Dump water contg. suspended pond bottom sediments (500 mg/L) was treated with Fe or At coagulants (content up to 100 mg/L) or anionic or cationic polyelectrolytes (1 mg/L) or with a coagulant-polyelectrolyte mixt. for 30 min in a com. flocculator. The increasing concn. of coagulants resulted in an increase in suspended matter removal as expressed by removal of turbidity (up to 99%) and orthophosphates (up to 70%). The decrease in COD was lower (37.4%) but significant. The polyelectrolytes used alone were not as efficient as coagulants. The combined use of coagulants and polyelectrolyts resulted in formation of bigger and easily sepd. flocks, when compared to alone use of coagulants. The pH decreased from 7.3 down to 6.4 after the treatment.