Reduction of waste chrome levels in tannery wastewater: Optimized direct recycling

The chrome tanning process is the most popular tanning method but it results a considerable discharge of chromium to the wastewater. Various processes have been developed to increase the up-take of chromium by the hide with success, but there remains a major chromium discharge to the wastewater. The wastewater from the tanning process can be reused directly or indirectly but these recycling processes can present problems related to the accumulation of undesirable substances (salts, fat, protein, etc.) and irregularities from batch to batch. The present work is devoted to the development of a direct recycling process that associates a high chromium up-take process with recycling to the pickling bath and then disposal of this bath after pickling. A reduction of the chromium offer to between 4.5% and 5.5% is achieved, against typical values of between 7% and 8%. Good results are obtained for chromium discharge to the wastewater especially when the splitting is done in the lime state where values of chromium about 50 mg/L are obtained.