8-羟基喹啉对白菜废弃物厌氧消化特性及作用机制的影响OA

Anaerobic digestion is one of the most important processes to realize the conversion of vegetable waste into carbon-based materials.This study aims to investigate the effects of 8-hydroxyquinoline on methane production,intermediate metabolite conversion,microbial community structure,and electrochemical properties during anaerobic digestion of Chinese cabbage wastes.The low and high concentrations of 8-hydroxyquinoline were also selected to clarify the microbial and electrochemical mechanisms during methane production.Batch anaerobic digestion experiments were conducted with three treatments:a control without 8-hydroxyquinoline,a low-dose treatment containing 50 mg/L 8-hydroxyquinoline,and a high-dose treatment containing 150 mg/L 8-hydroxyquinoline.Each treatment was performed in triplicate at 35 ℃.Biogas production,methane production,volatile fatty acids,and methane-production kinetics were determined to verify the concentration regulation for risk assessment.Microbial community composition was characterized by high-throughput sequencing of the 16S ribosomal RNA gene.Co-occurrence network analysis was used to evaluate potential correlations among bacterial and archaeal taxa.Cyclic voltammetry and electrochemical impedance spectroscopy were applied at the initial,acidification,and peak methane-production stages to assess redox activity and interfacial electron-transfer characteristics.The results show that there was a strong effect of 8-hydroxyquinoline concentration.Compared with the control,the 50 mg/L treatment increased cumulative biogas production from 1 935.00 mL to 2 134.00 mL,and cumulative methane production from 568.80 mL to 693.09 mL,with increases of 10.28%and 21.85%,respectively.In contrast,the 150 mg/L treatment reduced cumulative biogas and methane production to 1 162.00 mL and 211.32 mL,indicating decreases of 39.95%and 62.85%,respectively.Modified Gompertz fitting showed that the predicted methane-production potential increased from 552.03 mL in the control to 673.03 mL in the 50 mg/L treatment,whereas there was a decrease of 198.54 mL in the 150 mg/L treatment.The maximum methane-production rate decreased by 84.41%in the high-dose treatment,compared with the control.The peak of total volatile fatty acids shifted from day 25 in the control to day 28 in both high and low 8-hydroxyquinoline treatments.The proportion reached 30.12%in the 150 mg/L treatment on day 5,while acetate accumulated during the later digestion stage.The high-dose exposure impaired the conversion of acidification products into methane.Microbial analysis showed that the relative abundance of Chloroflexota decreased from 57.16%in the control to 44.13%in the 150 mg/L treatment,while unidentified Anaerolineaceae decreased from 56.65%to 43.47%.These taxa were associated with primary fermentation and degradation of complex organic matter.Although Methanocorpusculum increased from 76%in the control to 83%in the high-dose treatment,the methane yield remained markedly lower,indicating that methanogen abundance failed to directly represent methanogenic activity.Co-occurrence networks showed that there were more nodes and edges in the bacterial network than in the archaeal network.Positive correlations predominated,indicating that substrate hydrolysis,acidification,and syntrophic fatty-acid conversion depended on coordinated interactions among multiple bacterial groups.Electrochemical responses varied among digestion stages.During the initial stage,the charge-transfer resistance values of the control,50 mg/L,and 150 mg/L treatments were 311.9,307.9,and 367.8 Ω,respectively.The high-dose treatment therefore increased the initial charge-transfer resistance by 17.9%,compared with the control.During the acidification stage,the differences among treatments were below 1.9%.At the peak methane-production stage,low charge-transfer resistance in the 150 mg/L treatment failed to obtain high methane production,indicating that electrochemical resistance itself does not represent the overall methanogenic performance.Low-dose 8-hydroxyquinoline promoted methane recovery to maintain the coordinated relationship among substrate degradation,volatile fatty acid conversion,and methane generation.High-dose 8-hydroxyquinoline inhibited methane production to increase the initial electron-transfer resistance.Acidification products were accumulated to reduce key fermentative taxa,and then disrupt metabolic cooperation between fermentative bacteria,syntrophic microorganisms,and methanogenic archaea.These findings can provide a mechanistic basis for risk assessment and regulation in the anaerobic treatment of vegetable wastes with 8-hydroxyquinoline residues.