Influence of operational parameters on the performance of domestic wastewater treatment in a single-stage algal-bacterial column photobioreactor

This study evaluated the performance of a single-stage photobioreactor (PBR), under varying hydraulic retention times (HRT) (4, 3 and 2 days), biomass concentrations (2.7 and 1.6 g TSS L −1 ) and illuminated surface/volume ratios (17.8 and 26.7 m 2 m −3 ) in a continuous system operated for 192 days. The system achieved removal efficiencies of Total Organic Carbon of 94–96 %, Total Nitrogen of 92–97 % and phosphate of 91–100 % regardless of the operational conditions. N-NH 4 + removal was primarily driven by assimilation into algal-bacterial biomass. Nitrate and nitrite accumulation in the cultivation broth was not observed and N 2 O generation was negligible. Increased light availability boosted biomass productivity up to 335.7 ± 77.8 g m −3 d −1 . The reduction in biomass concentrations from 2.7 to 1.6 gTSS L −1 decreased microalgal concentration and diversity, particularly affecting filamentous bacteria. These results demonstrate that a single-stage PBR can achieve performance comparable to conventional two stages anoxic-aerobic photobioreactors, while being more cost-effective and sustainable, highlighting its potential for advanced wastewater treatment and resource recovery. • Reducing hydraulic retention time boosted carbon and nitrogen removal over 130 %. • Short solid retention time prevented nitrite accumulation, favoring nitrogen uptake. • N 2 O emissions were undetectable below 2 gTSS L −1 of biomass concentration. • Higher light intensity maximized inorganic carbon removal (38.9 mg L −1 d −1 ) • Scenedesmus outcompeted Pseudanabaena under high surface-to-volume ratio.