Study On Treatment Effect And Power Generation Performance Of Constructed Wetland Coupled Microbial Fuel Cell System For Beer Wastewater

The effects of HRT,influent COD,and electrode spacing on wastewater treatment and power generation performance were explored in two Constructed Wetland-Microbial Fuel Cell systems(CW-MFC)with different electrode spacing(reactor A and B).The electrode spacings of reactor A and B were 18 cm and 28 cm,respectively.To provide technical references for further research and for the practical operation of CW-MFC.In addition,the influence of cathode microorganisms of reactor A on the power generation performance of the system was also investigated.The microbial community structure characteristics of the anodes of the two reactors and the cathodes of the reactor A were analyzed,and macroscopic experimental phenomena were combined with microscopic data.The main conclusions are as follows:(1)The extension of HRT was conducive to improving the sewage treatment and power generation performance of the system,however,excessive extension is ineffective for the electricity output.When the influent COD was 500 mg/L,reactors A and B both obtained the best wastewater treatment effect when the HRT was 48 h.The best electricity generation performance of reactors A and B was achieved when the HRT was 24 h and 48 h,respectively.Improving influent COD within the appropriate range facilitated the power generation performance of the CW-MFC.The optimal power generation performance of reactors A and B were achieved when the HRT was 24 h and the influent COD was 1000 mg/L.The maximum output voltage and maximum power density of reactor A were 548 mV and 120.31 mW/m3,respectively.The maximum output voltage and maximum power density of reactor B were 540 mV and 116.83 mW/m3,respectively.The reduction of electrode spacing was beneficial to wastewater purification and power generation of the system.Compared to reactor B,reactor A with smaller electrode spacing achieved better electricity generation and contaminant degradation under the optimal condition.Its average output voltage could be improved by 5.1%?-46.1%and the removal rates of COD and NH4+-N could also be improved by 0.2?4.9%and-0.9?13.7%,respectively.(2)The introduction of cathode microorganisms has significantly improved the wastewater removal efficiencies of the reactor.When influent COD was 500 mg/L,1000 mg/L,and 2000 mg/L,the average removal rates of COD in reactor Al were 93.1%,94.8%,and 91.5%,respectively,which were 6.9%,5.0%,and 64.2%higher than that of reactor A under the same conditions;the average removal rates for NH4+-N in reactor Al were 95.5%,99.5%,and 79.8%,respectively,which were 9.6%,50.7%,and 70.2%higher than that of reactor A under the same conditions.The addition of cathode microorganisms can inhibit the power generation performance of the system.When the influent COD was 500 mg/L and 1000 mg/L,the maximum power density of reactor A was 72.39 mW/m3 and 185.80 mW/m3,respectively.The addition of cathode microorganisms reduced the maximum power density of reactor A by 53.34%and 27.7%,respectively.(3)According to the analysis of the microbial community structure,reactor A has more types of Gram-negative bacteria than reactor B.At the genus level of anode microorganisms,the majority of bacteria in reactor A were Gram-negative bacteria,such as Sulfuritalea,Aquaspirillum,Arcobacter,Desulfomicrobium,Pseudomonas,Acidaminobacter,Geobacter.However,there were more Gram-positive bacteria in reactor B,such as Anaerofustis,Sedimentibacter and Desulfitobacterium.The total proportion of Gram-negative bacteria in the anodes of reactors A and B were 17.15%and 14.78%,respectively.Therefore,from the perspective of electron transfer,it is speculated that the electrical activity of reactor A,which has more Gram-negative bacteria in the anode microorganism,was better than that of reactor B.This was consistent with the power generation performance in both reactors.(4)Although there are more Gram-negative bacteria in the cathode microorganisms of reactor A,and some of them have been confirmed to be electrically active,the addition of cathode microorganisms reduced the number of reactants that were semi-reactive in the cathode electricity generation.This had a greater impact on the power generation performance of the system.Therefore,the addition of cathode microorganisms in reactor A would have a limiting effect on the power generation performance of the system.