滞留时间和进水有机物对生物滞留系统除氮的影响

Effect of Retention Time and Organic Matter on the Nitrogen Removal by Bioretention

传统雨水生物滞留系统对氮的去除很不稳定。为了提高硝氮和总氮的去除效果,尝试在生物滞留系统底部增加内部淹没区,提供所需的缺氧环境,并延长系统内雨水的停留时间,改善系统的除氮能力。对有淹没区运行条件下进水有机物浓度和滞留时间除氮的影响进行了试验。结果表明系统在有淹没区和无淹没区运行条件下,对NH_4^+-N的平均去除率均在90%以上。无淹没区时系统对NO_3^--N的去除率为21%。有淹没区时(滞留时间2 h)系统对NO_3^--N和TN的去除作用显著提高到74%和78%。淹没运行时进水中COD浓度可以显著影响NO_3^--N的去除效果。当COD浓度为0~100 mg/L,NO_3^--N(7~9 mg/L),去除率随COD浓度的增加而显著升高。滞留时间对NO_3^--N去除效果的影响较为明显,滞留时间从1 h增加到8 h,系统的NO_3^--N平均去除率从21%增加到93%。

The traditional bioretention system is very unstable to remove nitrogen from rainwater. Aiming at increase the removal efficiency of nitrogen,the internal submerged zone( ISZ) at the bottom of the bioretention was established to provide the anoxic environment and to prolong the retention time of rainwater in the system. The effect of COD concentration and retention time on nitrogen removal was investigated. The results showed that the average removal rate of NH_4^+-N was above 90% at conditions with and without ISZ. The removal rate of NO_3^--N was21% by bioretention without ISZ,whereas the removal of NO_3^--N and TN significantly increased to 74% and 78%by bioretention with ISZ at the retention time of 2 h. At COD of 0 ~ 100 mg/L,the removal rate of NO_3^--N( 7 ~9 mg/L) increased significantly with the increase of COD level in the influent. The effect of retention time on NO_3^--N removal was marked,the average removal rate of NO_3^--N increased from 21% to 93% when the retention time increased from 1 h to 8 h.