Figure 2
Biogas production profile of pretreated and un-pretreated sludge bioreactors. Efficiency of biogas production in (A) the pretreated sludge bioreactor is significantly higher than (B) the un-pretreated sludge bioreactor, giving rise to a 7.71-fold difference in the produced volume at day 8. (C) The cumulative methane production was 389.8 mL-CH4/g VSS-added using pretreated sludge as substrate, 3.78 times of that with un-pretreated sludge (103.2 mL-CH4/g VSS-added) as substrate. Figure 2 (D-E) display methane and carbon dioxide percentages produced by (D) pretreated and (E) un-pretreated sludge bioreactor, respectively; while methane is the major biogas component in both reactors, the methane content was increased by 19.3% with a decrease in carbon dioxide content by 60.9% after pretreatment.