80%
70%
80%
'iI ;. 50%
=
E GI
... 40%
. .
u
~
30%
0
U
20%
10%
0%
0.0
Chemical Pre-Treatment of Sewage - A Cost-Benefit Method
379
v-0.6155x fl-O.263
• v=O.25 3x +0.1613
R'=O.! 1707
./
VR' 0.9258
I'ly = 0.380 ~+0.1527
/
R'= . 8795 .. ~ . ..
AI
~/. foIo
. . ....
-.I ~ ~O
rf
A
7
y
= 0.2179x+ 0 ~876
/
R 2 =0.890
I
+Prallac
ABOPAC
~P
-I a FaCI3
DAI2(S04)3
.-.
0.5
1.0
1.5
2.0
2.5
3+
Metal dose [mmol Me /I]
....
I
1
3.0
3
Fig. 2. CODcr removal at Nt WWTP
It is important to examine the effect of coagulants on the removal of dissolved
organic matter. Fig. 3 shows the residual CODer in percentage of dissolved CODer
of raw sewage (dotted line represents the dissolved CODer concentration in raw
sewage). The graph illustrates that coagulants also affect the dissolved part of
organic matter content, even 40-55% of the dissolved CODer can be removed by
aluminum sulfate feeding.
200%
180%
180%
+ Preflac
.... BOPAC
r:::P
140%
0
120%
U
-; 100%
=
:s!
80%
'"
~
60%
a FeCI3
DAI2(S04)3
a
•
j~
.16. • . .
0
0"
0 · ..
In ...
--u
o I)
4
(
0
0
c
p
40%
20%
0%
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
Metal dose [mmol Me3+ll]
Fig. 3. Residual CODcr concentrations in percentage of dissolved organic content of raw
sewage at Nt WWTP