Excess reactive phosphorus (PO4) in waterways can lead to eutrophication. A low-cost approach to reducing PO4 levels in surface water was evaluated using the alum-based water treatment residual (Al-WTR) or Al-WTR augmented with powdered activated carbon (PAC-WTR). Batch adsorption-desorption and continuous flow column experiments were performed to assess the specific adsorption capacities under various concentration and flow conditions. Both Al-WTR and PAC-WTR exhibited the ability to adsorb PO4. The overall, cumulative sorbed amount after a 28-d desorption step for Al-WTR was 33.93 mg/kg, significantly greater than the PAC-WTR value of 24.95 mg/kg ( p < 0.05). The continuous flow column experiments showed a theoretical PO4 uptake of 9.00 mg/g for Al-WTR and 7.14 mg/g for PAC-WTR over 720 h. When surface water was used, the Al-WTR and PAC-WTR columns removed 67.4％and 62.1％of the PO4, respectively. These results indicated that Al-WTR was more effective for in-field evaluation.