Ultrafiltration for colour removal of tannery dyeing wastewaters

Investigation of ultrafiltration (UF) performance for the purpose of removi ng the colour of three different effluents coming from the dyeing cycle of a tannery industry was carried out using four polyethersulphone (PES) membr anes with molecular weight cut-offs (MWCO) of 40, 10, 5 and 3 kDa. A closed -loop recycle (CLR) and batch (B) modes of operation were used. For the fir st mode of operation, the evolution of permeate flux and colour rejection v s. time of operation was evaluated. For the batch concentration experiments , attention was focused upon the evolution of the rejection and/or concentr ation of colour with the volume reduction factor (VRF) and on the decrease of the permeate flux as a function of VRF for all the membranes under study . All experiments showed the occurrence of concentration polarization and a dsorptive fouling with a pronounced effect for the membranes with higher MW CO. Due to that, the 40 and 10 kDa membranes did not offer a significant re gaining of permeate productivity. High-colour and low-solids rejections wer e observed for all the experiments, showing a marked dependence on the type of effluent used.