Study on ammonia generation from digested sludge by subcritical water treatment. (20th January 2023)

• Record Type: Journal Article
• Authors: Kato, Takahiro; Kojima, K.; Sumikura, M.; Kuroiwa, Y.
• Is Part Of: Water science and technology. Volume 87:Number 3(2023)
• Page Start: 614
• Page End: 619
• Publication Date: 2023-01-20
• Subjects: ammonification -- high temperature and pressure treatment -- oxidation treatment -- pyrolysis treatment -- sewage sludge -- sludge decomposition; Water -- Pollution; Sewage -- Purification; Water quality management; Periodicals; 628.168
• DOI: 10.2166/wst.2023.015
• Languages: English
• ISSNs: 0273-1223

Abstract

Abstract: Organic sludge has recently attracted attention as a renewable energy source. While the organic matter contained in sludge can be utilized as various renewable energy sources, its nitrogen component has limited use. In this study, subcritical water treatment was conducted to recover ammonia from digested sludge. While ammonia recovered via stripping is limited to soluble components, subcritical water treatment can convert solid components and dissolved organic nitrogen sludge into ammonia. Digested sludge was treated at several reaction temperatures, reaction pressures, treatment times, and oxygen ratios to determine the ammonia generation rate. Among the conditions tested in this study, an ammonium generation rate of 84.0% was obtained at 400 °C, 10 MPa, a treatment time of 5 min, and at an oxygen ratio of 1.2. HIGHLIGHTS: Subcritical water treatment efficiently converts nitrogen in digested sludge into ammonia. Under 400 °C, 10 MPa, 5 min, and an oxygen ratio of 1.2, ammonia was produced for 84.0% of total nitrogen. Subcritical water treatment can recover more nitrogen components as ammonia compared to ammonia stripping. This is because solid nitrogen and dissolved organic nitrogen can also be converted into ammonia by this method.