MIZUNO Osamu Tohoku university, Engineering Research Associate, 工学部, 助手 (90271882)
MIYAHARA Takashi Tohoku university, Engineering Research Associate, 工学部, 助手 (70239432)
LI Yu-you Tohoku university, Engineering Associate Professor, 工学部, 助教授 (30201106)
The inhibitory effects of six kinds of aromatic compounds (benzoate, phenol, catechol, resorcinol, hydroquinone, phloroglucinol) on the acetotrophic methanogenesis were investigated by batch anaerobic toxicity assays. Concomitantly, the degradation characteristics and metabolic pathway were clarified by batch anaerobic toxicity assays using anaerobic sludge acclimatized to phenol. Based on the results, the following conclusions can be made :
1)The relative methanogenic activity remaining after addition of aromatic compounds decreased with an increase in the concentration of all aromatic compounds tested. The concentrations (IC_<50>) of benzoic acid, phenol, catechol, resorcinol, hydroquinone and phloroglucinol resulting in 50% inhibition of methanogenic activity were 49.2,18.6,22.7,27.7,40.0, and 51.6 mmol/L,respectively.
2)For all the phenolic compounds tested, a good correlationship between their inhibition effect and hydrophobicity was observed, and the logarithm of the octanol/water partition coefficient (logP), an indicator of hydrophobicity, was found to be correlated with the inhibition of methanogenic activity, according to the following equation : logIC_<50>=-0.283 logP+1.68 (n=5, r^2=0.953)
3)The effect of phenol on the anaerobic degradation rate of phenol was represented by Haldan equation. The values of k, K_s and K_i as kinetic parameter were 0.096hr^<-1>,1128mg/L and 188mg/L,respectively. Phenol was metabolized primarily into transformed into benzoate. Benzoate was further converted to fatty acids which are subsequently mineralized to acetate and hydrogen. Benzoate and acetate were major metabolites of anaerobic degradation of phenol.