Abstract:The oxygen transfer rate (OTR) and removal of organics, nitrogen, phosphorus in a naturally-ventilated constructed wetland (CWNV) installed with an air duct system at different wind speed (u≤4.0 m·s?1) was systematically investigated. Results showed that the external air could effectively diffuse and dissolve into the wetland interior through the bores on air ducts. Compared to a non-ventilated CW (CW0), OTR in CWNV (61.38~78.30 g·(m3·d)?1) increased by 19.3%~33.5%, and thus the processes of ammonification, nitrification and aerobic degradation of organics in CWNV were enhanced. The removal loads of NH3-N and COD in CWNV were 2.84~4.57 g·(m3·d)?1 and 45.0~56.6 g·(m3·d)?1, respectively, they were higher than those in CW0 by 90.5%~119.6% and 11.9%~23.2%, respectively. The effluent nitrate concentration was 1.10~10.39 mg·L?1 in CWNV, while it was only 0.41~0.91 mg·L?1 in CW0. Under moderate wind speed conditions, aerobic and anoxic/anaerobic zones simultaneously existed in CWNV, which was beneficial to both nitrification and denitrification, so that higher TN removal occurred than CW0. When the wind speed was ≤1.0 m·s?1, the TN removal load in CWNV was 6.70~6.77 g·(m3·d)?1 with 17.2%~23.1% higher than that in CW0. However, the improvement in TP removal efficiency through natural ventilation was limited with only 2.4%~4.8%. The relationships between wind speed and OTR, removal loads or degradation rate constants of COD, NH3-N and TN in CWNV conformed to quadratic equations. Key words:constructed wetland/ natural ventilation/ nitrogen/ oxygen transfer/ organics/ phosphorus.
图1人工湿地系统实验装置示意图 Figure1.Schematic diagram of the lab-scale CW systems
表1在不同风速条件下CW0和CWNV系统中氧传质速率 Table1.Oxygen transfer rate in CW0 and CWNV at different wind speed
湿地系统
不同风速下的氧传质速率/(g·(m3·d)?1)
0 m·s?1
1 m·s?1
2 m·s?1
3 m·s?1
4 m·s?1
CW0系统
51.44±0.60
53.60±0.99
55.78±0.76
56.45±0.91
59.14±0.82
CWNV系统
61.38±1.15
67.39±0.88
72.75±0.92
75.35±0.42
78.30±0.71
湿地系统
不同风速下的氧传质速率/(g·(m3·d)?1)
0 m·s?1
1 m·s?1
2 m·s?1
3 m·s?1
4 m·s?1
CW0系统
51.44±0.60
53.60±0.99
55.78±0.76
56.45±0.91
59.14±0.82
CWNV系统
61.38±1.15
67.39±0.88
72.75±0.92
75.35±0.42
78.30±0.71
下载: 导出CSV 表2风速与CWNV中氧传质速率、污染物(COD、NH3-N、TN)去除效果关系模型验证(n=3) Table2.Model verification of the relationship between wind speed and oxygen transfer rate, removal of COD, NH3-N and TN in CWNV (n=3)
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Key Laboratory of Clean Energy Utilization and Pollutant Control in Tianjin, School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401, China Received Date: 2020-09-29 Accepted Date: 2020-12-30 Available Online: 2021-04-23 Keywords:constructed wetland/ natural ventilation/ nitrogen/ oxygen transfer/ organics/ phosphorus Abstract:The oxygen transfer rate (OTR) and removal of organics, nitrogen, phosphorus in a naturally-ventilated constructed wetland (CWNV) installed with an air duct system at different wind speed (u≤4.0 m·s?1) was systematically investigated. Results showed that the external air could effectively diffuse and dissolve into the wetland interior through the bores on air ducts. Compared to a non-ventilated CW (CW0), OTR in CWNV (61.38~78.30 g·(m3·d)?1) increased by 19.3%~33.5%, and thus the processes of ammonification, nitrification and aerobic degradation of organics in CWNV were enhanced. The removal loads of NH3-N and COD in CWNV were 2.84~4.57 g·(m3·d)?1 and 45.0~56.6 g·(m3·d)?1, respectively, they were higher than those in CW0 by 90.5%~119.6% and 11.9%~23.2%, respectively. The effluent nitrate concentration was 1.10~10.39 mg·L?1 in CWNV, while it was only 0.41~0.91 mg·L?1 in CW0. Under moderate wind speed conditions, aerobic and anoxic/anaerobic zones simultaneously existed in CWNV, which was beneficial to both nitrification and denitrification, so that higher TN removal occurred than CW0. When the wind speed was ≤1.0 m·s?1, the TN removal load in CWNV was 6.70~6.77 g·(m3·d)?1 with 17.2%~23.1% higher than that in CW0. However, the improvement in TP removal efficiency through natural ventilation was limited with only 2.4%~4.8%. The relationships between wind speed and OTR, removal loads or degradation rate constants of COD, NH3-N and TN in CWNV conformed to quadratic equations.
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