Comparison of chemosynthetic and biological surfactants on accelerating hydrogen production from waste activated sludge in a short-cut fermentation-bioelectrochemical system

Abstract

The effects of chemosynthetic and biological surfactants on accelerating hydrogen generation from waste activated sludge (WAS) is investigated in a short-cut fermentation-bioelectrochemical system. The specific experiments are conducted in a series of completely stirred tank reactors (CSTRs) and single-chamber microbial electrolysis cells (MECs). Results shows that rhamnolipid (RL) lead to a VFAs yield 1.16-fold and 3.63-fold higher over with sodium dodecylsulphate (SDS) and sodium dodecyl benzene sulfonate (SDBS) treatments in CSTRs on 72 h. By contrast, the corresponding conversion efficiency of methanogenesis is inhibited (0.18 ± 0.03% versus 1.89 ± 0.15% (SDS) and 6.63 ± 0.77% (SDBS)), which is beneficial for subsequent hydrogen production in MECs. The distribution of the acidogenesis metabolites is also affected by the types of surfactants, reflected on cascade changing of hydrogen production. Highest hydrogen yield is 12.90 mg H2 g−1 VSS in RL-MECs, which is larger than all values that have been reported for fermentation and single-chamber MECs. Current and electrochemical impedance spectroscopy clearly demonstrate the important role of RL treatment in electron/proton transfer and the internal resistance decrease. This study demonstrate the sustainability and attractiveness of WAS short-cut fermentation-elelctrohydrogenesis, providing a sound basis for sludge stabilization and bioenergy recovery.