Reuse of olive mill effluents from two-phase extraction process by integrated advanced oxidation and reverse osmosis treatment

In this work, complete reclamation of the olive mill effluents coming from a two-phase olive oil extraction process (OME-2) was studied on a pilot scale. The developed depuration procedure integrates an advanced oxidation process based on Fenton's reagent (secondary treatment) coupled with a final reverse osmosis (RO) stage (purification step). The former aims for the removal of the major concentration of refractory organic pollutants present in OME-2, whereas the latter provides efficient purification of the high salinity. Complete physicochemical composition of OME-2 after the secondary treatment was examined, including the particle size distribution, organic matter gradation and bacterial growth, in order to assess the selection of the membrane and its fouling propensity. Hydrodynamics and selectivity of the membrane were accurately modelized. Upon optimization of the hydrodynamic conditions, the RO membrane showed stable performance and fouling problems were satisfactorily overcome. Steady-state permeate flux equal to 21.1 L h(-1)m(-2) and rejection values up to 99.1% and 98.1% of the organic pollutants and electroconductivity were respectively attained. This ensured parametric values below standard limits for reuse of the regenerated effluent, e.g. in the olives washing machines, offering the possibility of closing the loop and thus rending the production process environmentally friendly.

Effective treatment of olive mill effluents from two-phase and three-phase extraction processes by batch membranes in series operation upon threshold conditions

Production of olive oil results in the generation of high amounts of heavy polluted effluents characterized by extremely variable contaminants degree, leading to sensible complexity in treatment. In this work, batch membrane processes in series comprising ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) are used to purify the effluents exiting both the two-phase and tree-phase extraction processes to a grade compatible to the discharge in municipal sewer systems in Spain and Italy. However, one main problem in applying this technology to wastewater management issues is given by membrane fouling. In the last years, the threshold flux theory was introduced as a key tool to understand fouling problems, and threshold flux measurement can give valuable information regarding optimal membrane process design and operation. In the present manuscript, mathematical approach of threshold flux conditions for membranes operation is addressed, also implementing proper pretreatment processes such as pH-T flocculation and UV/TiO2 photocatalysis with ferromagnetic-core nanoparticles in order to reduce membranes fouling. Both influence the organic matter content as well as the particle size distribution of the solutes surviving in the wastewater stream, leading, when properly applied, to reduced fouling, higher rejection and recovery values, thus enhancing the economic feasibility of the process.