p-Fluoronitrobenzene (p-FNB) was degraded in a novel three dimensional bioelectrochemical system (3D BES) and potentially utilized as carbon source for achieving both nitrate (NO3=AN) and Cr(VI) reduction. For single NO3-AN and Cr(VI) removal, 200 mg L-1 NO3-AN and 100 mg L-1 Cr(VI) could be almost completely converted to N-2 and Cr(III) at current 50 mA. For single p-FNB degradation, 100 mg L-1 p-FNB was completely degraded at current 50 mA. The critical current for defluorination was 40 mA, and the intermediate product p-fluoroaniline (p-FA) tended to decrease when current was higher than 40 mA. When NO3-AN, Cr(VI), and p-FNB were both coexisted in this system, the average NO3-AN, Cr(VI), and p-FNB removal efficiencies slightly decreased with addition of carbon source. Without carbon source, NO3-AN and Cr(VI) removal rates reached 34.45% and 41.38% with 91.02% p-FNB degradation, proving that NO3-AN and Cr(VI) could be reduced by degrading p-FNB in the BES. (C) 2015 Elsevier Ltd. All rights reserved.