Evaluation of the microalgae-based activated sludge (MAAS) process for municipal wastewater treatment on pilot scale

The microalgae-based activated sludge (MAAS) process was evaluated regarding the removal efficiency of organic matter and nitrogen from physiochemically pretreated municipal wastewater at different hydraulic retention time (HRT) on pilot scale. Additionally, the interplay between the algal and bacterial consortium was evaluated regarding the ability of the algal consortium to provide oxygen for bacterial oxidation processes. The results showed in general high organic matter (COD removal 75-90%) and total nitrogen (40-50%) removal at all HRTs (6, 4 and 2 days). The dissolved oxygen (DO) concentration was maintained stable at 6 days (6.04±0.47 mg L-1) and 4 days (4.24±0.62 mg L-1) HRT. However, the DO significantly declined at 2 days HRT due to loss of biomass at the high influent flow in the sedimentation unit. Nevertheless, the MAAS process functioned as a symbiotic algal-bacterial system with bacterial organic matter oxidation and nitrification and algal nutrient removal