Digested Sludge Quality in Mesophilic, Thermophilic and Temperature-Phased Anaerobic Digestion Systems
Anaerobic digestion (AD) technology is commonly used to treat sewage sludge from activated sludge systems, meanwhile alleviating the energy demand (and costs) for wastewater treatment. Most often, anaerobic digestion is run in single-stage systems under mesophilic conditions, as this temperature reg...
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MDPI AG
2021-10-01
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| Online Access: | https://www.mdpi.com/2073-4441/13/20/2839 |
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| author | Iryna Lanko Jakub Hejnic Jana Říhová-Ambrožová Ivet Ferrer Pavel Jenicek |
| author_facet | Iryna Lanko Jakub Hejnic Jana Říhová-Ambrožová Ivet Ferrer Pavel Jenicek |
| author_sort | Iryna Lanko |
| collection | DOAJ |
| description | Anaerobic digestion (AD) technology is commonly used to treat sewage sludge from activated sludge systems, meanwhile alleviating the energy demand (and costs) for wastewater treatment. Most often, anaerobic digestion is run in single-stage systems under mesophilic conditions, as this temperature regime is considered to be more stable than the thermophilic one. However, it is known that thermophilic conditions are advantageous over mesophilic ones in terms of methane production and digestate hygienisation, while it is unclear which one is better concerning the digestate dewaterability. Temperature-phased anaerobic digestion (TPAD) is a double-stage AD process that combines the above-mentioned temperature regimes, by operating a thermophilic digester followed by a mesophilic one. The aim of this study is to compare the digestate quality of single-stage mesophilic and thermophilic AD and TPAD systems, in terms of the dewaterability, pathogenic safety and lower calorific value (LCV) and, based on the comparison, consider digested sludge final disposal alternatives. The research is conducted in lab-scale reactors treating waste-activated sludge. The dewaterability is tested by two methods, namely, centrifugation and mechanical pressing. The experimental results show that the TPAD system is the most beneficial in terms of organic matter degradation efficiency (32.4% against 27.2 for TAD and 26.0 for MAD), producing a digestate with a high dewaterability (8.1–9.8% worse than for TAD and 6.2–12.0% better than for MAD) and pathogenic safety (coliforms and <i>Escherichia coli</i> were not detected, and <i>Clostridium perfringens</i> were counted up to 4.8–4.9 × 10<sup>3</sup>, when for TAD it was only 1.4–2.5 × 10<sup>3</sup>, and for MAD it was 1.3–1.8 × 10<sup>4</sup>), with the lowest LCV (19.2% against 15.4% and 15.8% under thermophilic and mesophilic conditions, respectively). Regarding the final disposal, the digested sludge after TAD can be applied directly in agriculture; after TPAD, it can be used as a fertilizer only in the case where the fermenter HRT assures the pathogenic safety. The MAD digestate is the best for being used as a fuel preserving a higher portion of organic matter, not transforming into biogas during AD. |
| first_indexed | 2024-03-10T06:08:16Z |
| format | Article |
| id | doaj.art-3165159cd8e045c4a40dfb566661c66d |
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| last_indexed | 2024-03-10T06:08:16Z |
| publishDate | 2021-10-01 |
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| spelling | doaj.art-3165159cd8e045c4a40dfb566661c66d2023-11-22T20:21:34ZengMDPI AGWater2073-44412021-10-011320283910.3390/w13202839Digested Sludge Quality in Mesophilic, Thermophilic and Temperature-Phased Anaerobic Digestion SystemsIryna Lanko0Jakub Hejnic1Jana Říhová-Ambrožová2Ivet Ferrer3Pavel Jenicek4Department of Water Technology and Environmental Engineering, University of Chemistry and Technology, Technicka, 5, 166 28 Prague, Czech RepublicDepartment of Water Technology and Environmental Engineering, University of Chemistry and Technology, Technicka, 5, 166 28 Prague, Czech RepublicDepartment of Water Technology and Environmental Engineering, University of Chemistry