Increasing biosolids phosphorus fertilizer value and decreasing biogas carbon dioxide content for municipal wastewater treatment processes with anaerobic digestion
Notice bibliographique
Résumé
Municipal wastewater treatment by the City of Ottawa produces biosolids and biogas by-products from anaerobic digestion of sewage sludge. Some of these biosolids are distributed to selected farmlands. The biosolids contain a variety of low-solubility iron phosphate solids, which contribute to their low phosphorus (P) fertilizer value. Some of the biogas is used to produce electric power and heat at the plant. In this research, we investigated the potential to increase the biosolids P fertilizer value by using endogenous microbial activity and sulfur chemistry to dissolve iron phosphate, which can later be precipitated as higher-solubility calcium phosphate, and decrease the biogas carbon dioxide concentration by precipitating calcium carbonate. Precipitation of lower-solubility iron sulfide was examined for its potential to dissolve higher-solubility iron phosphate within biosolids and consequently increase the dissolved inorganic orthophosphate (o-Pi) concentration. Endogenous bacteria within the biosolids were hypothesized to generate sulfide from inexpensive elemental sulfur. Experiments were performed to test the effect of incubating 10 % biosolids with different molar ratios of elemental sulfur (S0) to total phosphorus (TP) (S/TP: 0 – 4) and times (24 h – 192 h) at different temperatures (22 °C, 32 °C, or 42 °C) on P dissolution. Experiments were conducted on five biosolids batches from different times of year. Dissolved TP concentration plateaued after an S/TP molar ratio of 0.5. For winter 2023 biosolids, higher dissolved TP was obtained for an incubation at 32 °C or 42 °C than at room temperature (22 °C). The maximum observed dissolved TP concentration was 7 % of the TP for winter 2023 biosolids incubated with 0.5 S/TP at 32 °C for 168 h. Summer 2024 biosolids yielded significantly lower TP concentrations at all temperatures than winter 2023 biosolids. The incubation temperature did not significantly affect the TP concentration. The different biosolids batch compositions were found to influence the P dissolution and the effect of temperature on P dissolution. Waste concrete fines and wollastonite (CaSiO3) were tested as potential inexpensive sources of soluble Ca and alkalinity for calcite precipitation of dissolved carbon dioxide in biogas. Both the waste concrete fines and wollastonite were leached with acetic acid. Experiments selected using design of experiments was used to assess the effect of percent solids, acetic acid concentration, and temperature on soluble calcium concentration in the leachates for both the waste concrete fines and wollastonite. The effect of percent solids and acetic acid concentration on the Ca extraction from the concrete fines and wollastonite was more significant than the effect of temperature. Calcium ion extraction was inversely proportional to pH for both wollastonite and calcined concrete. Leaching with 1.0 % solids and 100 mM acetic acid at 32 °C resulted in ~100 % calcium ion extraction for the concrete fines and ~20 % calcium ion extraction for wollastonite. The leachate for the concrete fines had a higher pH compared to that of the wollastonite. Endogenous microbial activity in biosolids can reduce elemental sulfur to sulfide, precipitate iron sulfide, and dissolve a fraction of the range of iron phosphate solids in biosolids. Waste concrete was found to dissolve more calcium ions and alkalinity than wollastonite by acetic acid leaching under mild conditions, for carbon capture from biogas. Combination of these two research findings presents an opportunity to reduce the carbon dioxide concentration in biogas, reduce carbon dioxide emissions, and increase the P-fertilizer value of biosolids produced by municipal wastewater treatment processes with anaerobic digestion, although the net energy cost remains to be ascertained
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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) | 0,001 | 0,001 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,000 | 0,001 |
| 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 ».