Vatten, vol. 57, nr. 1, pp. 29-37, 0042-2886 Enhanced biological phosphorus removal (EBPR) was studied at the Suomenoja research station in Finland in cooperation with St Petersburg Water and Wastewater Works. The studied process was a mainstream process designed for 10 m³/h with anaerobic and aerobic units. EBPR proved to be a stable and reliable method that endures organic volumetric loads up to 1.0 BOD7 (m³/d). The phosphorus concentration in the outflow was 0.2 mg/l soluble P at the maximum load, corresponding to reduction 97 %. No chemicals were used. The size of the anaerobic compartment should be less than 35 % of the activated sludge basin and the sludge recirculation rate should be close to 100 %. A BOD7:P ratio 18:1 is high enough for EBPR. The phosphorus release rates were 4.0 mg P/(g VSS*h) in the anaerobic compartments, and the accumulation rate was 2.3 mg P/(g VSS*h) at the maximum loading. The accumulation rates were highly dependent on the release rates. Phosphorus concentration increased 0.18 mg/l in the secondary sedimentation due to the release reaction, but most of the released phosphorus was retained by the sludge blanket. EBPR is suitable for the needs of St Petersburg as the water company there cannot use chemical precipitation.