ABSTRACT
Biohydrogen production by anaerobic sludge was studied by using wastewater as substrate in batch process. Hydrogen production potential of different substrate species, as well as the composition of fermentation product in liquid phase, was studied in the batch culture experiments. The hydrogen production and bacterial growth dynamics were also analyzed. The experiment results demonstrated that the optimal substrate was glucose for hydrogen production. It could be obtained maximum cumulative hydrogen production 67.21 L/mol, hydrogen yield 3.23 mol/mol and hydrogen content 49.52%. The butyrate and acetate were main liquid end products, occupied 26.76%-40.49% of acetate, 37.60%-58.07% of butyrate, implying that it is butyrate-type fermentation. Butyrate/acetate could be used as the indicator for evaluating the effectiveness of H2 production, with that the higher butyrate/acetate, the higher the hydrogen yield. ORP was less than -300 mV during fermentation indicating the experiment was anaerobic. A modified Gompertz model can adequately describe the H2 production and bacterial growth.
Subject(s)
Bacteria, Anaerobic/metabolism , Bioreactors/microbiology , Hydrogen/metabolism , Waste Disposal, Fluid/methods , Bacteria, Anaerobic/growth & development , Fermentation , Glucose/metabolism , Hydrogen/analysisABSTRACT
Biohydrogen production by anaerobic sludge was studied by using manure wastewater as substrate, in batch process. The influences of sludge and carbon nitrogen nutrition on hydrogen production, the liquid fermentative products and hydrogen dynamics were investigated. The results indicate both sludge and nutrition were able to enhance the hydrogen production. It can be obtained maximum hydrogen content 50.65%, cumulative hydrogen production 334.80 mL and hydrogen yield per COD 287.10 mL/g from manure wastewater with carbon nitrogen nutrition and sewage sludge. However, the cumulative hydrogen production and the hydrogen yield per COD were only 59.24 mL and 67.05 mL/g from raw wastewater. Acetic acid and butyric acid in the effluent of fermentation occupied 61%-86%. It might be acetic-butyric acid type fermentation in the batch reactor. The more the VFA content, the higher the hydrogen yield. A modified Gompertz model can adequately describe the H2 production.
Subject(s)
Bacteria, Anaerobic/metabolism , Bioelectric Energy Sources , Hydrogen/metabolism , Manure , Waste Disposal, Fluid/methods , Animals , Bioreactors/microbiology , FermentationABSTRACT
Experiments were conducted to select a natural mixed microflora seed source and investigate the effect of temperature and pH on fermentative hydrogen (H2) production from cattle wastewater by sewage sludge. Sewage sludge was shown to have higher cumulative H2 production than other inoculum collected from cow dung compost, chicken manure compost, and river sludge. Experimental results show that H2 production from cattle wastewater was significantly affected by both pH and temperature of the culture. The maximum H2 yield was obtained at pH 5.5. H2 yield and the ratio of butyrate/acetate (Bu/Ac) followed a similar production trend, suggesting that butyrate formation might favor H2 production. The optimal temperature for H2 production from cattle wastewater was 45 degrees C with peak values of H2 production (368 ml), hydrogen yield of 319 ml H2/g chemical oxygen demand (COD) consumed, and butyrate/acetate ratio of 1.43. Presence of ethanol and propionic acid indicated decreased hydrogen production; their concentrations were also affected by pH and temperature. A modified Gompertz model adequately described H2 production and bacterial growth.