We characterized anoxic nitrate granules produced by an alternating current biofilm electrode reactor operating at low voltage-low frequency under optimum conditions. Hydrodynamic results revealed that the settling velocity for the granules ranged from 0.12 to 2.85 cm/s, while that of settling velocities ranged from 0.07 to 3.42 cm/s. Granule diameter varied, with a mean mass of 3.65 +/- 1.29 mm and corresponding dry mass ranging from 0.52 to 5.64 mg. Roundness ratio of the sampled granules was determined to be 0.78 +/- 0.11. Integrity coefficient obtained from a shear strength test was 87.05 +/- 2.07% after 2 min and 74.1 +/- 4.14% after 5 min. An adhesion test revealed hydrophilic properties of bacteria. The Most probable number (MPN) value was 2.0 x 10(6) for HDB and 2.0 x 10(3) for ADB. An apoptosis assay by flow cytometry confirmed that the majority of cells (87.7%) were viable and non-apoptotic (Annexin V-PI) and dehydrogenase activity was 15.05 +/- 1.76 mu g TF/mg biomass cm(-2) d. Comparison of seed and granules by I H-1 NMR spectra showed different signals in the range of 0.279-1, 1-1.5, and 1.5-7.5 ppm. Therefore, the biofilm in ACBER can be easily granulated and used to generate dense and fast-settling sludge granules. (C). 2017 Elsevier Ltd. All rights reserved.