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Updated: Nov 1, 2025
Continuously-stirred Anaerobic Digester to Convert Organic Wastes into Biogas: System Setup and Basic Operation
Published on: July 13, 2012
Air side-stream ammonia stripping in a thin film evaporator coupled to high-solid anaerobic digestion of sewage
Francesco Di Capua1, Fabrizio Adani2, Francesco Pirozzi3
1Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, Via Claudio 21, 80125, Naples, Italy; Department of Civil, Environmental, Land, Building Engineering and Chemistry, Polytechnic University of Bari, Via E. Orabona 4, 70125, Bari, Italy.
Abstract:
Air side-stream ammonia stripping in a thin-film evaporator (TFE) is proposed for the first time to control total ammonia nitrogen (TAN) concentration in a centralized full-scale plant performing high-solid anaerobic digestion (HSAD) of sewage sludge (SS). In this process, anaerobically digesting sludge (ADS) is continuously recirculated from the digester to the TFE unit where ammonia is stripped by an air stream. The stripped ammonia reacts with sulfuric acid in an absorption unit to produce ammonium sulfate. Overall, HSAD coupled to air side-stream ammonia stripping results in a twofold production of fertilizers (i.e. ammonium sulfate and SS digestate) recycling nutrients from organic wastes in agreement with the principles of circular economy. This study evaluates the influence of different operational airflow rates, temperatures and CO2 concentrations on air side-stream ammonia stripping in the TFE without alkali addition and the impact of air-based ammonia stripping on HSAD performance at full-scale. The study also investigates the chemistry and the interaction between the ammonia and carbonate subsystems of ADS and clarifies the stoichiometric relationship between ammonia and CO2 stripping.
