EPA-600/3-77-083
July 1977
Ecological Research Series
MANAGEMENT OF BOTTOM SEDIMENTS
CONTAINING TOXIC SUBSTANCES
Proceedings Of The Second U.S.-
Japan Experts' Meeting October 1976
Tokyo, Japan
Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Corvallis, Oregon 97330
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal spe-
cies, and materials. Problems are assessed for their long- and short-term influ-
ences. Investigations include formation, transport, and pathway studies to deter-
mine the fate of pollutants and their effects. This wor|< provides the technical basis
for setting standards to minimize undesirable changes in living organisms in the
aquatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/3-77-083
July 1977
MANAGEMENT OF BOTTOM SEDIMENTS CONTAINING TOXIC SUBSTANCES
Proceedings of the Second U.S.-Japan Experts' Meeting
October 1976 -- Tokyo, Japan
edited by
Spencer A. Peterson and Karen K. Randolph
Corvallis Environmental Research Laboratory
Corvallis, Oregon 97330
CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330
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DISCLAIMER
This report has been reviewed by the Corvallis Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental Protection
Agency, nor does mention of trade names or commercial products con-
stitute endorsement or recommendation for use.
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FOREWORD
Effective regulatory and enforcement actions by the Environmental
Protection Agency would be virtually impossible without sound
scientific data on pollutants and their impact on environmental
stability and human health. Responsibility for building this data base
has been assigned to EPA's Office of Research and Development and its 15
major field installations, one of which is the Corvallis Environmental
Research Laboratory (CERL), Oregon.
The primary mission of the Corvallis Laboratory is research on the
effects of environmental pollutants on terrestrial, freshwater, and
marine ecosystems; the behavior, effects and control of pollutants in
lake systems; and the development of predictive models on the movement
of pollutants in the biosphere.
The United States-Japan Ministerial Agreement of May 1974 provided for
the exchange of environmental information in several areas of mutual
concern. This report is the compilation of papers presented at the
Second U.S.-Japan Experts' Meeting on the Management of Bottom
Sediments Containing Toxic Substances, which was hosted by the Japanese
Government in October 1976. The first meeting was held in Corvallis,
Oregon, in November 1975. The next session is scheduled for Washington,
D.C. in the fall of 1977.
A.F Bartsch, CERL Director
and U.S. Coordinator for the
U.S.-Japan Experts' Meeting
m
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CONTENTS
FOREWORD , ill
JAPANESE PAPERS
Dredging of Contaminated Bed Sediment in Japan 1
T. Sameshima
Countermeasures for Pollution in Tokyo Bay 20
T. Ohtsuka
An Experiment in Removal of Organically Polluted
Bottom Mud from the Seto Inland Sea 62
A. Murakami
The Mechanism of Methylmercury Accumulation in Fish .... 89
M. Fujiki, R. Hirota and S. Yamaguchi
Determination of Trace Amounts
of Methylmercury in Sea Water 96
H. Egawa and S. Tajima
Behavior of Heavy Metals and PCBs in Dredging
and Treating of Bottom Deposits 107
K. Murakami and K. Takeishi
A Study on the Behavior of Mercury-Contaminated
Sediments in Minamata Bay 127
T. Yoshida and Y. Ikegaki
Using Sand Fill to Cover Dredge Spoils Containing Mercury .144
S. Fuji no
Chemical Stabilization of Soft Soils 155
T. Okumura
A Method for Disposing of Waste Water at Dredged
Material Reclamation Sites 169
E. Satoh
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UNITED STATES PAPERS
Legal and Administrative Aspects
of Bottom Sediment Management 191
A.F. Bartsch
Hydraulic Dredging as a Lake Restoration Technique:
Past and Future 202
S.A. Peterson
Interchange of Nutrients and Metals Between Sediments and
Water During Dredged Material Disposal in Coastal Waters. .229
D.J. Baumgartner, D.W. Schults, S.E. Ingle
and D.T. Specht
Dredging Conditions Influencing the Uptake of
Heavy Metals by Organisms 246
J.F. Sustar and T.H. Wakeman
Dredged Material Densification and Treatment of
Contaminated Material 253
C.C. Calhoun, Jr.
Ecological Considerations in Site Assessment for
Dredging and Spoiling Activities 266
O.K. Phelps and A.C. Meyers
APPENDICES
Appendix A—Notes on Units of Measure and Methodology
Used by Japanese Authors 287
Appendix B--Turbidity and Suspended Solids Measurement
Methodology 288
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DREDGING OF CONTAMINATED BED SEDIMENT IN JAPAN
T. Sameshima*
Technical Counsellor
Bureau of Ports and Harbours
Ministry of Transport
ABSTRACT
Dredging of contaminated bed sediment has only
recently started in Japan. In the Sumida River,
Tokyo, the first dredging for the purpose of water
pollution control was undertaken in 1958. In 1971 a
dredging project initiated in Tagonoura port was the
first large scale management of accumulated bed
sediment in Japan. In 1972-73 the problem of fish
contamination was recognized and bed sediments were
investigated all over the country. Concurrently,
legal and adminstrative systems concerning pollution
control were gradually formulated, and removal of
contaminated bed sediments has been extensively under-
taken.
This paper discusses the progress of dredging,
present status of dredging, and the legal and adminis-
trative issues concerning pollution control, especially
the cost allocation system which has promoted pollution
control efforts.
INTRODUCTION
Since about 1955, when the Japanese economy began to grow rapidly after
the post-war confusion, water pollution has gradually become serious. The
over-concentration of population and industries in large cities such as
Tokyo, Osaka and Nagoya has generated much contaminated sewage which polluted
the water and the river beds running through these cities. At that time many
rivers were essentially dead. The waters were darkly colored, smelled bad
and devoid of fish.
In lakes such as Suwa and Kasunrigaura, where the water is neither suf-
ficiently circulated nor exchanged with outside water, eutrophication has
been accelerated due to nutrient salts which have flowed into and accumulated
in the lakes. Similarly, in the enclosed or semi-enclosed sea areas such as
the ports of Tokyo, Osaka, and Nagoya many rivers discharge waste water from
nearby factories. This has accelerated the pollution of the water and the
*Kobe District Bldg., Kaigandori, Ikuta-ku, Kobe 650, Japan
1
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bed sediment. At the same time toxic substances contained in effluents from
chemical factories and mines accumulated in the sea bed, river bed and agri-
cultural soil and have caused harmful effects on human health through consump-
tion of fish and plants.
At present, pollution is widely found even in the sea areas around the
bays of Tokyo and Osaka and in the Seto Inland Sea. However, restrictions on
discharging waste water and sewage and the removal of contaminated bed sedi-
ments are considered important efforts toward restoring the former clean
environment.
BACKGROUND OF DREDGING
Bed Sediment Contamination
Because of strengthened controls for waste water discharge and the
progress of sewage treatment systems the water quality of rivers and ports
has been gradually improved and the toxic substances environmental standard
for water quality is nearing reality. Some water areas, however, are still
considered polluted and cause fish contamination as a result of the accumu-
lated bed sediments which contain toxic substances.
In 1972-73 mercury and PCB contamination of fish was discovered. The
intensive accumulation of these substances in fish was caused by the fishes'
intake of bed sediment contaminated with these substances. At that time it
became an important administrative problem to cope with the pollution of bed
sediments. Accordingly, environmental pollution was intensively investigated
all over the country in 1972-74 by the Environment Agency, the Fisheries
Agency, the Ministry of International Trade and Industry, the Ministry of
Transport and the Ministry of Construction in cooperation with concerned
local governments. Fish, water, bed sediment and soil were investigated in
relation to their pollution by toxic substances such as mercury and PCB.
With regard to mercury contamination, bed sediment was investigated in
332 rivers, 155 ports and 148 sea areas. In total, 5,186 samples were col-
lected and tested from 635 locations. In addition 580 samples from 9 rivers
and 3 ports were investigated separately by local governments. The result
showed that 258 samples from 19 rivers and 11 ports were contaminated with
mercury according to the tentative criteria for removal of bed sediment (7-40
mg/kg) which was established in 1973.
PCB contamination of bed sediment was being investigated throughout
Japan in 1972-73. In 1972, out of 2,529 water areas examined, 87 were found
contaminated with PCB in excess of 10 mg/kg. In 1973, 1,789 samples were
collected and tested from 258 rivers, 38 ports and 58 sea areas. These 354
sample stations showed that 6 water areas were contaminated with PCB over 100
mg/kg, 8 water areas with 50-100 mg/kg, 11 water areas with 25-50 mg/kg and
26 water areas with 10-25 mg/kg (Figure 1, Figure 2).
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KANTO
KINKI
Figure 1. Mercury contaminated bed sediments (1973).
These investigations showed that contaminated bed sediments were distri-
buted all over the country, but contamination with mercury was found to be
heaviest in the districts of Kanto and Kinki; greatest contamination with PCB
was found in the Tokai and Hokuriku districts.
Bed sediments contaminated with organics were found in rivers running
through cities, especially in small, stagnant rivers, and also in canals,
creeks and small craft basins.
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TOKAI
Figure 2. PCB contaminated bed sediments (1973).
• PCB concentration (max) greater than 100 mg/kg
o PCB concentration (max) 25-100 mg/kg
Progress of Dredging Projects
Contaminated river bed sediments were first dredged 1n 1958 in the
Sumida River. Dredging bed sediment and projects for channeling fresh water
followed in rivers which ran through large cities such as Osaka and Fukuoka.
Except for small-scale maintenance dredging in ports located at the
mouth of large rivers, dredging of contaminated bed sediment in ports was
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first undertaken 1n the port of Tagonoura, Shlzuoka prefecture, where the
basin was contaminated and silted with pulp mill waste.
The pollution of Tagonoura port became widely known 1n Japan because the
bad odor from the waste water was offensive. So much waste was discharged
that 1t Interfered with port activities and damaged the nearby fishery.
This event prompted the establishment of the legal and administrative system
for anti-pollution 1n Japan.
At the end of 1970 the "Basic Law for Environmental Pollution Control"
was revised and the "Cost Allocation Law for Pollution Control Works," the
"Water Pollution Control Law" and the "Marine Pollution Prevention Law" were
enacted. Also 1n 1971 the "Law Governing Government's Special Financial
Measures Relative to Pollution Control Projects" was enacted.
In addition to establishing the legal system 1n 1971 the Environment
Agency was created to promote a comprehensive and positive environmental
administration which had formerly been under the control of several govern-
mental organizations. At that time dredging of bed sediment containing toxic
substances such as mercury became an urgent problem. Therefore, the Environ-
ment Agency established "a tentative criteria for removing bed sediment
contaminated with mercury," taking Into consideration the solubility of
mercury from bed sediments agitated by waves and currents, the concentration
of accumulated mercury in fish and shellfish, and the eating habits of local
Inhabitants.
Based on Investigation of the PCB concentration 1n bed sediment and
fish, "a tentative criteria for removing bed sediment contaminated with PCB"
was established 1n 1975 to be 10 mg/kg dry weight of bed sediment.
For dredging, 1t 1s Important to prevent secondary pollution such as
diffusion of contaminated bed sediment and leakage of toxic substances from a
spillway or containment wall. A "tentative guideline for managing contami-
nated bed sediment" was established in 1974. This Included a study of water
quality 1n selected areas which had already been dredged under the tentative
criteria and guidelines.
In addition to PCB and Hg it 1s also necessary to remove bed sediment
contaminated with organic compounds and oil. However, criteria for dredging
bed sediments contaminated with organic compounds and oil are not uniformly
determined yet, and Individual criteria for removing these sediments is left
to the Implementing organization according to local conditions.
In 1975 the Central and local governments began dredge projects for
pollution control 1n about 70 areas in addition to dredging done by private
enterprises at their own cost.
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TABLE 1. CHRONOLOGICAL TABLE CONCERNING DREDGING
1956 ° "Minamata disease" was officially reported.
1958 ° "The Law Concerning Water Quality Conservation of Public
Water" and "The Industrial Effluent Control Law" were enacted.
Dredging first undertaken in Sumida River.
1960 ° Fish with offensive odors were found in Yokkaichi port.
1967 ° "The Basic Law for Environmental Pollution Control" was enacted.
1970 ° Bed sediment in Tagonoura port was brought to public attention.
0 First "Environmental Pollution Control Program" was established
in three areas.
0 "Environmental Quality Standard Concerning Water Pollution" was
established.
0 "The Cost Allocation Law for Pollution Control Works," "The Water
Pollution Control Law" and "The Marine Pollution Prevention Law"
were enacted.
1971 ° "The Law Governing Government's Special Financial Measures
Relative to Pollution Control Projects" was enacted.
0 "The Environment Agency" was established.
0 Red tide increased rapidly in Seto Inland Sea.
0 First large scale dredging was undertaken in Tagonoura port.
1972 ° Dredging undertaken in Kitakyushu port.
1972-73 ° Mercury and PCB contamination of fish was publicized.
1973 ° "A Tentative Criteria for Removing Bed Sediment Contaminated with
Mercury" was established.
1972-74 ° Bed sediment was investigated all over the country.
1974 ° "A Tentative Guideline for Managing Contaminated Bed Sediment"
was established.
1975 ° "A Tentative Criteria for Removing Bed Sediment Contaminated with
PCB" was established.
Investigation and Research on Pollution Control
To promote the development of science and technology which will help
prevent environmental pollution, the Central government takes measures neces-
sary to establish an efficient survey and research program. Both Central and
local governments are studying pollution prevention techniques, the influence
of pollution on human beings and the environment, and monitoring and surveil-
lance techniques. Research is also undertaken by universities and private
firms. At present, pollution control problems are being studied by 53 nation-
al investigation and research institutes attached to 11 governmental organiza-
tions. The principal national institutes are shown in Table 2 with their
main research subjects.
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TABLE 2. PRINCIPAL NATIONAL INSTITUTES AND THEIR MAIN STUDIES
CONCERNING POLLUTION CONTROL
Institute of Public Health
(Ministry of Health and Welfare)
Influence on human health by air pollution
Behavior of sediments containing heavy metals
Mechanism of photochemical reactions
Industrial Health Institute
(Ministry of Labour)
PCB concentration and accumulation in human bodies
Regional Fisheries Research Laboratory
(Ministry of Agriculture and Forestry)
Influence on fishery products by thermal effluent
National Institute of Agricultural Science
(MAF)
Influence on farm products and fish by environmental pollution
Regional Institute of Industrial Technology
(Ministry of International Trade and Industry)
Environmental protection in the Seto Inland Sea
Monitoring technique for water pollution in coastal areas
Treatment techniques on waste water containing heavy metals
Geological Survey Institute
(MITI)
Treatment techniques on mine drainage
National Research Institute for Pollution and Resources
(MITI)
Dispersion mechanism of smoke
Surveillance of water pollution
Treatment technique for automobile exhaust gas
Treatment and utilization of sludge
Port and Harbour Research Institute
(Ministry of Transport)
Treatment technique for contaminated bed sediment
Pollutant diffusion due to tidal currents
Traffic Safety and Nuisance Research Institute
(MOT)
Purification of automobile exhausts
Meteorological Research Institute
(MOT)
Methods of measuring air pollution
Environmental impact assessment concerning air pollution
Public Works Research Institute
(Ministry of Construction)
Treatment technique of contaminated bed sediment
Nitrogen removal technique at sewage treatment facility
These national institutes are studying various pollution problems arising
from public activities under their jurisdiction, while the Environmental
Agency comprehensively coordinates these studies to promote them efficiently.
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In 1974, the National Institute for Environmental Pollution Research was
established as a central institute of investigation and research on pollution
control in Japan. This institute is attached to the Environment Agency. In
this institute, influence on human health by environmental pollution, the
process of environmental pollution and monitoring, and surveillance techniques
for environmental pollution are being studied. Investigation and research on
the management of contaminated sediments are being studied by the Fisheries
Agency, the Ministry of Transport and Ministry of Construction.
The Division of Investigation and Development, the Fisheries Agency, and
the Ministry of Agriculture and Forestry are studying techniques for prevent-
ing the red tide which often occurs in coastal areas. Red tide is most
likely due to eutrophication and is not only harmful to commercial marine
products but is also destructive to the remainder of the ecosytem. With a
view to preventing fishery damage, a withdrawl technique on the red tide and
a removal of the bed sediment which is assumed to cause the red tide are
being studied in the field.
Port and Harbour Research Institute, Ministry of Transport, is studying
dredging and transportation of contaminated bed sediment, especially turbidity
due to dredging and dumping of dredged materials. It is also developing
dredge and sediment treatment equipment.
Public Works Research Institute, Ministry of Construction is studying
properties of bed sediment and the management techniques for bed sediment,
especially bed sediment contaminated with heavy metals and PCB.
In addition to these governmental organizations, many private firms are
studying management techniques for contaminated bed sediment including devel-
opment of dredges, treatment of muddy water and spill water, and prevention
of leakage at diked spoils areas.
PRESENT STATUS OF DREDGING
Rivers are under the control of the River Bureau, Ministry of Construc-
tion. Dredging of contaminated bed sediments in rivers was put into practice
by the Central and local governments in 1958 before a legal and administrative
program concerning pollution control was established. Both dredging of bed
sediment and improved water systems have been undertaken for water purifica-
tion in rivers adjacent to large cities, for example the Sumida River in
Tokyo and the Kanzaki River in Osaka. Good results were obtained and recently
these projects have been undertaken all over the country.
The total volume of bed sediment removed from 1958 to 1975 is about 12
million cubic meters and from 1958 to 1968 the average volume of sediments
removed was about 500 thousand cubic meters annually. Recently, the volume
increased to 600-1,200 thousand cubic meters annually. In 1975 dredging was
done in 53 rivers and lakes such as the Tama River, the Kanzaki River and the
Suwa Lake, and a sediment volume of about 700 thousand cubic meters was
removed at the expense of 1,945 million yen.
8
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The cost of dredging is borne by those enterprises responsible for the
pollutants to the extent of their responsibilities and the remaining cost is
publicly shared. Generally, bed sediments in rivers are polluted by many
unspecified activities as well as sewage. Dredging is usually undertaken for
both river improvement and pollution control. Therefore most dredging in
rivers is executed by the Central or local government.
In a Class "A" river which is controlled by the Central government,
excluding certain designated sections, the Central government implements
river improvement projects directly, which includes dredging of bed sediments.
The cost of such projects is shared equally by the Central and local govern-
ments. In the case of designated sections of Class "A" rivers and Class "B"
rivers, the local government executes river improvement works; one-third of
the cost is subsidized by the Central government and the remaining two-thirds
is borne by the local government.
If the dredging is listed in the environmental pollution control program,
or designated by the Minister of Domestic Affairs as projects to prevent or
control pollution, the cost of such projects is shared equally by the Central
and local government. For dredging in rivers, shovel type dredges are used
in addition to suction and grab type dredges, depending upon the volume and
quality of the sediment and surrounding local conditions. Dredge spoils are
usually disposed of in containment areas in the sea and, in some cases, in a
dry riverbed or on farm land. It is becoming more difficult to find disposal
sites, especially inland.
Dredging in Ports
Ports are under the control of Ports and Harbours Bureau, Ministry of
Transport.
In Tagonoura port, dredging of contaminated bed sediment was first
undertaken by the Shizuoka prefecture! government in 1971. Since then dredg-
ing of contaminated bed sediments in ports has been executed by port adminis-
trations in 16 ports and is already complete in the ports of Mikawa, Sakata,
Matsuyama and Aburatsu.
The total volume of bed sediment removed during 1971-75 was 4.5 million
cubic meters. In 1976, removal projects were begun in 12 ports such as
Tokyo, Osaka and Ohmuta and about 700 thousand cubic meters of sediment were
removed in a year at a cost of 8.2 billion yen. The Central government and
the port administration bear the costs equally and in each case the enterprise
responsible for pollution bears a part of the cost. Both of the government
agencies bear the remainder half-and-half. Dredging done by private enter-
prises at their own cost have already been completed in ports of Chiba (Hg),
Kawasaki (Hg), Higashiharima (Hg), Tokuyama-kudamatsu (Hg), Shimonoseki (Cd),
Tsuruga (PCB), Mikawa (PCB), Iwakuni (PCB), and so on.
For dredging in ports, suction type and grab type dredges are widely
used. Bed sediments are carried by barge, pipe and truck and are usually
disposed into containment areas in the sea. From 1976 to 1980, port improve-
ment works are being carried out along the 5th Five-Year Port Improvement
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Plan which was formulated according to the national economy plan. Pollution
control works in port will be carried out in parallel with improvement of
port facilities based on this plan. These works will be executed in 29 ports
including work in progress during this five years (Figure 3).
RUMOI-
MINAMATA
SAKATA
AMAGASAKI
OSAKA
• Completed or under construction
o Planning
(Excluding particular works of
private enterprises)
HIGASHIHARIMA
HIMEJI^
MIZUSHIMA
KURE
OHTAKE
IWAKUNI
M/TAJ/R*
UBE-
KITAKYUSYU
OHMUTA
HACHINOHE
SHIOGAMA
TOKYO
WASAKI
YOKOHAMA
TAGONOURA
MIKAWA
\GOYA
YOKKAICHI
WAKAYAMA
IMABARI
MATSUYAMA
ABURATSU
SAEKI
Figure 3. Distribution of ports undertaking removal works (dredging)
In this five-year plan, the total volume of contaminated bed sediment to
be removed in 26 ports is estimated at about 12 million cubic meters and the
area of contaminated bed sediment to be covered with good soil in Nakatsu and
Ohmuta port is estimated at about 500 thousand square meters. Total cost of
10
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these works amounts to about 59 billion yen. Of the total cost, 14 billion
yen (23.7%) will be borne by the Central government, 14 billion yen (23.7%)
by port administration and 31 billion yen (52.6%) by responsible enterprises.
In 14 out of 28 ports a part of the cost of these works will be borne by
responsible private enterprises. The outline of dredging projects in ports
is shown in Table 3.
Dredging in Other Water Areas
There are a few examples of dredging works in water areas other than
rivers, lakes and ports. In fishing ports which are under control of the
Fisheries Agency, local governments execute dredging projects as pollution
control projects with subsidy from the Central government. For example, in
1975-76 a bathing beach was created from a dredging project using contaminated
bed spoils covered with good sand.
LEGAL AND ADMINISTRATIVE PROGRAM FOR POLLUTION CONTROL PROJECTS
Both regulation of effluent discharges, smoke, soot and exhaust fumes
and execution of pollution control projects such as dredging contaminated bed
sediment are required to prevent environmental pollution and to preserve a
good environment. Regulation of effluent is prescribed by the Water Pollution
Control Law and regulation of smoke, soot and exhaust gas is prescribed by
the Air Pollution Control Law. Matters concerning pollution control works
are given in the Basic Law for Environmental Pollution Control and the Cost
Allocation Law for Pollution Control Works. The latter two laws, with ex-
amples of cost allocations, are presented in this chapter.
The Basic Law for Environmental Pollution Control
The Basic Law for Environmental Pollution Control was enacted to identify
the responsibilities of private enterprise, the Central government, and local
government with regard to environmental pollution control, and to determine
the fundamental requirements for control measures to promote comprehensive
policies for coping with environmental pollution, thereby ensuring the protec-
tion of public health and conservation of the living environment.
This law mainly defines fundamental policies for environmental pollution
control. Specific applications for particular control are left to individual
laws such as the Water Pollution Control Law, the Air Pollution Control Law,
etc. except for the establishment of Environmental Quality Standards and
formulation of Environmental Pollution Control Programs in accordance with
the Basic Law.
Environmental Quality Standards
At present Environmental Quality Standards, which are maintained for the
protection of human health and for the conservation of the living environment,
are established with regard to six environmental factors: air pollution,
carbon monoxide, sulfur dioxide, noise, aircraft noise and water pollution.
11
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TABLE 3. PLAN OF REMOVAL PROJECTS IN PORTS
ro
Port
Tokyo
Kawasaki
Yokohama
Nagoya
Yokkaichi
Wakayama
Osaka
Himeji
Kitakyushu
Hachinohe
Shiogama
Tagonoura
Amagasaki
Working
Period
1978-79
1980-81
1973-78
1972-81
1974-78
1978-79
1973-81
1974-80
1972-81
1979
1972-77
1972-77
1977-81
Removal
Volume m3
2,400,000
300,000
690,000
738,870
2,200,000
100,000
1,645,000
460,000
3,300,000
113,000
47,000
1,720,000
200,000
Polluting
Substances
organic compound
& sulfide
ditto
organic compound
& sulfide
organic compound,
sulfide & mercury
oil & mercury
organic compound
organic compound
organic compound
organic compound
& mercury
organic compound
organic compound
organic compound
& PCB
organic compound
Main
Polluter
unspecified
unspecified
unspecified
unspecified &
chemical ind.
oil refinery &
chemical ind.
unspecified
unspecified
sewage &
leather ind.
steel &
chemical ind.
sewage
aquatic food ind.
pulp ind.
sewage
Dredge
Type
grab
grab
grab
grab &
suction
suction
grab
suction
suction
grab
grab
grab
grab &
suction
suction
Transportation
Method
barge
barge
barge
barge &
pipe
pipe
barge
barge &
pipe
barge &
dump truck
barge
barge
barge
dump truck
& pipe
barge &
dump truck
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TABLE 3. (CON'T.)
Port
Higashiharima
Mizushima
Kure
Takamatsu
Toyo
Imabari
Iwakuni
Mi ta j i ri
Ube
Saeki
Mi namata
(Make
Rumoi
Working
Period
1978-79
1972-79
1978-79
1978-79
1977
1978-79
1979-80
1976-78
1978-79
1977-81
1974-83
1978-81
1979-80
Removal
Volume m3
50,000
813,000
200,000
397.000
20,000
30,000
372,000
444,500
492,000
805,000
1,675,000
890,000
15,000
Polluting
Substances
organic compound
oil
organic compound
& sulfide
organic compound
& PCB
organic compound
& sulfide
organic compound
organic compound
organic compound
organic compound
organic compound
mercury
organic compound
organic compound
Main
Polluter
sewage
oil refinery,
chemical & steel ind.
pulp ind.
pulp ind.
& sewage
sewage
sewage
pulp & oil ind.
pulp & textile ind.
pulp & chemical ind.
pulp ind.
chemical ind.
pulp & chemical ind.
sewage
Dredge Transportation
Type Method
suction
suction
suction
suction
grab
grab
grab or
suction
suction
suction
or grab
suction
suction
suction
dragline
barge &
dump truck
barge &
pipe
barge &
pipe
barge &
pipe
barge
barge
barge &
pipe
pipe
pipe or
barge
pipe
pipe
pipe
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For example, the Environmental Quality Standard concerning water pollu-
tion (which is an environmental quality standard relating to the health of
human beings) prescribes the concentration of toxic metals such as cyanides,
alkyl mercury, organic phosphorus, cadmium, lead, hexavalent chromium, arsen-
ic, total mercury and polychlorinated biphenyls. This standard should soon
be achieved and maintained uniformly throughout the rivers, lakes and seas.
The environmental standard prescribes water quality in terms of hydrogen-
ion concentration (pH), chemical oxygen demand (COD), dissolved oxygen (DO),
number of coliforms and normal hexane extraction according to 3 types of
water utilization in rivers, and 6 types of water utilization in lakes and
seas. The types of water areas were classified by the Central or local
government according to local conditions of water use. This standard is to
be achieved as soon as possible and then is to be maintained.
Environmental Pollution Control Program
The Prime Minister instructs the concerned prefectural governors to
formulate a program relating to environmental pollution control measures to
be implemented in specific areas where environmental pollution is serious or
likely to become serious, and where it is recognized that it will be extremely
difficult to achieve effective environmental pollution control unless compre-
hensive control measures are taken.
Pollution Control Programs were first established in 1970 in three areas
where adequate measures against pollution were required. These are Chiba-
Ichihara (Chiba pref.), Yokkaichi (Mie pref.) and Mizushima (Okayama pref.).
Since then, programs have gradually been established in 38 areas (second to
sixth program) and at present the basic policy has been promulgated to 9 more
areas (seventh program) by the Prime Minister. The national share of manu-
facturers' shipments and population in the 41 areas where these programs are
already established is 70% and 50%, respectively. These programs are already
established in most of the main industrial areas in the country.
Specific measures to be carried out by governments for pollution control,
such as a green buffer zone and removal of contaminated bed sediments, are
prescribed in these Pollution Control Programs, and the Central and local
governments are obligated to take necessary measures for the full implementa-
tion of these programs.
Cost Allocation of Pollution Control Projects
The Central and local governments promote necessary projects for the
prevention of environmental pollution in addition to private enterprise,
which is responsible for taking necessary measures for the prevention of
environmental pollution resulting from specific industrial activities. After
private industry pays its share for pollution control projects the remainder
is paid for at public expense according to the Cost Allocation Law for Pollu-
tion Control Works and the Basic Law for Environmental Pollution Control.
These projects are performed by the local governments.
14
-------
Cost Allocation Law for Pollution Control Works
The Cost Allocation Law for Pollution Control Works was enacted pursuant
to the Basic Law for Environmental Pollution Control and provides for proper
consideration of the scope of pollution control projects, the responsible
private enterprise and the extent of costs to be borne by the responsible
private enterprises.
Dredging of bed sediment, water conducting projects and/or any other
projects undertaken in rivers, lakes, ports or any other public water areas
where water is polluted, are defined as pollution control projects. The cost
of pollution control projects, in principle, shall be allocated to each
enterprise in proportion to the degree and extent of pollution which arises
from its individual activities.
The law prescribes that the scope of the enterprise liable to bear the
cost of pollution control projects shall be the enterprise which is definitely
considered to engage in individual activities which cause or will cause
pollution in the area where the said projects take place. According to these
rules, the implementer (the Central or the local government) must determine,
after hearing the opinion of the Council (which consists of men of learning
and experience), a cost allocation plan which includes (1) the kind of pollu-
tion control (2) the criteria to be used to determine the enterprises that
are to bear the cost (3) the cost of the pollution control projects (4) the
total amount to be borne by the responsible enterprise and the basis of
computation and (5) any other matters necessary to execute the pollution
control project.
In case of any work listed in the Environmental Pollution Control Program
or any work designated by the Minister of Domestic Affairs as work for preven-
tion of pollution, the local government is to be given necessary financial
subsidy by the Central government according to the Law Governing Government's
Special Financial Measures Relative to Pollution Control Projects.
Example of Cost Allocation
According to the Cost Allocation Law for Pollution Control Works, pollu-
tion control projects were put into practice as shown in Table 4 from May
1971 (when the law went into effect) to February 1976. This table shows the
total cost of pollution control projects at about 68 billion yen and the
total cost borne by responsible enterprises is about 38 billion yen. There-
fore, the total cost borne by responsible private firms accounts for 56.4% of
all costs.
These projects consist of 19 pollution prevention projects for removing
bed sediment, 6 pollution prevention projects for managing soil (such as top-
soil replacement at a farm) and 7 installations for green buffer zones. The
percent of the total cost borne by private enterprises accounts for 71.1% in
removal works, 74.4% in top-soil replacement and 28.9% in green buffer zone
projects. The reason why the cost-sharing ratio is so low in the case of the
green buffer zone is that in cases of sediment removal and top-soil replace-
ment, the enterprises that bear the cost are limited in number and the pollu-
15
-------
TABLE 4. LIST OF POLLUTION CONTROL WORKS WHERE THE COST ALLOCATION LAW APPLIED
(MAY 1971 - FEB. 1976)
cr»
Area
Dredging of bed sediment
---Ports---
Tagonoura (Shizouka) 1st
2nd
Kitakyushu (Fukouka)
Shiogama (Miyagi)
Mizushima (Okayama)
Ohmuta (Fukuoka)
Yokkaichi (Mie)
Sakata (Yamagata)
Mlnamata (Kumamoto)
— Rivers —
Ta (Tochigi)
Tempaku (Mie)
Tsusen & Kurinoki (Niigata)
Hama (Miyazaki)
Nakanoi & Yamanol (Fukuoka)
Hanamune & Yamanoi (Fukuoka)
Ohe (Aichi)
Chigiri (Ehime)
Kuroda (Osaka)
— Water Ways —
Sada (Osaka)
Sakamoto (Osaka)
Total Cost
Million Yen
500
1,885
1,800
420
2,800
4,430
5,500
670
19,335
22
28
400
1,550
6
17
1,302
50
32
3
10
Percentage
Paid by Private
Enterprise*
25
25
71
6.65
77.4
77.42
83.28
76.3
65
32.6
43.8
67
75
75.44
75.44
57.4
63.2
54.9
60.8
67.4
Number of
Enterprises**
158
154
19
8
21
6
48
2
1
4
11
11
2
7
7
2
12
11
1
1
Working
Period
1971
1971-77
1972-73
1972-80
1973-77
1973-75
1974-77
1974-75
1974-83
1971-73
1971-80
1971-74
1972-77
1973
1973
1973-77
1973-74
1974
1973
1974
Polluting
Substances
SS
Cd, As, Hg, SS
SS
Oil
Cd, Hg, SS
Oil, Hg, SS, COD
Hg •
Hg
SS
SS
SS
Hg
PCB
PCB
Hg
SS
SS
SS
Cu
-------
TABLE 4. CONTINUED
Area
Total Cost
Million Yen
Percentage
Paid by Private
Enterprise*
Number of
Enterprises**
Working Polluting
Period Substances
Top-Soil Replacement Projects
Usui (Gumma)
Ikuno (Hyogo)
Nakano (Nagano)
Kariya (Aichi)
Aizu (Fukushima)
Tsubokawa (Aomori )
Installation Projects for
Mizushima (Okayama)
Himeji (Hyogo)
Ohe (Aichi)
Tokai (Aichi)
Jonan (Hyogo)
Sakaide (Kagawa)
Tokuyama (Yamaguchi)
913
428
132
1,500
408
57
Green Buffer Zone
7,290
6,629
1,302
1,447
436
4,373
3,226
75
75
60
74.9
75
75
25
33.3
57.4
33.3
25
25
33.3
1
1
1
2
1
1
62
15
2
undecided
19
8
3
1972-75
1973-74
1973-74
1973-74
1974-76
1975-76
1971-77
1973-76
1973-77
1973-77
1971-73
1974-77
1975-78
Cd
Cd
Cd
Cd
Cd
Cu
Air Pollution
Air pollution,
noise
Air pollution
Air pollution,
noise
Air pollution,
noi se
Air pollution
Air pollution,
noise,
offensive odor
Remarks: * Percentage of the cost to be borne by private enterprise
** Number of enterprises liable to bear the cost of the works
-------
tion sources are comparatively definite. Green buffer zone pollution sources
are usually very broad and the projects will produce additional benefits
other than pollution control, for instance, a park.
An example of a cost allocation plan in Yokkaichi port
The port of Yokkaichi is located in the central part of Japan and faces
the northern section of Ise Bay. In the uninhabited portion of the port many
oil refineries and oil chemical plants have been located since 1953 and at
present the Yokkaichi area is one of the largest petrochemical complexes in
Japan. Bed sediment in the south of this port has been polluted by industrial
effluents containing oil and mercury. Since 1960 fishes were found to be
contaminated and have offensive odors. Because of these matters, the Yokka-
ichi Port Administration decided to remove the contaminated bed sediment
under the environmental pollution control program. This work, begun in 1974,
will take 4 years and cost 5.5 billion yen. The sediment to be removed is
estimated at 2.2 million cubic meters.
In figuring the cost allocation of this work, enterprises which had to
bear the cost of the pollution control work were determined by considering
the following three conditions, all of which must be simultaneously satisfied.
The first one is enterprises which are located in the designated area, the
second one is enterprises with effluents of more than 50 cubic meters per
day, and the third one is enterprises from which effluents are judged to have
influence upon bed sediments which are to be removed from April 1, 1960 to
March 31, 1972.
Then the weight of pollution factors in the cost of the project was
determined. In considering the purpose of the project, the process of the
sediment formation, the influence to the sea and the marine ecosystem, and so
forth, these factors were determined to be 40% for mineral oil, 10% for
mercury, 25% for SS and 25% for COD. Then each item to be borne by the
private sector and public sector was determined as follows:
Private Sector
(a) Mineral oil, total mercury, SS and COD from effluents from the
responsible private enterprises
Public Sector
(a) SS and COD from rivers
(b) SS and COD from domestic sewage
(c) Total mercury from agricultural effluent and domestic sewage
(d) Mineral oil, SS and COD from effluent from exempt enterprises
(e) SS and COD from effluent from bankrupt private enterprises
(f) Mineral oil from ships and others
After the above process, each cost to be borne by private enterprises
and the public sector was determined as shown in Table 5.
In the case where the responsible private enterprises share part of the
cost of a project, a cost allocation plan is fairly determined after careful
consideration by the Council, and then the cost allocation plan is officially
18
-------
announced. According to this system, which is based on the so-called "pollu-
ter pays" principle, pollution control projects are extensively and fairly
implemented. It is expected that the environment is becoming improved in
harmony with economic and social development in Japan.
TABLE 5. COST ALLOCATION IN PORT OF YOKKAICHI
Items
Percentage
to be borne
Cost to be borne
in thousand yen
Private
Enterprises*
Factory Waste Water
83.28
4,580,400
exempt portion from
factory waste water**
waste water from
exempt enterprises***
Public Sector waste water from
6.77
0.46
bankrupt enterprises****
domestic sewage
river water
ships and others
Sub Total
Total
0.09
5.17
3.12
1.11
16.72
100.00
919,600
5,500,000
Remarks: * Number of private enterprises to bear the cost is 48.
** The cost to be borne is partly exempted in consideration
of the period when the enterprises were not responsible.
*** Small scale enterprises from which effluents are less
than 50 cubic meters per day are exempted from bearing
part of the cost.
**** Enterprises which have gone bankrupt are exempted from
bearing the cost.
As stated above, the cost of pollution control works is usually borne by
both responsible enterprise and the public sector and, in some cases, borne
by either the responsible enterprise or the public sector, depending upon the
cause of the pollution, the responsible period of the enterprise and so
forth.
19
-------
COUNTERMEASURES FOR POLLUTION IN TOKYO BAY
T. Ohtsuka*
2nd District
Port Construction Bureau
Ministry of Transport
ABSTRACT
Tokyo Bay has been instrumental in the development
of the Metropolitan area. However, its quality as a
resource has been decreasing with the area's rapid
industrialization and urbanization. To improve its
quality it is essential to improve the Bay environment.
This paper will discuss the impact of pollution on
bottom sediment quality, its purifying function, and
the effect of improvement projects on the environment.
OUTLINE OF TOKYO BAY
Geography, Topography
The geographic characteristics of Tokyo Bay (the water area to the north
of the line connecting Kannonzaki of Yokosuka City and Isone Point of Chiba
Prefecture) are shown in Table 1.
_ TABLE 1. GEOGRAPHIC CHARACTERISTICS OF TOKYO BAY _
Length Approx. 61 km
Width Approx. 34 km
Maximum Depth Approx. 70 m at Old Tokyo River of the Uraga Channel
and approx. 40 m at the south end of Nakanose.
Average Depth Approx. 15 m (steep slope from 5 to 10 m, approx. 8%
from 10 m to 40 m) sloped from northeast to southwest.
Length of the Coastline Approx. 170 km «
Water Area Approx. 1,200 km (Futtsu Point)
Shoreline Configuration Approx. 1.51 (the bay becomes closer to a circle as
Index the number is closer to 1)
SCI _ _ S_ S = measured perimeter of the bay
a = calculated circumference of a
circle having the same area as the
3 irregular measured perimeter(s).
Volume Approx. 18.3 kg
Amount of Fresh Water q 3
Flowing into Tokyo Bay Approx. 9.98 x 10 m /y _
*l-2-5 Takashima-cho, Nishi-ku, Yokohama 220, Japan
20
-------
The length of the Bay is large in comparison to the mouth of the Bay.
The water is generally calm and mixing is limited. Characteristic of an
enclosed bay, it easily becomes eutrophic.
The coastal area from Yokohama through Tokyo, Chiba and Ichihara has
been reclaimed for ports, harbors, industrial sites and housing sites, and
thus has lost the characteristic of a natural waterfront. On the other hand,
the coastline from Yokohama to Kannonzaki and from Sodegaura to Futtsu exclud-
ing Kisarazu, still retains the natural characteristics.
The sea bottom topography shows distinctive characteristics divided by
the line connecting Honmoku Point and Futtsu Point. The sea bottom north of
the line shows primarily the geographical characteristic of accumulation.
The water depth is less than 40 meters and the sea bottom topography is
nearly uniform. The sea bottom geology in this area consists of sand in the
shallow part and mud in the deep part, with the boundary at the steep slope
from 5 to 10 m. In Tokyo Bay, the reclamation is concentrated mostly on the
area with a water depth of less than 5 m. The area south of the line has a
water depth of about 5 m with exposed bed rock and fewer deposits. The map
below shows the topography of Tokyo Bay.
Sumidagawa
Rl\
Tokyo.'.
Mfba
JCHIHARA
Tamagawa Ri
Kawasaki . /.:2
Yokohama ;J&&
FUTTSU
'fsbnemisaki
Yokosuka ••••:*
Kannonzak'i-':^
Kenzaki
WATER DEPTH IN METERS
TOPOGRAPHICAL MAP OF TOKYO BAY BOTTOM
21
-------
Present State of Water Quality
About 10 billion cubic meters of water flow into Tokyo Bay from the
rivers each year. This means that fresh water equaling approximately half
the volume of Tokyo Bay (18.3 billion cubic meters) flows into the Bay each
year. The fresh water inflow is becoming more polluted each year; in particu-
lar pollution by ammonium nitrogen has been increasing. As a result ammonium
nitrogen has been increasing in the Bay. The concentration of COD, BOD and
ammonium nitrogen is highest during the winter months of February and March
and lowest during July and September. It seems that this is due to the
seasonal change in the quantity of river water flow.
Let us look at the water quality in the sea area. First, the water
temperature ranges from 6°C to 28°C during a year. Since clarity is deter-
mined by such factors as the quantity of plankton and pollutants, it is used
as the most convenient index of water pollution. Figures 1 and 2 show the
yearly change of clarity. At the deep end of the Bay, the clarity used to
average 3 to 4 meters; it started to decrease from 1958 to 1960. Today it is
about 2 meters. Similarly, it was 3.5 to 4.5 meters in the middle of the
Bay; today it is about 3 meters. Seasonally it decreases to less than 1
meter in July when red tides appear frequently. Then, it recovers from fall
to winter as plankton populations decrease. Clarity is greater at the mouth
of the Bay where the ocean sea water has more influence. Since clarity is
influenced by the quantity of plankton, it is also an indicator of the stage
of eutrophication.
Figure 3 shows that oxygen saturation exceeded 100% almost every year,
but there has been a decreasing trend since 1970. The Bay mouth area had a
normal percentage of oxygen saturation from 100 to 110 percent, excluding the
oversaturation during the development of the red tide in 1968, but it fluctu-
ated widely both in the middle and deep end of the Bay, indicating that
eutrophication in the Bay has been progressing.
Next, let us look at organic matter. Figure 4 shows the annual change
of COD value after 1963. According to the figure, the value of COD has been
within a range of 1 to 3 ppm in general; about 1 ppm at the Bay mouth and 2
ppm in the middle area. Annual fluctuation has been minimal. However, in
the deep end of the Bay, it has been increasing slightly since 1966.
Figures 5 through 7 show the values of nutrient salts such as NH^-N,
N03-N and P04-P, respectively. From the figures, it is clear that they have
been increasing since 1964, especially N03-N and PO^-P.
By area, the highest value of NH4-N was measured at the deep end of the
Bay with around 0.5 ppm, for N03-N and PO^-P, relatively higher values were
found in the middle of the Bay with 0.2 ppm, and 0.05 ppm, respectively.
While the values of NH4-N showed considerable variation depending on sea
area, neither N03-N nor PO^-p showed such wide variation.
22
-------
UJ
QC
nJ_ J r
•0fif Funobashl
•Off Chiba
-Off Tamagawa River mouth
— \
* ^^^ TL.
V^
i i I
I
i i I i i i i I i i t i I i i i i
1946 50 55 60 65 70 75
CHANGE IN TRANSPARENCY (deep end of the Boy)
Figure 1
LU
o:
CO
£2
T
I I I
•Off Banzunonana
• Off Kawasaki
\
h- Off Kisarazu
I i l I I i i I I I I I I I I I I I I I t I l I
till
I
1946 50 55 60 65 70 75
CHANGE IN TRANSPARENCY (middle of the Bay)
Figure 2
23
-------
140
-------
0,8
^ 0.6
D.
a.
~ 0.4
I
0.2
1963 65 67 69
Figure 5 CHANGE IN NH4-N
71
0.4
I I I I
E
Q.
Q.
~ 0.2
i
ro
O
DEEP END OF THE BAY
MIDDLE OF THE BAY
MOUTH OF THE BAY
I
0.10
Q.
a
a. 0.05
1963 65 67 69 71
Figure 6 CHANGE IN N03-N
T
i i I I I I i
Yr-
J±-
I i
i i i
1963 65 67 69
Figure 7 CHANGE IN P04~P
71
25
-------
PRESENT CONDITION OF THE BOTTOM DEPOSIT
In January, 1976, a survey was made of the general condition of the
bottom deposit in the Bay of Tokyo. The survey was carried out at 11 points
(Figure 8) sediments were collected with a mud sampler (Figure 9). Results
of the survey are discussed in the following sections.
40'
50'
140'
40'
30'
20'
10'
Tamagawa Rl.
Kawasaki] •'•:
^Jfbkohama^j
'Anegasaki
Kannofuaki
• • • * * * *
.* • * • " «
•v- • /.•.:.
•**• * . . . i»ji*
'^f * • >.J^
Bottom Deposit
(January 1976)
Collection of Samples -
for PCB Accumulation
Only Humic Acid
40'
35°
30'
20'
35°
10'
40' 50' 140°
BOTTOM POINTS SURVEYED
Figure 8
26
-------
I
©
Wire; (attached to a crane)
Weight; 17 circular-shaped
metal sheets in the
metal pipe of 2OOmm
-------
CORE SAMPLES
—H
-40,5
No. I
Smell of hydrogen
sulflde (Strong)
No. 2
No. 3
No. 4
No. 5
No. 6
Smell of hydrogen
sulflde (Strong)
-1.5
V 1 V
"«••»,
'*'<
/»ord
shell (small)
smell (weak)
5mm
Smell (Strong)
0,55 0.7Q
S/na// <^ hydrogen
sulflde
0.68
\
O.E;
Smell of hydrogen
sulfide (Strong)
Lugworm
shell (small)
hard
shell (very
small)
hard
0.1
shell (small)
l^^( shell (smalt) I-..H
[•»**i L1* -.1
K>1 t>.%
: .
b » *
•• <
' r 4 '
» 1 »
. k 1
.::-v
^ »
>*., »
i r 4
;::•
> >*
s/ie// (small)
shell (small)
hard
shell (large)
O.I
< "• >
;•••:
* A '
r 4 to
^
* r -»
r v *
* T
v r '
•>k,
:•%'
•V
w «
uv'
«. > v
hard
LUGWORM(1) NO LIVING THING NO LIVING THING SPIDERFISH (2) NO LIVING THING
shell (large)
aqueous rock (yellow
beach smell ochr9)
LUGWORM (1)
oo
r~H ,
0.86
~0m 008
— I
-1.5
Yo.7
!??
:*:»'
•>v,
^ r »
' v«
»« 4 (
::«:
T A
v:
< ••.
»*«.
4 l>k
i» » '
«**.
-:v
r * i
»»«
•',
1
v Smell of hydrogen
\ sulfide
0,68 ^
L 0.60
^ \
0.83(
shell (small)
a
a
a
4o.8
I^^M
> ">
•«• k
^•' 4
„'*
4 <%
V::
','
«»•••
* «.-'
:-v'
vv
1 1 * >
» **
»« >
r
k Shw// of hydrogen
\ sw/f/:
:v;
^
* » ^ ,
*T»
Smell (Strong) i
r °'6v
f
shell(lorge) o/»5
hard
smell of
hydrogen
sulfide (strong)
•;:•
» 4 «
r*« ••
•::•
V-l
»»•»<
« -i »
"4 1
> *4
y0.29
itf
s>i»//rs/ro/v;
0.10
s/>0// (many)
shell (large,
many)
n
v« l
< « J
•v:
» r •
M ^
-v;
< «• ,
;,%;-
^ A t
-v
„-
11 of hydrogen :
sulfiei* — .
0.07 •
4 Lugwormfmany) rr
shell (many) |V
b_
55
/>ord g
H
ii
i>
1 S/LT/ fl/oc*
IsiLTfvery Black-grey
fine)
\1 , .
•ij SILT(clay) Sreen-grey
^ S4/VO Black-grey
Position where the lead
weight of 9kg stopped
(January 1976)
NO LIVING THING NO LIVING THING NO LIVING THING NO LIVING THING LUGWORM (MANY)
Figure 10
-------
40'
50'
140°
I Arakawa River
Sumidagawa.Ri. • •:
Tokyo'. •.>
Tamagawa'RiyefS£\. °-60
Banzuhohana
-Kisarazu
Konriorizaki:j:.
Kurigahama:
•SKohaya. . (January 1976}
"'.'.'• • ' (Unit: m)
40'
35°
30'
20'
35°
10'
Figure 11
DISTRIBUTION OF SILTY MUD
Toxic Substances
In the survey, total mercury, hexivalent chromium, lead, cadmium and
PCBs were measured.
(1) Total Mercury
Figure 12 shows the horizontal distribution of total mercury. The silty
mud from the sea areas (No. 4) off Kawasaki and Yokohama (No. 2) contained
more than 1.0 mg/kg; high density area extends in a tongue shape from the
west side of the Bay towards Anegaskaki.
29
-------
40'
50'
140'
'.'Bahz'unohana
•Karfaya
; (January 1976)
40'
35°
30'
20'
35°
10'
Figure 12 HORIZONTAL DISTRIBUTION OF T-Hg (Sty mud level)
Next, Figure 13 shows the vertical distribution at each survey point.
The surface layer which was 50 cm thick showed a high density of mercury,
particularly in the silty mud.
(2) Hexivalent Chromium
As far the the result of this survey is concerned the density of hexi-
valent chromium was less than the quantitative limit of 1 mg/kg at all test
sites.
(3) Cadmium
In the silty mud, both at the station (No. 10) off Arakawa River mouth
and the stations (No. 4 and No. 5) off Kawasaki, cadmium density was from 2
to 3 mg/kg in the silty mud; at all other points, it was less than 1 mg/kg.
Figure 14 shows the vertical distributions.
30
-------
,0
0.5
1.0
0.5
1.0
Sllty mud_pi
0
05
1.0
2.0
m
No. 2
sm
0
0.5
1.0
2.0
m
1.0
0.5
1.0
NO. 5
05
1.0
2.0
m
F|gure 13 VERTICAL DISTRIBUTION OF TOTAL MERCURY (JAN., 1976)
0 1.0 2.0 3O 4.0 0 ID 2.0 3O 4.0
No. 1
(ppm)
i i
B.m.
0
0.5
1.0
2.0
m
_ 1
-
-
-r
*+ ' ' :
—
—
No. 2
I i i i -
1.0 20 3.0 40
Silty mud_f-«
0
0.5
1.0
2.0
m
0 1.0 2.0 30 4.0
NO. 5
am.
0
0.5
1.0
2.0
m
1.0 2.0 3O 4.0
s.m.
0
0.5
1.0
2.0
m
_l
w I I —
Figure 14VERTICAL DISTRIBUTION OF CADMIUM (JAN., 1976)
31
-------
(4) Lead
There was a highly dense area of more than 50 mg/kg of lead from the
area off the river mouth of the Arakawa River to the area off the Tamagawa
River and Yokohama port. As shown in Figure 15 the vertical distribution of
concentration was almost constant at 15 mg/kg in depths greater than 0.5 m,
excluding the area off the Arakawa and Tamagawa Rivers. Therefore, this
value can be considered as the natural environmental value of lead in Tokyo
Bay.
Silty
mud_
0
05
1.0
2.0
m
20 40 60
20 40 60
No. 1
(ppm)
sjn.
0
0.5
1.0
2.0
m
1 -
No. 2
sm
0
0.5
1.0
20 40 60
I
Sllty mud
-III II
Figure 15 VERTICAL DISTRIBUTION OF LEAD (JAN, 1976}
32
-------
(5) PCB
According to the "Outline of Results of the National Environmental
Survey (Water and Bottom Deposits) 1973, PCB", by the Water Quality Bureau of
the Environment Agency, the PCB density varied from 0.4 to 29.0 mg/kg with an
average of 7.96 mg/kg in the Keihin Yokohama Port. The maximum density of
2.57 mg/kg was detected in the bottom deposits of Tokyo Port. Both of these
highly polluted areas were within Tokyo Bay. However, countermeasures to
remove PCBs are almost completed and the present values of PCB concentration
are from 0.1 to 0.6 mg/kg at Station No. 2 off Yokohama Port and Station No.
1 off Honmoku.
Distribution of total mercury, cadmium, lead and PCBs was discussed
above. Relatively high concentrations of these substances were distributed
into the bay near the mouths of the Arakawa and the Tamagawa Rivers. From
this, it is estimated that toxic substances flow from the rivers into Tokyo
Bay in large quantities. Vertically, the concentration was especially high
in the silty mud at all points except Station 10 off the Arakawa River mouth.
The effect of man-induced pollution was limited to the surface layer of 50
cm.
