外置植物碳源型人工湿地系统反硝化脱氮效果及N2O释放

人工湿地系统在处理低碳氮比污水时,通过外加碳源来提高系统的脱氮效率。碳源是反硝化过程中重要的影响因素,对N_2O释放必然也产生影响。采用芦苇(Phragmites australis)和二球悬铃木(Platanus acerifolia)树叶为碳源的外置碳源型的人工湿地系统,以葡萄糖作为对比碳源,研究有机碳源对脱氮效果及N_2O释放量的影响。结果表明,芦苇和悬铃木树叶作为碳源,在植物分解稳定后,脱氮效果稳定,TN平均去除率分别为90.3%和92.5%,比空白组高出15%左右;单批次试验中,芦苇组和树叶组N_2O平均释放量分别为40.91μg/(m~2·h)和34.16μg/(m~2·h),略高于葡萄糖组的6.20μg/(m~2·h),但显著小于空白组的127.45μg/(m~2·h),累积释放量与TN去除量的比值小于0.1%且显著小于空白组;芦苇和树叶组基质微生物的反硝化作用强度及PLFAs总量均显著高于空白组,细菌PLFAs占PLFAs总量的比例均接近50%,而真菌PLFAs仅大于7%,细菌为优势种群。因此,向处理低C/N污水的人工湿地系统补充适宜的植物碳源材料,可以有效提高脱氮效率并降低N_2O释放。

On the denitrification characteristics of nitrogen removal and N2O emission in the constructed wetland systems supplied with the external plant carbon source

To study the influence of plant carbon sources on the nitrogen removal efficiency and N2O emission in the well-cultivated wetlands to treat the sewage with the low C/N ratio,we have chosen the reed (Phragmites australis) and the leaf litter (Platanus orientalis) as the external organic carbon sources,so as to establish a composite constructed wetland system with the plant material decomposing cell with the glucose as a kind of paralleled carbon source.The microbial denitrification intensity and phospholipid fat acid (abbreviated as PLFA) technology have also been applied to study the microbial denitrifying activity and the microbial dominant population.The results have shown that the wetland systems added with the two plant materials can display nice performance of N removal when the decomposition process of the plant materials can grow up to a stable state.The nitrogen removal efficiency of the systems supplied with the reed and leaves may account for 90.3％ and 92.5％,respectively,and even get to 15％ higher than that in the blank control system.In batch experiments,the average emission amount of N2O in the wetland systems with reed and leave litter turn to be 34.16 μg/(m2 · h)and 40.91 μg/(m2 · h),respectively,which are slightly higher than 6.20 μg/(m2 · h) of the glucose system and significantly less than 127.45 μg/(m2 · h) of the blank control system.The ratio of the cumulative emission of N2O to the TN removal proves to be less than 0.1％,which is significantly less than that of the blank control system.On the other hand,the microbial denitrification intensity and the total amount of PLFAs turn out to be significantly higher than those of the blank control system.In spite of this,the ratio of the PLFAs in the bacteria to the total PLFAs comes close to 50％,while PLFAs in fungi is only over 7％,with the bacteria remaining the dominant species.Therefore,it is possible for us to improve the nitrogen removal efficiency effectively and reduce the N2O emission by adding suitable plant materials as carbon sources to the constructed wetland system for treating the sewage in a lower C/N ratio.