Kinetics and boundary flux optimization of integrated photocatalysis and ultrafiltration process for two-phase vegetation and olive washing wastewaters treatment

• Simultaneous treatment of effluents of olive mills operating with two-phase technology.
• pH-T flocculation + UV/TiO2 photocatalysis + UF yields effluent apt for irrigation.
• Significant and stable flux (26.5% increment) and minor fouling (28.6% reduction).
• Proposed boundary model fits accurately the UF membrane performance.

In many of the studies available on the treatment or fractionation by membrane technology of the effluents by-produced by olive oil factories, the problem of fouling is not correctly approached or not even addressed. In the present study, the operating framework of a spiral wound polymeric ultrafiltration (UF) membrane module was optimized by the boundary flux theory, which merges both the critical and threshold flux theories for simplification purpose and was formerly validated by the Authors. The raw wastewater, a mixture of olive washing and olive vegetation wastewaters, was pretreated by two processes developed in prior research: pH-temperature flocculation (pH-T F) and photocatalysis with lab-made ferromagnetic-core titanium dioxide nanoparticles under ultraviolet light (UV/TiO2 PC). The organic matter removal during UV/TiO2 PC fitted accurately a two-step first-order kinetic model. Also, the proposed boundary model fits the membrane experimental data with accuracy. Higher boundary flux values were confirmed for batch UF when the feedstream is further pretreated by UV/TiO2 PC (23.3–23.6% increment), and also slightly higher feed recovery and significant minor sub-boundary fouling index α. Moreover, the higher rejection of the organic pollutants (53.3%) permits achieving the standard limits to reutilize the purified effluent for irrigation purposes.