潜流人工湿地负荷变化对脱氮效果的影响研究

通过15个月的现场监测试验,研究了约40种入水负荷下人工湿地的脱氮效果,总结了芦苇、茭草、混合种植以及无植物潜流湿地在不同水力负荷和污染负荷下的单位面积出水氮负荷和去除率的变化规律.4种潜流系统入水负荷从400mg·(m²·d)^-1变化到8 000 mg·(m²·d)^-1,出水负荷小于7 000 mg·(m²·d)^-1,研究表明,潜流湿地出水负荷随着入水负荷的升高而升高,具有明显的线性相关关系.单位面积总氮的去除率在低负荷条件下随入水负荷的升高而升高,但在高负荷时单位面积去除率基本维持在一定的水平,不受入水负荷的影响,去除率变化波动较大.各系统的最佳运行范围在2 000～4 000mg·(m²·d)^-1之间,平均去除率在1 062～2 007 mg·(m²·d)^-1之间.床体间比较认为,植物床脱氮效果明显好于空白床,芦苇床、茭草床单位面积脱氮效率高出空白床63%和27%;同时考察的植物吸收量证明,植物吸收氮的量非常有限,不到去除量的5%,证明植物主要通过吸收以外的其它因素如改善水力条件和根系微环境来提高系统的氮去除效率.研究结果为潜流湿地脱氮机理的理解和设计提供参考.

Relationships Between Loading Rates and Nitrogen Removal Effectiveness in Subsurface Constructed Wetlands

About forty kinds of nitrogen loading removal rate were studied in field in 15 months, inflow and outflow loading rules of reeds/Zizania caduciflora/mixing and no-plant bed were discussed in different inflow loading. The four kinds SFS inflow loading changed from 400 mg x (m2 x d)(-1) to 8 000 mg x (m2d)(-1), while outflow loading is less than 7,000 mg (m2 d)(-1). Results show that outflow loading increase with the increase of inflow loading, linear relation is obvious. Total nitrogen removal rate has the same trend at low inflow loading. But in high inflow loading TN removal rate has much variation. The system had better run between 2,000 mg x (m2 x d)(-1) and 4,000 mg x (m2 x d)( -1) inflow loading. Average removal rate in between 1062 mg x (m2 x d)(-1) and 2 007 mg x (m2 x d)(-1). Plant SFS removal rate is better than no-plant SFS. TN removal rate of reed and zizania caduciflora bed is 63 % and 27 % higher than no-plant bed. Plant harvesting is unimportant and contributes less than 5% of TN removal loading, plant can improve system microenviroment and hydrology condition which could increase TN removal rate. The results provided deep insight to SFS nitrogen removal and reference to SFS design.