补充碳源提取液对人工湿地脱氮作用的影响

为了提高人工湿地的脱氮效率,在不同条件下分别对美人蕉、香蒲及稻杆进行稀硫酸水解,以获得相应碳源提取液.正交实验表明,稀硫酸浓度的提高和水解时间的增加都会导致碳源释碳能力的提高,稻杆在5%稀硫酸溶液中水解30 min以上,释碳能力最高.通过观察,前2 d是系统脱氮反应高峰时段.对以NH₄⁺-N和NO₃^--N为氮源的脱氮过程,随C/N比升高,NO₃^--N和TN去除率增长明显;而NH₄⁺-N受溶解氧制约,去除有限;随C/N比升高,碳源对系统溶解氧的竞争会进一步抑制硝化反应的彻底进行.而对以NO₃^--N为氮源的反硝化过程,补充碳源对TN和NO₃^--N的去除有明显作用;TN去除率由54%提高到95%,NO₃^--N去除率由48%提高到96%;中间产物NO₂^--N的积累与NO₃^--N去除率有关;当NO₃^--N去除率较高时,NO₂^--N无积累.此外,基质反硝化强度也随C/N比升高呈上升趋势,湿地填料细沙层的反硝化强度略高于碎石层.

Effect of adding carbon source extracts on nitrogen removal in constructed wetland

To enhance the nitrogen removal efficiency in constructed wetland, Canna indica Typha latifolia and straw were hydrolyzed by dilute sulphuric acid under different conditions to get relevant carbon source extracts. Orthogonal test indicated that the increase of dilute acid concentration and time of the hydrolysis led to the increase of COD concentration. Straw hydrolyzed in 5% dilute sulphuric acid over 30 minutes had the highest COD concentration. The removal rate of nitrogen was high in the initial two days of the experiment. The removals of NH₄⁺-N and TN obviously increased as the C/N ratio increased, while NH₄⁺-N was controlled by DO and its removal was limited. Carbon source further restrained nitrification by competition for DO. Adding carbon source significantly enhanced the removal of TN and NO₃^--N, with the removal of TN increased from 54% to 95% and the removal of NO₃^--N increased from 48% to 96%.The accumulation of intermediate product, NO₂^--N, was dependent on the removal rate of NO₃^--N. When the removal of NO₃^--N was relatively high, no accumulation of NO₂^--N was found. Furthermore, denitrification in matrix showed an increasing tendency as the C/N ratio increased and denitrification in the fine sand layer was relatively higher than that in the rubble layer.