600
J. Bebin, P. Boulenger and J.C. Bourdelot
Table 5. Treatment by aluminium sulphate
Colour, COD, BOD efficiency
raw effluent characteristics :
PH
colour
mg Pt/1
COD
mg/1
BOD
mg/1
treated effluent characteristics :
PH
colour
mg Pt/1
COD
mg/1
BOD
mg/1
obtained efficiencies :
colour
%
COD
%
BOD
%
Sodation
10.8
3350
2400
430
5.4
290
600
260
91.5
75
39.5
Chlorinosodation
2.4
1100
1090
-
5.4
95
450
-
91.4
59
-
Efficiency in COD and BOD removal
The BOD is not very much affected by chemical treatment. The COD reduction tends
to show that a part of the colour removal is not only due to the removal of all the
molecules responsible for the COD, but also some transformation of certain of these
molecules.
Reagent and energy consumption
Table 6. Aluminium sulphate treatment. Power and reagent consumption
Sludge production
Mineral matter content
Reagent consumption
. technical aluminium sulphate
. lime
. organic polymeres
. sulphuric acid
Power consumption
. electrical
. thermal
kg/t of pulp
% D.S.
kg/t of pulp
kWh/tofpulp
thermies/t of pulp
40
20 to 30
3.8
2
0.078
30
2
75.5
See Fig. 4: aluminium sulphate process — basic diagram.