Pollution Prevention for Tannery Industry
Recovery, Reuse and Recycle; Process modification; Housekeeping; Material substitution.
Cleaner Production Application
The assessment identified following pollution prevention opportunities at this facility: recycling the spent chrome tanning wastes, oxidizing the sulfide containing wastes, decreasing the volatile organic discharge by changing finishing materials, decreasing water use by batch washing, and using solid wastes from the waste stream as fertilizer.
Chromium recycling. This step allows the collection of the spent chrome tanning solutions, without dilution or contamination, for use in the pickle and tanning process. Since the tannery also tans splits, the spent chrome tanning solution can be used here as well. The tanning of splits results in very good fixation of chromium, so the concentration of chromium in the final effluent should meet effluent regulations. This system results in a saving of about 25 percent in the chromium chemicals used.
Solvents. The suppliers of finishing products have developed water-based lacquers with significantly lower volatile solvent contents. These materials are now widely accepted as quality products, and their use is strongly advised.
Process Water. In some hide wetting processes there is an opportunity to recycle the final rinses. The final rinse wastewater in this process is compatible with fluids used for the first wetting of the hides.
Solid Waste. Elimination of solid leather waste discharges through the use of trimmings in reconstituted leather will ease the burden on landfills.
Capital Intensive Modifications. Eliminating sulfides from the effluent is very important, as they will corrode pipes, cause objectionable odors, and may cause fatal accidents. The sulfide-lime solution, and washes from this process, can be collected without contamination from other solutions. These collected wastes can be placed in a tank and the sulfides oxidized by air with a catalyst.