1. TREATMENT OF
TANNERY WASTEWATER
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Presented by
SUSAN ANN JAYAN
II M.SC., Biotechnology
School of Biotechnology & Genetic Engineering
Bharathiar University

2. An aerial view..
medium-sized tannery wastewater treatment plant
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3. Tanning industry
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What is tanning?
 Tanning is the process that converts a part of a once
living animal (i.e., hides and skins) into a non-rotting,
soft and durable textile called leather
 Two types of tanning, broadly :
 Vegetable tanning
 Chrome tanning
Procedures involved..
 After removal of hairs and flesh, the involved processes
are curing, receiving and storing, soaking, unhairing,
bating, pickling, tanning, wringing, sorting, splitting and
shaving.

4. Chemicals used in a tannery
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LEATHER PROCESS CHEMICALS USED
Curing & Preservation Sodium chloride, pentachlorophenol
Soaking, Liming & Unhairing Sodium sulphide, caustic soda,
surfactants, milk of lime
Deliming Ammonium chloride, ammonium
sulphate
Degreasing Alkyl phenyl ethoxylate
Pre-tanning Basic chrome sulphate
Tanning/retanning Mineral tannages/retannages
Fat liquoring Synthetic at liquors, surfactants from
petrochemicals
Finishing Cadmium and lead chrome pigment,
nitrocellulose and liquor emulsion
water-proofing agent

5. Tannery wastewater is characterized by..
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6. Fate of 1000 kg of wet-salted hides..
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7. TREATMENT REGIME
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Combination of physical, chemical and
biological systems
 1. Separation of effluents within the tannery
 Wastewater collection within departments to maintain
separate beamhouse effluents
 By means of gutters and sluice gates
 2. Hair recovery from liming baths
 To reduce pollution load considerably
 Special passages of very fine screens
 Recycling outside the drum
 Mechanical separation effectively reduces concentration of
suspended solids 30-40% & COD 20-30%

8. Rotating drums - for separation of hair
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9.  3. Chrome recovery from Tanning baths
 Drastic reduction of heavy metal load
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 Sludge containing high amounts of chromium is usually disposed
off in landfills
 Re-use of expensive chromium –
 Add alkaline lime to acidic tanning bath and adjust pH to slightly
above neutrality – bivalent chromium will completely settle
 4. Screening operations
 Fundamental
 Coarse grid bars
 Filtering at 10mm
 Prevents clogging by coarse pieces of leather, wood, etc.
 Rotating brush
 Filtering at 2-3mm diameter

10. Chrome recovery plant, with a filter press
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11. Rotating brush screening
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 5. Equalization & Sulfide oxidation
 Necessary due to unequal discharge of effluents
 Sulfide oxidation carried out and the contents are kept mixed
 Manganese sulfate may be added to speed up, acting as
catalyst

13. Equalization & Sulfide oxidation tank
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 6. Flocculation
 Chemical flocculation for suspended solids & unyielding
colloidal organic matter
 Flocculants –
 metal salts - ammonium sulfate, most effective
 organic coagulants (polyelectrolytes) – increase size of sludge
flakes

15. Flocculation in tanks fitted with agitators
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 7. Sedimentation
 Gravitational settling of suspended solids, then disposal of
clarified supernatant into sewers
 Sedimented sludge is collected by pumps for dehydration
 8. Sludge treatment
 Natural drying beds
 Sludge is distributed in layers a few cm high and loses water by
filtration on a bed of sand and gravel and natural evaporation
 Frequently used in geographical zones with dry hot climate
 Mechanized systems, e.g., filter presses, continuous belt
presses, centrifugal decanters
 Used when the quantity of sludge produced each day is high,
because the area needed would be excessive

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 9. Biological treatments
 To reduce the soluble and suspended or colloidal organic
matter in effluents into carbon dioxide and minerals
 Bubble aeration systems
 Lagoon systems
 Sequencing batch biofilm reactor (SBBR)
 Combined with chemical oxidation by ozone. The treatment was
carried out at laboratory scale on a real primary effluent coming
from a centralized plant treating the wastewater of a large tannery
district in Northern Italy [2]
 Microbial consortia
 Fungal and bacterial biosorptive degradation
 Bacillus, Rhizopus, Aspergillus, Streptovertcillum,
Saccharomyces

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 10. Other innovative methods

 Use of activated clays in the removal of dyes and surfactants[3]
 The capacity of sepiolite and acid-activated bentonite to adsorb
anionic dyes normally used in the tannery was compared with
conventional adsorbents
 Natural bentonite activated with 0.5 M H2SO4 was the most effective
adsorbent for ethoxylated nonylphenol.
 Use of electrochemical processes as alternative to biological
nitrification/denitrification processes, for removal of a variety of
pollutants[4]
 And their combinations are still being studied
 Quicker and reduction in global plant volume (considering both
biological and electrochemical sections) and sludge generated for
disposal

19. References
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1. http://www.fgmengineering.it >wastewater treatment>tannery
2. Thakur S. T., Environmental Biotechnology – Basic Concepts
and Applications. I.K. International Pvt. Ltd; 398-408
3. C. Di Iaconi , A. Lopez , R. Ramadori , and R.
Passino. Tannery Wastewater Treatment by Sequencing Batch
Biofilm Reactor. Environ. Sci. Technol., 2003, 37 (14), pp
3199–3205
4. A.G Espantaleón et al.,(2003). Use of activated clays in the
removal of dyes and surfactants from tannery waste waters.
Applied Clay Science, 2003,24 (1-2), pp 105-110
5. Lidia Szpyrkowicz, Santosh N. Kaul, Rao N. Neti. Tannery
wastewater treatment by electro-oxidation coupled with a
biological process. Journal of Applied Electrochemistry (2005)
35: 381-390

20. Luxury with Responsibility..
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