(6) Oil
According to the Marine Pollution Survey Report (Hydrography Department,
Maritime Safety Agency, November, 1974), the condition of oil pollution in
the bottom deposits of Tokyo Bay was surveyed with saturated hydrocarbon as
an indicator. Oil contains saturated hydrocarbon on the order of several
tens of percents. The density of saturated hydrocarbon in the bottom deposit
was especially high, both in the northwest sea area and the area off Goi, of
Chiba Prefecture. The maximum value was more than 700 mg/kg. The average
density was about 300 mg/kg in Tokyo Bay. Judging from these values and the
speed of accumulation, it has been estimated that the total quantity of oil
(as saturated hydrocarbon), which is artificially discharged, amounts to 1.2
x 101* m tons. According to the survey, the normal hexane extraction method
of analysis found an oil density of 3530 mg/kg in the area off Arakawa River
mouth and less than 1000 mg/kg in other areas.
Organic Substances and Nutrient Salts
The results of the survey are shown below.
(1) Percentage of Mud
The percentage of mud contained was 32.4% on the average in the silty
mud and 21% in the central points No. 5, 7, 8 and 9. There was a tendency
for the percentage to be smaller in the middle than in the coastal region.
This tendency was found in other layers, too. Since the areas with low
percentages of mud correlated with areas containing thick sludge, it may be
inferred that particulates have been settling in the middle of the Bay due to
low water velocity.
33
-------
(2) Ignition Loss
The silty mud showed a rate of more than 10% ignition loss (IL) in all
the areas, excluding the deep end coastal region in front of Funabashi Port
and off Arakawa River mouth. A maximum of 16.1% IL was observed in the
middle of the Bay at Station No. 5. In the area off Haneda, a high rate of
15.6% IL was observed and the general region of high values (over 13% IL)
extended from the area off Haneda to the middle of the Bay (Figure 16).
(3) COD
The area with densities over 30 mg/g extended in a circular pattern from
the middle of the Bay off Haneda. The horizontal distribution of COD in the
silty mud tended to be similar to that of ignition loss and percentage mud,
but a distinctive difference was observed in that its vertical distribution
rapidly decreased from the silty mud layer to the 0 m level. This was especi-
ally noticeable in the middle of the Bay (Figure 17).
(4) Sulfide
An extremely high concentration of 3.73 mg/g was detected at point No. 8
off Haneda and the area with concentrations greater than 1.0 mg/g extended
from the west part of Tokyo Bay to Anegasaki. The sulfide distribution was
similar to that of the abiotic zone. Vertical distribution showed a drastic
decrease from the silty mud layer to the 0 m level and there was no variation
in density in the layers below 0 m at all stations except Station 10. At the
points off Arakawa River mouth and Tamagawa River mouth, a concentration of
over 0.2 mg/g in the 0 m layer was detected, which was considered to have an
effect on living things (Figure 18).
(5) Total Organic Carbon
The area extending from Yokohama to Chiba and Tokyo Port showed TOC
densities of over 10 mg/g. In the middle of the Bay (Station 5) a rich
organic content of 15.2 mg/g was noticed.
(6) Total Nitrogen
In the silty mud layer, a density of over 2000 mg/kg was observed in the
area extending west from Tokyo Bay to Anegasaki. Especially at Station No.
1 off Honmoku the value for N was over 4,000 mg/kg, and the area of high
density extended from the middle to the deep end of the Bay (Figure 19). A
similar distribution was observed in the 0 m layer.
(7) Total Phosphorous
The rivers exert a considerable influence in the case of phosphorus, and
therefore a high density is observed at river mouths. In the silty mud
layer, a density of over 600 mg/kg was observed in the area extending from
Tokyo Port to the mouth of Tamagawa River. The area where values were
greater than 500 mg/kg was similar to that of nitrogen. In the 0 m layer,
the circular area extending from the mouth of Arakawa River to that of the
34
-------
40'
50'
I40C
40'
50'
140*
to
en
e
Sumidagawa R,.. . . v
Ahegosaki
Haneda'. :$
Tamagawa fii. :%
(Percentage)
(January 1976)
40'
35°
30'
20'
35°
10'
Tawaga'waRi.:\
Kawasaki. '-:\£M
40'
dried mud)
{January 1976)
VERTICAL DISTRIBUTION OF IGNITION LOSS
Figure 16 (Silty mud layer)
HORIZONTAL DISTRIBUTION OF COD
Figure i? (Silty mud layer)
35°
30'
20'
35*
-------
40'
50'
I40e
CO
(ft
I Arakawa
Sumidagawa R/.'/ :
Tokyo
• Funabashi
-Kawasaki:'..•£
Yokohama-^.
(mg/g dried mud)
(January 1976)
I
40'
35°
30'
20'
35°
10'
4&
I Ardkawa
Tokyo •
50'
140°
• I' Funabashi
Haneda
Tamagawa Pi.-. •:
Kawasaki.'.
(mg/g dried mud)
(January 1976)
I
HORIZONTAL DISTRIBUTION OF SULFIDE
Figure is (Silty mud layer 1
HORIZONTAL DISTRIBUTION OF T-N
Figure 19 (Silty mud layer)
40'
35°
30'
20'
35°
10'
-------
Tamagawa River showed concentrations of over 500 mg/kg. This area contained
a large amount of nutrient salts and was considered a eutrophic area (Figure
20).
(8) BOD
High BOD densities were observed at Station No. 9 in both the silty mud
layer and the 0 m layer. The values were 74.4 mg/g and 65 mg/g, respectively
The gradient from No. 8 off Haneda showed progressive organic pollution of
the bottom deposits. A concentration of over 30 mg/g was widely distributed
in the silty mud layer, even in the middle of the Bay, except for the areas
off Funabashi and Yokohama Port which showed a relatively low density of less
than 20 mg/g (Figure 21). In the area on the west side of the Bay to the
north of Honmokuhana, and in the middle of the Bay, the bottom deposit was
polluted considerably by organic matter.
ACTUAL CONDITION OF ORGANIC POLLUTION IN TOKYO BAY AS INDICATED
BY BIOLOGICAL INDEX
In the preceding section, the pollution distribution was shown in terms
of actual conditions of the water quality and bottom sediments. In this
section pollution is given as determined by the AGP (Algal Growth Potential)
survey. This survey evaluates the potential capacity of the water in the Bay
to grow algae and also used the growth of benthos as an indicator of organic
pollution in bottom deposits.
Present Condition of AGP
In December 1975, surface water was collected at 14 points in the Bay
(Figure 22). Skeletonema costatum, a common Bay algae, was used in the test.
Figures 23 and 24 show that the algae tended to enter directly into the
logarithmic growth period without passing through a latent period. Growth
stopped after 4 to 5 days and the population began declining after 6 days in
all the samples except K (Kanagawa) 4, and the control (off Arasaki Miura
Peninsula). In the cases of K-4 and the control, a short latent period and
less active growth were observed in the second day after the start of cultiva-
tion due to (it appears) a smaller quantity of P and N in the samples. In
the cases of K-4, K-15, T (Tokyo)-8 and the control, the decline after the
peak was relatively rapid.
Comparison of AGP values by sea area is shown in Table 2 and Figure 25.
The Tokyo seas area showed the highest value of from 9.43 x 105 to 1.18 x 106
cells/ml, followed by 1.83 x 105 to 8.70 x 105 cells/ml in the Kanagawa sea
area and 2.39 x 105 to 4.89 x 105 cells/ml in the Chiba sea area. As seen in
Figure 26, the distribution of AGP resembles those of N and P.
The value of T-N showed considerable changes for samples from K-7, T-23
and C-3 before and after the test and, at the remaining stations, from 50 to
60 percent of the nitrogen was consumed.
37
-------
40'
50
140
00
00
Haneda
Tamagowa R
Kawasaki.: .'•
"Kannonzaki:''-^
(ppm/ dried mud)
(January 1976)
40'
35°
30'
20'
35°
10'
40* so;
I ArakawaAjv*
Sumldogawq;Ri..- •.
~~ Tokyo
Shlnagawd
140'
•» *
'.Antg'asakl
Haneda'
Tamagawa Rj
Kawasaki' '
''Banzuriohdna '
sKlsdra'zu
-40'
35°
30'
20'
( mg/g dried mud)
( January 1976 )
35°
10'
HORIZONTAL DISTRIBUTION OF T-P
Figure 20 (Sllty mud layer)
HORIZONTAL DISTRIBUTION OF BOD
Figure 21 (Sllty mud layer)
-------
; Tokyo-.:-.^
.T-zl
Kawasaki'. '$
Yokohama
lAhegasaki
'••Kisarozu
?•Futtsu
WATER SAMPLING POINTS FOR AGP TEST
Figure 22
39
-------
10'
6
10
AGP
jo5
o
10
I03
(cells/ml)
DAYS OF CULTIVATION
i i I i
0
Figure 23
10'
6
10
AGP
5
10
3
10
8 Day
i I T
(cells/ml)
-8 -
DAYS OF CULTIVATION
1 I I I I I
8 Day
PRODUCTION CURVE OF SKELETONEMA COSTATUM
-------
io7
AGP
1 I I T
(cells/ml)
-15
DAYS OF CULTIVATION
I I I I I i
io7
T I T
(cells/ml)
itf
AGP
IO5
DAYS OF CULTIVATION
I I I I I
10
4 6 8 Day 0 2 4 6
PRODUCTION CURVE OF SKELETON EM A COSTATUM
8 Day
-------
TABLE 2. COMPARISON Of KWIMJV QUANTITY OF PRODUCTION BY AREA
ST. t-14 K-10 k-~ K-4 K-l "-23 T-2 T-B C-2 C-3 C-9 C-'.5 C-18 :-22 Control
Jtexii
Quantity of 1.B3 5.60 6.84 ^.49 8.70 1.06 9.43 1.18 4.89 3.59 3.58 4.61 3.?5 2.39
Production xlO5 xlO5 xlO5 xlO5 xlD- xlO6 xlO5 x!0? xlO5 xlO5 >1C- xlO5 xKE >1C-
1* 2.0 6.2 7.6 5.0 9.6 11.7 10.4 13.1 5.4 4.0 4.0 5.1 4.4 2.6 1.0
2* 1.0 3.1 3.7 2.5 4.8 5.8 5.1 6.^ 2.' 2.0 2.0 2.5 2.2 1.2
-& ZZZZZIIIZIIII^^III^II^IIIIIIII^ZZIIZI^IZI^IZIZIIIIIIIIIIIIIII^
ro
*1 Shows the ratio of the maximum quantity of production at the point to the control.
*2 Shows the ratio of the maximum quantity of production at the point to K-14.
-------
I I05_
CONTROL
Figure 25
MAXIMUM QUANTITY OF PRODUCTION OF SKELETONEMA COSTATUM BY AREA
43
-------
ppm
I I I I I I I 1 I I I I I I
I I I I I I I I
P04-P
FIRST (Befbretest)
O......Q SECOND (After test)
i i i i iii LI
ANALYSIS OF WATER SAMPLE FOR AGP TEST
Figure 26 44
-------
In the case of P, especially P04-P, the values generally decreased to
0.004 to 0.009 mg/kg after testing. This shows that Skeletonema costatum
does not proliferate greatly once the density of P04-P declines to this
level, in spite of the abundance of other nutrients. In other words, POU-P
is significant as a limiting factor of AGP in Tokyo Bay.
From the above results, it was found that:
(1) AGP clearly indicates the water quality of each area, even in the
Bay of Tokyo where pollution has progressed considerably, and is an effective
indicator of eutrophication;
(2) Enrichment of the sea water has been progressing from Tokyo to the
Kanagawa and Chiba sea areas in Tokyo Bay; and
(3) Phosphorus is a factor which limits growth of algae in Tokyo Bay.
Benthos
Because benthos has a strong tendency to live in a fixed area on the sea
floor it is used as an indicator to show the general degree of pollution.
Figure 27 shows the changes in species composition of the benthos with
enrichment. In non-polluted areas the benthic species composition tends to
be diverse: it becomes less diverse as pollution increases. Also, as pollu-
tion increases, the ratio of the total population to the number of species
(benthic index) increases because only specific kinds can survive and ultim-
ately no benthic organisms can survive.
Therefore, the most simple standard for judging whether or not the
bottom sediment is polluted is if living things are able to survive there.
Figure 28 shows the abiotic areas among 11 points surveyed. The distribution
is similar to that of sulfide with 1.0 mg/g (dry wt.). Judging from these
two indices, it can by seen that both the coastal region and the area extend-
ing from the west side to north of the sea area in front of Anegasaki (exclud-
ing the area near to Funabashi Port) are considerably polluted.
ORIGIN OF SLUDGE AND ACCUMULATION RATE OF SLUDGE IN TOKYO BAY
Origin of Sludge
To find out the origin of organic pollution, humic acid, pheophytine and
C/N ratio in the bottom were studied. Results are shown in Figures 29 through
31. Solid organic substances which settle in the bottom mud may be classified
into two groups according to their origin. The first group includes marine
organic substances such as dead organisms and metabolized substances from
phytoplankton. The second group includes organic substances which originate
on land. Generally speaking, the value of P for humic acid in the bottom
deposits is higher near the mouth of the river where the inflowing river
water exerts its influence and smaller at the mouth of the bay where the
influence of sea water dominates and insea areas where detritus from phyto-
plankton accumulates.
45
-------
DEPOSITS
POLLUTED WATER
NUMBER OF MOLLUSCS (PERCENT)
NUMBER OF POLYCHAETS (PERCENT)
POPULATION/NUMBER OF SPECIES
POPULATION
NUMBER OF SPECIES
CHANGE IN FACIES OF BENTHOS DUE TO POLLUTION AND CLASSIFICATION
OF POLLUTION (By Kitamori)
Figure 27
FUNABASHI
TOKYO
KAWASAKI
YOKOHAMA
r^
HONMOKU
KISARAZU
ANEGASAKI
Area with no
living things
Point with no
living things
DISTRIBUTION OF BENTHOS (JANUARY 1976)
Figure 28
46
-------
40'
50'
140*
I .Arakawg. River* ^jfe^
. Tokyo '. '.':$
Haneda •'
TamagaWa'f^i'-
. Kawasaki •'.'..':&
Yokohat
0.603
"•^Anegasaki
r.Bdrizunohana
i-'Kisarazu
(January 1976)
I
40'
35°
30'
20'
35°
fO1
HORIZONTAL DISTRIBUTION OF HUMIC ACID
Figure 29 (Om level)
According to Figure 29, stations 1 and D (close to the mouth of the Bay)
showed small values of 0.084 and 0.050, respectively, and Stations 2 and C
showed 0.120 and 0.110, respectively. This indicates that the sea water
exerts a significant influence at the mouth of the Bay and a considerable
part of the humic acid in the bottom deposit is sea-oriented humic acid. On
the other hand, Station 4 at the mouth of Tamagawa River, Station 3 off the
47
-------
I40C
I . Arakawa
__ SumidagawaRi.^
Tokyo • •;
Tamagawd Ri.£
Kawasaki:•',-':^G^
.•Jchihara
•JAnegdsaki
anzunohana .
* i » *
;:kisarazu
(ma/a? Floating mud)
(January 1976)
40'
50'
140°
Haneda .\
Tamagawa Ri
Kawasaki.' ••'
40'
35°
30'
20'
35°
10'
(January 1976)
HORIZONTAL DISTRIBUTION OF PHEOPHYTINE HORIZONTAL DISTRIBUTION OF C/N
Figure 30 (0 171 level ) Figure 31 (Om level )
-------
mouth, Station 10 off the mouth of Arakawa River and Station 11 off the mouth
of Edogawa River showed large values from 0.512 to 0.962, indicating that the
influence of the river water was very strong; a considerable part of the
humic acid in the bottom deposit was land-oriented humic acid. Although
small values from 0.05 to 0.160 were observed at Stations 5, 7 and B in the
middle of the Bay, it was due, it seems, to decayed substances produced from
the large amount of dead phytoplankton accumulated on the bottom.
Pheophytine is produced by decomposition of chlorophyll in phytoplankton
and it has been reported that it is strongly related to the value of P for
humic acid. In other words, the value of P for humic acid is small in the
layer containing a large amount of pheophytine and large in the layer contain-
ing a small amount of pheophytine. This tendency was corroborated in this
survey. The horizontal distribution map of Figure 30 shows values greater
than 100 mg/m3 for the area from the west side of the Bay to the deep end.
The maximum value was found in the middle of the Bay, indicating a large
amount of deposits mainly from phytoplankton.
There is a tendency for the ratio of organic carbon to nitrogen (C/N) to
increase as accumulated organic substances decompose, and thus this ratio can
be used as an indicator of the degree of decomposition of organic substances
in the bottom deposits. Figure 31 shows that the degree of decomposition was
small (less than 7.0) in the region north of the line connecting Haneda and
Anegasaki, in the middle of the Bay (Station 3), and off the Bay off Honmoku
(Station 1). The C/N ratio was large in the region extending across the Bay
from Yokohama and Kawasaki to Banzunohana with values above 8.0; the maximum
value of 9.5 was in the middle of the Bay, indicating that the decomposition
there had progressed to a large extent.
The above findings show that: (1) The organic sludge in the area off
the mouth of the Tamagawa River and the Arakawa River originated from organic
substances from the land, and (2) the organic sludge in the middle of the Bay
was produced from marine phytoplankton which settled on the bottom.
PCB Accumulation Rate
In this survey PCB was considered as an index and the PCB accumulation
rate was measured both at Station 1 off Honmoku and Station 2 off Yokohama
Port. The amount of PCB use increased every year from its beginning in 1954
to its peak in 1970. This pattern also is followed in the Kanto district.
Therefore, the bottom layer with a uniform amount of PCB was considered to be
a layer formed in 1954. Assuming that the sludge accumulation rate was
either 1 or 2 cm/year, two different correlations were made to find the
relationship between the amount of PCB used and the amount of PCB deposited
in each sediment layer. Table 3 shows the results.
From the correlation coefficients shown in Table 3, it is considered
that the accumulation rate was approximately 1 cm/year at Station 1 off
Honmoku and approximately 2 cm/year at Station 2 off Yokohama Port. The
values are close to those shown by Aizawa (1).
49
-------
TABLE 3. CORRELATION BETWEEN PRODUCTION OF PCB AND QUANTITY OF PCB IN THE
SEDIMENT
Accumulation Measured
Speed Station Point
1 cm/year No.
No.
2 cm/year No.
No.
1
2
1
2
Regression
Line
y =
y =
y =
y =
56
6
22
6
.4x
.3x
.4x
.4x
1.
+ 2.
- 0.
+ 1.
5
9
5
2
Correlation
Coefficient
Y = 0.
Y = 0.
Y = 0.
Y = 0.
7
1
6
7
EFFECT OF BOTTOM DEPOSITS ON WATER QUALITY
Organic matter deposited on the bottom is decomposed by bacteria. Below
the surface deposits there is a limited supply of oxygen and decomposition is
done by anaerobic bacteria. Anaerobic decomposition is slower in comparison
to the aerobic decomposition in the water column and produces substances
which impede bacterial action, further slowing down the speed of decomposition
and making the bottom a storage reservoir of organic substances.
Bottom deposits are also a source of nitrogen and phosphorous. These
nutrients return to the water and are used in the production of phytoplankton.
This can cause a cyclical problem of increased phytoplankton production,
which causes increased organic accumulation, the BOD/COD of which creates the
anaerobic condition of bottom sediments, which causes release of nutrients,
and so on.
This survey measured the quantity of TOC (total organic carbon), T-N
(total nitrogen) and T-P (total phosphorus) released from the silty mud
layer, the 0 m layer and the 2 m layer under both aerobic and anaerobic
conditions. The study took place over a period of 60 days at 11 points in
Tokyo Bay. Figure 32 shows the device used in the experiments. Oxygen gas
(02) was used for the experiment under aerobic conditions and nitrogen gas
(N2) was used for the experiment under anaerobic conditions. Under aerobic
conditions the concentration of T-N changed considerably at the 2 m level.
T-P showed almost no change in any layer, but TOC varied considerably.
Figures 33a and b show the results of the experiments for Stations 4, 5 and 6.
Under anaerobic conditions both T-N and T-P increased in concentration
as time passed, and T-N increased in concentration particularly at the 2 m
level. TOC did not show much variation under aerobic conditions.
The amounts of nutrients released from the bottom deposits were obtained
by considering the slope of the line tangent to the release curve at the
point where positive values were obtained (see Examples 1 and 2).
50
-------
10cm,,
N2 and 02 Gases
I
(0.2 Kg/cm)
DEVICE FOR NUTRIENT RELEASE MEASUREMENT
Figure 32
Artificial
Water
Mud
-------
(ppm)
6
T-N
1.0
I I I I I
I I I 1 I I
1.0
I i I I II
11 I 1 II
2
2 2
1,0
6 6
1.0
I I I I I I
I I I I I I
TOC
I III
6 61-
2-
20 40 60Doy 0 20 40 60Day 0 20 40 60 Day
Figure 33a. Oxygen Saturation (100%)
52
-------
(ppm)
TOC ( 2 m)
T-N
T-P ^X*l 1.876
SILTY MUD
I I I I I I
I I I I I I
III
I I I I I
I I I I I I
I I I I I
TOC
Na4
No. 5
- 6
._ No.6
20 40 60Day 0 20 40 60Day 0
Figure 33b. Oxygen Saturation (0%) 53
20 40 60 Day
-------
Density
(ppm)
Density
(ppm)
0
0 Day
EXAMPLE 1
0 Day
EXAMPLE 2
Quantity of TOC Released
Under both anaerobic and aerobic conditions, there were large fluctua-
tions in the release of TOC. It appears this was primarily due to the effect
of biological decomposition and coagulation. The organic matter originally
exists as a solid in the bottom mud. As it is decomposed by microorganisms
some of it becomes soluble and is dissolved in the upper water. The organic
matter released is decomposed and coagulated by microorganisms, and some of
it is vaporized into the air. In order to find out the precise quantity of
TOC released, it will be necessary to control decomposition, settlement and
condensation by bacteria.
Quantity of Nutrient Salts (T-N, T-P) Released
Decrease in concentration of T-N was observed under aerobic conditions
both in the flocculent layer and the 0 m layer. This was probably due to
biological coagulation settlement and denitrification. Thus the observed
decline is due to a mixture of release coagulation and denitrification. In
order to find out the true quantity of T-N released further study is required.
However, an estimate of the quantity of T-N released is given in Table 4.
Average values from this table show aerobic conditions yielded 5.0 mg/m2/day,
5.4 mg/m2/day and 9.3 mg/m2/day from the silty mud, 0 m layer and 2 m layer,
respectively, and anaerobic conditions yielded 7.0 mg/m2/day, 5.9 mg/m2/day
and 7.6 mg/m2/day, respectively. There is not much difference in quantities
released under anaerobic and aerobic conditions.
In the middle of the Bay, T-N release was over 5 mg/m2/day and the
maximum value was 23.6 mg/m2/day at Station No. 4 off the Tamagawa River
mouth. The total quantity of T-N released in the Bay was estimated to be
approximately 7.0 metric tons/day, assuming that the average quantity was 7.0
mg/m2/day and the area of the Bay was about 1000 km2. This may be converted
into COD by the equation:
COD =
19.7
1.78
x an x gn x N,
where:
an = Conversion rate (0.230) obtained from water quality analysis of the
public water area in 1974.
54
-------
gn = distribution ratio of plankton in the productive water area (1.0 in the
sea water area).
CODN - YJg x 0.230 x 1 x 7.0 * 18 (metric tons/day)
The actual value should be larger because the effect of coagulation,
settlement and denitrification was included in the result and disturbance of
the silty mud was not taken into consideration.
TABLE 4. QUANTITY OF T-N RELEASED
(mg/m2/day)
^^-4^
Condition
•^^^.^^^
st/Nor-^^^
i
2
3
^
5
6
7
8
9
10
11
average
Si
aerobic
«-fc^.
0.338
0.860
1.026
16.390
3.089
2.733
5.918
18.225
4.555
2.096
0.140
5.034
Ity Mud
anaerobic
3.518
3.737
2.675
23.599
1.051
5.701
6.975
11.019
4.841
8.503
5.642
7.024
aerobic
2.255
4.755
0.541
22.690
5.803
7.147
5.039
3.007
5.287
0.508
2.448
5.407
0 m
anaerobic
4.809
6.338
2.930
11.274
9.336
1.210
8.312
7.484
5.000
8.408
0.191
5.936
aerobic
17.027
10.810
7.631
4.771
18.817
3.928
11.912
8.504
12.816
4.090
2.484
9.345
2 m
anaerobic
6.274
5.988
8.918
8.281
13.696
3.376
6.784
8.886
12.453
4.245
5.196
7.645
Quantity of T-P Released
As shown in Figures 33a and b, the concentration of T-P was almost
constant under aerobic conditions with very little release. About ten times
as much was released under anaerobic conditions as under aerobic conditions.
55
-------
Table 5 shows the quantity of T-P released. It was calculated in the
same way as T-N. This table shows that under aerobic conditions the average
quantity was 0.117 mg/m2/day, 0.092 mg/m2/day and 0.032 mg/m2/day from the
silty mud, 0 m layer and 2 m layer, respectively, and under anaerobic condi-
tions, 0.919 mg/m2/day, 0.502 mg/m2/day and 0.627 mg/m2/day were released,
indicating a great variation between aerobic and anaerobic conditions.
TABLE 5. QUANTITY OF T-P RELEASED
(mg/m2/day)
"" — -Layer
Condition
StTllor-^^^
1
2
3
4
5
6
7
8
9
10
11
average
Sil
aerobic
0.061
0.185
0.185
0.070
0.025
0.217
0.306
0.166
0.142
0.191
0.047
0.117
ty Mud
anaerobic
0.153
1.344
0.287
1.096
1.675
1.191
1.108
0.433
0.701
, 1.834
0.287
0.919
aerobic
0.042
0.000
0.081
0.312
0.006
0.032
0.248
0.045
0.000
0.250
0.000
0.092
0 m
anaerobic
0.191
0.541
0.605
0.720
0.790
0.032
0.287
0.433
0.389
1.147
0.382
0.502
aerobic
0.064
0.127
0.032
0.000
0.000
0.000
0.000
0.064
0.032
0.068
0.008
0.036
2 m
anaerobic
0.612
0.822
0.548
0.718
0.867
0.034
0.331
1.013
0.656
1.236
0.057
0.627
The total quantity of T-P released in the Bay was estimated to be
approximately 0.92 metric tons/day. This figure is based on the assumption
that the average quantity was 0.92 mg/m2/day and the area of the Bay was
approximately 1000 km2- This may be converted into COD using the equation:
143
CODp .= YJQ x ap x ep x P
ap = 0.585
56
-------
n s- x 0.585 x 1 x 0.92 « 43 (metric tons/day)
r I . /o
The average value of both CODN and COD is given as
COD., 0
- N_ - P_ = __ a 31 (metric tons/day)
This is the total quantity of the nutrient salts released.
Oxygen Consumption
Dissolved oxygen in the water is consumed by both organic matter in the
water and bottom mud. Thus, the oxygen demand is great. This is particularly
true in summer when the sea water is stratified and lack of oxygen becomes
very serious in the bottom layer.
Dissolved oxygen consumption was determined in this study using a mud
layer of 10 cm thickness in order to correctly represent the oxygen absorption
rate in the field as shown in the report by Fair (2). Table 6 shows the
results.
TABLE 6. RESULTS OF OXYGEN CONSUMPTION TEST
(02 g/m2/day)
Silty Mud 0 m 2 m
Oxygen
^Saturation 100% 50% 100% 50% 100% 50%
St. NoT
1
2
3
4
5
6
7
8
9
10
11
average
1.044
0.594
2.499
2.262
1.542
0.621
0.192
0.885
1.173
1.305
0.594
1.156
0.912
0.594
1.377
1.656
1.350
0.516
0.552
1.902
0.684
0.867
0.375
0.980
0.639
0.498
0.051
1.200
0.735
1.218
0.402
0.329
0.561
2.235
0.366
0.749
0.717
0.903
0.096
1.779
1.377
1.287
0.465
0.876
0.849
1.437
0.726
0.956
2.792
0.697
0.147
0.648
0.306
1.296
0.675
2.103
4.650
0.867
1.824
1.455
1.095
1.095
0.252
2.244
0.789
0.402
0.840
1.323
3.000
0.945
1.455
1.222
Figure 34 shows the distribution of silty mud (50%). The quantity of
oxygen consumption was 1.0 g 02/m2/day in the flocculent layer with an oxygen
saturation of 50% in the area extending from the middle of the Bay to the west
coast of the Bay. The maximum value was 1.9 g 02/m2/day measured at Station
No. 8 off Haneda.
57
-------
40'
50'
140'
Sumidagawa: Ri.'/ .;• • '•,
Tokyo].;
Harieda'.
Tamagawa Riytfi
Yokohama'-'-'.'-.iis
(SILTY MUD)
• Kanaya
r\:: • ' ' (02 g/mz/day)
' • . ' (Set at 50%)
40'
35°
30'
20
35°
10'
HORIZONTAL DISTRIBUTION OF OXYGEN
Figure 34 CONSUMPTION RATE
The total consumption of oxygen in the Bay was estimated to be approxi-
mately 1000 metric tons/day or 600 metric tons/day in terms of COD (TOD: COD
= 1.78:1) based on the assumption that the average oxygen consumption was 1.0
g 02/m2/day and the area of the Bay was approximately 1000 km2.
58
-------
Judging from the above result it is estimated that the silty muds consume
600 metric tons 02/day which is equivalent to 80% of that necessary to satisfy
the oxygen demand (741 metric tons/day) of materials flowing into the bay from
the land on a daily basis. In spite of the fact that the silty mud contained
more organic matter in comparison to other layers, it consumed a similar
quantity of oxygen to that consumed by other layers. This indicates that the
best method for determining oxygen consumption has not yet been established
and the cause and mechanism of oxygen consumption by sludge must be determined.
SUMMARY
Eutrophication is considerable in Tokyo Bay and is caused by the large
quantity of organic matter produced endogenously in the Bay as well as an
equivalent amount flowing into it from the surrounding land. The sludge
accumulates in the middle of the Bay. It is estimated that the quantity of
accumulated sludge is approximately 400 million metric tons. This lowers the
water quality by release of nutrient salts and consumption of oxygen.
Moreover, the area devoid of life has been expanding.
The oxygen consumption experiment did not show a clear difference
between the silty mud layer and the bottom layer (2 m layer), but it is
estimated that the bottom mud consumes about 80% of the oxygen necessary to
decompose all the organic substances flowing into the Bay from the land.
Since the sludge consumes a large quantity of oxygen, when an overlying
sludge is formed the bottom layer becomes anaerobic.
The experiment on nutrient release from the bottom muds determined that
almost no phosphorus is released under aerobic conditions, but the quantity
of phosphorus released increases in proportion to the quantity of phosphorus
in the sediments when they are subjected to anaerobic conditions. It is
therefore estimated that phosphorus equivalent to 10% of that amount flowing
from the land into the Bay is released from the bottom mud at the time of
formation of the sludge layer. Moreover, the AGP survey showed that the
effect on the water quality of the sludge is considerable because phosphorus
is the nutrient which limits phytoplankton productivity in Tokyo Bay.
It is expected that by removing the accumulated sludge the environment
can be improved through the cycle as shown in Figure 35. If the silty mud
layer is removed COD will be less than 30 mg/g and sulfide less than 0.3 mg/g
(up to the 0.5 m layer at Station 4 and up to 1 m layer at Station 10) to
make the bottom mud either clay or silt. Here the water quality should be
taken into consideration. According to Yoshida's table (3) which classifies
sea area by nutrient level and bottom characteristic, a polluted water area
can become a more desirable enriched water area where benthos and crustaceans
may increase in kind and number.
Finally, problems which need work are listed below.
(1) Mechanisms of bottom pollution
More work is required on dispersal of organic sludge and on oxygen
consumption rates. It will be necessary to research suspended solids and the
dispersion of bottom mud.
59
-------
Figure 35. Flow Chart for Purification of Bottom Deposits in Tokyo Bay
Reestablishment
of a Viable
Living
Community
For fishing
Increase of
benthos
Increase of
zooplankton
Decrease of
phytoplankton
Decrease of area
devoid of life
(Migration of fishes ... saurel, gray
mullet, sprat)
(Bivalves ... short necked clam, ark
shell, flatfish, young sea bass,
giant clam)
(crustaceans)
(decrease of red tide)
(multiplication of sludgeworms)
1
Reduction of Water Pollution (decrease of COD, TOC, Ns and
Ps and increase of DO)
Prevention of Red Tide (decrease of secondary pollutants)
Prevention of Concentration of Biota
Facilitation of Decomposition of Detritus, Prevention of
Nutrient Release, Stabilization of Toxic Substances
Decrease of Area with Poor Oxygen
(Removal of Organic Detritus) (Removal of Nutrient Salts)
(Removal of Harmful Substances)
Removal of Accumulated Sludge
60
-------
(2) Effect of sludge
The general effect of bottom mud and water quality on the ecosystem was
determined. To define this in more detail it is necessary to find out 1) the
effect on eutrophication (in the form of AGP) of nutrients contained in the
mud, 2) the effect of bottom sediments on living organisms through bioassay
and 3) oxygen consumption of mud and sludge to be removed.
(3) Technology of pollution abatement
Dredge reclamation, treatment at the original place and ocean dumping of
dredged materials should be comprehensively evaluated from the standpoints of
environment, technology and economics. It is also necessary to develop a
technology to facilitate settling of dredged materials at the dredge and dump
sites.
(4) Effect of bottom purification
It is necessary to quantitatively determine the effect of improving
water quality via bottom purification by using a model in which the cycling
of substances and the exchange of sea water are taken into consideration. At
the same time the model should account for the effect of bottom purification
on the recovery of the ecosystem.
REFERENCES
1) Takako Aizawa, "Vertical Distribution of Cadmium, Total Mercury and PCB
in the Bottom of Tokyo Bay," Bottom Pollution Improvement Countermeasure
Survey Research Paper, 1974.
2) G. M. Fair, "Water Supply and Waste Water Disposal."
3) Yohichi Yoshida, et a!., "Change in Production of Living Things in the
Lower Production Stage," Eutrophication and Cultivation of Marine Pro-
ducts in the Water Area, April, 1973, Japanese Fishery Society, Koseisha-
Koseikaku.
61
-------
AN EXPERIMENT IN REMOVAL OF ORGANICALLY POLLUTED
BOTTOM MUD FROM THE SETO INLAND SEA
Akio Murakami*
Nansei Regional Fisheries
Research Laboratory
Fisheries Agency
ABSTRACT
Since the 1950's organic pollution of bottom mud
in the Seto Inland Sea has been observed near the pulp
mill wastewater drain. By the 1970's the polluted
area had expanded (Figure 3). The Fisheries Agency
examined this problem from August to October in 1974
(Figures 1,2, Tables 1,2). According to the Agency,
concentrated areas of polluted mud were observed in
Osaka Bay, the eastern part of Hiuchi Nada, Hiroshima
Bay, Beppu Bay and some other areas (Figures 4-9,
Tables 3, 4). The upper 20 to 30 cm of the bottom mud
was heavily polluted. The volume of organically
polluted bottom mud (COD >40 mg/g) is 106 m3 in the
Seto Inland Sea, 85% of which exists in Hiroshima Bay
(Figures 10, 11, Table 5).
The red tide in the Seto Inland Sea became harmful
in the 1960's and this is related to bottom pollution.
Eutrophication in inshore waters contributes to the
outbreak of the red tide, and the organically polluted
bottom mud contributes to the eutrophication. Since
1973, the Fisheries Agency has been removing the
polluted mud to reduce the eutrophication.
In this project the organically polluted bottom
mud is dredged using a variable volume volute pump to
prevent the diffusion of mud. The dredged mud is
transferred to the treatment pontoon by a suction
pipe. Then the mud is treated through the processes
of coagulation, sedimentation and dehydration. Activ-
ated charcoal is used to filter the decant water which
is then discharged to the sea. The settled sludge is
hardened with cement and then dumped in a reserved
land area (Figure 13).
*7782-9 Maruishi, Ohno-cho, Saeki-gun, Hiroshima-ken 739-04, Japan
62
-------
There are still some problems to be solved in our
experiment. Work needs to be done on the method of
removing newly deposited materials from the surface of
polluted bottom muds.
INTRODUCTION
The increase of organic pollution of bottom mud in the Seto Inland Sea
has spread from stagnant regions, where it has been exacerbated by the lack
of dissolved oxygen at the bottom layer and eutrbphication due to nutrients
released from the sediment. The marine ecosystem has been severely damaged.
This paper discusses the mechanism and the influence of organic pollution of
bottom mud, reports on the organic pollution of the bottom mud in the Seto
Inland Sea in 1974, and describes the Fisheries Agency project for abating
this pollution by removal of the bottom mud.
MECHANISM AND INFLUENCE OF ORGANIC POLLUTION OF BOTTOM MUD
Solid organic materials which end up in bottom sediments are produced
both in the sea and discharged from the land. Once discharged pollutants
have grown beyond the capability of the sea to process them, the sea water
becomes polluted. This occurs first in the neighborhood of the drainage
outfalls when solid organic materials in the waste waters (or detritus pro-
duced in the sea) settle to the bottom near the outfall. Bottom mud pollution
lags behind water pollution, and is restricted to a more narrow area. Water
pollution is ephemeral, while a history of sediment pollution is recorded
continually by layers of deposited material. The area polluted is dependent
on the quantity of pollutant and the prevailing currents. In the case of
bottom mud pollution, particulate materials sink mostly at the center of eddy
currents or in stagnant regions. The particle size of sediment in such
regions is very small, and the surface layer is covered with fine silt common-
ly called "Hedoro" in Japan.
In summer a thermocline is developed because the current is generally
slow in inshore waters except at the mouth of the bay and in the strait. At
that time the surface water is not mixed with bottom water and occasionally
the temperature difference between the two is 10°C or more in July and August.
In autumn, the thermocline disappears due to the cooling of the surface water
and mixing of the two layers occurs. Moreover, they may suddenly be mixed in
shallow waters by strong winds such as a typhoon. In such cases, silt at the
sediment-water interface is mixed into the overlying water and may transfer
to another stagnant region where it settles again. Therefore, polluted
bottom mud often is found far from the drainage outfalls where the contamina-
tion originates. In the Seto Inland Sea the polluted sediments in the central
part of Harima Nada, the eastern part of Hiuchi Nada, and the southern part
of Suho Nada have resulted from such processes.
Organic pollution in the bottom mud acts as a secondary source of water
pollution. Although nitrogen and phosphorus do not affect eutrophication as
long as they are combined with the mud, when released by bacterial or chemical
action they can be transferred into bottom water and from there move through
mixing into the upper waters where they contribute to eutrophic conditions.
63
-------
Particulate organic nitrogen (PON) and participate organic phosphorus
(POP) are mineralized both in suspension and in sediments. The amount of
particulate organic materials existing in the bottom and the surface sediments
is related to the degree of eutrophication of the marine environment. The
bottom mud polluted by the waste water from pulp mills generally does not
contain many nutrients, but it consumes dissolved oxygen in sea water as it
is oxidized. This results in a lack of dissolved oxygen in bottom waters
(especially in the summer thermocline stage), and many benthic organisms are
killed. Since the organic compounds (vitamins, etc.) and heavy metals (iron
and manganese, etc.) stimulate the growth of flagellates, an important count-
ermeasure against the red tide is to prevent the release of such substances
from the bottom mud.
STATUS OF SEDIMENT ORGANIC POLLUTION IN THE SETO INLAND SEA
The Seto Inland Sea is the largest inshore body of water in Japan. It
is about 400 km in length and 21,827 km2 in area and its average depth is
37.3 m. Depth in the straits is more than 100 m. There are about 800 islands
and many bays, Nadas and straits. Two branches of the Kuroshio current enter
this area via Bingo and Kii channel, and the Tsushima current also enters via
the Shimonoseki strait. Many rivers flow into this area. Consequently, the
water in the Seto Inland Sea is slowly transferred from west to east and
there are many stagnant regions in it. Thus the exchange of water with the
ocean is very poor. Marine pollution has been observed since the 1950's, and
became serious around 1973 or 1974. Due to the regulation of pollution loads
by the "Seto Inland Sea Conservation Law" in 1973 the situation is improving.
The Fisheries Agency currently is studying sediment pollution in the
inshore waters of Japan. They carried out research in the Seto Inland Sea
from September to October, 1974 and in Ise and Mikawa Bay, Hibiki Nada and
Hakata Bay from August to September, 1975 and also in Omura Bay and Ofunato
Bay in July, 1976 (1). The volume of polluted bottom mud has been estimated
from the results. The investigations were carried out by the Fuyo Ocean
Development, Co. at 160 stations in the Seto Inland Sea and another 924
stations in 28 heavily populated areas. The sampling and analyzing methods
are shown in Tables 1 and 2. Mud samples were collected with the core sampler
shown in Figure 1 and frozen until the analytical work was performed. The
echo sounder investigation was carried out at 160 stations with a Som'cator
Model RS-72. Two ultrasonic frequencies (400 kHz and 30 kHz) were used and
the thickness of the mud-water layer was determined from the difference of
the return time between the 400 kHz and 30 kHz waves. The sea regions in the
Seto Inland Sea and the stations are shown in Figure 2.
Many local sediment studies relating to fisheries impacts have been
carried out in the Seto Inland Sea. But the investigations carried out
by our laboratory (2) in December 1970, August 1971, October 1972 and May
1973 were the first time the inland sea had been investigated in entirety.
Sediment from the upper 3 cm layer was collected with an Ekman-Birge
dredge at 100 stations and analyzed for COD, Ignition Loss (IL)* and total-S.
ash-free dry weight
64
-------
TABLE 1. STANDARDIZED SAMPLING PROCEDURE FOR BOTTOM MUD
0%
en
Sampling
Method
Ekman-Birge
Smith-Mclntyre
Core Sampler
Item of COD
Anal%fcnc _____
Sampling length
of Mud (cm)
<10
10-20
<20
20-35
35-50
>50
Water Cont.
Layer of Mud for Analysis (cm)
0-15 15-20 30 - 35
X
X
x
X X
XXX
XXX
XXX
5 Between Bottom
and 35 cm Layer 5 from Bottom
— —
X
X
X
X
X X
X X
IL Total-S. P.
N. Silt Comp.
-------
TABLE 2. METHOD OF ANALYSIS OF BOTTOM MUD
Items
Methods
Items
Methods
Size
Composition
en
Screen ca. 50 g mud with
water by 32 and 150 mesh
sieves, dry the residue
at 110°C, weigh after
cooling.
(division of bottom mud)
Coarse Sand not pass
Gravel
Sand
Mud
through 32
mesh
(dia. <0.5 mm)
not pass through
150 mesh
(dia. 0.125-
0.5 mm)
pass through
150 mesh
(dia. <0.125 mm)
COD
IL
Total-S
P
alkaline potassium permanganate,
idometric titration
700°C 2 hrs.
detection tube
Strickland and Parson's
"A Practical Handbook of
Seawater Analysis" (1968)
CN - Corder
-------
IL was determined by burning the mud at 800°C until constant weight was
achieved. Total-S content was determined using the following method: The
mud was steam distilled and hydrogen sulfide from it was absorbed by a
solution of zinc-acetate titrated with 1/100 N iodine. Results showed that
the degree of bottom mud pollution changes seasonally--it increases during
summer and autumn, and decreases during winter and spring. The maximum
values of COD, IL and total-S are often found in autumn. The distribution of
COD, IL and total-S for October, 1972 is shown in Figure 3. It is obvious
that the mud is seriously polluted in Osaka Bay, the northern coast of Harima
Nada, Hiuchi Nada, Hiroshima Bay, the southern area of Suho Nada and in Beppu
Bay. The higher values (e.g., COD 30 mg/g, IL 14%, total-S 0.5 mg/g) are
also observed at the central part of Harima Nada, Bingo Nada, Hiroshima Bay
and the mouth of Beppu Bay during summer and autumn. COD and IL values do
not exhibit the seasonal variation similar to the total-S values. Although
the regions where total-S content exceeds 0.5 mg/g are observed everywhere
during summer and autumn, the values decrease below 0.2 mg/g in spring at
almost all stations. The nearest station to the coast is 2 or 3 km offshore,
but there are regions of about 35 mg/g COD and 1.0 mg/g total-S offshore of
Kure.Bay and the central part of Osaka Bay. The area of heavily polluted
sediment offshore had already increased by the time of the survey.
TOTAL LENGTH! 3m
SAMPLING LENGTH! 2ro
DIAMETER! 60mm
WIRE
WEIGHT
'STOPPER
VINYL CHLORIDE TUBE
O METAL VALVE
Figure 1. Core sampler.
67
-------
133'
34J
00
BINGO NADA-.:.•.: • -J^.
3:*
133'
Figure 2. Sampling stations of bottom mud in the Seto Inland Sea. Aug-Oct 1974.
-------
COIJ
Figure 3. Bottom mud qualities (COD, Total-S, Ignition Loss)
in the Seto Inland Sea, October 1972.
The 1974 investigation was carried out from September to October during
the season when pollution is most severe. More than 1,000 stations from 2-
300 m off the coast were examined. Nutrient values as well as the usual
measurements were determined. The results are shown in Figures 4-9. The
maximum, minimum and average values of measurements in several regions are
shown in Table 3. As shown in these figures and the table there are many
heavily polluted regions. Although these are the same regions as in former
research projects, the maximum values of COD, IL and total-S have increased.
High nitrogen and phosphorus contents (3.0 mg/g and 1.5 mg/g, respectively)
are presumed to be due to interstitial water containing dissolved inorganic
nitrogen (DIN) and dissolved inorganic phosphorus (DIP). According to Ukita
et al., (3). the mud columns collected off Iwakuni, Mitajiri, Tokuyama and
Ube, are black at the surface, but gradually fade with depth. Generally,
nitrogen and phosphorus in the upper 5 cm layer are respectively 2 to 3 times
and 1.5 to 2 times greater than those below the 20 cm layer. Nitrogen and
phosphorus contents are especially high in Mitaziri Bay which is polluted by
69
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TABLE 3. QUALITY OF BOTTOM MATERIALS FROM SEVERAL SEA REGIONS IN THE SETO INLAND SEA, AUG.-OCT., 1974
^x. Sea Region
ItemN. Suho Hiroshima
x. Nada Bay
COD
(mg/g)
IL
(*)
Total-
S (mg/g)
P (mg/g)
N (mg/g)
Composition
of Mud
(*)
Max.
Av.
Min.
Max.
Av.
Min.
Max.
Av.
Min.
Max.
Av.
Min.
Max.
Av.
Min.
Max.
Av.
Min.
26.2
14.3
4.3
16.5
11.0
3.1
1.0
0.3
0.01
1.1
0.6
0.2
2.5
1.6
0.4
100.0
75.9
10.3
40.7
23.5
12.8
17.8
12.8
9.2
0.6
0.2
0.04
0.9
0.7
0.6
2.8
2.3
2.0
99.4
97.6
94.2
lyo
Nada
7.8
4.2
1.3
12.8
8.5
4.7
0.1
0.0
0.01
1.2
0.6
0.4
1.2
0.7
0.3
77.5
38.3
1.1
Bingo
Nada
23.2
10.3
2.5
14.8
11.0
8.4
0.9
0.4
0.1
0.9
0.7
0.5
2.5
1.9
1.4
99.7
97.2
86.2
Hiuchi
Nada
20.3
8.3
2.0
13.8
10.7
6.8
0.4
0.2
0.04
0.9
0.6
0.4
2.3
1.7
0.9
99.9
94.8
63.2
Bisan
Strait
12.9
7.8
2.4
12.0
8.6
2.7
0.8
0.3
0.01
0.9
0.5
0.2
1.9
. 1.3
0.3
95.7
61.3
12.0
Harima
Nada
23.1
12.1
1.2
13.8
9.6
2.6
1.2
0.3
0.01
0.9
0.6
0.2
2.5
1.7
0.4
99.5
81.6
3.7
Osaka
Bay
21.8
6.6
1.3
14.0
10.0
3.5
1.3
0.5
0.01
0.9
0.5
0.2
2.8
1.2
0.4
99.0
53.1
9.8
Kii
Suido
•12.9
10.0
6.4
8.4
6.8
3.6
0.3
0.1
0.02
0.8
0.7
0.7
1.3
1.1
0.6
99.2
93.3
77.1
Inner
Beppu Bay
39.6
18.1
2.3
18.8
14.2
1.8
1.4
0.3
0.02
1.5
0.9
0.5
3.0
2.2
0.4
99.9
91.8
14.5
-------
131'
132'
133'
35
34'
331
13?'
133'
Figure 4. COD (mg/g) value of the bottom mud in the upper 5 cm layer in the Seto Inland Sea, Aug-Oct 1974.
-------
131"
13?'
'3-'
34'
ro
33
33
31"
133'
I3S'
Figure 5. Ignition Loss (%) value of the bottom mud in the upper 5 cm layer in the Seto Inland Sea,
Aug-Oct 1974.
-------
132'
133
135
Figure 6. Total-S (mg/g) content of the bottom mud In the upper 5 cm layer in the Seto Inland Sea,
Aug-Oct 1974.
-------
I3C
13?'
!33'
134'
135'
34"
33'
33
(33
133'
13;'
Ffgure 7. P (mg/g) content of the bottom mud in the upper 5 cm layer in the Seto Inland Sea, Aug-Oct 1974.
-------
131'
13;'
13:
34'
33'
KYUSHU
I3J-
(.IT
Figure 8. N (mg/g) content of the bottom mud in the upper 5 cm layer in the Seto Inland Sea, Aug-Oct 1974,
-------
1 3V
34'
•vj
(T>
33*
•^^^^^^^ ' - ' '•
->^^t^
13?
Figure 9. Composition (%) of silt (dia 125 \i) of the bottom mud in the upper 5 cm layer in the Seto Inland
Sea, Aug-Oct 1974.
-------
waste water from breweries. They are respectively 15 mg/g and 2-3 mg/g in
the upper 20 cm of the mud column. The N/P ratio is 6 or 7. Generally the
black surface layer is richer in nutrients than the greenish-gray deeper
layer. Nitrogen is 2-3 mg/g, phosphorus is about 1 mg/g, and the N/P ratio
is 3-10 in the surface layer. The N/P ratio is about 2.5 in the lower layer.
Although nitrogen and phosphorus contents were not determined for the lower
layer in the investigation in 1974 it usually has a nitrogen content of 1-2
mg/g and a phosphorus content of 0.5-1 mg/g.
The highest N/P (3.3) values were observed in Osaka Bay and Hiroshima
Bay. Nitrogen content was 2.8 mg/g in both regions. On the contrary, the
lower N/P ratios (1.1 and 1.6) were obtained in lyo Nada and Kii channel
respectively, and the nitrogen content was 1.2 mg/g in lyo Nada and 1.3 mg/g
in Kii channel.
In 28 regions the coastal areas were more polluted than the offshore
areas. As shown in Table 4 the heavily polluted areas were off Otake and
Iwakuni in Hiroshima Bay, Hiro Bay in Aki Nada, the inner part of Beppu Bay,
off Mishima and Kawanoe in Hiuchi Nada and off Sakai in Osaka Bay. The major
pollution sources are paper mill waste water in Hiro Bay, off Otake and
Iwakuni and off Mishima and Kawanoe, and brewery waste water off Hofu, sewage
off Sakai, and sewage and ironwork and oil refinery waste waters at the inner
part of Beppu Bay. The characteristics of the sediment pollution are related
to the kind of pollutant. For example, in the area polluted by the paper
mill outfall COD and IL values are high. Brewery waste water causes high
nitrogen content but low values of COD and total-S. Total-S and nutrient
values are high in the area polluted by sewage.
Until 1973 about 30,000 kl of human waste were discharged per day in the
Seto Inland Sea; 740 kl were released in the central part of Osaka Bay and
620 kl in Hiroshima Bay. Sewage released off Otake and Iwakuni in Hiroshima
Bay caused high concentrations of nitrogen and phosphorus in this region.
The distribution of COD in the upper 5 cm of the sediments at 71 stations off
Iwakuni is shown in Figure 10. In Otake, 105 tons per day of paper mill
waste water are released. In Iwakuni, 3 x 105 tons per day of paper mill
waste water are released. Refineries, the petrochemical industry, the rayon
factory and the airport waste water are other important sources of pollutants
in these areas. Until the 1970's, untreated pulp mill waste water was dis-
charged to the sea causing a brown colored bubbling water mass along the
coast. Near the outfall, COD of the bottom mud was about 40 mg/g and remained
over 30 mg/g as far as 3-4 km from the coast. The environmental water quality
standard for fisheries (4) sets the desirable COD of the bottom mud at less
than 20 mg/g. Sediments which met this quality were observed only around
Atada Island as far as 4-5 km from the coast. The bottom mud off Iwakuni and
Otake has been seriously polluted since the 1950's. In October 1951 COD was
40-56 mg/g off the coast between the Oze and Imazu Rivers.
