ABSTRACT: The Fukushima nuclear accident of March 11, 2011, soil and water had been contaminated by radioactive cesium. Moreover, radioactive cesium was found in the ocean sludge in Tokyo Bay flowing from rivers. Cesium which is adsorbed to the sludge cannot be easily removed. One of the authors developed decomposition and purification system, a circulation-type system by micro bubbles, that is, by creating aerobic state, aerobic bacteria are activated resulting to decomposition and purification of ocean sludge. Based on the hypothesis that radioactive cesium is adsorbed on the surface of the sludge deposition. It is considered cesium can be eluted after decomposing the deposited sludge. Once the cesium is eluted in the water, it can fix to a mineral such as zeolite. Now we need the properties of sludge in removal process by decomposition system with circulation type. In this study, our objects is to check the characteristics of the sludge particle in removal process of radioactive cesium from ocean sludge by decomposition system with circulation type using micro bubbles and activating microorganisms. As the results of this experiments, we had very good purification ratio on total nitrogen and had made 40 times of smaller size on diameter of the particle of sludge

Kyoichi Okamoto

Takeshi Toyama

Tomoe Komoriya

CiteSeerX

 
51 
CHARACTERISTICS OF THE SLUDGE PARTICLES IN REMOVAL 
PROCESS OF RADIOACTIVE CESIUM FROM OCEAN SLUDGE BY 
DECOMPOSITION SYSTEM WITH CIRCULATION TYPE USING 
MICRO BUBBLES AND ACTIVATING MICROORGANISMS 
*Kyoichi OKAMOTO
1
, Takeshi TOYAMA
1
 and Tomoe KOMORIYA
2
1
CST, Nihon University, JAPAN; 
2
 CIT, Nihon University, JAPAN 
* Corresponding Author, Received: 29 June 2016,   Revised: 19 August 2016, Accepted: 30 Nov. 2016
ABSTRACT: The Fukushima nuclear accident of March 11, 2011, soil and water had been contaminated by 
radioactive cesium. Moreover, radioactive cesium was found in the ocean sludge in Tokyo Bay flowing from 
rivers. Cesium which is adsorbed to the sludge cannot be easily removed. One of the authors developed 
decomposition and purification system, a circulation-type system by micro bubbles, that is, by creating 
aerobic state, aerobic bacteria are activated resulting to decomposition and purification of ocean sludge. 
Based on the hypothesis that radioactive cesium is adsorbed on the surface of the sludge deposition. It is 
considered cesium can be eluted after decomposing the deposited sludge.  Once the cesium is eluted in the 
water, it can fix to a mineral such as zeolite. Now we need the properties of sludge in removal process by 
decomposition system with circulation type. In this study, our objects is to check the characteristics of the 
sludge particle in removal process of radioactive cesium from ocean sludge by decomposition system with 
circulation type using micro bubbles and activating microorganisms. As the results of this experiments, we 
had very good purification ratio on total nitrogen and had made 40 times of smaller size on diameter of the 
particle of sludge.  
Keywords: Decontamination, Radioactive Cesium, Ocean Sludge, Micro-bubble, Microorganism, Zeolite 
1. INTRODUCTION
The Fukushima nuclear accident on March 11, 
2011, soil and water had been contaminated by 
radioactive cesium. Moreover, radioactive cesium 
was found in the ocean sludge in Tokyo Bay 
flowing from rivers. A report says radioactive 
cesium is still existing in seashore in Tokyo Bay, 
2015 in [1]. Cesium which is adsorbed to the 
sludge cannot be easily removed.  
One of the authors developed decomposition 
and purification system, a circulation-type system 
by micro bubbles, that is, by creating aerobic state, 
aerobic bacteria are activated resulting to 
decomposition and purification of ocean sludge. 
Based on the hypothesis that radioactive cesium is 
adsorbed on the surface of the sludge deposition. It 
is considered cesium can be eluted after 
decomposing the deposited sludge.   
Once the cesium is eluted in the water, it can 
fix to a mineral such as zeolite. Now we need the 
properties of sludge in removal process by 
decomposition system with circulation type.  
In this study, our object is to check the 
characteristics of the sludge particle in removal 
process of radioactive cesium from ocean sludge 
by decomposition system with circulation type 
using micro bubbles and activating 
microorganisms.  
1. DECOMPOSITION SYSTEM WITH
CIRCULATION TYPE
It is very important to reduce sedimentary 
sludge in the ocean. Plans to reduce the sludge are 
usually dreading or sand covering. Dredging is a 
simple way and aims to cut off the sludge. But 
after cutting off, treating the dredged sludge takes 
much more time and, of course, cost. Sand 
covering, in general, gives a big load to living 
organisms and the ecological system.  
Fig. 1 Purification System of Circulation Type 
So that, a more efficient way is needed to 
reduce the sludge while not imparting 
International Journal of GEOMATE, June, 2017, Vol.12 Issue34, pp. 51-56 
Geotec., Const. Mat. & Env., ISSN:2186-2990, Japan, DOI: http://dx.doi.org/10.21660/2017.34.2669 
実海域 
波浪
海波
潮流 
マイクロバブル発生装置 循環用ポンプ 堆積汚泥Experimental TankPumpMicro-bubble Generating
Sea Bottom
currentwave
International Journal of GEOMATE, June, 2017, Vol.12 Issue34, pp. 51-56 
52 
 
