3 years ago

Optimizing the performance of organics and nutrient removal in constructed wetland–microbial fuel cell systems

Xiaoou Wang, Yimei Tian, Hong Liu, Xinhua Zhao, Sen Peng

Publication date: 25 February 2019

Source: Science of The Total Environment, Volume 653

Author(s): Xiaoou Wang, Yimei Tian, Hong Liu, Xinhua Zhao, Sen Peng

Abstract

No studies have reported the operation optimization of constructed wetland–microbial fuel cell (CW–MFC) systems in terms of pollutant removal under the influence of multiple factors. Multifactor orthogonal experiment (L25(55)) was designed in this study to investigate the influence of multiple factors on the CW–MFC performance and determine the optimal operating conditions for the organics and nutrient removal. The tested factors include volume ratio of granular graphite in the substrates (A), dissolved oxygen (DO) concentration in the cathode zone (B), hydraulic retention time (HRT) (C), effluent reflux ratio (D), and external resistance (E). The results showed that the sequence and degree of the influence of the tested factors were C** > B** > E** > D* > A for chemical oxygen demand (CODCr) removal, C** > B** > D* > E > A for ammonia nitrogen (NH3-N) removal, C** > D** > B** > E* > A* for total nitrogen (TN) removal, and C** > D* > B > A > E for total phosphorus (TP) removal (* denotes significant influence (0.01 < p < 0.05) and ** denotes extremely significant influence (p ≤ 0.01)). HRT was found to be the most influential factor for pollutant removal in CW–MFCs with a contribution of over 50% for CODCr, NH3-N and TP removal, and over 45% for TN removal. The optimal operating conditions for CODCr, NH3-N, TN and TP removal in CW–MFCs were quite different from each other. Comprehensively considering the treatment efficiency of pollutant, treatment capacity of wastewater, and energy consumption from artificial aeration, the selected comprehensive optimal operating conditions for CW–MFCs were A = 20%, B = 1.5 mg/L, C = 1.5 days, D = 50%, and E ≤ 250 Ω. Moreover, incorporating the MFC significantly enhanced the organics and nitrogen removal in CWs by 8.72–11.04% CODCr and 9.78–12.04% TN.

Graphical abstract

Constructed wetland–microbial fuel cell (CW–MFC) system:

1.

HRT was the most influential factor for the removal of organics, nitrogen and phosphorus in CW–MFCs.

2.

External resistance was the most influential factor for power output of CW–MFCs.

3.

DO concentration in the cathode zone was significant for organics and nitrogen removal in CW–MFCs.

4.

Effluent reflux ratio was significant for the removal of organics, nitrogen and phosphorus in CW–MFCs.

5.

Incorporating MFC significantly enhanced organics and nitrogen removal in CWs by 8.72–11.04% CODCr and 9.78–12.04% TN.

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