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Advances in the aquatic sciences
RESEARCH ARTICLE

Elevated salinity inhibits nitrogen removal by changing the microbial community composition in constructed wetlands during the cold season

Yajun Qiao A B , Penghe Wang A C , Wenjuan Zhang A , Guangfang Sun A , Dehua Zhao A B D , Nasreen Jeelani A B , Xin Leng A B D and Shuqing An A B
+ Author Affiliations
- Author Affiliations

A Institute of Wetland Ecology, School of Life Science, Nanjing University, Xianlin Avenue 163, Nanjing, 210046, P.R. China.

B Nanjing University Ecology Research Institute of Changshu, Huanhu Road 1, Changshu, 215500, P.R. China.

C MCC Huatian Engineering and Technology Corporation, Fuchunjiangdong Street 18, Nanjing, 210019, P.R. China.

D Corresponding authors. Email: dhzhao@nju.edu.cn; lengx@nju.edu.cn

Marine and Freshwater Research 69(5) 802-810 https://doi.org/10.1071/MF17171
Submitted: 8 June 2017  Accepted: 8 November 2017   Published: 8 February 2018

Abstract

In the present study we investigated whether subsurface flow constructed wetlands (SSF-CWs) can remove nitrogen from saline waste water and whether salinity affects nitrogen removal during the cold season (mean water temperature <10°C). Eight Iris pseudacorus-planted SSF-CWs were fed with normal (salinity 1.3–1.5‰; CWP) or saline (salinity 6.3–6.5‰; CWP+) waste water; similarly, eight unplanted SSF-CWs were fed with normal (CWU) or saline waste water (CWU+). The systems were run continuously at a hydraulic loading rate of 187.5 mm day–1 and a hydraulic retention time of 4 days. Nitrogen removal efficiency, plant parameters and bacterial abundance and community composition were measured. In CWP, 80% of NH4+-N and 52% of total nitrogen (TN) were removed. In contrast, the removal rates of NH4+-N and TN in CWP+ were reduced by 27 and 37% respectively. In the presence of higher salinity, not only were there decreases in plant biomass (32.1%) and nitrogen uptake (50.1%), but the growth, activity and oxygen release of roots were also reduced (by 37.8, 68.0 and 62.9% respectively). Bacterial community composition also differed under conditions of elevated salinity. Elevated salinity is associated with lower nitrogen removal in SSF-CWs, which we speculate is a result of suppressed wetland macrophyte growth and activity, as well as changes in microbial community composition.

Additional key words: bacterial community, Iris pseudacorus, nitrification–denitrification, nitrogen reduction, saline waste water.


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