Reduced energy consumption during low strength domestic wastewater treatment in a semi-pilot tubular microbial electrolysis cell

The present study examines the effect of the organic loading rate and the configuration of a semi-pilot modular microbial electrolysis cell (MEC) on the energy consumption during domestic (dWW) wastewater treatment. The MEC reactor consisted of twin tubular units hydraulically connected in series and was able to reduce up to 85% of the chemical oxygen demand (COD) concentration of the influent dWW at a relatively low energy consumption (1.6 kW h kg-COD−1). Hydrogen production was limited by the reduced amounts of organic matter fed into the reactor and the poor performance of the cathode.Overall, the results identified both an organic loading rate (OLR) threshold that makes the use of MECs for dWW treatment feasible in terms of energy consumption and COD removal efficiency and an OLR threshold that justifies the operation of two MECs in series to provide the required degree of COD removal.

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► A modular MEC was able to reduce up to 85% of the COD of a real domestic wastewater.
► Hydrogen production became limited by low organic loads.
► Net energy consumption was lower than that associated to aerobic WW treatment.
► WW treatment by MECs in series may become feasible at OLRs above 0.67 g La−1 d−1.
► OLRs above 0.1 g La−1 d−1 would justify the use of MEC for WW treatment.