found to occur in the SRT range of 9 to 12 days.This transition in floc surface properties was linked to irnproved bioflocculation and a more stable fioc structure.It is the physicochemical properties of sludge flocs, such as hydrophobicity and surface charge, rather than the quantity of EPS, that govem the flocculating ability.In contrast, the total EPS content plays a more important role in determining the compressi bi lity of sludge flocs than hydrophobicity and surface charge.A conceptual mode1 is proposed to describe the floc structure of floc-forming microorganisms at different SRTs.1 am grateful to my supervisors.Prof Steven N. Liss and Prof. D
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 distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| 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) | 0,026 | 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 tête enseignante, 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 ».