Influence of operational mode, temperature, and planting on the performances of tidal flow constructed wetland

Abstract

In order to investigate the effect of operational mode, temperature, and planting on the performance of tidal flow constructed wetland (TFCW), four lab-scale units were operated in parallel experiments. They were operated in three cycles d⁻¹ tidal flow mode with planting (3TF+P), three cycles d⁻¹ tidal flow mode without planting (3TF), one cycle d⁻¹ tidal flow mode with planting (1TF+P), and continuous flow mode with planting (CF+P), respectively. The results demonstrated that the multi-cycle tidal flow operational mode promoted the biofilm growth and pollutant removal with the low relative clogging coefficient (RCC) of 21.42% during the whole experimental period. The average COD, -N, and -P area removal rate in 3TF+P reached 18.00, 2.38, and 0.24 g m⁻² d⁻¹, respectively. Meanwhile, the influence of low temperature on the performance of TFCW in the winter was partially compensated by the multi-cycle operational mode, which made the performance of TFCW more stable than that of other systems under temperature variation. Planting Canna indica L. (Cannaceae) led to an increase in average area removal rate of N with 24.17%. The net uptake of N by planting was 0.35 g m⁻² d⁻¹, which accounted for 17.95% of the total nitrogen removal. Besides the direct uptake, the combination of aerobic zone close to rhizosphere and anaerobic zone around rhizosphere may also play an important role in the nitrification–denitrification process. The direct P removal by Canna indica L. (Cannaceae) was quantified as 0.01 g m⁻² d⁻¹, which only accounted for 4.17% of the -P removal.

Keywords:

• Tidal flow constructed wetland
• Temperature
• Canna indica L
• Oxygen transport
• Clogging

Acknowledgments

The authors are thankful to the National Natural Science Foundation of China (51178047, 51378190, 51039001), and Furong Scholar of Hunan Province for support.

Notes

Presented at the 7th International Conference on Challenges in Environmental Science and Engineering (CESE 2014) 12–16 October 2014, Johor Bahru, Malaysia