Treated municipal wastewaters as a sustainable resource of water for the leather industry

The leather industry employs large amounts of water in unit operations of the tanning process which occurs in an aqueous medium. Identify strategies to minimize the quantity of water used in the wet stages of the leather processing is necessary in order to increase the sustainability of this compartment. In the present work, an integrated pilot scale membrane system (membrane bioreactor unit (MBR) coupled to nanofiltration (NF)) was developed for municipal wastewater reclamation. Its performance was evaluated and designed to meet the water quality criteria in view of its reuse in the tanning process. The feasibility of using reclaimed wastewater in the different wet phases of the tanning process (beamhouse, tanning, re-tanning, dyeing, fatliquoring) for manufacturing of calf skins was investigated on pilot scale. The results showed that the combination of MBR and NF treatments applied to municipal wastewaters is adequate for recovering water with low hardness, very low Fe, Mn and ammonium levels as required by tanneries. The pilot-scale tests demonstrated the technical feasibility of using the reclaimed water in the tanning process. The wet-blue leathers produced with treated water and with softened tap water did not show any considerable differences in terms of physical and sensorial properties and their quality fully satisfied the tannery specifications. The results indicate the use of treated municipal wastewater can be considered a promising solution to reduce the groundwater depletion.