芦苇根际微环境对潜流人工湿地氮与COD去除性能的影响

构建了3个小型潜流人工湿地，一个不种植物作为对照；另2个栽种芦苇，其中一个湿地在芦苇根部埋设300目尼纶网制成的根袋，以区分根际与非根际环境.采用人工配水，研究了稳定运行期的人工湿地对COD、N的去除性能.结果表明，3个湿地对COD、N的去除场所主要位于湿地前端，且COD与N的去除具有沿程同步性.在进水C/N=5时，对照湿地、芦苇湿地和根袋湿地对NH⁺₄-N和TN的去除效率分别为66.2%、94.2%、82.2%和67.2%、90.7%、76.1%，具有同步硝化反硝化现象；对COD的去除效率分别为56.2%、80.9%、72.7%.试验中，3个湿地沿程水样的C/N值均大于5，表明碳源供应较充足.通过在湿地中预埋铂电极和土壤溶液采样器的方法，测定了根际土壤与非根际土体土壤ORP以及土壤溶液中的有机物含量（以TOC表征）.结果表明，湿地前端根际土壤ORP明显高于空白湿地和湿地土体土壤，差值分别为11～311 mV、62～261 mV.根系分泌物显著增加了植物湿地中有机碳的供应，根际土壤与非根际土体土壤中TOC含量分别为21.3～54.6 mg·L^-1和6.65～12.0 mg·L^-1.正是湿地植物根际环境中较高的氧化还原电位以及充足的碳源供应，使得植物湿地的脱氮效果好于对照湿地.

Effect of Reed Rhizosphere on Nitrogen and COD Removal Efficiency in Subsurface Flow Constructed Wetlands

Nitrogen removal efficiency was investigated in three subsurface flow constructed wetlands (CWs) with and without reed. Root bag made of nylon sieve with 300 mesh was used to enwrap the reed root in one of reed CWs to distinguish reed rhizosphere from non-rhizosphere. The CWs with root bag enwrapped reed root (hereinafter called as mesh CWs) and other CWs were fed with artificial ammonium-rich wastewater. The results indicated that the COD and N removal occurred mainly in the front of CWs, and C and nitrogen removal occurred concurrently along the stream way. When C/N ratio of influent was 5, the removal efficiencies of NH⁺₄-N in control CWs, reed CWs and mesh CWs were 66.2%, 94.2% and 82.2%, respectively. TN removal efficiencies were 67.2%, 90.7% and 76.1% respectively. Simultaneous nitrification and denitrification phenomenon in this study was also observed. The removal efficiency of organic carbon was different from nitrogen removal efficiency, mesh CWs showed the highest COD removal efficiency with 80.9%, while control CWs and reed CWs were 72.2% and 56.2%, respectively. C/N ratio of wastewater throughout the bed was more than 5 in three CWs, which indicated carbon source supply was enough for denitrification. The oxidation-reduction position (ORP) and concentration of total organic carbon in rhizosphere and non-rhizosphere were detected. The ORP in the front of mesh CWs's rhizosphere was much higher than that in control CWs and non-rhizosphere in mesh CWs, which were 11_311 mV and 62_261 mV, respectively. Root exudates also showed the difference between rhizosphere and non-rhizosphere in mesh CWs, the TOC of them were 21.3_54.6 mg·L^-1 and 6.65_12.0 mg·L^-1. Due to the higher ORP and concentration of TOC, the nitrogen removal efficiency in plant CWs was much higher than that in control CWs.