Numerical assessment of nitrogen removal from swine wastewater in activated sludge systems: Comparison between continuous and intermittent aeration

International audienceThe appropriate conditions needed to achieve nitrogen (N) removal from swine wastewater (SW) in an activated sludge continuous stirred-tank reactor (+settler) were assessed by performing numerical simulations. Air supply was considered through continuous or intermittent aeration (CA vs. IA), and several values were assumed for the SW BOD5-to-N ratio. By considering CA and low dissolved oxygen (DO) levels, feasibility for peforming N removal via nitrite through simultaneous nitrification–denitrification was confirmed. Nitrogen removal via nitrite was also the case when applying IA, even at higher DO ranges. The nitrite short-cut was shown to reduce energy consumption for aeration. However, regardless of the aeration method applied, sensitive DO controls will be required, particularly when the SW BOD5-to-N ratio takes low values. This study allowed to assess the operational conditions required when biologically treating SW to meet N standards and to identify situations in which a final post-treatment is needed before effluent discharge

Treatment of swine wastewater in continuous activated sludge systems under different dissolved oxygen conditions: Reactor operation and evaluation using modelling

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.Postprint (published version

Nitrogen removal from swine wastewater in activated sludge systems using an ASM for continuous and intermittent aeration

An ASM-type model considering BOD and N removal was implemented including nitrite as intermediate, free ammonia and free nitrous acid as potential inhibitors and temperature as process parameter during swine wastewater treatment. Simulations were performed at various conditions: continuous and intermittent aeration; influent swine wastewater BOD/N ratio of 2, 3 and 4. Under continuous aeration and low DO, N was mainly removed through the nitrite short cut in simultaneous nitrification-denitrification. Under intermittent aeration, N was removed at broader DO conditions during aeration than previously assessed for continuous aeration. In both aeration conditions, critical DO control was required to achieve satisfactory N removal, particularly when the BOD/N ratio of the wastewater was set at 2. This study assesses those conditions needed to meet the N effluent standards in AS swine wastewater treatment plants, and to identify those cases when post-treatment will be needed.Postprint (published version

Nitrogen removal from swine wastewater in activated sludge systems using an ASM for continuous and intermittent aeration

An ASM-type model considering BOD and N removal was implemented including nitrite as intermediate, free ammonia and free nitrous acid as potential inhibitors and temperature as process parameter during swine wastewater treatment. Simulations were performed at various conditions: continuous and intermittent aeration; influent swine wastewater BOD/N ratio of 2, 3 and 4. Under continuous aeration and low DO, N was mainly removed through the nitrite short cut in simultaneous nitrification-denitrification. Under intermittent aeration, N was removed at broader DO conditions during aeration than previously assessed for continuous aeration. In both aeration conditions, critical DO control was required to achieve satisfactory N removal, particularly when the BOD/N ratio of the wastewater was set at 2. This study assesses those conditions needed to meet the N effluent standards in AS swine wastewater treatment plants, and to identify those cases when post-treatment will be needed

Treatment of swine wastewater in continuous activated sludge systems under different dissolved oxygen conditions: Reactor operation and evaluation using modelling

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