Effects Of Polypyrrole Coated Electrode On Biofilm Electrode Reactor Of Hydrogenotrophic Denitrification And Methanogenesis

Biofilm Electrode System had received more and more attention in recent years as a new method for wastewater treatment which combines biological technology and electrochemical process. It offers various advantages such as a large quantity of fixed biofilm, high electrochemical oxidation reduction ability, and the high mass transfer efficiency between electrode and biofilm. With the development of biological electrochemical reactor, Electrode modifications involved in biofilm electrode reactor have been widely studied. A lot of reports show that, significant improvements of the reactor performance were achieved using modified electrodes.In this study, the effect of polypyrole (PPy) films electropolymerization on carbon felt (CF) electrode was investigated, and the composite was characterized by scanning electron microscope (SEM) and fourier transform infrared (FTIR) spectroscopy. The modified electrode was applied in biofilm-electrode reactors, and its effects on the reactor performance, the adhesion, the component of extracellular polymer substrates (EPS) and the microbial community of the biofilm were also demonstrated.Results indicated that PPy films could form evenly and stably on CF electrode by using potentiostatic electropolymerization method doping with 25 mM AQDS (anthraquinone-2, 6-disulfonic acid disodium salt). Besides, compared with the control reactor, the NO3--N removal rate of the modified electrode biofilm-electrode hydrogenotrophic denitrification reactor was enhanced by 24.7%. Compared with the control reactor, the COD removal rate of the modified electrode biofilm-electrode methanogenesis reactor was enhanced by 18%, CH4 accumulation was enhanced by three times.SEM and 16S rDNA were carried out to analyze the structures and communities of the biofilm on the electrode. It was visible that more biomass was attached on the modified electrode in R2, which indicated that the approach presented here could improve bacteria adhesion on the cathode. The analysis results of EPS content of the biofilm in the reactor indicated that electrode modification contributeds to the increase of EPS content and the ratio of protein to polysaccharide and finally improved the activity, strength and stability of the biofilm.16S rDNA analysis of the biofilm of hydrogenotrophic denitrification indicated that Hydrogenophaga sp. and Thauera sp. were the dominant isolates in R2, which were different from Rl with the dominant isolate of Dechloromonas sp. Moreover, the microbial communities of the biofilm on the modified electrode in R2 were more diversified than those of the control in R1.16S rDNA analysis of the biofilm of methanogenesis indicated that Methanosarcina sp. was the dominant isolate in both two reactors, then was Methanobacterium sp. in R1, and Methanomicrobia sp. in R2, The significant differences between the two reactors indicated that electrode modification had an effect on the composition of electrode biofilm microbial communities.