The vertical distribution of COD varies throughout the Inland Sea. At
the station having over 30 mg/g in COD in the upper 5 cm of bottom mud, the
value is usually over 20 mg/g in the upper 30 cm. There is a station (Iwakuni
St. 5) where COD is 31.8 mg/g in the upper 5 cm, 33.0 mg/g in the 15-20 cm
layer, 21.3 mg/g in the 30-35 cm layer, 21.8 mg/g in the 81-86 cm layer, and
77
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TABLE 4. QUALITY OF BOTTOM MATERIALS IN SPECIAL SELECTED SEA REGIONS IN THE SETO INLAND SEA,
AUG. - SEPT., 1974
Item
Sea Region
Hiro Bay off Otake off Iwakuni off Hofu
off Mishima
and Kawanoe
off Sakai
COD
(mg/g)
IL
/ o/ \
V fO i
Total -S
(mg/g)
P (mg/g)
N (mg/g)
Composition
of Mud
(*)
Max.
Av.
Min.
Max.
Av.
Min.
Max.
Av.
Min.
Max.
Av.
Min.
Max.
Av.
Min.
Max.
Av.
Min.
55.7
18.5
10.1
13.2
10.2
8.2
1.2
0.2
0.02
0.8
0.6
0.4
2.5
1.8
1.4
99.6
89.8
34.6
51.4
27.6
12.6
27.8
14.1
7.5
0.7
0.2
0.03
0.8
0.7
0.4
3.5
2.5
1.4
99.1
94.3
34.4
47.1
26.4
15.9
16.4
13.0
10.7
1.6
0.4
0.07
1.0
0.7
0.3
2.9
2.2
1.8
99.9
96.2
72.9
16.5
9.7
3.3
19.6
7.3
2.2
0.3
0.1
0.01
0.8
0.5
0.2
3.9
1.3
0.3
99.4
63.0
2.5
46.8
16.5
5.9
19.1
11.4
3.5
1.2
0.2
0.01
1.0
0.7
0.4
2.8
1.7
0.6
100.0
86.2
3.3
23.7
15.7
7.6
14.4
11.4
7.9
2.1
1.0
0.2
1.1
0.7
0.4
2.7
2.1
1.4
100.0
99.5
96.0
-------
mg/g in the 130-150 cm layer of the mud column. Off Kawanoe and Mishima the
maximum COD is 46.8 mg/g in the upper 5 cm layer. This is due to paper mill
waste water which is as great as that in the Iwakuni and Otake district.
Tuz'u'3
10km
Figure 10. COD (mg/g) value of the bottom mud at upper 5 cm layer off Otake
and Iwakuni, 23-25 August 1974.
79
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COD in the upper layer of the bottom mud is not very different in the
two sea regions, but the layer of high COD in the sediment is restricted only
to the thin surface layer off Mishima and Kawanoe. The distribution of
polluted mud (COD over 20 mg/g) is not available in the deep layers over 25
cm in that region.
The pollution distribution is summarized as follows: the region off
Otake and Iwakuni is located in the western part of Hiroshima Bay where water
exchange is limited by the offshore current. The area off Mishima and Kawanoe
is located at the eastern part of Hiuchi Nada and is not closed by the off-
shore current. Thus, the polluted mud is spread all over the eastern part of
Hiuchi Nada. Paper mill waste water, 105 ton per day, is discharged into the
inner part of Hiro Bay. In this region the area of polluted mud is restricted
to a narrow area near the outfall. Distribution of high COD value stations
is limited to a circle having the center at the point of the pollution source.
Values over 30 mg/g lie as far away as 1 km from the drainage, and values of
20 mg/g are found as far away as 2 km. Vertically, COD is over 20 mg/g in
the upper 50 cm of the bottom mud, and 30 mg/g in the upper 25 cm. Hiro Bay
is narrow but has a wide mouth opening to Aki Nada. The exchange of water in
and out of this bay is rather uniform, so the mass of colored waste water
occasionally extends to the outer part of the bay. Under these circumstances
the pulp fiber in the waste water does not settle thickly on the bottom. The
horizontal and vertical distributions of the polluted bottom mud are ruled by
the currents and topography of the sea floor.
The amount of polluted sediment was estimated as follows: COD in each
25 cm layer of the mud column was obtained at each station from the vertical
distribution of COD using values for grain composition and echo sounder
results. Stations with a bottom consisting of sand or rock were excluded.
The area was divided into several blocks by grouping mud-bottom stations.
The volume of each sediment layer in every block was obtained by multiplying
the area by the thickness (up to 25 cm). A cumulative curve of the polluted
sediment layer was drawn for each region examined (as shown in Figure 11) for
the upper 25 cm layer in Hiroshima Bay. These curves are calculated with the
percentage of the mud volume in every layer as vertical axis, and the average
COD in each block as the horizontal axis. From this graph the volume of the
polluted mud in each COD range can be estimated by multiplying the total
volume of the mud by the percentage given in the cumulative curve. The
amount of the polluted sediment estimated by COD at each region in the Seto
Inland Sea is shown in Table 5. The volume of polluted sediment over 30 mg/g
of COD is about 8 x 106 m3 in the Seto Inland Sea, 92% of which is in Hirosh-
ima Bay. For 40 mg/g there is a volume of 106 m3 and 85% of it is found in
Hiroshima Bay. Although pollution is slight in Aki Nada and lyo Nada because
of the relatively strong currents, a polluted bottom exists at Hiro Bay in
Aki Nada and the inner part of Beppu Bay in lyo Nada. This is shown in Table
5.
According to research done in August, 1975, the volumes of the polluted
sediments in the bays of Ise and Mikawa which contain over 30 mg/g and 40
mg/g of COD are respectively 488 x 105 m3 and 71 x 105 m3- Although the area
of Ise and Mikawa Bay is a tenth of the Seto Inland Sea, seven times the
volume of polluted mud exists in Ise and Mikawa Bay. This is probably due to
80
-------
30 20
COD (mg/g)
10
Figure 11. Cumulative curve of polluted sediment in the upper 25 cm layer in
Hiroshima Bay, August 1974.
81
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the difference in water exchange. According to the Environment Agency, the
pollution load of COD was 1,600 tons per day in the Seto Inland Sea in 1972,
and 600 tons per day in Ise and Mikawa Bay in 1973.
TABLE 5. VOLUME OF POLLUTED BOTTOM MUD IN SEVERAL SEA REGIONS IN THE
SETO INLAND SEA, AUG. - OCT., 1974. X 104 M3
COD mg/g
Sea Region
Osaka Bay
Kii Suido
Harima Nada
Bisan Strait
Bingo Nada
Hiuchi Nada
Aki Nada
Hiroshima Bay
Beppu Bay
lyo Nada
Suho Nada
Total
Area (km2)
1,529
1,554
3,462
916
954
954
963
946
3,974
3,100
18,316
15
5,523.1
21.3
1,964.5
61.9
1,400.1
878.1
608.5
75,737.0
4,076.5
17,633.2
107,904.2
20
1,211.2
—
589.6
—
464.4
119.8
58.3
22,115.1
363.5
794.0
25,715.9
30
4.5
—
7.1
—
—
14.4
26.5
725.6
12.3
—
790.4
40
_._
—
—
—
—
6.4
8.8
87.0
—
—
102.2
50
— _ «P
—
—
—
—
—
4.1
0.7
—
—
4.8
EXPERIMENTAL DREDGING OF ORGANIC POLLUTED SEDIMENT IN THE FISHING GROUNDS
Red tide broke out frequently in the Seto Inland Sea in the mid 70's, as
shown in Figure 12. Recently, the red tide has been noted about 300 times a
year in the Seto Inland Sea. The kind of red tide plankton has changed from
diatoms to flagellates. To put it succinctly, the red tide in the Seto
Inland Sea is becoming worse. Particularly the red tide caused by Hornellia
(Chloromonadophyceae) is a large-scale outbreak during the warm season from
July to September, and damage to cultured yellowtail (fish) is severe. The
number of cases of red tide harmful to fisheries (shown in Figure 12) is not
correlated with the scale of the damage. For example, in the summer of 1972
Hornellia red tide in Harima Nada and the western part of Kii Suido, produced
a record breaking kill of cultured yellowtails valued at about 2 million U.S.
dollars. It is clear that the deleterious effects of the red tide in the
Seto Inland Sea owes much to eutrophication of inshore waters. Since 1973,
the Fisheries Agency has been removing the polluted mud to reduce eutrophica-
tion in order to avoid fisheries damage.
The experiment was carried out as a joint venture of "World Ocean System
Co." and "Fuyo Ocean Development Co." Dredging was done at Yura in Awaji
Island in 1973, at Sagoshi Bay in Ako city in 1974, and at Aboshi Bay in
Himeji city in 1975. In 1976 it will be carried out at le Island in Harima
Nada. In this project the organically polluted sediment in the yellowtail
rearing areas and off the river mouth is dredged to prevent diffusion of mud.
The dredged mud is transferred to sedimentation pontoons, 600 m away, by a
82
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suction pipe on the sea surface. Then the mud is treated through the proces-
ses of coagulation, sedimentation and dehydration. The separated water is
filtered, then discharged to sea. The settled sludge is hardened, then
dumped on a reserved land area. The flow sheet of the experiment carried out
for Aboshi Bay is shown in Figure 13. The bottom mud off the mouth of the
Ibo river is black in color, smells of hydrogen sulfide, has 34-85 mg/g of
COD and contains much sulfide and chromium.
I i i i i
RED TIDE
FISHERIES DAMAGE
300
200
100
0
40
30
20
10
0
1967 70 75
Figure 12. Frequency of red tide and
fisheries damage in the
Seto Inland Sea, 1967-1975
The bottom sediment dredge is equipped with a suction mouth which has
movable wings and a variable volume (0-1500 m3/hr) volute pump which dredges
the polluted bottom mud at a speed of 1900 m3 of slurry per hour. The mud to
be dredged is 50-60 cm thick, 5700 m2 in area and 2-2.5 m under the sea
surface. The sediment is 30% in its average concentration of mud and has a
D60 of 11 y. The dredged mud is about 3100 m3 in volume. Two sedimentation
pontoons of 600 m3 volume are used, one for sedimentation and the other for
discharging the sludge. The volume of the sludge is 30 to 50% of the dredged
mixture. Often the screen is clogged with deposited vinyl sheets or grass,
so the volume and the mud concentration of the supernatant varies. The
treatment pontoon has a capacity of 50 m3 per hour. Alum and polymer are
poured into the supernatant as a coagulant, the proper pH is regulated with
sulfuric acid and sodium hydroxide, then sodium hypochloride is used for
denitrification. The raw water is treated with polymer which settles out
(dehydrater). Finally, the supernatant is treated with activated charcoal to
remove the residual chlorine and the water is discharged to the sea after
confirming its non-toxicity to marine organisms with a bioassay using minnows,
The effluent water quality standard is described as follows: "SS <20 mg/1,
COD <20 mg/1, NH4-N <1 mg/1, free chlorine <0.05 mg/1, H2S <1 mg/1, pH <9"
and the heavy metals and harmful substances are discharged in concentrations
less than the quality standard as given in the Water Pollution Control Law.
The settled sludge in the sedimentation pontoon and the dehydrated cake from
the dehydrater are mixed with cement, then dumped on the reclaimed land and
the surface covered with sand.
83
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**-
CO
Figure 13. Flow sheet of withdrawal and treatment of polluted bottom mud.
-------
(Fig. 13)
1 dredge (180 m3/h)
2 pipe on sea surface
3 screen
4 storage barge
5 treatment pontoon
6 coagulation tank
7 sludge collector
8 concentration tank
9 thickener (140 m3)
10 super-high rate pelletizing and sedimentation unit (pbs type)
11 separated water
12 back washing wastewater tank
13 chlorinated reaction tank
14 filter
15 activated carbon adsorption
16 back washing blower
17 effluent
18 sulfuric acid storage tank
19 sodium hypochloride storage tank
20 sodium hydroxide storage tank
21 polymer dissolving tank
22 P.B.S. polymer dissolving tank
23 aluminum sulfate storage tank
24 sea water pump
25 polymer dissolving tank
26 sludge mixing trough
27 dehydrater
28 sulfuric acid storage tank
29 separated water tank
30 belt conveyor
31 barge (390 m3)
32 discharging wharf
33 clamshell bucket
34 hopper
35 cement silo
36 mixing car
85
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Essentially this experiment is aimed at removing an organically polluted
sediment without affecting the sea or increasing the red tide. Therefore,
the effect on the surrounding sea and the red tide is estimated during the
experiment. As a result there was no direct effect due to the experiment
except the increase of NH^-N concentration in sea water.
An experiment with red tide plankton culture was carried out to determine
the effects of the effluent on the outbreak of the red tide. Cultures of
Hornellia and Olithodiscus were added with sea water to the filtered effluent.
They were kept for two weeks under the following conditions: water tempera-
ture, 20-30°C; illumination, 4,000 Lux for 12 hours per day. Neither culture
increased in growth rate as a result. On the contrary, the growth rate was
inhibited, and sometimes the Hornellia culture (and also minnows used to
monitor the harmlessness of the effluent) were killed, probably due to the
high concentration of NHU-N and the residual chlorine and chloramine in the
effluent.
On this project it was most difficult to determine how to deal with
newly deposited materials on the surface of polluted mud. As mentioned
above, the eutrophied bottom sediment acts as a secondary source of nitrogen
and phosphorus for the bottom water. These nutrients are mainly released
from the upper 15 or 20 cm of the sediment. But the suspended detritus in
sea water is a more important secondary source. It settles gradually and
concentrates in the water layer 1 or 2 cm above the bottom sediment, finally
settling out as newly deposited material. So generally, in many polluted
areas, there is a newly deposited material of a different color, several mm
in thickness, which contains concentrated detritus from the water layer and
is in contact with the bottom surface. It is the same situation as the case
of fiber waste from pulp mills. In this project the mud was dredged by a
dredging pump to prevent the diffusion of mud, but this is not always applic-
able to the newly deposited materials or the concentrated detritus. It is
important to examine this problem, especially in the case of bottom sediment
polluted by pulp fiber.
When selecting an area to dredge it is necessary to understand the
impacts on fisheries and the significance of the mud in polluting the environ-
ment. When the project is carried out commercially, the balance between the
scale of damages and the cost of removal and treatment must be examined.
But, it is more important that the removal must be decided reasonably in view
of the pollution mechanism. Once the dredging is decided upon, the quality,
the range, the thickness of the mud and the time to remove it must be examined
through research on the distribution of bottom mud and detritus.
Parameters indicating the amount of pollution such as COD, IL, N, P,
total-S and size composition of mud must be given. Moreover, toxicity, heavy
metals and oil pollution may also be necessary parameters depending upon the
circumstances. These parameters must be measured vertically and horizontally
in as much detail as possible, not only on the mud but on the surface deposits
and the detritus, along with the rate of release. Insoluble nitrogen and
phosphorus in the bottom mud do not accelerate eutrophication of the sea
water, but once these nutrients change into the soluble state due to bacterial
action or the lowering of pH in sea water, they are added to the bottom layer
86
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sea water through diffusion from the interstitial water in the bottom muds.
Moreover, nitrogen and phosphorus also are released directly from the newly
deposited materials and suspended detritus. These processes are very impor-
tant in eutrophication of inshore waters. But, unfortunately, we have no
effective method to sample the detritus, the new deposits and the interstitial
water in mud, so it will be necessary to develop methods in the future. When
the measurements are carried out in water which lacks dissolved oxygen, it is
desirable to measure DO content continuously in time and space using a DO
meter.
After bottom mud and the bottom water conditions are determined, then
critical values for each parameter of the polluted mud must be determined to
decide if removal is necessary. The desirable qualities of bottom sediment
in fisheries grounds are given in environmental water quality standards such
as "COD below 20 mg/g, total-S below 0.2 mg/g, the concentration of the n-
hexene soluble matter less than 1% and no harmful substances in soluble
state."(4) It is a matter of record that the qualities of bottom mud in the
stagnant region of the Seto Inland Sea are much worse than those in the
standard. Therefore, these values in the standard cannot be adopted as a
lower limit of quality for removing bottom mud. In this experiment 30 mg/g
of COD are decided as one of the criteria for removing organic polluted mud.
But, according to the results presented from the economical point of view,
the criteria might be considered "40 mg/g in COD, 15-20% in IL, 1 mg/g in
total-S, 1 mg/g in total-P, 2-3 mg/g of total-N."
As mentioned above, the minimum quality of the polluted mud removed
should be decided case by case from the view point of the pollution mechanism
rather than the cost. The thickness of the mud to be removed may be 20 to 30
cm in general. The distribution of the polluted mud must be estimated ver-
tically and horizontally by test bores in many stations and by investigation
with an echo sounder. In conclusion, it is necessary to quickly establish
standards for removing mud in order to carry out this project.
The project of removing polluted sediment should be completed with esti-
mates of the improvement of the fisheries environments. This method has not
been discussed yet in our research, but would be desirable to estimate the
effects not only on improvement of the environment and reduction of the
fisheries damage, but in technical problems such as the efficiency of removal.
CONCLUSIONS
In marine pollution, the surface water turbidity or colored waste water
are directly recognized as problems. But toxicity and heavy metal contamina-
tion of the fisheries catch or bottom mud pollution cannot be as easily
detected. They can be recognized the first time by a red tide or a polluted
catch and the fish kills. For bottom sediment pollution in particular there
are few directly obvious results. It is very difficult to carry out the
research itself because the pollution and its damage occur at the bottom of
the sea. But in the Seto Inland Sea the damages are becoming comparable to
other pollution sources. Thus, bottom mud pollution and its means of influ-
ence are gradually becoming understood. Dredging bottom mud is now being
recognized as an important countermeasure to marine pollution. However, the
•
87
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dredging and reclamation are frequently carried out in inshore waters, so the
polluted bottom mud cannot be disregarded as a secondary source to add to the
pollution load of the sea. It is natural that the regulation of the reclama-
tion and the pollution load is a basic countermeasure to marine and bottom
mud pollution. But in the polluted inshore waters such as the Seto Inland
Sea, it is also important to remove the pollution load in the form of bottom
mud. The progress of research on the polluted sediment is desirable princi-
pally for the protection of the marine environment.
REFERENCES (all in Japanese)
1) Report of the Basic Reseach on Improvement and Recovery in Fisheries
Ground. (1974, 1975). Fisheries Agency, '75, '76.
2) Report of the Circulation of the Pollution Load in Ecosystem and the
Index Species for the Pollution. (1973). Tokai and Nansei Reg. Fish.
Res. Labs., Fish. Coll., '74.
3) M. Ukita, et al. On Some Problems in the Estimation of Released Nitrogen
and Phosphorus from the Bottom Mud. J. Water and Waste, 17-10, 11, '75.
4) Water Quality Standard for Fisheries. Japan Fisheries Resources Conser-
vation Assoc., '72.
5) T. Nitta, et al. Study on Pollution by Industrial Sewage. Bull. Naikai
Reg. Fish. Res. Lab. 3, '53.
6) Report of the Realization Project of Preventing and Removing the Red
Tide. (1974, 1975). Japan Fisheries Resources Conservation Assoc.,
'75,. '76.
-------
THE MECHANISM OF METHYLMERCURY ACCUMULATION IN FISH
* ** *
M. Fujiki, R. Hi rota, and S. Yamaguchi
ABSTRACT
The factors contributing to methylmercury accumu-
lation in the red sea bream (Chrysophrys major) were
investigated by using sea water containing methyl-
mercury, bottom sediment from Minamata Bay (methyl -
mercury: 0.015 mg/kg [dry wt.], total mercury: 192
mg/kg [dry wt.]), and bait containing methyl mercury.
The contaminated sea water contained 0.5 yg/liter of
methylmercury and fish placed in this water accumulated
methylmercury in the body, going from a concentration
of 0.012 yg/g (muscle tissue) to 0.033 yg/g (muscle
tissue). The fish fed on methylmercury bait (0.133
yg/g) accumulated a little methylmercury; the methyl -
mercury concentration in the fish increased from 0.012
yg/g (muscle tissue) to 0.020 yg/g (muscle tissue).
Fish raised in a rearing tank containing bottom sediment
from Minamata Bay did not show an effective accumulation
of methylmercury; and methylmercury accumulation was
almost the same as that of the control group.
INTRODUCTION
When Minamata disease was first recognized among inhabitants in the
vicinity of Minamata Bay, the fish from Minamata Bay contained a high concen-
tration of methylmercury. Since the discharge of waste water containing
methylmercury from the factory was stopped, the methyl mercury concentration
in fish from Minamata Bay has gradually decreased. The methylmercury concen-
tration in the fish from Minamata Bay has consequently reached about 0.4
mg/kg (wet weight). The concentration is not always lower than that in fish
from the control area.
However, the mercury concentration in the bottom sediment of Minamata
Bay is still very high. For example, the inorganic mercury concentration in
the bottom sediment near Myojin-misaki is about 600 mg/kg (wet weight). It
has been well known that methylmercury, formed from inorganic mercury, accumu-
lates in fish more easily than does inorganic mercury. This is why extensive
water pollution control is necessary in Minamata Bay.
~*Department of Environmental Epidemiology, Institute of Community Medicine,
the University of Tsukuba, Ibaraki, Japan
** Aitsu Marine Biological Station, Kumamoto University, Kumamoto, Japan
89
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The mechanism of accumulation of methyl mercury by fish is not completely
known. However, it has been generally considered that methylmercury is taken
up by the fish through the gills directly from sea water, from the digestive
organs via food, or from the gills and/or digestive organs via bottom sedi-
ments. The following experiments were conducted to determine which of these
speculations are correct and the degree to which each mechanism contributes
to the problem.
EXPERIMENTAL METHOD
The red sea breams (Chrysophrys major) used in these experiments were
obtained from a fish farm. Body length and weight of the fish is shown in
Table 1. Two hundred of the red sea breams were divided into 4 groups, A to
D, each group containing 50 fish. The red sea breams were acclimated to the
conditions of the fish rearing tank (Figures 1 and 2) for 3 days before the
experimental procedures.
Experiment A
Sea water containing methylmercury (0.5 jjg/liter) was added to the fish
rearing tank (1000 1) and aerated by an agitating pump. Then the sea breams
were reared in the tank for 10 days. The sea water containing methylmercury
was replaced each day. Ten of the sea breams were taken out of the tank
every 2 days and the methylmercury in the fish was measured by gas chromatog-
raphy.
Figure 1. Experimental apparatus for
Experiment A, B, and D.
a: fish rearing tank (1000 1)
b: agitating pump
c: net
90
-------
TABLE 1. THE MEAN OF THE BODY LENGTH AND WEIGHT OF THE RED SEA BREAM
Experimental Rearing
Group Time
A Mean
S.D.
B Mean
S.D.
C Mean
S.D.
D Mean
S.D.
0
1.
12.2
1.3
12.2
1.3
12.2
1.3
12.2
1.3
w.
42.6
12.4
42.6
12.4
42.6
12.4
42.6
12.4
2
1.
10.7
1.4
11.3
1.2
11.8
1.8
11.1
1.2
w.
33.7
11.1
39.4
9.5
40.5
14.0
32.9
8.3
4
1.
11.5
1.1
11.2
1.0
11.7
1.1
10.9
1.0
w.
38.2
12.6
40.4
8.6
41.3
9.1
35.0
9.3
6
1.
11.0
0.9
11.3
1.4
11.7
1.4
11.1
1.2
8
w.
37.5
8.7
40.0
14.6
43.7
10.2
38.3
10.0
1.
11.3
0.7
11.3
0.8
11.3
0.8
11.5
1.0
w.
38.8
7.9
37.6
8.8
37.9
8.1
40.0
9.2
10
1.
11.9
0.8
11.8
1.0
12.0
1.0
11.5
1.2
w.
41.2
5.9
41.9
9.6
43.3
6.2
35.9
7.4
Rearing Time: day Length: cm
Weight: g
A: Reared in sea water containing 0.5 yg/1 of methylmercury
B: Fed the prawn containing 0.133 yg/1 of methylmercury
C: Reared in sea water containing the suspended solids and the bottom sediment from Minamata Bay
D: Control
-------
Experiment B
Sea breams were reared in a tank (1000 1) holding aerated sea water for
10 days. Sea water was replaced daily. The prawn (Penaeus japonicus) was
obtained from a fish farm and reared in the sea water containing methylmer-
cury. Then the prawn was used as bait. The content of methyl mercury in the
prawn was 0.133 yg/g. The amount of the bait eaten was about 7% of the sea
bream's body weight per day. Ten of the sea breams were removed from the
tank every 2 days and the methylmercury in the fish was measured by gas
chromatography.
Experiment C
Three kg of the bottom sediment from Minamata Bay containing 0.015 mg/kg
(wet weight) of methylmercury and 192 mg/kg wet weight) of total mercury was
placed on the bottom of the fish rearing tank (1000 1). Sea water was added
to the tank and aerated by an agitating pump, and then the sea breams were
reared in the tank for 10 days. The bottom sediment and sea water were
replaced daily. Ten of the sea breams were taken out of the tank every 2
days and the methylmercury in the fish was measured by gas chromatography.
Figure 2. Experimental apparatus
for Experiment C.
a- fish rearing tank (1000 1)
b: agitating pump
c: net
d: bottom sediment vessel
Experiment D
Sea water was added to the fish rearing tank (1000 1) and aerated by an
agitating pump. Then the sea breams were reared in the tank for 10 days.
Sea water was replaced daily. Ten of the sea breams were removed from the
tank every 2 days and the methylmercury in the fish measured by gas chromatog-
raphy.
92
-------
The prawn (0.018 yg/g of methylmercury) obtained from a fish farm was
used as the bait for each group except the B group. The amount of the bait
eaten was about 7% of the sea bream's body weight per day. Each sample
consisting of 10 of the sea breams was homogenized and then used to measure
the methylmercury content. The temperature of the sea water during the 10-
day experimental period was between 25.1 and 28.5°C.
RESULTS
The concentration of methylmercury accumulated in the sea bream is shown
in Table 2 and Figure 3. The methylmercury concentration in the fish of the
A group increased gradually from 0.12 yg/g (muscle tissue) to 0.033 yg/g
(muscle tissue) for 10 days, that of the B group increased gradually from
0.012 yg/g (muscle tissue) to 0.020 yg/g (muscle tissue) for 10 days, that of
the C group increased gradually from 0.012 yg/g (muscle tissue) to 0.016 yg/g
(muscle tissue) for 10 days, and that of the D group increased gradually from
0.012 yg/g (muscle tissue) to 0.015 yg/g (muscle tissue) for 10 days. The
methylmercury accumulation in the fish of the A group was evidently higher
than that of the other groups. The methylmercury accumulations in the fish
of the B and C groups were almost the same as that of the D group. However,
the methylmercury accumulation in the fish of the B group was slightly higher
than that of the C group and that of the C group was almost the same as that
of the D group (the control).
TABLE 2. THE METHYLMERCURY CONCENTRATION IN THE RED SEA BREAM
Rearing
Experimental\ Time 0 2 4 6 8 10
Group
A
B
C
D
0.
0.
0.
0.
012
012
012
012
0
0
0
0
.019
.017
.011
.011
0
0
0
0
.019
.012
.016
.015
0.
0.
0.
0.
022
018
013
014
0
0
0
0
.038
.023
.019
.023
0.033
0.020
0.016
0.015
Rearing Time: day methylmercury concentration: yg/g (wet wt. of muscle)
A: Reared in sea water containing 0.5 yg/1 of methylmercury
B: Fed the prawn containing 0.133 yg/g of methylmercury
C: Reared in sea water containing the suspended solid and the bottom sediment
from Minamata Bay
D: Control
93
-------
(muscle tissue)
0.04
c
o
•5 0.03
9
3
O
O
3
O
0.02
I o.oi
i r
i I I I L
i i
8
10 Days
Figure 3. The relation between rearing time and methylmercury
accumulation.
A: reared in sea water containing 0.5 yg/1 of
methylmercury
B: fed the prawn containing 0.133 yg/1 of methyl
mercury
C: reared in sea water containing suspended solid
and bottom sediment from Minamata Bay
D: control
DISCUSSION
In experiments on methy!mercury accumulation in fish, it would be more
desirable to try a rearing experiment for 50-100 days or more. A special
laboratory was not available to continuously supply the large amount of sea
water required to rear marine fish. Conventional equipment was available
only for this experiment so the term of the experiment was limited to 10
days.
Experiment A was designed to observe the accumulation of methlymercury
from sea water via fish gills. Experiment B was designed to observe the
effect of the methylmercury accumulation by the food chain. And experiment C
was carried out to observe the effect on methylmercury accumulation by the
intake of suspended solids containing methylmercury.
94
-------
In experiment A the methylmercury concentration in the sea water was set
at the concentration given as the maximum tolerance limits in Japan for water
in the environment (0.5 yg/liter). The methylmercury concentration in the
prawn used for experiment B was about 10 times as much as that in the prawn
used for experiments A, C and D. Superfluous bottom sediment was used in
experiment C because it was considered that both suspended solids containing
methylmercury and dissolvable methylmercury from bottom sediments were cumula-
tive factors.
Experiment D was the control group and the increase of methylmercury in
the fish of experiment D has the same meaning as the increase occurring in
the natural environment via the normal food chain. In experiment B, the
methylmercury concentration of the prawn used as the bait was 10 times as
much as that of the prawn in the natural environment. However, the methyl -
mercury accumulation in the fish of the B group showed only a small increase.
Therefore, it is concluded that the food chain is not necessarily an important
factor for the accumulation of a large amount of methylmercury.
In experiment C, the concentration of suspended solids (SS) was 50 ppm
in sea.water and the superfluous bottom sediment was on the bottom of the
tank. This condition is almost the same as conditions which occur during
dredging work. The methylmercury accumulation in the fish of the C group was
the same as that of the D group. Therefore, it is concluded that the sus-
pended solids and the bottom sediments are not effective pathways for the
accumulation of methylmercury in fish. In experiment A, the concentration of
accumulated methylmercury in fish increased distinctly in spite of the low
concentration of methylmercury in sea water (0.5 yg/liter). Therefore, it is
concluded that dissolved methylmercury in sea water is one of the critical
factors for methylmercury accumulation in fish.
CONCLUSION
It was found by these experiments on environmental methylmercury accumu-
lation in marine fish that mercury in the suspended solids and bottom sedi-
ments did not accumulate in the fish, that the accumulation via the food
chain was unexpectedly low, and that dissolved methylmercury in sea water was
the critical agent for methylmercury accumulation.
95
-------
DETERMINATION OF TRACE AMOUNTS OF METHYLMERCURY IN SEA WATER
H. Egawa and S. Tajima*
Department of Industrial Chemistry
Faculty of Engineering
Kumamoto University
ABSTRACT
In determining methylmercury (MeHg) concentration,
gas chromatography after extraction with benzene and
glutathione is common, but the concentration of MeHg in
sea water is generally so low that this common method
can not be directly used. In this study chelating
resins which have a selective adsorption for MeHg were
investigated as a means of preconcentrating MeHg in sea
water.
The trace amounts of MeHg in sea water can accur-
ately be determined in the concentration range from
0.005 pg/1 to 0.05 yg/1 (as Hg) after preconcentration
of MeHg by adsorption and elution using chelating resin
in a batch method.
Macroreticular chelating resin (A) containing
episulfide groups was excellent for both the adsorption
of MeHg and the elution of it with hydrochloric acid.
The adsorption of MeHg on the resin (A) attained equil-
ibrium after shaking for 12 hours at 30°C. The calibra-
tion curve of MeHg added to deionized water, synthetic
sea water and natural sea water had excellent linearity
in the concentration range of 0.005 yg/1 to 0.05 yg/1
and it was only slightly affected by mercuric ions and
other various ions in sea water.
The following method is recommended. A 0.2 g
chelating resin (A) is shaken with 1 liter of sea water
for 15 hours at 30°C. MeHg in the elutriate is first
extracted with benzene and then with glutathione solu-
tion from benzene. MeHg in glutathione solution is
then analyzed by the flameless atomic adsorption tech-
nique. The concentration of MeHg is determined from
the calibration curve.
*2-39-l Kurokami, Kumamoto-shi, Kumamoto 860, Japan
96
-------
This method was applied for the determination of
MeHg in sea water samples collected in Minamata Bay and
the adjacent sea.
INTRODUCTION
In the process of dredging bottom sediments containing mercury compounds
the mercury compound may dissolve in sea water under certain conditions. The
mercury content in sea water, particularly methylmercury (MeHg), must always
be checked during the process to prevent secondary pollution. This is because
the dissolved MeHg is accumulated directly by fish (1).
The concentration of MeHg in sea water is generally so low that the
usual method cannot be applied directly to such a sample. The determination
of trace amounts of total mercury, using flameless atomic absorption spectro-
photometry after preconcentration of samples, has been reported by many
authors. Nishimura et al. (2) reported that as low as 0.005 pg/1 of total
mercury in sea water, which is acidified with H2SOit to stabilize the concen-
tration of mercury, can be determined after preconcentration of mercury on
silver metal particles. Baltisberger et al. (3) investigated the separation
and identification of nanogram quantities of MeHg, Hg(I), and Hg(II) in an
aqueous solution by using isothiocyanatopentaaquochromium in an ion exchange
procedure. But they have not tested less than 0.1 pg/1 of mercury in environ-
mental water samples because of the problem of background contamination from
reagents.
This paper investigates the method of determining trace amounts of MeHg
in sea water by preconcentration, using chelating resins having selective
adsorption for MeHg.
EXPERIMENTAL METHODS
Chelating Resin
The macroreticular chelating resins used in this study were prepared in
our laboratory. They have selective adsorption for MeHg. The estimated
structure of a functional group in these chelating resins is shown in Figure
1. For comparison the commercial chelating resin Diaion CR-10, containing
amino diacetic acid groups, was also used.
Reagent
100 mg/1 standard stock solution of mercury was prepared from special
grade chemicals of methylmercurychloride and mercuricchloride obtained from
the Wako Pure Chemical Industry LTD. 10 yg/1 and 100 ug/1 standard solutions
were prepared before use from a 1 mg/1 intermediate standard solution. The
other reagents (hydrochloric acid, benzene, reduced glutathione etc.) used in
this study were obtained from Wako Pure Chemical Industry Ltd. A synthetic
sea water was prepared by the method of Lyman-Fleming (4).
97
-------
(A) RG-S (B) RSS (C) RGS-I (D) RGS-II
CM, -CH2-CH- CH3 Oh
-CH?-C- -CH;-C-
1
COCH2CH-CH2 ^s^ COCHpCH-CH2 COCH2CHCH2OCCH2CH2
» \ / i ii I i (I / ii " /
0 S CH2SH 0 SH SH 0 OH 0 SH
(E) RCS (F) RST (G) RMT (H) RMH
CH3 -CH2-CH- CH3 CH3
1 JL 'I
-CH2-C- P^NI -CH2-C- -CH2-C-
COCH2CH-CH2 t^Jj C(NHC7H,)?NH7 CNHNH2
0 OH SH CH2(NHC2HJ3NM? 0 0
(I) RNH (J) CR-10
H -CH2-CH-
-CH2-C-
. C=NOH
NH? CH7N(CH2COOH)?
Figure 1. Macroreticular chelating resins.
Adsorption Procedure
A precise amount of chelating resin was placed in a stoppered Erlenmeyer
flask, the aqueous solution containing MeHg was added to the flask, and the
flask was mechanically shaken in a constant temperature bath at 30°C for the
designated time (batch method). After the adsorption the resin was separated
from the solution by filtration and rinsed with an adequate volume of deion-
ized water and dried for 2 days at room temperature.
Elution Procedure
The resin was placed in a stoppered 100 ml Erlenmeyer flask, hydrochloric
acid solution was added to the flask, and the flask was mechanically shaken
in a constant temperature bath at 30°C for 3 hours. After the elution the
resin was separated from the elutriate.
Extraction Procedure
MeHg in the elutriate was extracted to 100 ml of benzene after the
concentration of hydrochloric acid in the elutriate was adjusted to one
Normal, and then it was extracted with 10 ml of 0.05% reduced glutathione
solution.
98
-------
Analysis of mercury
The concentration of mercury in samples prepared in the above procedure
was analyzed by the flameless atomic absorption technique, using the instru-
ment of Rigaku Mercury SP (Rigaku Electric Company, Japan). The detection
range of mercury used in this study was usually in the 0 to 5 ng range.
RESULTS AND DISCUSSION
Adsorption of Methylmercury on Chelating Resin and Subsequent Elution of it
from the Resins
The chelating resins used in this study were synthesized in our labora-
tory and had selective adsorption for mercury in mole order concentrations.
The first thing done was to examine the selective adsorptive ability of these
resins for MeHg in low concentrations and the subsequent elution of MeHg with
hydrochloric acid from the resins.
The following procedure was carried out. A 0.1 g chelating resin was
placed in a stoppered 100 ml Erlenmeyer flask, 50 ml of 10 yg/1 MeHg solution
were added to the flask, and the flask was shaken mechanically for 3 hours at
30°C. The amounts of MeHg adsorbed on the respective resins were determined
from differences in the initial and residual concentrations of MeHg. The
resins separated after the adsorption of MeHg were placed in a stoppered 100
ml Erlenmeyer flask, 50 ml of 2N-HC1 or 25 ml of 4N-HC1 were added to the
flask, and the flask was shaken mechanically for 3 hours at 30°C. MeHg in
the elutriate was analyzed after the extraction procedure as described in the
experimental section. The results are presented in Table 1.
The resins (A), (B), and (E) had excellent adsorption for MeHg. MeHg
could be eluted completely from resins (A) and (E) by 4N-HC1 but could not be
eluted completely from resins (B) and (C). 4N-HC1 was a better eluent of
MeHg than 2N-HC1. MeHg was not decomposed by the acid. It was concluded
from the above that the chelating resin (A), which contains episulfide groups,
is the most adequate for the purpose of these studies.
Effect of Adsorption Time on Recovery of Methylmercury
The time taken for the adsorption of MeHg on the resin to reach equilib-
rium was investigated. 0.2 g of chelating resin (A) was placed in a stoppered
2 liter Erlenmeyer flask, 1 liter of 0.05 yg/1 MeHg solution was added to the
flask and the flask was shaken mechanically for periods ranging from 3 to 48
hours at 30°C. The elution was carried out under constant conditions.
Because of the true concentration of MeHg used in this investigation, the
MeHg adsorbed on the resin could not be determined from the residual concen-
tration of MeHg in the solution after adsorption. Therefore, the recovery of
MeHg through the procedure of adsorption, elution and extraction for each
adsorption time was determined. The results a-re shown in Figure 2. It was
found that adsorption equilibrium is reached after 12 hours of shaking at
30°C.
99
-------
IAIJI I J. AU',OKI'IION AND LLIJIION Of Ml (HYLMERCURY BY USING CHEATING RESINS
S in
Adsorption (I)
MclUj ridsorhcd Porr.firiUfjf} of
d/q as Hg/'j-R) adsorption (%)
luent. (3)
Molkj fTutVd Percentage of
(H'J as Hg/g-R) elutlon (%)
(A) KG-',
(B) NV,
((.) WV.-
(u) w/>-
'
/
1
/
1
(
1
4.
4.
4.
4.
4.
4.
4.
4.
4.
4.
i.
'i.
(2.
'
/
1
1
'}.
4.
2.
2.
'1.
'I/
M
tj'l
60
'10
V
l.'l
Ki
'JO
'10
40
'to
03
40
47
17
08
4?
%
95
98
100
93
94
89
89
O'l
93
73
72
47
/'I
7"j
47
45
/''
.0 a
.0 (<,
.6
(<
ij f4
, fj (-
.0 „
.9 c,
.5 «
,'j ft
.9 a
.8 p.
. U (i
.9
.4 n
.1
. '< |i
•
4]
1.
1.
'1.
3.
'i.
3,
3.
4.
?.
?.
1,
2.
3.
1.
1.
2.
80
38
99
99
11
96
43
54
85
05
83
92
95
10
77
H'l
94
87.
100.
43.
43.
72.
90.
83.
85.
89.
100.
60.
84.
94.
86.
• 89.
HI.
88.
86.
0
2
9
3
3
6
1
7
f,
2
'i
5
2
8
3
6
0
0
(I) KM
(fi) RMT
(II) RMH
(I) RNH
(J) f.R- 10
(I) 0,1 g of resin war, shaken with 50 ml of 10 ug/1 (as Ikj) MeHg solution for
3 hours at 30"C. (2) Resin adsorbed MeHg was shaken with IIC1 for 'J hours
,it. 'JO"C. ('0 „: 2N-HM ml, fi; 4N-HC1 25 ml
100
0 10 20 30 40 50
Adtorptlon tlmt (hr)
Figure 2. Effect of adsorption time on recovery of methyl-
mercury. Adsorption: Resin 0.2 g/MeHg solution
0/j ug/1 (as Hg), shaking at 308C.
Tlutlon: 4N-HC1 25 ml, shaking for 3 hr at 30°C
100
-------
The effect of the time Interval between adsorption and elutlon on the
recovery of MeHg was also studied. The result,-, are shown In Figure 5. When
the elutlon was carried out soon after the adsorption, the recovery of MeHg
was slightly greater than 1n the case where the elutlon was done after 7
days-. After that, the recovery of MeHg was not affected, even 1f the resin
was allowed to stand at room temperature for over 2 days nfter th<- •id
of MelUj.
100
80
I
6
Time
6
(day)
10
12
Figure 3. l.ffect of time- Interval between adsorption
and elutlon on the recovery of methylmereury.
Adsorption and elutlon: same as Flqure 7.
This Implies that trace amounts of MeHg 1n natural waters are able to be
determined by preconceritratlon using chtlatlng res Ins because the recovery of
MeHg will be constant after the adsorption has attained equilibrium. Recovery
will not be 100 percent, however.
Ca11bratlon Curve for Trace Amounts of Methylmercury
from 0.01 pg/1 to 0.05
solution of EDTA or
The calibration curve for the method under study was determined as
follows: A standardized 10 pg/1 MeHg solution was diluted with delonlzed
water to obtain a series of MeHg sample solutions ranging in concentration
pg/1 (as Hg). The glassware was washed with an aqueous
.SgO-, and with a dilute add solution and then rinsed
with delonlzed water before use. This was to decrease blank values 1n this
procedure. Then 0.2 g of chelatlng resin (A) were shaken mechanically with 1
liter of the sample 1n stoppered 2 liter rrlenmeyer flasks for 1'j hours at
30"C. The resin was dried for 7 days at room temperature (after the separa-
tion from samples) and was then shaken mechanically with 7.^ ml of 4N-HCI 1n a
stoppered 100 ml Erlenmeyer flask for '5 hours at 30"C. Mellq 1n the elutriate
was extracted at first with benzene and then with glutathione solution from
benzene. Through this entire procedure the trace amount of Meii'j 1n 1 liter
of sample was finally concentrated 1n 10 ml of 0.05% glutathlone solution.
101
-------
One ml of the glutathione solution was analyzed by the fTameless atomic
absorption technique. The data represented the MeHg recovered (reported as
ng of Hg.
The results shown in Figure 4 illustrate that the calibration curve has
an excellent linearity for concentration of MeHg. It has been found that
MeHg concentration in water samples can be determined from the calibration
curve. It is considered that the datum for 0 ug/1 (no addition of MeHg) is
attributed to the reagents used in this procedure.
0.02
Concentration of MeHg
0.04
as Hg)
Figure 4. Calibration curve of methylmercury
added to deionized water.
•First time
oSecond time
Effect of Inorganic Mercury on the Calibration Curve of Methylmercury
Inorganic mercury compounds (Inorg Hg) usually exist in greater quantity
than MeHg in natural water samples and are also adsorbed on the chelating
resins. The effect of Inorg Hg on the MeHg calibration curve was investi-
gated.
A calibration curve of MeHg in the concentration range of 0.01 yg/1 to
0.05 ug/1 plus Inorg Hg, was determined by the procedures outlined in the
previous section. The concentration of Inorg Hg in the solution used in this
experiment was 0.5 pg/1 as mercury. This value was based on the limiting
value in the natural environment. The results are shown in Figure 5.
102
-------
0.02
Concentration of MeHg
0.04
as Hg.)
Figure 5. Effect of inorganic mercury on the cali-
bration curve of methyl mercury.
oMeHg and Inorg Hg (0.5 ug/1 as Hg) added
to deionized water
•MeHg added to deionized water
The calibration curve almost agreed with that of the MeHg solution which
did not contain Inorg Hg. It is concluded that Inorg Hg scarcely affected
the determination of MeHg in this procedure. Although MeHg and Inorg Hg
coexist in samples, and both are adsorbed in chelating resin (A), MeHg is
effectively separated from Inorg Hg by subsequent elution and extraction
procedure. This is because Inorg Hg is hardly eluted by 4N-HC1, and even if
Inorg Hg is eluted slightly, it is scarcely extracted with benzene from 1N-
HC1.
Calibration Curve for Determination of Methylmercury in Sea Water
The effect of various ions contained in sea water on the calibration
curve of MeHg was investigated. The experimental procedure was the same as
the method described previously. The calibration curve for MeHg added to
deionized water in the concentration range of 0.01 yg/1 to 0.05 yg/1 was made
at the same time. The calibration 'curves of MeHg added to the synthetic sea
water and the deionized water are shown together in Figure 6.
The calibration curve of MeHg added to the synthetic sea water also had
excellent linearity and was in agreement with that of MeHg added to deionized
water. In comparing these two calibration curves it is concluded that MeHg
can be adsorbed on the chelating resin in the presence of various ions con-
tained in sea water and can then be eluted with 4N-HC1.
103
-------
I
0.02 0.04
Concentration of MeHg (>jg// as Hg)
Figure 6. Calibration curve of methylmercury
added to sea water* -(I)
SMeHg added to synthetic sea water
oMeHg added to deionized water
*Synthetic sea water prepared by Lyman-Fleming method
The calibration curve of MeHg added to natural sea water in the concen-
tration range of 0.005 yg/1 to 0.05 yg/1 is shown in Figure 7. The natural
sea water was collected from an area which was not contaminated by mercury
and was filtered with No. 1 filter paper.
The calibration curve had good agreement when repeated three times. On
the basis of the above results it has been found that trace amounts of MeHg
contained in sea water can be determined accurately in the concentration
range from 0.005 yg/1 to 0.05 yg/1.
Determination of Methylmercury in Sea Water Samples
Sampling stations are shown in Figure 8. Sea water samples were col-
lected using a Van Dorn water sampler and filtered with No. 2 paper.
Chelating resin amounting to 0.2 g (A) was added to 1 liter samples of
filtered sea water immediately after sampling and all the previous procedures
were carried out. The concentration of MeHg in a sea water sample was deter-
mined from the calibration curve described previously. The results are
presented in Table 2.
104
-------
50 -
0 0.02
Concentration of MeHg
0.04
(ppb as Hg)
Figure 7. Calibration curve of methy!mercury
added to sea water* -(II)
•First time oSecond time oThird time
*Natural sea water, collected from an
area which was not contaminated by mercury
TABLE 2. METHYLMERCURY IN SEA WATER SAMPLES
Sampling
station
Depth from the
surface (m)
(Hg yg/1)
Date of sampling
April 23, 1976 June 3, 1976 August 10, 1976
a
b
c
0.5
4.5
10.0
0.013
0.032
<0.005
0.010
0.005
<0.005
<0.005
105
-------
Kbiji Island
?' T^ Fukuro-Bay
:• --cL si/-..'. . ^
^^M^-:.
:. '. • •• ^v;™.\n??r?'. • •'.
;'•. Hyolckisri port
Figure 8. Sampling stations—a, b, c.
REFERENCES
1) M. Fujiki, R. Hi rota and S. Yamaguchi, "Reports of the studies on Mina-
mata Disease," edit, by Japan Public Health Association (1976) p. 16.
2) M. Nishimura, K. Matsunaga and S. Konishi, Bunseki Kagaku, Jtt, 655
(1975).
3) R. J. Baltisberger and C. L. Knudson, Anal. Chem., 47_, 1402 (1975).
4) J. Lyman and R. H. Fleming, J. Marine Research, 3^ 134 (1946).
106
-------
BEHAVIOR OF HEAVY METALS AND PCBS IN DREDGING AND TREATING OF BOTTOM DEPOSITS
K. Murakami* and K. Takeishi**
Public Works Research Institute
Ministry of Construction
ABSTRACT
Many problems concerning water quality arise when
bottom deposits containing various toxic substances,
such as heavy metals and PCBs, are dredged and treated.
These problems are dealt with in this paper, centering
around the results of laboratory experiments on the
solubility of these toxic substances when contained in
bottom deposits and solidified deposits, and the
treatment of waste water from processes of handling
dredged deposits. The summary of results follows:
(1) The deposit constituents were markedly
variable according to particle size, varying with
the kind of deposit. The content of heavy metals
and PCBs tended to be higher in finer grained
sediments.
(2) Mercury and PCBs released from sediments
into the overlying water were very low in concen-
tration and most were bound to suspended particles.
(3) Concentration of dissolved PCBs in the
wastewater from dredging operations was very low,
and dissolved mercury concentration was also low
in the normal range of pH. Therefore, it seems
that the quality of effluent from dredging opera-
tions can be improved to a level which conforms
to the effluent standards by eliminating suspended
solids.
(4) Elutriate tests showed that mercury trans-
ferred from the deposits into the water tended to
increase sharply when the solvent was high in pH
value. When mercury-containing deposits were
solidified with a solidifying agent of the cement-
**
Chief, Water Quality Section
Research Sanitary Engineer, Sewage Works Section
5-41-7 Shimo, Kita-ku, Tokyo 115, Japan
107
-------
lime group, the solubility of mercury measured by
the standard elutriate test was greater for solified
deposits than that for the orignal deposits. This
was because of a rise in pH value of the solvent.
However, dissolved PCB obtained by shaking from
solidified deposits was very low in concentration,
not more than 1 yg/1.
(5) Even if the solvent is high in pH value, the
amount of mercury transferred from the deposits to
the water could be remarkably lowered by decreasing
the water content of the deposits and by oxidizing
them.
(6) Redissolved heavy metals from solidified
deposits (other than Hg and PCB) were very low in
concentration.
INTRODUCTION
Deposition of sediments containing a large amount of toxic substances,
such as heavy metals and PCB, has caused a kind of social problem in Japan,
and bottom deposit dredging is now being carried out in various places as one
measure of water pollution control. One of the most important things in a
dredging operation is to prevent the dispersion of toxic substances into the
environment in the course of dredging and treating deposits. If the dredging
operation is performed without sufficient understanding of the behavior of
these toxic substances and without avoiding the dispersion of them into the
environment, the possibility exists that the efforts to control pollution
would instead cause secondary environmental pollution.
The method of dredging and treating of bottom deposits may differ depend-
ing on the characteristics of the deposits to be handled and the geographic
and social conditions of the area where the deposition took place. However,
a general flow diagram for a dredging operation may be expressed as shown in
Figure 1. Dispersion of toxic substances in bottom deposits into the environ-
ment, either in dissolved or particulate form, can occur from every handling
process shown in the figure.
Solid-Liquid
Separation
/
\
Solidification
and/or drying
•Disposal
Treatment of
Supernatant
•Discharge
Figure 1. Schematic flow diagram of dredging operation.
108
-------
These problems are disscussed in this paper with particular emphasis on
the dissolving of toxic substances from bottom deposits and the laboratory
experiments which are the basis of the results.
CHARACTERISTICS OF THE BOTTOM DEPOSITS USED IN THE EXPERIMENTS
The characteristics of the 4 kinds of deposits used in the experiments
are given in Table 1. Sample A (collected from the port of Tagonoura) was
from a bottom deposit formed mainly by paper mill waste discharges. Sample B
(Minamata Bay) was from a sandy deposit and had relation to chemical industry
wastewater discharge. Sample C (Naka no Umi - a salt lake) was related to an
electrical industry and fairly low in moisture content. Deposit D (The
Tsurumi River) was collected from the tidal reach of an urban river. (Here-
after, samples of these bottom deposits are simply referred to as A, B, C and
D).
TABLE 1. CHARACTERISTICS OF THE SEDIMENTS USED IN THE EXPERIMENTS
Water Ignition
A
B
C
D
Content
85
70
54
55
Loss
/
-------
TABLE 2. HEAVY METALS IN THE SEDIMENTS USED IN THE EXPERIMENTS
(Hg in mg/kg and others in mg/g)
Fe Zn Mn Pb Cu Cr Ni Cd Hg
A
B
C
D
Clarke
Number
9.91
44.10
29.93
63.0
48.3
1.320
1.218
0.103
0.588
0.060
0.
0.
0.
0.
0.
106
960
346
506
950
0.406
0.537
0.029
0.438
0.015
0.322
0.913
0.031
0.222
0.055
0.128
0.357
0.036
0.096
0.100
0.112
0.140
0.047
0.094
0.075
0.
0.
0.
0.
0.
148
021
0073
0015
002
0.527
298
0.448
0.567
0.08
CONTENTS OF HEAVY METALS AND PCB BY PARTICLE SIZE GROUP
Each of the bottom deposit samples was divided into classifications by
sieving into several groups by particle size, heavy metal content and PCB
content to clarify the relation between particle size and Hg and PCB contents.
The results are shown in Figures 2 and 3. Table 3 lists the contents of PCB
and Hg shown in Figures 2 and 3, and also gives particle size groups as
percentage to the total content.
Results for PCB: The total PCB content of Sample A was extraordinarily
high. The percentage of PCB content in the particle size group of less than
74 y was overwhelmingly higher than those in the other groups, i.e., the PCB
content of this size group accounted for 99.7% of the total content (Table 3).
