Balancing hygienization and anaerobic digestion of raw sewage sludge
The anaerobic digestion of raw sewage sludge was evaluated in terms of process efficiency and sludge hygienization. Four different scenarios were analyzed, i.e. mesophilic anaerobic digestion, thermophilic anaerobic digestion and mesophilic anaerobic digestion followed by a 60 °C or by an 80 °C hygi...
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Veröffentlicht in: | Water research (Oxford) 2012-12, Vol.46 (19), p.6218-6227 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | The anaerobic digestion of raw sewage sludge was evaluated in terms of process efficiency and sludge hygienization. Four different scenarios were analyzed, i.e. mesophilic anaerobic digestion, thermophilic anaerobic digestion and mesophilic anaerobic digestion followed by a 60 °C or by an 80 °C hygienization treatment. Digester performance (organic matter removal, process stability and biogas yield) and the hygienization efficiency (reduction of Escherichia coli, somatic coliphages and F-specific RNA phages) were the main examined factors. Moreover, a preliminary economical feasibility study of each option was carried out throughout an energy balance (heat and electricity). The obtained results showed that both thermophilic anaerobic digestion and mesophilic anaerobic digestion followed by a hygienization step were able to produce an effluent sludge that fulfills the American and the European legislation for land application. However, higher removal efficiencies of indicators were obtained when a hygienization post-treatment was present. Regarding the energy balance, it should be noted that all scenarios have a significant energy surplus. Particularly, positive heat balances will be obtained for the thermophilic anaerobic digestion and for the mesophilic anaerobic digestion followed by 60 °C hygienization post-treatment if an additional fresh-sludge/digested sludge heat exchanger is installed for energy recovery.
► Evaluation of the process performance, hygienization efficiency and dewaterability. ► Mesophilic digestion plus pasteurization showed higher viral indicators removal. ► Somatic coliphages look very promising to evaluate thermal treatments of sludges. ► A heat exchanger can led to positive heat balances in a hygienization treatment. |
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ISSN: | 0043-1354 1879-2448 |
DOI: | 10.1016/j.watres.2012.07.035 |