The impact of contactor scale on the efficacy of a ferric nanoparticle embedded media for phosphorus removal was investigated. Experiments were conducted on columns with diameters between 15 and 500 mm, operated at a fixed empty bed contact time of 4 min and an aspect ratio of bed depth to column diameter of 2:1 to ensure self similarity. The columns contained a ferric nanoparticle embedded media, and treated water containing 4 mg P L-1 to simulate applications of full load removal. The treatable flow before breakthrough, the shape of the mass transfer zone and the capacity were all seen to vary with the column diameter used. A logarithmic relationship was observed between column diameter and adsorption capacity such that the capacity increased from 3.4 to 6.3 mg P g(media)(-1) as the column diameter increased from 15 to 500 mm. Overall the results highlight the importance of considering the scale at which the capacity is measured when assessing the economic suitability of the embedded nanoparticle resin. (C) 2012 Elsevier B.V. All rights reserved.