Effect of 2,4-dichlorophenol on the production of methane from anaerobic granular sludge during anaerobic digestion through spectroscopy analysis

Chlorophenols in urban high organic wastewater increases, which plays an inhibitory role in the process of anaerobic fermentation and methanogenesis. The release rules of extracellular polymers (EPS) and soluble microbial products (SMP) and the production of methane from anaerobic granular sludge were evaluated by spectroscopic analysis. The methane production was reduced by 21.6%, 41.4% and 50.5% respectively by adding 2,4-DCP of different concentrations (25, 50 and 100 mg/L). Activity tests of methanogenic functional enzymes indicated that F420 was more susceptible to the toxic of 2, 4-DCP than Acetyl-CoA and NADH. The decrease in methane production was due to the reduction in the activity of conversion enzymes rather than the loss of crucial precursors for methanogenesis. 2,4-DCP disintegrated the protein 'shell' of anaerobic granular sludge by destroying alpha-helix and beta-sheet structures. After the protein 'shell' in EPS was destroyed, 2, 4-DCP entered the interior of granular, which inhibited the activity of functional enzymes and affected the process of acidogenesis and methanogenesis. At the same time, due to the partial rupture of the cells after being affected by the toxicity of 2,4-DCP, the protein material could be dissolved into the aqueous phase and complexed with 2,4-DCP to reduce the toxic effect of 2,4-DCP.