Leather & Tanning Industry – Wastewater

Leather tanning or finishing is the conversion of animal hides or skins into leather. Cattlehides, sheepskins, and pigskins are the major hides and skins used most often to manufacture leather.

To a lesser extent, hides and skins of horses, goats, deer, elk, calves, and other animals are also tanned.

Cattlehide or cattle-like hide have short hair and are relatively heavy. Deerskin, horsehide, cow bellies, splits (flesh side of tanned hides which is usually processed separately into suede types of leather) and hides of a similar nature are included in this group.

Sheep or sheep-like skins have long hair and are relatively light. Goatskin and other similar hides are included in this group.

Pig or pig-like skins have short hair or are hairless and are relatively light. This group includes skins which have little hair,
yet typically require unhairing operations. The type of raw material (hides or skins) and the amount of processing already performed on the raw materials received by the facility determines the type of processes necessary to produce finished or partially processed leather. Facilities covered by the Leather Tanning and Finishing regulations are included in SIC 3111 or NAICS 316 which is for Leather and Allied Product Manufacturing.

Contact Aries Tek for removing chemicals from wastewater generated from leather processing and tanning operations…

Leather tanning is the process of converting raw hides or skins into leather. Hides and skins have the ability to absorb tannic acid and other chemical substances that prevent them from decaying, make them resistant to wetting, and keep them supple and durable. The surface of hides and skins contains the hair and oil glands and is known as the grain side. The flesh side of the hide or skin is much thicker and softer. The three types of hides and skins most often used in leather manufacture are from cattle, sheep and pigs.

Tanning is essentially the reaction of collagen fibers in the hide with tannins, chromium, alum, or other chemical agents. The most common tanning agents used in the U.S. are trivalent chromium and vegetable tannins extracted from specific tree barks. Alum, syntans (man-made chemicals), glutaraldehyde, and heavy oils are other tanning agents. Vegetable tannins, aldehydes, oils, and most other tanning methods yield usable leathers from the tanning process alone. In chrome tanning, the reaction with the chromium salts gives a very stable hide fiber that is resistant to bacterial attack and high temperatures, but additional processes are usually performed to produce usable leathers.

Contact Aries Tek for removing chemicals from wastewater generated from leather processing and tanning operations…

Leather Tanning and Finishing Facilities

The table below contains two columns.

  • The first column lists chemicals used by the Leather Tanning & Finishing industry as reported by leather tanners to the US Environmental Protection Agency (EPA).
  • The second column describes which step of the leather tanning process that said chemicals are used.

It is important to keep in mind that every Leather Tanning & Finishing company is unique. Leather tanners and finishers may use all, some or none of the chemicals listed.

Table 1: Chemicals Reported to the US Environmental Protection Agency (EPA)

Chemicals and Chemical Groups
Leather Tanning & Finishing Process
Formic acid
Coloring
Butyl acrylate
Finishing
Butyl alcohol
Finishing
Certain glycol ethers
Finishing
Di (2-ethylhexyl) phthalate
Finishing
Ethylbenzene
Finishing
Methanol
Finishing
Methyl ethyl ketone
Finishing
Methyl isobutyl ketone
Finishing
Methyl methacrylate
Finishing
N-Methyl-2-pyrrolidone
Finishing
Toluene
Finishing
Triethylamine
Finishing
Xylene (mixed isomers)
Finishing
Zinc compounds
Finishing/Retanning
Hydrochloric acid (acid aerosols)
Pickling
Sulfuric acid (acid aerosols)
Pickling
Formaldehyde
Synthetic Retanning
Naphthalene
Synthetic Retanning
Chromium
Tanning
Chromium compounds
Tanning
Ammonia (anhydrous and 10% of aqueous)
Wastewater Treatment
Chlorine
Wastewater Treatment
Manganese
Wastewater Treatment
Manganese compounds
Wastewater Treatment
Nitrate compounds (only in water and water dissociable)
Wastewater Treatment

Source: EPA

Contact Aries Tek for removing chemicals from wastewater generated from leather processing and tanning operations…