Colour Removal from Bleached Kraft Pulp Waste Waters
601
Effluent to
PRECIPITATION
SETTLING
be trea-ted
A
injection|
+ i < n v i
f l n . 4 + +i+ +#
o t
THICKENING TANK
+
t
ALUMINIUM
I
J
!
+
SULPHATE
.
1
1
T
2SO4+H2O
CoSO^
f v e n t u o l
|
dump
TALUMINIUM
\^~)
[RECOVERY
I
«^JX^INCINERATION
Fig. 4.
Treatment of Bleaching Effluents with Aluminium Sulphate - Flow Sheet
COMPARATIVE COST OF TREATMENT
BY ALUMINIUM SULPHATE AND LIME
Aluminium Sulphate
Lime
Characteristics Cost per ton of Characteristics Cost per ton of
pulp in Dollars
pulp in Dollars
Investments -
. Equipment (clarifiers,
sludge treatment,
regulation units)
. Civil Engineering
Total
Depreciation
Power -
. electrical (Dollars/kWh)
. thermal (Dollars/thermie)
Chemicals -
aluminium sulphate
. lime
. coagulation aid products
sulphuric acid
Labour
Maintenance
355,000
65,000
420,000
on 10 years
0.0145
0.0027
4% of annual
capital
0.57
0.0273
0.21
0.20
0.031
0.187
0.642
0.16
0.153
710,000
55,000
765,000
on 10 years
4% of annual
capital
1.04
0.30
0.642
0.16
0.28
TOTAL
2.175
2.42
WITHOUT DEPRECIATION
1.61
1.38