芦苇碳源-表面流人工湿地对农田退水脱氮的长期效能研究

针对农田退水NO₃^--N占比高、C/N低，氮污染难以去除的问题，将经济易得的芦苇(Phragmites australis)茎叶碎段装填在表面流人工湿地(packed surface flow construct wetland，PSFW)的表层作为外加碳源，以研究其长期运行情况下的脱氮效能。结果表明：第29~149天，外加芦苇茎叶碎段的PSFW的脱氮效能明显高于无芦苇茎叶碎段的空白PSFW₀；进水NO₃^--N和TN浓度分别为(16.4±1.0)和(17.7±2.0)mg/L，HRT按3、4和2 d运行时，HRT为4 d时脱氮效能最优，PSFW对NO₃^--N和TN去除率分别为(87.4±6.0)%和(74.1±6.0)%，PSFW₀去除率仅为(14.4±4.0)%和(14.4±3.0)%；第150~269天，PSFW的脱氮效能稍高于PSFW₀，在进水NO₃^--N和TN浓度分别为(10.4±1.0)和(10.8±1.0)mg/L，HRT按3、2和1 d运行时，HRT为3 d时脱氮效能最优，PSFW对NO₃^--N和TN的去除率分别为(91.9±7.0)%和(90.2±7.0)%，PSFW₀去除率分别为(91.3±5.0)%和(86.4±6.0)%。第270~334天，PSFW的脱氮效能稍低于PSFW₀；进水NO₃^--N和TN浓度分别为(5.7±0.4)和(7.2±0.8)mg/L，HRT为3 d时，PSFW对NO₃^--N和TN的去除率分别为(88.6±10.0)%和(82.5±7.0)%，PSFW₀去除率分别为(94.0±6.0)%和(87.8±3.0)%。

The Long-term Nitrogen Removal Efficiency from Agricultural Runoff in Phragmites Australis Packed Surface Flow Constructed Wetland

The low C/N ratio and high nitrate proportion characteristics of agricultural runoff makes its nitrate removal difficult. To resolve such problem, the economically and easily obtained Phragmites australis stems and leaves were applied and packed in the surface layer of the surface flow constructed wetland (PSFW) as external carbon sources to study the long-term nitrogen removal from agricultural runoff. Compared with control PSFW0, obviously higher nitrate removal efficiency was observed in Phragmites australis packed PSFW during 29-149 d operation. When the influent NO3--N and TN were (16.4±1.0) mg/L and (17.7±2.0) mg/L and the HRTs were 2 d, 3 d and 4 d, the highest nitrogen removal efficiency was achieved under 4 d HRT condition, and the NO3--N and TN removal efficiency in PSFW were (87.4±6.0)% and (74.1%±6.0)%. Those removal in PSFW0 were (14.4±4.0)% and (14.4±3.0)% respectively. Slight higher denitrification efficiency was obtained in PSFW than that in PSFW0 during 150-269 d operation. When the influent NO3--N and TN were (10.4±1.0) mg/L and (10.8±1.0) mg/L and the HRTs were 3 d, 2d and 1d, the highest nitrogen removal efficiency was achieved under 3d HRT condition, and the NO3--N and TN removal efficiency in PSFW were (91.9±7.0)% and (90.2±7.0)%. Those removal were (91.3±5.0)% and (86.4±6.0)% in PSFW0 accordingly. Slight lower denitrification efficiency was obtained in PSFW than that in PSFW0 during 270-334 d operation. When the influent NO3--N and TN were (5.7±0.4) mg/L and (7.2±0.8) mg/L and the HRT was 3 d, the NO3--N and TN removal efficiency in PSFW were (88.6±10.0)% and (82.5±7.0)%. Those removal were (94.0±6.0)%和(87.8±3.0)% in PSFW0 accordingly.