Sustainable olive-oil mill wastewater treatment by distillation using a parabolic trough solar collector

Abstract

The olive oil industry, although among the most important sectors in the Mediterranean basin, causes huge environmental problems due to the discharge of polluting wastewater. The treatment of olive-oil mill wastewater is therefore at the crossroads of many concerns and is a major challenge for sustainable development. This study focuses on the exploitation of a parabolic trough solar collector as a clean source of energy for sustainable olive-oil mill wastewater treatment. A conical coil heat exchanger immersed in an olive-oil mill wastewater distillation reservoir is coupled with a parabolic trough solar collector. The productivity, environmental impact, and profitability of the proposed prototype are experimentally evaluated. A comparative study and a Physico-chemical characterization of filtered and unfiltered olive-oil mill wastewater are conducted to assess their potential reuse. A simulation using a spray-type falling film evaporation approach is realized to achieve numerical optimization. The obtained results show that the use of a parabolic trough solar collector allows more heat gain to be transferred into the distiller, enhancing system productivity, and decreasing temperature fluctuation compared to the traditional solar distiller. A significant reduction of 95 % to 97 % of phenolic compounds is observed for the distillate. The overall analysis reveals that the 26.6 m2 parabolic trough solar collector aperture area has generated 19 MWh of thermal energy throughout the olive oil post-production phase, which led to the avoidance of about 12,660 kg (eq) of CO2 emissions, while the Levelized cost of heat was 0.3 $/kWhth.