JOURNALS/BOOKS
The factors influencing nitrous oxide emissions during nitrification and denitrification processes 1-12 H. Chai, N. Ai, G. Li, X. Hu, Q. He

Energy Education Science and Technology Part A: Energy Science and Research

2016 Volume (issue) 34(1): 1-12

 

 

The factors influencing nitrous

oxide emissions during nitrification

and denitrification processes

 

Hongxiang Chai1,2,*, Nanping Ai1,2, Gengsheng Li1,2, Xuebin Hu1,2, Qiang He1,2

 

1Key Laboratory of the Three Gorges Reservoir’s Eco-Environments, Ministry of Education, Chongqing University, Chongqing 400045, PR China;

2National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing 400045, China

 

 

 

 

Received: 16 November 2015; accepted: 27 December 2015

Abstract

 

    When treating the domestic wastewater in constructed wetlands (CWs), nitrous oxide (N2O), a greenhouse gas, would be released in substantial amounts during nitrification and denitrification processes. However, there are many factors affecting the activity of nitrifying bacteria and denitrifying bacteria, which include influent BOD5, COD/N ratio, influent nitrate and nitrite concentrations and pH. In this study, the change of N2O fluxes in a newly developed lateral subsurface constructed wetland was measured using the closed chamber method to research these factors influencing N2O emissions. The results showed that: (1) the N2O emissions would increase with the increase of influent BOD5 concentration in different seasons and different hydraulic load. (2) When the COD/N ratio was controlled at 5:1 or 10:1, the N2O fluxes was lowest with a flux of 80.29 μg/m2•d. (3) Improving the influent nitrate and nitrite concentrations could increase the emissions of N2O. The influent nitrite concentration was >1 mg/L, the N2O emissions greatly increased with a maximum of 487.38 μg/m2•d. (4) When the pH value was lower than 6.8, the N2O emissions would get a significant increase, with a maximum of 298.85 μg/m2•d. However, if the pH value was > 6.8, N2O emissions were very low with a flux of about 10 μg/m2•d.

 

Keywords: Constructed wetlands (CWs); Wastewater treatment; Nitrifying bacteria; Denitrifying bacteria; N2O emissions