Mechanism Of Enhanced Anaerobic Biodegradation Of Phenol By Particle Manganese Dioxide Coupled With Microbial Electrolysis Cell

Phenol is a common toxic compound in industrial wastewater.It is widely used in petrochemical,coke and dyeing and textile industries.It has large emissions to the waterbody and high toxicity.If it is directly discharged into open water,it will cause serious ecological problems.Treatment of substandard phenol-containing wastewater will continue to pollute aquatic organisms and even cause death.Compared with physical,chemical and aerobic biodegradation treatment methods,anaerobic biological phenol degradation has great advantages in terms of cost and efficiency,low cost,simple operation,and the ability to generate biogas resources,etc.The refractory characteristics and biological toxity have become the rate-limiting step in the anaerobic biological of phenol degradation process.These two characteristics can lead to technical problems such as low phenol degradation efficiency,easy collapse of the anaerobic system,and low yield of biomass resources（methane）.A large number of studies have shown that the addition of functional materials and microbial electrolysis cell coupled anaerobic digestion technology（MEC-AD）can effectively promote anaerobic digestion,however,particulate manganese dioxide as an additive,the introduction of MEC-AD technology in anaerobic digestion.There are few studies on biological phenol degradation and methane production.Therefore,this study will introduce particulate manganese dioxide and microbial electrolysis cell technology and couple the two to explore different technical means to enhance anaerobic biological phenol degradation,and study the degradation efficiency and production efficiency.The main research conclusions are as follows:（1）Different doses of granular MnO₂（MnO₂ Ps）（0,50,100,200 mg/g VS）were added to the phenol anaerobic degradation system to study the anaerobic co-metabolism effect of Mn O₂ Ps on phenol.The results showed that compared with the control group（without adding Mn O₂ Ps）,in the VS group with Mn O₂ Ps dosage of 200 mg/g,the phenol degradation rate increased by 37.46%,and the methane production increased by 52.98%.In addition,the change of Mn²⁺concentration is positively correlated with the dosage,and the biological reduction and oxidation of manganese may have occurred.It is verified that Mn²⁺has little effect on the performance improvement of the anaerobic reactor.The results of electrochemical technology and three-dimensional fluorescence spectrum analysis preliminarily showed that Mn O₂Ps stimulated the secretion of humic substances by microorganisms,which was beneficial to extracellular electron transfer（EET）.The sludge conductivity analysis showed that Mn O₂ Ps enriched electroactive microorganisms;The change of coenzyme F₄₂₀ preliminarily indicated that microbial interspecies hydrogen-electron transfer（IHT）was promoted;the analysis of microbial community structure further confirmed that Mn O₂Ps promoted EET and microbial manganese（IV）reduction,and Mn O₂Ps enriched hydrogenophilic Methanogens（relative abundance increased from 56.61%to 61.36%）,acetate-consuming methanogens and Geobacter,and the relative abundance of syntrophic bacteria that can establish electronic links with hydrophilic methanogenic archaea was greatly increased,which can mediate microbial Manganese（IV）-reducing Clostridium was also significantly enriched,and genes for predicted proteins related to metabolic activity were highly expressed.It is shown that Mn O₂Ps facilitates electron transfer between syntrophic bacteria and methanogens,thereby promoting the decomposition of phenol and methanogenesis,while triggering the reduction of biological manganese（IV）to promote the degradation of organic pollutants.（2）In order to make the electrons of oxidized organic matter more effective for resource recovery,a single-chamber microbial electrolysis cell with an input voltage of 0.8v was introduced to further drive the interspecies electron transfer and explore the mechanism of the synergistic effect of the coupling between Mn O₂ Ps and the microbial electrolysis cell.and control mechanisms.Five groups of intermittent experiments were set up:blank group（R1）,MEC group（R2）,Mn O₂Ps group（R3）,MEC/Mn O₂Ps group（R4）and MEC-Open group（R5）.The results show that the MEC/Mn O₂ Ps phenol removal rate and methane production are increased by 24.1%and 21.8%,respectively,compared with the MEC reactor R2 without modified Mn O₂Ps anode,and the current calculation confirms that the additional transferred electrons contribute significantly to the methane production.Small,it is speculated that the main contribution comes from DIET.R2,R3 and R4 all have stable degradation performance in stages I-VI,and the MEC/Mn O₂ Ps group has obvious synergistic effect on the improvement of reactor performance.The concentration of Mn²⁺in the effluent of R4 was always higher than that of R3,and it was preliminarily speculated that MECs promoted the reduction of biological manganese（IV）.Three-dimensional fluorescence spectroscopic analysis showed that MECs and Mn O₂Ps stimulated the secretion of microbial extracellular polymers,which was conducive to extracellular electron transfer;microbial community analysis showed that under the action of MECs,further promoting the reduction of microbial dissimilatory manganese（IV）accelerated the oxidation of phenol,a refractory substance Degradation,MECs/Mn O₂Ps enriched Geobacter and Methanothrix（also known as Methanoseta）to the greatest extent,further confirming that the DIET process in the R4 reactor was promoted,and the promotion of microbial dissimilatory manganese（IV）reduction benefited from the modification of Mn O₂ Ps The enrichment of Clostridium in the MECs reactor also showed that the enrichment effect of the mutualistic bacteria and methanogens in the reactor R4 was the most significant,which showed the synergistic effect on phenol degradation and methane production.