Investigations on dynamics of <phosphorus> and <nitrogen> reduction in the <UCT model> system were conducted. After three-week adaptation period, population of activated sludge microorganisms indicated capacity for excessive phosphorus uptake. Source of carbon in synthetic nutrient medium was then sodium acetate (0,5g/l), the concentration of PO4 - 30 mg/l and the NH4 concentration - 60mg/l. At the second stage of the studies the PO3/4 concentration was 15 mg/l in inflow., with increased up to 40 mg/l under anaerobic conditions and decreased to 0,5-1,5 mg/l under aerobic conditions. Togrether wiyth conversions of phosphorus compounds, nitrification processes occurred under aerobioc conditions (12,10-23,15 mg/l) and dentrification in an anoxic reactor (0,1 - 9,5 mg/l). Intensity of the phosphorus and nirogen conversions depended upon biomass loading, degree of recirulation and retention times in the reactors.