Phosphorus (P) discharge from wastewater treatment plants into the environment contributes to eutrophication issues. Reactive media filters represent an effective, simple and cost-effective solution to decrease the P content. Previous research used various experimental designs and often synthetic wastewater, making assessment of real-world performance difficult. This study assesses the impact of the hydraulic retention time (HRT) on P removal using real wastewater to refine design criteria for full-scale installations. Four media were compared in column experiments for >200 days. Different HRTs were applied and initially the media achieved low P effluent concentrations of >0.1 mg/L PO4-P, increasing over time. Best P removal was observed for the highest HRT with on average >99%. HRT was seen to be the driving factor for P removal rather than media capacity. Three of the four materials showed pH levels above 12 initially, decreasing over time. Water quality parameters, including organics, solids and metals, were monitored. In-depth analysis confirmed formation of calcium phosphate precipitation on the media's surface. The results suggest the importance of an optimal HRT to achieve high P removal and show that the reactive media application is an appropriate technology for P removal on small sites if the elevated pH is addressed.