Use and treatment of olive mill wastewater: current situation and prospects in Spain

Abstract

The characteristics of olive mill wastewater are set out the viewpoint of their pollutant capacity and the problems arising from their tipping in olive-growing areas. The national administration's solutions for preventing pollutions of surface waters are also stated. Special detail is given to the action taken within a research and development program financed by the Spanish Government and the EEC through the Commission MEDSPA 89 for the technical-economic evaluation of different systems for eliminating and treating olive mill wastewater, in order to determine the feasibility of their introduction at industrial level. At the same time the systems currently under evaluation are described: - Intensification of natural evaporation from olive mill wastewater stored in ponds (two systems). - Physical processes using forced evaporation to eliminate the olive mill wastewater, followed by aerobic biological processes or systems of ultrafiltration and inverse osmosis for final treatment of the condensate (two systems). - Application of physico-chemical processes to eliminate the greater part of the organic components of the olive mill wastewaters and the use of aerobic biological processes or systems of ultrafiltration and inverse osmosis for final treatment of the clarified fraction (three systems). - Biological process for the complete treatment of the olive mill wastewaters by the successive application of processes: bioconversion, biomethanisation, aerobic treatment, and physico-chemical treatment. Treatment yields of the order of 99,6% are achieved, at the same time obtaining by-products of commercial interest (one system).