environmental load in the local sea area. Here, 
attention was paid to micro-bubble technology for 
application to the purification of the sludge. The 
important point in this technique is to activate the 
bacteria existing in the area by micro-bubbles.  
Micro-bubbles (that is MB) can change 
conditions into an aerobic state. If the bubbling 
stops, the situation changes into anaerobic state, 
according to recent research. So, we selected a 
method for decomposing the sludge by 
microorganisms. 
One of the authors had developed the 
decomposition system for ocean sludge with 
circulation type by micro-bubbles, shown in Fig.1, 
which decompose and purification sludge by 
activating the aerobic bacteria, after creating an 
aerobic state by micro-bubbles. 
 
 
1. MECHANISM ON FIXING OF CESIUM 
FROM ELUTION 
 
In general, ocean sludge has a negative charge. 
When cesium with a positive charge flows from 
river, sludge was adsorbed cesium, shown in Fig 2. 
So that, sludge adsorbed cesium cannot eliminate 
by usual way.  
 
 
 
 
 
 
 
Fig.2 Mechanism on Adsorption of Cesium 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig.3 Mechanism on Fixing of Cesium from 
Elution 
 
Here, we have a way by using of the 
decomposition system for ocean sludge with 
circulation type. After decomposition of the sludge 
adsorbed cesium by our system, cesium is eluted 
into water, shown in Fig 3. That is our hypothesis. 
 
2. ELUTION EXPERIMENTS FOR CESIUM 
 
4.1 Procedure of Experiments  
 
The experimental devices consist of two parts, 
shown in Fig. 4. The water circulates through two 
tanks. In a tank (Width40xLength28x Hight28cm), 
micro-bubbles are generated. The micro-bubbles 
have micro-size diameter and high solubility. This 
means the water with high concentration of 
dissolved oxygen circulates through these tanks. 
The other part is the experimental tank 
(W60xL29xH35cm). We used sea-water 30(litter) 
and sludge 1(kg). Here, a micro-bubble generator 
is based on [4], [5] and the flow rate is 900 
(litter/hour). The flow rate of water pumps 
connected each tanks are 300 (litter/hour).   
 
 
 
 
 
 
 
 
 
 
 
 
Fig.4 Experimental System for Elution of Cesium. 
 
We had caught the sludge and the sea water at 
Funabashi Port in Chiba Prefecture in JAPAN, as 
shown in Fig.4 and 5. Here, we had removed under 
10cm of the sludge from seabed before sampling 
as experimental procedure, because we have to 
remove the initial value of cesium in the sludge, 
from [3]. 
 
 
Fig.5 Catching Point of Sludge and Sea Water at 
Funabashi Port in Tokyo Bay. 
 
