Impact of water level fluctuation on nitrogen removal in horizontal subsurface flow constructed wetlands
GUO Shi-lin1,2, YE Chun2, LI Chun-hua2, XU Shi-hong1, LÜ Mei-ting2
1. Environmental Science and Engineering College, Donghua University, Shanghai 201620, China;
2. State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
By building simulation devices of horizontal subsurface flow constructed wetlands, four wetlands (CW1、CW2、CW3、CW4) with the frequency of water-level fluctuation as 0,3,6,9cm/d were set up to study the impact of water-level change on nitrogen removal in them. The results showed that water-level change could improve the effect of nitrogen removal. The average concentration of dissolved oxygen was (0.99±0.20), (1.14±0.19), (1.30±0.27) and (1.34±0.27) mg/L, for CW1, CW2, CW3, CW4 respectively. The average concentrations of dissolved oxygen in the above four wetlands had significant differences(P<0.05),and they increased with the frequency increasing. Characterization value of nitrification intensity had the same thend with dissolved oxygen. And it gradually decreased along the inlet to outlet of wetlands, but the upper layer was greater than the lower layer in the depth direction. Characterization value of denitrification intensity increased with the frequency decrease and it increased first then decreased along the wetlands' inlets to outlet. TN average removal rates of four wetlands were (89.04±0.80)%, (91.04±1.14)%, (93.94±1.23)% and (91.45±1.11)% respectively. The TN removal rate of CW3 wetland was the highest and had significant differences (P<0.05) with others. The CW3and CW4 wetlands had better efficient for NH4+-N removal and the average removal rates were (93.79±1.19)% and (95.30±1.09)% respectively.
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