Marine and Freshwater Research Marine and Freshwater Research Society
Advances in the aquatic sciences

Just Accepted

This article has been peer reviewed and accepted for publication. It is in production and has not been edited, so may differ from the final published form.

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

Yajun Qiao , Penghe Wang , Wenjuan Zhang , Guangfang Sun , Dehua Zhao , Nasreen Jeelani , Xin Leng , Shuqing An

Abstract

We investigated whether subsurface flow constructed wetlands (SSF-CWs) can remove nitrogen from saline wastewater and if salinity affected nitrogen removal during the cold season (average 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+) wastewater, while eight unplanted SSF-CWs were fed with normal (CWU) or saline wastewater (CWU+). The systems were run continuously at a hydraulic loading rate of 187.5 mm·d−1 and a hydraulic retention time of 4 days. The nitrogen removal efficiency, plant parameters, and bacterial abundance and community composition were measured. In CWP, 80% of ammonium-nitrogen (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. Under the higher salinity, not only was there a decrease in plant biomass (32.1%) and nitrogen uptake (50.1%), but also reduced growth (37.8%), activity (68.0%), and oxygen release (62.9%) of roots. The bacterial community composition was also different in the 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, and changes in microbial community composition.

MF17171  Accepted 08 November 2017

© CSIRO 2017