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Nitrogen and phosphorus are involved in many processes on the Planet Earth. Especially in agricultural areas water is contaminated by nutrients, which can cause the eutrophication of surface waters, and other problems. The solution could be use of denitrifying bioreactors, which are used for the reduction of high nitrate concentrations in shallow groundwaters. The subject of the thesis was the study of phosphorus removal in the denitrification bioreactor by steel turnings, which are constituent part of the organic load of the bioreactor. Steel turnings release Fe, which causes the precipitation and adsorption of P. Eight bioreactors were filled with poplar woodchips. To these columns just above the surface were added model water enriched with nitrate nitrogen, phosphate phosphate was added to 4 columns, where two of them were enhanced by the addition of steel turnings upstream of the wood medium. Sampling and the analyses of the samples were determined weekly, determination of the phosphorus, iron and other substances necessary for the detection of processes in the bioreactor was performed. The dependence of phosphorus removal on the bioreactor operating conditions was evaluated based on measured data, and the effect of iron on the biological denitrification process was also assessed. Steel turnings have been found to be effective in removing TP, but it is necessary to solve iron leaching in the future. The concentration of phosphorus was reduced up to 0 mg/l on the effluent from the denitrification bioreactors, efficiency of phosphorus removal reached 100 %. The presence of steel chips had no effect on denitrification speed. The denitrification process was also successful in the phosphorus removal columns. From the point of view of leaching of substances and iron, the removal of N and P seems to be preferable in dry period during stoppage with no water fillings. Shutdown of bioreactors with flooded filling caused high concentrations of leached iron up to 149 mg/l