Effects of Long-china Fatty Acids on Methanogenic Activity of Granular Sludge and the Interactions

The toxicity of caprylic acid, capric acid and lauric acid to anaerobic granular sludge as well as the influence of capric acid on toxicity of caprylic acid and lauric acid were studied in batch assays. The results showed that caprylic acid, capric acid and lauric acid had strong inhibition on methanogenic activity of anaerobic granular sludge. The concentrations of three long -chain fatty acids(LCFA)which inhibited 50 % of maximum specific methanogenic activity(IC50 )of anaerobic granular sludge were 5 .6, 1 .9, 4. 6 mmol·L- 1 respectively, among which carpic acid was the most toxic. The presence of capric acid enhanced the inhibitory effects of caprylic acid the lauric acid. The synergistic action of capric acid was found when combined with caprylic acid and lauric acid. With the presence of capric acid, the IC50 values of caprylic and lauric acid deceased obviously.