Digestate of Fecal Sludge Enhances the Tetracycline Removal in Soil Microbial Fuel Cells

Abstract

The soil pollution of agricultural lands is increasingly being caused by the widely used antibiotic tetracycline (TC) in the animal husbandry industry. Soil microbial fuel cells (SMFCs) provide a promising strategy for the bioremediation of contaminated soil. However, our current understanding of the bioremediation of TC-contaminated soil by SMFC is still limited. Here, we investigated the influence of fecal sludge (FS) digestate on TC biodegradation efficiency and extracellular electron transfer in SMFCs. The addition of FS digestate was beneficial to electricity generation by SMFC, and thus enhanced the removal efficiency of TC in the SMFC. After 25 days, the SMFC with fecal sludge digestate showed a TC removal efficiency of 64.5%, compared to values of 25.2% and 21.4% observed for a SMFC and an open-circuit SMFC operating without the addition of fecal sludge digestate, respectively. Moreover, the addition of FS digestate was favorable for electricity generation by SMFCs, and the average current density and the maximum power density of the SMFC with fecal sludge digestate were 0.054 A/m3 and 8.85 W/m3, respectively. The enrichment of Desulfuromonas and Pseudomonas in the electrode biofilms might account for their high TC removal efficiency and electricity generation. The SMFC with fecal sludge digestate provides a promising approach for the simultaneous disposal of fecal sludge digestate and the bioremediation of antibiotics-contaminated-soil.