Treatment of wastewaters from the cork process industry by using ultrafiltration membranes

Wastewaters produced in the cork process industry were treated by means of two commercial ultrafiltration membranes with MWCO of 10 kDa and 5 kDa, respectively. Previous experiments were conducted for the evaluation of the water hydraulic permeability of the membranes. Experiments with total recycling of the retentate and permeate streams, as well as experiments in batch concentration with partial recycling of the retentate stream were conducted. In both procedures, the influence of the main operating variables (transmembrane pressure, feed flow rate, temperature and nature of the membranes) on the permeate flux was established. The purification levels reached by the membranes were also evaluated by determining the rejection coefficients referred to several parameters which measure the global pollutant content of the effluent: COD, absorbance at 254 nm, tannic content, colour, and ellagic acid, one of the organic pollutant compounds which is present in this wastewater. Finally, experiments in continuous mode, without recycling of both streams, were also carried out. After the determination of the rejection coefficients, the fouling mechanism of the membranes was established by considering some filtration fouling models which are proposed in the literature.