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Water 2017, 9(11), 865;

Cyanobacterial Nitrogen Fixation Influences the Nitrogen Removal Efficiency in a Constructed Wetland

Beijing Key Laboratory of Wetland Services and Restoration, Institute of Wetland Research, Chinese Academy of Forestry, Beijing 100091, China
School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China
Author to whom correspondence should be addressed.
Received: 18 September 2017 / Revised: 1 November 2017 / Accepted: 3 November 2017 / Published: 7 November 2017
(This article belongs to the Special Issue Biological Treatment of Wastewater)
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Nitrogen removal efficiency in constructed wetlands (CW) is influenced by multiple environmental factors. However, little is known about the role of cyanobacterial nitrogen fixation in affecting nitrogen removal efficiency. This study investigated how cyanobacterial nitrogen fixation affects the efficiency, at which a CW removes nitrogen from an associated artificial lake (AL) in Beijing. For this purpose, we measured cell densities of N-fixing and non-N-fixing cyanobacteria, the aquatic nitrogen fixation rate (RNfix), and the concentration of various nitrogen fractions over the growing season (April–November) of 2014 in both AL and CW. We found that the removal of particulate organic nitrogen (PON) contributed to >90% of the total nitrogen removal in the CW. The removal efficiency of PON was lower during August–October (55.45 ± 27.49%) than during April–July (68.86 ± 8.83%). Phytoplankton proliferation in summer, as one of the main sources of PON, may have exceeded the capacity of the CW and led to declines in PON removal efficiency. RNfix peaked in July–October (3–169 ng N·L−1·h−1) and was positively correlated with both PON concentration and the cell density of N-fixing Anabaena sp. over the growing season, suggesting that aquatic nitrogen fixation (primarily in the AL) may increase PON and thereby reduce the its removal efficiency in the CW. View Full-Text
Keywords: constructed wetland; nitrogen fixation; particulate organic nitrogen; Anabaena sp. constructed wetland; nitrogen fixation; particulate organic nitrogen; Anabaena sp.

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Zhang, X.; Jia, X.; Yan, L.; Wang, J.; Kang, X.; Cui, L. Cyanobacterial Nitrogen Fixation Influences the Nitrogen Removal Efficiency in a Constructed Wetland. Water 2017, 9, 865.

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