Study Of Constructed Wetland Microbial Fuel Cell For Treating Organic Wastewater Containing Chromium

Cr(Ⅵ)and DOM in chromium-containing organic wastewater can show high ecological toxicity risk to organisms and the environment.In this study,constructed wetland microbial fuel cell(CW-MFC)was applied to the treatment of chromium-containing organic wastewater.Water quality and electrochemical analysis,XAD resin classification,three-dimensional fluorescence spectroscopy,gas chromatography-mass spectrometry and high-throughput sequencing were used to investigate the effects of bioelectricity production and Cr(Ⅵ)on water purification and electricity production,removal of dissolved organic matter and distribution of microbial communities.The main conclusions are as follows:(1)CW-MFC operated better than CW throughout the start-up phase,and the introduction of bioelectricity production and Cr(Ⅵ)was able to significantly improve the water purification and electricity production capacity of the wetland.The effect of COD concentration,Cr(Ⅵ)concentration and HRT on the performance of the plant was investigated by varying the operating conditions during the stabilisation phase.At a COD concentration of 400 mg/L,a Cr(Ⅵ)concentration of 70 mg/L and an HRT of 3d,the CW-MFC had the best water purification and power production capacity and still outperformed the CW,with a maximum COD removal rate of 92.70%,a maximum Cr(Ⅵ)removal rate of 97.39%,a maximum output voltage of 500 m V and a maximum power density of 35.39 m W/m~3.(2)Bioelectricity production combined with Cr(Ⅵ)can promote the removal of dissolved organic carbon(DOC)from the effluent and each components,and bioelectricity production combined with Cr(Ⅵ)can promote the removal of hydrophilic organic matter(HIS),hydrophobic basic organic matter(HOB)and hydrophobic neutral organic matter(HON)much more than Cr(Ⅵ);bioelectricity production combined with Cr(Ⅵ)can promote the removal of unsaturated macromolecular organic matter,and can preferentially remove humic and aromatic substances in hydrophobic acid organic matter(HOA)and HON;the degradation of small molecules substances by bioelectricity production combined with Cr(Ⅵ)is higher than that of humic and aromatic macromolecules.The fluorescence intensity of the effluent and fractions is mainly derived from proteins and fulvic acids,and bioelectricity production combined with Cr(Ⅵ)is effective in removing proteins,fulvic acids and humic acids in wetlands.The effluent contains a large number of alkanes and olefins,and bioelectricity production combined with Cr(Ⅵ)can facilitate the removal of simple and complex unsaturated organics from the water,with bioelectricity production playing a leading role.(3)Cr(Ⅵ)can increase the diversity and stability of microbial communities in anode and cathode,while bioelectricity production can promote the concentration of the anode community and increase the stability of the cathode community,and bioelectricity production combined with Cr(Ⅵ)can increase the difference of the anode or cathode community and cause a certain degree of differentiation of microorganisms.Proteobacteria in the anode microbial community are the typical electrogenic phylum,and Geobacter in the Proteobacteria is the main electrogenic genus.Bioelectricity production combined with Cr(Ⅵ)can promote the growth of Proteobacteria and Geobacter,but the long-term accumulation of Cr(Ⅵ)will inhibit their continued growth.Chloroflexi was the most competitive of the cathode microbial communities,and bioelectricity production combined with Cr(Ⅵ)inhibited the total abundance of Longilinea,Geobacter and Syntrophobacter.