砾石床湿地系统对氮去除率影响的研究

The Influention on the Nitrogen Removal for Gravel Bed Wetland System

为探究砾石床湿地系统对氮去除的影响,设计茭草床和芦苇床湿地系统以研究对氮去除的影响因素。结果表明HRT增加至2 d,TN和NO_3--N的去除率增加,而NH_4+^-N的去除率无变化。保持HRT为1 d,温度由22℃降低至10.6℃时,NO_3^--N的去除率明显下降,而NH_4^+-N的去除率变化不大。投加50 mg/L的葡萄糖补充碳源,湿地床沿程NO_3^--N逐渐降低、DO浓度降低1 mg/L,碱度的沿程变化幅度比未加碳源提高数倍。反硝化作用不仅需在碳源充足时进行,而且外加有机碳源可以显著强化反硝化过程。水力负荷为0.2~0.8 m^3/(m^2·d)时,茭草床TN负荷增加,出水浓度增加,进水浓度和出水浓度满足简单回归方程。分析TN去除途径,砾石床因吸附能力较好而具有较大的TN去除率,而茭白床和芦苇床湿地系统脱氮的最主要路径是微生物的反硝化作用,最高脱氮比例可达49%,其次是砾石吸附作用,而植物吸收脱氮作用最弱。

To research the influention on the nitrogen removal for gravel bed wetland system, the zizania latifolia and reed wetland system were designed to explore the influencing factors. Results showed that HRT increased to 2 d, the removal efficiency increased for TN and NO3--N while it had no change for NH4＇-N. When HRT was I d, temperature decreased from 22℃to 10.6 ℃, the NO3--N removal efficiency decreased clearly, but NI-h^-N kept unchanged nearly. Added 50 mg/L glucose to supply organic carbon resource, the NO3--N declined gradually and the DO concentration reduced 1 mg/L with the stream flowing in the wetland system, the amplitude of variation on alkalinity increased several times than that with no additional organic carbon resource, denitrification would require adequate carbon resource, and denitrification had enhanced obviously with organic carbon resource. When hydraulic load rate were 0.2-0.8 m3/（m·2d）, increased TN loading, the TN concentration for effluent increased, the TN concentration for inlet and outlet met the simple regression equation. Analyzed the TN removal path, the gravel bed had good removal efficiency owing to excellent absorption capacity, and the main TN removal path for zizania latifolia and reed bed wetland came from microorganism denitrification, the maximum proportion for denitfification was 49 %, and the second was absorption of gravel while the proportion uptaked by plants was the least.