COMBINED ANAEROBIC - AEROBIC BIOELECTROCHEMICAL SYSTEM FOR AMMONIUM, SULFIDE AND CARBON REMOVAL FROM ETHANOL STILLAGE

Abstract

The organic matter (as an electron donor) could be oxidized at an anode in the bioelectrochemical systems (BESs), to produce electrons and protons with the biocatalysts of electrochemically active microorganisms. Electron acceptors at the cathode could accept them. By combining an anaerobic digestion reactor with BES, the chemical composition of biogas can be improved - the yield of methane can be increased at the expense of carbon dioxide. If an aerobic reactor is included in this combined system, complete decomposition of organic matter, generation of energy (biomethane) and nitrogen removal is achieved. The efficiency of carbon, sulfide and ammonium ions removal during anaerobic digestion of ethanol stillage in an integrated BES system was studied in 5 modes of operation - without BES, microbial fuel cell (MFC) and microbial electrolysis cell (MEC at 0.6, 0.8 and 1.0 V external voltage). In MEC mode, the gas composition is improved (increased amount of methane to 74 %, vol.), and the content of sulfates and hydrogen sulfide is reduced. At 1.0 V external voltage, 94.1 % removal of organic matter and 90.91 % removal of NH4 + are achieved.