Effects of Initial pH on Bio-hydrogen Production from Alkaline Pretreated Municipal Sludge

Great attention has been paid to the increasing amount of municipal sludge generated from wastewater treatment plants due to its potential risks to the surrounding environment. The municipal sludge, which mainly composed of polysaccharides, proteins as well as abundant groups of microorganisms, has been proved to be a promising biological material for hydrogen production by anaerobic fermentation. The tests systematically investigated the effects of initial pH on bio-hydrogen production from alkaline pretreated municipal sludge. The results showed that both hydrogenogen and methanogen were inhibited at the initial pH 2 to 4, which resulted in little hydrogen production. The methanogen inhibition was obvious by the rate of 94-98 % at the initial pH 5. The relatively high hydrogen production appeared at the initial pH 5 during the fermentation using the alkaline pretreated sludge at pH=12.0, and the corresponding pH at the end of fermentation was from 5.0 to 6.0, which was good for hydrogen production from saccharide. The hydrogenogen and methanogen could be promoted and the lag phase for hydrogen production could be shorten at the initial pH 6 to 10, however the corresponding hydrogen production was quite low. It also could be concluded that the alkaline pretreated sludge with initial pH 12.0 gave the highest hydrogen production, and the initial pH 12.0 for the alkaline pretreated sludge could inhibit methanogen growth and meanwhile maintain a high activity of the hydrogenogen.