Microbial Fuel Cell Coupled Constructed Wetland For Bio-refractory Organics Removal

In this paper, a microbial fuel cell coupled constructed wetland (CW-MFC) was established for azo dye degradation. Based on the previous study, Reactive Brilliant Red X-3B(ABRX3B) was chose as the model refractory organics. Effects of co-substrate, buffer solution concentration, electrode area, electrode distance and wetland substrate on the performance of CW-MFC were investigated, to improve the abilities of CW-MFC on refractory organics purification and simultaneous electricity generation. Main contents and results were as follows:Glucose, Sodium acetate and starch were selected as the co-substrates of X-3B in CW-MFC. The results showed that the glucose was the best co-substrate for CW-MFC. Co-substrates not only had an impact on the decolorization performance and the further degradation of decolorizing products, but also affected the performance of electricity production via the anode microbes.Four different concentrations of buffer were chosen to study the effect of buffer concentration on the performance of CW-MFC. The results showed that increasing buffer concentration in a certain range were benefit to the degradation of X-3B and electricity generation performance. However, excessively high buffer concentrations might inhibit the activity of microbes which would reduce the performance of CW-MFC.Five kinds of wetland substrates were selected to analyze the effects of material, particle size and porosity of wetland substrate on the performance of CW-MFC. The results showed that the rough surface and the small size of substrates were benefit to the growth of microbes. This could promote the degradation of X-3B in the substrate layer which would improve the degradation performance of CW-MFC. However, microbial biomass in the substrate resulted in excessive consumption of co-substrate which may cause the lack of nutrients in the anode layer. This would reduce the electricity production. Besides, the greater the size and porosity of the substrates were, the smaller the mass transfer resistance was, which made a better electricity production performance.To investigating the effects of cathode area on the performance of CW-MFC, four different cathode area were settled. The results showed that with the increase of the cathode area, the removal ability of CW-MFC firstly increased and then decreased. The best X-3B removal efficiency was achieved when the ratio of electrode area was 1.9, the removal rate was 99.41%. The electricity generation performance of CW-MFC was improved with the increase of the cathode area. The best electricity generation performance was achieved when the ratio of electrode area was 2.5, but the removal rate of X-3B was only 85.48%. By control the ratio of electrode area to achieve the best balance of the reaction rate between cathode and anode which can make a great contribution to improve the performance of CW-MFC.In order to study the effects of electrode spacing on the performance of CW-MFC, various electrode spacing were settled. CW-MFC with the 13.2 cm electrode spacing achieved the best X-3B removal as well as the power generation efficiency. The removal rate of X-3B was 91.05%. And the power density could reach 0.196 W/m3.