The document discusses the tannery industry process and waste water treatment. It describes the various stages of tanning including preparatory, tanning, and surface coating stages. It outlines the sources and characteristics of waste water generated at different stages. It then summarizes various treatment schemes that can be used including solids removal, biodegradable organics removal through activated sludge or trickling filter processes, and specialized treatment for other pollutants like acids, alkalis, oils, grease, and chromium. It notes that while in-process measures can reduce water usage and pollution, end-of-pipe treatment is still needed to further treat any waste water from tanneries.

2. Submitted To
Dr.(Mrs) Smita B Patil
Submitted By
Shubham Patil - C/70
Saurabh Kokane - C/58
Harsh Shah - C/60
Khushboo Patil - C/47

3. Tanning
Tanning is the process that converts the protein of the raw hide or
skin into a stable material which will not putrefy and is suitable for a wide
variety of end applications. Tanned material dries out to a flexible form.
That does not become putrid when wetted back.

4. Overview Of Tannery Industry

5. CONTENTS
Process of
Tannery
Industry
Waste
Generation
Points
Characteristics
of Waste Water
Treatment
Schemes for
Waste Water
Innovative
Technology

7. Preparatory Stages
Tanning and Crusting
Surface Coating

8. Preparatory Stages
The preparatory stages are when hide/skin is prepared for tanning. Many options for pretreatment
of skin exist. Not all of the options may be performed. Preparatory stages may include :-
Preservation - the hide/skin is treated with a method which renders it temporarily unputrescible.
Soaking - water for purpose of washing or rehydration is reintroduced.
Liming - unwanted proteins and “opening up” is achieved.
Unhairing - the majority of hair is removed.
Fleshing - subcutaneous material is removed.
Splitting - the hide/skin is cut into two or more horizontal layer.
Reliming - the hide/skin is further treated to achieve more “opening up” or more protein removal.
Deliming - liming & unhairing chemicals are removed this step.
Bating - proteolytic proteins are introduced to the skin to remove further proteins and to assist
with softening of the pelt.
Degreasing - natural fats/oils are stripped or as much as is possible from the hide skin.
Frizing - physical removal of fat layer inside the skin.

9. Preparatory Stages
Bleaching - chemical modification of dark pigments to
yield a lighter coloured pelt.
Pickling - lowering of pH value to the acidic region. Must
be done in presence of salt.
Depickling - raising of the pH out of the acidic region.
Soaking of HidesTrimming Of Hides

10. Tanning
Tanning is the process that converts the protein of the raw hide or
skin into a stable material which will not putrefy and is suitable for a wide
variety of end applications. Tanned material dries out to a flexible form.
That does not become putrid when wetted back.
There are two types of tanning :-
• Vegetable tanning
• Chrome tanning

11. Vegetable tanning
• Tannins bind to the collagen proteins in the hide and coat them
causing them to become less water-soluble, and more resistant to
bacterial attack.
• The process also causes the hide to become more flexible.
• Hides are stretched on frames and immersed for several weeks in vats
of increasing concentrations of tannin.
• Vegetable tanned hide is flexible and is used for luggage and furniture.

12. Chrome Tanning
• Chromium salts such as chromium sulphate is used.
• Chrome tanning is faster than vegetable tanning (less than a day for
this part of the tanning (less than a day for this part of the process)
and produces a stretchable leather which is excellent for use in
handbags and garments.

13. Crusting
Crusting is when the Hide/Skin is thinned, re-tanned and
lubricating often a coloring operation is included in the crusting sub
process. The chemicals added during crusting have to be fixed in place.
The culmination of the crusting sub process is the drying and softening
operation.

14. Surface
Coating
Finishing : Finishing consists of
stuffing and fat liquoring followed
by dyeing. It includes :-
•Oiling
•Brushing
•Padding
•Spraying
•Roller Coating
•Curtain Coating
•Polishing
•Plating
•Embossing
•Ironing
•Combing
•Glazing

15. Waste Water Generation Points

16. Source
Soaking Effluent : Soluble Protein like Albumin, major source of Proteolytic and other
Bacteria,Dirt.
Liming Effluent : Suspended and Dissolved Lime and Sodium Sulphide.
Unhairing and Fleshing Effluent : Hair, Sulphides.
Deliming Effluent : Deliming Liquor.
Spent Bate Liquor : Organic matter, Ammoniacal Nitrogen.
Spent Pickle Liquor : Acidic Salts.
Vegetable Tanning Effluent : Spent Vegetable Tan Liquor.
Chome Tanning Effluent : Spent Chrome Tan Liquor.
Dyeing and Fat-Liquoring Effluent : Dye, Oily Emulsions.
Composite Effluent : Highly Alkaline coloured, Foul smelling.

17. Characteristics Of Wastewater

19. Treatment of Waste Water

22. Solids Removal
Most solids can be removed using simple
sedimentation techniques with the solids
recovered as slurry or sludge. Very fine solids
and solids with densities close to the density of
water pose special problems. In such case
filtration may be required. Although flocculation
may be used, using alum salts or the addition of
polyelectrolytes.

23. Removal of Biodegradable Organics
Biodegradable organics material of plant or animal origin is usually
possible to treat using extended conventional wastewater treatment
processes such as Activated Sludge Process or Trickling Filters.

24. Activated Sludge Process
Activated sludge Process is a biochemical
process for treating sewage and Industrial
waste that uses air (Oxygen) and micro-
organisms to oxidize organic pollutants,
producing a waste sludge (or flock) containing
the oxidized material

25. Trickling Filter Process

26. A trickling filter process consists of bed of rocks, gravel, slag, peat moss or plastic media over which
wastewater flows downwards and a contacts a layer of microbial slimes covering the bed media. Aerobic
conditions are maintained by forced air flowing through the bed or by natural convection air. The process
involves adsorption of organic compounds of wastewater by the microbial slime layer, diffusion of air into
the slime to provide the oxygen required for the biochemical oxidation of organic compounds. The end
product includes carbon dioxide gas, water and other products of oxidation. As the slime layer thickness
increases, it becomes difficult to the air to penetrate the layer and an inner anaerobic layer is formed.
Trickling Filter Process

27. Synthetic organics material including solvents, paint, pharmaceuticals, pesticides,
cooking products and so forth can be very difficult to treat. Treatment methods are often
specific to the material being treated. Methods include advanced oxidation processing,
distillation, adsorbtion, vitrification, incineration, chemical immobilisation or landfill
disposal.
TREATMENT OF OTHER ORGANICS

28. Acids & alkalis can usually be neutralised under controlled conditions.neutralization frequently
produces a precipitatethat will require treatmentas a solid residue that may also betoxic. In some
cases,gases may be evolved requiring treatmentfor the gas stream. Some other forms of treatment
are usually required following neutralisation.
TREATMENT OF ACIDS & ALKALIS
OIL AND GREASE REMOVAL
Oil and greasecan berecovered from openwater surfaces by skimming devices.

29. Chromium,present in tannery effluent is removed by using chromium
salts(chromiumchloride as adsorbate)and cement kiln dust (a waste from
white cement industry)as adsorbent.
TREATMENT OF CHROMIUM

30. Leather plant in Liptovský Mikuláš in Central Slovakia

31. A significant number of operations within a tannery are wet
operations consuming large amounts of water, chemicals and energy
and leading to large amounts of polluted water. Through “process
integrated” measures a significant reduction of water consumption
and pollution load can be achieved, however tanneries keep
producing wastewater requiring special treatment. In cases where
the potential for “process integrated” measures has worn out, further
pollution reduction has to be found in the improvement of end-of-
pipe measures.