This work evaluated the performance of an innovative anoxic-aerobic algal-bacterial photobioreactor coupled with biogas upgrading for the treatment of domesticwastewater via nitrificationdenitrification. The process, which incorporated a biomass settling step followed by recycling to the anoxic tank, was operated at a hydraulic retention time of 2 days, a sludge retention time of approximate to 11 days under a 12 h/12 h light/dark irradiation cycle at 392 mu Em(-2) * s-1. An increase in the removal efficiency of TN from 38% to 81%, NH4+ from 39% to 97%, and P-PO43- from 59% to 64% were recorded when additional CO2 was supplied to the photobioreactor via biogas scrubbing, which supported an almost complete nitrification of the NH4+ to NO3- and promoted microalgae growth (with the subsequent enhancement in N and P assimilation). TOC removal remained constant at 90 +/- 2% regardless of the addition of CO2, while the effluent biomass concentration averaged 26 +/- 12 mg TSS/L. A DGGE-sequencing analysis of the bacterial community revealed the occurrence of 10 phyla, Proteobacteria being the dominant phylum. Finally, the morphological characterization of the microalgae population dynamics revealed a gradual dominance of the genus Scenedesmus, which accounted for 94-100% at the end of the experiment. (C)2016 Elsevier B.V. All rights reserved.