Optimisation of the nanofiltration process of residual wastewater from table olives using synthetic solutions for the recovery of phenolic compounds

Abstract

Abstract Synthetic solution of ultrafiltration permeate from brine wastewater from the elaboration process of table olives was used to investigate the simulation and optimisation of the nanofiltration process with the aim of reducing the contents of salt and organic material, as well as maintaining the major phenolic content in the permeate of nanofiltration as a contribution to their possible recovery. The synthetic solution was elaborated by considering the main characteristics of the ultrafiltration permeate of residual brine from table olive fermentation. A response surface methodology – central composite design (RSM-CCD) was used. The efficiency of conductivity (Ec), total polyphenol content (TPC) and chemical oxygen demand rejections (RTPC and RCOD) were the response variables selected. Transmembrane pressure (TMP), cross-flow velocity (CFV) and nanomembrane type (NF270 and NF245) were the independent variables. The range for RTPC was from 0.59 to 3.34%, while the values for Ec were higher than the NF270 membrane, being between 13.63 and 24.13%. The RSM-CCD results indicate that the optimum that satisfies the objectives of the research were: nanomembrane (NF245), TMP (14.43 bar) and CFV (1.50 m/s). This allowed the permeate to keep 97.39% of polyphenol contents and reduce organic material and salts by 52 and 23%, respectively.