The only true leather-building substance in raw hide is corium collagen, everything else (hair, epidermis, fat, some proteinaceous matter etc.) has to be removed for which purpose substantial quantities of both general and specialty chemicals are needed; only some 20 % of them is actually retained by leather. Agglomerations of traditional tanning units with inadequate investment potential, lack of space and specific skills were conducive for setting up Common Effluent Treatment Plants (CETPs) servicing tannery clusters, the concept also adopted in relocations and/or establishing new leather clusters in developing countries. Due to only gradual increase in volumes of effluents and seasonal fluctuations associated with religious festivals, new CETPs are designed in modular way. On-site, physical-chemical (primary) treatment, including strict segregation of streams, catalytic oxidation of sulphide bearing spent floats, chrome management as well as equalization, settling, sludge removal and dewatering are by now already well-established technologies; the biological (secondary) treatment, typically using activated sludge method, often in raceways, in addition to high energy consumption, requires experienced personnel and close monitoring, in particular the removal of excess nitrogen (nitrification/denitrification). 

However, reutilisation and/or safe disposal of sludges remains a challenge to deal with. It appears that in very arid regions the best option to overcome the problem of Total Dissolve Solids (TDS, colloquially salinity) is to link tannery (C)ETPs with Municipal Wastewater Works (MWW).

Furthermore, it is important for the leather sector to take a proactive role in battling negative publicity and spreading of misleading information by fake green lobbies and pressure groups. Better coordination among various national, regional and global leather organizations, including R & D institutions would make a stronger impact.

Leather industry expert Richard Daniels In association with IULTCS, SLTC and the United Nations Industrial Development Organisation (Unido), has released an extensive guide to leather manufacturing.

The 10-part guide, which contains insight on leathermaking, was created to give aspiring leather technicians a self-training resource for the procedures used in making a wide variety of leathers. It includes 300 technical diagrams.

The study is optimised for mobile or tablet viewing and covers the raw material properties, manufacturing procedures and outcomes, and production of major leather types including:

Bovine hides
Hair sheep and goatskins
Wool-bearing sheepskins.

You can find the full guide in below. The full guide was presented during the XXXVI IULTCS Congress in Ethiopia in November 2021.The guide was updated and enhanced in 2024.

The course Introduction to Leather Testing is designed for training institutions, private companies and individuals that require understanding of both the theory and application of a wide array of standard test methods in utilize in the leather industry. The course is recommended to be used in a blend of classroom instruction using training content or self-learning along with allocation of time for hands on application in the laboratory. All courses provide opportunity for continuous professional development and lifelong learning.

The Course is divided into five modules:

M1: Fundamentals in Material Testing

M2: Basics in Leather Testing

M3: Physical Testing

M4: Fastness Testing

M5: Chemical Testing

Content was developed and prepared as a joint effort between UNIDO, FILK Freiberg Institute and Common Sense. Dr. S. Dietrich will guide you through the course. The course is offered free of charge and a certificate issued upon successful completion of the course.

The course will be available also in additional languages. The course was developed thanks to a generous support from the Government of Japan.

To register to the course, please use this link:  https://learning.unido.org/course/view.php?id=56

The course, “Introduction to Treatment of Tannery Effluent” is designed for training institutions, private companies, and individuals that require an understanding of effluent treatment methods in the leather industry. The course is recommended to be used in a blended approach via classroom instruction using training content or self-learning along with an allocation of time for hands-on application in the laboratory.   There are 5 modules in this course as below:

Module 1: Load, norms, in-house treatment. This module will explain the aim of effluent treatment; pollution load and the main wastewater quality parameters; typical discharge norms.  It will also offer a general overview of the treatment of tannery effluents, segregation of streams, treatment of spent liming floats, and treatment of chrome-bearing floats
Module 2: Treatment within tannery compound. This refers to the pre-treatment for discharge into the common effluent treatment plant (CETP) collection network, and physical-mechanical (primary) treatment for discharge into municipal sewage.
Module 3: Sludge dewatering.  This module explores sludge thickeners, sludge pumps, filter press, centrifuge, belt filter press, flow-chart of physical-chemical treatment, and sludge drying beds.
Module 4: Biological (secondary) treatment.  This module looks into activated sludge, aeration devices, oxidation ditch, and the flow-chart of the biological treatment
Module 5: Occupational safety and health (OSH) in CETP, and its costing and management

Link to the course: https://learning.unido.org/course/view.php?id=6