The intensity of phosphorus elimination in the annual cycle was examined in a complex of fishponds occupying the total area of 40 ha, fertilized with biologically treated municipal sewage. During the winter season a decrease in phosphorus concentrations by approximately 30% in fishponds was observed with ten days’ sewage retention in the non-stocked ponds and at low water temperatures. During the summer season, phosphorus elimination from sewage discharged to the ponds periodically exceeded 80%. The highest rate of phosphorus elimination in the ponds was recorded in the second half of the vegetative period, concurrent with slower growth of phytoplankton and increased water turbidity.

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