In this study, the feasibility of utilizing an algal photo-bioreactor as a polishing step for secondary treated wastewater was tested. Algal photo-bioreactors utilize the interaction of bacteria and microalgae, which offers an eco-friendly and lower energy consumption technology for nutrient removal and biomass production. The pilot plant in this study consists of an algal photo-bioreactor with an effective volume of 0.188 m³ and a lamella settler, constructed and operated at Zenin Wastewater Treatment Plant, Giza, Egypt. The pilot plant was operated for about 112 days under continuous flow conditions at ambient temperature. The effect of hydraulic retention time (HRT) on the rate of removal of organics and nutrients was investigated at a fixed solid retention time of 15 days. The photo-bioreactor was continuously illuminated with light obtained during the day from sunlight and at night from incandescent lamps. HRT of 16.1 hours had the best overall organic and nutrient removal efficiency. However, from an economic standpoint the optimum applied load was 50 g N/d/m³ and 22 g P/d/m³ for ammonia and phosphorus, respectively. These applied loads correspond to HRTs in the range of five to six hours and expected removal efficiencies above 85% and 70%, respectively, for ammonia and phosphorus.