Alternative treatment strategy for tannery water reuse and material recovery.

ABSTRACT

Most tanneries use conventional systems for treatment of the mixture of all production effluents. Such an approach makes it possible to meet environmental regulations, but because of the high cost of the treatment facilities, its implementation has been scarce, especially in developing countries. With the waste reduction-elimination concept in view, an alternative strategy for water management is proposed based on individual treatment of the effluents from different processing steps to obtain multiquality recycled water for various reuse purposes, materials recovery and complete reuse of treated water. The methodology includes a database generation of tanneries in Mexico, a mass balance and pollution index determination, formulation of water management scenarios and technical-economical evaluation. To replace the traditionally used sulfde oxidation, a sulfide recovering was proposed. Chromium, grease and protein recovery were considered too. The proposed alternative allows a 90% fresh water reduction, the recovery of more than 95% of chromium and sulfide, 90% of grease, 65% of protein and zero discharge of wastewater. Simultaneous implementation of various water saving methods using in-house wastewater treatment techniques for recovering of chemicals and sub-products reduces substantially the cost of water management.