水平潜流人工湿地堵塞初期微生物群落结构变化

为了寻找合适的湿地堵塞监测指标, 文章通过运行4组湿地装置来模拟水平潜流人工湿地堵塞的过程, 并研究人工湿地中微生物群落在湿地堵塞初期的响应。在人工湿地反应器运行过程中, 定期监测基质过滤速率与人工湿地处理性能, 包括化学需氧量(COD)、总氮(TN)和总磷(TP)去除效率, 同时应用高通量测序技术测定并分析湿地反应器中微生物群落结构组成与多样性。结果表明: 随着堵塞的形成, 在4组人工湿地中, 基质过滤速率和TP的去除效率持续下降, 而COD和TN的去除效率分别为50%—85%和10%—20%; 16S rDNA测序结果表明堵塞会降低细菌群落的丰富度和多样性; 人工湿地系统中的优势菌门主要是变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)和绿弯菌门(Chloroflexi)等, 且当湿地进入堵塞初期后, 变形菌门丰度明显增加, 具体表现为其门下的反硝化细菌属(Thauera、Zoogloea和Rhizobium) 丰度显著增加, 此外厚壁菌门和绿弯菌门的有机物降解菌属(Clostridium sensu stricto、Gracilibacter和Levilinea)的丰度也明显增加, 这表明上述菌属有望成为人工湿地系统堵塞初期的预警指示菌。

MICROBIAL COMMUNITY STRUCTURE DURING THE INITIAL CLOGGING STAGE IN HORIZONTAL SUBSURFACE FLOW CONSTRUCTED WETLANDS

Microorganisms play an essential role in material transformation and energy flow in constructed wetland systems. However, the excessive reproduction of microbes would cause the formation of large amounts of extracellular polymers (EPS), which can lead to the clogging in constructed wetlands. This study mainly focused on bacteria and compared its ability to indicate the clogging in constructed wetlands so as to provide some important implications for developing the biological assays to monitor the clogging of constructed wetlands in the future. In order to achieve this, four horizontal subsurface flow constructed wetlands (HFCWs) were designed and operated to simulate the process of clogging and to investigate the interaction between the clogging and microorganism by monitoring the variation of the filtration rate of substrates, the removal efficiency shift of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorous (TP), and bacterial communities by high-throughput sequencing of 16S rDNA. Results showed that as the clogging progression, the filtration rate of substrates and the TP removal efficiency consistently decreased in four wetland systems, while the COD and TN removal efficiency was fluctuated constantly with 50%—85% and 10%—20%, respectively. Sequencing results indicated that the clogging reduced the richness and diversity of bacterial community structure; Proteobacteria, Firmicutes and Chloroflexi were dominated in all HFCWs; the relative abundance of Proteobacteria increased significantly as the clogging developed; more specifically, the abundance of denitrifying bacteria belonging to Proteobacteria (Thauera, Zoogloea and Rhizobium) and organic-metabolizing bacteria belonging to Firmicutes and Chloroflexi (Clostridium sensu stricto, Gracilibacter and Levilinea) increased significantly. These results suggest that the afore-mentioned bacteria were expected to act as early warning indicators for the clogging of constructed wetlands.