Results for Hg: Hg content tended to be higher in finer particles in
all the deposit samples except A, and about 90% of the Hg was contained in
the particle size group of less than 74 y in B (Table 3). The concentrations
of other heavy metals were also generally higher in the finer particles. But
Sample A tended to be different from the other samples in the contents of
many heavy metals. There was no definite trend in the distribution of heavy
metal content in Sample A. This is probably because most of the constituents
of the deposit were specific substances, artificially produced and the heavy
metals contained in it were introduced under different conditions when com-
pared with those in the other samples.
Relation among heavy metals: Relatively good correlations were observed
between Cu and Zn content and between Cu and Pb content, but there were no
notable correlations between the others (Figures 4 and 5).
As mentioned above, toxic substances were in many cases contained in
specific particle size groups. Though the particle size which exhibits the
highest concentration is variable (depending on the sediment characteristics
and the toxic substances) it can be said that these toxic substances as a
110
-------
100
80
-= 60
£
40
20
150
100
-J.
-4
u.
a.
E
-
50 i
L.T.74 74 105 250 420 840 2000
Particle Size!//)
SO
E
-1 2
E
•f\
30O
200 -
E
a
(S.
100 =
LT74 74 105 250 420 840
Particle Size-G/1
Figure 2. Relationship between PCB Figure 3. Relationship between Hg
content and size of sediment particles, content and size of sediment particles
TABLE 3. SEDIMENT PARTICLE SIZE GROUPS VS. PCB AND HG CONTENT
Particle
Size
(y)
L.T. 74
74-105
105 250
250 - 420
420 - 840
840 - 2000
M.T. 2000
Weight
Ratio
of Solid
(%)
86.07
1.59
3.96
1.79
1.87
3.34
0.97
Sample A
PCB
Content
(mg/kg)
117.0
0.69
3.99
1.41
1.73
3.30
1.98
Weight
Ratio
of PCB
(%)
99, 65
0.01
0.16
0.02
0.03
0.11
0.02
Weight
Ratio
of Solid
(%)
75.68
0.56
4.07
12.71
2.95
2.76
0.12
Sample B
Hg
Content
(mg/kg)
284.5
77.2
133.0
82.9
54.0
58.1
• « _ _•
Weight
Ratio
of Hg
(X)
91.40
0.18
2.29
4.47
0.67
0.99
111
-------
10
o»
E I
"c
Q>
T3
Q>
cO,l
3
u
0.01
1 1 1 1 1
—
A
—
: *
1 1 1 1 1
1 1 I 1 1 1 1 1 1 1 1 | 1 1 1 1
V :
A ty
n • A
4 B —
AC
i i i i 1 1 I I II 1 i I I 1 1
0,1 I 10 100
Zn in Sediments (mg/kg)
Figure 4. Relationship between Cu and Zn in sediments.
10
o>
JC
0>
c
Q)
^
0)
1 1 1 II
—
A
A A
1 A^
_
1 1 1 1 1
1 | i I i I I I I i I i | 1 1 l 1 1
• ~
y/o {
D «A
4B
AC I
DD 2
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0.01 0,1 I 10 100
Pb in Sediments (mg/kg)
Figure 5. Relationship between Cu and Pb in sediments.
112
-------
rule have a tendency to be contained in the finer particles of bottom depos-
its. Therefore, attention must be paid to the fact that resuspension of
bottom deposits at the time of dredging and disposal of untreated effluent
from handling and treating spoils will cause fine particles of deposits to
disperse and will result in environmental pollution due to any toxic sub-
stances contained in the dredged deposits.
RELEASE OF H6 AND PCBS INTO OVERLYING WATER FROM BOTTOM DEPOSITS
Experimental Method
A 10 cm thick sediment sample was laid at the bottom of each 75 liter
cylindrical vessel and either sea water or fresh water was placed over the
sediment in the cylinder. The water in each cylinder was kept either under
anaerobic conditions by an air-tight seal at the top of the cylinder or kept
under aerobic conditions by aerating the water. In both cases the water was
slowly mixed to ensure a uniform concentration throughout. All the experi-
ments were carried out at a constant temperature of 20° or 30°C. During the
experimental period of 500 days, water samples were regularly taken from each
cylinder and analyzed for PCB or Hg as well as pH, ORP, SS, TOC and other
parameters.
Sediment samples used in the experiments were types A and C for the
experiment on mercury, and types B and D for that on PCB. Other se'diment
samples collected from rivers were also used after adjusting the PCB or Hg
contents.
In addition to the 75 liter-cylinder test, smaller scale experiments
were done using 300 ml flasks to supplement the cylinder test. In the flask
test a sediment sample was placed in a series of flasks and the flasks were
filled with distilled water. These flasks, after being glass-stoppered, were
stored in a 20°C constant temperature room and were opened sequentially for
water quality analysis to examine the release of PCB or Hg from sediments to
overlying water.
Release of PCB
The experiment included twelve 75 liter cylinder tests and ten flask
tests. The PCB added to the river sediment samples used in the 75 liter
cylinder tests was a mixture of KC (Kaneclor) 300, KC 400, KC 500 and KC 600
with a weight ratio of 1:1:1:1 and the PCB content in the samples was adjusted
to 50 or 100 mg/kg (on a dry basis). In the flask test the mixture mentioned
above as well as each project (KC 300-600) was used to adjust PCB contents in
the samples.
The ranges of pH and ORP variation of the overlying water were respec-
tively 6.5 to 8.5 and -0.4 to 0.1 V. The concentration of PCB in the water
decreased successively in most cases with no relation to ORP or pH. In some
cases comparatively high concentrations of PCB 30-60 yg/kg) were observed.
At these times suspended solids in the water also tended to be high. When
the PCB concentrations were corrected (on the assumption that the sediment
PCB content in each case was 100 yg/kg) in order to examine the relationship
113
-------
between the PCB and SS in the water, a comparatively good correlation was
seen as shown in Figure 6. The solid line in the figure shows the relation-
ship in which all PCB in the water is present in the form of suspended solids
From this figure it was concluded that the resolutilization of PCB from
bottom sediments to overlying water is very small.
5 10 20 30 4O 50 100 2OO 300
SS
-------
TRANSFER OF HG AND PCB INTO THE SUPERNATANT IN
THE DEWATERING OPERATION OF DREDGED DEPOSITS
In order to reduce the contents of Hg and PCB in the supernatant from
mechanical dewatering processes, experiments on the treatment of supernatant
obtained by the leaf test of Deposits A and B were carried out by chemical
coagulation with metal salts and/or a polymer.
The PCB contained in the supernatant of sample A was considered to be
mostly bound to suspended solids, as shown later (Figure 9). Therefore, it
seemed possible to reduce the concentration of PCB in the supernatant to the
level of the effluent standard by the removal of suspended solids.
In the case of Hg, when lime was used as a conditioning chemical for
filtration, the soluble Hg concentration tended to increase in the supernatant
because of a rise in pH, and the concentration of residual Hg was 10 yg/1 or
more, even after chemical coagulation. Therefore, the effect of pH on the
solubilization of Hg from bottom deposits was further examined using elutriate
tests. Deposit sample B was added to distilled water at a concentration of 3
g of solids per 100 ml (on a dry basis) and the pH of the mixture was adjusted
to several levels with NaOH or H2SOU. After violent shaking the supernatant
of each mixture was filtered through a 0.45 y membrane filter and the filtrate
was analyzed to examine the relation between the Hg concentration or COD and
the pH value. The results are shown in Figure 7. The pH value of the mixture
without pH control was 8.4.
150
100
a
o
50
300
200
100
4 6 8 IO
pH of the Solvent
12 i4
Figure 7. Relationship between solubilization of
Hg and COD from the sediments and pH of
the solvent. Obtained by the elutriate
tests.
115
-------
The concentration of soluble Hg in the supernatant was sharply increased
at about pH 11 and the elutriate ratio reached 3.1% at pH 12.8. Obviously pH
value has a great influence on the behavior of mercury contained in deposits.
Therefore, changes of pH value should be avoided as far as possible in the
treating of dredged spoils.
TREATMENT OF WASTEWATER FROM DEWATERING PROCESSES OF DREDGED DEPOSITS
The deposit dredging operation system now widely in use is as follows:
pump dredging —> pipe transportation —> landfill. In this system, the
water content of dredged deposits is usually kept at more than 90% because of
pump and pipe transportation requirements. Therefore, a large quantity of
excess water returns from landfill disposal sites, and when deposits contain
heavy metals and PCBs it is especially important to keep the quality of
effluent higher than the effluent standard in order to carry out successful
spoils disposal. In the present study, the possibility of treating the
supernatant containing Hg and PCB was investigated using deposit samples A
and B.
Treatment of Wastewater Containing PCB
Sample A was added to distilled water at a concentration of 3 g dry
solid/100 ml water and shaken. After a quiescent period, the supernatant was
taken and used as the water sample for the experiment on chemical coagulation.
PAC (polyaluminum chloride) and/or an anionic polymer were used as coagulants.
Figure 8 indicates the relation between the coagulant dosage and the turbidity
of the supernatant. The effect of PAC in reducing turbidity was greatest at
a dosage of about 1000 mg/1. When the polymer was added to the PAC, the
turbidity was at a minimum with a polymer dosage of 10 mg/1.
Figure 9 shows a correlation between the turbidity and the PCB concentra-
tion. In this figure, data obtained by chemical clarification of the super-
natant from vacuum filtration of deposit sample B are included. The correla-
tion between the turbidity and the PCB content was fairly good. From the
fact that a correlation between turbidity and PCB in treated water was
observed not only in the samples prepared, by a kind of elutriate test as in
this experiment, but also in the interstitial water of deposits, it seems
that the influence of the solid content or salinity on the solubilization of
PCB is rather slight. The sample water, prepared by a kind of elutriate test
as mentioned above, was filtered through several kinds of membrane filters
with different pore sizes, and the relation between turbidity and PCB of the
filtrate was examined. These results are also shown in Figure 9. When these
data are compared with the other data obtained by chemical coagulation, it
can be seen that the PCB content tended to be a little higher in the former,
suggesting that a part of the soluble PCB was removed by chemical coagulation.
If PCB contained in water filtered through a 0.45 jj filter is defined as
soluble PCB, then the content of soluble PCB in the supernatant was confirmed
by physical stirring to be not more than 3 yg/1 under such conditions of
solubilization. Therefore, it is considered possible to obtain effluent that
conforms to the effluent standard if suspended solids are completely removed
by chemical coagulation and/or filtration.
116
-------
30
fc
5 20
TJ
la
u
3
.0
No Polymer Addition
Polymer 5 mu /
10 •
15 «
600 700 800 900 IOOO 1100 1200
PAC Dosage (mg//)
Figure 8. Relationship between residual turbtdi.ty and
coagulant dosage.
100
m
o
Ou
X Supernatant from Vacuum Filtration
O Chem Clarified Effluent: PAC only
D • :PAC + 5mg// Polymer
^ ' :PAC+10mg// Polymer x
10
X
A X
X
X^«
x x
" on A
A OD o
O •
A D *"
• Chem Clarified Effluent: PAC f ISmg'/ Polymer
^ * : Polymer only
• Elutriate Tests
O.I I 10 TOO
Turbidity (FTU)
Figure 9. Relationship between PCB and turbidity in
various kinds of effluent from bottom deposits
117
-------
PCB and its Solubility
PCB used in Japan in the past was almost exclusively Kaneclor, and
Kaneclor includes 4 main products, KC 300, KC 400, KC 500 and KC 600. The
figures following KC stand for chlorine content; for instance, KC 600 contains
60% chlorine. PCB becomes higher in viscosity and lower in solubility with
an increase in chlorine content.
Table 4 shows the solubility of each PCB product, KC 300-KC 600. In
Experiment I PCB was dissolved in distilled water by shaking violently, and
allowed to stand for 10 minutes. Then samples were taken from the middle
part of the water column and used for analysis. In Experiment II PCB was
dissolved in the same manner as in Experiment I and, following filtration
through a 0.45 p filter, the filtrate was used for analysis.
TABLE 4. SOLUBILIZATION OF PCB
Experiment I Experiment II
KC-300
KC-400
KC-500
KC-600
0.092 mg/1 0.068 mg/1
0.072
0.018
0.012 0.006
As mentioned above, the solubilization of PCB from deposits is very
small and most of the PCB transferred to the water phase is considered bound
to suspended solids. But the solubility of PCB itself as shown in Table 4 is
fairly high, much higher than the level of the effluent standard. Therefore,
depending on the characteristics of the-deposits, there may be a possibility
that more PCB is resolubilized.
PCB is a mixture of various chlorinated biphenyls and exhibits 29 peaks
on a gas-chromatogram of 9 chlorinated compounds with 2-9 chlorines. Figure
10 indicates the percentages of various chlorinated compounds in two products,
KC 300 and KC 600, and in their water soluable fractions. The composition of
the water soluble fraction are those with lower chlorine numbers and the
composition of the water soluble fraction is considerably different from that
of KC 600 itself. That means the solubility of PCB is higher in compounds
with lower chlorine numbers than in those with higher chlorine numbers.
Treatment of Mercury-Containing Wastewater
Deposit sample B contained much sand and the quality of the supernatant
obtained by elution of the deposits was fairly clean. Accordingly, when
treated by chemical coagulation in the same manner as in the case of sample
A, the Hg concentration of the supernatant could easily be decreased by the
addition of an inorganic coagulant (several tens of yg per liter) to a level
118
-------
50
= 40
BO
a.
a
c
L-
-------
lower than the detection limit (0.5 ug/1). Therefore, treatment by ordinary
sedimentation was also examined. Deposits were added to sea water or dis-
tilled water at a solid content of 10 g/100 ml and 3 g/100 ml (dry deposit/
water) and, after shaking, changes of the quality of the supernatant with
settling time were examined to examine the efficiency of the gravity treatment
consolidation alone.
The relationship between the settling time and the Hg concentrations of
the supernatant is shown in Figure 11. The quality of the supernatant seemed
to be poorer with sea water than with distilled water, probably because of
the lower settleability of particles in the former. But in all the cases the
Hg concentration could be decreased to a lower level than the effluent stan-
dard by 24 hours quiescent settling.
Figure 12 shows the relationship between SS and Hg in the supernatant as
observed in the above settling test. This figure indicates that there is
little influence by salinity or solid content on the concentration of soluble
Hg in the supernatant. There was a fairly good correlation between the SS
and the Hg content. The solid line in the figure indicates that all the
mercury in the water is included in suspended solids, which are the solids of
deposit sample B. Data in the figure agree fairly well with the solid line.
Therefore, it is assumed that almost all the Hg exists bound to suspended
solids and its solubility in water is very low under conditions of physical
stirring.
10
100 200
SS(mR//)
Figure 12. Relationship between Hg and turbidity in
supernatants obtained by elutriate tests,
120
-------
SOLUBILIZATION OF TOXIC SUBSTANCES FROM SOLIDIFIED DEPOSITS
Disposal of deposits containing toxic substances such as heavy metals is
provided for in the "Ordinance of the Prime Minister's Office on the standards
for judgment of harmful industrial solid wastes—Tests for toxic substances
contained in industrial solid waste" (February, 1973). Elutriate tests for
toxic substances should be performed before landfill disposal. If the elut-
riate ratio is higher than the standard, then measures must be taken to
prevent toxic substances from diffusing out when deposits are solidified with
cement, etc. In this section, the results of experiments on solubilization
of toxic substances from solidified deposits are discussed. Sediment samples
A and B were used for this experiment.
Solubilization of Toxic Substances from Solidified and Crushed Deposits
Sediment samples were mixed with several separate kinds of solidifying
agents, and each of them was put into a 5 x 10 cm form and cured in wet air
at 20°C for 7 days. The solidified deposit obtained was subjected to an
unconfined compression strength test and then crushed into particles according
to the "Tests for toxic substances contained in industrial solid wastes."
The particles were sieved, and the ones with a size of 0.5-5 mm were placed
in distilled water adjusted to pH 7.8-8.3 with NaOH. The solid content was
adjusted to 10 g dry sol ids/100 ml water). The mixture was shaken for 6
hours and the supernatant was filtered through 5C filter paper; the filtrate
was used as the sample for analysis.
Some of the results obtained by the above mentioned standard elutriate
test are given in Table 5. These data were obtained from solidified deposits
of about 1 kg/cm2 in strength. The elutriate ratio is defined as the ratio
of the amount of a substance dissolved in the water to the amount present in
the deposit.
The pH of the solvent (distilled water) increased with the amount of
solidifying agent added. The solubilization of PCB from solidified deposits
was very low—concentration in the filtrate was between 0.3 and 1.0 yg/1.
The concentrations of Cd, Cr and Pb in the filtrate were also low—at or
below the detection limit in almost all cases—and showed that an increase in
pH did not affect the solubility of these metals. However, the concentration
of Hg was considerabley higher (0.7-144 yg/1) when compared with the other
heavy metals and with the standard for Hg concentration (5 yg/1). This
increased Hg concentration is probably due to the increased pH of the solvent.
Figure 13 shows changes with curing time of the soluble Hg concentration
in the filtrate. The data on the zero day of curing were obtained by perform-
ing the elutriate test immediately after mixing in the cement. The solubili-
zation of Hg showed a strong decline after 3 days curing, but declined more
slowly after that, until the change became practically nil after about 30
days of curing. The cement dosage affected the solubilization of mercury by
increasing solubilization with an increase in the cement dosage while the
dosage was low. However, as the dosage became high, the solubilization
reached the maximum rate, and then decreased gradually with the increase in
the dosage.
121
-------
TABLE 5. RESULT OF ELUTRIATE TESTS USING SOLIDIFIED AND CRUSHED DEPOSITS
(Figures in parentheses are elution ratios in percentages)
ro
ro
Compress ive
Name of Initial Strength of
Deposit Water Content Solidifying Solidified
Sample of Deposit Agent and Dosage Deposit pH COD Cd Pb Cr Hg PCB
(«) (g/lOOg dry solid) (kg/cm) (mg/1) (mg/1) (mg/1 ) (mg/1 ) (ug/1) (ug/1 )
A 54.5 Cement
A 64 . 3 Cement
A 65.5 Slaked Lime
Sand
A 65.5 Quick Lime
Sand
B 56.6 Cement
B 30.5 Cement
B 56.6 Slaked Lime
B 56.6 Quick Lime
20 0.97
40 1.00
38 0.89
190
40 1 . 03
100
20 0.98
20 1.17
80 0.73
*
40 0.65
10.0 114 0.9
(1.30) (0.002)
11.7 155 1.0
(2.37) (0.03)
12.7 100 0.5
(2.46) (0.02)
12.7 101 Tr.
(2.07) ( - )
12.1 203 N.D. N.D. N.D. 22.4
(11.0) ( - ) ( - ) ( - ) (0.19)
11.4 63 0.001 N.D. 0.02 N.D.
(2.5) (0.24) ( - ) (0.19) ( - )
13.0 179 N.D. N.D. N.D. 35.6
(12.0) ( - ) ( - ) ( - ) (0.37)
1.29 214 N.D. N.D. N.D. 83.4
(12.6) ( - ) ( - ) ( - ) (0.75)
-------
10
20 "-• 40
Period of Curing(days)
Figure 13. Effect of curing period on resolubiliza-
tion of mercury from solidified sediments
(Standard Elutriate Test).
Although deposit sample B has a very high Hg content of 300 mg/kg, when
an elutriate test was performed without solidification the soluble Hg in the
filtrate was only 2 yg/1. Therefore, solidification by cement or lime is
meaningless as far as the solubility of Hg per unit surface area is concerned.
The effect of solidifying agents which raise the pH value of a solvent should
only be regarded as a physical fixing of the deposits themselves.
Solubility of Toxic Substances from Bulk Solidified Sediments
The solubilization of toxic substances from bulk solidified sediments
was investigated by two kinds of experiments:
Experiment I: The sediment (Sample A) was mixed with cement to form
solidified spherules weighing 67-87 g. Each solidified spherule contained 25
g of deposit of a dry basis. Several solidified spherules prepared under the
same conditions were soaked in distilled water in a series of 2 liter glass
bottles. Water in each bottle was analyzed sequentially after predetermined
periods, and the solubility of toxic substances was investigated.
Experiment II: Cement-solidified deposit cubes weighing 320-380 g were
prepared using samples A and B. Each cube was soaked in 40 liters of dis-
tilled water or sea water for about 40 days. The solubility of toxic sub-
stances was examined by taking water samples during the experimental period.
123
-------
In the tests with sample A (Experiment I) the pH of the solvent (water)
increased from to 10 to 12 in the early stages and then decreased gradually
due to the absorption of C02 from the atmosphere. The increase in pH seemed
to be influenced by the constituents of each solidified cube i.e., if the
cement content was fixed, the increase of pH was greater when the water
content was higher and the strength of the cubes was lower. When the water
content was fixed, the pH increase was greater with a high cement content in
the solidified deposits.
The concentration of PCB in the solvent was less than the limit of
detection (0.1-0.6 yg/1), except for one case which showed a maximum value of
1.1 pg/1. As PCB is a very stable compound, and difficult to influence
chemically, it is probable that solidification is effective in reducing the
solubility of PCB.
In Experiment II the pH value of the solvent gradually increased for
about 20 days, but the increase was especially sharp in the first 5 days.
The ORP of the solvent tended to be low when the pH was high, but there was
not a definite trend.
In considering the solubility of heavy metals, Cd seems to have diffused
out a little from solidified Deposit A, but its concentration was less than
the detection limit in the other experiments. Therefore, it may safely be
said that Cd is hardly solubilized under these conditions. The concentrations
of T-Cr and Hg were hardly more than the detection limit; the determination
of Mn, Fe, Cu and Ni were performed only on the last day of the experimental
period, but none of them could be detected in the solvent with the exception
that Cu content was 0.01-0.18 mg/1 in Deposit A, and Fe content was about
0.25 mg/1 in both A and B when samples were soaked in sea water.
As mentioned earlier, in the elutriate test using solidified crushed
deposits the Hg content of solvent tended to increase with a rise of pH
value. But, in the soaking test of bulk solidified deposits, the solid-
ification was effective for confinement of Hg, and even if the pH of the
solvent was increased, no notable solubilization of Hg was observed.
Factors Affecting the Solubilization of Hg in Deposits
In ordinary practice the bottom deposits are dredged, and then dried and
oxidized under the conditions of landfill disposal. In order to investigate
the effect of drying on the solubilization of Hg, deposit samples were air-
dried and the solubilization of Hg was then measured using elutriate tests.
In addition, the effect of solvent pH on the solubilization of Hg was again
examined in order to confirm the results mentioned above. The results are
shown in Table 6.
The solubilization of Hg evidently increased with a rise in pH. This
was especially true when the pH was adjusted with NaOH and the deposits
entered a colloidal state as a result of which the solubilization of Hg was
remarkably increased. But, if deposits were dried before treatment, the
solubilization of Hg was noticeably low, and this phenomenon was especially
remarkable at high pH values. Therefore, a fixed amount of Ca(OH)2 was added
124
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TABLE 6. EFFECT OF DRYING OF DEPOSITS ON SOLUBILIZATION OF HEAVY METALS
(Obtained by elutriate tests. Figures in the parentheses are elution ratios in percentages)
ro
ui
Name of
Deposit
Sample
A
A
A
A
A
A
B
B
B
B
B
B
Water
Content pH Condition
of Deposit of Solvent
(*)
85.
85.
85.
0
0
0
2L.1
21.
21.
57.
57.
57.
6.
6.
6.
1
1
0
0
0
96
96
96
pH
pH
PH
pH
pH
pH
pH
pH
pH
pH
PH
PH
8 by
13 by
13 by
8 by
13 by
13 by
8 by
13 by
13 by
8 by
13 by
13 by
NaOH
NaOH
Ca(OH)2
NaOH
NaOH
Ca(OH)2
NaOH
NaOH
Ca(OH)2
NaOH
NaOH
Ca(OH)2
pH
7.7
13.1
12.1
5.5
13.0
12.8
9.0
11.3
12.7
8.0
12.7
12.8
COD
(mg/1 )
52.7
(0.25)
2710
123
87.4
1840
113
16.8
(0.37)
181
109
80.4
167
72.5
Cd
(mg/1 )
0.009
(0.04)
N.D.
N.D.
N.D.
0.004
N.D.
N.D.
0.009
N.D.
0.001
N.D.
N.D.
Pb
(mg/1 )
N.D.
0.04
N.D.
0.02
0.04
0.01
N.D.
0.654
N.D.
Tr.
0.02
0.13
Cr
(mg/1)
N.D.
0.06
N.D
N.D.
0.06
N.D.
N.D.
0.160
N.D.
N.D.
0.01
N.D.
Hg
Ug/i)
N.D.
3.9
0.6
N.D.
5.2
N.D.
2.0
(0.01)
179 '
148
0.8
3.5
0.7
-------
to each of several deposit samples (which were different in water content
from each other) and the'solubilization of Hg from each sample was examined
by elutriate test. The intent was to observe the relationship between the
degree of drying of the deposits and the solubilization of Hg from them. The
results are shown in Table 7. The pH of the solvent was not greatly influ-
enced by drying, but the ORP changed markedly from the oxidized state to the
reduced state. The solubilization of Hg decreased sharply with the decrease
of water content. From this result, and from the fact that Hg did not dis-
solve out of solidified-crushed deposits with an initial water content of
30.5% (Table 5), the conclusion is that drying of deposits seems to be greatly
effective for decreasing the solubilization of Hg.
TABLE 7. EFFECT OF DRYING DEPOSITS ON SOLUBILIZATION OF MERCURY
(obtained by elutriate tests)
Initial
Water Content
of Deposit
(*)
6.83
14.15
23.93
36.61
54.69
pH
11.8
11.9
11.8
11.7
12.2
ORP
(mV)
+144
+123
+128
-233
-214
COD
(mg/D
104
141
110
126
106
Hg
(pg/D
0.9
0.3
0.4
35.2
44.9
Diffusion of Heavy Metals Added to Deposits
As mentioned above, the solubilization of heavy metals from natural
bottom deposits was very generally low and that of Hg was also low unless it
was influenced by some specific factor such as an increase in pH. In order
to investigate the heavy metal-stabilizing capacity of deposits, soluble
heavy metals were added to deposits and then the transfer of the metals into
the water phase examined using the elutriate test.
A mixed solution of Cd(N03)2, K2Cr207 and HgCl2 or a solution of Pb(N03)2
was added to deposits A and B at a content of 100 mg/kg (mg of each metal/kg
dry solid). Samples were taken at 10 day intervals and the transfer of each
heavy metal into the water phase was examined using the elutriate test.
Analysis was carried out 4 times at intervals of 10 days, but the soluble
metals in. the water phase were always less than the detection limits. This
result indicates that every soluble heavy metal added was changed to a stable
and insoluble form in the deposits.
126
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A STUDY ON THE BEHAVIOR OF MERCURY-CONTAMINATED SEDIMENTS IN MINAMATA BAY
T. Yoshida* and Y. Ikegaki**
ABSTRACT
This study was undertaken by the Bottom Sediments
Management Association, on the request of Kumamoto
Prefecture, to investigate the behavior of mercury-
contaminated sediments in Minamata Bay in regards to
the plan to remove them by dredging. This plan for
dredging and disposal of contaminated sediments in
Minamata Bay was presented by Mr. Sakemi at the meeting
last year in Corvallis, Oregon, USA, (Figure 1). This
year it was decided to put the project into practice
beginning in 1978. But there are still some technical
problems to be solved before the removal operations can
begin. One of them is how to treat the toxic metal
compounds contained in the sediments, especially mercury
compounds, without causing any adverse effects on the
surrounding environment. Several tests were conducted
on the behavior of mercury compounds in sediments
during the dredging and disposal operation. This paper
describes the test results and methods of non-polluting
treatment of mercury compounds in Minamata Bay dredge
spoils.
INTRODUCTION
The sediments in Minamata Bay are heavily contaminated by mercury com-
pounds which were deposited from the waste water discharged from the Chisso
chemical factory. Mercury chloride or mercury sulfate was used there as a
catalyst for the synthesizing of vinyl chloride or acetaldehyde. After the
outbreak of the famous Minamata disease, there has been much investigation of
the cause of the disease, the formation of organic and inorganic mercury in
chemical reactions or in the sediments, and the transition mechanism of
methylmercury from fish to the human body. But there have been few studies
on the behavior of mercury in sediments from the standpoint of sediment
treatment. As the sediments are dredged and disposed, the metallic mercury
in them will become subject to new conditions, i.e., dredging, pumping,
settling ponds, land fills, etc. How does mercury behave in these new condi-
tions? To find out, the authors conducted a series of sediment treatment
tests and observed the behavior of mercury compounds under these conditions.
* Japan Bottom Sediments Management Association, Sankyo Bldg. 2-7-12 Tsukiji,
Chuo-ku, Tokyo 104, Japan
**Environmental Department, Kumamoto Pref. 6-18-1 Suizenji, Kumamoto 862, Japan
127
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SAMPLING OF SEDIMENTS
The samples used for tests were taken from the sea bottom outside of the
planned embankment, as shown in Figure 1. The sampling was done by hand with
two divers, using a 50 ton barge, 150 ps tug boat and 30 ps diver boat. The
two divers picked up predetermined quantities of sediments taking care that
the samples not be diluted, and filled up large drums with them. The drums
were covered and sealed at the sea bottom and then pulled up (Figure 2).
The ocean depth at the sampling site was 10-12 m and bottom soil was
sampled between the surface and 80 cm in depth from the surface. The color
of the soil was blackish to 20 cm depth and grayish below 20 cm.
ANALYSIS OF PHYSICAL AND CHEMICAL CHARACTERISTICS OF SEDIMENTS
The samples were analayzed according to the following authorized methods.
i) Soil test standards by the Japanese Society of Soil Mechanics and
Foundation Engineering.
ii) Guideline "Provisional Criteria for the Removal of Bottom Sediments"
iii) Japanese Industrial Standards
The analytical results of the sediment tests are shown in Table 1. As
shown, about 95% of the sediment composition consists of silt and clay, and
large quantities of toxic materials as well as mercury are contained in it.
MICROSCOPIC OBSERVATION OF THE SEDIMENTS
The sample sediment was diluted to 350 mg/1 in SS (suspended solids)
concentration and then, by using a concentric settler, it was divided into 4
fractions according to particle sizes.
As shown in Figure 3, the fractions were microscopically observed.
The grain sizes of the fractions are 100 y (first), 30 y (second), 13 y
(third) and 4 y (fourth). The first one is mostly sand particles, and the
second for the most part consists of dead organisms or their fragments. The
third contains many salients, and the fourth is a structure mixed with white
flakes and needle-shaped particles.
The electron micrographs at magnifications of 1,OOOX and lO.OOOX are
shown in Figure 4. In these the "flowers" of soil mineral are visible.
X-RAY DIFFRACTION ANALYSIS OF SEDIMENTS
The samples were also observed by X-ray diffraction, and a typical
result is shown in Figure 5. In the fourth fraction, with a particle size of
4 y, the presence of Feldspar and Montmorillonite is recognized and also
mercuric sulfite, lead sulfite and mercuric sulfate are detectable.
128
-------
( ?8 Minamata Bay
Figure 1. Sampling site.
I
Figure 2. View of sampling.
129
-------
TABLE 1. PROPERTIES OF SEDIMENT
Item
Unit
Measured Values
Color
Odor
(H20)
PH
Gray blackish
8.13
(KCI)
Water Content
wt. (g) of water ,nn S03
C02
CuO
PoOq "
ZnO
V MnO
8.06
292
2.578
1.16
18.2
420
22
12
231
0.003
1.7
238
65
1750
928
<0.01
0.01
0.3
1.5
1.52
6.0
36.2
4.3
9.7
9.5
2.9
5.7
2.4
trace
M
n
n
130
-------
SECOND FRACTION
FOURTH FRACTION
Figure 3. Micrographs of Sediments
SECOND FRACTION
FOURTH FRACTION
Figure 4. Electron micrographs of sediments.
131
-------
Feldspar
o
Montmorillonite
Mercury(I) Sulfate
\
Pvrophillte
Mon tmorlllonlte
f
Fo Idspar
Pyrophl11te
16
20
25
2 e
30
35
40
Figure 5. X-ray diffraction spectrum of sediment.
BEHAVIOR OF MERCURY BY PHYSICAL ACTIONS
Settling by Gravitation
The sample sediment was diluted with the artificial sea water "Aqua-
marine" into 8 kinds of SS concentration which were about 50, 100, 500,
1,000, 5,000, 10,000, 50,000 and 100,000 ppm. A 2 liter cylinder was used
for the gravity settling of each sample. Figure 6 shows the relationships
between settling time and total Hg concentration and also between settling
time and turbidity of the supernatant in the cylinder.
The relationship between the residual content of total mercury in the
supernatant and the intial concentration of SS was shown in Figure 7. A
residual total Hg, defined as the ratio of the total-Hg concentration in the
supernatant to that in the sample, was also plotted against the initial SS
concentration in Figure 7. From these results it was noted that (1) the
larger the degree of dilution, the greater the residual total-Hg and SS, and
(2) the maximum concentrations of total-Hg and turbidity in the supernatant
were observed in a range of from 1,000 mg/1 to 5,000 mg/1 of the SS concentra-
tion in diluted samples.
Mercury Behavior under Mechanical Agitation of Sediment
A mixture of sediment and Aquamarine, the volumetric percentages of
which were 10% and 90% respectively, was prepared and 40 liters were agitated
132
-------
T. Mg
Tiirhidity
Figures: Initial Concentration of SS
0 I 2345^789 10
Settling Time In Hrs.
24 48 72
Figure 6. Relationships between settling time and T.Hg, and turbidity.
SO 100
560' 1000 5000 10000 50000 100 000
Initial Conccntr.itIon of SS (pom)
Figure 7. Plots of T.Hg cone, and residual T.Hg against initial cone, of SS.
133
-------
for 60 minutes by a hand mixer with turbine blades in a 60 liter polyethylene
vessel. Samples were taken after elapsed times of 5, 10, 30 and 60 minutes
from the start of agitation and were then passed through filter paper Toyo-
roshi No. 5C (pore size: 1 y). The concentration of total-Hg in the fil-
trates was always below 0.5 y'g/1.
Mercury Behavior with Pump Circulation
Sixty liters of the mixture was reciprocally moved from one polyethylene
vessel (100 liters) to another by a pump. It was then examined to see if the
pumping agitation would have any influence on total-Hg contained in the
solids. The pump circulation was repeated 10 times and the mixture was
allowed to settle for 16 hours. The settled solids were divided into four
equal parts (by distance) from top to bottom which were (A) the top layer,
(B) the upper layer, (C) the middle layer, and (D) the bottom layer. Total-
Hg content was measured for each layer. A mixture that settled for 16 hours
without pump circulation was used as a control and total-Hg contents of the
settled solids were measured by the same procedure. Figure 8 shows the
results in the total-Hg measurement for both the samples. The concentration
of total-Hg in the upper layer was higher than in the lower one. Also the
concentration of total-Hg in the sample of circulated solids was lower than
in the noncirculated sample. Perhaps the fine particles adhering to the
larger and heavier ones were detached due to the circulation. It is worth-
while to note here that the mercury in the particles of the sediments are not
easily released from the sediment particles to the water, even if they suffer
physical disturbance such as agitation or pump circulation.
2 TO
260
250
240
230
220
210
200
190
180
170
circulated
upper
r -- J- — middle •!• - boltom —
C layer o layer
Figure 8. Effects of pump circulation on total-Hg cone,
134
-------
BEHAVIOR OF MERCURY UNDER FILTRATION
Filtration Test
The supernatant of the settled mixture which was made of 10% (volumetric)
sediment was used for filtration tests. Total-Hg and turbidity of this
supernatant were 79 mg/kg and 105 degrees, respectively. Three types of
filter membranes were employed. They were (1) Membrane Filter RA (Milipore
Co. Ltd.): pore size 1.2 ± 0.3 y; (2) Membrane Filter MA: pore size 0.45 ±
0.2 y; (3) Membrane Filter VA: pore size 0.05 ± 0.03 y. Each filtrate of
the supernatant through these filter membranes contained a total-Hg concentra-
tion of less than 0.5 yg/1.
Permeation Test of Mercury
The tests on the permeability of mercury were carried out in such a way
that 3 kinds of embankment fill materials (coal fines, silt, and sand) were
packed in columns, and the sediment liquid, diluted by Aquamarine, was sup-
plied under pressure to the tops of the columns.
The test equipment consisted of the 3 filter columns of transparent
vinyl chloride, with an inside diameter of 160 mm. They were 1 m, 2 m and 3
m in height. A holding tank of 1 m3 was employed for delivering pressurized
liquid (Figure 9).
The filter media - fine coal, silt and sand - have permeability coeffici-
ents of 3.48 x 10"**, 3.76 x 10"6 and 2.43 x 10"2 cm/sec and mean grain sizes
of 19.5, 440 and 490 microns, respectively (Figure 10).
Test conditions were set up as follows:
The inlet pressure at column top 0.5 kg/cm2
The circulating rate 1.5-1.6 1/min
The concentration of SS 8,460 ppm and 35,000 ppm
The test operation period 15 days cont.
To avoid the accumulation of suspended solids over the surface of the filter
bed the liquid was always agitated at the upper part of the columns. The
relationships between permeation time and the quantities of permeates are
shown in Figure 11.
The permeation rates after 15 days of operation were 0.1-0.15 I/day for
coal fines, 0.1-0.3 I/day for silt, and 11.0-21.9 I/day for sand. The perme-
ability of sand was larger by 37-220 times than that of coal fines and silt.
The concentrations of total-Hg in the permeates were almost always less than
0.5 yg/1. This is shown in Figure 12.
The relationships between the thickness of the three filter layers and
the SS concentration of the permeates are plotted in Figure 13. The effect
of thickness on the permeability of SS is remarkable and greatest for the
silt material. From these data, it may be concluded that a probability of
mercury leakage through the embankment is very small.
135
-------
Figure 9. View of permeation test plant.
105 ti 420/J__ ZOOOxj 952""" 254mm508mm
1 I I
I 00 r —
74>j 250/1 840iU 4760w 19 I mm 33 lmm
0001
0005 001
005 O I 0510
GraIn s i 7c (m/m)
50 10 0
Gra 1 n ^ i ?.
5QO
riay
Si It
Sand
Crave 1
0001 . 0005
0074
20
Figure 10. Size distribution of fill materials.
136
-------
06
0.9 -
- 04
03
2. 02
I I I
I I I I
06
05~ -
0 123 4 9 6 7 S 9 10 II 12 13 14 IS
Pi-cmo.it ton Time Days
A. COAL FINES
0 4
Q3
02
1 I I
1 T
Column Length 1 ra _
j I
0 I 2 345 6 78 9 10 II 12 13 14 IS
[Vrmr.it ton Time In D.iys
a SILT
2.5
^2.0
1.5
1.0
£0.5
1
Turbidity 10,000 degrees
I i i
5 10 15
Permeation Time in Hrs,
C. SAND
20
Figure 11. Relationship between permeates and permeation time,
137
-------
^
o>
20
10
^ 05
§ 04
* «.
1
ju
"o
o>
E
o
c
o
-------
REMOVAL OF SS CONTAINING MERCURY COMPOUNDS
From the preceding test results it has been recognized that mercury
compounds are firmly bound to the solid particles of the sediments, i.e.,
mercury compounds are not easily released by physical disturbances. There-
fore, in order to remove mercury compounds, it is necessary to remove sus-
pended solids. It then becomes a matter of importance to estimate the SS-
removing capabilities of various sediment treatments.
Coagulation Test of SS Containing Mercury Compounds
Among the various treatments for removing SS, coagulation is the best.
As a first step, tests of coagulation were conducted as follows.
i) The liquid sample of 1 liter is premixed in a beaker (1 liter) for
30 seconds at a mixing rate of 150 rpm.
ii) A certain amount of inorganic or organic coagulant is added to the
beaker and the sample is mixed for one minute at a mixing rate of
150 rpm.
iii) Then follows a slow mixing at 60 rpm for 3 minutes after which the
sample is allowed to settle for 30 minutes.
iv) To measure various items (flocculating times, sizes of floes,
settling velocities, water properties, etc.) under varying loads of
suspended solids five samples were prepared. The SS contents of
these samples were 50, 100, 500, 1,000, 5,000 mg/kg.
v) Two kinds of reagents, inorganic and organic, were used. The
inorganic agents, which facilitate clearing, were Alum and PAC. The
organic agents, which accelerate precipitation, were sodium algin-
ate, sodium polyacrylate and polyacrylamide. The polyacrylamide is
classified into 2 kinds according to the chemical structure, one of
them having an electric charge (anion), another non-charged (non-
ion). The relationship between dissolving time and liquid viscosity
of these two kinds of polyacrylamide is shown in Figure 14.
PA-331
AnIonic
i 01 %1iquid I
Kurifloc
Nonionic
Dissolving Time in Minutes
Figure 14. Relationship between dissolving time and viscosity.
139
-------
Settling by Gravitation
The relationship between the concentrations of mercury and settling times
are plotted in Figure 15. The figure indicates that it is very difficult to
get the Hg concentration below 0.5 ug/kg in the supernatant, even if a long
time is allowed for settling.
0.2
02 04060 810 2 4 6 810 20 40 6080 f00 I 4 6 8 10
';< i ' 1 iiVfi, Tine (It)
Figure 15. Plot of Hg concentration against settling time.
Settling by Chemical Agents
Figure 16 shows the relationships between the settling velocities of floes
produced and the dosage rates of various kinds of organic flocculants.
From this figure it was found that polyacrylamide was effective in the
flocculation of the liquid sample, but both sodium alginate and sodium poly-
acrylate were not effective. The relationship between the turbidity of the
supernatant and the amounts of the flocculant added for the sample having SS
of 5,000 rng/1 are shown in Figure 17. To obtain a turbidity of 13 to 23 de-
grees, the required PAC dosage was 100-200 mg/1. It is difficult to get the
turbidity below 3 degrees by only using the polymer PA-331. In case of the
combined use of PAC and PA-331 a turbidity of below 2 degrees was attained in
spite of the small quantities used (only 2-4 mg/1). From this it is clear that
the combination of PAC and Kurifloc PA-331 was the most effective coagulant.
140
-------
7
6
Kurifloc
10
10
PA-331
20
28
Figure 16.
Dotage of Pol/aerie Flotcular.t* (pp«)
Relationships between settling velocity
and dosage of flocculants.
200 —
9.2 0406081
4 6 8 10 20 40 60 100 200
J»pm
Dosage of Florrtilants
Figure 17. Relationships between turbidity and dosage of flocculants
141
-------
Relationships Between the Concentrations of Total-Hg and SS
Figure 18 shows the relationships between the total-Hg concentration and
SS remaining in the supernatant. These were obtained by jar-tests of settling
with or without flocculants. From this figure, it is clear that the removal
of mercury may be achieved by eliminating the suspended solids remaining in
the supernatant. Furthermore, it has been proven that in a range of SS around
20 mg/1 the total-Hg concentration may be significantly decreased as the SS
concentration decreases. The figure also indicates that the reduction to about
10 mg/1 of SS in the supernatant may be necessary in order to achieve a total-
Hg concentration of less than 0.5 yg/kg.
2 3 4 5 6 8 10
20 3040506080100 200 ppm
SS ConcenLrntion (ppm)
Figure 18. Plot of Hg concentration against SS concentration.
142
-------
CONCLUSIONS
From the studies the following conclusions have been made.
(1) In order to control the water quality of the final effluent in accordance
with "provisional criteria for the removal of bottom sediments," the concen-
trations of SS in the effluent should be maintained below 10 mg/kg.
(2) In order to obtain a final effluent having an SS concentration of 10
mg/1, it is necessary to treat the spillwater from a settling pond using a
clarification plant.
(3) If chemical precipitation is employed to remove suspended solids, the
combined use of PAC and polyelectrolite (such as polyacrylamide) is recom-
mended.
(4) In the dredging of the sediments there may be no problem concerning
mercury release from dredge spoil particles into the seawater.
143
-------
USING SAND FILL TO COVER DREDGE SPOILS CONTAINING MERCURY
S. Fuji no*
Port and Harbor Bureau
of Kitakyushu City
ABSTRACT
In Dokai Bay of Kitakyushu City, a project to
dispose of contaminated bottom sediments containing
high concentrations of mercury was planned and carried
out. It was the first project to dispose of mercury-
containing sediment in Japan. The characteristics of
the contaminated bottom sediments and the plan for
removal of the sediments were presented and discussed
at the first United States-Japan meeting in Corvallis,
Oregon in 1975 (1). This paper reports on a project to
cover the spoil impounded in a spoil area in order to
prevent wind-borne dust from the dried spoil from
becoming a secondary pollution source.
To achieve this purpose, a layer of sand one meter
thick was placed over the spoil. Since the impounded
spoil was too soft to allow the direct placement of the
sand layer, the use of a "bamboo-net method" was adopted
after studying several alternatives. Rafts made of
thick, long bamboos were placed on the mud over the
entire spoil area and sheets of plastic were then
spread over them. A layer of sand was hydraulically
emplaced and followed by a layer of surface soil.
The purpose of the work was achieved safely,
securely and economically.
SPOIL AREA
Prior to dredging, a spoil area was prepared by enclosing a basin with a
double sheet piled wall. The slopes of the inner sea walls were covered with
plastic sheets to keep the polluted water from the spoil from seeping out.
The details are in the report presented at the first meeting.
The spoil area was 52,600 square meters and in it impounded some 350,000
cubic meters of polluted material, forming a very soft soil some 7 meters
thick at 2.5 meters above the datum level (Figures 1 and 2). The volume of
the impounded spoil was almost the same as that of the dredged sediment,
i.e., no change in volume due to the dredging operation was observed.
* 1-2-7 Nishikaigan, Moji-ku, Kitakyushu-shi, Fukuoka 801, Japan
144
-------
Figure 1. Location of spoil area.
Figure 2. Spoil area.
145
-------
PROPERTIES OF DREDGED SPOIL
Pollutants contained in the bottom sediments at Dokai Bay were described
in the paper presented at the first US-Japan meeting (1). The sediment
contained an average of 50 mg/kg of mercury and considerable amounts of lead,
chrome, cyanide and arsenic. Alkylmercury was not present. It also contained
a significant amount of tar and sulfides—average ignition loss was 16 per-
cent. Mechanical properties of the sediments, obtained from laboratory
tests, are as follows:
Cohesion 0.01 kg/cm2
Compression Index Cc = 1.2
Coefficient of Consolidation Cv = 2.5 x 10"2cm2/min
After the completion of the dredging operation, 85 samples of the spoil were
tested and physical properties of the spoil were obtained as follows:
Water Content 63 - 263% (average 128%)
Specific Gravity
of Spoil Particles 2.16 - 2.65 (average 2.44)
Void Ratio 1.7 - 6.4 (average 3.12)
Particle Size
Distribution Sand 30% (average)
Silt 47% (average)
Clay 23% (average)
Soil Classification Clayey Silt
COVERING PLAN FOR SAND FILL
In order to eliminate bad odors and to prevent the dried surface soil
from being carried by wind, it was decided that the spoil should be covered
as soon as possible.
When the dredging work was complete the spoil was too muddy for any
equipment to have access to it. It also contained significant amounts of
harmful materials, although they were unlikely to elute from the deposits.
In deciding on a method for covering the spoil area, priority was
placed on the worker's safety and health. The covering work also had to be
done economically.
The thickness of the covering soil was to be 1.5 meters thick, one meter
for preventing subsequent pollution and 0.5 meters to permit vehicle travel.
Five alternative methods were studied to help place the 1.5 meter thick
sand fill over the soft spoil impounded in the pond.
a. Covering by means of cloth sheets
Sheets of cloth or woven fabric are often applied to help place a thin
layer of sand on soft ground. This method was rejected because the
dredged material was extremely soft and any unevenness in the thickness
of the sand fill would cause an increase in the volume of sand. Further-
146
-------
more, eruption of the dredged spoil through the sheets was likely and
preventing this is very difficult.
b. Covering by means of sheets and netted ropes
A net made of ropes spread over the above-mentioned sheets has recently
been used in Japan. The net is effective in preventing the spoil from
erupting, and also makes it possible to bring in earth moving machinery.
Unevenness in the thickness of the sand fill was also anticipated and
the amount of soil needed was therefore assumed to be great. This
method was also rejected.
c. Surface stabilization with stabilizing agents
Instead of covering the spoils with membranes, a portion of the surface
layer of a spoil may sometimes be stabilized directly by mixing in a
stabilizing agent, consisting mainly of cement, by using floating equip-
ment. But the stabilized layer might be destroyed due to an accidental
overload. This alternative also was not considered to be economically
feasible.
d. Combined method of b and c
Combined use of the stabilizing agent and a net of ropes was considered
very effective and the amount of sand fill could be reduced compared to
method a or b. This method, however, was very expensive and was accord-
ingly eliminated.
e. Covering by means of sheets and rafts of bamboos (Bamboo-net
method)
In this method rafts of bamboos are placed on top of the mud and then
sheets of cloth are spread over them. Since bamboos are resilient the
rafts will distribute the load of sand fill equally on the soft spoil
and will reduce the needed volume of sand to a minimum. The rafts will
enable workers to lay the membrane safely since the rafts are used as
footholds. This method was finally chosen for its economy and safety.
Two alternatives were studied in placing a thin sand layer over the
bamboo rafts and the sheets of cloth. One used a conveyor system and the
other used a small hydraulic pump dredge to transport a mixture of sand and
water.
The former was rejected because it would be more costly and take more
time. The latter was finally selected for its economy and its certainty in
producing an even, thin layer of sand.
BAMBOO RAFTS
Bamboo rafts were used to distribute the weight of sand placed over
them. In order to determine the spacing of the bamboo members an elastic
foundation analysis was performed. Although the ground consisting of the
dredged spoil was not elastic, the analysis was performed since there was
little experience with this kind of work.
147
-------
A bamboo is known to have a Young's modulus of 120,000 kg/cm2 and a
tensile and compressive strength of 800 kg/cm2. An eight meter long bamboo
with a diameter of 5 cm and a thickness of 0.5 cm has a section modulus of
7.245 cm3 and a maximum resisting bending moment of 5,796 kg/cm.
Assuming that bamboos are beams spaced about 70 cm apart on an elastic
foundation the elastic modulus of which is 0.03 kg/cm3, and also assuming
that the first layer of a fill be placed at one time as shown in Figure 3,
the bending moment, stress and vertical deflection were computed as follows:
Bending Moment
Stress
Vertical Deflection
4,660 kg/cm
450 kg/cm2 (Factor of Safety 1.78)
19 cm
From this analysis it was expected that a raft of bamboos spaced 70 cm
apart both laterally and longitudinally could withstand the weight of a layer
of sand laid as shown in Figure 3. It was decided that the one meter thick
sand fill was to be placed by repeating the operation three times.
81400
I
* i,200
1 : 8
_~--^r_r "V: B "1
Ll^^:
1 20
2.000
I
0)t~BOO
~'~f""l -~-il7T
7oo-a
-------
To protect the workers from accidents, life jackets, rubber gloves and
rubber boots were supplied to all the workers, who always worked in pairs. A
number of boards for footing were used to prevent the workers from falling.
A guard was posted to ensure the safety of the workers. A portable shower
house was on site for use when the workers got soiled or fell into the spoil.
SHEETS
The main purposes of the sheets were to prevent the spoil from erupting
and to prevent the fill material from collapsing into the mud during the
filling operation. The sheets also served as footholds for subsequent work.
To determine the type of membrane, a calculation was carried out which
showed that the sheets should have a tensile strength not less than 16 kg per
centimeter of width. A polypropylene cloth was finally chosen. Its proper-
ties are listed in Table 1. For safety, spaced polypropylene ropes were laid
between each bamboo and fastened to the bamboo rafts (Figure 5).
I
Figure 5. Illustration of safety techniques.
TABLE 1. SPECIFICATIONS OF POLYPROPYLENE COVER SHEETS
Material
Polypropylene PP-1616
Number of mesh
Tensile strength
Elongation
Tensile strength of
sewed portion
longitudinal
lateral
longitudinal
lateral
longitudinal
lateral
16/inch
16/inch
103.3 kg/5 cm
100.0 kg/5 cm
25.1%
14.8%
97.2 kg/5cm
149
-------
42 m x 22 m polypropylene membranes were manufactured at the factory and
delivered to the site. They were joined together after being spread over the
bamboo rafts. The detail of the joint is shown in Figure 6.
(l2mmJn_dl*J
'JOINTING ROPE
.ADDITIONAL SHEET
Figure 6. Joint of sheet.
PLACEMENT OF SAND FILL
Clean sea sand was collected by sand carriers equipped with grab-buckets
and transported to a nearby concrete wharf where the sand was unloaded,
transported to the site by dump trucks, and stockpiled in a pond by means of
belt conveyors. The pond was 85 m long, 18.6 m wide and 3 m deep. The grain
size distribution of the sand was as follows:
D max. = 10 mm
D30 = 0.29 mm
D60 = 0.47 mm
D10 = 0.18 mm
Sea water was let into the stockpiling pond and three portable hydraulic
pump dredges were used to move the sand-water mixture to the fill area. The
dimensions and capacity of the dredges are as follows:
Length
Width
Depth
Draft
Main Pump
Diameter of Discharge Line
Maximum Length of Pipe Line
Maximum Discharge
8 m
2.5 m
0.8 m
0.6 m
Diesel Engine 185 - 175 HP
8 inches
600 m
300 cu. m per hour (water)
60 cu. m per hour (sand)
The dredges sent the sand-water mixture through discharge lines. Each
outlet of the discharge line was extended at a rate of 4 meters every five
minutes, placing the sand fill as shown in Figure 3. The water was recovered
and pumped back into the stockpile pond to be reused since it contained no
pollutants according to laboratory analyses.
