| Title | Anaerobic-aerobic sequential treatment: Temperature optimization and cost implications |
| Abstract | Traditionally, aeration units, used as a polishing stage after anaerobic digestion (AD) of wastes, are operated at ambient temperature. Yet, when effluent quality is the main design criterion, raising the temperature of the aeration stage can be justified by improved removal efficiencies. In this study, an anaerobic-aerobic sequential system (AASS) was operated to co-digest raw wastewater and food waste. The aerobic compartment was tested under psychrophilic and mesophilic temperatures. At the design loading rate of 2 g L d, the anaerobic digester achieved removal efficiencies of 85 ± 2% of volatile solids (VS), 84 ± 3% of total chemical oxygen demand (COD) and a biogas yield of 1,035 ± 30 mL g (50% methane). The aerobic reactor achieved additional removal of 8% COD and 7 % VS. By raising the temperature of the aerobic reactor to the mesophilic range, COD and solids concentrations of the effluent dropped to approximately half their values. This was accompanied by an increase in nitrification (from 68% to 91%) and denitrification (from 10% to 16%). The energy analysis showed that total energy consumption slightly increases (from 0.45 to 0.49 kWh kg) by raising the temperature of the aerobic reactor to mesophilic range. A preliminary evaluation of the sludge disposal cost, revealed a saving increase of 5-6% under mesophilic operation with respect to psychrophilic conditions. Implications: In order to cope with the globally increasing constraints on the disposal of urban wastes, efficient post-processing of effluents becomes a crucial requirement for the anaerobic digestion industry. In this context, the submitted manuscript shows that the quality of the effluent, of an anaerobic digester, treating food waste with raw wastewater, can be substantially improved by optimizing the aerobic polishing stage. Raising the temperature of the aerobic reactor to the mesophilic range resulted in a drop of solids and COD concentrations to approximately half their values. Equally important, the implications on operational costs were found to be favorable, compared to traditional psychrophilic aerobic post-treatment, when taking into consideration indirect sludge treatment costs and energy selling revenues. |
| Source | Journal of the Air & Waste Management Association (1995) 69 (10), pp. 1170–1181 |
| Keywords | Anaerobic-aerobic sequential systemfood wastewastewatermesophilic aerobic digestionpsychrophilic aerobic digestionenergy balance |
| Journal | Journal of the Air & Waste Management Association (1995) |
| Editor | Air and Waste Management Association,, Pittsburgh, PA, Stati Uniti d'America |
| Year | 2019 |
| Type | Articolo in rivista |
| DOI | 10.1080/10962247.2019.1629361 |
| Authors | Ghanimeh S.; Abou Khalil C.; Mosca Angelucci D.; Tomei M.C. |
| Text | 420417 2019 10.1080/10962247.2019.1629361 Scopus 2 s2.0 85071329886 Anaerobic aerobic sequential system food waste wastewater mesophilic aerobic digestion psychrophilic aerobic digestion energy balance Anaerobic aerobic sequential treatment Temperature optimization and cost implications Ghanimeh S.; Abou Khalil C.; Mosca Angelucci D.; Tomei M.C. Department of Civil and Environmental Engineering, Notre Dame University Louaize, Zouk Mosbeh, Department of Civil and Environmental Engineering, Notre Dame University Louaize, Zouk Mosbeh, Lebanon, , Lebanon; Water Research Institute, C.N.R., Roma, Water Research Institute, Roma, C.N.R., Italy; Water Research Institute, C.N.R., Roma, Water Research Institute, Roma, C.N.R., Italy. Traditionally, aeration units, used as a polishing stage after anaerobic digestion AD of wastes, are operated at ambient temperature. Yet, when effluent quality is the main design criterion, raising the temperature of the aeration stage can be justified by improved removal efficiencies. In this study, an anaerobic aerobic sequential system AASS was operated to co digest raw wastewater and food waste. The aerobic compartment was tested under psychrophilic and mesophilic temperatures. At the design loading rate of 2 g L d, the anaerobic digester achieved removal efficiencies of 85 ± 2% of volatile solids VS , 84 ± 3% of total chemical oxygen demand COD and a biogas yield of 1,035 ± 30 mL g 50% methane . The aerobic reactor achieved additional removal of 8% COD and 7 % VS. By raising the temperature of the aerobic reactor to the mesophilic range, COD and solids concentrations of the effluent dropped to approximately half their values. This was accompanied by an increase in nitrification from 68% to 91% and denitrification from 10% to 16% . The energy analysis showed that total energy consumption slightly increases from 0.45 to 0.49 kWh kg by raising the temperature of the aerobic reactor to mesophilic range. A preliminary evaluation of the sludge disposal cost, revealed a saving increase of 5 6% under mesophilic operation with respect to psychrophilic conditions. Implications In order to cope with the globally increasing constraints on the disposal of urban wastes, efficient post processing of effluents becomes a crucial requirement for the anaerobic digestion industry. In this context, the submitted manuscript shows that the quality of the effluent, of an anaerobic digester, treating food waste with raw wastewater, can be substantially improved by optimizing the aerobic polishing stage. Raising the temperature of the aerobic reactor to the mesophilic range resulted in a drop of solids and COD concentrations to approximately half their values. Equally important, the implications on operational costs were found to be favorable, compared to traditional psychrophilic aerobic post treatment, when taking into consideration indirect sludge treatment costs and energy selling revenues. 69 Published version http //www.scopus.com/record/display.url eid=2 s2.0 85071329886 origin=inward Articolo in rivista Air and Waste Management Association, 1096 2247 Journal of the Air Waste Management Association 1995 Journal of the Air Waste Management Association 1995 J. Air Waste Manage. Assoc. 1995 Journal of the Air Waste Management Association. 1995 Journal of the Air and Waste Management Association 1995 domenica.moscaangelucci MOSCA ANGELUCCI DOMENICA mariaconcetta.tomei TOMEI MARIA CONCETTA |
