The document discusses the tannery industry in India, highlighting the treatment of industrial waste which includes strong odors, high biochemical oxygen demand, and high pH levels. It outlines the three stages of the manufacturing process: preparation of hides, tanning (which includes both vegetable and chrome tanning), and finishing, noting the characteristics and uses of each tanning method. Additionally, it poses both objective and theory questions related to the processes and waste treatment alternatives in the tannery industry.

1. L- 28L- 28
Tannery Industry
Industrial Waste Treatment

2. Introduction
• Tannery industry is one of the oldest in
India.
• Usually tannery waste consists of
- Strong odour
- High BOD,- High BOD,
- High pH
- High dissolved salts
• Treatment of waste is essential before
treatment.

3. Manufacturing Process
•It consists of basic three stages
1. Preparation of hides for tanning
2. Tanning proper
3. Finishing3. Finishing

4. i] Preparation of hides
1) In first stage hides are washed to
remove dirt and preservative salts
used earlier and then soaked into
the fresh water containing NaCl and
preservative chemical.preservative chemical.
2) The hides are washed in running
water. Washed hides are pasted with
lime and sodium sulphide

5. 3) Limed hides are then mechanically
cleaned of hairs and fleshing in
wooden vats with running fresh
waters.
4) Bating prepares the hides for tanning
by reducing pH, reducing swelling and
removing the protein degradation
products of it.

6. 5) The deliming and bating is carried
out in verrrrtically rotating drums in
warm solution of ammonium salts
and enzymes

7. ii] Tanning proper
•Tanning makes hides
nonputrescible and soft.
•There are two types of tanning
1. Vegetable tanning1. Vegetable tanning
2. Chrome tanning

8. 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• 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.

9. 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 thetanning (less than a day for this part of the
process) and produces a stretchable
leather which is excellent for use in
handbags and garments.

10. iii] finishing
•Finishing consists of stuffing and fat
liquoring followed by dyeing

16. Treatment alternative -

18. Chrome
recoveryrecovery

19. Objective Questions
1. Two types of tanning processes are
________ and ______ tanning
2. _________ tanning requires very less time.
3. Amount of Chromium present in spent3. Amount of Chromium present in spent
chrome tan liquor is _______ mg/lit

20. Theory Questions
Q1. Discuss detailed process involved in the
tannery with the help of process flow
sheet.
Q2. Give general characteristics ofQ2. Give general characteristics of
Combined waste from tannery industry.
Q3. Discuss treatment alternatives for
leather tanning industry.