[Analysis of hydrogen-production performance in a UASB system at low pH].

This experiment used upflow anaerobic sludge blanket (UASB) with brown sugar water as fermentation substrate and sewage sludge as the initiation sludge of the reaction, which was made into granular sludge by adding activated carbon. Emphasis was placed on assessing the hydrogen production performance of the UASB hydrogen bio-production system in the stable ethanol-type fermentation. Under the conditions that the influent COD was 4000 mg x L(-1), the temperature was (35 +/- 1) degrees C and the hydraulic retention time (HRT) was 8 h, a certain amount of NaHCO3 was added to adjust pH from 3.72 to 3.80, 3.85, 3.94 and 4.04, the hydrogen production rate increased correspondingly from the initial 5.5 L x d(-1) to about 7.0, 8.0, 9.5 and 6.0 L x d(-1), which was improved by 27.27%, 45.45%, 72.73% and 9.09%, respectively. The highest hydrogen production rate and gas yield were observed at pH 3.94. The maximal gas yield was 15.83 L x d(-1), which was 1.75 times as high as the initial production. Meanwhile, the hydrogen production efficiency was 58.05%. This study broke through the lower limit pH value 4.0 in fermentative hydrogen production.