Activity
A specific activity test is used to determine the performance of different specific physiological groups involved in anaerobic digestion.36J44 The specific metabolic activity of granular sludge is measured on defined substrates in batch tests. Specific activity is directly proportional to the relative amount of viable bacteria biomass of the trophic group corresponding to the defined substrate used in the batch activity test.36 High methanogenic activity is one of the characteristics of granular sludge and the specific methanogenic activity (SMA) of granules is typically between 0.5 and 2 g COD (chemical oxygen demand) CH4/g VSS (volatile suspended solid)/day (10-42 mmol CH4/g VVS/day (Table 11). However,the SMA of thermophilic granules has been observed up to 7.1 g COD/g VSS/day (148 mmol CH4/g VSS/day) (Table 11). The specific methanogenic activity of the biomass depends on the energy and carbon source which the granules were grown on. The maximum values are obtained when the test substrate is identical to the growth substrate or if the test substrate is an important intermediate, e.g., H2. The activity of granular sludge can be inhibited by high concentrations of fatty acids. Investigations with thermophilic granules degrading a mixture of acetate, propionate, and butyrate showed that propionate can be inhibitory for the degradation of other volatile fatty acids.161-lm Butyrate degradation was immediately reduced by 50% when propionate was added to a final concentration of 30 mM compared to the maximum activity at 10 mM; and degradation of acetate was immediately inhibited by 50% by adding 25 mM propionate, compared to the maximum degradation rate at 10 mM pr~piona t e . '~' -F'~ur~th ermore, propionate degradation was severely inhibited by the addition of 50 mM acetate to the influent of a thermophilic propionate degrading. UASB reactor. Propionate degradation was not affected by 35 mM butyrate to the infl~ent.'~' A mesophilic UASB reactor degradation acetate was completely inhibited when the reactor was subjected to a pulse of lauric acid above 0.5 mM (0.3 g COD/L). However, the addition of an equivalent amount of calcium to the wastewater prevented inhibition.'15 The calcium could reduce the inhibition, probably by chemically binding the lauric acid and thereby preventing the adsorption of the lauric acid to the cell walls. The absorption of long chain fatty acids to the cell wall has been reported to play an important role in the mechanism
of inhibiti~n.~~ Granular sludge maintains viability without feeding and methanogenic activity can easily be reestablished after the UASB reactor had been shut down for many months.87.139,141
กิจกรรมA specific activity test is used to determine the performance of different specific physiological groups involved in anaerobic digestion.36J44 The specific metabolic activity of granular sludge is measured on defined substrates in batch tests. Specific activity is directly proportional to the relative amount of viable bacteria biomass of the trophic group corresponding to the defined substrate used in the batch activity test.36 High methanogenic activity is one of the characteristics of granular sludge and the specific methanogenic activity (SMA) of granules is typically between 0.5 and 2 g COD (chemical oxygen demand) CH4/g VSS (volatile suspended solid)/day (10-42 mmol CH4/g VVS/day (Table 11). However,the SMA of thermophilic granules has been observed up to 7.1 g COD/g VSS/day (148 mmol CH4/g VSS/day) (Table 11). The specific methanogenic activity of the biomass depends on the energy and carbon source which the granules were grown on. The maximum values are obtained when the test substrate is identical to the growth substrate or if the test substrate is an important intermediate, e.g., H2. The activity of granular sludge can be inhibited by high concentrations of fatty acids. Investigations with thermophilic granules degrading a mixture of acetate, propionate, and butyrate showed that propionate can be inhibitory for the degradation of other volatile fatty acids.161-lm Butyrate degradation was immediately reduced by 50% when propionate was added to a final concentration of 30 mM compared to the maximum activity at 10 mM; and degradation of acetate was immediately inhibited by 50% by adding 25 mM propionate, compared to the maximum degradation rate at 10 mM pr~piona t e . '~' -F'~ur~th ermore, propionate degradation was severely inhibited by the addition of 50 mM acetate to the influent of a thermophilic propionate degrading. UASB reactor. Propionate degradation was not affected by 35 mM butyrate to the infl~ent.'~' A mesophilic UASB reactor degradation acetate was completely inhibited when the reactor was subjected to a pulse of lauric acid above 0.5 mM (0.3 g COD/L). However, the addition of an equivalent amount of calcium to the wastewater prevented inhibition.'15 The calcium could reduce the inhibition, probably by chemically binding the lauric acid and thereby preventing the adsorption of the lauric acid to the cell walls. The absorption of long chain fatty acids to the cell wall has been reported to play an important role in the mechanismของ inhibiti ~ n. ~ ~ ตะกอน Granular รักษาชีวิตไม่ให้อาหาร และกิจกรรม methanogenic สามารถจะเพลิดได้หลังจากเครื่องปฏิกรณ์ UASB ได้ถูกปิดใน months.87.139,141
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