Abstract
The adoption of a new economic model, the circular economy, that promotes closing-the-loop of product lifecycles through greater recycling and re-use, is driving attention to by-products and waste valorisation. Food production chain has been considered one of the main waste producers and therefore several studies have been developed on its by-products and waste valorization, producing a range of secondary raw materials. Membrane technologies can be used for the recovery of valuable compounds such as fibers, pectin, sugars, proteins, and phenolic compounds from agroindustrial wastes.
In this sense, olive mill wastewater (OMW) is one of the main wastes generated during the production of olive oil and represents an environmental problem of this agro-industrial process. It is extremely difficult to treat due to its considerable volume and high organic matter concentration. Its principal components are polysaccharides, sugars, polyphenols, polyalcohols, proteins, organic acids, and oil.
Among them, phenolic compounds represent one of the major factors of the environmental problems caused by OMW. They are present in high concentration and they have different negative effects such as phytotoxicity, toxicity against aquatic organisms, suppression of soil microorganisms and difficulty to decompose. On the other hand, phenolic compounds possess high antioxidant activity that makes them interesting for the food, pharmaceutical and cosmetic industries. Because of that, the recovery of these compounds by different physicochemical methodologies represents an important objective for olive oil industry that will help to obtain interesting extracts and reduce the volume of this industrial by-product.
In this work, the goal was the fractionation of fresh OMW, directly taken from the centrifuges of two-phase olive oil mills. For this goal, and prior to run bench or pilot-scale experiments, a novel screening of microfiltration (MF), ultrafiltration (UF) and loose nanofiltration (NF) membranes was performed. The procedure consisted of filtering the samples of OMW through 0.45 μm membrane filters. After this, the filtered samples were poured into Falcon tubes provided with membranes of different mean pore size (MWCO ranging from 100 down to 3 kDa). Finally, they were subjected to quick centrifugation, after which the total polyphenols concentration, the COD, the electroconductivity and the pH of both the permeate and concentrated fractions of the centrifuged-filtered samples were analyzed in both outlet streams to assess the adequate membrane pore size selection.
