30
A. Geethakarthi
Table 2 Characteristics of tannery effluent
Parameter Soaking
Beam house
operation
Pickling and
chrome
tanning
Wet
finish—rechroming,
dyeing and fat
liquor
Composite
(include
washing)
Volume of
the
effluent in
litres/ton
of hides
6000–9000
6000–10,000 1500–3000
3000–5000
30,000–40,000
pH
7.5–8.0
8.0–12.0
2.2–4.0
3.5–4.5
7.0–9.0
BOD 5 ,
mg/L
1100–2500
2000–8000
400–800
1000–2000
1200–3000
COD,
mg/L
3000–6000
3000–15,000 1000–3000
2500–7000
2500–8000
Sulphide,
mg/L
–
50–200
–
–
30–150
Total
solids,
mg/L
35,000–55,000 6000–20,000 30,000–60,000 4000–10,000
15,000–25,000
Dissolved
solids,
mg/L
32,000–48,000 5000–15,000 29,000–58,000 3400–9000
13,000–20,000
Suspended
solids,
mg/L
3000–7000
3000–15,000 1000–2000
600–1000
2000–5000
Chlorides,
mg/L
15,000–30,000 3000–6000
15,000–25,000 500–1000
6000–9500
Total
chromium
mg/L
–
–
1500–3000
30–60
80–200
Source Central Leather Research Institute, Chennai, India
Note Volume of wastewater applicable for hides (cow and buffalo) and goat skins and not for wool
sheep skins
Table 3 Advantages and limitations of sludge drying
Advantages
Limitations
Volume of sludge is significantly reduced
High energy requirement and intensive
Further disposal/reuse of sludge is needed
Investment cost is very high
Pathogen-free residue can be found in the end
sludge with minimal odour
Operational cost is high
Product requires very less area, since the end
sludge can be pelletized
Testing, operating and controlling the process
are labour-intensive and expensive
A. Geethakarthi
Table 2 Characteristics of tannery effluent
Parameter Soaking
Beam house
operation
Pickling and
chrome
tanning
Wet
finish—rechroming,
dyeing and fat
liquor
Composite
(include
washing)
Volume of
the
effluent in
litres/ton
of hides
6000–9000
6000–10,000 1500–3000
3000–5000
30,000–40,000
pH
7.5–8.0
8.0–12.0
2.2–4.0
3.5–4.5
7.0–9.0
BOD 5 ,
mg/L
1100–2500
2000–8000
400–800
1000–2000
1200–3000
COD,
mg/L
3000–6000
3000–15,000 1000–3000
2500–7000
2500–8000
Sulphide,
mg/L
–
50–200
–
–
30–150
Total
solids,
mg/L
35,000–55,000 6000–20,000 30,000–60,000 4000–10,000
15,000–25,000
Dissolved
solids,
mg/L
32,000–48,000 5000–15,000 29,000–58,000 3400–9000
13,000–20,000
Suspended
solids,
mg/L
3000–7000
3000–15,000 1000–2000
600–1000
2000–5000
Chlorides,
mg/L
15,000–30,000 3000–6000
15,000–25,000 500–1000
6000–9500
Total
chromium
mg/L
–
–
1500–3000
30–60
80–200
Source Central Leather Research Institute, Chennai, India
Note Volume of wastewater applicable for hides (cow and buffalo) and goat skins and not for wool
sheep skins
Table 3 Advantages and limitations of sludge drying
Advantages
Limitations
Volume of sludge is significantly reduced
High energy requirement and intensive
Further disposal/reuse of sludge is needed
Investment cost is very high
Pathogen-free residue can be found in the end
sludge with minimal odour
Operational cost is high
Product requires very less area, since the end
sludge can be pelletized
Testing, operating and controlling the process
are labour-intensive and expensive