Effect of the ammonia concentration on the performance of wetland microbial fuel cells

Li Wang,Wenlei Wang,Yutong Song,Jiafeng Fu,Yan Li

doi:10.1051/e3sconf/202126901002

Abstract

This work explores the effect of the ammonia concentration on the wetland synthesis of microbial fuel cell (MFC) and on the production and the efficiency of sewage purification. Four ammonia concentrations from 1 to 30 mg/L have been selected. Under the fixed condition of a chemical oxygen demand (COD) concentration of 200 mg/L, a constructed wetland microbial fuel cell (CW-MFC) could be built. The results show that by selecting the optimum ammonia concentration the production of the CW-MFC could be promoted; a higher ammonia concentration (>20 mg/L) is found to inhibit the production activity of CW-MFC. In the optimum conditions, Cathode and anode thickness is 10 cm, the ammonia concentration is 10 mg/L, the COD concentration of 200 mg/L, the maximum power density of the battery is 13.6 W/m3, the corresponding current density is 148.6 A/m3 and the battery internal resistance is 270 Ω. At the ammonia nitrogen concentration of 10 mg/L, the removal rates of ammonia nitrogen and COD were up to 89.7% and 98.47% respectively. As the ammonia nitrogen concentration increased to 30 mg/L, the ammonia nitrogen and COD removal rates decreased to 74.6% and 90.69% respectively. That is, when the ammonia nitrogen concentration is 10 mg/L, CW-MFC can exhibit the best performance.

Highlights

The wetland microbial fuel cell is a new type of water purification device, which combines an artificial wetland with a microbial fuel cell; the anaerobic oxidation of organic matter at the anode is promoted by a microbial metabolism under electrical bias [1,2,3]
The CW-microbial fuel cell (MFC) system used in this work is made of plexiglass cylinders with an inner diameter of 19 cm, a total height of 58 cm; Below is the anode part, above is the cathode part, the total volume of the reactor is 14.75 L, the effective storage capacity is 7.1L, set the sampling port at the bottom 20cm, 30cm, 40cm, the upper part contains the water outlet; the filling matrix stacks and the electrode materials are: a 10 cm thick ceramic, and three repeated cycles of a 5 cm thick quartz sand layer and a 5 cm thick activated carbon particles embedded in a carbon felt electrode
Rich bamboo is used as the wetland plant, the fuel cell electrode spacing is 10 cm, the electrode thickness is 3 mm, study the effect of different ammonia nitrogen concentrations on the electricity production performance of microbial fuel cells

Summary

Introduction

The wetland microbial fuel cell is a new type of water purification device, which combines an artificial wetland with a microbial fuel cell; the anaerobic oxidation of organic matter at the anode is promoted by a microbial metabolism under electrical bias [1,2,3]. To reduce the operating costs there is an urgent requirement for developing improved cathodic aeration devices. The use of plant composite bio-cathodes instead of precious metal cathodes as in the conventional CW-MFC, would allow to greatly reduce the electrode material costs, possibly improve the catalytic activity of the electrode and allow for the largescale production of CW-MFCs [6,7,8]. For the development of large-scale CW-MFC, the high cost of the infrastructure and the too low power generation are the two main problems; the cathode material plays a key role in these problems, because of its high cost and slow redox reaction. The biocathode is promising in the CW-MFC application

Objectives

Methods

Results