Evaluation of pretreatment methods on harvesting hydrogen producing seeds from anaerobic digested organic fraction of municipal solid waste (OFMSW)

In order to harvest high-efficient hydrogen producing seeds, five pretreatment methods (including acid, heat, sonication, aeration and freeze/thawing) were performed on anaerobic digested sludge (AS) which was collected from a batch anaerobic reactor for treating organic fraction of municipal solid waste. The hydrogen production tests were conducted in serum bottles containing 20 gVS/L (24.8 g COD/L) mixture of rice and lettuce powder at 37 °C. The experimental results showed that the heat and acid pretreatment completely repressed the methanogenic activity of AS, but acid pretreatment also partially repressed hydrogen production. Sonication, freeze/thawing and aeration did not completely suppress the methanogen activity. The highest hydrogen yields were 119.7, 42.2, 26.0, 23.0, 22.7 and 22.1 mL/gVS for heated, acidified, freeze/thawed, aerated, sonicated and control AS respectively. A pH of about 4.9 was detected at the end of hydrogen producing fermentation for all tests. The selection of an initial pH can markedly affect the hydrogen producing ability for heated and acidified AS. The higher initial pH generated higher hydrogen yield and the highest hydrogen yield was obtained with initial pH 8.9 for heated AS.