The identification of variable shear strength of particles deposited on drinking water PVC pipes after the passage of a suspended particle plume in a full-scale laboratory system
Notice bibliographique
Résumé
Understanding the adhesion properties of sediments that accumulate on the wall of drinking water pipes is an important step in the development of mitigation strategies to prevent the formation of deposits and protect drinking water. Research based on flushing of operational pipe mains that mobilized particulate sediments from isolated pipe sections has shown that fine iron oxide particles are a recurrent major component of these deposits. In addition, it has been established that adhesion forces proportional to the flow wall shear stress (WSS) develop between the pipe wall and accumulated particles, which prevents the washing-off of particles during common conditioning flows and provokes a rapid resuspension during high-flow events that cause water discolouration. Discolouration models have also showed that sediments have a variable shear strength, and, therefore, a fraction of material may resist a first increase in WSS but then be mobilized after a second increase in WSS. To explain the variable shear strength of layers, researchers have hypothesized that sediments accumulate as cohesive layers, which might be explained by the growth of biofilm among particulate material. Although current models have successfully explained sediment mobilization during flushing, the prediction of material accumulation and its shear strength is more challenging due to the lack of a comprehensive understanding about the accumulation process. The aim of this paper is to examine how particulate iron oxide that are rapidly deposited on PVC pipes develop variable shear strength under common hydraulic conditions found in drinking water distribution networks. A set of experiments were performed in a full-scale laboratory facility, where selected iron oxide particles were controlled and used to amend the feed water at the entrance of a 200 m pipe loop during a short period of time to create a suspended sediment plume with constant concentration. Experiments were realized at three different concentrations and three different velocities. In each set, three sequential plumes were used to accumulate particles on the pipe walls, followed by three sequential flushing steps used to mobilize the particulate material. The deposition of iron oxides in the PVC pipes were assessed indirectly through suspended sediment concentration (SSC) and turbidity data. Results showed that iron oxide particles predominantly accumulated in the first sections of the pipe wall. Most sediments were found to have weak shear strength and were easily mobilized with the first flushing step. However, the mobilized load from the second and third flushing steps revealed a consistent mobilization of sediment with higher shear strengths. These shear strengths were higher in the experiments with a higher inoculation concentration, and they were lower in experiments performed with a higher conditioning fluid velocity. The results suggest that variable shear strength can develop without biofilm. Additional long-term experiments are still required to evaluate the evolution of sediment shear strength which possibly can increase with time.
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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 | 0,001 | 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) | 0,000 | 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 ».