NO3--N负荷对树皮填料人工湿地早期反硝化及释碳速率的影响

为了将污水厂尾水作为再生水进行利用,常常需要对尾水进行深度脱氮,针对尾水的水质特征,在深度脱氮时常常需投加碳源.试验采用树皮作为填料,兼作脱氮的缓释碳源,进行树皮填料人工湿地深度脱氮模型试验,研究进水NO_3~--N负荷对反硝化和树皮释放碳源的影响.结果表明,树皮填料人工湿地可稳定脱氮;反硝化速率遵循Monod关系式,随进水NO_3~--N负荷增大而递增,饱和常数KS=19.10 mg·L~(-1);硝氮去除率随进水NO_3~--N负荷增大而减小;在树皮填料人工湿地运行早期,树皮释碳总量、树皮释碳速率随进水NO_3~--N负荷增大而递增,与进水NO_3~--N均呈线性正相关;树皮静态释碳速率为0.2 mg·(g·d)-1,与腐朽木等中空松散的植物碳源相比,碳源缓释性能较好,释碳周期较长,是良好的缓释碳源.

Effects of NO3--N Loading on the Early-Period Efficiency of Denitrification and Carbon Releasing in Constructed Wetland Filled with Bark

The reuse of tailwater as recycled water requires an advanced nitrogen removal treatment, during which carbon source is added based on the tailwater quality. This study conducted an advanced nitrogen removal model test in constructed wetland to evaluate the effects of influent NO₃^--N loading on denitrification and carbon releasing. In the constructed wetland, bark was used as filler and carbon source for nitrogen removal. The results showed that nitrogen removal was steady in the constructed wetland filled with bark. Denitrification velocity followed the Monod equation, and it increased as the influent NO₃^--N loading increased. The saturation constant K_S was 19.10 mg·L^-1. NO₃^--N removal rate decreased as the influent NO₃^--N loading increased. During the early periods of operating the constructed wetland filled with bark, the carbon releasing amount and velocity increased as the influent NO₃^--N loading increased. Both factors were positively linearly correlated with the influent NO₃^--N loading. The static carbon releasing velocity was 0.2 mg·(g·d)^-1. Compared with the hollow and loose plant carbons, such as rotten wood, bark had a better performance and a longer cycle of carbon releasing, which made bark a good slow-release carbon source.