PROJECT DESCRIPTION
BACKGROUND
Brine released from the production of table olives is contaminating soils and water bodies around the Mediterranean. These salty effluents can seep into the ground and spread through rivers, altering local chemical conditions and upsetting ecosystems. The composition and irregular discharge of effluents from the olive industry complicate their treatment. At present, brine is typically accumulated in open ponds where it is left to evaporate. The sludge from evaporation ponds is treated and disposed of in landfills. However, bad practices in the construction and maintenance of these evaporation ponds entail a high risk of pollution due to waste leakage and migration into groundwater and deep soil. Other common brine management techniques include discharging it directly into the sea or injecting it in deep wells, raising in both cases local salt content to levels that cause negative environmental effects.
OBJECTIVES
The main goal of LIFE SOLIEVA was to demonstrate the environmental benefits and economic viability of clean technologies to treat brine from processed table olives. These environmentally sustainable approaches would help recover valuable by-products from the effluents, including salt, and organic compounds called polyphenols that can be of further use in the food industry. Cleaning the wastewater would also make it fit again to process olives. Project partners expected to reduce the overall freshwater demand in this industry by 60%, supporting water conservation objectives set out in the Water Framework Directive. The technologies would also help to use resources more efficiently as described in the EU circular economy strategy. These benefits could ultimately be shared by other agrofood sectors facing brine treatment challenges.
RESULTS
The LIFE SOLIEVA project has designed, constructed and tested an innovative process for treating wastewater from olive production. The project’s solution allows valuable resources to be recovered and re-used as raw materials in line with circular economy principles.
The wastewater is first treated to separate the organic matter from which polyphenols are extracted. The resulting brine could potentially be re-used in the table olive process. If brine is not reused, it is dried in advanced evaporation ponds, eliminating any liquid discharge.
The tests carried out in the pilot plant showed that 30% of the salts can be recovered with a purity of 85% and that 42% of the polyphenols can be extracted with a purity of 7%. Additionally, clean water could also be obtained.
These results were not as good as expected due to two reasons: first, the olive company that hosted the plant could not segregate the different flows of wastewater; second, the regenerated membranes were not able to separate efficiently salts and organic matter to produce the envisaged yield. The results highlighted the technical and regulatory barriers to fully realising the potential of the project’s approach.
Despite these difficulties, functional foods were prepared using the extract rich in polyphenols, which have high nutritional value. Though bitter to taste, eight types of food were produced using polyphenols, with olive pate and chocolate cookies being the most successful.
The benefits of the LIFE SOLIEVA process for the olive industry include: the reduction of water and salt consumption; the minimisation of the area required for the wastewater evaporation ponds, along with the related current environmental risks; and the addition of new income sources related to the recovery of polyphenols. The overall cost of the technology would therefore be 1.2 €/ m3 without the recovery of polyphenols or €9.3 per m3 including the recovery process. These costs are lower than the cost of conventional forced evaporators, which is 15.7 €/m3. Considering that revenues from polyphenols could amount to 10 €/kg, its recovery could be considered to be profitable. However, the project concluded that currently implementation of the solutions is not feasible, while additionally food industry legislation represents a barrier to the use of recovered products.
Further information on the project can be found in the project's layman report (see "Read more" section).
