Effects Study Of Micro-current Coupled Magnetic LDH Biochar On Enhancing Anaerobic Degradation Of Phenolic Wastewater

2,4,6-Trichlorophenol（TCP）is a typical chlorophenol compound widely used in industrial production.As an environmental hormone,TCP can accumulate in organisms and has carcinogenic,teratogenic,and mutagenic effects,making it a limited pollutant controlled by the US Environmental Protection Agency,EU countries,and China.Therefore,the efficient and green degradation of TCP in the environment is an urgent issue.Anaerobic biotechnology has outstanding advantages such as wide application range,low energy consumption,and resource recovery,and is one of the most effective green technologies to achieve"pollution reduction,carbon reduction,and efficiency enhancement"of organic wastewater.However,the poor biodegradability of the effluent from traditional anaerobic technology and the instability of the system make it prone to acidification,which has become a research hotspot and technical application difficulty.In this study,magnetic LDH carbon was prepared by combining waste biomass corn stalks with double-layered hydroxide LDH using co-precipitation and high-temperature pyrolysis,and its efficiency in enhancing anaerobic degradation of TCP and its impact on anaerobic sludge performance were studied.Meanwhile,the changes in microbial community and metabolic pathways during the process were analyzed by metagenomic sequencing,and the following conclusions were drawn:（1）Magnetic LDH carbon was prepared using corn stover as the precursor through co-precipitation and high-temperature pyrolysis.The BET results showed that the specific surface area of magnetic LDH carbon was 238.711（m²/g）.XPS spectra confirmed the successful loading of Fe and Mg elements in the material,with Fe and Mg proportions of 5.72%and 1.27%,respectively,and magnetic component Fe₃O₄ was also detected.XRD patterns showed the characteristic absorption peaks of Fe₃O₄ that matched the standard spectra.The FTIR spectra showed the characteristic Fe-O functional groups of magnetic LDH carbon.The leaching concentrations of the main heavy metal ions were found to be lower than the national emission limits through heavy metal leaching tests.（2）Under the action of micro-electricity coupled with magnetic LDH carbon,the performance of anaerobic sludge system for degrading 2,4,6-trichlorophenol wastewater was significantly improved,and the methane production capacity of the system was also increased.The COD and 2,4,6-trichlorophenol removal rates reached71.1%and 75.4%,respectively,which were 2.25 times and 2.5 times higher than those of the original sludge.Compared with the magnetic carbon（R1）and micro-electricity（R2）treatment systems,the COD removal rates were increased by 19.3%and 14.4%,respectively.The maximum methane production was 182 m L/d,about 2.39 times that of the original sludge,and the methane production in the coupled system（R3）was increased by 1.68 times and 1.37 times compared with that of the magnetic carbon and micro-electricity treatment systems,respectively.The treated wastewater had strong biodegradability,with a BOD₅/COD of 0.39,which was conducive to the subsequent biochemical treatment of organic matter removal.Even when the influent phenol load increased to 900 mg/L,the coupled system（R3）still maintained a 64.87%removal rate for 2,4,6-trichlorophenol,and when the p H changed from 8 to 6,the removal rate remained at 50.56%.After the phenol and p H loads were restored,the removal rate of2,4,6-trichlorophenol in the coupled system（R3）could also be maintained at 73%and63%,respectively,which was restored to the pre-impact level.（3）Under the action of micro-electricity coupled with magnetic LDH carbon,the performance of anaerobic sludge was significantly improved.The MLVSS of the coupling system treatment group reached 45.87 g/L after anaerobic treatment,and the protein（PN）concentration increased from 22 mg/（g·MLVSS）on the 20th day to 90mg/（g·MLVSS）on the 90th day.The polysaccharide（PS）concentration increased from8 mg/（g·MLVSS）on the 20th day to 28 mg/（g·MLVSS）on the 90th day.After 90 days of anaerobic system operation,the concentration of coenzyme F₄₂₀ in the micro-electricity coupled magnetic carbon treatment group was 2.79μmol/（g·MLVSS）,which was 2.27 times that of the original sludge.The micro-electricity coupled magnetic LDH carbon treatment group effectively improved the activity of electron transfer system（ETS）in the anaerobic sludge and accelerated the biochemical reaction.Under the action of micro-electricity coupled with magnetic LDH carbon,the microorganisms in the anaerobic sludge were well aggregated,which further enhanced the pollutant removal efficiency and stability of the anaerobic system.（4）Under the action of micro-electric coupling magnetic LDH carbon,the microbial diversity in the anaerobic sludge increased.At the phylum level,Actinobacteria,Chloroflexi,and Planctomycetes were enriched,and the rate of anaerobic degradation of pollutants increased,and organic acid consumption accelerated.At the class level,Anaerolineae,Methanomicrobia,Clostridia,Anaerolineae,and Actinomycetia were enriched.From the archaeal perspective,Methanothrix was enriched,which can produce methane through direct interspecies electron transfer（DIET）with exoelectrogens.Combined with ETS activity analysis,micro-electric coupling magnetic LDH carbon promoted interspecies electron transfer between microorganisms.Based on KEGG analysis,the metabolic pathways of the micro-electric coupling magnetic LDH carbon treatment group were significantly different from the other three groups,with higher abundance in Environmental Information Processing and Genetic Information Processing pathways.In-depth analysis of the abundance of carbohydrate-active enzymes（CAZy）found that GH109and GT41 enzyme abundance increased under the action of micro-electric coupling magnetic LDH carbon.These two enzymes are involved in biomass decomposition and metabolism,cell synthesis,and glycosylation.The abundance of COG functional categories was detected,and it was found that under the action of micro-electric coupling magnetic LDH carbon,the transcription,amino acid transport and metabolism,cell wall/membrane/envelope biogenesis,translation,and carbohydrate transport and metabolism functions were enriched.The enrichment of these functions helps improve the acidic environment of the system,promote pollutant degradation,and methane production.In summary,the coupling of micro-electricity and magnetic LDH-char has a significant enhancement effect on the anaerobic degradation of phenolic wastewater,and shows good stability in response to changes in phenol load and p H.This study established a micro-electricity coupled magnetic LDH-char enhanced anaerobic degradation system based on traditional anaerobic biological systems,which demonstrated high treatment performance.Through analysis of anaerobic sludge properties and metagenomic sequencing,this study provides a more in-depth theoretical understanding of the enhancement of anaerobic degradation of phenolic wastewater by micro-electricity coupled magnetic LDH-char,and offers new insights into the low treatment efficiency of anaerobic biological degradation of phenolic wastewater.