 
 
 
- - -
-
-
-
-
-
-
Sludge Cesium
-
-
-
-
-
-
-
-
-
Adsorption
Cs+
Cs+
Cs+
Cs+
Cs+
Cs+
Cs+
Cs+
Cs+
Cs+
Cs+
Cs+
Cs+
Cs+
Cs+
Cs+
Not elute
In the adsorbed 
state
Cs+
Cs+Cs+
Cs+
Cs+
Cs+ Cs+
Cs+
Cs+
-
-
-
-
-
-
-
-
-
Cs+
Cs+
Cs+
Cs+
Cs+
Cs+
Cs+
Cs+
Cs+
OKFixing of Cesium
Ｂｙ Usual Technology
for example: Zeolite,
Fiber for Adsorption etc.
Adsorption
Decomposition
of Sludge
Elution
 Cooler 
MB Generator Pump for Circulation 
Zeolite 
    
  
Tokyo Bay 
Yokohama 
Yokosuka 
Tokyo 
Tokyo Bay 
 
Funabashi Port 
Tokyo
Yokohama
 
   
International Journal of GEOMATE, June, 2017, Vol.12 Issue34, pp. 51-56 
53 
 
 
 
 
Fig.6 Scene of Catching Sludge. 
 
 
 
 
 
 
 
 
Fig.7 Procedure for Liquid Measurements. 
 
4.2 Measurement Procedure for Liquid Phase 
 
We used the cesium chloride before 24 hours 
of starting time and the concentration of cesium 
ion is 100 (ppm). A cooler for water tank was set 
at side of the tank for generating microbubbles, for 
the purpose of setting water temperature 30 degree 
centigrade.   
After setting the decomposition system with 
circulation type by micro-bubbles, experiment 
starts at the same time of generating micro-bubble 
device and also the zeolites were set in the tank. 
After 6 hour, the microorganism activator was 
put in the experimental tank. Main staff of the 
activator is Kelp and including nutrients and some 
enzyme. Our used activator is reported to show 
effective results in purification for grease trap.  
Measurements for liquid phase did each 6 
hours until 12 hours, and then every 12 hours 
to120 hours, shown in Fig.7.  
  Dissolved oxygen (DO), water temperature and 
pH are measured by using of multi-parameter 
water quality meter. Ammonium nitrogen (NH4-N), 
total nitrogen (T-N) and total phosphorus (T-P) are 
measured by using of digital-water-analyzer by 
digital “Packtest”, by water filtered after sampling 
in experimental tank. 
 
4.3 Experimental Condition 
 
Case 1 is to use our purification system with 
circulation type and Case 2 is not use the system 
which means do not use the micro bubble and 
activator of microorganisms.   
Case 3 is to do current velocity control in 
purification system for reducing hydrogen sulfide. 
As procedure of experiment in case of current 
velocity control by our purification system with 
circulation type, setting the water pomp (2400L/h) 
in a tank is worked from starting time to 24 hours 
later. 
3. RESULTS AND CONSIDERATION 
 
5.1 Results and Consideration for Liquid Phase 
 
5.1.1 Results of water temperature, pH and DO as 
environmental condition 
 
Fig.7-9 show the water temperature, pH and 
DO (Dissolved Oxygen) as the results of 
environmental condition of this experiment. 
Water temperature was almost constant about 
30 degree centigrade after 6 hours, by setting the 
cooler for water tank in the experimental system. 
pH was also constant about 8.0 to 9.0. DO in Case 
1 and 3 were 7.0 to 8.0 and also saturation state 
after 24 hours, but DO in Case 2 was about 4.0 and 
lower oxygen state.    
 
 
 
 
 
 
 
 
 
 
 
 
Fig.7 Changes in Water Temperature as 
Environmental Conditions. 
 
 
 
 
 
 
 
 
 
 
 
 
Fig.8 Changes in pH as Environmental Conditions. 
 
 
 
 
 
 
 
 
 
 
 
 
Fig.9 Changes in DO as Environmental Conditions. 
 
