*The method of regenerating phosphorus from wastewater, especially from sludge water, uses biochar, the sorption capacity of which is saturated with iron from a solution prepared by dissolving ferrous scrap in HCl or 10% FeCl3 solution and then neutralizing the filter with 5% NaOH solution and subsequent washing with water. After washing the biochar saturated with iron with clean water, the purified water is pumped through the biochar from the sewage treatment plant, to which phosphorus is collected. The phosphorus thus captured is then used as a fertilizer with freely available phosphorus for plants.