Weak electrostimulation to enhance planktonic and biofilm microbial interactions on complex carbon degradation for biogas recovery

Electrode biofilm and planktonic microorganisms are two important parts in bioelectrochemical system, but the mechanism of planktonic microorganisms affect biofilms is not clear. Waste sludge lysate produced from sludge pyrolysis contains melanoidins as complex carbon source that are refractory. Anaerobic digestion companied with weak electrostimulation is adopted to treat the wastewater and explore the mechanism in electron transfer, biofilm activity and microbial community structure. In the presence of planktonic microorganisms, electrode biofilm still plays a major role that about 70% of organics was removed by biofilm, the energy recovery efficiency increased by 10.81%, and the main electron transfer mechanism of biofilm is unchanged, but extra electron transfer pathway (E_f = 0.404 V vs Ag/AgCl) is generated. More cytochrome is produced in biofilm and charge transfer resistance decreases to facilitate electron transfer. The planktonic microorganisms cause more electrochemically active microorganisms and methanogens enrich in the electrode biofilm to enhance the direct interspecies electron transfer.