5.1.2 Results of H2S, DIN and T-N 
 
Fig.12-14 are shown in results of H2S 
Set Activator of 
Microorganisms
Set Sea Water, Sludge 
and Cesium 
0h 24h 48h
Start
Generate MB
72h 96h-24h 120h6h
W
a
te
r
 T
e
m
p
e
r
a
tu
r
e
 [
℃
] 
International Journal of GEOMATE, June, 2017, Vol.12 Issue34, pp. 51-56 
54 
 
(Hydrogen sulfide), DIN (Total Inorganic 
Nitrogen) and T-N (Total Nitrogen).   
H2S (Hydrogen sulfide) in Case 1 and 3 
decrease rapidly, it seemed by the supply of 
Oxygen. It decreased more rapidly in Case 3 by 
flow control and then became N.D. value. Case 2 
showed not big change and relatively constant 
values, because of no supplying oxygen.  
 
 
 
 
 
 
 
 
 
 
 
Fig.10 Changes in H2S. 
 
DIN (Total Inorganic Nitrogen = NH4-N+NO2-
N+NO3-N), shown in Fig. 11. DIN of Case 1, 3 
reduced 100% at 120 hours, it seemed it happen to 
denitrification by microorganism from [7]. 
 
 
 
 
 
 
 
 
 
 
 
Fig.11 Changes in DIN. 
 
T-N (Total Nitrogen) is expressed in 
normalization; initial values in Case 1, 2 and 3 
were 
4.0, 1.5, 4.3, respectively. T-N in Case 1 and 3 
reduced 80 and 85 %, respectively. It seems these 
are activated by microorganisms. A little high 
values in Case 3 caused rapidly decreasing of H2S 
by flow control, so that it seems purification 
efficiency is very good. 
 
 
5.2 Results and Consideration for Solid Phase 
 
5.2.1 Measurement Procedure for Solid Phase 
 
Measurements for solid phase did every 24 
hours to120 hours, shown in Fig.13. There are 6 
patterns; 0, 24, 48, 72, 96, 120 hour. When it 
comes each closing time, the experimental tanks 
are prepared for measurement of solid phase. The 
sediment in the tanks are carried out filtration and 
dry. After filtration and dry, cesium in solid was 
analyzed by the energy dispersion type X-ray 
analysis device (EDX).  
The characteristics of the sludge particle in 
removal process are also measured by Scanning 
Electron Microscope (SEM). 
 
 
 
 
 
 
 
 
 
 
 
 
Fig.12 Changes in T-N. 
 
 
Fig.13 Measurement Procedure for Solid Phase. 
 
 
5.2.2 Results of Cesium (solid) 
 
We paid attention to cesium and silica (Si), as 
there are many chemical elements in sludge. We 
used the energy dispersion type X-ray analysis 
device (EDX), because we can measure by the 
solid state. Weight ratio of cesium and silica 
(CS/Si) in solid of dry sludge are shown in Fig.15. 
Results of cesium in solid phase by EDX in 
Case 1 reduced 47.1% but in Case of 2 did not 
reduce. It seems cesium adsorbed on sludge was 
decomposed and eluted to water by decomposition 
and purification system of circulation type. 
 
 
 
 
 
 
 
 
 
 
 
 
Fig.15 Changes in (Cesium)/(Silica) in Solid Phase. 
 
0h 24h 48h
Start
Generate MB
72h-24h
Set Activator of 
Microorganisms
Set Sea Water, 
Sludge and Cesium 
Filtration 
and Dry 
6h
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 24 48 72 96 120
Case 1
Case 2
Time[hour]
C
s/
S
i
in
 S
o
li
d
 P
h
a
se
International Journal of GEOMATE, June, 2017, Vol.12 Issue34, pp. 51-56 
55 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5.2.3 Characteristics of Sediment by SEM 
 
Results of SEM (Scanning Electron 
Microscope) are expressed for each 24 hours from 
0 to 120 hours, shown in Fig.16 and 17. 
Diameter of sludge particle in Case 1 is 100 to 200 
(micro meter) when experiment starts, and then it 
becomes 5 (micro meter) at 120 hours later, so that 
the size became about 40 times small. That in Case 
2 denoted no change. It seems the diameter of 
sludge particle is decomposed and becomes very 
small according to the working time of 
decomposition and purification system of 
circulation type. 
 
