[Changes of sludge characteristic in start-up process of UASB treatment for highly sulfate-containing wastewater]

Changes of sludge characters in a sulfate-reducing UASB reactor during the 243 day of domestication process were tracking comparison. Results showed the average diameter of granular sludge in initial domestication stages decreased to 0.99 mm compared with 1.82 mm of incubating sludge, but which was found to be increasing along with the enhance of the loading rate of reactor, the shorten of HRT, and the acceleration of hydraulic up-flow velocity. N2 stripping was used to remove H2S produced in the reactor, and the average diameter of granular sludge increased to 1.51 mm quickly when N2 stripping with the flux of 60 mL x min(-1) was used, but it decreased when the flux of N2 improved to 100 mL x min(-1). Differences in average diameter among granular sludges in different height of the reactor became unconspicuous through continuous stripping. Changes in the MLVSS and the ratio of (MLVSS/MLSS) displayed similar trends, for which firstly decreased in the earlier period then increased to 33.59 g x L(-1) and went up to 49.72 g x L(-1) steadily in the later stage, and then raised from 0.36 to 0.50 subsequently. Sulfate reduction efficiency improved from 30% to 95%, which was strongly correlated with the MLVSS (r = 0.918, p = 0.003). Scanning electron microscope analysis showed inoculating sludge was coarse and incompact, and with the dominant species of filamentous bacteria, bacillus, cocci, but granular sludge with dense microorganism community structure were observed, and in which vibrio and bacillus were the dominant species.