The aim of the paper is to evaluate the usefulness of opoka rock and reactive material made of it to remove phosphorous from surface water and wastewater. Presented results concern the effects of calcium (Ca) contamination in the reactive material (heated opoka) and it impacts on the value of the maximum sorption capacity Smax. Six batches of material (O1-O6) which come from deposits located in Belzec (south-east part of Poland) is characterized by variable amounts of Ca, which is 238,6-520,1 g∙kg-1. The maximum sorption capacity Smax estimated by Langmuir isotherm model equals 12,3-25,5 mg P-PO4 g-1∙kg. To assess the relationship between the content of Ca, Fe Al and Mg in composition of the reactive material and its ability to retain phosphorus correlation coefficients was used and showed that calcium (Ca) is associated with phosphorus sorption capacity (r=0.99126). Also, Fe2O3 and Al2O3 content have an impact on the ability to bind phosphorous. In contrary, the contamination of MgO has no significant effect on the value of Smax.