[Effects of initial pH on hydrogen production from acid pretreated municipal sludge]

A series of batch tests were conducted to investigate the effects of initial pH on bio-hydrogen production from acid pretreated municipal sludge. The pH of sludge was first adjusted to 2.0, 3.0, 4.0 and 5.0, stood by for 24 h in a refrigerator at 4 degrees C, then adjusted to pH 2.0-12.0 respectively before using as the substrates for batch experiments. The results showed that the acid pretreated sludge with initial pH 11.0 gave the highest hydrogen production, and the corresponding accumulative hydrogen for sludge (dry basis) pretreated at pH 2.0, 3.0, 4.0 and 5.0 were 0.59, 1.83, 0.50 and 0.56 mL/g respectively. Hence, it could be seen that the initial pH 11.0 for the acid pretreated sludge should be the optimum pH range for promoting the growth of dominant hydrogen-producing anaerobes, while inhibiting hydrogen-consuming anaerobes. Meanwhile it also could be concluded that both hydrogenogen and methanogen were inhibited at the initial pH 2.0 to 4.0 and 12.0, which resulted in a low hydrogen production. Although the hydrogenogen and methanogen could be promoted at the initial pH 5.0 to 9.0, the corresponding hydrogen production was still quite low.