and Technology, Technicka, 5, 166 28 Prague, Czech RepublicGEMMA—Group of Environmental Engineering and Microbiology, Department of Civil and Environmental Engineering, Universitat Politècnica de Catalunya·BarcelonaTech, c/Jordi Girona 1–3, Building D1, 08034 Barcelona, SpainDepartment of Water Technology and Environmental Engineering, University of Chemistry and Technology, Technicka, 5, 166 28 Prague, Czech RepublicAnaerobic digestion (AD) technology is commonly used to treat sewage sludge from activated sludge systems, meanwhile alleviating the energy demand (and costs) for wastewater treatment. Most often, anaerobic digestion is run in single-stage systems under mesophilic conditions, as this temperature regime is considered to be more stable than the thermophilic one. However, it is known that thermophilic conditions are advantageous over mesophilic ones in terms of methane production and digestate hygienisation, while it is unclear which one is better concerning the digestate dewaterability. Temperature-phased anaerobic digestion (TPAD) is a double-stage AD process that combines the above-mentioned temperature regimes, by operating a thermophilic digester followed by a mesophilic one. The aim of this study is to compare the digestate quality of single-stage mesophilic and thermophilic AD and TPAD systems, in terms of the dewaterability, pathogenic safety and lower calorific value (LCV) and, based on the comparison, consider digested sludge final disposal alternatives. The research is conducted in lab-scale reactors treating waste-activated sludge. The dewaterability is tested by two methods, namely, centrifugation and mechanical pressing. The experimental results show that the TPAD system is the most beneficial in terms of organic matter degradation efficiency (32.4% against 27.2 for TAD and 26.0 for MAD), producing a digestate with a high dewaterability (8.1–9.8% worse than for TAD and 6.2–12.0% better than for MAD) and pathogenic safety (coliforms and <i>Escherichia coli</i> were not detected, and <i>Clostridium perfringens</i> were counted up to 4.8–4.9 × 10<sup>3</sup>, when for TAD it was only 1.4–2.5 × 10<sup>3</sup>, and for MAD it was 1.3–1.8 × 10<sup>4</sup>), with the lowest LCV (19.2% against 15.4% and 15.8% under thermophilic and mesophilic conditions, respectively). Regarding the final disposal, the digested sludge after TAD can be applied directly in agriculture; after TPAD, it can be used as a fertilizer only in the case where the fermenter HRT assures the pathogenic safety. The MAD digestate is the best for being used as a fuel preserving a higher portion of organic matter, not transforming into biogas during AD.https://www.mdpi.com/2073-4441/13/20/2839mesophilicthermophilictemperature-phased anaerobic digestion (TPAD)dewaterabilitysludge qualitysludge valorisation |
| spellingShingle | Iryna Lanko Jakub Hejnic Jana Říhová-Ambrožová Ivet Ferrer Pavel Jenicek Digested Sludge Quality in Mesophilic, Thermophilic and Temperature-Phased Anaerobic Digestion Systems Water mesophilic thermophilic temperature-phased anaerobic digestion (TPAD) dewaterability sludge quality sludge valorisation |
| title | Digested Sludge Quality in Mesophilic, Thermophilic and Temperature-Phased Anaerobic Digestion Systems |
| title_full | Digested Sludge Quality in Mesophilic, Thermophilic and Temperature-Phased Anaerobic Digestion Systems |
| title_fullStr | Digested Sludge Quality in Mesophilic, Thermophilic and Temperature-Phased Anaerobic Digestion Systems |
| title_full_unstemmed | Digested Sludge Quality in Mesophilic, Thermophilic and Temperature-Phased Anaerobic Digestion Systems |
| title_short | Digested Sludge Quality in Mesophilic, Thermophilic and Temperature-Phased Anaerobic Digestion Systems |
| title_sort | digested sludge quality in mesophilic thermophilic and temperature phased anaerobic digestion systems |
| topic | mesophilic thermophilic temperature-phased anaerobic digestion (TPAD) dewaterability sludge quality sludge valorisation |
| url | https://www.mdpi.com/2073-4441/13/20/2839 |
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