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All
right reserved. Any Unauthorized Copying or Using Prohibited.
NEW
PROCESS FOR
IMPROVEMENT OF
CONTAMINATED
SEDIMENTS
BY
SUCCESSION
OF MICRO-BIOTA
2nd
INTERNATIONAL
CONFERENCE
on
COTAMINATED
SEDIMENTS.
Rotterdam
Netherlands.
September
7-11
1997
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RESURUTS
AND DISCUSSION.
The
results of the tests are described below.
.Reduction
in the volume of sediments. .Changes
in the composition of sludge.
.Results
of nitrogen, phosphorus and COD release tests.
.Nitrogen.
.Making
the sediments odorless. .Change
in the bacterial phase. .Iron.
Reduction
in the volume of sediments
Top
Page
The
concentration of sludge, 63,100 mg/l at the time of commencing the
test, dropped to 50,600 mg/l after the lapse of 25 days. The
results of this test are shown in Table 1.
The
table shows the percentage changes % and DSkg/m3 taking the value
at the time of commencing the test as 100.
Table
1 Changes of sludge concentration in test tank
|
Day
|
Starting
day
|
25days
|
_
|
|
Item
(Unit)
|
DSkg/m3
|
%
|
DSkg/m3
|
%
|
%/day
|
|
MLSS
|
63,1
|
100
|
50,6
|
80.2
|
-0.79
|
|
MLVSS
|
15,9
|
100
|
16,2
|
101.9
|
_
|
|
MLSS-VSS
|
47,2
|
100
|
34,4
|
72.9
|
_
|
Changes
in the composition of sludge.
Top
Page
The
tendencies of changes in the composition of sediments and improved
sludge in this test are described below. Changes in the
composition of sediments are shown in Table 2.
Table
2 Change of sludge composition in test tank
|
|
Starting
day
|
25days
|
|
|
|
Item
|
(Unit)
gr/m3
|
gr/m3
|
%
|
%
|
|
C
|
4,382
|
3,850
|
87.9
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-12.1
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N
|
323
|
290
|
89.8
|
-10.2
|
|
P
|
154
|
154
|
100.1
|
+0.1
|
|
S
|
791
|
45
|
5.7
|
-94.3
|
|
Si
|
9,591
|
6,927
|
72.2
|
-27.8
|
|
Fe
|
2,618
|
2,646
|
101.1
|
+1.1
|
(1)
Sulphur (S) in the sediments rapidly decreased with the succession
treatment.
(2) Silicon (Si) in the sediments greatly decreased
with the succession treatment. A similar tendency was also
observed in reducing the volume of sludge.
(3) Carbon (C) in
the sediments decreased a little with the succession treatment.
Carbon is a substance that may be increased by bio-treatment
(carbon dioxide assimilation). It was an interesting behavior in
comparison with the behavior of other substances such as
silicon.
(4) Nitrogen (N) in the sediments decreased a little
with the succession treatment.
(5) Phosphorous (P) and iron
(Fe) underwent no change with the succession treatment.
Fig
3.1 shows the quantitative changes(mg/l) of the composition in
sludge and Fig 3.2 shows the changes(%) of the sludge composition
in the test tank.
|
Test
period[day]
|
Test
period[day]
|
|
Figure
3.1 Change in the component of the improved bottom
sediments[mg/l]
|
Figure
3.2 Change in composition of the improved bottom sediments[%l]
|
Results
of nitrogen. phosphorus and COD release tests
Top
Page
Tests
were conducted on the release of nitrogen, phosphorus and COD from
the sediment in Marsh Furukawa and the improved sediment. As a
result, differences in the release characteristics (release rate
and volume) between the sediment in the marsh and the improved
sediment were clarified. Particularly, as for nitrogen, a tendency
contrary to the release was observed, and a conspicuous difference
was seen in the release characteristics of the sediment in the
marsh and the improved sediment. The results of these tests are
shown in Table 3.
Table
3 Release test results from the bottom sediments and improved
bottom sediments
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|
Bottom
sediments
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Improved
sediments
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Improvement
effect
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Item
(Unit)
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mg/m2/day
|
mg/m2/day
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%
|
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COD
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45.1
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-0.8
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101.8
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Nitrogen
|
89.2
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-5.4
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106.1
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Phosphorus
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39.3
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1.2
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96.8
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Nitrogen
Top
Page
The
results of the release test are shown in Fig. 3.3.
Test
period[day] ____________________
Test period[day]
Figure 3.3 Release test results of nitrogen
from bottom sediments and improved bottom sediments.
Making
the sediments odorless
Top
Page
The
results of the gas generation test are shown in Table 4.
Table
4. Gas generation rate and improved effect.
|
|
Sediments
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Improved
sediments
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Improved
effect
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Item
(Unit)
|
ul/DS
kg
|
ul/DS
kg
|
%
|
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Sulfide
|
87.3
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ND
|
100
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Methane
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982.0
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9.2
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99.1
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Ammonia
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34..0
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18.9
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44.4
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Change
in the bacterial phase
Top
Page
To
verify the safety of the sediment in the marsh and the improved
sediment, ordinary bacterial count and coliform group number were
measured. The results of this test are shown in Table 5.
Table
5 .Change in the number of the bacteria.
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Bacterial
phase
|
Sediments
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Improved
sediments
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Removal
rate
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Bacteria
[number / cc]
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75.100
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890
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99%
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Coliform
group [group number / cc]
|
512,000
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15
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100%
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Iron
Top
Page
Iron
is an oxidation-reduction element contained in the sediments.Under
oxidation-free condition, it becomes reduced iron and can be used
as an index of the environment in which the sediments are placed.
Simultaneously with the succession treatment of microorganisms,
the iron contained in the sediments is oxidized. The change in the
composition of iron in the sediments is an index showing
succession treatment and also the volume of oxygen contained in
the sediments and the capacity to retain oxygen. The results of
this test are shown in Table 6.
Table
6. Change in the iron contained in sludge.
|
test
period
|
starting
day
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25days
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Item/
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(Unit)
g/KgDS
|
%
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mg/KgDS
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%
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Fe
2+
|
35300
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85
|
7400
|
14
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Fe
3+
|
6200
|
15
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44900
|
86
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In
this test, the harmful sediment became a brown sludge and its ORP
was +300 mv and pH was 6.5.
(1)
The putrid contaminated organic sediment was odorless.
(2) The
sediment decreased by 0.79% DS/day.
(3) Changes in the
composition of the sediment were different, depending on
substances. Sulfur decreased greatly. The decrease in silicon was
large, and agreed with that of the sediment. The decrease of
nitrogen and carbon was small and showed the same tendency. A
decrease of phosphorus and iron was not recognized. It is
therefore possible to estimate the increase and decrease of
sediments from the variations in the concentration of which
substance.
(4) The regeneration of substances (nitrogen and
phosphorus) causing eutrophication from sediments was greatly
reduce. Particularly, nitrogen showed a self-purifying tendency,
indicating that the function of activated sludge was transplanted.
The same tendency was also observed in COD.
(5) The coliform
bacilli contained in the sediments decreased.
(6) 85% of iron
contained in the sediments changed into oxidized iron, and harmful
sediments were improved into sediments possessing a large amount
of oxygen. The results of these tests showed the same tendency as
those of basic tests conducted in Marsh Furukawa (brackish lake,
1988-89) and those of continuous tests conducted in Lake Biwa
(freshwater lake, 1991-92), thus demonstrating the reproducibility
of succession technology. From the tests and actual examples, this
process proved to be effective in improving the harmful
contaminated organic sediments found in the freshwater, brackish
water and sea areas.
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