 
4. CONCLUSION 
 
We had carried out the elution and fixing 
cesium by setting zeolite, after decomposing the by 
using the decomposition system with circulation 
type, by not using it and by using it adding flow 
control.  
From the results for water qualification, 
(1) for T-N, it decreased 80% in case of use the 
decomposition system and decreased 85% in 
adding flow control. 
From the results for cesium in solid phase, 
(2) the eluted performance of absorbed cesium on 
the sludge is indicated 47.1% by using the 
decomposition system, compared with no use 
of microbubble and activator of 
microorganisms.   
(3) Diameter of sludge particle in removal process 
by using the decomposition system became 
about 40 times small. 
 
 
5. ACKNOWLEDGEMENTS 
 
The authors would like to express sincere 
thanks for executing the experiments to Takahiro 
ARAKAWA and Taiyo KOKATSU, Students of 
Nihon University, in Japan. 
This work was supported by KAKENHI 
(Grant-in-Aid for Scientific Research (C-
0h                           24h                       48h                       72h                       96h                     120h   
100 - 200μm about 100μm 40 - 70μm about 20μm 
 
10 - 15μm about 5μm 
Fig. 16 Photo by SEM (Scanning Electron Microscope) of Case 1 (Upper=100 times / Lower=1000 times) 
No Subtilization, particle cannot be resolved through for 120 hours. 
0h                          24h                          48h                         72h                        96h                       120h   
Fig. 17 Photo by SEM (Scanning Electron Microscope) of Case 2 (Upper=100 times / Lower=1000 times) 
International Journal of GEOMATE, June, 2017, Vol.12 Issue34, pp. 51-56 
56 
 
26420831)). 
 
 
6. REFERENCES 
 
[1] Tokyo News Paper: Radioactivity pollution in 
the Tokyo Bay, “A nuclear power plant, far 
convergence”, March 10, 2015.  
http://www.tokyo- np.co.jp/feature/ 
tohokujisin/archive/fouryears/150310_1.html 
[2] Okamoto Kyoichi, Hotta Kenji, Toyama 
Takeshi and Kohno Hideki, “Purification 
System of Ocean Sludge by Activating 
Microorganisms”, International Journal of 
GEOMATE (Geotec, Const. Mat. & Env.), 
Vol.6, No.1, pp.791-795, March, 2014. 
[3] Okamoto Kyoichi and Toyama Takeshi,” 
Ocean Decontamination: Removal of 
Radioactive Cesium from Ocean Sludge by 
Using Micro bubbles and Activating 
Microorganisms”, The Japan Society of Naval 
Architects and Ocean Engineers, May, 2014. 
[4] Imai, T, Shioshige, K, Ukita, M, Sekine, M, 
Higuchi, T, Fukagawa, K and Fujisato, T, 
“Development of Device for Dissolving High 
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[5] Matsuo, K, Maeda, K, Ohnari, H, Tsunami, Y, 
and Ohnari, H., “Water Purification of a Dam 
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Progress in Multiphase Flow Research I, 
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[6] Okamoto Kyoichi and Toyama Takeshi, 
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Society of Naval Architects and Ocean 
Engineers, May, 2015. 
[7] Okamoto Kyoichi and Toyama Takeshi, 
“Ocean Decontamination: High Efficiency 
Removal Method of Radioactive Cesium from 
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Activating Microorganisms”, The Japan 
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[8] Okamoto Kyoichi and Toyama Takeshi, 
“Ocean Decontamination: Removal Efficiency 
of Radioactive Cesium from Ocean Sludge by 
using Microbubbles and Activating 
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GEOMATE (Geotec., Const. Mat. & Env), 
May, 2016, Vol. 10, Issue 21, pp. 1924-1928. 
 
 
 
 
 
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permission is obtained from the copyright 
proprietors.  


CHARACTERISTICS OF THE SLUDGE PARTICLES IN REMOVAL PROCESS OF RADIOACTIVE CESIUM FROM OCEAN SLUDGE BY DECOMPOSITION SYSTEM WITH CIRCULATION TYPE USING MICRO BUBBLES AND ACTIVATING MICROORGANISMS

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CHARACTERISTICS OF THE SLUDGE PARTICLES IN REMOVAL PROCESS OF RADIOACTIVE CESIUM FROM OCEAN SLUDGE BY DECOMPOSITION SYSTEM WITH CIRCULATION TYPE USING MICRO BUBBLES AND ACTIVATING MICROORGANISMS

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