Treatment of aqueous effluents of the leather industry by membrane processes - A review

A general overview on the potentiality of membrane processes in the treatment of aqueous solutions coming from the leather industry is reported. The wet operations of the leather cycle which can be combined with or modified by membrane processes, such as microfiltration, ultrafiltration (UF), nanofiltration (NF) and reverse osmosis, have been described on the basis of consolidated applications and experimental tests on laboratory and industrial pilot scale. Some new applications are also proposed. The membranes and modules employed for the treatment of the effluents, pretreatment of fluids, cleaning procedures and fluid dynamic conditions in experimental applications are reported and discussed. An outline of direct and indirect energy analysis of tanning operations and the results of a mathematical model applied to the degreasing step are also presented. The integrated membrane processes described permit to rationalize the tanning cycle realizing the recovery and the recycle of several chemicals utilized in the tanneries. A reduction of environmental impact, a simplification of cleaning-up processes of wastewaters, an easy re-use of sludges, a decrease of disposal costs, a saving of chemicals and water and of direct and indirect energy are some advantages coming from the described membrane operations. In the future a wider application of the more consolidated membrane processes in this field is expected in the plant innovation phase of a tanning factory.