Comparing the effects of Al-based coagulants in waste activated sludge anaerobic digestion: Methane yield, kinetics and sludge implications
Due to its effectiveness and ease of application, the process of flocculation and coagulation is often used for pollution removal in wastewater treatment. Most of these coagulants precipitate and accumulate in waste activated sludge (WAS), and could negatively affect sludge treatments, as observed f...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Elsevier
2024-04-01
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| Series: | Heliyon |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2405844024053131 |
| _version_ | 1797215926236479488 |
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| author | Francesco Pasciucco Erika Pasciucco Alessio Castagnoli Renato Iannelli Isabella Pecorini |
| author_facet | Francesco Pasciucco Erika Pasciucco Alessio Castagnoli Renato Iannelli Isabella Pecorini |
| author_sort | Francesco Pasciucco |
| collection | DOAJ |
| description | Due to its effectiveness and ease of application, the process of flocculation and coagulation is often used for pollution removal in wastewater treatment. Most of these coagulants precipitate and accumulate in waste activated sludge (WAS), and could negatively affect sludge treatments, as observed for anaerobic digestion. Nowadays, wastewater treatment plants (WWTPs) are widely discussed because of the current paradigm shift from linear to circular economy, and the treatments performed at the facility should be planned to avoid or reduce adverse effects on other processes. The aim of this study was to compare the impact of poly aluminum chloride (PAC) and aluminum sulfate (AS) on WAS anaerobic digestion, by feeding replicate serum reactors with different levels of coagulant (5, 10 and 20 mg Al/g TS). Reactors without the addition of any coagulants represented the control group. Results revealed that Al-based coagulants inhibited methane production, which decreased as the coagulant addition increased. The inhibition was much more severe in AS-conditioned reactors, showing average reductions in methane yield from 14.4 to 31.7%, compared to the control (167.76 ± 1.88 mL CH4/g VS). Analytical analysis, FTIR and SEM investigations revealed that the addition of coagulants affected the initial conditions of the anaerobic reactors, penalizing the solubilization, hydrolysis and acidogenesis phases. Furthermore, the massive formation of H2S in AS-conditioned reactors played a key role in the suppression of methane phase. On the other hand, the use of coagulant can promote the accumulation and recovery of nutrient in WAS, especially in terms of phosphorus. Our findings will expand research knowledge in this field and guide stakeholders in the choice of coagulants at full scale plant. Future research should focus on reducing the effect of coagulants on methane production by modifying or testing new types of flocculants. |
| first_indexed | 2024-04-24T11:37:49Z |
| format | Article |
| id | doaj.art-e991c17c309f4dbdbd45c7902a5182dd |
| institution | Directory Open Access Journal |
| issn | 2405-8440 |
| language | English |
| last_indexed | 2024-04-24T11:37:49Z |
| publishDate | 2024-04-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Heliyon |
| spelling | doaj.art-e991c17c309f4dbdbd45c7902a5182dd2024-04-10T04:29:18ZengElsevierHeliyon2405-84402024-04-01107e29282Comparing the effects of Al-based coagulants in waste activated sludge anaerobic digestion: Methane yield, kinetics and sludge implicationsFrancesco Pasciucco0Erika Pasciucco1Alessio Castagnoli2Renato Iannelli3Isabella Pecorini4Department of Energy, Systems, Territory and Construction Engineering (DESTEC), University of Pisa, 56122, Pisa, ItalyDepartment of Energy, Systems, Territory and Construction Engineering (DESTEC), University of Pisa, 56122, Pisa, ItalyDepartment of Energy, Systems, Territory and Construction Engineering (DESTEC), University of Pisa, 56122, Pisa, ItalyDepartment of Energy, Systems, Territory and Construction Engineering (DESTEC), University of Pisa, 56122, Pisa, ItalyCorresponding author.; Department of Energy, Systems, Territory and Construction Engineering (DESTEC), University of Pisa, 56122, Pisa, ItalyDue to its effectiveness and ease of application, the process of flocculation and coagulation is often used for pollution removal in wastewater treatment. Most of these coagulants precipitate and accumulate in waste activated sludge (WAS), and could negatively affect sludge treatments, as observed for anaerobic digestion. Nowadays, wastewater treatment plants (WWTPs) are widely discussed because of the current paradigm shift from linear to circular economy, and the treatments performed at the facility should be planned to avoid or reduce adverse effects on other processes. The aim of this study was to compare the impact of poly aluminum chloride (PAC) and aluminum sulfate (AS) on WAS anaerobic digestion, by feeding replicate serum reactors with different levels of coagulant (5, 10 and 20 mg Al/g TS). Reactors without the addition of any coagulants represented the control group. Results revealed that Al-based coagulants inhibited methane production, which decreased as the coagulant addition increased. The inhibition was much more severe in AS-conditioned reactors, showing average reductions in methane yield from 14.4 to 31.7%, compared to the control (167.76 ± 1.88 mL CH4/g VS). Analytical analysis, FTIR and SEM investigations revealed that the addition of coagulants affected the initial conditions of the anaerobic reactors, penalizing the solubilization, hydrolysis and acidogenesis phases. Furthermore, the massive formation of H2S in AS-conditioned reactors played a key role in the suppression of methane phase. On the other hand, the use of coagulant can promote the accumulation and recovery of nutrient in WAS, especially in terms of phosphorus. Our findings will expand research knowledge in this field and guide stakeholders in the choice of coagulants at full scale plant. Future research should focus on reducing the effect of coagulants on methane production by modifying or testing new types of flocculants.http://www.sciencedirect.com/science/article/pii/S2405844024053131Anaerobic digestionWaste activated sludgeMethane productionPoly aluminum chlorideAluminum sulfateCoagulants |
| spellingShingle | Francesco Pasciucco Erika Pasciucco Alessio Castagnoli Renato Iannelli Isabella Pecorini Comparing the effects of Al-based coagulants in waste activated sludge anaerobic digestion: Methane yield, kinetics and sludge implications Heliyon Anaerobic digestion Waste activated sludge Methane production Poly aluminum chloride Aluminum sulfate Coagulants |
| title | Comparing the effects of Al-based coagulants in waste activated sludge anaerobic digestion: Methane yield, kinetics and sludge implications |
| title_full | Comparing the effects of Al-based coagulants in waste activated sludge anaerobic digestion: Methane yield, kinetics and sludge implications |
| title_fullStr | Comparing the effects of Al-based coagulants in waste activated sludge anaerobic digestion: Methane yield, kinetics and sludge implications |
| title_full_unstemmed | Comparing the effects of Al-based coagulants in waste activated sludge anaerobic digestion: Methane yield, kinetics and sludge implications |
| title_short | Comparing the effects of Al-based coagulants in waste activated sludge anaerobic digestion: Methane yield, kinetics and sludge implications |
| title_sort | comparing the effects of al based coagulants in waste activated sludge anaerobic digestion methane yield kinetics and sludge implications |
| topic | Anaerobic digestion Waste activated sludge Methane production Poly aluminum chloride Aluminum sulfate Coagulants |
| url | http://www.sciencedirect.com/science/article/pii/S2405844024053131 |
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