Microaerobic Digestion of Low-Biodegradable Sewage Sludge: Effect of Air Dosing in Batch Reactors

Raffaele Morello, Francesco Di Capua, Ludovico Pontoni, Stefano Papirio, Danilo Spasiano, Umberto Fratino, Francesco Pirozzi and Giovanni Esposito
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Raffaele Morello: Department of Civil, Environmental, Land, Building Engineering and Chemistry, Polytechnic University of Bari, Via E. Orabona 4, 70125 Bari, Italy
Francesco Di Capua: Department of Civil, Environmental, Land, Building Engineering and Chemistry, Polytechnic University of Bari, Via E. Orabona 4, 70125 Bari, Italy
Ludovico Pontoni: Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, Via Claudio 21, 80125 Naples, Italy
Stefano Papirio: Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, Via Claudio 21, 80125 Naples, Italy
Danilo Spasiano: Department of Civil, Environmental, Land, Building Engineering and Chemistry, Polytechnic University of Bari, Via E. Orabona 4, 70125 Bari, Italy
Umberto Fratino: Department of Civil, Environmental, Land, Building Engineering and Chemistry, Polytechnic University of Bari, Via E. Orabona 4, 70125 Bari, Italy
Francesco Pirozzi: Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, Via Claudio 21, 80125 Naples, Italy
Giovanni Esposito: Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, Via Claudio 21, 80125 Naples, Italy

Sustainability, 2021, vol. 13, issue 17, 1-11

Abstract: The adoption of prolonged solid retention times during the biological treatment of urban wastewaters is a well-known strategy to reduce sewage sludge production. However, it also results in the production of a biological sludge with low percentages of biodegradable organic matter, also characterized by high humification degrees, which may hamper the anaerobic digestion treatment aimed at sludge stabilization. To accelerate the hydrolytic stage, the application of microaerobic conditions during the anaerobic digestion of low-biodegradable sewage sludge was investigated in this study. In particular, six bio-methanation tests of a real sewage sludge were carried out, introducing air in the bioreactors with doses ranging between 0 and 16.83 L air/kg VS in d, in order to evaluate the air dosage that optimizes the biomethane production and organic matter degradation. Notably, the lower air loading rates investigated in this study, such as 0.68 and 1.37 L air/kg VS in d, led to an increase in methane production of up to 19%, due to a higher degradation of total lipids and proteins. In addition, these microaerobic conditions also resulted in a decrease in the sludge humification degree and in lower volatile fatty acid accumulation.

Keywords: microaeration; sewage sludge; anaerobic digestion; WWTP; methane production; biogas (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
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