Investigation of the Main Parameters Influencing the Kinetics of an Ammonia Stripping Plant Treating Swine Digestate

Alessandro Abbà, Marta Domini, Marco Baldi, Maria Cristina Collivignarelli () and Giorgio Bertanza
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Alessandro Abbà: Department of Civil, Environmental, Architectural Engineering and Mathematics, University of Brescia, Via Branze 43, 25123 Brescia, Italy
Marta Domini: Department of Civil, Environmental, Architectural Engineering and Mathematics, University of Brescia, Via Branze 43, 25123 Brescia, Italy
Marco Baldi: Department of Chemistry, University of Pavia, Viale Taramelli 12, 27100 Pavia, Italy
Maria Cristina Collivignarelli: Department of Civil Engineering and Architecture, University of Pavia, Via Ferrata 3, 27100 Pavia, Italy
Giorgio Bertanza: Department of Civil, Environmental, Architectural Engineering and Mathematics, University of Brescia, Via Branze 43, 25123 Brescia, Italy

Sustainability, 2023, vol. 15, issue 13, 1-14

Abstract: Ammonia stripping is a consolidated technology that can be adopted to reduce the excessive content of nitrogen in the digestate, thus allowing its reuse as fertilizer within the maximum nitrogen loads set by regulations. In this work, the role of the main operational parameters (airflow and temperature) was assessed on a pilot bubble reactor treating a swine-based digestate, under batch conditions. A kinetic model was developed to correlate temperature, airflow and the ammonia removal yield. Varying the temperature from 60 to 70 °C and the airflow rate from 30 to 60 m 3 air h −1 m −3 digestate , the performance of the plant was measured at different reaction times. The process was favored by the spontaneous pH increase over 10, without basifying agent addition. The lowest removal efficiency (50%) was recorded at 60 °C and 30 m 3 air h −1 m −3 digestate . A removal efficiency higher than 80% was reached running the process at 70 °C and 45 or 60 m 3 air h −1 m −3 digestate. Performance curves were than developed as a practical tool to identify the operating conditions leading to a desired nitrogen removal rate: for instance, under the most severe conditions, up to 80% ammoniacal nitrogen could be removed in about 10 h. Though the obtained results are valid for the treated digestate, the experimental methodology as well as the mathematical model could be replicated in other case studies, thus allowing the amelioration of the process operation.

Keywords: ammonia stripping reactor; anaerobic digestion; nitrogen removal; livestock manure; performance curves (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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