Studies conducted during 1997–2002 in Jastków in the Lublin province investigated the use of a pond to remove contaminants from partly purified sewage discharged from a household soil-plant treatment plant. The pond (area 1190 m², mean depth 0.8 m) is situated in the bottom of the Ciemięga river valley and is supplied with pressure water. The water plants of the pond belong to the most eutrophication-resistent plants and play an important role in the treatment of household sewage by creating very good conditions for further elimination of the load of contaminants from the sewage discharged from the soil-plant bed. The studies showed that the pond plays a purifying function. The values of the analysed indicators of contamination are significantly lower for the water from the pond than for the sewage discharged from the soil-plant bed. The average values of COD_Cr and BOD₅ make it possible to include the water of the pond in purity class II or III. Only the mean concentrations of total phosphorus in this water exceed the norm for class III. The studies suggest that ponds should be used as an additional purifying element accompanying soil-plant sewage treatment plants.

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