The surplus of phosphorous in surface water leads to increasing its productivity, and makes the water unable for economic, recreational and natural use. One of the method for removing phosphorus from water bodies is to use reactive materials, which are referred as adsorbents or sorbents and specially interact with targeted chemical species such as phosphate ions. The aim of this study is to characterize the decision-making process of selection of reactive material for removing phosphorus from water and wastewater, on the example of lightweight aggregate Pollytag®. The lightweight aggregate Pollytag® is made by granulation and sintering of fly ash in temperature of 1000–1350 °C. Laboratory tests showed that Pollytag® is characterized by good sorption (32,24 mgP-PO4·g-1) and can be used as a phosphorous reactive material for high concentration of phosphorous (above 10 mgP-PO4·L-1). Sorption capacity of reactive material should be verified by column and full-scale experiment.