Enhanced nitrogen removal through aerobic denitrifying bacteria in horizontal subsurface flow constructed wetlands: Influencing factors and microbial community structure

Variation in the demand for dissolved oxygen during nitrification and denitrification processes is one of the main constraints for nitrogen removal performance in conventional constructed wetlands. This study aimed to enhance the performance of horizontal submerged flow constructed wetland (HSCW) systems through aerobic denitrification (AD). The effects of different operating conditions on the performance and microbial community structure of the system were investigated using three experimental systems including a non-aerated HSCW without bacterial inoculation (CWC), a non-aerated HSCW with bacterial inoculation (CWM) and an intermittently aerated HSCW with bacterial inoculation (CWMA). Results showed that C/N ratio of 10 and aeration rate of 0.2 L/ (min & sdot;L) were the optimum conditions for CWMA, which showed 29.01 % and 12.17 % higher COD and TN removals than CWC, even at an average temperature of 8.80celcius. Microbial community analysis revealed that the addition of Pseudomonas stutzeri significantly increased the microbial diversity and abundance within the HSCWs. This study provides a new idea for the treatment of nitrogenous wastewater and the AD-CW system has a promising application in low-temperature areas.