College of Water Conservancy and Environmental Engineering, Zhengzhou University, Zhengzhou 450001, China.
Research Center for Environmental Policy Planning & Assessment of Zhengzhou University, Zhengzhou 450002, China E-mail:
Water Sci Technol. 2019 May;79(9):1639-1647. doi: 10.2166/wst.2019.156.
Micro-polluted river water is characterized as having limited biodegradability, low carbon to nitrogen ratio and little organic carbon supply, all of which makes it hard to further purify. Two bench scale constructed wetlands (CWs) with a horizontal subsurface flow mode were set up in the laboratory to evaluate their feasibility and efficiency on denitrification with and without corn cobs as external carbon sources. Micro-polluted river water was used as feed solution. The CW without corn cobs substrates possessed a good performance in removing chemical oxygen demand (COD, <40 mg/L) and ammonia nitrogen (NH-N, <0.65 mg/L), but less efficiency in removing total nitrogen (TN) and nitrate nitrogen (NO-N). In marked contrast, the CW with 1% (w/w) corn cobs substrates as external carbon sources achieved a significant improvement in the removal efficiency of TN (increased from 34.2% to 71.9%) and NO-N (increased from 19% to 71.9%). The incorporation of corn cobs substrates did not cause any obvious increase in the concentrations of COD and NH-N in the effluent. This improvement in the denitrification efficiency was owing to the released organic carbon from corn cobs substrates, which facilitated the growth of abundant microbes on the surface and pores of the substrate. The open area of the used corn chips is larger than that of the pristine ones, and corn cobs can continue to provide a carbon fiber source for denitrification.
微污染河水具有可生化性差、碳氮比较低、有机碳源供应不足等特点，进一步净化难度大。本研究采用实验室规模的水平潜流人工湿地，分别以玉米芯作为外加碳源和无外加碳源，考察其对微污染河水的脱氮效能。结果表明，无外加碳源的人工湿地对 COD（<40 mg/L）和氨氮（NH4-N，<0.65 mg/L）的去除效果较好，但对总氮（TN）和硝酸盐氮（NO3-N）的去除效果较差；而投加 1%（w/w）玉米芯作为外加碳源的人工湿地，TN 和 NO3-N 的去除率分别由 34.2%和 19%提高至 71.9%和 71.9%。外加碳源对 COD 和 NH4-N 的去除效果没有明显影响。玉米芯的添加为微生物的生长繁殖提供了丰富的碳源，增加了湿地中微生物的数量和活性，这是提高脱氮效率的主要原因。此外，玉米芯的比表面积大于玉米芯碎屑，为反硝化反应提供了持续的碳源。
