Release of metals from homogeneous soil columns by wastewater from an agricultural industry.

The effect of discharging olive mill wastewater (OMW) in soils on the release of metals previously retained by them is simulated by leaching homogeneous soil columns with a solution of the residue after passing solutions of Cu or Zn through the columns. The effect of other residues, previously added to the soil as composts in field experiments, on the behaviour observed in the laboratory is also discussed. OMW shows a strong power for releasing the metals retained. Previous addition of a compost made from olive mill sludge and plant refuse to the soil causes a significant reduction of the release of retained metal by liquid OMW. Previous addition of concentrated sugarbeet vinasse causes much less significant effects.