Air side-stream ammonia stripping in a thin film evaporator coupled to high-solid anaerobic digestion of sewage sludge: Process performance and interactions. (1st October 2021)

• Record Type: Journal Article
• Authors: Di Capua, Francesco; Adani, Fabrizio; Pirozzi, Francesco; Esposito, Giovanni; Giordano, Andrea
• Is Part Of: Journal of environmental management. Volume 295(2021)
• Publication Date: 2021-10-01
• Subjects: Ammonia stripping -- Anaerobic digestion -- Circular economy -- Nutrient recovery -- Thin-film evaporator -- Sewage sludge; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2021.113075
• Languages: English
• ISSNs: 0301-4797

Abstract

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. Graphical abstract: Image 1 Highlights: A thin-film evaporator (TFE) is proposed for air side-stream ammonia stripping. TFE is suitable for ammonia control in high-solid sewage sludge anaerobic digesters. Airflow rate had a greater impact on ammonia stripping than temperature and %CO2 . Ammonia removal was controlled by concomitant CO2 stripping in the TFE. High-solid anaerobic digestion was not negatively impacted by air as a strip gas.