382
I. Licsko et al.
the plant was complemented with nitrifying and denitrifying submerged biofilm
reactors downstream from the activated sludge stage. Before upgrading, the
phosphorus concentration was decreased by biological phosphorus removal, now
it is obtained by chemical addition into the activated sludge basin (simultaneous
precipitation).
Before upgrading of the WWTP, no significant nitrification was performed at
the activated sludge section. Now at relatively high temperature (>20 0c) 35-40%
of the ammonium is transformed into nitrate, although the age of the aerobic
sludge is less than 3 days. During winter, the ~-N conversion is usually very
low.
350
90
a"
~
300
COl
~
'"
-=
250
a"
"" COl
~~ 200
.5 Ob
' " e
a,,150
:t:
COl
e
u
100
' = COl
~
50
0
A
A
~
•
I
•
.i.l
• ~ ~ ..........
~
f).-.c
ra~ rz:r lil
V n
_ tI- - - -
-n::r __ !!1 I~IIII- 0
--Ii; -Ii - - - tf - ....... . -- .. ......
•
• --' .:: . •
I...._
- - - .... -
I-Q.. I - - _ 1 _ -
-
•
COD with Fe3+
0 COD with AI3+
•
BOD5 with Fe3+
0 BODS with A13+
I-- - - . Filtered COD
-
-Filtered BOD5
- . - COD removal (Fe3+)
t:. COD removal (Al3+)
80
70
60
50
40
30
20
10
•
BODS removal (Fe3+)
Q BODS removal (AI3+)
o
o
5
10
15
20
25
30
35
Metal dose [Me 3 + mg/I]
40
45
50
Fig. 5. Removal rates and residual concentrations of organic matter at B I WWTP
Evaluation of the existing data showed relatively high organic content
removal in the primary settling tank (35-45%); however, phosphorus removal was
not so effective. The lab experiments have demonstrated that chemical
pretreatment could increase the organic removal to 70-80% as CODer and to 6065% as BODs (Fig. 5-7) The further results showed that 60-70% of the raw
sewage organic matter is connected to suspended solids. The lab experiments
demonstrated the special reactions between different species of aluminum and
iron(III) hydroxides and some types of organic compounds of sewage. The
residual CODer concentration was below the value of the filtered sample meaning
that part of the dissolved CODer was also removed by coagulation (see Figs. 5, 6).
It is very important to know the minimum residual organic content after the
chemical pretreatment. During the experiments different sewage samples were
investigated having an average (400-600 mgr 1 CODer), extremely low (270 mgr l
CODer) and high (4000 mgr l CODer) organic matter concentrations. In the latter
I. Licsko et al.
the plant was complemented with nitrifying and denitrifying submerged biofilm
reactors downstream from the activated sludge stage. Before upgrading, the
phosphorus concentration was decreased by biological phosphorus removal, now
it is obtained by chemical addition into the activated sludge basin (simultaneous
precipitation).
Before upgrading of the WWTP, no significant nitrification was performed at
the activated sludge section. Now at relatively high temperature (>20 0c) 35-40%
of the ammonium is transformed into nitrate, although the age of the aerobic
sludge is less than 3 days. During winter, the ~-N conversion is usually very
low.
350
90
a"
~
300
COl
~
'"
-=
250
a"
"" COl
~~ 200
.5 Ob
' " e
a,,150
:t:
COl
e
u
100
' = COl
~
50
0
A
A
~
•
I
•
.i.l
• ~ ~ ..........
~
f).-.c
ra~ rz:r lil
V n
_ tI- - - -
-n::r __ !!1 I~IIII- 0
--Ii; -Ii - - - tf - ....... . -- .. ......
•
• --' .:: . •
I...._
- - - .... -
I-Q.. I - - _ 1 _ -
-
•
COD with Fe3+
0 COD with AI3+
•
BOD5 with Fe3+
0 BODS with A13+
I-- - - . Filtered COD
-
-Filtered BOD5
- . - COD removal (Fe3+)
t:. COD removal (Al3+)
80
70
60
50
40
30
20
10
•
BODS removal (Fe3+)
Q BODS removal (AI3+)
o
o
5
10
15
20
25
30
35
Metal dose [Me 3 + mg/I]
40
45
50
Fig. 5. Removal rates and residual concentrations of organic matter at B I WWTP
Evaluation of the existing data showed relatively high organic content
removal in the primary settling tank (35-45%); however, phosphorus removal was
not so effective. The lab experiments have demonstrated that chemical
pretreatment could increase the organic removal to 70-80% as CODer and to 6065% as BODs (Fig. 5-7) The further results showed that 60-70% of the raw
sewage organic matter is connected to suspended solids. The lab experiments
demonstrated the special reactions between different species of aluminum and
iron(III) hydroxides and some types of organic compounds of sewage. The
residual CODer concentration was below the value of the filtered sample meaning
that part of the dissolved CODer was also removed by coagulation (see Figs. 5, 6).
It is very important to know the minimum residual organic content after the
chemical pretreatment. During the experiments different sewage samples were
investigated having an average (400-600 mgr 1 CODer), extremely low (270 mgr l
CODer) and high (4000 mgr l CODer) organic matter concentrations. In the latter