Journal of Ecology and Rural Environment ›› 2017, Vol. 33 ›› Issue (4): 364-371.doi: 10.11934/j.issn.1673-4831.2017.04.010

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Greenhouse Gases Emission in Operation of Constructed Eichhornia crassipes Ecological Ponds In-Depth Purifying Tail Water From Sewage Treatment Plants

QIU Yuan-yuan1,2, ZHANG Zhi-yong2, ZHANG Jin-hua1, ZHANG Ying-ying2, WEN Xue-zheng2, SONG Wei2, WANG Yan2, LIU Hai-qin2   

  1. 1. School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China;
    2. Institute of Agricultural Resource and Environmental Sciences, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
  • Received:2016-06-27 Online:2017-04-25 Published:2017-04-01


An ecological wastewater purifying project consisting of three ponds with Eichhornia crassipes growing therein connected in tandem was constructed for in-depth purifying tail water from a town-run sewage treatment plant. Greenhouse gases (CO2, CH4 and N2O) emitted in the operation of the project were collected and analyzed with a home-developed in-situ bubble trapping device coupled with gas chromatography during the period of August-November, 2015 to explore characteristics of the emission and relationship of the emission with the main environmental factors of the waterbody. Results show that the ecological project performed quite well in removing TN and TP with a rate up to 68.07% and 64.21%, respectively. The concentration of TN in the effluent of the project approached to the criteria of Grade V of the "Standard for Environmental Quality of Surface Water (GB 3838-2002)" and the concentration of TP was lower than the criteria. During the study period from August to November in 2015, the average flux of CO2, CH4 and N2O emitted from the project was 0.058, 0.076 and 1.539 mg·m-2·h-1, respectively, and the cumulative emission of CO2, CH4 and N2O reached 1.273, 1.685 and 33.59 kg, respectively. The fluxes of CO2 and CH4 varied significantly with the season, being much higher in summer than in autumn, whereas the flux of N2O did not. Along the direction against the water flow in the ecological project, the fluxes of CO2, CH4 and N2O increased first and then declined. Correlation analysis shows that the fluxes of CO2 and CH4 were closely and positively related (P<0.05) to the temperature of water in the ponds; the flux of CO2 was significantly and negatively related (P<0.05) to pH and DO; the flux of CH4 was negatively related (P>0.05) to pH and DO; and the flux of N2O was positively related (P>0.05) to TN and NO3--N concentrations in the water. All the findings in this study may serve as a useful reference for evaluation of greenhouse gases emission from ecological wastewater treatment projects of ponds grown with Eichhornia crassipes.

Key words: Eichhornia crassipes, domestic sewage, in-depth treatment, greenhouse gas, emission flux

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