ACETATE TREATMENT IN 70-DEGREES-C UPFLOW ANAEROBIC SLUDGE-BLANKET (UASB) REACTORS - START-UP WITH THERMOPHILIC INOCULA AND THE KINETICS OF THE UASB SLUDGES

This study focused on the use of thermophilic anaerobic granulae in th e start-up of 70 degrees C acetate-fed upflow anaerobic sludge-blanket (UASB) reactors and the kinetics of granulae grown at 70 degrees C. I n the UASB reactors, chemical oxygen demand removal commenced within 4 8 h of the start-up. The maximum reduction in chemical oxygen demand w as 84% with the feed containing yeast and 71% without a yeast suppleme nt. In the bioassays, the yeast-grown sludge converted 98% of the acet ate consumed to methane as compared to 92% for the sludge grown withou t yeast. The highest initial specific methane production rate (mu CH4) Of the UASB sludges grown at 70 degrees C was 0.088 h(-1) at an aceta te concentration of 4.6 mM. The higher initial acetate concentration w as found to prolong the lag-phase in methane production significantly and to decrease the mu CH4. The half-saturation constant (K-s), the in hibition constant (K-i), the inhibition response coefficient (n), and the mu CH(4)max, calculated according to a modified Haldane equation, were 1.5 mM, 2.8 mM, 0.8, and 0.28 h(-1), respectively. The prolonged starvation of the 70 degrees C sludge (15 days) decreased the mu CH4 f rom about 0.022 h(-1) to 0.011 h(-1) and increased the lag phase in me thane production from 6 h to 24 h as compared to non-starved sludge.