Treatment of olive oil industry wastes

The waste products derived from olive oil extraction are an aqueous effluent (vegetation water) and a solid residue, mainly containing the olive skin and stone (olive husk). Biological purification of the vegetation water is particularly difficult because it contains solids in suspension, and a high concentration of polluting organic compounds and mineral salts. In addition, since the recovery of oil by solvent extraction from the olive husk is no longer a profitable process, the olive husk has become a waste product that must be disposed of. In this work, samples of vegetation water (VW) from olive oil mills were separated by evaporation into an aqueous liquid (80-90% of the initial volume), that could then be purified by a traditional biological process, and a residue in which about 98% of the organic load was concentrated. The properties of the concentrated VW residue and of the olive husk suggested the possibility of using a mixture of the two as an efficient fuel to provide the heat for the evaporation stage. (C) 1998 Elsevier Science Ltd. All rights reserved.