The quantity of sand necessary to provide a minimum thickness of 1 meter
was calculated as follows: the difference between the largest and the small-
est displacement of the sheet surface due to elastic compression and plastic
flow of the spoil was assumed to be 30 cm. The difference in further dis-
placement due to uneven consolidation was assumed to be an additional 30 cm.
150
-------
Since the surface of the completed ground had to be flat, the mean
thickness of the sand fill was assumed to be 1.3 meters (Figure 7).
1,00 1,60
(MIN) (MAX)
^^^S^^^^^^^^^^^^:
' ••'•!'"t::': 8.40 "T!' 8.40 "'•''•"''•"•'•'•'
Figure 7. Assumed formation of sand.
The volume of sand to be transported was increased by an additional 15%
to account for volume changes due to the effect of compacting during placement
and loss during handling. After the sand laying was completed the recycled
water was purified in the settling pond and discharged to the sea. Numerous
soundings were made and they showed that the required minimum thickness was
obtained with a mean thickness of 1.31 meters.
PLACEMENT OF SURFACE SOIL
Two months after the sand fill was completed placement of surface soil
was begun to prevent windblown sand dust and to increase the ability of the
spoil area to support traffic. Two months following the sand placement the
covered spoil had been consolidated to such a degree due to the weight of the
sand that small earthmoving equipment could be operated on it. Figure 8
shows the shear stresses caused in subsurface soil by four different truck
loads. Line A in Figure 8 shows the cohesion of the subsurface silt 60 days
after the sand placement. It indicates that a 4 ton dump truck (total weight
approx. 8 metric tons) or lighter equipment can travel on the sand. Three-
ton bulldozers were used to place 20 cm thick finger dikes as shown in Figure
9. These acted as counterweights. They were 30 cm lower than the final
level of the ground. The interspaces between these dikes were then filled,
bringing them to the same level as the dikes, after which a 30 cm thick layer
of soil was laid over the whole area using 12-ton bulldozers. The 3-ton
bulldozers remained at least 20 meters ahead of the follow-up bulldozers,
i.e., the first stage of the dikes extended at least 20 meters in front of
the completed area.
RESULTS AND DISCUSSION
Main materials used in the fill and cover project are listed below:
Bamboo Rafts 52,600 sq. m
Bamboos, 5 cm in diameter, 8 m long
Annealed iron wire, 3.5 mm in diameter
Polypropylene ropes, 12 mm in diameter
Membrane 52,600 sq. m
Polypropylene woven cloth, PP 1616, 42 m x 22 m
Sea Sand 82,000 cu. m
Surface Soil 33,000 cu. m
30,700 pcs.
11 tons
162,000 m
82 sheets
151
-------
SHEAR STRESS STRENGTHkg/cm2)
o o.Q5 mo
E 1.5
—•T-6 LOADING
» TH4 LOADING
T-201DADING
LINE A!
Estimated cohesive strength
at 60 days after completion
of sand fill.
LINE Bl
Estimated final cohesion
Figure 8. Subsurface stress by a dump truck.
BY 12 TON
BY 3 TON BULLDOZER BULLDOZER
t20mMin. I
PLAN
SHEET
> cm
-BAMBOO RAFT
CROSS SECTION
Figure 9. Procedure of surface soil placement.
152
-------
Settling due to consolidation is being measured. Sixty cm of settlement
was recorded four months after the completion of the entire project. In
order to detect the level of contamination of the covering sand due to effects
of filtration and adherence, twelve samples were taken at six points. One
sample was taken from the upper part and one from the lower part of the sand
layer at each point. Samples were analyzed at the Kitakyushu Municipal
Institute of Environmental Health Sciences. The concentrations of main
contaminants in the sand are shown in Table 2. It shows that the sand at the
level 30 cm above the sheet was not affected to a great extent by the contam-
inants contained in the spoils. In another laboratory experiment (S. Yamada,
et al., 1975) similar results were reported (2).
"In this experiment a sand layer of 50 cm in thickness was placed on a
polluted mud filled in polypropylene bags to squeeze its pore water out
of the mud. The concentration of suspended solids in the water taken
from the sand 30 cm above the bag surface was 10 parts per million.
Visual examination showed that the mud which seeped out of the bags
remained in the area less than 10 cm above the bag surface." (sic)
TABLE 2. CONCENTRATION OF CONTAMINANTS IN THE UPPER AND LOWER PORTION
OF THE SAND LAYER COVERING THE TOXIC SPOILS
Concentration (mg/kg)
Contaminants in Upper3 Lower
stockpile pond part part
Cadmium and its compounds 0.033 0.05 0.06
Cyanides --c
Organic phosphorus
Lead and its compounds 2.2 2.2 2.6
Hexachrome
Arsenic and its compounds
Mercury and its compounds 0.014 0.008 0.012
aUpper part: 70 cm above the sheet Lower part: 30 cm above the sheet
c—: "not detected"
Most of the pore water squeezed out of the spoil will rise through the
covering soil and evaporate. Some of it might flow horizontally through the
sand fill into surrounding areas. It was unlikely that pollutants would move
to surrounding areas since most of the pollutants are bound to suspended
solids which would be retained in the sand. To test this hypothesis several
wells were installed in the periphery of the spoil area to monitor the quality
of ground water. Monitoring of the wells has continued and has shown no
abnormalities to date.
15.3
-------
CONCLUSIONS
The "bamboo-net method," introduced as a surface treatment technique to
confine toxic spoils which do not elute, was verified as a satisfactory
technique from the following points of view:
1. The technique does not allow secondary pollution.
2. It is safe and sanitary for the laborers concerned.
3. It is economically feasible.
It was also found that a covering soil of 100 cm in thickness was
sufficient in itself to prevent secondary pollution (such as dust and bad
odors) from occurring. There was also no influence on the periphery of the
area due to exudation of pore water from the spoils. Execution of the tech-
nique does not require sophisticated skills. The proposed thickness of the
covering soil was obtained within a reasonable period of time by applying the
technique to the spoil surface step by step. This allowed the use of the
surface by vehicular traffic in a reasonable time.
The authors hope that this paper will be of some help to those who are
concerned about the management of polluted bottom sediments.
REFERENCES
1) T. Koike. Real application of management techniques in Port Kitakyushu,
The US-Japan Experts Meeting on Management of Bottom Sediments Containing
Toxic Substances, November 1975.
2) S. Yamada, K. Mori, N. Morii. Experiment on disposal of toxic mud by
confining in bags of cloth, June 1975.
154
-------
CHEMICAL STABILIZATION OF SOFT SOILS
T. Okumura*
Chief, Soil Stabilization Laboratory
Port and Harbor Research Institute
Ministry of Transport
ABSTRACT
Chemical stabilization methods have recently been
employed on reclaimed surface soils and in-situ soft
clayey soils. Chemical stabilization is affected by
the characteristics of the soil and the stabilizing
agents. In this paper various kinds of chemical stabil-
izing agents are reviewed, stabilizing effects are
considered, and the test results of comparisons of
different stabilizers are shown. In conclusion, there
is no single agent useful for all kinds of soil and
stabilizing conditions. In many cases it is more
reasonable to use a slightly greater amount of a simple
agent than to use expensive additives.
INTRODUCTION
Toxic sediments have often been treated by means of reclamation. In
these cases the surface should be stabilized as soon as possible to reduce
the possibility of secondary pollution and/or to utilize the reclaimed land.
Recently, chemical stabilization methods have been employed in these
cases as well as physical or mechanical methods such as sand spread and
covered with sheets. Chemical stabilizations are also employed in improvement
of in-situ soft soils (Okumura and Terashi, 1975).
In general the principle of chemical stabilization utilizes the chemical
bonding of soil and stabilizer when they are mixed together. However, the
stabilizing effect of chemical agents also depends on many factors such as
water content, grain size, physio-chemical properties of soil and the type of
agent. For example, Figure 1 shows the variety of stabilizing effects of
quicklime on various chemical agents.
CHEMICAL STABILIZING AGENTS USED IN PRACTICE
Table 1 summarizes the chemical stabilizing agents commonly used on the
reclaimed surface layer and on the in-situ soft soils.
* 3-1-1 Nagase, Yokosuka-shi, Kanagawa 239, Japan
155
-------
TABLE 1. CHEMICAL STABILIZING AGENTS USED ON RECLAIMED SURFACE AND IN-SITU SOFT SOIL
cn
Type
Lime
Portland
Cement
asphalt
additive
Main Component
Quicklime
hydrated lime
slag with lime
gypsum and lime
sludge ash and
hydrated lime
Portland Cement
Portland Cement
and hydrated
lime
Portland Cement
and slag
polymer
polymer
Name of Agent
Quicklime
Chemico Lime
-100
Semii Lime
Hydrated Lime
Road Lime
Slag with Lime
Slag Bacillus
Gypsum with Lime
Hi -Tog
Portland Cement
Cement Mortar
Fuji Beton-FPC
Fuji Beton Toa
-PC, -FK, -AL
Fudo Mix
Chemico Lime
-200, -400
Slag Cement
Denka HS-1, -2
Nisso ALM
EB-CX
Danseal X5
Konseal
Phase in Use
solid
solid
solid
solid/slurry
solid
solid
solid
solid
solid
slurry/solid
slurry
si urry
slurry
slurry
slurry
slurry
solid
slurry
Method of Treatment
mixing (deep/shallow)
mixing (shallow)
lime pile
mixing/lime pile
mixing (shallow/deep)
mixing
mixing
mi xi ng
mi xi ng
mi xi ng
mixing (deep/shallow)
mixing (deep)
mixing (shallow)
mixing (shallow)
mixing (shallow)
sludge mixing
mixing (shallow)
mixing (shallow)
mixing (shallow/deep)
mixing with soil
with cement, for rapid
solidification
ditto, for Hg fixing
Name of Treatment
Deep- Lime-Mixing,
etc.
Chemico Lizer
Chemico Pile
Soil Limer
slag, gypsum and
hydrated lime
Deep Chemical
Mixing, etc.
Clay Mixing
Consolidation
TBS Method
Consolider System
TST System
Mini-max, M.R.
Mixer
ditto, for fixing metal ic
compounds
ditto, for making
impervious film
ditto, for organic soils
-------
Lime and its Variations
Quicklime
(1) Quicklime
Quicklime is one of the most popular and widely used agents in road
construction for sub-base and sub-grade stabilization. Recently, the Deep-
Lime-Mixing Method was developed (Okumura, et al., 1974) and has been used
for stabilization of the in-situ soft clayey layer in both marine and terres-
trial projects. In this case high activity quicklime is effective because of
its quick hydration and ease of mixing.
(2) Chemico Lime - 100
Chemico Lime-100 is quicklime with some additives and is produced by
Onoda Cement Co. Ltd. It is used for both road construction as Chemico Lizer
and for deep stabilization by means of lime piles as Chemico Pile.
(3) Semii Lime
Semii Lime consists mainly of quick lime and is used by Fujita Industry
Co. Ltd. for road construction or as lime piles.
Hydrated Lime
(1) Hydrated Lime
Hydrated lime is used as widely for road construction as quicklime. It
is possible to use it in the form of slurry for deep mixing stabilization.
(2) Road Lime
Road Lime consists mainly of hydrated lime with a small amount of water.
It is used by Nisshin Hodo Co. Ltd. for road construction.
Other Agents with Lime
(1) Slag and Lime
Slag (blast furnace slag) is not very effective in the pure state for
rapid soil stabilization. But with the aid of quick or hydrated lime, its
reactivity becomes greater and more rapid. In some cases the mixture of slag
and lime is more effective than pure lime. Several steel companies and
others have studied the effectiveness of the slag and lime mixtures.
(2) Slag Bacillus
Slag Bacillus consists mainly of slag and contains gypsum, hydrated lime
and other materials. In some cases, it is more effective than quicklime
(Kotani, et al., 1974).
(3) Gypsum and Lime
Gypsum in its pure state has almost no effect for soil stabilization.
But, with'the aid of lime, it may be more effective than pure lime.
(4) Hi-Tog
Hi-Tog is sludge ash from sewage with some hydrated lime. It is produced
by Hirose Steel Industry Co. Ltd. In some cases it is more effective than
pure hydrated lime. It also allows utilization of a waste product.
157
-------
Portland Cement and Us Variations
Portland Cement
(1) Portland Cement
Portland cement has been widely used 1n road construction as a "soil
cement" for solid states. Recently It has been used for solidifying soft
dredged soils (e.g., the Takenaka Sludge Treatment System), and also has been
tried mixed with deep 1n-s1tu clayey soils 1n the liquid state as Deep Chemi-
cal Mixing Method or DCMM method.
(2) Cement Mortar
In some cases, cement mortar (a slurry of cement and sand) 1s a more
effective stabilizer than cement slurry. It has been used for 1n-s1tu soil
stabilization as the Clay Mixing Consolidation method by Fudo Construction
Co. Ltd.
(3) Fuji Beton
Fuji Beton - FPC and Fuji Beton Toa -PC, -FK, -AL are compounds consist-
Ing of portland cement with various additives (organic and/or Inorganic).
They have been widely used for sludge treatment and for surface stabilization
of reclaimed land.
(4) Fudo Mix
Fudo Mix 1s a series of portland cement compounds with various kinds of
additives, and 1s used for surface treatment as the Consollder System.
Portland Cement with Other Agents
(1) Chemlco L1me -200, -400
Chemlco L1me -200 and -400 are portland cement with some amount of
hydrated Hme. They are used 1n liquid state for surface treatment as to
Mini-rnax method or M.R. method, and as the Mixer method 1n the solid state.
(2) Slag Cement (Portland Blast Furnace Slag Cement)
Slag cement Is, 1n some cases, more effective and economical than port-
land cement. It 1s also widely used 1n surface and deep stabilizations.
Asphalt 1s also used 1n sludge treatment, but 1t 1s not as popular as
11 me or portland cement.
Additives
There are several additives for portland cement which Improve Its stabll
1z1ng qualities. Denka HS-1 and -2 are added for rapid solidification.
Konseal makes films on the surface of organic soil grains 1n the same way as
Oanseal X5. To fix metallic compounds N1sso ALM and EB-CX are employed.
158
-------
GENERAL EFFECTS OF STABILIZATION WITH QUICKLIME
Variations which Depend on Soil Type
As shown In Figure 1, the unconflned compress1ve strengths, q , obtained
from laboratory mold tests 1n accordance with the authors' manual T.PHRI,
1975), vary widely depending on the kind of soil. Strength Increase due to
consolidation, being a mechanical stabilization, does not depend as much on
the kind of soil. The c /p ranges from 1/3 to 1/4. Thus, the reactivity of
Hme treated soil depends mainly on the chemical and mineraloglcal properties
of the soils, and therefore has a variation greater than 5 times that shown
1n Figure 1. In general the effectiveness of Hme or cement on organic so1U
1s less.
20
11
E
o
V.
o>
10
LIME CON'irriT 10%
NAUJRAL WATER CONTENT
MIXING TIME lOrnin.
YOKOHAMA CLAY
(Wi-102.5%)
HGf.'MOKU MARPJE
CLAY(Wi»l20%)
KU.1E O'LT < CLAY (Wi = C0%)
KURIHAMA CLAY
(Wi-114%)
NARUO CLAY
i = 90.2%)
KOBE CLAY
HAMEOA RECLAIMED SOIL
(Wi-170%)
37 21 60
CURING TIME (DAYS)
Figure 1. L1me reactivity of Japanese marine clays.
159
-------
Effect of Time and Temperature
Strength increase with time, of lime treated soil, is similar to that of
cement concrete and as shown in Figure 1, is roughly proportional to the
logarithm of time. High temperature results in a more rapid reaction between
the soil and the lime leading to a quick increase in strength. The final
strength reached does not necessarily depend on the temperature.
Effect of Initial Water Content
Figure 2 shows the effect of the initial water content of the treated
soil on the lime reactivity. The quicklime content relative to the solid
weight of the soil (%) is represented as a , and T is the curing time (days).
The reactivity is maximum at an initial content near the "liquid limit," w. ,
or a little less. For higher water content the reactivity is greater than
that for lower values of water content, and therefore the effectiveness for
stabilizing dredged material with high water content may still be consider-
able.
30
o
\
o>
ZJ
cr
20
10
0
HOMMGKU MARINE
CLAY
WL= 95 %
WP 45 %
50 100 150
INITIAL WATER CONTENT (%)
200
Figure 2. Changes in lime reactivity with initial water content.
Effect of Lime Content
The lime reactivity is roughly proportional to the lime content for
small amounts of lime. However, it is not necessarily true that more lime
results in more reactivity. In the extreme case 100% quicklime becomes 100%
hydrated lime, which is a rather soft material. In the practical range of
lime content, which is up to 15 or 20%, this trend of diminishing effective-
ness sometimes exists.
160
-------
Effect of Grain Size
Contrary to common sense, lime reactivity is not maximum in pure clay,
but is higher in soils with some sand content (Yanase, 1968). For pure sand
the lime reactivity is less.
Consolidation Characteristics of Lime Treated Soils
Figure 3 shows an example of void ratio, e, vs. consolidation pressure,
p, for a soil-lime mixture cured for 3 weeks. The compressability of treated
soil is much less than that of untreated soil up to the consolidation yield
stress, p . It means that the lime treated soil is more resistant to settling
than the untreated. The consolidation yield stress or the preconsolidation
pressure of the treated soil is proportional to the unconfined compressive
strength, q , as shown in Figure 4. Therefore, the greater the strength
increase, tne heavier the allowable load is before settling begins.
60
e
3,0
2.0
1,0
I I I I
TREATED SOIL
UNTREATED SOIL
I
I
I
50
40
CM
30
o>
3
CT
20
10
i I r
HONMOKU MARINE CLAY
KOBE CLAY
KURESILTYCLAY
O
10
rl 10° 10' I02
P (kg/cm2)
Figure 3. Typical void ratio vs
consolidation pressure curve.
20 40
Py (kg/cm2)
60
Figure 4. Consolidation yield stress vs
unconfined compressive strength.
161
-------
Figure 5 shows a relationship between the ratio of the coefficient of
volume compressability of treated soils, m , to that of remolded and untreated
soils, m , and the mean relative consolidation pressure to the yield stress,
p/p . Tne relative compressability, mv/m is less than 10% for a mean
relative consolidation pressure less than 0.3, and is about 1.5 for an m
greater than 1.0. vr
Relationship between the relative coefficient of consolidation, c /c ,
and the mean relative consolidation pressure is shown in Figure 6. The' rate
of consolidation of treated soils is more than 10 times greater when compared
with that of the remolded and untreated soils in the range of relative consol-
idation pressures less than 1.0 (Okumura, Terahsi and Yoshida, 1974).
COMPARISON OF THE STABILIZING EFFECTS OF VARIOUS
CHEMICAL AGENTS ON SOME SOFT CLAYEY SOILS
The author and his colleagues carried out a series of laboratory tests
to compare stabilizing effects of various chemical agents. The testing
method was in accordance with the author's manual (PHRI, 1975), and the
stabilizing effect is evaluated by employing the unconfined compression test.
Physical and chemical properties of the soils used in the test are
listed in Table 2. Two of the soils are organic and the other two are
inorganic. Chemical agents mixed with these soils are two of the quicklime
type, two of the portland cement type, plus three additives used with the
Portland cement.
TABLE 2. PHYSICAL AND CHEMICAL PROPERTIES OF TESTED SOILS
Soil
Property K M
Specific gravity of solid, GS
Liquid limit, w. , %
Plastic limit, w , %
Soil classification
PH
Ignition loss, %
Organic carbon, mg/g
Sulfide, S mg/1 g solid
Total Hg, mg/kg
Oil content, mg/kg
COD, 02 mg/1 g solid
2.66
91.8
40.9
clay
8.1
7.9
10.5
0.26
190
10.0
2.71
89.9
27.9
silty clay
8.4
9.7
8.5
0.67
0.36
2120
18.7
2.44
145.4
48.2
sandy silt
7.8
19.2
29.5
3.31
14500
46.7
2.52
137.0
55.8
clay
8.1
20.0
23.5
19.16
4.66
19400
86.3
162
-------
HONMOKU MARINE CLAY
KOBE CLAY
o.i
0.0!
P/Py
Figure 5. Coefficient of volume compressability
of lime treated soils.
loot
° HONMOKU MARINE CLAY
KOBE CLAY
P/Py
Figure 6.
Coefficient of consolidation of lime
treated soils.
-------
Test conditions were as follows:
Initial water content, % --- 100, 200
Agent content in weight relative to the solid weight, % — 5, 15
Curing time, days, — 3, 7, 21
Curing temperature, — 20°C
Test results are compared in Figures 7, 8 and 9 in the form of frequency
distributions on a logarithmic scale, where the ordinate is the frequency and
the abscissa is the logarithm of the ratio between the two unconfined compres-
sive strengths of soils. These soils are treated under the same conditions
with two different stabilizing agents.
Figure 7 compares the stabilizing effect of Portland cement and quick-
lime. There is no significant difference between organic and inorganic
soils. On the average, portland cement is more effective by 34%, although
the variation is higher in the test cases.
77
Mean 0-1254
(q,/qF1-335)
-08 -06 -04 -02 0 0-2 04 0-6 0-8 10 12
log qp/qq
Figure 7. Comparison of stabilizing effect between portland
cement and quick lime.
Figure 8 compares the stabilizing effect of portland cement with additive
and pure portland cement. In these cases the additive together with portland
cement is on the average more effective by 25%.
164
-------
••••
r^
/;
/
u*rt^.
CO >
ch u
L
c
O
C D
~ O
O »-
CO lJ-
O
'c
TJ
cn
L—
O
//y?
^v>
^X>
i
30
25
20
15
Y/4
fa*
-fy
Mean 00975
(q/q,= 252)
1
Figure 8.
-04-0-2 0 02 0-4 06 08
log q,/q,
Comparison of stabilizing effect between
some cement type agent and port! and cement.
Figure 9 shows the stabilizing effect of another additive on organic
soil. In these particular cases the additive is less effective by 14%, on
the average.
These comparisons show rather wide variation. As previously mentioned,
the stabilizing effect of a particular agent depends on both soil and environ-
mental conditions. Figure 10 compares portland cement and quicklime again.
In this, figure some reliable data other than the above are included. On the
average, portland cement is slightly more effective by 12% than quicklime,
but with considerable variation among the samples.
Figure 11 compares the stabilizing effect of hydrated lime and quicklime.
In this case, it is rather clear that hydrated lime is less effective by
about 40%.
165
-------
Mean -0-0636
(q,/0=0-865)
cr>
20
15
I
o
CO
en
L_
O
c
o
CO
o
c
rfl
01
-1-0 -08 -06 -0-4 -02 0 02 OA
log
Figure 9. Stabilizing effect of some additive for
organic soil .
o
en
en
i_
o
c
o
in
o
c
0}
en
i_
O
u
C
0»
D
CT
30
20
Mean
vs/-.',
-08 -0-6 -0 A -02 0 0-2 0-A 06
log qp/qq
10 1-2
Figure 10. Comparison of stabilizing effect
between port!and cement and quick
lime.
-------
o
-------
The commercial cost of some special additives makes them impractical,
even though they add some degree of increased strength in the stabilization.
It is much more reasonable, in practice, to increase the content of the
simple stabilizing agents such as quicklime, hydrated lime, Portland cement,
and slag cement.
REFERENCES
1) Kotani, S. et al. (1974): On the Slag Type Agent for Soil Stabilization,
Proc. Japanese Soc. Soil Mech. and Foundation Eng., Vol. 22, No. 5, pp.
75-80 (in Japanese)
2) PHRI, Soil Stabilization Laboratory (1975): Laboratory Testing Manual--
Deep-Lime-Mixing Method for Soil Stabilization —, 13 p. (in Japanese)
3) Okumura, T., Terashi, M. and Yoshida, T. (1974): Studies on the Engineer-
ing Characteristics of Lime Treated Soils (1st Rept.), Proc. 9th Annual
Meeting of Japanese Soc. of Soil Mech. and Foundation Eng., No. 225, pp.
893-896 (in Japanese)
4) Okumura, T., Terashi, M. Mitsumoto, T., Yoshida, T. and Watanabe, M.
(1974): Deep-Lime-Mixing Method for Soil Stabilization (3rd Rept.), Rept.
of PHRI, Vol. 13, No. 2, pp. 3-44 (in Japanese)
5) Okumura, T. and Terashi, M. (1975): Deep-Lime-Mixing Method of Stabiliza-
tion for Marine Clays, Proc. 5th Asian Regional Conf. on Soil Mech. and
Foundation Eng. (Bangalore, India), Vol. 1, pp. 69-75
6) Yanase, S. (1968): Stabilization of Alluvial Clays with Quick Lime (1st
Rept.) Rept. of PHRI, Vol. 7, No. 4,. pp. 85-132 (in Japanese)
168
-------
A METHOD FOR DISPOSING OF WASTE WATER
AT DREDGED MATERIAL RECLAMATION SITES
E. Satoh*
Japan Dredging and Reclamation Engineering
ABSTRACT
This report introduces a method for disposing of
the waste water that continuously flows in huge volumes
from dredged materials as they are removed, transported
and dumped in reclamation sites. This method is already
being put into practice in Japan. It is characterized
by its attempt to reduce the quantity of flocculants
and to establish a stable and reliable system for
disposal of large volumes of waste water by taking
advantage of the natural conditions at the site to be
reclaimed.
INTRODUCTION
Reclamation using dredged materials requires disposal of the waste water
that flows from the reclaimed land. When the dredged materials used for
reclamation are polluted, strict controls have to be placed on the toxic
compounds; even if the materials are not polluted, it would still be desirable
to reduce turbidity to the lowest possible level. The salient point for
disposal of waste water derived from reclamation using dredged materials is
that the disposal has to be conducted under stable conditions while continu-
ously handling a huge volume of water.
The conventional method of solving this problem focuses on purification
of waste water by means of flocculants. This method is quite expensive and
also causes concern about the toxic effects of the flocculants. These defects
in the conventional method have compelled us to study and find ways of
lowering the turbidity to a required level while reducing the quantity of
flocculants.
PRESENT STATE OF WASTE WATER TECHNOLOGY
Figure 1 is a flow chart that shows the basic processes of dredging
seabed sediments and the use of dredged materials in later reclamation works.
These processes are actually in practice in Japan. The materials dredged
from the seabed are transported to the reclamation site by a pipeline system,
or by other methods. Figure 1-1 represents a method that makes good use of
the reclamation area itself as a condensation pond for reclaimed materials,
and at the same time, as a clarification pond for waste water. This method
* Toranomon-Kotohirakaikan Bldg. 1 Shiba-Kotohira-cho, Minato-ku, Tokyo 105, Japan
169
-------
1) Using the reclaimed land as a condensing and clarifying tank
I ^inland)
bottom
sediments
reclamation
(civil engineering dehydration
surface concreting overlay
method, and so on)
barge (at seajfcinjand)
pipe
conveyer L t^ar,,,-. ^discharge)
-^atioy
2) Installing separate condensing tank and clarifying tanks (mechanical
dehydration)
inland disposal
bottom
sediments
(barge
)pipe
[conveyer |
b) disposal on board
j—*•( inland)
bottom
sediments
'barge
truck
conveyer
pipe
—^(discharge)
Figure 1. Basic Disposal Flows of Reclamation
170
(pipe
^conveyor
(truck
reclama-
tion
(at sea,
inland)
\tation I
(pipe
-------
is called the "Civil Engineering Dehydration System" because it makes full
and effective use of the natural conditions.
By comparison, Figure 1-2 shows the method in which dehydration is done
by installing separate condensation and purification tanks. The location
where the mechanical dehydration equipment is to be installed must be chosen
in each case with consideration of, and in conformity to, the actual con-
ditions of dredging and reclamation. The above mentioned equipment is in
some cases installed on shore, but in most cases is ship board. Generally
speaking, the method shown in Figure 1-1 is useful for comparatively large
scale work, while the one shown in Figure 1-2 is useful for small scale work.
The waste water produced by dehydration is duly dreated and then drained
away. So far in Japan, the waste water from reclamation of unpolluted dredged
materials has been returned directly to the sea without treatment of any
kind.
The turbidity of the waste water in question varies in proportion to the
scale of reclamation work, the volume of waste water itself, the duration of
work, and other conditions. Some records of turbidity obtained through
projects completed in the past are shown below (1).
During the initial phase of reclamation 75 - 100 ppm
middle " 3,000 - 5,000 ppm
final " 15,000 ppm
Under the present laws and regulations there are no special provisions
to restrict the quality of waste water derived from reclamation using dredged
materials which are not polluted. However, it is desirable to attain and
maintain turbidity at the lowest possible level in consideration of environ-
mental effects on the natural stream water and-the sea surrounding the reclam-
ation site. For this purpose, the values cited in Table 1 are largely com-
piled as a "waste water turbidity standard" and constitute a target to be
attained.
Additionally it is quite possible that measures will be undertaken in
the future to control waste water disposal for all types of reclamation
works.
At present, waste water quality is stringently controlled and restricted
in all cases of reclamation using dredged seabed materials which contain
toxic heavy metals, organic matter, and oily substances.
The flocculation acceleration method, recently implemented for waste
water disposal, consists of simultaneous utilization of both poly-acrylic
amide and inorganic flocculants. In order to prevent diffusion of turbid
water, physical barriers are in common use.
In cases where waste water quality is highly restricted, rapid filtration
equipment is often utilized.
171
-------
TABLE 1. STANDARDS FOR WASTE WATER DERIVED FROM RECLAMATION
Items
Allowable Bounds
cadmium and its compounds
organic phosphorus
compounds
chromium and its compounds
hexa-chromium compounds
arsenic and its compounds
mercury and alkyl mercury
and its other compounds
alkyl mercury
hydrogen ion concentration
(pH)
biochemical oxygen demand
(BOD)
chemical oxygen demand
(COD)
suspended solids
(SS)
0.1 mg/1
1.0 mg/1
1.0 mg/1
0.5 mg/1
0.5 mg/1
none detected
none detected
5.0 - 9.0
160 mg/1
mean 120 mg/1 during daytime
160 mg/1
mean 120 mg/1 during daytime
200 ppm
mean 200 ppm during daytime
(notes)
(1) "mean concentration during daytime": average polluted conditions
(2) the Environmental Authority directs that waste water may be discharged
at 1/2 to 1/4 of the above levels
172
-------
Figures 2, 3 and 4 are graphic explanations of the disposal methods for
polluted seabed materials. These methods have actually been tried and
carried out in Japan. In particular, Figure 2 represents experimental work
conducted in the Port of Yokkaichi Municipality and Mie-prefecture, for
disposal and removal of bottom soil in waters of the port area. The sediment
was .polluted with mercury and oily substances. In this experimental work the
polVuted muddy bottom soil was dredged by suction dredges and then trans-
pdrte^:b^;b4rges to the reclamation site. There, the muddy soil settled
leaving 'ttie:'upper water relatively clear. This was disposed of using rapid
filtration equipment. This method is like the one shown in Figure 1. A
full scale project for removal and disposal of polluted soil from the Yok-
kaichi Municipality port is scheduled to begin with a total soil volume of
2,200,000 m3 to be dredged in the latter half of 1976. Completion will take
approximately 2 years.
Figure 3 shows the dredging work at Lake Biwa, Shiga prefecture, which
involves disposal of pulp sludge containing PCB. This is an example of a
relatively small scale project. In this case, dredged sludge was dehydrated
by a filter type dehydrator installed in the on-site plant. The dehydrated
sludge was solidified by means of cement while the waste water was purified
by flocculants and then drained away. This method corresponds to Figure 1-
2a.
Figure 4 shows a dredging project now in progress in the Seto Inland Sea
which is handling seabed soils polluted by organic matter. This work is
being undertaken as a measure to minimize the effects of the red tide. The
muddy polluted soil, after being dredged, is brought to the disposal vessel
which is moored in the vicinity of the dredging area. Thickening tanks,
dehydrators and quick filtration equipment are all installed aboard the
disposal vessel. The polluted soil, once dehydrated, is transported ashore
and then solidified by cement. The filtered waste water is drained into the
sea. This method is shown in Figure l-2b.
The standards of waste water quality set by regulation are shown below.
Fig. 2: Yokkaichi Harbor
SS 30 ppm
Normal-hexane soluble substances 2 ppm
(daily average)
Fig. 3: Lake Biwa
SS 40 ppm
Fig. 4: Seto Inland Sea
SS 10 ppm
CIVIL ENGINEERING MANAGEMENT OF WASTE WATER
Until recently in Japan, dredging and reclamation of land required that
the reclamation site be enclosed by a simple wooden stockade from which all
the waste water from the spoils drained through spillways. Muddy soil and
water which spilled from the wooden stockade caused turbid water to spread.
173
-------
Dredging pump for bottom
sediments - high density „
suction with gas removal device
Bottom Sediments
cxjcxxxxYYxrr x xT
Oil fence for prevention
of diffusion of soluble
oil portion
Special suction equip
for prevention of ami
>ment
fusion
of muddiness, prevention of
gas diffusion and promotion
of collecting accuracy
Unloading Pontoon
_XZ_
Barge for the transportation of
bottom sediments with closed
deodorizing device
Filteration Equipment
Sedimentation Pond
xx
.L.
Figure 2. An example of reclamation using "Civil Engineering Dehydration."
-------
Deodorant chemicals
Polymer
coagulants
Hardening chemicals
01
I. Dredge for bottom sediments
2. Floating line
3. Inland pipe line
4. Rotary screen
5. Belt conveyer
6. Cushion lank
7. Submergible sand pump
8. Proportional filter
9. Belt conveyer
10. Mixer
II. Warehouse
12. Dump truck
Figure 3. An example of reclamation using mechanical dehydration with inland disposal
-------
en
dredge
A.
• /
bottom sediment
disposal pontoon
sand carrier with
grab bucket
A
r— 1 ! .. . , dehydration
clarifier [j thickener '
(TP
discharge
belt conveyor
transportation by
dump truck
sand carrier with
grab bucket
disposal
Figure 4. Another example of reclamation using mechanical dehydration and inland disposal.
-------
Because of the large volumes of silt and clay which were released, the local
inhabitants and the general public complained about this method of reclama-
tion.
Therefore, in compliance with public opinion, and prior to the commence-
ment of a project, bulkheads are usually erected to enclose most of the
reclamation sites. With this technique almost the entire volume of waste
water brought into the area is spilled outside of the bulkheads through
spillways and consequently drains to the adjacent water. Therefore, the
quality of the waste water flowing through the spillways has become the focus
of a water quality problem.
Japanese reclamation projects which make use of quality non-polluted
material are done with suction dredges equipped with dredging pumps of around
4,000 ps. This means that, including rainfall, waste water would flow through
the spillways at an average rate of 6,000-8,000 m3 per hour. Dredging of
polluted muddy sediments that contain toxic substances require waste water
disposal at the rate of 1,000-2,000 m3 per hour. The point is that the waste
water arising from reclamation using dredged materials is a huge volume that
has to be dealt with constantly.
In using the bulkhead method it is easy to provide a large settling pond
inside the enclosure in the initial phase of the work. However, the pond
would be reduced in capacity as the work progressed and would lead to in-
creased waste water turbidity over the spillways. Rainfall would also in-
fluence the volume of the waste water at the same time. Thus, the fluctua-
tion in both waste water turbidity and volume constitutes an additional
characteristic of the "Civil Engineering Dehydration Method."
Grading of the soil to be dredged is also related to waste water quality.
The greater the proportion of minute silt and clay in the dredged material
the more difficult the disposal work will be.
In actuality, this waste water disposal method has been applied to
reclamation work using normal quality soils and used only in cases where the
soils were of soft quality and mostly composed of clay and silt. In these
cases the waste water contained a substantial volume of clay.
There are two particular methods which have been applied in these
cases. The first is to inject poly-acrylic amide inside the pipe that conveys
the dredged soil to the reclamation area with subsequent flocculation and
separation of soil grades occurring over the entire spoil area. The second
method is the same as the preceding method up to the process of conveying the
dredged soil. Once the dredged soil arrives in the reclamation area it is
placed in a smaller enclosure within the larger reclamation area. This is
where it is concentrated by flocculation and separation processes.
The waste water disposal method which depends wholly upon poly-acrylic
amide is open to question. The doubt arises in the application of the floc-
culants. The method as explained above requires instantaneous flocculation
and separation. The'direct application of the chemicals to highly turbid
water allows insufficient mixing between the chemicals and the muddy water
177
-------
unless huge doses of poly-acrylic amide are used. Some actual cases report
an average use ranging from 10 to several hundred grams of poly-acrylic amide
per 1000 kg of reclaimed soil (dry weight basis). Therefore, these present
methods not only subject the area to the toxic effects of poly-acrylic amide,
but also are not economical.
In cases where the waste water density and its volume fluctuate, the
dose of chemical is figured by assuming the worst possible conditions. This
sometimes compels an unnecessary quantity of chemicals to be used needlessly.
In cases where polluted muddy seabed soil is handled, stringent water quality
standards often require an excessive application of flocculants.
Thus, while the original motivation for experimenting with new methods
for waste water disposal in reclamation is undoubtedly an attempt to minimize
turbidity it is, at the same time, aimed at reducing the consumption of poly-
acrylic amide. With this point of view in mind a group of engineers, under
the leadership of the author, have conducted the following studies and inves-
tigations.
Development of a Method of Settling and Consolidation of Dredged Materials
in an Enclosed Reclamation Area Without Using Flocculants
This method consists of two steps. The first step is to utilize effec-
tively the water-bearing area of the reclamation site for a sedimentation
pond. There is a limited water volume in the reclaimed area, especially in
the final stages of reclamation. There are also many complex currents in the
sedimentation pond, e.g. surface currents, short cut flows and wind waves.
In addition, the settling time of minute particles is considerable. Because
of these problems the capacity of a pond for sedimentation and consolidation
of the dredged material is limited. This makes it very difficult to estimate
the capacity of a sedimentation pond. In spite of these difficulties, we
consider it worthwhile to try to utilize the full capacity of any sedimenta-
tion pond. In order to utilize the reclaimed area for primary sedimentation
it is important to consider plants growing in the reclaimed area (such as
reeds), the plan for reclamation procedures, and the plan of discharge
pipelines. This first step is only to decrease the turbidity of waste water.
The second step of this study is intended to accelerate the settling and
precipitation of the particles in the waste water. For this reason, an
attempt was made to take advantage of the location where the waste water was
to be discharged from the reclaimed area as a second sedimentation pond.
This water collecting sedimentation pond is based on our idea to settle and
precipitate minute particles without using flocculants.
This sedimentation pond, which we call the "Trough Spillway," is dis-
cussed later in this report along with an explanation of its structural and
test results. This sedimentation pond is aimed at promoting settling and
precipitation without using electric power or mechanical devices, and is also
aimed at making good use of natural conditions. Because of this we call this
technique the "Waste Water Disposal Applied Civil Engineering Method" to
distinguish it from the conventional "Civil Engineering Dehydration Method."
178
-------
A Method of Flocculatlon and Separation of Mass-Waste Water Using Temporary
Rectifying Sedimentation Ponds in Reclaimed Areas In Combination with the
Waste Water Controlling System
When reclamation work uses dredged bottom sediments containing noxious
materials, there are severe restrictions on waste water turbidity and quality.
We often cannot attain the standard using only natural sedimentation and
separation. In this case the use of flocculants is necessary. The temporary
rectifying sedimentation pond, located in the reclaimed area in combination
with the controlling system, is a rational system to continuously dispose of
a huge volume of waste water.
The waste water flowing though the reclaimed area is introduced into a
sedimentaion pond of required volume. There chemicals are added to the water
and its currents are "rectified" by means of baffle boards in the pond.
Actual instances where this system was applied are discussed in the following
section. The rectifying sedimentation pond system is not effective without
being combined with a waste water control system as discussed above. Properly
done, a stable and economical mass waste water disposal system is realized by
adjusting the amount or chemicals in proportion to the water quality and
quantity flowing into the rectifying sedimentation pond. By controlling the
discharge rate and chemical dose, water quality is precisely adjusted to meet
the standards.
AN EXAMPLE OF THE RECTIFYING SEDIMENTATION POND METHOD
Bottom sediments containing cadmium in Shimonoseki City, Yamaguchi
Prefecture, were dredged from 1973 to 1974. Regulation of the waste water
standards are as follows:
SS less than 20 ppm
Cadmium less than 0.005 mg/1
pH 5.8 to 8.6
Structure
Figures 5 and 6 show the general plan of the work s.ite and a side view
of the rectifying sedimentation pond. Dredged slurry is transported via
pipeline to the reclamation area, which is enclosed by a watertight structure.
The disposal point of the dredged slurry is the place farthest from the
reclamation area behind the fence (see Figure 5). Waste water is conducted
into the rectifying sedimentation pond. Poly-acrylic amide is added and the
pH value is adjusted using chemicals, such as hydrochloric acid, which are
added to the waste water at the entrance of the sedimentation pond. Steel
"rectifying plates" are baffles set into the sedimentation pond to regulate
currents in the waste water. The seepage ratio of the rectifying plate is
3.1%. The quantity of waste water is 270 m3/hr, the mean velocity of the
rectifying current is 3 mm/sec, and the residence time is around 10 hours.
The volume of the flocculants used is 0.9 g/m3 and 7 cc of 30% hydrochloric
acid is used as the neutralization chemical.
179
-------
Second sedimentation pond
10 m
pH adjusting
equipment
Water quality control room
Rectifying
sedimentation pond
Equipment for addition
of flocculant
T£
^Outfall
Di
+*
^s
•charge outlet
Dredged area
j? Dredge
I/
*^^
;
Figure 5. Rectifying sedimentation pond as used with
dredged materials disposal for land recla-
mation.
I recTainiedr'
[are a \
o o
addition of chemicals
rectifying. plate_
primary sedimentation
pond
m -
±-
77 m
130 m
submerged sheeting board_
rectifying plate
V^
second sedimen-
tation pond
i
50 m
Figure 6. Side view of rectifying sedimentation pond,
180
-------
The sedimentation pond is a two-stage structure; the partition wall, or
wier, is of the "submerged sheeting board" type. Figure 7 shows the control
system for the waste water and Figure 8 the flow chart the for the pH adjust-
ing system.
Test Results
In order to examine the effectiveness of the rectifying sedimentation
pond, SS values of the waste water were tested constantly at the pond en-
trance, and at 3 meters and 80 meters from the entrance of the pond. Table 2
shows an example of the test results.
Evaluation
As shown in Table 2, the average SS value at the sedimentation pond
entrance is 26.5 ppm, while the average SS value of the waste water passing
through the sedimentation pond is 9.3 ppm. Generally, when the SS value is
small, the components of suspended solids almost always consist of minute
particles which are difficult to settle and precipitate. For the rectifying
sedimentation pond, however, the removal ratio of 65% achieves the SS values
desired.
TABLE 2. SUSPENDED SOLIDS IN THE RECTIFYING SEDIMENTATION POND
Average during 70 days Average during 11 days
(pneuma pump) (centrifugal pump)
Measuring
Point
1
2
3
4
Measurement
(ppm)
Place
at flowing
entrance
3m downstream
from flowing
entrance
80m downstream
from flowing
entrance
130m downstream
from flowing
entrance
Turbidity
(ppm)
25.2
18.5
15.1
12.9
Removal
SS Ratio
(«)
14.1
10.7 26.6
8.9 13.5
7.8 8.7
48.8
Turbidity
(ppm)
49.6
31.7
20.7
15.8
Removal
SS Ratio
(%)
26.5
17.4 36.1
11.8 22.3
9.3 9.9
68.8
Figure 9 shows that in the rectifying sedimentation pond almost all the
soil is accumulated in the first area. This is the whole point of the two-
stage sedimentation1 pond.
181
-------
[dredging
removal, inspection of cadmium
removal of cadmium, precip.(lime)
| flow into the reclaimed area |
methoc
1 of reducing
turbidity
>
f
silt fence before the
discharge outlet
J,
silt fence in the entrance
of the sedimentation pond
| rectify ng sedimen-
1 tation pond
| <
I c
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1
1
1
1 _
I f
I
L -
1
r 1
iddition of f locculants '
(Panfloc) !
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i
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1
, \
low through the '
sedimentation pond ;
J
\
PH adjusting \
equipment /
equipment for
the addition of H
MAI f tr/i \ • •*/>• t\r\r\ ^_
neuTraiizaTion •—
chemicals
_J L_, .. ,,lL.^
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)pen||closed|
wuier quuiuy c<
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turbidity v
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I alarm | br:
H open r
1_i __ _ ji
closedl
submersible
pump
^^"j* i 1
~H discharge |
Figure 7. Waste water controlling system in rectifying sedimentation pona
182
-------
neutralizing
tank and pump
additional L
equipment for
polyocrylicomid
ON|-
OFFH
water quality
controllng room
pH meler
No. I
Lf-|YES
HNO
pH meter
N
uipment
addition
reclaimed
area
pH meter
No. 2
iNOf
IYES
alarm
siren, red lamp
to reclaimed
area
pH meter
No. 2
I
submergible
ump
p
J
exhaust
valve
closed]
[discharge)
Figure 8. pH adjustment flow in rectifying sedimentation pond.
•primary sedimentation pond-
(80.0 M)
equipment for addition
M
secondary sedimentation
t pond *•
(50.0 M)
weir
bottom sediments
discharge
100
130m
'distance from entrance of flow
Figure 9. Soil accumulation conditions in rectifying sedimentation pond,
183
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EXAMPLE OF THE TROUGH SPILLWAY METHOD IN USE
The trough spillway method was developed through fundamental experiments.
It has been applied in the reclamation projects in Kumamoto Prefecture in
1975 and 1976. Here, the materials to be reclaimed were not polluted.
However, the sediment contained large amounts of silty and clayey materials
which would cause turbidity. This is why the spillway method was applied at
that time. The quantity of water to be disposed of was 5000 m3/hr. No
flocculants were applied in this work.
Structure of Trough Spillway Method
Figure 10 shows the structure of the trough spillway. This is built at
the outlet portion of the waste water sedimentation pond in the reclamation
area. The spillway consists of the following sections:
Submerged sheeting boards : 2
Curtain walls inside boards : 3
Horizontal filters inside walls : 4
Trough floating on the water : 1
A 10 cm thick flow of waste water passes over the sheeting board which
acts as a wier. This overflow collects the surface water. Then, in the
second stage, the waste water which overflows into the inside of the boards
is changed to a vertical ascent current within the curtain walls. The average
ascending velocity of this vertical current is 3 mm/sec, which is equivalent
to the natural settling velocity of 65 ym diameter soil particles. In the
third stage the ascending waste water passes through the horizontal filters
which have an effect of stopping the upwelling of soil particles. The appar-
ent density difference can be seen on both sides of the horizontal filters.
In the last stage, the waste water is discharged to open water outside of the
reclamation area via a 1,000 m long trough with an overflow depth of about 6
mm. To maintain efficient sedimentation the materials which accumulated on
the bottom of the trough spillway were transported to the reclamation area
with a submersible pump. Figure 11 shows the installation of the trough
spillway structure.
Test Results of the Trough Spillway Method
To evaluate the trough spillway method turbidity values for the waste
water were sampled in the overflow of the submerged sheeting board and the
discharged water from the trough spillway. These are shown in Table 3. On
the whole, turbidity removal efficiency is high for the waste water flowing
into the trough spillway system. Figure 12 shows some of the records obtained
by the continuous turbidity recorder. Fluctuations of turbidity values for
the inlet waste water are large, while fluctuations in turbidity for the
waste water outlet from the trough spillway are small. Figure 13 shows the
particle size distributions for mud sampled at several points. This shows
that the percentage of minute particles increases from the first to the last
stages.
184
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00
en
n
n
u
u
li-+-
n
®
!
I'
C5
11
' i
•'-JJ
i'
•
Figure 10. Illustration of the structure of the trough spillway.
trough
submerged sheeting
board
curtain wall
horizontal filter
-------
screw jack for
fine adjusting level
bearing I-beam
for trough
trough device for collecting
clarified surface water
water, collecting channel
>uoyancy adjusting gate
and water level sensor
u
11
11
11
11
^bearing pipe
~i
Figure 11. Structure with set troughs.
-------
12
II
10
8
when
discharging
RANGE 0~200ppm
when flowing in
-200-
Figure 12. Turbidity record in the
entrance and exit of trough spillway.
-------
CO
00
I I I I I I I I 1 I I I I I | I I |
flowing over troughs-*^- ^*
i I i i i i 11
bottom of
—sedimenta- i
tion pond ^
.dredged materials
I | I I I I I I I I I I I Mill
i I I I I I II
100
o
£^
3
JQ
80 .-§
60*
N
55
2o°:
o
o
o
0.001
0.01
gram size
O.I
(mm)
1.0
CLAY I
SILT
I
SAND
TCOBBLE
0.005
O074
2.0
Figure 13. Grain size distributions at respective points of the trough spillway.
-------
TABLE 3. TURBIDITY AT THE ENTRANCE AND EXIT OF THE TROUGH SPILLWAY
Measuring
date
February
26th, 1976
February
27th, 1976
February
28th, 1976
March
1st, 1976
March
2nd, 1976
March
3rd, 1976
March
4th, 1976
March
5th, 1976
March
6th, 1976
March
7th, 1976
March
8th, 1976
March
9th, 1976
March
10th, 1976
March
llth, 1976
March
12th, 1976
March
13th, 1976
March
14th, 1976
March
15th, 1976
March
16th, 1976
March
17th, 1976
average
Turbidity values
(average during
in- flow
water
35
33
70
170
42
54
25
32
20
22
34
16
24
16
43
35
22
22
12
25
36.5
daytime)
Discharged
water
25
20
60
150
35
38
12
23
13
20
29
15
10
15
35
26
15
13
10
13
28.9
Effect
Reduced
turbidity
10
13
10
20
7
16
13
9
7
2
5
1
14
1
8
9
7
9
2
12
7.6
of usage
Removal
efficiency
28.6%
39.4
14.3
11.8
16.7
29.6
52.0
28.1
35.0
9.1
41.2
6.3
58.3
6.2
18.6
25.7
31.8
40.9
16.7
48.0
20.8
189
-------
Evaluation of the Trough Spillway Method
For waste water from reclamation areas consisting of more than 60% silty
and clayey materials, this method could reduce the turbidity values to less
than 30 ppm on the average, without using flocculants, and could operate
continuously treating waste water at the rate of 5,000 m3/hr. For land
reclamation using polluted materials it would be difficult to satisfy the
increased turbidity restrictions with this method without additional equip-
ment. But this trough spillway method will be effective in combination with
a rectifying sedimentation pond employing a small amount of flocculants.
AUTHOR'S POSTSCRIPT
The motivating conception from which the present report originated is an
attempt to make the most effective use of all the conditions that nature
offers us in the area of waste water disposal. It is important that efforts
should be made without interruption in order to reduce the environmental
impact that reclamation projects may cause, regardless of whether or not the
soil to be reclaimed is polluted. The present report represents a small part
of these efforts.
REFERENCE
Public Nuisance Countermeasuring Committee's Survey in 1974 Japan Dredging
and Reclamation Engineering Association.
190
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LEGAL AND ADMINISTRATIVE ASPECTS
OF BOTTOM SEDIMENT MANAGEMENT
by
A. F. Bartsch, Director
Corvallis Environmental Research Laboratory
U. S. Environmental Protection Agency
200 S. W. 35th Street
Corvallis, Oregon 97330
INTRODUCTION
Today there is great interest in toxic substances in bottom sediments,
mostly as a result of recent costly episodes in the United States and else-
where in the world. Some episodes have tragically affected human health and
welfare. Obviously, because we are confronted by these problems in both our
countries, we have a kinship of concern and a united desire to deal with
them in the most effective manner. To do this certainly was the intent of
signatories to the May 1974 Ministerial Agreement between our countries.
In the United States we are concerned about toxic sediments in both
marine and freshwaters. The marine coastlines are long and diverse, ranging
from the tropics of Florida to the arctic coast of Alaska. Here and there,
estuaries and bays mark areas that are susceptible to sediment deposition.
There are more than 100,000 lakes ranging in size from several hectares to
Lake Superior with 84,131 square kilometers, and all accumulate sediments to
some extent. Major river systems have more than 418,340 kilometers of
streams, many with impoundments and other segments of low velocity where
sediments collect.
Sediments, and whatever toxic chemicals they may carry, enter these
waters from several sources. Sediments already in place may acquire toxic
substances through waste discharges or accidental spills. Apart from the
sediments that come from soil erosion, principal sediments are materials
discharged through pipes and materials dumped from ships and barges. Cir-
cumstances may cause some of them to become dredged spoils at a later time.
Recipient aquatic environments reflect in their accumulated sediments
not only the character of the immediate surroundings but also activities
taking place on the watersheds of streams that flow into them. While there
is no question that even treated municipal and industrial wastes often
contribute to the toxic sediments in these various settings, the materials
of main consideration in this paper are those dumped from vessels. These
191
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materials are emphasized because preventive programs for wastes discharged
from pipes are well established, having been continually improved over 50
years of experience, while programs to control ocean dumping and dredge
spoils are still new. Traditional sources of municipal and industrial
pollution are controlled under even stricter regulations in the 1972 amend-
ments to the Federal Water Pollution Control Act (FWPCA). All point sources
discharging pollutants into fresh and marine waters of the United States can
legally do so only under terms of a discharge permit. By June 1975 more
than 40,000 permits had been issued. In addition, all municipalities are
required to provide the equivalent of secondary treatment by July 1, 1977.
