Inhibition of volatile fatty acid production in granular sludge from a UASB reactor

Inhibition of volatile fatty acids (VFA), namely acetate, butyrate, and propionate, on the activity of acetoclastic methanogens within a full-scale upflow anaerobic sludge blanket (UASB) reactor was investigated using specific methanogenic activity (SMA) test. SMA tests were carried out at acetate concentrations in a range of 1000-25,000 mg l(-1), butyrate concentrations in a range of 3000-25,000 mg l(-1) and propionate concentrations between 500-10,000 mg l(-1). Maximum potential methane production (PMP) rates were obtained as 389 ml CH4 gTVS(-1).d(-1) at 3000 mg l(-1) acetate concentration, 432 ml CH(4)gTVS(-1).d(-1) at butyrate concentration of 5000 mg l(-1), and 162 mlCH(4) gTVS(-1).d(-1) at 1000 mg l(-1) propionate concentration. App. 50% and 100% inhibition occurred at acetate concentrations of 13,000 mg l(-1) and 25,000 mg l(-1), butyrate concentrations of 15,000 mg l(-1) and 25,000 mg l(-1), and propionate concentrations of 3500 mg l(-1) and 5000 mg l(-1), respectively.