PRODUCTION OF CLEAN WATER FROM AGRO-INDUSTRIAL WASTEWATERS USING OSMOTIC DISTILLATION

Abdelilah El-Abbassi, Hajar Kiai, Abdellatif Hafidi, Faculty of Sciences - Semlalia, Marrakech, Morocco
Maria Carmen García-Payo, Mohamed Khayet, Faculty of Physics, University Complutense of Madrid, Spain

Abstract

Agro-industrial wastewaters present a serious environmental concern. In this study we are interested to the treatment of olive mill wastewaters (OMW) and producing clean water. Olive oil extraction generates important volumes of toxic and polluting wastewaters. The olive mill wastewaters are seasonally produced with large volumes. Amongst other organic constituents, OMW contain high concentrations of phenolic compounds up to 10 g/L that make, along with the high organic load, OMW hardly biodegradable and phytotoxic. Considering the OMW polyphenols, the osmotic distillation (OD) is a non-destructive process, which makes possible the recovery of these valuable compounds and water. The treatment and concentration of OMW was carried out using microporous polytetrafluoroethylene (PTFE) membranes at 30°C (±0.1°C) with different nominal pore sizes (TF200, 0.2 µm; TF450, 0.45 µm and TF1000, 1µm). Calcium chloride (5 M) was used as osmotic agent in the permeate side. The results show that the PTFE membranes exhibit reasonable fluxes (2.9-4.2 L/h.m2) and a complete retention of the phenolic compounds (separation coefficient =100%). The concentration factors were up to 1.2 after 280 min of OMW processing. Although, when treating OMW in the same conditions but with a difference of temperature between feed and brine, the concentration factor reached 1.9 after 30 hours of operating time using TF200 membrane. The PTFE membranes exhibit a high fouling resistance since the reduction of the water flux at the end of the experiment did not exceed 6%. Distillation on PTFE membrane can be considered as an efficient alternative for the water recycling and the concentration of OMW for further valorization by recovering its phenolic content.

Keywords: Osmotic Distillation; PTFE membranes; Olive Mill Wastewater; treatment; water recycling; phenolic compounds