During the past five years, more than $5 billion of federal money was made
available to cities as a national share in the cost of constructing sewage
treatment works.
The United States, like many other countries, has experienced a number
of episodes involving toxic substances in bottom sediments. The following
three are typical examples:
--In April 1969, PCB (polychlorinated biphenyl) was first detected in
the United States in oysters in Escambia Bay, Florida. Further study showed
PCBs in the water, sediment, fish, blue crabs, and shrimp. The source was
found to be a leak from an industrial plant 10 kilometers upstream. Since
1969, PCBs have been found in fish and shellfish from several bodies of
water including the Great Lakes. The U. S. Food and Drug Administration has
established temporary tolerances in food. For edible portions of fish and
shellfish the level is 5 mg/kg (milligrams per kilogram), but the agency is
considering lowering this level in the light of recent toxicity findings.
--In the spring of 1970, high levels of mercury were detected in fish
in Lake St. Clair. To protect the public health, Canada, on the east shore,
banned the sale of fish taken from the lake, and Michigan, on the west
shore, did the same. These actions triggered an intense examination and
search for mercury problems elsewhere and emphasized the issues of toxicity
to people, bio-magnification, and ecosystem effects. During the following
months bans were issued on fish and fishery products taken from waters in
several other areas of the country because of mercury content.
--The most recent episode of national concern began in July 1975 when
it was discovered that several workers in a chemical plant at Hopewell,
Virginia, became ill and showed classic symptoms of pesticide poisoning. It
was determined that they were seriously ill from massive occupational
exposure to Kepone (1). As a result, the plant which was producing the
Kepone was shut down a short time later. It was then discovered that
during and subsequent to plant operation, Kepone had found its way into the
environment, including the James River system, by way of waste effluent,
seepage, and air convection. Varying amounts were found in the water, soil,
and bottom sediments. Residues found ranged from 0.1 to 2.0 mg/kg in fish
and shellfish, even in samples collected as far away as 64 kilometers from
the source. These levels found in fin fish, crabs, and oysters caused
officials to prohibit fishing in these waters. Remedial actions are still
underway.
192
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SOURCES OF POTENTIALLY TOXIC SEDIMENTS DUMPED IN OCEANS
Quantities of waste materials disposed from ships and barges increased
from 1968 to 1973 and then decreased somewhat as a result of newly insti-
tuted regulatory action (Table 1). Industrial wastes and sewage sludge were
dumped at sea in similar amounts up to 1974. During 1975, industrial
dumping decreased markedly while sewage sludge dumping remained essentially
unchanged. Over the years most of these industrial wastes have been trans-
ported to sea in vessels of 907 to 4,535 metric ton capacity to sites
between 6 and 200 kilometers offshore. Greatest tonnage of dumping has been
on the Atlantic Seaboard. Only industrial wastes have been dumped in the
Gulf of Mexico, decreasing from 1.3 million metric tons in 1973 to 112,000
metric tons in 1975. The limited dumping in the Pacific Ocean was brought
to an end by 1975.
TABLE 1. TYPES AND AMOUNTS OF MATERIALS DISPOSED IN THE OCEANS
(IN METRIC TONS, APPROX.) (2, 3, 4, 5)
Combined Total: Atlantic, Pacific, & Gulf of Mexico
Waste Type
Industrial Waste
Sewage Sludge
1975
3,125,500
4,570,900
1974
4,165,000
4,544,100
1973
4,581,100
4,443,300
1968
4,254,700
4,060,600
Construction &
Demolition Debris
Solid Waste
Explosives
359,100
0
0
698,800
180
0
883,100
200
0
520,600
23,600
13,800
Total
8,055,500
9,408,080
9,907,720 8,873,300
Industrial Wastes
The types of contaminants in industrial wastes dumped at sea vary with
the industry involved. Some wastes are highly toxic; for example refinery
wastes often contain cyanide, heavy metals, mercaptides, and chlorinated
hydrocarbons. Data for 1973 and 1974 show dumping of mercury and cadmium
off the Atlantic Coast (6). With some areas not reporting, the figures in
Table 2 are minimal. In addition to mercury and cadmium, chemical plant
193
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wastes often contain many kinds of toxicants including arsenic, persistent
organic compounds, and sometimes numerous other forms. New chemical products
and wastes from their production create continuing challenges.
TABLE 2. MINIMUM ANNUAL INPUTS OF MERCURY AND CADIMUM
DUE TO OCEAN DUMPING OFF THE ATLANTIC COAST (6)
Mercury
kg.
1974
Cadmium
kg.
Mercury
kg.
1973
Cadmium
kg.
1,609.7
22,348.3
2,786.8
16,407
Sewage Sludge
In the United States most sewage sludge is disposed of on land or by
incineration. Only small amounts—4 million tons on a wet basis—were
dumped at sea in 1968, but this amount has increased slightly each year up
to 1975. -Most of this sludge is dumped outside New York Harbor from origins
in New York and New Jersey metropolitan areas. Because of its origin and
nature, sewage sludge contains numerous residues of modern organized commu-
nity living. These residues are of almost infinite variety—reflecting the
food we eat, the medications we take, the cleansing agents and household
chemicals we use, and the wastes from the community's business and industry
tributary to the system. The range of toxicants to be expected is almost
infinite also, although the concentrations may be low except in special
circumstances.
Dredge Spoils
In recent years the U. S. Army Corps of Engineers has dredged an annual
average of 290,519,870 cubic meters of sediments for maintenance of the
nation's waterways (7). Dredging by other jurisdictions for different
purposes is a much lesser activity. In 1968 and again in 1973 the tonnage
of dredge spoils was about five times the tonnage of all other wastes com-
bined (2). Moreover, it was found in 1968 that 34% of the total amount of
dredge spoils was polluted based on measurements of coliform bacteria,
chlorine. BOD, COD, volatile solids, oil and grease, phosphorus, nitrogen,
iron, silica, color, and odor--as judged by a set of criteria still being
evaluated. Dredge spoils from Lake Erie were found to contain heavy metals--
cadmium, chromium, lead, and nickel--at levels deemed detrimental to aquatic
life. Recently, laboratory studies seeking to evaluate the impact of open
water disposal of dredged sediments have included scrutiny of metals and
pesticides (7, 8).
Unfortunately, there apparently has been no search of broader scope to
determine the geographical extent and frequency of toxic chemicals in
194
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marine dredge spoils. Hence, the magnitude of the toxic chemical problem
can only be surmised. Nevertheless, the array of pollutants that have been
found suggests that a wide variety of toxic components could be present with
them.
LEGISLATION AND CONTROL PROGRAMS
In 1972, the United States passed a law as a step toward protecting the
ocean, the coastal waters, and the Great Lakes. This legislative action was
stimulated by a great national concern that dumping offshore was adversely
affecting the marine environment. There was apprehension on the part of
many people that the following vital values would be impaired:
--Provision by the Great Lakes, the coastal area, and adjacent
seas of critically needed food and minerals.
--Utilization of such areas as biologically productive habitats
for fish and wildlife.
—Provision of transportation, recreation, and a pleasant setting
for more than 60 percent of the nation's population.
--Critical function of the oceans in maintaining the world's
environment, including oxygen—carbon dioxide balance, global
climate, and cycling of the planet's water.
The increasing appearance of episodes like the ones involving mercury,
PCBs, Kepone, and other toxic substances that already were exacting health
and economic toll added to citizen uneasiness. It was obvious that the
crucial environmental values cited above could be even further impaired if
pollution of the coastal waters continued to increase.
The new law, the Marine Protection, Research and Sanctuaries Act of
1972, has three main objectives; regulation of dumping, research aimed at
finding ways to end all ocean dumping, and the creation of marine sanctu-
aries.
Procedures established under the new law to regulate dumping are now
well established. The law categorically prohibits the dumping of certain
materials such as high-level radioactive wastes and all biological, chem-
ical, and radiological warfare agents. Dumping of all other wastes, with
the exception of dredge spoils, is regulated by the Environmental Protection
Agency (EPA). The regulations include general criteria which require that
the Environmental Protection Agency consider the following factors before
granting a permit for ocean dumping or for outfall discharges into the
ocean:
--Need for proposed dumping or discharge.
--Effect of dumping or discharge on marine environment.
195
-------
--Social and economic impacts, effects on health and welfare, fishery
resources, recreation, and other values.
--Alternate disposal means available.
--Feasibility of dumping beyond the continental shelf.
Figure 1 summarizes the permit procedures in a schematic flow sequence.
Only officially designated dumping sites may be used. Eleven sites in the
Atlantic Ocean and Gulf of Mexico are now in use for municipal and indus-
trial wastes. None of these wastes are dumped in the Pacific Ocean, although
municipal sewage sludge enters the ocean through outfalls that are regulated
under other legislation (FWPCA). Dumping site surveys are under way in
several locations. They are designed to assess the impacts of dumping
activities on the ecology of the dumpsite. Such derived information will
provide guidance for improving regulatory procedures.
APPLICATION SUBMITTED TO REGION
PRELIMINARY EVALUATION OF APPLICATION
1
PUBLIC NOTICE OF APPLICATION WITH TENTATIVE DECISION
_L
J.
TENTATIVE DECISION TO ISSUE | I TENTATIVE DECISION TO DENY
I • »
REQUEST FOR HEARING
I
HEARING
I
FINAL EVALUATION OF APPLICATION
ISSUANCE OF PERMIT | | DENIAL OF PERMIT
I
NOTIFICATION OF COAST GUARD
SURVEILLANCE
MONITORING OF DUMP SITE ENFORCEMENT ACTION
Figure 1. Permit procedures (6).
196
-------
The Environmental Protection Agency has taken a highly restrictive
approach to ocean dumping by requiring all dumpers to seek environmentally
acceptable alternatives even though their wastes may meet the agency criteria
for permits. As a result of this strong action, 75 former dumpers on the
Atlantic Coast have stopped dumping, and 8 more were to have stopped by June
of this year (9). Moreover, by a recent ruling, dumping of almost 5.5
million wet tons of sewage sludge into the New York Bright by New York and
New Jersey communities is scheduled to end by December 31, 1981. Planning
must begin immediately for provision of environmentally acceptable land-
based disposal facilities. By the end of 1976 waste dumping in the Gulf of
Mexico will be reduced to 10 percent of the 1973 figure.
The Ocean Dumping Act assigns surveillance of dumping activities to the
U. S. Coast Guard. Surveillance methods include escorting or intercepting
dumping vessels at the dump site by boat or aircraft, spot checking ships'
logs, and using vessel riders to ascertain position and dumping rate. From
April 1973 to December 1974, 983 surveillance missions were carried out, and
36 violation notifications were referred to the Environmental Protection
Agency encompassing 154 apparent violations (6). Under its authority, the
Environmental Protection Agency has assessed civil penalties of up to $40,000
for permit violations. There is also a provision for pursuing legal action
in criminal court. During 1974, 98 permits were in force, but the number is
decreasing as acceptable alternate methods of disposal are adopted.
Another aspect of control program activity relates to unexpected
crises. Reactions to crisis problems like those caused by mercury, PCBs,
and Kepone involve several similar stages:
—Eruption of the crisis.
--Evaluation of problem scope.
--Action to protect the public health and welfare.
--Corrective action for this episode.
--Prevention of other episodes.
The Kepone crisis may serve as an example of these reactions. Having
long since passed through the first two stages, attention now centers con-
currently on the remaining three. Actions to protect the public health and
welfare include: (a) closure of the James River to fishing because of the
Kepone levels in fin fish, oysters, and crabs; (b) monitoring Kepone levels
in these organisms in the river and adjacent waters; and (c) testing citizens
of the area for blood levels of Kepone.
Corrective actions underway or planned include: (a) dismantling the
Kepone production plant, cleaning up the site, and disposing of the plant
remnants in a state-approved landfill and (b) treatment of residual liquid
wastes from production and hydroblast cleaning of the plant before disman-
tling. A further corrective action, step (c), relates to a problem of great
197
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magnitude—the James River sediments. The continuing contamination of fish
and shellfish appears to be coming from Kepone in the bottom sediments.
Removal of sediments by dredging is under consideration by the Environmental
Protection Agency, the State of Virginia, and the U. S. Army Corps of Engi-
neers. A test dredging for Kepone removal was completed recently and the
results are being analyzed.
To prevent additional Kepone episodes, orders have been issued by the
Environmental Protection Agency under the Federal Insecticide, Fungicide,
and Rodenticide Act to stop the sale and use of this poison. To prevent
other episodes of similar kind, the Environmental Protection Agency has
taken steps some time ago to establish effluent standards for the following
toxic pollutants: DDT (DD, DDE), aldrin/dieldrin, endrin, toxaphene, ben-
zidine, and PCBs. Moreover, some of these agents have been de-registered
for general use in the United States, and others are to be restricted for
use solely by licensed, certified applicators. Such actions help to limit
the opportunities for entry of these substances into bottom sediments.
Dredged material may be dumped under permits issued by the U. S. Army
Corps of Engineers, but only after the permit proposal has been reviewed and
approved by the Environmental Protection Agency in keeping with provisions
amended to the Federal Water Pollution Control Act in 1972. In issuing such
permits the Corps is required to use EPA-designated sites wherever possible
as well as the disposal criteria developed by the Environmental Protection
Agency as for other dumping.
New legislation recently enacted by the U. S. Congress will, if enacted
into law by signature of the President, further decrease the possibilities
for accumulation of toxic substances in bottom sediments. The Toxic Sub-
stances Control Act, which has been under consideration for some time, is
the product of public concern over the broad dimensions of the toxicity
problem—including (10):
--Magnitude of chemical use and continuing appearance of new
chemical products.
--Environmental presence of toxic substances that:
are implicated in human disease*
contaminate food
cause environmental damage.
--Episodes involving:
PCBs
Vinyl Chloride
Kepone
Asbestos.
*Including carcinogenicity, mutagenicity, and teratogenicity.
198
-------
The federal government already controls such things as food additives,
pesticides, and nuclear materials. The new law will address the 1,000 or
more new chemicals that enter the U. S. market each year. If passed in its
present form, the proposed new law will require manufacturers to report all
new chemicals three months before production, authorize the Environmental
Protection Agency to screen such substances before they are marketed, order
testing for potentially dangerous ones, and ban those that threaten health
or the environment.
RESEARCH ON TOXIC SUBSTANCES IN BOTTOM SEDIMENTS
A provision of the Ocean Dumping Act fosters research to find ways to
minimize or end all ocean dumping within five years. The results of such
programs, once completed, will go a long way to mitigate the toxic aspects
of such pollution. But in addition, a myriad of other research activities
pursued under provisions of the Federal Water Pollution Control Act address
in a broader way many aspects of the toxic substances problem—not only in
marine areas, but in freshwater ones as well. The following list of specific
research areas suggests the scope and significance of studies currently
underway or soon to be initiated and implies the new useful information that
will result from these efforts:
—Determination of acute and chronic toxic effects on marine and
freshwater organisms and ecosystems caused by the following
pollutants and pollution-related activities:
Complex waste mixtures.
Petrochemicals, energy-related organic solvents from offshore
drilling and ocean dumping.
Onshore petroleum extraction, refining, and fossil fuel use.
Selected inorganics, complex organics, and pesticides.
Suspended particles, especially asbestos.
Kepone.
--Determination of the significance, hazards to humans, bio-magnifi-
cation, persistence, transformation, and ecosystems effects of
carcinogenic pollutants.
--Investigation of potential substitute pesticides to learn their
chemical routes, biological effects, and degradation rates in
marine and freshwater.
--Development of bioassay procedures using single species in static
and flow-thru systems to estimate the ecological impact of dredge
material disposal in marine and freshwater.
199
-------
--Development and testing of biostatistical methods of quantitive
assessment of the effects of stress on marine communities.
--Development of mathematical models of chemical equilibration of
metals in seawater.
These research activities, which constitute many separate projects, are
almost evenly divided between work done by government staff in the Environ-
mental Protection Agency laboratories and grant-supported work done in
universities and other research institutions. The Environmental Protection
Agency laboratories most involved are the following:
Corvallis Environmental Research Laboratory, Con/all is, Oregon.
Duluth Environmental Research Laboratory, Duluth, Minnesota.
Gulf Breeze Environmental Research Laboratory, Gulf Breeze,
Florida.
Narragansett Environmental Research Laboratory, Narragansett,
Rhode Island.
The growing awareness of the problems of toxic substances in bottom
sediments in the United States and the regulatory and research actions that
have been taken as a response offer prospects for an orderly diminution of
this problem. Because toxic substances easily find their way into the
environment and because this problem occurs in many countries, the joint
concern by the United States and Japan, the exchange of scientific infor-
mation, and cooperative projects that may be undertaken will benefit all of
mankind. We, therefore, must continue the effective communication estab-
lished among our scientists and engineers as we move forward in responding
to this challenge.
REFERENCES
1. EPA Environmental News (August 17, 1976); and EPA Kepone Fact Sheet
(June 28, 1976).
2. Council on Environmental Quality, OCEAN DUMPING—A National Policy.
A Report to the President, Washington, D. C. (October 1970).
3. EPA Regional Offices, Unpublished Reports--8 months of dumping
activity, May to December 1973, under permits issued by Ocean
Disposal Program extrapolated for 12 months to provide an annual
rate (1973).
4. EPA Regional Offices, Unpublished Reports—updated information, 12
months of dumping activity (1974).
5. EPA Regional Offices, Preliminary Figures from Unpublished Reports--
12 months of dumping activity (1975).
ZOO
-------
6. EPA, Ocean Dumping in the United States--1975. Third Annual Report
of the Environmental Protection Agency (June 1975).
7. Chen, Kenneth Y.; Gupta, Shailendra K.; Sycip, Amancio Z.; Lu, James
C. S.; Knezevic, Miroslav; and Choi, Won-Wook; Contract Report on
Research Study on the Effect of Dispersion, Settling, and Resedi-
mentation on Migration of Chemical Constituents During Open Water
Disposal of Dredged Materials. Paper prepared for joint U. S.-
Japanese Conference, Corvallis, Oregon (November 17-21, 1975).
8. Fulk, R.; Gruber, D.; and Wullschleger, R.; Laboratory Study of the
Release of Pesticide Materials to the Water Column during Dredging
and Disposal Operations. Paper prepared for joint U. S.-Japanese
Conference, Corvallis, Oregon (November 17-21, 1976).
9. Breidenbach, Dr. Andrew W. (Assistant Administrator for Water and
Hazardous Materials), Statement Before the Subcommittee on Oceans
and the Atmosphere Committee on Commerce. U. S. Senate, Washington,
D. C. (April 12, 1976).
10. Council on Environmental Quality, Toxic Substances (April 1971.)
201
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HYDRAULIC DREDGING AS A LAKE RESTORATION TECHNIQUE:
PAST AND FUTURE
S.A. Peterson
Criteria and Assessment Branch
Con/all is Environmental Research Laboratory
United States Environmental Protection Agency
Corvallis, Oregon 97330
USA
ABSTRACT
Hydraulic dredging in freshwater lakes has given
rise to serious environmental concerns. Examples of
past dredging projects are described here and the paucity
of factual data from these projects is pointed out. Lack
of reliable data makes it difficult to predict the ecological
effects of dredging freshwater lakes. Federal funding
through the "Clean Lakes Program" will be the impetus for
new lake restoration dredging projects in the United States.
Potential advantages and disadvantages of dredging lakes
are addressed. Lake Lansing, Michigan provides an example
of the type of dredging project which may be funded.
Evaluation of these projects should provide answers to
many of the environmental concerns associated with dredging.
INTRODUCTION
In the past, "Environmentalists have pictured the dredge as the
dragon in paradise, wreaking mindless destruction to valued natural
resources"(1). While this view may be extreme, there are a number of
potentially legitimate environmental concerns associated with dredging,
especially inland lakes. These include increased turbidity, reduced
light penetration, increased oxygen demand, reduced pH, alteration of
water temperature patterns, release of pollutants from resuspended and
newly exposed sediments, and reduced water levels, in addition to a
variety of effects on the biological community. All of these may
culminate in significant long range ecological modifications. However,
at present there is a lack of data on many of these factors; consequently
the purpose of this paper is to describe some of the problems associated
with dredging nutrient enriched organic and inorganic sediments from
lakes and to describe a research program to evaluate environmental
concerns of future dredging activities.
Arguments in favor of dredging include improved boating and associated
activities, and altered temperature patterns resulting in lower summer
202
-------
surface temperatures which encourage green rather than blue-green algal
growth (2). One of the most positive restorative factors associated with
dredging is the physical removal of the nutrients contained in the
sediment.
Lake basins can be compared to reaction chambers that respond to
changes taking place within them and in their watersheds. An increase in
nutrient supply causes subsequent increases in productivity. The primary
producers, zooplankton, and higher organisms become overabundant as a
result of the increased nutrient supply. Eventually these organisms
die, to be replaced by members of the same species or by different
species better adapted to changing conditions. In either case the lake
system continues to thrive as long as nutrients are available to the
primary producers.
Nutrients are regenerated and recycled in part by both dead and
living organisms in the water column; some of this organic material
settles to the bottom where it undergoes further decompostion. If pro-
ductivity in the euphotic zone of the lake exceeds decomposition in the
aphotic zone, an oxygen deficit is incurred in the deep water with a
resultant accumulation of organic debris on the bottom; the depth of the
lake is reduced. Phosphorus under anaerobic, low pH conditions is
highly soluble and accumulates in deep water as long as thermal stratification
of the lake persists. Many lakes in advanced stages of eutrophication
are shallow, however, and periodically are subject to thermal and chemical
destratification by wind action. The accumulated nutrients of the deep
water zone are then mixed throughout the lake, utilized by phytoplankton
in the euphotic zone, and the cycle of accelerated productivity begins
anew. Several investigations have referred to this partially self-
sustaining mechanism of the eutrophication process (3,4,5,6).
Since eutrophic lake sediments frequently regenerate plant nutrients
it is reasonable to assume that their removal from the lake would help
eliminate internal nutrient loading. It should be stressed, however,
that control of internal nutrient sources will be effective in reducing
eutrophication only if external nutrient supplies are controlled.
PAST EXPERIENCES WITH LAKE RESTORATION VIA HYDRAULIC DREDGING
Storm Lake, Iowa
In a 1970 survey of inland lake dredging projects in the Great
Lakes region, Pierce stated that, "There is no finished lake dredging
project in the upper Midwest from which complete and reliable data can
be obtained on the effect of lake dredging on the total lake environ-
ment" (7). He presented eight project histories of lake dredging in the
upper Midwest, none of which presented conclusive evidence of benefits.
An example is Storm Lake, Iowa, a shallow 1200 ha lake which has been
dredged intermittently since 1940. No information is available on the
total quantity of material dredged or from where it was removed. Disposal
of dredged material presented problems early in the project. Dredge
spoil was used to build an island in the lake and later was deposited in
203
-------
diked areas along the shore. Suitable material for dike construction
was limited, and dike failure in 1970 forced suspension of dredging.
Substantive technical information on the impact of dredging at Storm
Lake is not available (7).
Trout Lake, Florida
The Florida Department of Natural Resources recognized that much of
the productive fishery habitat in the state was being destroyed as a
result of nutrient pollution. The mechanism was a familiar one. Sustained
algal blooms precipitated detrital material to the bottom where it
underwent decomposition, creating an excessive oxygen demand. This
resulted in relatively non-utilized vast organic muck communities over
many lake basins, where benthic fish food organisms formerly were
abundant.
In 1970 and 1971, the Florida Department of Natural Resources
attempted an experimental restoration at Trout Lake, a 41 ha lake near
the town of Eustis (8). Approximately 31,850 m3 of organic muck were
removed, exposing 7 ha of sandy lake bottom. Lateral sloughing of the
muck wall on subsequent passes of the hydraulic dredge partially recovered
the exposed sandy bottom. The final result was 3 ha of clean sand
exposed. Over a two month period this area was further reduced to 2.5
ha as a result of additional sloughing. Cost of this project was $9,163*
per hectare of bottom cleaned. The project report (8) contained no data
on the characteristics of the sediment, the disposal area, or chemical
characteristices of the lake environment during dredging. The only
mention of biological effects indicated that in areas converted from
muck to sand the diversity of the benthic population increased. It
apparently now supports amphipods, prawns, clams, snails, ceratopogonids,
leeches, and naiads (dragonfly, damselfly, mayfly, and caddisfly) where
it formerly supported only oligochaetes and chironomids.
A subsequent report on this project is sketchy about the final
outcome (9). Almost all reported changes in the lake during dredging
were qualified so it was difficult to tell if the changes actually
resulted from the dredging. A statement by Crumpton and Wilbur (9)
indicated that increased turbidity, conductivity and total residue,
decreased pH, photosynthetic activity, chlorophyll-a_, calcium, sodium,
hardness and organic nitrogen, even though temporary, could be attributed
to the dredging activities. The phrase "even though temporary" is
confusing since data in the appendix of their report indicated that the
average concentrations of all the above parameters, plus magnesium,
total phosphorus and phycophyton pigments, were greater in the two year
post-dredging period than prior to, or during, dredging. It appears
that a trend toward greater diversity in the benthic fish food fauna may
have been realized; however, the authors reported that, "insufficient
benefits were accrued to enhance the existing fish populations" (9).
The long term effectiveness of the project is open to question based on
the Information presented.
* All monetary amounts quoted in this paper are given in United States
dollars.
204
-------
Results from the Trout Lake project produced several recommendations
regarding future dredging projects in confined lake basins. Among these
were that soft surface material should be removed over the entire
sediment surface area prior to removing deeper sediments. Evaluations
of the Florida experience further recommended that dredging begin at the
highest elevations and proceed to the lowest ones. This suggests that
bottom cleaning efficiency might be improved by dredging in a consecutive
ring pattern beginning at the periphery of the lake basin.
Long Lake, Michigan
A hydraulic dredging project by the Michigan Department of Natural
Resources from 1961 to 1965 was directed toward the same objective3of
improving fish habitat (10). Dredging removed more than 765,000 m of
organic material from Long Lake in Oakland County, Michigan. The size
of the lake was increased from 60 to 63 ha, and the depth from an average
of 0.75 m to 2.0 m; the maximum depth increased from 2 m to 4 m. Dredge
spoil was originally distributed over 6 ha of adjacent upland and marginal
wetland. Problems developed immediately when solids failed to separate
from the slurry, and it became apparent that additional spoil disposal
area would be needed. Dredge spoil eventually covered 17 ha to a depth
of 0.3 m to 1.8 m. All vegetation in the spoil area was killed. Vegetation
grew on spoil after the dikes were leveled, but eight years later many
of the original trees stand dead, attesting to the problems of spoil
disposal. The former marshland portion resembles a wetland, but is of
little value as a waterfowl habitat.
Persons using the lake now enjoy good boating and excellant bass
fishing. A 1969 survey indicated that the average bass had increased in
size over the pre-dredging average length by nearly 4.8 cm. Other
species apparently remained approximately the same size or became
slightly smaller. This might indicate a general trend in the fishery of
small warm water lakes when a portion of the macrophytes are removed.
Lake Herman, South Dakota
A small portion (4.2 ha) of one bay in Lake Herman was dredged
during the summers of 1970, 1971, and 1972 (Figure 1), to test the
effect of hydraulically dredging inorganic silt of high nutrient concentra-
tion from the lake. Lake Herman has a surface area of«546 ha, a maximum
depth of 2.4 m, and a mean depth of 1.7 m. The 145 km watershed is
farmed intensively for row crops and small grain. The lake is subject
to periodic destratifiation due to wind action. Poor soil conservation
practices have resulted in the deposition of approximately 2 m of silt
over the entire lake basin.
The dredged~bay area was deepened from 1.7 m to approximately 3.4
m. Some 47,860 m of dredge spoil were deposited in a 3.4 ha lakeside
area diked to a height of 1.5 m. Silt from the dredge slurry eventually
covered the disposal area to a depth of 1.4 m. At the end of the three
year project, drying had reduced the volume of this silt 50 to 60 percent.
205
-------
No settling agents were added to the slurry and no attempt was made to
treat the carriagewater return flow to the lake. Table 1 provides
information on phosphorus concentration reductions as the dredged material
moved from the sediment-water interface of the lake, through the dredge
pipe, the silt deposit area, and the runoff water returned to the lake.
Churchill et_ al_. (11) point out that in all instances the return flow
water had lower phosphorus concentrations than that in the immediate
vicinity of the dredge. The significance of this is questionable,
however, since phosphorus concentrations throughout the lake during the
same period were more than adequate to produce the algal blooms which
typically occur in Lake Herman each summer.
TABLE 1. CHANGES IN ORTHOPHOSPHORUS CONCENTRATION (mg phosphorus/1) AS
DREDGE SPOIL FROM LAKE HERMAN, SOUTH DAKOTA, MOVES SEQUENTIALLY
FROM THE LAKE TO THE DEPOSIT AREA, TO THE RUNOFF AREA, AND
BACK TO THE LAKE (modified from reference 11)
DATE
7/28/70
8/11/70
8/18/70
8/26/70
9/3/70
9/22/70
10/6/70
10/13/70
10/21/70
11/3/70
7/13/71
8/18/71
8/25/71
9/13/71
DREDGE BAY
OF LAKE
0.29*
0.38
0.38
0.49
0.50
0.54
0.53
0.57
0.57
0.49
0.43
0.52
0.41
DREDGE PIPE
EFFLUENT
__._
0.24
0.24
0.24
0.36
0.13
0.11
0.29
0.13
0.10
0.06
0.12
0.18
SILT DEPOSIT
AREA
0.15
0.29
0.28
0.30
0.20
0.11
0.06
0.15
0.16
0
DEPOSIT AREA
OUTLET
....
0.26
0.20
0.16
0.13
0.17
0.10
0.09
0.06
0.19
_ __ _
* At the sediment - water interface
More significant was the observation that orthophosphorus concentra-
tions increased by approximately 300 percent (from 0.17 to >0.5 mg
P/l) shortly after dredging commenced in July, 1970. In spite of the
relatively small dredging area, this magnitude of increase in phosphorus
concentration was noted throughout the lake; it occurred even in the
southeastern bay area which is separated from the main lake by a narrow
neck of water (Figure 1). Figure 2 indicates that phosphorus concentration
in the southeast bay tended to parallel that in the lake proper and
approximately two months after dredging began, phosphorus concentration
in the bay actually exceeded lake concentrations. Brashier et al.(12)
attempted to assess results by comparing Lake Herman data with those
collected from Lake Madison during the same period. Lake Madison is
206
-------
N
d
Kilometers
0 0.5 1.0
I I I
1.2—
LEGEND
Water depth (in meters)
Sediment depth (in meters)
Silt deposit area
Dredged area
X Water quality sample sites
Figure 1. Lake Herman, South Dakota (redrawn from reference 11).
207
-------
2.5r
ro
o
oo
o
CL
E
UJ
X
CL
O.
O
I
h-
cr
o
2.0
1.5
1.0
0.5
0.0
Lake Herman (average of 3 sites)
Lake Madison (average of 3 sites)
Southeast Bay of Lake Herman
/\
Dredging
Commenced
;
*4 /
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1970
Figure 2. Othophosphate (orthophosphate X 0.33 = phosphorus) in Lake Madison,
South Dakota (modified from reference 13).
-------
within 2-3 km of Lake Herman, but is more than twice as large (1,295
ha), has an average depth of 3.5 m, and is not subject to high silt
loading. Phosphorus data in Figure 2 depict Lake Madison as a more or
less typical eutrophic dimictic lake. Because of these differences,
direct comparison of the two lakes is difficult. Lake Madison does,
however, exemplify the typical seasonal phosphorus pattern of eutrophic,
dimictic lakes in the midwestern United States, and is thus useful to
show how polymictic Lake Herman differs from that pattern.
Another aspect of interest to the Lake Herman study was that
phytoplankton productivity did not increase dramatically along with the
increase in phosphorus concentrations (13). One explanation for this
might be that Lake Herman is normally a nitrogen limited lake and
increased phosphorus loading would have little impact. This is supported
by data of the National Eutrophication Survey Program (14) and by Churchill
ejt al_. (11) who stated that during algal blooms in the lake, the nitrate-
nitrogen concentration declines, sometimes to 0.0 mg/1. Another support-
ing factor is that nutrients other than phosphorus did not increase in
the lake water during dredging. In fact, it appears that ammonia and
nitrate levels in the vicinity of the dredge were actually lower than at
other locations in the lake. Perhaps this is due to rapidly decreasing
nitrogen concentration with increasing sediment depth as reported by
Churchill e_t aj_. (11).
The investigators on the Lake Herman project were reluctant to
attribute the increased phosphorus concentrations to dredging, since
they could demonstrate no phosphorus or turbidity gradient away from the
dredge. There appears to be good circumstantial evidence, however, to
support a conclusion that dredging did produce the increased phosphorus
levels. Table 2 from Churchill et^al_. (13) indicates there may be a
trend toward lower average summer phosphorus concentrations since dredging
was terminated at the end of summer 1972. Post dredging phosphorus
concentration ranges appear generally to be reduced and somewhat lower
on the low end of their range. Despite their reluctance to draw any
conclusions about the effects of dredging on the phosphorus concentrations
en Lake Herman, the authors indicated that, "there were no other noticeable
environmental changes that could readily account for this dramatic
increase in phosphates" (11).
TABLE 2. SUMMER PHOSPHORUS RANGES IN LAKE HERMAN, SOUTH DAKOTA, FROM
1969 to 1975 (modified from reference 13).
YEAR ORTHO PHOSPHORUS TOTAL PHOSPHORUS DREDGING PHASE
mg/1 mg/1
1969 0.20 0.25-0.46 Prior to dredging
1970 0.17-0.50 0.17-0.99 During Dredging
1971 0.17-0.50 0.20-1.06
1972 0.17-0.50 0.33-0.69
1973 0.03-0.30 0.13-0.46 Following Dredging
1974 0.03-0.50 0.13-0.66
1975 0.10 0.13
(through June) (through June)
209
-------
Lake Trummen, Sweden
Dunst ejt aj_.(15) cite the court case of Reuter vs. the Wisconsin
Department of Natural Resources to emphasize that a common criticism of
dredging projects is a lack of concern, on the part of the dredge
operators and those who commission them, for the overall environmental
effects associated with dredging. One noteworthy exception to this
generalization, is the project at Lake Trummen, Sweden.
By the early 1960's domestic waste discharge had deteriorated the
lake to the point that filling in the basin was considered by inhabitants
of the adjacent city of Va"xjo (16). Instead, however, a rehabilitation
plan was developed by the Lake Restoration Research Team at the University
of Lund. The team, consisting of limnologists, microbiologists, plant
ecologists and geologists, developed a comprehensive plan to restore the
lake and measure the success of their effort.
Lake Trummen has an area of 100 ha and, prior to restoration, a
maximum depth of 2 m and a mean depth of 1.1 m. Studies to determine
the predredge trophic status of the lake began in 1968 and continued
through 1970 when the restoration project was implemented. A half
meter of gyttja type sediment was dredged uniformly from the main lake
basin (17). In 1971 another half meter of sediment was removed from the
same area. Altogether, approximately 400,000 m3 of sediment and an
additional 200,000 m3 of water were removed. Water content of the
dredge spoil was minimized by using a specially designed intake nozzle
on the hydraulic dredge. Despite the indicated removal of about 1 meter
of sediment from the bottom, the lake was deepened by an average of only
40 cm. This suggests that the fine sediment may have shifted and been
redistributed over the lake basin. Part of the macrophyte and gyttja
dredge material'was disposed of in three diked-off bays which were
overgrown with macrophytes (Figure 3). Care was taken to keep the
dredging of macrophyte vegetation in the lake to a minimum, consistent
with Sweden's policy of nature conservation. The remainder of the
dredge spoil was pumped to diked settling ponds on an old farm area from
which the top soil had been removed. The return flow water was treated
with aluminum sulfate to remove phosphorus and suspended solids. Total
phosphorus concentration of lake water prior to restoration was about
600 yg P/l, that of the dredge slurry approximated 1 mg P/l and that
returned to the lake after treatment was about 30 yg P/l. Following
restoration, total phosphorus concentrations have occasionally reached
levels of 70 to 110 yg P/l (18). Interstitial water orthophosphorus
concentration in 1973 was 200 to 500 times lower than in 1969 (18).
The dried dredge spoil was sold to greenhouses, parks, etc. as top
soil dressing for approximately $2 per cubic meter, and the proceeds
helped finance construction of green belts and parks around the lake.
An indication of the environmental concern evident in the Lake Trummen
Project is demonstrated by the one large bay overgrown with macrophytes
left intact as a waterfowl reservation (Figure 3) and an artificial
island developed from dredge spoils for a waterfowl habitat.
Documentation of environmental changes associated with the Lake
Trummen Project are beginning to appear in scientific literature.
Bengtsson et^al_. (18) indicate that phosphorus and nitrogen have de-
creased drastically (Figure 4) and that the role of the sediment in
recycling nutients has been minimized. There was a general reduction
in phosphorus concentration of the lake water as dredging commenced
210
-------
METERS
-------
Kjeldahl-Nitrogen mgN/l
Total Phosphorus mgP/l
1968 I 1969 | 1970 | 1971 | 1972 | 1973
Phosphate mg P/l
Silica mgSi02/l
Figure 4. Kjeldahl-nitrogen, total phosphorus, phosphate phosphorus and
silica in Lake Trummen (0.2 m), 1968-1973 (from reference 18).
212
-------
(Figure 4), just the opposite of the experience at Lake Herman, South
Dakota. The total and orthophosphate as well as the Kjeldahl-nitrogen
levels are significantly lower than before or during the dredging program.
Biologically, the phytoplankton diversity index (Shannon diversity
index) increased from 1.6 in 1968 to 3.0 in 1973 (19). Secchi disk
transparency increased from 23 to 75 cm over the same period. Prerestora-
tion mean annual phytoplankton productivity was 370 g C/m2 (for 1968-
1969), but it declined to 225 g C/m2 following restoration (1972-1973).
In the latter case, more than 60 percent of the annual phytoplankton
production was attributed to algae less than 10 ym in size. Blue-green
algal biomass was drastically reduced and some species disappeared,
notably Osciliatoria agardhii.
Disturbance of the benthic community during dredging has always
concerned ecologists. Before dredging in Lake Trummen, the benthic
fauna was dominated by oligochaetes and chironomids (20). A year after
dredging tubificid oligochaetes and chironomids became much more numerous.
Andersson et_aJL(20) indicate the most striking qualitative change in
the benthos was the appearance of the clam Anodonta cygnen; the total
number of benthic organisms changed little. They attributed this to the
motility of chironomid larvae and the fact that the dominant species
swarms all summer, thus probably recolonizing newly dredged areas almost
immediately.
According to Carline (21), a long term project in the State of
Wisconsin to determine re-population rates by benthos in dredged spring
ponds exhibits varied results for similar ponds. For example, in two
different ponds, after five years the chironomid populations were only
55 percent and 40 percent, respectively, of predredging numbers. In the
case of amphipods, Gatnmarus increased ten fold in one case, but attained
only 30 percent of predredge levels in another case. Another amphipod,
Hyalella, was eliminated and has not reappeared. Initial reductions in
benthic populations may be related to physical removal, but lack of
recolonization and long term population reductions probably are more
closely allied to alteration of the lake substrate.
The results to date from Lake Trummen are highly encouraging,
although the data conflict somewhat with other studies. The project
demonstrates that nine summer months of dredging and an expenditure of
$500,000 has produced a dramatic difference in the lake and transformed
it into a clean multi-use recreational facility. Changes in Lake Trummen
will be followed closely through 1980 to determine the longevity of the
restoration. Although the Lake Trummen project is beginning to answer
many of the environmental questions associated with dredging of recreational
lakes and presumably will answer many more, it will not resolve all of
the questions and all of the apparent differences which have been
reported in the literature. The statement by Pierce (6) about there
being no finished lake dredging project with complete and reliable data
on environmental effects appears to be as valid today as it was in
1970.
213
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THE UNITED STATES CLEAN LAKES PROGRAM AND ONE EXAMPLE
OF A POTENTIAL LAKE RESTORATION DREDGING PROJECT
Dredging in the United States explicitly to remove polluted sediments
has not reached the scale reported in Japan. Most projects of this
nature are relatively small and associated with isolated spills of toxic
substances such as the one with polychlorinated biphenyl on the Duwamish
River Waterway in the State of Washington (22). Most dredging in the
U.S. is performed to maintain navigation lanes in estuarine waters and
large rivers. Dredging to improve recreational facilities and aesthetics
has been minimal. This will change as a result of Section 314 of Public
Law 92-500, the amended Federal Water Pollution Control Act which states
that:
A. "Each state shall prepare or establish, and submit to the
Administrator for approval:
1. An identification and classification according to eutrophic
condition of all publicly owned fresh water lakes in such
state;
2. Procedures, processes, and methods (including land use
requirements) to control sources of pollution of such
lakes and;
3. Methods and procedures, in conjunction with appropriate
Federal agencies, to restore the quality of such lakes.
B. The Administrator shall provide financial assistance to states
in order to carry out methods and procedures approved by him
under this section."
Under this law, EPA has received approximately 100 applications for
financial assistance to demonstrate lake restoration techniques which
will improve water quality, thereby enhancing the recreational and
aesthetic attributes of the lakes. A variety of restoration techniques
are being proposed, however, approximately 25 percent of those received
to date, propose dredging as part of the restoration plan (Table 3).
Discussion in this paper focuses on one of these potential dredging
projects.
Some of the attributes as well as the environmental concerns of
dredging have been mentioned previously. Another major concern in
dredging fresh water lakes is the environmental effect of dredge spoil
disposal. To frequently, the spoils are deposited in some adjacent
wetland with little concern for environmental consequences. This may be
the overriding concern associated with dredging as a lake restoration
technique. Wetlands, including marshes, swamps and bogs are unique and
valuable resources. They serve as habitat and breeding areas for many
species of fish, waterfowl, and other wildlife, and in some cases are a
valuable source of harvestable timber. Such areas may moderate extremes
in water flow, serve as groundwater recharge areas, and function in
natural water purification processes. They provide unique recreational
214
-------
TABLE 3. LAKE RESTORATION PROJECT APPLICATIONS WHICH INCORPORATE
DREDGING AS PART OF THE RESTORATION PROGRAM
LAKE AREA TOTAL COST*
hectares/acres $U.S.
Delaware Park, NY
Blue, I A
Stafford, CA
Lake Temescal Reg Park, CA
Fenwick, WA
Gi bra Her, CA
Covell, SD
Oelwein, IA
Steinmetz, NY
Ellis Brett Pond, MA
59th Street Pond, NY
Vancouver, WA**
Long, MN
Liberty, WA
Silver, WA
Penn, MN
Henry, WI
Noquebay, WI
Big, WA +
Lansing, +MI
Long, WA .
Collins Park, NY
Lilly, WI
12
372
81
4
10
121
4
--
1
2
2
1052
74
316
668
15
17
871
221
176
137
22
--
29
918
200
10
24
300
10
--
3
5
4
2600
184
781
1650
36
43
2152
545
435
339
54
--
1,000,000
745,000
580,500
609,450
276,000
10,000,000
350,000
30,000
78,360,
16, 000?
650,000
8,200,000
2,593,430
592,000
1,840,000
245,000
360,000
410,000
300,000
1,600,000
711,940
925,000
546,000
35,658,680
* Total project cost. Dredging may represent only part of this
cost. Federal government pays 50%, State and Local pay 50%.
**Pilot scale dredging project funded ($50,000).
+ Projects which are funded currently.
| Dredging portion of $1,000,000 project.
opportunities and contain many rare and endangered species. A wetland
once defiled will not revert to its former level of productivity for
many years, if ever.
For the above reasons, it is EPA's policy to minimize alterations
in the quantity and quality of natural water flows that nourish wetlands
and to protect wetlands from detrimental dredging or filling practices.
Any Federally funded project which anticipates an adverse effect to
wetlands will require the submittal of an environmental assessment
delineating the alternatives investigated and the reasons for their
rejection. A cost-benefit appraisal should be included where appropriate,
While the policy is strongly worded, and rightly so, it is recognized
that not all wetlands are of equal value. Some are naturally more
215
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productive than others, while in some, the productivity may be optimized
through various managerial practices. If, after careful evaluation of
alternatives, it is decided to use wetlands as dredge disposal areas,
they cannot be selected at random and for convenience. Consequently,
one of the greatest problems in freshwater lake dredging is where to
place the spoils in order to minimize the environmental impact, i.e.,
how to determine which wetlands might be filled, which ones might be
modified and managed, and which ones must be preserved! The fate of
many lake dredging plans will hinge on the basis of a satisfactory
resolution of these problems.
Lake Lansing, Michigan
Lake Lansing provides one example of the dredging restoration
projects being considered for funding under the "Clean Lakes Program"
and highlights what may be the overriding environmental concern with
dredging freshwater lakes—what to do with the dredge spoil.
Lake Lansing has an area of 176 ha, a drainage basin of 1029 ha, a
maximum depth of 10.5 m and a mean depth of 2.7 m. Approximately 37
percent of the lake is less than 1.5 m deep and 79 percent less than
3 m deep (Figure 5). The shore line is approximately 5 km with 86
percent in private ownership and 14 percent in public ownership (1971
data). Public ownership has increased somewhat through the recent
purchase of park property by the state.
Problems
The lake has long suffered from algal blooms, bacterial contamination,
stunted fish populations, aquatic weed growth and the accumulation of
approximately 3.5 m of bottom sediments. All have been attributed to
the influx of nutrient materials from septic tank disposal systems
serving permanent and summer residents around the lake (23).
According to Young e_t a]_. (24) the most recent blue-green algal
blooms on the lake were reported in the falls of 1959 and 1962 when
Microcystis aeruginosa, Microcystis flos-aquae, Coelosphaerium Naegelianum
and Anabaena sp. dominated the phytoplankton. In the spring of 1960,
Ceratium hirudinella was associated with a fish kill; that fall Tolypothrix
tenuis was dominant in the largest bloom ever recorded on the lake.
Aquatic macrophytes generally cover the entire lake basin
where the water depth does not exceed 4.5 m. The last detailed survey
of aquatic macrophytes was made in 1958 (25). At that time the dominant
macrophytes were Potamogeton spp., Myriophyllum, Ceratophyllurn and
El odea. The lake restoration proposal compiled by John R. Snell Engineering,
Inc. of Lansing, Michigan, states that macrophytes become such a nuisance
after June 15 that boating is difficult. This is particularly true for
sailboating, which is popular on the lake.
Chemical data for the lake are sparse; however, a general pattern
of increased Kjeldahl nitrogen in the deeper water during summer stagnation
reflects an increase in ammonia nitrogen levels. Total Kjeldahl nitrogen
reached levels of nearly 4 mg/1 during August of 1971. Increased concentra-
tions of reduced nitrogen were not evident under ice cover (24).
216
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N
i
FEET
Figure 5 Contour map of Lake Lansing, Michigan, {feet X 0.3048 = meters)
as originally drawn by Ball 1938 and reported by Young et al.,
1975. (from reference 24).
Phosphorus concentrations show a great deal of variation in Lake
Lansing and there appears to be little accumulation of phosphorus in
deep water during summer stagnation. Deep water samples from the lake
during the winter stagnation period, however, revealed orthophosphate
concentrations of approximately 150 ug P/l in March, 1972. This probably
217
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represents the maximum for the year, since the lake would ordinarily
become ice free shortly after this and the concentration would be reduced
by mixing with the overlying water. Biological uptake would further
reduce the orthophosphorus level. The fact that nutrient levels do
increase during the winter under ice suggests that the same might happen
during the summer "stagnation" period.
Thermal stratification in Lake Lansing was persistent from the
first week in June through most of September in 1971; however, none was
indicated in two previous studies cited by Young et^ al_ (24). It may be
that thermal stratification in Lake Lansing is intermittent, with irregular
recycling of nutrients from the sediments to the lake throughout the
summer. In such a case, due to more or less constant wash out, the lake
may not retain high concentrations of nutrients which would tend to be
released under stratified conditions. According to a draft environmental
assessment of the proposed Lake Lansing project, there are no data
available on the nutrient content of the lake sediments. This aspect of
the project needs to be examined at the earliest possible date. The
data presented by Young et^ al. (24) show that the deep water areas do
become anaerobic from June through mid-September. Ordinarily these
conditions would tend to cause the release of nutrients from the sediments.
There was a gradual trend in this direction during the period of summer
stratification in 1971, but phosphorus concentration never exceeded
80 ug P/l, not exceptionally high for a eutrophic lake.
At one time, there was some concern over the possibility of mercury
toxicity as a result of dredging in Lake Lansing; however, that has been
largely dispelled. The source of the mercury in this case was from
atmospheric fall out, but concentrations in the sediment amounted to no
more than 115 yg/kg (dry weight). Khalid et^ al_. (26) found that low
levels of mercury added to river sediment under controlled laboratory
conditions were most readily recovered (desorbed) in their bioavailable,
soluble and exchangeable forms under strongly reducing and alkaline (pH
8.0) sediment conditions. High concentrations of added mercury were
most readily recovered from oxidized, acid environments (pH 5.0).
Neither environment would likely be encountered in lake dredging. The
same authors indicated that sediment containing high concentrations of
adsorbed mercury, if oxidized, (as could happen during dredging and
dredged material disposal) would most likely convert bound mercury to
the bioavailable form. It was further shown, however, that the quantity
released under dredging conditions would be very small relative to the
total sediment mercury content. It has been pointed out that up to 50
percent of the mercury contained in dredge spoil may leave the settling
pond with return flow and that this mercury may be attached to small
particles constituting only 2 percent of the dry contents of the dredged
sediments (27). Westermark and Ljunggren (28) have suggested that
aluminum sulfate treatment might reduce the mercury content of biologically
treated municipal waste effluents by more than 80 percent. Jernelov and
Lann (27) suggest the same technique can be applied to dredge spoil
return flow water.
The major problem with mercury, of course, is its bioaccumulation
potential. The mercury content of fish in Lake Lansing has been reported
to range from 0.05 to 1.01 mg/kg on a wet weight basis (29). This range
represents concentrations high enough to be of concern (U.S. Food and
218
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Drug Administration prohibits the sale of fish containing >0.5 mg/kg
Hg). However, in view of the relatively small quantity of mercury
contained in Lake Lansing sediment and the potential treatability of
return flow water, it is thought that any additional possibility of
mercury toxicity due to dredging the lake is minimal. Nevertheless,
mercury in the lake and the return flow water will be monitored carefully
during dredging.
As previously mentioned,'the major nutrient problems in Lake
Lansing have been attributed to leaching from septic tank drain field
areas around the lake. Installation of a sewage interceptor system
completely around the lake in 1965 alleviated much of the problem.
There are few published data on the water quality of the lake following
installation of the sewer system, but local residents indicate that
algal blooms have decreased in recent years. At the same time, rooted
macrophytes (which obtain part of their nutrient supply from the sediment)
have apparently increased. These macrophyte problems, together with
shallowness, which interfers with boating, have prompted the preparation
of the current $1.6 million dredging proposal by the Ingham County,
Michigan, Lake Lansing Lake Board. Half of the funds for this project
are being provided by the Federal Government under the 314 Clean Lakes
Program.
Objectives of the Lake Restoration Project
The foremost objective of this demonstration project is to remove
aquatic macrophytes and organic sediment by hydraulic dredging to
deepen the lake and remove the potential for resuspension of sedimented
nutrients; thereby optimizing its recreational potential. A secondary
objective, if funded, would be to evaluate the effectiveness of the lake
restoration project in terms of improved water quality and the associated
economic and social benefits realized by the local community.
Approach
The lake will be deepened selectively to 3.5 m using a cutterhead
hydraulic dredge. Approximately 1.3 million m3 of sediment will be
removed from various sites which encompass approximately 80 percent of
the lake basin (Figure 6). Areas to be left intact will reduce the
amount of spoil to be removed and will provide habitat diversity within
the lake. It is estimated that 45 percent of the sediment removed will
be organic silt, 40 percent marl, and 15 percent sand. Shaping of the
lake basin will result in a 10 percent slope of the bottom for a distance
of 9 m from shore. From 9 to 27 m the slope will be 3.3 percent, and
beyond 27 m again 10 percent*to a depth of 3.5 m. Dredging will take
place between April and December; an estimated three years will be
required to complete the project.
Dredge spoil will be pumped to selected spoil disposal areas. The
originally proposed disposal sites are shown in Figure 6 together with
the area surrounding the lake considered by the consulting engineers as
economically feasible for disposal. However, objections have arisen to
proposed sites within the "economical pumping limit ring," because many
219
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are valuable wetland habitats (30). Project consultants do not favor
disposal beyond the economical pumping limit because of the cost of
pumping and returning water to the lake from outside the natural drainage
basin. Return flow to the lake is necessary to maintain the water level
during hydraulic dredging.
Economical
limits of
pumping
\
N
Figure 6
LEGEND
nil
Area to be dredged in lake I Wetland ranking
HI In quadrants
No dredge area in lake '
Proposed dredge disposal areas
Residential development around the lake
Lake Lansing, Michigan showing area to be dredged, residential
areas, and proposed dredge disposal sites, (modified from
reference 30).
