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Updated: Jul 12, 2026

Continuously-stirred Anaerobic Digester to Convert Organic Wastes into Biogas: System Setup and Basic Operation
Published on: July 13, 2012
Treatment of swine wastewater in continuous activated sludge systems under different dissolved oxygen conditions:
Miyoko Waki1, Tomoko Yasuda2, Yasuyuki Fukumoto2
1National Agriculture and Food Research Organization (NARO), Institute of Livestock and Grassland Science, Animal Waste Management and Environment Research Division, 2 Ikenodai, Tsukuba, Ibaraki 305-0901, Japan; Irstea, UR OPAALE, 17 Avenue de Cucillé-CS 64427, F-35044 Rennes, France.
Abstract:
Swine wastewater was treated in two continuously aerated activated sludge (AS) systems at high (AS1: 1.7-2.6 mg/L) and low (AS2: 0.04-0.08 mg/L) dissolved oxygen (DO), and at three temperatures (10, 20, and 30 °C). Biochemical oxygen demand (BOD) removal was >94.8%. Meanwhile, total nitrogen (N) removal was significantly higher in AS2, at 64, 89, and 88%, than in AS1, at 12, 24, and 46%, for 10, 20, and 30 °C, respectively. The experimental data were considered in a simulation study using an AS model for BOD and N removal, which also included nitrite, free ammonia, free nitrous acid, and temperature. Simulations at high-DO showed that ammonium was partly oxidized into nitrate but not removed, whereas at low-DO ammonium was removed mainly through the nitrite shortcut in simultaneous nitrification-denitrification. This study demonstrates that treatment at low-DO is an effective method for removing N, and modelling a helpful tool for its optimization.
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