Regrowth of bacterial pathogen indicators in electro- dewatered biosolids
Notice bibliographique
Résumé
Land application of biosolids from activated sludge wastewater treatment plant (WWTP) is an attractive disposal solution. However, to be land applied in the US and Canada, biosolids need to meet specific pathogen loads regulations at the time of land application (i.e., not immediately after treatment). This study examined bacterial regrowth potential after electro-dewatering of biosolids. During a 8-min typical electro-dewatering treatment performed in the laboratory or a control heat treatment, Escherichia coli and fecal coliform (FC) counts were reduced to below the detection limit. After treatment, the extent of E. coli and FC regrowth was assessed by incubating the biosolids in aerobic or anaerobic conditions. After aerobic incubation, FC and E. coli counts stabilized between 107-109 MPN/g-dry solids in all biosolids samples irrespective of treatments (electro-dewatering, heat-treatment and no treatment) despite different levels of pH and dryness. Total aerobic counts also stabilized between 107-109 CFU/g-dry solids after four days of incubation. Finally, stable FC and E. coli counts at the end of incubation of samples prepared by belt filter press during winter were 1 log lower than in samples prepared by centrifuge press during the summer. Although similar trends about the effects of dewatering processes were reported in the literature, it is not be possible to conclude because seasonal factors are confounded with process factors. After anaerobic incubation, E. coli and FC counts in electro-dewatered biosolids stabilized 1 log lower than their respective counts in heat-treated or not treated biosolids (107-108 vs 108-109 MPN/g-dry solids, respectively). This difference was not changed when electro-dewatering filtrate was added back into the electro-dewatered biosolids. At WWTP, biosolids are typically stored as large piles. It is therefore likely that a major portion of piles is anaerobic, and that storage (hence regrowth) takes place under anaerobic condition. This study suggests that the electro-dewatered biosolids would exhibit a lower level of regrowth than other biosolids. Microbial counts observed in this study would not allow land application of these biosolids after 7-day storage because the lowest counts observed for electro-dewatered biosolids under anaerobic conditions were just above the requirements for the US-EPA Class B (FC counts above106 MPN/g-dry solids). However, these results suggest that this technology could be improved such that biosolids could meet land application regulations even after extended storage periods.
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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 | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| 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 ».