220
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Since much of the area surrounding Lake Lansing is wetland and
marsh, and since 1.3 million m3 of dredge material requires disposal,
the original proposal would result in filling nearly 70 percent of the
wetlands surrounding Lake Lansing. This was unacceptable to the Michigan
Department of Natural Resources, and to Federal agencies, primarily the
Fish and Wildlife Service and EPA (note previously mentioned policy on
protection of wetlands).
The grant for the Lansing project was funded with a proviso that
alternate dredge disposal sites be selected. The consulting engineers,
the Snell Environmental Group, contracted with the Department of Fisheries
and Wildlife at Michigan State University to determine the relative
value of wetlands bordering the lake (30). This was a positive approach
to the problem; however, no new potential dredge disposal sites were
added for evaluation.
The Michigan State University researchers concluded from their
evaluation of the wetlands that those in quadrant I (Figure 6) were the
most valuable and should be left intact as wildlife lands (30). In
quadrant II, sections 2D and 9 were considered most valuable, and it was
recommended they be left intact. The report concluded that all potential
spoil sites in quadrants III and IV on the west side of the lake were
suitable for spoil disposal. The wetland habitats were ranked by Cole
and Prince according to the method of Golet and Larson (31).
The basic problem here is inadequate disposal area. To complete
the project as it is currently designed, a spoil disposal area sufficient
to contain 1.3 million m3 of spoil will be required. The primary disposal
sites selected by the consultants on the basis of economics and engineering
priority included several areas within quadrants I and II of the Michigan
State University Report (30). If the recommendation of that report
concerning dredge disposal in quadrants I and II were followed, as much
as 640,000 m3 of the consultants' proposed disposal area would be elimi-
nated from consideration. Therefore, further exploration was necessary
to select alternative disposal sites.
The consultants recently developed a method of ranking the origin-
ally proposed and the subsequently selected alternate spoil disposal
areas (Figure 7). These areas were ranked by a weighted system with the
percentage of the final numerical index associated with each category
shown in Table 4. It can be seen that the weighting system is strongly
oriented toward economics and engineering. It represents an attempt to
rank the potential wetland disposal sites, but ecological considerations
have been downgraded. Some of the areas identified are still considered
to be unfillable based on their wildlife habitat value, e.g., area
number 8 in Figure 7 is the same as number 2 D (Figure 6) in the Cole
and Prince report (30); an area recommended to be left intact.
Despite the lack of ecological sensitivity, the rating system may
provide a focal point for discussion and final selection of dredge
disposal sites. The highly biased cost factor (50 percent of rating)
should be eliminated from the rating scale and disposal site selection
made on the basis of minimizing adverse environmental impact. Cost will
need to be considered in the final selection but should not be used as a
criterion for ranking the spoil disposal areas. Final selection will
have to satisfy both the grantee and EPA. If more area is required than
can be reasonably agreed upon, reduction of the total amount of dredging
might be required.
221
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LEGEND
Type "A" spoil area is classified as wetland
Type "B"spoil area is classified as highland
Figure 7. Most recent proposed dredge disposal and alternate disposal sites
for the Lake Lansing Restoration Project (from reference 32).
-------
TABLE 4. WEIGHTED RANKING SYSTEM FOR DETIRMINING IF A GIVEN AREA
AROUND LAKE LANSING SHOULD BE USED AS A DREDGE DISPOSAL
SITE (modified from reference 32)
Category of Consideration Percent of Total Rating
1) M1ch1qan State University
wetland priorltlzatlon 10
2) Estimated total cost to project
per volume of dredge spoil 50
3) Percent of the proposed spoil area
that 1s true high land 10
4) Swamp class 5
Months wet/yr 5
Private or public land 5
Future land use 5
Judgement factor 10
TOO
[VALUATION PROJECT
Assuming that agreement on disposal sites 1s reached, research may
be carried out to evaluate the results of the manipulation Hmnologlcally
and soc1o-econom1cally. Tvaluatlons of this type are the primary reason
for Involvement of the CorvalUs Environmental Research Laboratory
(CERL) 1n the Clean Lakes Program.
A research proposal to determine the effect of dredging Lake Lansing
has been submitted to EPA by Dr. C.D. McNabb of the Department of
Fisheries and Wildlife at Michigan State University.
According to McNabb (33) the Lake Lansing project would be evaluated
in terms of changes 1n the following parameters:
1) mean standing crop of planktonk and filamentous algae and the
maximum summer standing crop of macrophytes 1n the littoral zone.
2) species composition of the phytoplankton, filamentous algae and
macrophyte communities.
3) rate of oxygen depletion 1n deep water areas of the lake.
4) maximum dally oxygen and C0« differences 1n the open water and
shoreline areas of the lake during Ice-free periods.
5) ratio of monovalent (Na, K) to divalent (Ca, Mg) cations 1n the
lake.
6) availability (concentration) of carbon, nitrogen, phosphorus and
silica during Ice-free periods.
223
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7) availability of toxicants (arsenic, copper, and mercury) throughout
the year.
8) quantity of solids, nutrients, and toxicants discharged from the
lake over the study period.
9) species composition and standing crops of fish-food organisms in
zooplankton and benthos.
10) species composition, age structure, growth rates and condition
factor of fish populations.
McNabb (33) has described a rational approach for evaluating this
dredging project. He proposes to emphasize that which will be most
directly affected, the flora and fauna of the benthic community. One of
the more interesting and unique methods of analyzing the data from Lake
Lansing will center around Figure 8 in which McNabb (34) suggests that
recreational lakes in southern Michigan may be ranked according to a
relationship between aquatic plant standing crops and the availability
of essential nutrients. It has been pointed out that dredging the
littoral zone of the lake to 4 m will not necessarily make this area
unsuitable for aquatic plants. Post dredging analyses of reinvasion
rate and species composition of the new plants will be important in
evaluating dredging as a lake restoration tool.
The socioreconomic analyses of this project would assess the sig-
nificant changes in the economy and social structure of the community
near the lake. This study would pursue two different avenues, one along
the lines of a recreational travel-cost approach and the other to estimate
the value of the lake to the user in terms of boating, fishing, swimming,
and picnicking. The negative aspects of restoration would also be
analyzed i.e., improved water quality may put undue recreational stress
on the system and actually produce a detrimental effect.
The evaluation project will be realized, of course, only if the
demonstration project (the lake restoration by dredging) proceeds to
completion. That is dependent upon resolution of dredge spoil disposal
site problems, which in turn will determine final engineering plans for
the project and possible modification of the evaluation research.
Therefore, the actual lake restoration at Lake Lansing could be substanti-
ally different from what is anticipated at this time. The fate of other
lake restoration dredging projects in the Clean Lakes Program may be
influenced significantly by the outcome of the one at Lake Lansing.
SUMMARY
--Dredging as a means of restoring the recreational potential of fresh-
water lakes is relatively untested.
--Past experience with dredging has produced mixed results regarding
ecological effects of the projects.
--The 314 Clean Lakes Program will provide the impetus for dredging lake
restoration projects in the near future; Lake Lansing Michigan is one
example of the type of dredging projects being proposed.
224
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ro
ro
Planktonic Algae
Relative magnitude •••••••••••••••••••••••
of Growing Season
Mean Standing Fresh Fl,arnentous Algae
Weights u.......v..............:.:.;.;.;...;.;.v.;.».
f
O
Z
5 Q
ID Z
x en
l|
< u]
UJ
o:
u.
t
Plateau of Nutrient Competition
Diversity Decline Toward
Clodeg canodens/s
Ceratophyllum demersum
Modern Expansion of
Submersed
Native Mixed Flora
K^^^^^g:
Acceptable Public Health
Stage Equilibrium
To Zero in Anaerobic
Sewage"LaKes"
Pre-Development Stage Equilibrium
AAA
ESSENTIAL NUTRIENTS AVAILABLE TO PLANTS
Figure 8. Generalized relationship between standing crops of aquatic plants and increas-
ing fertility in recreational lakes of southern Michigan (from reference 34).
-------
--Only through proper evaluation of such projects will we be able to
predict the potential for success and the environmental trade offs of
future dredging projects.
ACKNOWLEDGMENTS
My sincere thanks to Russell C. Dunst, Wisconsin Department of
Natural Resources, and to my CERL collegues Hal V. Kibby, Kenneth W.
Malueg, Bruce A. Tichenor, Donald B. Porcella, and Charles F. Powers for
their time, constructive criticism and suggestions for preparation of
this paper. Thanks is also extended to Clarence D. McNabb, Jr., Michigan
State University, for permission to reference his proposal to evaluate
the environmental effects of dredging at Lake Lansing, Michigan.
REFERENCES
1) Turner, T. M. and Fairweather, V., "Dredging and the Environment:
The Plus Side" Civil Engr. 44, 62 (1974).
2) Wetzel, R. G. "Limnology." W. B. Saunders Company. Philadelphia,
Pennsylvania. 743 pp. (1975).
3) Sawyer, C. N., "Basic Concepts of Eutrophication" Jour. Water Poll.
Control Fed., 38, 737 (1966).
4) Emery, R. M. £t a_]_., "Delayed Recovery of a Mesotrophic Lake After
Nutrient Diversion." Jour. Water Poll. Control Fed., 45_, 913
(1973).
5) Larsen, D. P. et^ a_l_. "Response of Eutrophic Shagawa Lake, Minnesota,
U.S.A., to Point-Source Phosphorus Reduction." Verh. Internat.
Verin. Limnol. ]_9, 884 (1975).
6) Haertel, L., "Ecological Factors Influencing Production of Algae in
Northern Prairie Lakes." S.D. State Univ., Water Resource Inst.,
Completion Rep., Proj. No. A-208-SDAK (1972).
7) Pierce, N. D., "Inland Lake Dredging Evaluation." Wis. Dept. of
Nat. Resources, Tech. Bull. 46, Madison (1970).
8) Wilbur, R. L., "Experimental Dredging to Convert Lake Bottom From a
Biotic Muck to Productive Sand." Water Resources Bull. 1^, 372
(1974).
9) Crumpton, J. E. and Wilbur, R. L., "Habitat Manipulation." Dingell-
Johnson Job Completion Report, Proj. No. F-26-5. Florida Game and
Fresh Water Fish Comm. (1974).
10) Spitler, F. J., "Dredging Along Lake Michigan to Improve Boating
and Fishing." Mich. Dept. Natural Resour. Tech. Bull. 73-17 (1973).
226
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11) Churchill, C. L., et aj_., "Silt Removal From a Lake Bottom." EPA
Ecol. Res. Ser. 660/3-74-017 (1975).
12) Brashier, C. K., et_ al_., "Effect of Silt Removal in Prairie Lake."
EPA-Ecol. Res. Ser. R3-73-037 (1973).
13) Churchill, C. L. ejt al_., "Evaluation of a Recreational Lake Re-
habilitation Project." OWRR Comp. Report No. B-028-SDAK. Water
Resources Inst., South Dakota State University, Brookings (1975).
14) National Eutrophication Survey. "Preliminary Report on Lake
Herman, Lake County, South Dakota, EPA Region VIII," Corvallis
Environmental Research Laboratory, Corvallis, Oregon. 7pp mimeo
(1976).
15) Dunst, R. C., e_t al_., "Survey of Lake Rehabilitation Techniques and
Experiences." Wis. Dept. Nat. Resources Tech. Bull. 75, Madison
(1974).
16) Bjflrk, S., et^al_., "The Lake Trummen Restoration Project: A
Presentation." The Lake Restoration Researchers Team, Univ. of
Lund, Sweden. 36p mimeo. (1971).
17) Bjflrk, S., "European Lake Rehabilitation Activities." Plenary
lecture at the Conference on Lake Protection and Management,
Madison, Wis. Oct. 21-23, 23 p. mimeo (1974).
18) Bengtsson, L., et^ al_., "Lake Trummen Restoration Project I. Water
and Sediment Chemistry." Verh. Internat. Verein. Limnol. 19, 1080
(1975).
19) Cronberg, G., ejt, al_., "Lake Trummen Restoration Project II.
Bacteria, Phytoplankton, and Phytoplankton Productivity." Verh.
Internat. Verein. Limnol. 1_9, 1088 (1975).
20) Andersson, G., et a_l_., "Lake Trummen Restoration Project III. Zoo-
plankton, Macrobenthos and Fish." Verh. Internat. Verein. Limnol.
1£, 1097 (1975).
21) Carline, R. F., Project Leader, Wisconsin Department of Natural
Resources, P. 0. Box 203, Waupaca, Wisconsin, USA 54981.
22) Pavlou, S. P., e£al_., "PCB Monitoring in the Duwamish River: A
Study of Their Release Induced by the Dredging Activities in Slip-
1." University of Washington, Department of Oceanography, Special
Report No. 66, Ref. No. M76-46, Seattle (1976).
23) Kettele, M. J. and Uttormark, P. D., "Problem Lakes in the United
States." University of Wisconsin Water Resources Center Tech.
Report 16010 EHR 12/71, Madison (1971).
227
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24) Young, T. C., ejt al_., "Project Completion Report Predredging
Analysis of Lake Lansing, Michigan." Michigan State University,
Institute of Water Research Tech. Report No. 43 (1975).
25) Roelofs, E. W., "The Effect of Weed Removal on Fish and Fishing in
Lake Lansing." Dept. of Fisheries and Wildlife, Michigan State
University, East Lansing. lOpp (1958).
26) Khalid, R. A., et^ al_., "Sorption and Release of Mercury by Miss-
issippi River Sediment as Affected by pH and Redox Potential."
Paper presented at 15th Annual Hanford Life Sciences Symposium,
Richland, Washington Sept. 29 - Oct. 1, ERDA Symp. Series (1975).
27) Jernelov, A. and Lann, H., "Studies in Sweden on Feasibility of
Some Methods for Restoration of Mercury—Contaminated Bodies of
Water." Environmental Science and Technology _7, 712 (1973).
28) Westermark, T. and Ljunggren, K., "Report to the Swedish Applied
Research Council." No. 4952 (1968).
29) D'ltri, F., et_ al_., "An Estimation of the Total Mercury Content in
Some Lake Lansing Fish and Sediments." Reprint Presented to the
Lake Lansing Lake Board Meeting, Meridian Township, Michigan.
(1971).
30) Cole, R. A. and Prince, H. H., "Fish and Wildlife Values of Wet-
lands Bordering Lake Lansing Proposed as Potential Spoil Disposal
Sites." Dept. of Fisheries and Wildlife, Michigan State Univer-
sity, East Lansing. Report prepared for Snell Environmental Group
Consulting Engineers in support of Lake Lansing Restoration Project
EPA No. 66405, April 26, (1976).
31) Golet, F. C. and Larson, J. S., "Classification of Freshwater
Wetlands in the Glaciated Northeast." Bur. Sport Fisheries and
Wildlife, Research Publication No. 116. 56pp. (1974).
32) Personal Communication. Letter from Snell Environmental Group,
Lansing, Michigan, dated August 27, 1976.
33) McNabb, C. D., "Evaluation of Dredging as a Lake Restoration
Technique." Michigan State University Dept. of Fisheries and
Wildlife. A research proposal submitted to EPA for Federal as-
sistance. (1976).
34) McNabb, C. D., "Aquatic Plant Problems in Recreational Lakes of
Southern Michigan. Michigan Department of Natural Resources,
Lansing, 53pp. (1975).
228
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INTERCHANGE OF NUTRIENTS AND METALS BETWEEN SEDIMENTS AND WATER
DURING DREDGED MATERIAL DISPOSAL IN COASTAL WATERS
by
D. J. Baumgartner, D. W. Schults, S. E. Ingle and D. T. Specht
Marine and Freshwater Ecology Branch
Corvallis Environmental Research Laboratory
U. S. Environmental Protection Agency
Corvallis, Oregon 97330
ABSTRACT
Conventional barge dumping of over 100,000 m3 of channel
sediment was arranged by the Corps of Engineers at a
controlled experimental dump site in Elliott Bay, Puget
Sound to study the fate and effects of metals, polychlo-
rinated biphenyls (PCBs), and nutrients in the dredged
materials. Periodic sampling was conducted before,
during, and at several intervals after dumping to deter-
mine the distribution and uptake of materials as well as
other biological effects resulting from the dumping. The
objective was to provide guidance to the regulatory
agencies regarding the effects of disposal of material
containing measurable levels of pollutants in "open
water" disposal sites. Incidental to this purpose,
research was undertaken to improve analytical techniques,
handling of samples and understanding of chemical pol-
lutant mobilization between water and sediment as it
affects the marine environment.
The purpose of this paper is to present an overview
and some partial results of this unusual project and
to describe methods employed.
229
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Perturbations in some water quality parameters were con-
siderable but short term during the dumping operation.
The concentration of chemical species in the water were,
however, below the values recommended as maximum concen-
trations by the Committee on Water Quality Criteria
(U. S. Environmental Protection Agency, 1973). Partial
results of sediment analyses indicate that there has not
been substantial chemical alteration of the disposal
site environment.
INTRODUCTION
Both the United States Environmental Protection Agency (EPA) and the Corps
of Engineers (COE) are seeking information about the environmental impact of
dredging and disposal operations so that these operations will be tech-
nically satisfactory, economically feasible and yet protect the environment.
Part of the COE research is to evaluate the environmental effects of open
water disposal of dredge material as authorized under the 1970 River and
Harbor Act. Similarly, the EPA under the Issuance of Permits for Dredge and
Fill Material (Section 404 of Public Law 92-500) needs additional informa-
tion to establish guidelines and procedures on open water disposal. To
learn more about environmental effects associated with open water disposal
of dredged material, the COE initiated the Duwamish Waterway Project in
Puget Sound, Washington. The dredging of the Duwamish Waterway with sub-
sequent marine "open water" disposal of the dredge material into Elliott Bay
on the river delta, offered an opportunity to observe environmental effects
principally from heavy metals, PCBs and nutrients. The objectives of the
field investigation are to:
a. Document the release of chemical species from the dredged material
to the water column during the following disposal operations.
b. Measure uptake, if any, of heavy metals and PCBs by important
species of demersal fish and shellfish.
c. Determine the effect of dredged material disposal on benthic and
demersal faunal abundance and distribution and the rate and
extent of benthic recolonization in the area of the dredged
material deposit.
The role of EPA in the cooperative study is twofold: (a) to provide data on
routine analyses of chemical constituents, and (b) to conduct research on
the behavior and effects of certain chemicals as particulates move from the
barge and become incorporated into the sea bed. Both field and laboratory
investigations are being performed to define the extent of release and
movement of chemical species. Laboratory evaluations include long and short
term release of heavy metals from deposited material to seawater; response
of a marine test alga in seawater before and after mixing the seawater with
dredged materials; and, in the laboratory, the response of benthic animals
230
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to deposited material. Much of the research is presently in progress;
therefore, this report will present initial results of heavy metals and
nutrients for the field investigations before, during and after the disposal
operation and the results of the laboratory algal assay.
The National Marine Fisheries Service is documenting the biological uptake
of heavy metals and PCBs while Shoreline Community College is documenting
the rate and extent of benthic recolonization at the disposal site.
The analyses of PCBs in sediment and seawater are being conducted by
Dr. Spyros Pavlou at the University of Washington Oceanography Department.
SITE DESCRIPTION
The study area is located in the southeast section of Elliott Bay in Puget
Sound, Washington (Figure 1). Between January 27 and March 6, 1976, approxi-
mately 114,000 m3 of sediment were removed from the mid channel of the
Duwamish River and deposited in Elliott Bay near the river mouth at a depth
of about 60 m. Dredging was done on a 1.9 km section of river (river km
6.3 to 8.2) using a clamshell dredge and barge transportation to the disposal
site. The dredged river sediments were characterized as sandy silt whereas
the bay sediments are typically sand.*
PARAMETERS MEASURED
The chemical and physical parameters that were measured are listed in Table 1
The main emphasis of the study was on heavy metals, PCBs and nutrients.
Techniques used to preserve and analyze the samples are outlined in Table 2.
SAMPLING PROCEDURE
Sediment samples were taken by gravity cores in parallel and by Van Veen
grab for bulk analyses. Water samples for nutrients and metals were pumped
from three depths using plastic hose; samplers fabricated from stainless
steel beer barrels were used for collecting PCB samples. Water for PCB
analysis was filtered on board the Research Vessel Hoh (R/V Hoh) using glass
fiber filters in stainless steel holders.
Sediment cores were obtained from the Research Vessel Streeter. One core
was processed on board for subsequent PCB analysis. A second core was held
for metal, grain size, and nutrient analysis.
SAMPLING SCHEDULE
The sampling was divided into three main periods: background, disposal
period, and post-disposal period. During the background sampling, 19
*During the oral presentation 14 color slides were shown to aid in visual-
izing the equipment employed for sampling and for handling the dredge
material. They have not been reproduced for this report.
231
-------
o
<_>
o
f.
a.
ro
CO
ro
Figure 1. General map of study area
-------
TABLE 1. CHEMICAL PARAMETERS
II.
III.
Water
pH
NH3
N03 - N02
OP
dissolved Cd, Cr, Pb, As, Fe, Mn
total Hg
participate metals
suspended solids
PCB
oil/grease
Sediment
Total
pH
Cd, Cr, Pb, As, Fe, Mn, Hg
organic C
Total and free sulfides
Eh
particle size
PCB
oil/grease
moisture
Elutriate test
NH3
N03 - N02
OP
dissolved Cd, Cr, Pb, As, Hg, Mn, Fe
PCB
Interstitial
dissolved Cd, Cr, Pb, As, Hg, Mn
NH3
N03 - N02
OP
PCB
233
-------
TABLE 2. SUMMARY OF PRESERVATION AND ANALYTICAL METHODS
Parameter
Preservation
Method of Measurement
Sediment moisture
Soluble Cd, Cr, Pb, Mn, Fe
in seawater
Hg in seawater and sediments
Cd, Cr, Pb, Mn, Fe
in sediments
NH3-N
N02-N03
Ortho P
Soluble As in. seawater
As in sediment
1% HN03
1% HN03+16ppm Au
freeze dried
40 mg/1 HgCl2
40 mg/1 HgCl2
40 mg/1 HgCl2
1% HN03
freeze dried
soluble sulfide in sediment frozen in absence
of air
total sulfide in sediment
frozen in absence
of air
Eh
particle size distribution air dried
suspended solids in seawater
organic carbon
PCB
freeze dried
hexane
dry at 70°C
atomic absorption
spectrophotometer (AA)
digestion in aqua
regia, cold vapor AA
analyses
HN03/HF digestion, AA
analyses
distillation, auto-
mated indophenol blue
automated cadmium
reduction followed by
diazotization
Murphy-Riley
arsine generation, AA
analyses
HN03 digestion/plasma
emission spectro-
photometer
cadmium nitrate
titration using
sulfide electrode
acid generation,
cadmium nitrate
titration using
sulfide electrode
Pt-calomel electrode
hydrometer technique
0.45u membrane filter,
dry at 70°C
O.I.C. carbon analyzer
gas chromatography
234
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river sediment cores (length to 0.6 m) were obtained with a Benthos Gravity
Corer from river km 6.3 to 8.2. Likewise, cores were taken from 16 stations
at the disposal site and four reference stations (Figure 2). Analyses were
done on the total core and interstitial water. To evaluate the pollution
potential of the river sediment, additional tests were performed including
elutriate test, algal assay of elutriate test water and benthic bioassay
using the river sediment. The purpose of this background sampling was to
predict what chemical species might be solubilized and of concern during and
after disposal of the river sediment to Elliott Bay, and to document any
algal and benthic response to the dredged material.
Sampling during the disposal period consisted of collecting water during
three consecutive disposal operations on two days. Each disposal operation
consisted of dumping two barges with 380-535 cubic meters of river sediment
each. Water was collected from two vessels, one at the disposal site center
(R/V Hoh) and the other about 60 m downwind (northeast) from the site center
(R/V Streeter). Each vessel collected water at the same time from three
depths, 1 m below the surface, mid depth and 1 m above the sediments. The
sampling frequency was: -15, 0, 5, 10, 15, 25, 45, 75, and 120 minutes
after the dump. Water samples were also collected at the reference stations
at the beginning and at the end of each day's monitoring. The main objective
of monitoring the disposal period was to identify the release of chemical
species from the dredged material to the water column.
The activities during the post-disposal period consisted of sampling the
sediments and the water column at the disposal site and the reference sta-
tions. Sediments were collected 1 week, and 1 and 3 months after the dumping
was completed. The upper 10 cm and the lower portion of the sediment core
were analyzed separately. The water was sampled at the same three depths as
during the disposal period. The purpose of the post-disposal sampling was
to determine the long term effects of dredged material disposal on the
migration of chemical species in the sediment and to the water column.
RESULTS
All the sediment and water samples have not been analyzed, but the initial
data indicate some distinct differences between the bay sediment and dredged
river sediment. Some of these differences can be seen in Table 3. Cadmium
was not detected and lead was lower in the river sediment than in Elliott
Bay sediment prior to dumping, so those two metals were not measured during
the disposal and post-disposal periods. Mercury levels in the river sediment
were similar to those in the bay sediment but it was monitored because of its
significance in the environment. Arsenic and chromium were at sufficiently
high levels in the river sediment to be of concern. Ammonia was about an
order of magnitude higher in the river sediments than in the bay sediments
and at a level that could produce an impact to the immediate disposal area.
From water column suspended solids data (Figure 3) obtained during the
disposal operation the dredged material appeared to settle through the water
column as a slug rather than in an extensively dispersed condition. This
tended to transport much of the soluble chemical species in the dredged
235
-------
REFERENCE
SITE B
EXPERIMENTAL
DISPOSAL SITE
REFERENCE
SITE A
MOUTH OF
OUWAMISH
D
DUWAMISH
RIVER
DUWAMISH •:
RIVER
STATIONS
Figure 2.
Map of study area showing sampling sites
236
-------
TABLE 3. SEDIMENT ANALYSES OF RIVER, SITE AND REFERENCE
STATIONS BEFORE DISPOSAL OPERATIONS
Bulk Analyses (mg/kg dry wt. )
Cd
Cr
As*
Hg
Pb
max
<2
109
70
0.7
120
River
min
<2
39
35
0.1
<2
Disposal Site
aver
<2
61
53
0.
20
max
<2
69
43
3 0
840
min
<2
12
19
.6 0
<12
Interstitial
Motal c
rlc Ud 1 o
(pg/i)
Cr
Hg
max
17
13.3
River
min
1
<"•
aver
<2
43
28
.2 0.4
105
Analyses
max
<2
54
33
0.
500
Disposal Site
aver
5.
6.
max
6 28
5 8
min
6
<1
aver
14.1
4.2
max
11
9
Reference
min
<2
54
23
6 0.2
<2
Reference
min
2
<1
aver
<2
54
28
0.
87
aver
6.
4.
4
2
5
Nutrients (mg/1)
NH3-N
Ortho P
40
1.69
0.6
<0.05
19.
0.
3 4
24 0
.0 0
.64 0
.4 2.1
.10 0.26
2.
1.
5 0.8
62 0.14
1.
0.
6
54
*neutron activation analyses
237
-------
1600
SHIP
DAY 57
SITE D
SURFACE*
BOTTOM «.
HOH
o
+
t
t
t
\
\
\
\
\
in
o
"1200
ro
CO
00
O
in
en eoo
*«
»,
400
•
•
•
600
1000
1200
1400
1600
TIME
Figure 3.
Suspended solids concentration in surface and bottom water
during dumping.
-------
material to the bottom rather than into the water column. There were,
however, some short term effects noted in the water column. For example
Figure 4 shows ammonia concentrations 1 m below the water surface and 1 m
above the sediments in the immediate area of the disposal site during the
disposal operation. A brief increase, especially in the bottom water was
noted a few minutes after the dredged material was dumped. Ortho P concen-
tration in the bottom water increased (Figure 5) immediately after the
disposal, but in the surface waters there was a slight decrease. Minor
fluctuations were noted in the N02-N03 concentration in the water column
(Figure 6). An elutriate test in which one volume of wet sediment was
shaken with four volumes of site water for 30 minutes under aerobioc con-
ditions, was performed on the river sediments. The results in Table 4 show
that NH3-N greatly increased in the site water after mixing with river
sediment and N03-N02 showed only a slight increase. Ortho P, however, was
removed from the site water by the sediment. Except for Ortho P the elu-
triate results agreed with the field observations.
TABLE 4. RESULTS OF ELUTRIATE TEST RUN ON RIVER SAMPLES
Cone, in Site Water Cone, in Interstitial H0 Cone, in Elutriate
Cr (Mg/D
Hg (ug/1)
NH3-N (mg/1)
N03-N02 (mg/1
4
<0.5
0.067
1) 0.426
7.4
6.2
16.3
—
3.5
<0.5
11.0
0.49
Ortho P (mg/1) 0.076 0.24 0.014
Initial data on mercury concentration in the water column of Elliott Bay
indicate that mercury was below the detectable level (0.5 ug/1). Some
soluble chromium was noted in the water column during disposal as shown in
Figure 7.
Algal assays (U. S. Environmental Protection Agency, 1974) using site water
(control) and elutriate water (test) indicated that the net effect of sedi-
ment dumping on algal growth in Elliott Bay water results from the stripping
of phosphorus from the water column, thus making the water, normally N or N
and Si limited, phosphorus limited. The elutriate sample and elutriate plus
1.0 mg/1 EDTA produced about the same amount of growth, both about 7% of the
control (control = 34.6 mg/1 algal dry weight, elutriate = 2.4 mg/1), indi-
cating that heavy metals released from the sediment were probably not sig-
nificant to algal growth.
Table 5 lists the concentrations of NH3-N, Ortho P ang Hg found in the sedi-
ment interstitial water at the disposal site and reference stations before
and after the disposal operation. Ammonia-N, which was an order of magnitude
239
-------
.40 ..
SHIP HOH
DAY 57
SITE D
SURFACEx
BOTTOM +
t
t
t
t
t
O
'.30
rn
ro
-£»
o
.20 ..
1000
1400
1600
1200
TIME
Figure 4. Ammonia concentration in surface and bottom water during dumping,
-------
t
9
$
.16
SHIP HOH
DAY 57
SITE D
SURFACEx
BOTTOM *
o
'.12
OL
O
I
h-
cr
ro O.OB
.04 .
1000
1200
TIME
1400
1600
Figure 5. Ortho P concentration in surface and bottom water during dumping,
-------
.40
SHIP
DAY 57
SITE D
SURFACEx
BOTTOM +
HOH
o
.30
rn
o
ro
-P>
ro
CM
O
'..20 ..
.10 ..
800
1000
1200
1400
1600
TIME
Figure 6. N02-N03 concentration in surface and bottom water during dumping.
-------
16
SHIP HOH
DAY 57
SITE D
SURFACEx
BOTTOM «,
O
12
PO
-P»
CO
O
CT
I
O
600
1000
1200
TIME
1400
1800
Figure 7. Soluble chromium concentration in surface and bottom water
during dumping.
-------
greater in the disposal material than the background bay sediments, increased
greatly in the disposal site interstitial water after the disposal operation.
One week after disposal higher concentrations were observed in the top 10 cm
of the sediment when compared to the sediment below 10 cm; later the sediment
below 10 cm had the higher concentration.
Mercury, likewise, was greater in the interstitial water immediately after
the disposal operation but was near background levels after one month. The
influence of the disposal operation on Ortho P in the interstitial water was
not readily apparent.
TABLE 5. CONCENTRATION* OF CHEMICAL SPECIES IN SEDIMENT INTERSTITIAL
WATER (IW) BEFORE AND AFTER DISPOSAL
Period
Disposal Site
Reference Sites
IW in top 10 cm IW below 10 cm IW in top 10 cm
NH3 Ortho P Hg NH3 Ortho P Hg NH3 Ortho P Hg
Before
1 week
1 month
disposal
after di
sposal
after disposal
3 months after
disposal
2.16
9.46
9.37
7.08
0.26
0.27
0.31
0.08
4.2
6.8
2.1
2.2
--
7.07
9.54
8.51
--
0.18
0.23
0.15
--
6.5
4.4
2.9
1.64
3.19
0.42
1.25
0.54
0.14
0.17
0.14
4.5
0.8
2.4
1.6
*NH3 and Ortho P in mg/1
Hg in ug/1
ACKNOWLEDGEMENTS
The Duwamish Waterways project was designed and funded by the U. S. Army
Corps of Engineers Environmental Effects Laboratory of the Waterways Experi-
ment Station, Vicksburg, Mississippi. Drs. Jeff Johnson and Robert Engler
of the Experiment Station were responsible for initiating and coordinating
the research. The authors would also like to thank R. Manabe, K. Harris,
and M. Tollefson for analyzing the samples that are used in this report. We
also wish to thank C. Powers, B. Lauer, D. Taug, and J. Carkin for their
efforts in collecting and preparing samples and processing data.
244
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REFERENCES
U. S. Environmental Protection Agency. 1973. Water Quality Criteria 1972.
EPA-R3-73-033 594 p.
U. S. Environmental Protection Agency. 1974. Marine Algal Assay Procedure:
Bottle Test. National Environmental Research Center, Corvallis,
Oregon EPA-660/3-75-008 43 p.
245
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DREDGING CONDITIONS INFLUENCING THE UPTAKE OF HEAVY METALS BY ORGANISMS
J. F. Sustar and T. H. Wakeman
U.S. Army Engineer District, San Francisco
211 Main Street
San Francisco, California 94105
ABSTRACT
Studies were conducted by the San Francisco District
of the U.S. Army Corps of Engineers during the period
1971 through 1976 to evaluate the impacts associated with
dredging and sediment release at open water disposal
sites in San Francisco Bay. Although significant changes
were observed in dissolved oxygen reductions, suspended
solids increases, and trace elements, chlorinated
hydrocarbon and nitrogen (nitrate and ammonia) releases,
the changes were not found to be synonymous with biolog-
ical impacts. Uptake and desorption of trace elements
by organisms were observed. Contaminant levels in
estuarine organisms appear to be controlled by a limited
number of factors. Suggested factors are the long-term
process of sediment resuspension-recirculation, seasonal
fluctuations in salinity and sources of contaminants
both man introduced and geologic formation.
INTRODUCTION
During the late 1960's, an awareness of man's impact on the environment
and, in turn, on man himself became a focal point not only for new projects
but also for the maintenance of existing projects. Within an estuarine
system, the development of facilities for trade along with associated services
is the most noticeable impact. The continuance of the development is contin-
gent on the availability of deep water. This means dredging. The dredging
and disposal operation can be viewed from two different aspects. First, the
dredging and disposal operation is a separate and distinct activity. Second,
the dredging and disposal operation can be viewed in terms of associated
changes in the system, that is, the resulting channel. Aside from the land
development, this means changes in the estuarine regimes in terms of water
circulation, salinity, sediment type, contaminant levels and contaminant
sources.
From 1971 through 1976, the San Francisco District of the U.S. Army
Corps of Engineers conducted studies to assess the impacts associated with
maintenance dredging in San Francisco Bay with open water disposal of the
sediments. The study addressed the first view of the dredging and dispoal
246
-------
operation and attempted to advance the understanding of the interrelationships
between the physical, chemical and biological systems in the Bay. The various
systems were initially studied independently to form a characterization of
the Bay. These studies were followed by investigations of how the extreme
ranges of the various systems influence other systems, primarily, biological.
DESCRIPTION OF THE BAY
San Francisco Bay is a drowned valley through which passes the drainage
of the great Central Basin of California. The outlet to the Pacific Ocean is
the Golden Gate, 1.6 kilometer wide, 4.8 kilometer long strait with depths in
excess of 90 meters. The Bay system is composed of several distinct areas
separated by narrow straits. Suisun Bay at the upper end is moderately
narrow and allows runoff from the Central Valley to pass quickly into the
more saline areas west of the 11 kilometer long Carquinez Strait. San Pablo
Bay provides the first area of extensive mixing of freshwater runoff with
saline ocean water. The isolated South San Francisco Bay receives very
little runoff due to no large tributaries and several impoundments of small
local drainage area. A pronounced wet and dry season is characteristic of
the area with about 85 percent of the total rainfall occurring between Novem-
ber and April. The Bay system has an area of 1,026 square kilometers at mean
lower low water and 1,191 square kilometers at mean higher high water, leaving
extensive mudflats exposed at lower low water. The Bay is generally shallow
with two-thirds of the area less than 5.5 meters deep and only 20 percent
greater than 9 meters deep.
DREDGED SEDIMENT
With the exception of the sandy sediments associated with the San Fran-
cisco Bay Channel, Southampton Shoal, Pinole Shoal and Suisun Bay, mainten-
ance dredging operations in the Bay move "Younger Bay Mud." Bay mud consists
of soft, plastic, black-to-gray silty clay or clayey silt with minor organic
material and clayey fine-grained sand which has been deposited in the Bay
largely due to flocculation. A typical grain size is as follows:
Dispersed Non-dispersed
% Sand (>0.075 mm) 12 13
% Silt 46 87
% Clay (<0.002 mm) 42 0
Organic carbon content is about one and one-half percent and in situ density
is about 1.3 to 1.4 grams per cubic centimeter. The clay size fraction is
composed of one-third montmorillinite, one-third normal and hydrated mica,
and one-third mixed-layered montmorillinite, chloritic and kaolinitic materi-
als.
Sediment deposition patterns reflect the energy gradient formed by
dynamic estuarine forces within the Bay. Deposition zones are situated in
low energy areas where the energy of wave action and current velocity is
dissipated or nonexistent.
247
-------
Contaminants enter the San Francisco Bay system through natural weather-
ing processes of rocks and soils and by anthropogenic means on land, air and
water. Dissolved substances are sorbed by particulate matter both before
entry and after entry into the estuary. These organic and inorganic contami-
nants show behavior and distribution patterns similar to that of natural
sediments with the physical setting and estuarine processes responsible for
their movement and deposition. Mean concentrations of contaminants in the
Bay based on Corps of Engineers sampling are as follows:
Dredged Channels Undredged Areas
Lead ppm 35.5 34.3
Zinc ppm 108.1 110.1
Mercury ppm 0.55 0.71
Cadmium ppm 1.59 0.86
Copper ppm 41.6 36.2
Oil and grease ppm 800 500
Volatile solids ppm x 10** 6.03 5.65
COD ppm x 101* 1000 1000
Contaminant levels are generally associated with sediment type (particle
size) which is reflected in both vertical and horizontal distribution of
contaminants. This relationship is not absolute and other factors such as
proximity to source of contaminants, rate of shoaling, rate of contaminant
input and association to other parameters such as organics play a role in the
distribution. Highest contaminant levels are normally associated with the
finest sediments. As such, the higher concentrations of contaminants in
dredged channels can be attributed to the finer grain size associated with
maintenance dredging. Since dredged channels are out of equilibrium, forming
a lower energy regime, finer sediments will tend to shoal.
About 7.6 million cubic meters of sediments are dredged annually in San
Francisco Bay. The majority of the dredging is accomplished with a trailing
suction hopper dredge with maintenance of berthing facilities and marinas by
clamshell and hydraulic cutterhead dredges.
SEDIMENT RESUSPENSION AND INTERACTION WITH WATER
The type of sediment and the degree to which it is disturbed determine
the sediment resuspension during dredging and the immediate release pattern
during disposal at open water sites. The disturbance including the adding
and mixing with water depends on the type and size of dredge, the efficiency
of operation and the configuration of the shoal. With both hopper dredge and
clamshell dredge, the plume can extend more than 700 meters downstream.
Concentrations at overflow ports were measured as high as 8.7 grams per
liter. These concentrations are reduced quickly to the hundred milligram per
liter range. At the sediment-water interface, higher concentrations in the
range of 2 grams per liter were measured.
The disturbance during open water release is limited to the bottom few
meters of the water column regardless of whether the sediment mounds or
disperses. Complete mounding of cohesive, new construction sediments excav-
ated by clamshell was observed at a 100-fathom disposal site. Maintenance
248
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sediments excavated by hopper dredge were found to leave an 1n-bay disposal
site typically within fifteen minutes of release, being quickly assimilated
into the Bay sediment regime. In the case of mound, very little contact time
and area occurs between the sediment and water column, limiting the immediate
interaction of contaminants with the water column. With dispersal, contact
time and area with the upper water column is similar to that of mounding.
However, in the bottom two meters, sediment concentrations were immediately
dispersed to a transport concentration of about ten grams per liter for
single plume movement and about twenty grams per liter for interaction of a
twin plume as with a hopper dredge with two hoppers. With in-bay disposal,
the sediments were distributed over a 260 square kilometer study area to
depths in excess of 23 centimeters. The majority of the samples in the study
area had less than four percent dredged sediment.
Dredging and disposal in the Bay were not observed to cause significant
changes in conductivity/salinity, temperature of pH. In addition to suspended
solids increases, water quality changes which were observed to be significant
included dissolved oxygen reductions, and trace element, chlorinated hydro-
carbon and nitrogen (nitrate and ammonia) releases. During dredging dissolved
oxygen reductions were found to occur only about 25 percent of the time. The
reduction is about two parts per million and lasts for about two minutes
before returning to background, typically eight to nine parts per million.
Reductions at the sediment-water interface were as much as four parts per
million for about eight minutes. The upper water column during open water
disposal experienced reductions similar to the dredging operation. Near the
bottom in the base surge cloud, significant oxygen depletion was observed.
Reductions of up to six parts per million were observed. Ambient concentra-
tions were regained after an average of three to four minutes, but could be
influenced for as long as eleven minutes. With sediments having a lower
oxygen consuming material, increases in oxygen were observed.
The result of a selective extraction scheme indicated that a significant
portion of trace elements investigated are in the residual phase of the
sediment. They were mercury (77 percent), iron (60 percent), manganese and
zinc (54 percent), copper (53 percent), lead (50 percent) and cadmium (2
percent). Phases other than in the residual or lattice of the sediment are
available for release under proper environmental conditions. The two factors
which exert the greatest effects are pH and oxidation-reduction potential of
the ambient environment. The pH of the Bay system is near neutrality and the
dredging with open water disposal was not observed to cause a change. Of
significantly greater importance is the effect of oxidation-reduction poten-
tial shifts. Significant amounts of metals were found in the organic and
sulfide-Uke phases using a hydrogen peroxide treatment. They were cadmium
(92 percent), lead (45 percent), copper (43 percent), zinc (39 percent),
mercury (23 percent) and iron (19 percent). Bay sediments contain 1,000-
3,000 parts per million of sulfides and thus represent a reducing environment
with trace metals associated with sulfides expected. In sorption-desorption
experiments, oxidation-reduction potential was found to have the greatest
effect on trace metal fate. Under oxygen rich conditions, significantly more
copper, cadmium, lead and zinc were found in the elutriate that under reduced
conditions. Iron acted 1n an opposite manner. Higher salinity elutriates
significantly influenced higher cadmium and zinc concentrations in oxygen
249
-------
rich samples and Iron 1n oxygen deficient conditions. Agitation time signifi-
cantly affected the release of cadmium, copper and zinc under oxidizing
conditions. More metals were released at the longer shaking periods, suggest-
ing that a kinetic mechanism may play a role in the fate of trace metals.
The release of trace elements (cadmium, copper, lead and zinc) under oxygen
rich conditions in general increased the water column concentration 30 to 200
percent. Ratios of elutriate to original water concentrations in general
ranged from 1.3 to 2.0 for samples which originally had trace metal concentra-
tions similar to values found in the Bay.
In field monitoring, solute concentrations of cadmium, copper and lead
increased in the release plume by 6, 4 and 9 times respectively. Cadmium
concentrations increased from 0.22 parts per billion (ppb) to 1.35 ppb,
copper from 1.29 ppb to 5.0 ppb and lead from 0.21 ppb to 1.88 ppb. These
observed increases lasted less than one and one-half hours which was the
frequency of sampling.
BIOLOGICAL UPTAKE
Chemical reactions which might be biologically significant during dredg-
ing and disposal operations are not as intuitively obvious as impacts due to
physical distrubance. During both laboratory and field Investigations,
significant changes in water quality were demonstrated owing to chemical
reactions occurring from Bay sediment resuspension. No analogous changes in
organisms were observed. Water quality impacts were not found to be synony-
mous with biological impacts.
Field studies were conducted to determine uptake of silver, cadmium,
copper, mercury, nickel, lead, selenium, zinc, and arsenic by invertebrates
Macoma balthica, Neanthes succinea, Ampelisca milleri and Ischadium demissum
and the mussel Mytilus edulis^Two periods of heaviest rainfall for the year
causing pronounced decreases in salinity coincided with the two dredging
periods. Metal concentrations 1n sediments and invertebrates fluctuated
during the period of study. With the exception of nickle concentrations in
f[. succinea, no significant changes in metal levels were associated with
dredging activities although significant uptake and desorptlon did occur
throughout the study area. The changes in nickel were significantly greater
at stations outside the dredging zone suggesting that dredging 1nhib1t1ed
nickel accumulation in this species.
The results of associated nine day studies showed that the greatest
uptake and accumulation in M. balthica of the chloride salts of silver,
cadmium, copper, mercury and lead occurred with the highest concentrations of
these metals in the lowest salinity water. The greatest desorption of nickel,
selenium zinc and arsenic occurred 1n the clams exposed with the highest
salinity.
A second study was conducted during a disposal operation. The concentra-
tion of twelve trace elements (Ag, As, Cd, Cr, Cu, Fe, Hg, Mn, N1, Pb, Se,
and Zn) were monitored in sediments, suspended and settled particulates,
selected benthic invertebrates (Macoma nasuta, PectinaHa callfornlensls,
Stylatula elongata, Tritonia diomedia, Glycerna~amer1cana, and G. robusta)
250
-------
and transplanted mussels, Mytil us edulis. The experimental disposal operation
did not affect trace element concentrations in the benthic Invertebrates nor
in mussels transplanted to the disposal area.
Bay dredging and disposal activities were found to redistribute contami-
nated sediments without, under the conditions of the experiments, resulting
in increased contaminant availability. Fluctuations in the concentrations of
test elements were highly correlated with each other in sediment, inverteb-
rates, suspended and settled particulates, although element levels within any
one component were not correlated with element levels in any other component.
The high correlation among trace elements within each component suggests that
only one or a few parameters may control trace element fluxes in San Francisco
Bay.
CONCLUSIONS
Based on results of studies conducted in San Francisco Bay during the
Dredge Disposal Study, the following conclusions have been formulated regard-
ing trace element uptake by organisms.
Although significant changes in water quality during dredging with open
water disposal were demonstrated, no analogous changes in organisms were
observed. Thus, water quality impacts were not found to be synonymous with
biological impacts.
Release of trace elements during dredging and disposal operations seem
to be of sufficiently low leveles and last for such short durations that
their availability for uptake and accumulation is extremely limited.
Salinity increases significantly intensify the potential for release of
certain trace elements from resuspended sediments. Organisms have been
observed to have greater uptake rates during periods of decreased salinity
and greateer depuration rates in high salinity water. These two opposing
conditions suggets that there is potentially a natural defense mechanism
operating in organisms to safeguard them from excessive trace element accumu-
lation.
Contaminant levels in estuarine organisms appears to be controlled by a
limited number of factors. Suggested factors are the long-term process of
sediment resuspension-recirculation, seasonal fluctuations in salinity and
sources of contaminants both anthropogenic and geologic. The biological
impact may be dependent on the form of contaminant and whether or not the
sediment system can assimilate the contaminant loading. With the observed
sorption-desorption by organisms and the fluctuating conditions in the estu-
ary, impacts such as high accumulations, mutations and toxicity would not be
expected unless the contaminant loading is foreign, in the case of synthetic
chemicals, or above the assimilation capability of the estuary with the
associated sediment regime, in the case of a low energy regime in which the
changes in ambient conditions is great.
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ACKNOWLEDGEMENT
This paper is based on the Dredge Disposal Study - San Francisco Bay and
Estuary by the U.S. Army Engineer District, San Francisco. Publication of
this paper has been approved by the Corps of Engineers but the expressed
views, interpretations and conclusions are those of the authors and do not
necessarily represent those of the U.S. Army Corps of Engineers. Added
thanks is given to Mr. Richard Ecker, a memeber of the District task force
and to the Corps personnel and many contractors who conducted the individual
study elements.
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DREDGED MATERIAL DENSIFICATION AND TREATMENT
OF CONTAMINATED DREDGED MATERIAL
C. C. Calhoun, Jr.
Manager, Disposal Operations Project
Environmental Effects Laboratory
USAE Waterways Experiment Station
P. 0. Box 631
Vicksburg, Mississippi 39180
ABSTRACT
This paper describes work conducted by the
Disposal Operations Project of the U. S. Corps
of Engineers' Dredged Material Research Program
to develop methods for dredged material densi-
fication and treatment of contaminated dredged
material. Densification techniques include
conventional gravity drainage, mechanical agi-
tation, electro-osmosis, crust management,
aeration, frost action, wicks, and vegetation.
With the exception of aeration and frost action,
all techniques are being evaluated by large-
scale field tests. The applicability of various
conventional wastewater treatment methods to
dredged material is discussed. The extent of
oil and grease contamination associated with
confined disposal areas is reviewed. The use
of flocculants to improve the quality of efflu-
ents for confined containment areas is outlined.
Field tests to determine the effectiveness of
injecting oxygen and air into the pipeline during
open-water disposal to increase the dissolved
oxygen in the water column are discussed as well
as field tests to evaluate the ability of
vegetation to remove contaminants from disposal
area effluents.
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INTRODUCTION
The Corps of Engineers' Dredged Material Research Program (DMRP) is a
comprehensive five-year research program initiated in March 1973 to address
problems associated with the disposal of dredged material. The program is
being administered by the Environmental Effects Laboratory (EEL) of the
Waterways Experiment Station (WES), Vicksburg, Mississippi. The DMRP is
divided into four projects. This paper describes work being conducted within
the Disposal Operations Project to densify dredged material and to treat con-
taminated dredged material. The densification studies are under the direction
of Dr. T. A. Haliburton while the treatment studies are being directed by
Mr. T. K. Moore.
DREDGED MATERIAL DENSIFICATION
Background.
In most cases where fine-grained dredged material from harbors and
waterways is placed in slurry form into containment areas, the material
remains at high water contents for years. The large volume of trapped water
significantly reduces the capacity of the containment area to retain solids.
If significant quantities of this water can be removed, the service life of
containment areas will be extended and the problems associated with securing
new disposal areas reduced. Therefore the purpose of densification is to
gain additional volume and not to stabilize the area per se.
The feasibility, both economic and technical, of dewatering or densifying
dredged material is being addressed by DMRP Task 5A (Dredged Material Densifi-
cation). The major thrust of the work in this task was initiated in October
1974 by a planning symposium attended by a panel of experts in various fields
dealing with the removal or movement of water in soils and sludges as well as
dredging experts. From the symposium, guidance was given for establishing a
program for evaluating in the laboratory or by small-scale field studies the
feasibility of various techniques for dewatering dredged material. Although
there are many techniques for dewatering dredged material, the feasibility of
these methods is usually controlled by the economics of dewatering vast areas.
The dewatering of a single containment area may involve hundreds to perhaps
thousands of hectares. Consequently, the costs of applying to containment
areas conventional techniques used to economically dewater building foundations
or sludge fields may be prohibitively high. Consideration must also be given
to the characteristics of the site itself when selecting a dewatering tech-
nique. Techniques that may be applicable to active sites where the depth of
the material is not great may not be applicable to sites nearing capacity or
previously abandoned when filled with material 9 to 12 m deep. All of these
factors were considered when decisions were made concerning the techniques
to be evaluated.
A second symposium was held approximately one year later and the panel
evaluated the results of the laboratory and small-scale field studies and made
recommendations as to which techniques deserved further evaluation in the
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field. The various studies (work units) considered at the second symposium
are shown in Table 1. In addition, one work unit conducted prior to the first
symposium and a work unit in a related task are listed and discussed.
TABLE 1: DREDGED MATERIAL DENSIFICATION PRELIMINARY AND LABORATORY INVESTIGATIONS
Work Units
Contractor*
4A16 Performance of Containment Areas Filled with
Dredged Material
5A01 Methodology for Dredged Material Reclamation
and Drainage
5A02 A Laboratory Study of Dredged Material Slurry
Water Loss Due to Mechanical Agitation
5A03 State-of-the-Art Survey and Evaluation of Current
Physical, Mechanical, and Chemical Dewatering and
Densification Techniques
5A04 A Laboratory Study to Determine the Variables that
Influence the Electro-Osmotic Dewatering of Dredged
Material
5A05 A Laboratory Study of Aeration as a Feasible Techni-
que for Dewatering Fine-Grained Dredged Material
5A06 Feasibility Study of General Crust Management as a
Technique for Increasing Capacities of Dredged
Material Containment Areas
5A07 Feasibility of Frost Action for Densification of
Dredged Material
5A10 Development of Capillary Enhancement Devices for
Dewatering Fine-Grained Dredged Material
Massachusetts Institute of Technology,
Cambridge, Massachusetts
Dames & Moore, San Francisco,
California
EEL, MESL
SPL
KMA Research Institute, Mesa, Arizona
Environmental Engineering Consultants,
Inc., Stillwater, Oklahoma
Texas ASM University, College Station,
Texas
USAE Cold Regions Research and
Engineering Laboratory, Hanover,
New Hamshi re
SPL
*WES Waterways Experiment Station
EEL Environmental Effects Laboratory (WES)
MESL Mobility and Environmental Systems Laboratory (WES)
SPL Soils and Pavement Laboratory (WES)
Preliminary and Laboratory Investigations
4A16A
In order to estimate the effectiveness of a densification technique, the
volume the material will occupy if it is placed in the containment area and
nothing is done to densify it must be known. In this work unit, as a part of
another task, a methodology is being developed for determining the capacity
of containment areas when conventional filling and operations are used. This
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methodology will provide the "do-nothing" case and be the datum from which the
effectiveness of the densification techniques can be determined.
