Treatment of olive mill wastewaters and spent tanning liquors by integrated membrane systems

In the leather industry membrane processes offer very interesting perspectives for the recovering and recycling of primary resources from spent liquors of unit operations such as soaking, unhairing, degreasing, pickling, dyeing, chromium and vegetable tanning. They can be used also for the treatment of global wastewaters in order to remove the salt content or to separate the biomass from the effluent after chemical-physical treatments (Cassano et al., 2001). Extensive studies involving microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) have been made both on laboratory and industrial scale (Ahmed et al., 2006; Jain et al., 2006; Scholtz and Bowden, 1999). This work aims at giving an overview on the potentiality of membrane processes in the recovery of chromium salts and vegetable tannins from spent tanning liquors in order to obtain tanning solutions which can be reused in the tanning cycle. The potentialities of an integrated membrane system for the recovery, purification and concentration of polyphenols from olive mill wastewater (OMW) were also analyzed.