5A01
The initial study within Task 5A was conducted in 1973 prior to the
first planning symposium and out of phase with the other studies since it was
a field demonstration of a technique previously used to densify dredged
material. Basically, the technique was to agitate the material continuously
to accelerate the loss of water by evaporation. In the early stages of the
DMRP, it was noted that practically all fine-grained material in containment
areas exhibited a relatively thin crust of dried, firm material underlain by
soft, very wet material. It was assumed that the formation of the crust
effectively sealed underlying material from the evaporation process and,
therefore, that agitating the material would prevent the crust from forming
and allow evaporation to continue. Although there appeared to be a signifi-
cant increase in the rate of dewatering of the agitated material when compared
to material not agitated, the field conditions did not allow rigorous analysis
of the data. Consequently, smaller scale controlled tests (5A02) were per-
formed and followed up by a relatively large-scale test.
5A02
The results of the controlled tests indicated that there was no signifi-
cant difference in the rate of water removal from agitated and non-agitated
fine-grained material. In the areas where the material was not agitated,
desiccation cracks formed and extended to the bottom of the material. It
appeared that the formation of the cracks allowed the evaporation process to
continue at about the same rate as from the agitated material.
These findings still do not answer why, under the field conditions
observed previously, a crust formed and underlying material remained wet for
long periods of time. Upon closer investigation of various sites where the
crust formed, it was observed that the containment area acted as a "bathtub"
and most water in the site could not be removed except by evaporation. It
became apparent that a water table was maintained by recharge from rain or
other sources and that the desiccation cracks in the crust extended only to
the elevation of this perched water table. This was also reported in a review
of tests conducted by private Industry on a fine-grained Industrial waste
(5A03). Results from Work Unit 5A06 also tend to verify the influence of the
perched water table on the formation of the crust. Based on the information
developed from this study, the DMRP no longer recommends continual agitation
to accelerate the dewatering of fine-grained dredged material.
5A03
In this work unit, a review was made of the performance of
conventional dewatering techniques used in soil mechanics and foundation
engineering and techniques used to dewater industrial sludges and slimes.
Results from this investigation indicate that the use of various types of
subdrains fed by gravity drainage or accelerated drainage from applied vacuum
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is feasible. This study also revealed that dewatering low plasticity material
(silt) yielded little additional volume, but significant volume could be
gained by dewatering more plastic material (clays).
5A04
Electro-osmosis is most often used for soil stabilization where small
amounts of water must be removed in a short period of time. Consequently,
large voltage gradients on the order of 1 V/cm are used for relatively short
periods of time (weeks). To dewater dredged material, relatively large
volumes of water must be removed, but normally relatively long periods of
time are available (months to years). This study considered the effects of
using electro-osmosis at low voltages applied continuously or intermittently
for long periods of time. The results of the study indicated that the dredged
material could be dewatered at gradients as low as 0.05 V/cm and that the pro-
cess continued If the voltage was applied intermittently. These findings are
significant since power costs are drastically reduced, thus resulting in the
overall cost of the process being much lower than the cost of the convention-
al electro-osmosis process. Also, the cost could be further reduced by
applying the current intermittently during off peak periods or by generating
electricity from sources such as windmills.
5A05
Although conceptually the forcing of air up from the bottom of the
dredged material would greatly accelerate water removal, the process has
limited feasibility. It is anticipated that the process would be used where
periods between fillings are short and where, because of limited space, water
must be removed in a very short period of time.
5A06
An in-depth study of crust development is presently underway. Since the
crust provided by nature entails no expense and results in a very dense
material, the processes involved in its formation are being investigated and
methods of accelerating crust formation through management of the area are
being developed. A methodology will be provided to predict the rate of crust
formation.
5A07
It 1s a well-known phenomenon that the permeability of a soil is greatly
increased from that of Its natural state by freezing and then allowing it to
thaw. In many parts of the world, dredged material is frozen to a depth of
several feet during winter. If water from the material could be removed
during the spring thaw, significant consolidation would occur. In this work
unit the magnitude of this consolidation is being investigated and methods of
removing the water developed.
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5A10
Probably the most unconventional dewaterlng technique being considered
is the use of capillary enhancement devices or wicks. Wicks provide a path
for water within the dredged material to rise to the surface where it evapo-
rates. Preliminary results indicate that the rate of dewaterlng is acceler-
ated considerably by wicks,
Field Studies
In 1975 the DMRP entered into a cooperative agreement with the Mobile
District of the Corps of Engineers for a full-scale field demonstration of
various densification techniques at the Upper Polecat Bay (UPB) disposal area,
The disposal area is located along the Mobile River in Mobile, Alabama, and
is used to contain material dredged from the main channel and harbor. The
disposal area is approximately 34 hectares in size and contained 2.5 to 3 m
of dredged material in 1975. The site was created in 1970 and dredged
material was placed in the area in 1970 and 1972. The material was predomi-
nantly an organic clay sediment of high plasticity. The foundation material
was very soft. It is anticipated that the Increased effective load resulting
from dewatering the overlying material will consolidate the foundation materi-
al significantly. The consolidation will also result in additional volume
available to contain dredged material. A layout of the demonstration area 1s
shown in Figure 1.
PROGRESSIVE TRENCHING
NORTH SUMP
AND WE IK
SOUTH SUMP
AND WEIR
ISO
150 M
Figure 1. Dredged material dewaterlng field demonstrations, Upper Pole-
cat Bay Disposal Area, U. S. Army Engineer District, Mobile
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When dewatering operations were initiated by the DMRP in August 1975, the
site conditions in all but the southeast corner consisted of a 5- to 15-cm
crust over the soft dredged material. This underlying material had the con-
sistency of warm axle grease and water contents of 1 to 2 times its liquid
limit. About 80 percent of the site was under ponded surface water. Little
vegetation existed.
Ponded water was removed from the site using the Riverine Utility Craft
or RUC (Photo 1). The RUC, a 5440-kg, 6.1-m-long twin helical screw amphibi-
Photo 1. RUC operating in disposal area
ous vehicle, has superior mobility in soil of extremely poor support conditions,
It was originally developed for military purposes to fill mobility gaps
between boats and conventional tracked or rubber-tired vehicles.
The RUC creates two semicircular ruts or trenches as it moves across soft
ground, thereby providing effective drainage channels. Approximately 46 cm of
ponded water was removed from the UPB site and a nearby 97-hectare site in less
than two days using the RUC to trench, cut through high spots, and clean areas
around weirs. It was estimated that the equivalent of several thousand dollars
worth of dragline work was performed under conditions where dragline operation
would have been difficult if not impossible.
As shown in Table 2, a total of seven Task 5A field demonstration work
units as well as one field study in a related task are presently scheduled to
be carried out at the UPB disposal area. The location of some of the
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demonstrations are shown in Figure 1. Each of the techniques will be dis-
cussed and when possible, costs will be estimated.
TABLE 2: DREDGED MATERIAL DENSIFICATION FIELD DEMONSTRATIONS
Work Units
Contractor*
5A08 Densification of Dredged Material by Progressive Trenching
5A09 Consolidation of Fine-Grained Dredged Material with
Windmill-Powered Well Points
5A11 Injection of Sand Slurry into Fine-Grained Dredged Material
5A14 Mechanical Stabilization of Dredged Material
5A15 Dewatering by Underdrainage
5A16 Electro-Osmotic Dewatering Field Study
5A18 Vegetation Dewatering
2C09 Field Evaluation of Equipment for Operation in Containment
Areas
EEL
Mobile District, EEL
SPL, EEL
EEL, MESL
SPL
Mobile District (L. Casagrande
and C. E. O'Bannon, Consultants)
Dauphin Island Sea Laboratory
MESL
*WES
EEL
MESL
SPL
Waterways Experiment Station
Environmental Effects Laboratory (WES)
Mobility and Environmental Systems Laboratory (WES)
Soils and Pavement Laboratory (WES)
5A08
This work unit being conducted over the center 24 hectares of the site is
concerned with determining the effect of progressive trenching on the drying
and drainage rate of fine-grained dredged material. The beneficial effects
will result from rapidly removing precipitation, lowering the perched water
table, and promoting desiccation and surface crust formation. Equipment used
in the trenching study has included the RUC (with and without implements), an
amphibious dragline, and a conventional dragline on mats. Starting from the
conditions described earlier, the progressive trenching so far has resulted in
the development of a surface crust from 0.5- to 1.5-cm thick.
5A09
A 6-kw windmill with a three-bladed 5-m-diameter prop located on a 12-m
tower is being used to provide electricity to run vacuum and water pumps in an
attempt to dewater and consolidate fine-grained dredged material with vacuum
well points. It is believed that dewatering constraints inherent in the
relatively low hydraulic permeability of dredged material slurry may be some-
what nullified by relatively long-term dewatering, as opposed to more conven-
tional short-term dewatering uses of vacuum well points. The wind-powered
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generation system has been found to provide effective power with a 63.5 cm Hg
vacuum being developed 1n the well point system and a flow of approximately
3.7 &/hr from each well point.
5A11
This work unit, carried out in February 1976, was a small-scale demon-
stration of hydraulically fracturing in-place dredged material by pressure
injection of sand grout. Fracturing at foundation level was expected to pro-
duce horizontal fans that would, in effect, produce underdrainage layers in
existing masses of fine-grained dredged material. The resulting drainage
layers could then be pumped, providing both water table drawdown and vacuum
consolidation in the dredged material mass. The field demonstration was a
success: 2.5 cu m of grout were placed under a 23- by 15-m area and horizontal
grout fans were produced. Pumping tests on the injected sand slurry with
63.5 cm Hg vacuum yielded flows of 11.5 Jl/hr per well point as compared to
0.6 £/hr from conventional sanded well points installed for comparison. Only
0.5 m excess head of sand grout was needed to fracture the material at the
2.5-m depth. Consequently, only a pipe and funnel were needed to inject the
grout rather than the conventional pressure grouting equipment. Additional
pumping of the sand-injected layers is currently underway.
5A14
This study is concerned with improving the drying rate of dredged
material slurry by periodically mixing the surface crust with the underlying
soft dredged material, allowing the crust to reform, then remixing, etc. The
process should not be confused with the technique described in Work Unit 5A01.
The process is not unlike mechanical stabilization of a highly plastic clay
by introduction of coarse-grained cohesionless material. This study has been
underway since February 1976. Preliminary data indicate that the periodically
mixed area is drying about 15 percent faster than an adjacent control area.
5A15
This work unit is designed to evaluate the effects of conventional
hydraulic drainage techniques (i.e., sand layers with collector pipe) for
dewatering fine-grained dredged material slurry. Five miniature diked areas
are being constructed on the stable dredged sand at the southeast corner of
the disposal area. After underdrainage layers are placed, highly plastic
organic clay dredged material slurry will be pumped into the test areas and
the rate of dewatering and drying will be evaluated. One area will be used
as a control section while the other four areas will be used to evaluate the
concepts of simple gravity underdrainage, vacuum-assisted underdrainage,
seepage consolidation, and seepage consolidation with vacuum assistance.
5A16
This study is the follow-on to the laboratory studies of long-term low
voltage gradient electro-osmotic dewatering conducted under 5A04. Although
the laboratory studies indicated electro-osmosis was apparently technically
and economically feasible, the field demonstration will provide valuable
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operational data so that the process can be refined under realistic conditions.
5A18
This study is designed to investigate the use of vegetation in providing
desired engineering characteristics in disposal areas. Engineering criteria
to be satisfied by the vegetation include the ability to dewater the surface
of dredged material slurry rapidly and the ability to form a root mat rapidly
that is capable of supporting men and equipment.
The use of vegetation for dewatering dredged material is also being
evaluated in a field study on Grassy Island in the Detroit River. In this
test the common reed PhJiagmutitA commuyuA was planted prior to placement of the
dredged material and allowed to grow. The dredged material was placed so that
the plants are almost completely inundated. The plants will send out roots or
rhizomes up and down the stalk, dewatering the dredged material throughout the
total depth.
2C09
Although this work unit is under Task 2C, the field evaluations of equip-
ment are being conducted at the UPB site. Results of this work unit are
directly applicable to work in Task 5A because of the equipment demands for
the systems being evaluated. This work unit is concerned with selection and
evaluation of both experimental and conventional equipment to perform trench-
ing, earthmoving, and survey and reconnaissance tasks in confined disposal
areas. Equipment to be evaluated include low-ground-pressure vehicles, such
as the RUC and other military personnel carriers, as well as marsh buggies,
backhoes, gradalls, draglines, and dozers, with and without special tracks and
operating on and off of matting.
TREATMENT OF CONTAMINATED DREDGED MATERIAL
Background
Investigations of treatment methods for contaminated dredged material are
being conducted within the DMRP Task 6B (Treatment of Contaminated Dredged
Material). Work within this task includes treatment schemes for dredged
material discharged in open-water and confined in diked containment areas.
Work units of Task 6B are shown in Table 3.
Preliminary and Laboratory Investigations
6B01, 6B02
Two preliminary studies were conducted to examine the adequacy of certain
parameters commonly used to describe the pollution potential of dredged
material, to assess conventional treatment methods, and to recommend applicable
treatment schemes.
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TABLE 3: TREATMENT OF CONTAMINATED DREDGED MATERIAL STUDIES
Work Units
Contractor
6B01 Assessment of Chemical, Physical and Biological Processes
for Treatment of Dredged Material
6B02 Laboratory Treatability Studies of Polluted Dredged
Material
6B05 An Evaluation of Oil and Grease Contamination Associated
with Dredged Material
6B06 Oxygenation of Dredged Material
6B07 Flocculation as a Means for Improving Effluent from
Confined Disposal Sites
6B08 Development of Design Procedures for Flocculation
of Dredged Material
6B09 Field Evaluation of Vegetation for Removal of
Contaminants from Effluent from Confined
Disposal Areas
JBF Scientific Corporation,
Wilmington, Massachusetts
EEL*
Engineering Science, Incorporated
Austin, Texas
JBF Scientific Corporation,
Wilmington, Massachusets
University of Southern California
Los Angeles, California
EEL
Savannah District
(H. L. Windom, Consultant)
* Waterways Experiment Station Environmental Effects Laboratory
Both studies showed that bulk analysis methods of evaluating the charac-
teristics of dredged material do not adequately assess the environmental
effects of dredged material disposal. The studies also indicated that many
conventional wastewater techniques are frequently inapplicable and/or impracti-
cal because the dredged material slurry generally presents a relatively high
solids content, a high magnitude and variability of flow, and a complex makeup
of physical and chemical properties and organic matter. The studies demon-
strated that biological treatment techniques are ineffective, but that chemical
coagulation treatment procedure could be employed to reduce suspended solid
and the attached contaminants.
Rapid oxygen depletion in the water column is one of the most documented
and noticeable effects of open-water disposal of dredged material. During the
laboratory studies it was shown that depletion of dissolved oxygen (DO) can be
appreciably reduced by aerating the slurry. Both studies recommended field
tests to evaluate the feasibility of injecting air or oxygen into the pipeline
to reduce the oxygen depletion within the water column. Field tests were con-
ducted and they will be discussed subsequently.
6B05
A study was initiated to investigate problems of oil and grease associat-
ed with confined disposal areas. Preliminary results indicate that oil and
grease contamination does not appear to be a significant problem. Oil and
grease generally are not released from the sediment during the dredging
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process. The second phase of this study was designed to develop treatment
processes for the removal of oil and grease from disposal area effluents.
Since the field survey results indicate that oil and grease concentrations in
the effluent are so low that treatment will probably not be required, the
scope of this phase was changed. Now, bench-scale studies will be conducted
to confirm the field findings and to determine factors that may affect oil and
grease release.
6B07, 6B08
The use of flocculants to improve the quality of effluent from confined
disposal sites is being investigated under these work units. Most contami-
nants appear to be tied up with suspended solids in the effluent. Consequently,
removal of the suspended solids should improve the quality of the effluent.
Work being conducted under Work Unit 6B07 is investigating dosages of
flocculants needed and the resulting quality of the effluent. Work under Work
Unit 6B08 is developing methods for implementing the results of 6B07 under
field conditions. Both of these work units are currently active.
Field Tests
Two major field tests have been or will be conducted as part of Task 6B:
one to investigate injection of air and oxygen into dredge pipelines to reduce
the immediate oxygen demand during open-water disposal of dredged material and
the other to evaluate the effectiveness of vegetation in removing contaminants
from dredged material in confined disposal areas and thus to improve the
effluent water quality.
6B06
Field tests were conducted to evaluate the effectiveness of injecting
oxygen and air into the pipeline during open-water disposal operations.
Oxygen was injected into the pipeline of a 41-cm dredge while air was injected
into the pipeline of a 61-cm dredge. The tests using air were conducted in
December of 1975 and the tests with oxygen were just completed.
The oxygenation tests were conducted in Apalachicola Bay, Florida. The
water in the area was about 1.8 m deep with a natural dissolved oxygen (DO)
value of about 10 mg/fc. During disposal operations the DO was depressed to
1 to 2 mg/Jl near the bottom and 3 to 4 mg/5, near the surface and at mid-depth.
When oxygen was injected into the system, the DO near the bottom and at mid-
depth was increased to about 5 mg/Jl. No significant change was noted at near
surface. Data from the aeration tests conducted in Mobile Bay, Alabama, are
currently being analyzed.
6B09
Field tests are currently in progress to evaluate the ability of
vegetation to remove contaminants from dredged material and thus improve the
water quality of effluents from containment areas. The tests are being con-
ducted at an active disposal site in Savannah, Georgia. The tests are being
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performed to assess the capability of SpcwUm att&iw4&o*A to remove nutrients
and heavy metals from the effluents. The site consists of twelve 3-m-wide and
100-m-long runways within the grass. The effectiveness of the grass for re-
moving contaminants will be monitored at various flow rates and distances from
the discharge point. These tests will provide general information on the con-
cept. It is realized that more controlled tests will be necessary using
various types of vegetation and chemical compositions of effluent to provide
a complete design methodology.
CONCLUDING REMARKS
The preceding discussions of research being conducted as part of the
Disposal Operations Project have been general with few details given. Since
research is in progress, definitive information is not yet available on all
aspects of the work. This information is coming in at a high rate and will
be analyzed and dissiminated as soon as possible. Summaries of the results
of DMRP studies are usually published in the DMRP Information Exchange
Bulletin several months before the final report is published. All studies
will be completed and final results published in mid-1978.
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ECOLOGICAL CONSIDERATIONS IN SITE ASSESSMENT FOR
DREDGING AND SPOILING ACTIVITIES
Donald K. Phelps and Allen C. Myers
Environmental Research Laboratory
U.S. Environmental Protection Agency
South Ferry Road
Narragansett, Rhode Island 02882
INTRODUCTION
Dredged materials may contain toxic substances whose effects upon the
marine ecosystem are poorly understood. Does ocean disposal of such material
have adverse environmental impact? If so, is the degree of impact great
enough to justify additional economic burdens that result from:
1) Moratoria on ocean disposal of dredged material resulting from legal
actions on the part of environmentalists?
2) Developing alternative methods of disposal that may ameliorate or
modify negative effects on the total ecosystem?
3) Development of new or improved technology for the disposing of spoils
containing toxicants into ocean systems?
The development of criteria for establishing the acceptability or not
for the disposal of dredged materials from marine systems which contain
toxicants resulting from a history of man's activities into clean marine
areas is extremely important. Given the diversity of coastal marine and
estuarine environments, it is unlikely that any single set of dredging and
spoiling site criteria can be developed for direct application to all situa-
tions. The problems of concern are potential long-term effects on the bottom-
dwelling biota of the dredging and dumping of contaminated materials near or
in an uncontaminated area. A basic assumption is that healthy benthic commun-
ities—whatever their direct economic benefit to humans--are absolutely
necessary for the continued function of coastal and estuarine ecosystems.
It is the purpose of this paper to report on a series of studies that
have been underway at the Environmental Research Laboratory, Narragansett,
Rhode Island, to provide some specific insight into areas of general concern.
The primary focus of the studies has been aimed at trying to identify methods
that singly or in combination give the most expeditious yet meaningful demon-
stration of possible negative environmental impacts resulting from the dis-
posal of contaminated sediments into clean marine systems.
The basic structure of this study is comparison. Comparisons have been
made between sediments, fauna! diversity, and animal tissue residues between
266
-------
highly contaminated and clean benthic systems. The nature of the area of
study is such that a series of field stations along a gradient of benthic
systems ranging from highly contaminated to a clean system proved helpful.
Animals and sediments have been brought from the field into the labora-
tory for a series of comparative analyses. The nature of flux from each
sediment extreme was measured in a "neutral" water column provided by the
seawater system in the laboratory. Responses of the same animal species from
each extreme to additional laboratory stress has formed the basis of the
development of comparative bioassay as a means for measuring potential impact
of contaminants in benthic systems.
AREA OF STUDY
The primary focus of this study is Narragansett Bay, Rhode Island (Figure
1). The Bay has been described "abnormally stressed" in its upper reaches
and as being divisible into a polluted upper Bay, a transitional zone, and a
lower Bay having water of high quality. Bottom water salinities range from
28-31 °/0o in the upper reaches and from 30-32 °/00 in the lower Bay.
Temperature escalates from freezing to 22°C throughout the estuary.
The major environmental difference within the system is due to a history
of pollution effects in the upper reaches of the Bay. Sources of pollution
are domestic waste treatment plants and industrial effluents including metal
plating and jewelry manufacturing activities.
Fine sediments in the upper area are anaerobic, characteristically
having their redox boundary at the sediment-water interface and having a
strong odor of H2S. In the lower Bay, fine sediments have a well-defined
aerobic layer with a redox boundary defined between 50 and 10 cm below the
sediment-water interface. Metals in upper Bay sediments include elevated
levels of Zn (250 ppm) and Cr (241-363 ppm) compared to lower Bay levels of
12-20 ppm Zn and 57 ppm Cr, respectively. High concentrations of hydrocarbons
have been reported in upper Bay sediments compared to levels found in the
lower Bay. The upper reaches of the Bay are dredged periodically to maintain
shipping channels for the port of Providence.
SUMMARY AND DISCUSSION OF RESULTS
A transect of stations progressing from contaminated to clean benthic
systems was studied in Narragansett Bay, Rhode Island (Figure 1). Sediment
box cores collected from either end of the transect were brought into a
"neutral" water columm provided by the flow-through seawater system and held
for four months with flow-through rate of 4 liters/min.
Flux of ammonia and metals from the box cores were monitored in the
laboratory. Fluxes observed from the contaminated sediments continued to be
significantly higher than those observed from uncontaminated sediments
(Tables 1-6).
These results demonstrate that a contaminated sediment disposed of in a
clean environment will tend to degrade quality of the overlying water column.
267
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Providence
NARRAGANSETT BAY
RHODE ISLAND
POLLUTED,*!
UPPER BAY/.
.
Providence
River
Greenwich Bay
Mount Hope
Bay
TRANSITION
ZONE
Sakonnet River
LOWER-
BAY • *r.
Figure 1. Area of study.
268
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TABLE 1. FLUX RATES OBSERVED FROM LABORATORY-HELD BOX CORES
NH3 IN MICRO MOLES/CM2/DAY
Dates
1976
1/7
3/31
4/20
4/21
Temp.
°C
2.8
6.6
11.9
21.3*
Sabin
Point
0.10
0.20
0.35
0.93
Jamestown
0.01
0.09
0.08
0.38
Ratio Sabin Point:
Jamestown
10
2.22
4.38
2.45
TABLE 2. FLUX RATES OBSERVED FROM LABORATORY-HELD BOX CORES
BOD IN M6/CM2/DAY
Dates
1976
3/2
4/8
2/9
4/8
Temp.
°C
5.4
8.5
10.3*
20.2*
Sabin
Point
0.07
0.073
0.142
0.289
Jamestown
0.05
0.054
0.145
0.174
Ratio Sabin Point:
Jamestown
1.20
1.33
.98
1.66
TABLE 3. FLUX RATES OBSERVED FROM LABORATORY-HELD BOX CORES
MANGANESE IN yG/CM2/DAY
Dates
1976
3/2
4/8
2/9
4/8
Temp.
°C
5.4
8.5
10.3*
20.2*
Sabin
Point
.214
.292
.378
1.542
Jamestown
.178
.026
0.148
0;406
Ratio Sabin Point:
Jamestown
1.20
11.64
2.56
3.79
269
-------
TABLE 4. FLUX RATES OBSERVED FROM LABORATORY-HELD BOX CORES
CADMIUM IN yG/CM2/DAY
Dates
1976
3/2
4/8
2/9
4/8
Temp.
°C
5.4
8.5
10.3*
20.2*
Sab in
Point
0.031
0.033
0.023
0.059
Jamestown
0.052
0.024
0.035
0.016
Ratio Sabin Point:
Jamestown
0.59
1.40
0.66
3.64
TABLE 5. FLUX RATES OBSERVED FROM LABORATORY-HELD BOX CORES
ZINC IN yG/CM2/DAY
Dates
1976
Temp.
°C
Sabin
Point
Jamestown
Ratio Sabin Point:
Jamestown
3/2
4/8
2/9
4/8
5.4
8.5
10.3*
20.2*
0.591
0.289
0.515
0.407
0.641
0.300
0.098
0.240
0.92
0.96
5.27
1.70
TABLE 6. FLUX RATES OBSERVED FROM LABORATORY-HELD BOX CORES
COPPER IN yG/CM2/DAY
Dates
1976
O/9
61 C.
4/8
2/9
4/8
Temp.
°C
c; &.
o . t
8.5
10.3*
20.2*
Sabin
Point
0.012
-0.153
0.027
Jamestown
0.009
-0.133
0.029
Ratio Sabin Point:
Jamestown
1.36
-1.15
0.95
270
-------
While dilutional effects may tend to render this degradation insignificant at
an undefined distance above the sediment surface, such a flux would exert a
significant negative impact at the sediment-water interface.
It may be inferred that the benthic system, once contaminated, provides
a major reservoir of contaminants which continue to be exchanged with the
overlying water column. A feedback loop of major environmental significance
is thereby identified. Regardless of the initial route of transport, whether
the media is the water column itself or particulate and/or colloidal scaveng-
ing within the water column, the benthic system appears to be the reservoir
of greater contaminant concentration. This point is basic in the use of
biota as environmental integrators and indicators or predictors. In order to
use biological magnification by biota effectively as a de facto demonstration
of the biological availability of contaminants present in dredge spoils, it
must first be established that the sediments are the more significant reser-
voir and provide a media of biological transport for those contaminants into
the overlying water column at a proposed dredge site.
Tissue residue analyses, or total body burden measurements, for some
trace metals demonstrate that the levels of metals accumulated by benthic
macrofauna and the degree to which the total number of animals within a given
population exhibit such accumulation appear to vary as a function of the
vertical position in the water column-sediment profile at which the animals
feed. Macrobenthic fauna were collected along a transect within the contamin-
ated sedimentary system of upper Narragansett Bay at one point in time.
Fauna were grouped according to the vertical position within the sedi-
ment-water profile from which they feed. Mercenaria mercenaria, Mulinia
lateral is, Ensis directus, and Mya arenaria were included in a group classi-
fied as "Water Column Feeders" (WCF) which secure purchase on or in the
substrate but feed from the overlying water column. The WCF are all molluscs
in this instance.
Two polychaetous annelids, Nephtys incisa and Glycera dibranchiata,
compose the "Subsurface Feeders" (SF). Members of this group actively
burrow and feed below the sediment-water interface.
The third and final group is composed of fauna which feed directly from
the sediment-water interface or the "Interface Feeders" (IF). The IP's
include a polychaete worm, Pherusa affinis; two Crustacea, Paleomenetes pugio
(the grass shrimp) and Rithropanopeus harisii (the mud crab); as well as two
molluscs, Yoldia limatula and Nassarius obsoletus.
Chromium (Cr), silver (Ag), and zinc (Zn) were measured in total body
tissue (molluscs minus their shells) for each animal in each group using
neutron activation analysis.
The metal analyses yielded two sets of information (as shown in Figure 2)
1) The percent of total number of animals (from each group) having
detectable levels; and
2) a comparison of relative metal accumulation between the groups.
271
-------
CR
AG
ZN
ro
»j
ro
70
63
56
49
42
35
28
21
14
7
0
SUBSI
N'
8
INTER
JRFACE
= 2 N =
1% 5C
WA
COLl
rRCE [
9 N =
)% 61
FER
JMN
INTEF
H
SUBSURFACE
_j
JFACE
1 WA1
COL
•
600
540
480
420
360
300
PER
JMN240
B
IOU
""" 120
J 60
' 1 N = 2 N=I4 N=IO
% 8% 78% 56%
SUBSUF
^ • •
Li
N^
I0(
INTER
?R\CE
• • ^
FACE
WA
COL
TER
JMN
•
•1
:2I N = I7 N= 8
D% 100% 100%
Figure 2. Levels and incidence of occurrence of chromium, silver, and zinc in benthic
fauna grouped according to feeding positions.
-------
Of the three animal groups, the SF's had the lowest accumulation of the
three metals. Cr and Ag analyses yielded only an 8% incidence of detection
in the SF group. This indicates that the group is the least useful in terms
of biological integrator or monitoring of contaminated benthic systems.
The WCF's showed the highest level of incidence within the population
monitored (61%) and the highest levels of accumulation for Cr. This group
showed lower levels of incidence in the case of silver (56%) and accumulation
for both silver and Zn than did the IF's.
The IF's showed a 78% level of incidence for Ag and the highest level of
accumulation for both Ag and Zn.
i
All three groups showed a 100% level of incidence for Zn.
These data indicate that the IF's are the most useful group in terms of
biological integration and hence monitoring for those contaminants in dredge
spoils which are biologically available. This fact takes on greater signifi-
cance in view of the results from laboratory box core studies described
above. Measurable degradation of the water column at the sediment-water
interface resulting from the flux of NH3 and metals through that interface
was demonstrated.
WCR's are the better apparent choice for Cr. These results also indicate
that they would be useful as integrator-monitors for Ag and Zn as well, but
less effective than IF's.
Field observations indicate that, in the contaminated benthic systems of
Narragansett Bay, dominance of feeding types shifts in numbers and biomass to
the WCF's at the expense of the IF's and SF's which dominate the clean benthic
systems of lower Narragansett Bay. This observation suggests that while the
IF's may be the best monitor, the group may also be quite sensitive to effects
of materials being released from contaminated sediments.
The reduction in numbers of IF's and SF's has a marked effect on the
physical system. These animals, through their active burrowing and/or feeding
activity, mix the sediments mechanically. Such mechanical mixing contributes
to aerating surface sediments. As the animals and their mechanical mixing
activity decrease, the redox potential discontinuity migrates closer to and
eventually meets the sediment water interface.
The Rhoads Interface Camera, which takes a picture of a sediment profile
including the sediment-water interface, is an excellent piece of remote
sensing gear. From these pictures, the depth of the RPD (redox potential
discontinuity), sediment penetrability which reflects animal activity such as
reworking, animal tubes, and burrows can be measured and read. Applied to
the transect, the camera allowed us to demonstrate that the RPD approaches
the sediment surface as one moves up the bay; further, that the sediment
penetrability increases in the same direction. We are currently evaluating
other kinds of information which can be inferred from the interface photo-
graphs.
273
-------
A gross measure of animal diversity, expressed simply as the total
number of species collected per unit measure of surface area, primarily
reflects the reduction in numbers of IP's and SF's referred to above. A
transect including six stations ranged from clean areas of Narragansett Bay
(stations 1, 2, 3 and 4) into areas having sediments of higher levels of
contamination (stations 5 and 6) (Figure 1). Stations 1 and 6 are the sta-
tions from which the "clean" and "contaminated" box cores, used in the labora-
tory flux experiments, were respectively collected.
Total numbers of species are listed for each season (Table 7). Stations
5 and 6, within the Providence River, have much lower numbers of species than
stations 4, 3, 2 and 1, which are located outside it. Moreover, though the
two end stations, 1 and 6, have only four species in common in the fall, they
have 11 species in common the following spring due to an influx of juveniles
into both stations. At station 1, some of these juveniles may be killed by
trophic group amensalism during which deposit feeders push out the filter
feeders. At station 6, observations suggest that most species are killed off
by late summer conditions. The fact is established that, for larvae at the
settling stage, both stations offer "acceptable" sediment. This material
represents only a preliminary report on the data collected.
TABLE 7. NUMBERS OF SPECIES IN QUANTITATIVE INFAUNAL SAMPLES AT EACH OF
6 STATIONS FROM THE PROVIDENCE RIVER (6) TO MID-NARRAGANSETT
BAY (1), BY SEASON
Station
Season 654321
July 1975
January 1976
June 1976
5
12
20
10
18
19
29
18
18
25
19
28
22
24
30
An initial study of tissue residues on total body burden measurements
for cobalt, iron, and zinc was made on Mercenaria mercenaria distributed
throughout Narragansett Bay. Two statistical populations of this water-
column-feeding mollusc were identified on the basis of those levels of metals
contained in their tissues (Figure 3). One population, which has significant-
ly higher levels of some metals, occurs from the upper portion of Narragansett
Bay and into the Providence River (Figure 1). The statistical population
found in the clean lower Bay (Figure 1) is characterized by lower metal
levels. Those M^ mercenaria having higher metal levels are also characterized
by the presence of dark pigment which infuses the tissues, as well as signifi-
cantly higher levels of yellow-staining amoebocytes and development of black
concretions in the,kidneys as evidenced by histopathological examination.
More intensive collections of M_. mercenaria were made at stations representing
areas typical for the occurrence of each statistically identified population.
Sabin Point and Fox Island were the stations where collections were made
(Figure 1). The metals analyzed were expanded to include chromium (Cr),
cadmium (Cd), silver (Ag), copper (Cu), lead (Pb), and nickel (Ni), as well
274
-------
ro
^4
tn
700
630
r UPPER BAY
o
cr
o
E
o»
560
490
1*420
o 300
i
o
E
280
210
140
o»
c 70
N
UPPER BAY
LOWER BAY
ZINC
LOWER BAY
L N=35
= 28
IRON
N=35 N=23
4.0r-
3.6
3.2
2.8
£ 2.4
g2.0
1-6
o 1.2
0.8
0.4
- UPPER BAY
QL-
UDWERBAf
COBALT
N=35 N=24
Figure 3. Levels of zinc, iron, and cobalt in grouped samples of Mercenaria mercenaria
from Narragansett Bay, Rhode Island.
-------
as including zinc (Zn) and cobalt (Co) which were measured in the initial
study. Results (Figure 4) indicate significantly elevated levels of Cr, Zn,
Cd, Cu, Pb, and Ni in M_. mercenaria collected from contaminated sediments, as
compared to those collected from clean sediments. No significantly elevated
differences were demonstrated between the two M^ mercenaria populations in
the case of Ag and Co.
Two basic questions were generated from these results:
1) Would those Mercenaria having higher metal levels depurate those
metals if held in clean water for a reasonable time period?
2) If higher levels of metals were retained, do those M^ mercenaria
having higher levels exhibit differences in physiological responses?
Samples of Mercenaria having elevated levels of metals and the group
having apparently lower were collected from Sabin Point and Fox Island,
respectively, and brought into our laboratory seawater system. They were
held for a period of 30 days in ambient temperatures of 24°C ± 3°C. At the
end of that time, soft tissues were removed from the shells and analyzed by
atomic absorption analyses for the metals identified above. Ambient tempera-
ture levels were optimum for Mercenaria pumping and feeding roles.
The results identify three types of conditions in the Mercenaria metal
relationship:
1) That condition in which metals are retained in Mercenaria collected
from contaminated ("dirty") sediments at statistically higher levels
than in those Mercenaria collected from uncontaminated ("clean")
sediments after 30 days depuration in a neutral system (Group I,
Figure 5). This group includes the metals Cd, Cu, Ni, Pb, and Ti.
2) The second situation is that in which there was no measurable
difference in metal levels between the "clean" and "dirty" Mercenaria
before or after depuration. Metals falling into this group (Group
II, Figure 6) include Mn, Zn, V, and Co.
3) The third and final situation is demonstrated by Group III (Figure
7). In this instance metals which were significanlty higher in
"dirty" Mercenaria were in fact depurated to a level comparable to
"clean" Mercenaria after 30 days. Two metals, Ag and Al, compose
this group.
In the case of the Group I metals, the data indicate a strong probability
that bioconcentration is taking place. Mercenaria are concentrating some
potentially toxic metals (Cd and Pb especially) from contaminated sediments.
They are making those materials available for biomagnification throughout the
food chain. Mercenaria are consumed directly by man. Dredging of contamin-
ated sediments and disposing of them in an area where commercial harvesting
of Mercenaria is taking place could pose a reasonably serious threat to man
as a consumer. Copper reached levels in "dirty" Mercenaria five times greater
than in "clean." Cadmium, Pb, Ni, and Ti levels were three times greater in
the "dirty" Mercenaria. Group I metals should be given high priority for
purposes of monitoring.
276
-------
IOOO
100—
X
o
LU
a.
a.
1.0—
Cr
99%
Zn
95%
Cd
99%
Ag
NS
Cu
99%
Pb
Ni
DIRTY
C
99%
99%
Co
NS
0,1-
Figure 4. Comparisons of metal levels between Mercenaria mercenaria from contaminated ("dirty") and
uncontaminated ("clean") sediments from Narragansett Bay, Rhode Island.
-------
iooo-d
100—\
CD
UJ
*io-
(T
O
CD
Q_
Q.
1,0—1
GROUP 1
I I 1
DIRTY MERCENARIA A = UNDEPURATED
CLEAN MERCENARiA
B = DEPURAT
B
Cd
B
Cu
B
Ni
A B
ID
A B
Pb
Ti
MERCENARIA
Figure 5
278
-------
GROUP H
100 —
h-
X
o
LU
10
a:
Q
QL
Q.
1,0-
0,1
B
B
DIFTTY MERCENARIA
CLEAN MERCENARIA
A= UNDEPURATED
B= DEPURATED
Mn
Zn
B
A
B
V
Co
MERCENARIA
Figure 6
279
-------
GROUP m
100
h-
10—
(X
Q
QL
a.
1.0 —
O.I
DIRTY MERCENARIA
CLEAN MERCENARIA
A= UNDEPURATED
B= DEPURATED
B
Ag
B
Al
MERCENARIA
Figure 7
280
-------
Of the Group II metals, Mn, Zn, and Co have been detected in signifi-
cantly higher levels in contaminated upper Bay sediments. The fact that
Mercenaria do not reflect such elevated levels in their tissues may be due to
the fact that the metals are fluxed from the sediments (as demonstrated in
the case of Mn and Zn) in a state that may render them biologically unavail-
able or that these molluscs regulate those metals biologically. No informa-
tion is available for V levels in sediments. At any rate, Group II metals
are of little use for monitoring purposes in this instance.
Group III metals, Ag and Al, depurate from "dirty" Mercenaria to lower
Bay levels within the 30 day period. Apparently, those metals, when initially
detected, were part of the gut content and were subsequently eliminated.
Monitoring for these metals may give insight into movement from disposal
sites. While they may not be biologically available, their presence in the
Mercenaria indicate movement through or from a system of greater concentration
to lesser concentration and probably in a particulate state.
Mercenaria were collected from the same upper and lower Bay stations
described previously to conduct another experiment designed to see if the
high metal and low groups responded differently.
Metal uptake under laboratory conditions was decided upon as a reasonable
measure for response. A wide range of reactions are involved in the uptake
of metals. Simple processes such as valve opening and closing and through
complex biochemical exchange reactions are bracketed in such an uptake study.
Clams from each location were placed in a series of tanks having radio-
active 65Zn alone, 65Zn plus Ag, and 65Zn plus Cu. Three clams were taken
from each group and 65Zn measured and compared at the end of 2, 4, 8, and 16
days, respectively.
Results are as follows:
The uptake pattern for Zn alone was very different between the two
groups. "Dirty" clams had taken up more than twice as much of the 65Zn by
the end of the experiment (Figure 8).
Animals exposed to the combination of 65Zn and silver demonstrated a
basic similarity in the uptake pattern; but "dirty" clams had a higher uptake
of 65Zn at the end of the experiment also (Figure 9).
The most dramatic difference was in the exposure of 65Zn in combination
with Cu. While uptake patterns were somewhat similar, the highest 65Zn
uptake level of all occurred in the "dirty" clams of this experiment in the
presence of Cu (Figure 10).
The previous depuration experiment demonstrated a real bi concentration
of five times the Cu level in "dirty" over "clean" clams. The next question
is__is the different uptake level of 65Zn in the presence of Cu demonstrated
in this experiment due to the existing body burden of Cu in the "dirty"
experimental animals? This is a question to be answered by further research
efforts.
281
-------
18
16
UPTAKE OF ZINC
I I I I I I I I I I I I I I I
CLEAN MERCENARIA
DIRTY MERCENARIA
14
o
z
N
12
CL
CL
10
0
A
I I I I I I 1 J I I I I I I
8
10
12
14 DAYS
Figure 8
282
-------
18
UPTAKE OF ZINC IN PRESENCE OF SILVER
~~lI I I I I T"l I I I I I I T
16
CLEAN MERCENARIA
DIRTY MERCENARIA
14
12
10
I I I I I I I I I I I I I I I
0
8
10 12
14 DAYS
Figure 9
283
-------
20
UPTAKE OF ZINC IN PRESENCE OF COPPER
"1 I I I I I F~l I I I T
18
CLEAN MERCENARIA
DIRTY MERCENARIA
16
14
I J J _1 I I I I I I I I I I I
0
8
Figure 10
284
10
12
14 DAYS
-------
The upper Bay population behaved differently. It may be deduced that
the different behavior results from a combination of impacts stemming from
man's pollutional contributions to the upper Bay systems.
While the "dirty" clams have higher metal levels, they also have higher
hydrocarbon levels. They have demonstrated differences in response and have
distinctly different histophathological histories as well. They even look
different. Obviously, specific cause and effect mechanisms are well buried
in this multi-stressed population.
While Mercenaria are WCF's and studies described above indicate that
IP's should be the biological monitors of choice, only Mercenaria are ubiquit-
ously distributed throughout the Bay. This fact added to the fact that
Mercenaria live for periods exceeding two years made them the biological
monitors of choice in the proceeding two experiments.
RECOMMENDATIONS
Data presented in this paper demonstrate that metals and other materials
(such as NH3) continue to be fluxed from contaminated sediments upon reloca-
tion or redeposition into a "clean" discharge site. Fluxed materials are
taken up in various levels and combinations by a variety of macrobenthic
fauna. The position at which fauna feed and ventilate (in a vertical profile
through the sediment-water interface) is related to the kinds and amounts of
materials which are accumualted by them.
Mercenaria having significantly higher levels of certain metals in their
tissues demonstrate different uptake patterns and levels when exposed to
additional amounts of those same metals in the laboratory under a parallel
bioassay run simultaneously with Mercenaria having significantly lower amounts
of metals. This fact provides an initial indication that response mechanisms
differ between the same species (Mercenaria in this case) living in contamin-
ated and uncontaminated benthic systems.
It is recognized that while Mercenaria having higher tissue levels of
metals respond differently from the same species having lower tissue residues,
no cause and effect relationship has been established.
It is therefore recommended that:
1. Heavy metal tissue elevations resulting from exposure to contaminated
sediments be examined for use as a tag for a variety of possible stres-
sors coming from contaminated sediments. For example, it is known that
Mercenaria having higher tissue residues of metals have a variety of
other problems that are associated with contaminated sediments. These
include elevated levels of total petrochemical hydrocarbons (reported in
the literature), histopathological, parasitological, and biochemical
abnormalities. However, for purposes of monitoring, good metal analyses
are more reliably carried out at much lower cost in currency and exper-
tise than are analyses for petrochemicals and other organics of interest
or than are sophisticated histopathological, parasitological, or biochem-
ical analyses. Another profitable avenue for research may be the examin-
285
-------
ation for possible direct relationships between metal levels and the
presence and possible quantity of other contaminants in the tissue of
fauna living in contaminated sediments.
Parallel bioassays should be run between fauna collected from sediments
that are of questionable and known quality before those sediments be
disposed of in clean systems. The parallel bloassay can be used as a
direct demonstration of possible negative environmental impact on biota
from contaminated sediments. Other types of responses than the metal
uptake approach, used in this study, should be examined. For example,
we are currently looking for differences in feeding rates and carbon
fixation between Mercenarla from contaminated and uncontaminated sedi-
ments. We intend to examine different responses that additional stress
may elicit from these parallel populations. We believe that fauna
living in contaminated sediments provide valuable insight into the
effects that those sediments will have on similar fauna living in a
"clean" site that may be proposed for dredge disposal. A direct demon-
stration of possible negative environmental impact due to disposal of
contaminated sediments may be outlined by a series of judicious compari-
sons made on the basis of biological responses and tissue residues.
286
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APPENDIX A
Notes on the units of measure and methodology used by Japanese authors.
(1) Taisuke Sameshima--
(2) Tomonri Ohtsuka--
(3) Akio Murakami--
(4) Motoo Fujiki et al.--
(5) Hiroaki Egawa
and Shizuko Tajima-
(6) Ken Murakami
and Kazuo Takeishi-
(7) Tatsuo Toshida
and Yoshikazu Ikegaki-
(8) Shingo Fujino--
(9) Tatsuro Okumura—
(10) Eisuke Satoh--
Concentrations of toxic substances in
sediment reported in the original manu-
script as ppm were converted to mg/kg (dry
weight).
Concentrations of toxic substances in sea
water reported in the original manuscript
as ppm were converted to mg/1 and the
concentrations of toxicants in sediment
originally reported as ppm were converted
to mg/kg (dry weight).
The unit "SS" refers to suspended solids
or suspended matter (See Appendix 6).
It may be assumed that concentrations of
toxicants in the muscle tissue of fish and
in the bail (prawns) were reported on a
net weight basis unless specified other-
wise. The "SS" refers to suspended solids
(See Appendix B).
All mercury concentrations in the paper
are reported as u/liter.
Units of measurement are those used in the
original text except for the "Tentative
Standards" units which were reported as
ppm and now converted to mg/kg for uniformity.
"SS" concentrations reported as ppm (See
Appendix B).
Units of measurement are as reported in
the original text except, ppm has been
changed to mg/kg when concentrations of
toxicants in spoils are referred to.
Units of measure are as they were in the
original text.
"SS" concentrations reported as ppm (See
Appendix B).
287
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APPENDIX B
Turbidity and suspended solids go hand in hand and may at times be
used somewhat interchangably. The two parameters are, however, quite
different and should not be confused. The following defines the two
terms and describes how they are measured and reported in this publi-
cation according to the Japanese Industrial Standard.
Turbidity—
TURBIDITY
the cloudy condition of water due to the suspension of
silt, finely-divided organic matter or other pollutants.
In Japan the standard unit of measurement is ppm. One
ppm turbidity is defined as the degree of cloudiness
present in water containing 1 mg of refined Kaolin in 1
liter of water.
GENERAL METHOD
There are two methods of measuring turbidity. Both measurements are
made by comparing the test water with a standard turbidity solution.
Standard Turbidity Solution
Place 1 gram Kaolin in a 1 liter flask, add 10 ml formalin and dilute to
1 liter with water. This is the primary standard solution. Secondary
standard turbidity solutions are made by diluting the primary standard,
e.g. 1 ml of the primary standard made up to 10 mis would provide a
standard solution in which 1 ml of solution would contain 0.1 mg of
refined Kaolin.
Measurement
Place 100 ml of test water in a test tube. Place 2, 4, 6, 8, and 10 ml
of the secondary standard solution in the same type of test tubes and
dilute them to 100 ml with water. Visually compare the turbidity of the
test water to the five different standard solutions by looking downward
through the length of the test tube. If the turbidity of the test water
is the same as one of the tubes which contains A ml of standard tur-
bidity solution, "Turbidity" is calculated as follows:
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T = Axlooox0.i
Where T = "Turbidity"
I = Quantity of test water (mis)
note: If the turbidity of the test water exceeds 10 ppm, dilute the
test water to less than 10 ppm and use the same method.
PHOTOELECTRIC PHOTOMETER METHOD
To Measure Transmitted Light
This is the method to measure light which passes through the test water
at a wavelength of 660 mu.
To Measure Scattered Light
This is the method to measure light scattered by small particles in the
test water.
Both of these methods require a calibration curve to be prepared with
standard turbidity solutions in order to determine the actual "turbidity."
SUSPENDED MATTER (Suspended Solids, "SS")
Suspended Matter— the substance which can be separated by filtration
or by means of the centrifugal separator. It shall
be determined by any of the following methods. When
the test water is difficult to filter, apply the
centrifugal separator method, and when the test
water contains extraordinarily large quantities of
suspended matter, apply the Buchner funnel method.
Test water shall be taken from the waste water
passing through a 2 mm mesh sieve. The lowest
detection level is 5 mg.
FILTRATION THROUGH FILTER PAPER
Sintered Glass Filter Method
1) Apparatus
Sintered Glass Filter--A crucible type glass filter 1G2 or a Buchner
funnel type sintered glass filter 3G2.
2) Operation
Prepare two sintered glass filters of the same type and approximately
same weight. Lay six sheets of filter paper on each one and pour water
over them several times so they adhere together. Then transfer the
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filters to a circulating air oven and dry them for two hours at 105-
110°C. Allow filters to cool in a desiccator, and weigh to the constant
weight (when a chemical balance is used, the lighter filter may be used
as a supplementary weight). Then pour a suitable amount of the test
water into the heavier filter1, filter by suction, and wash down the
substances adhering to the wall of the filter with the filtrate several
times. Next, pour the filtrate into the lighter filter several times
and filter by suction. Dry the two filters in the air oven for two
hours at 105-110°C, and allow to cool in a desiccator. Weigh each
filter (when a chemical balance is used, the lighter filter may be used
as a supplemental weight), obtain the difference in weight before and
after filtration, and calculate the quantity of the suspended matter in
ppm according to the following formula:
S = (a-b) x
1000
Where S = Suspended matter (ppm)
a = Difference in weight between before and after
the filtration of the test water (mg)
b = Difference in weight between before and after
filtration of the filtrate (mg) (when a
chemical balance is used, b = 0)
V = Amount of test water (ml)
Remarks 1. When determining the ignition loss of
volatile suspended matter, the test shall be carried out
in accordance with GFP method specified in Remarks 3, or
after washing out the suspended matter together with
filter paper into a crucible or an evaporating dish as
much as possible, then dry and ignite in the muffle
furnace.
Remarks 2. When soluble evaporated residue is less than 5000 ppm,
correction, due to the difference in weight of the
filtrate before and after filtration, may be omitted.
However, when chemical balance is used, lighter filter
shall be used as supplemental weight, so the filtration
of the filtrate shall be carried out at the same time.
Even when the direct reading balance is used, the weight
varies with the hygroscopic property of the substances
contained in the test water and other conditions, so it
is desirable to have the correction performed by obtain-
ing the blank test value of the filter through which the
filtrate is passed. When the test water contains a lot
1. The water sample must be sufficient to produce a suspended
solids weight in excess of 5 mg (the lower detection limit). Ordi-
narily, 200 ml of test water would be enough. However, for test water
which is rather difficult to filter, add 10 ml of test water just before
the test water is through filtering. Add the test water when filtration
has nearly stopped and use the total amount of added test water as the
volume for testing.
290
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of fats and oils, grease, wax, etc., a part of these
substances shall be determined as the suspended matter.
When a determination of suspended matter exclusive of
oils and fats is required, pour 10 ml of n-hexane over
the dried and weighed filter several times to wash out
the fats and oils. Then dry the filter and weigh again.
Remarks 3. Glass Fiber Paper Method (GFP Method)
Place on a Nutsche or suitable supporting plate a GFP
(Whatman GF/B or similar) filter of known weight, which
has been dried at 105 to 110°C for 2 hours after washing.
Pour a proper amount of test water into it so the weight
of the suspended matter after drying and filtration will
exceed 5 mg. Put a portion of the filtrate back in the
original test water container. Then-wash down the
suspended matter adhering to the walls of the container
and vacuum filter on GFP again. Repeat this operation
several times and remove as much water as possible.
Next, detach GFP from the filter and transfer it to a
watch glass, etc. Then proceed as described in the
discussion on operation of the Sintered Glass Filter
Method and obtain ppm of the suspended matter.
After determining the suspended matter, determine the
ignition residue in the suspended matter, if necessary.
Do this according to the operation described in the
section on Sintered Glass Filter Method.
Buchner Funnel Method
This method is applicable to samples containing a
quantity of suspended matter such as sludge.
1) Apparatus
large
Perforated Plate Made of stainless steel (SUS 27 or
28). Its size is about 0.5 mm in thickness, about 50 mm
or 90 mm in diameter and it can be put in a Buffner
funnel to be used. It is shaped like a watch glass with
a slightly-bent edge. Small mesh about 0.5 mm in dia-
meter is bored at suitable intervals over the flat
surface.
Rubber Packing Rubber packing is a rubber ring about
2 to 3 mm in thickness, about 10 mm to 90 mm in diameter
and about 10 mm in width. It can be put in a Buchner
funnel and used for filtration by means of suction,
putting the perforated plate on it.
Buchner Funnel
2)
plates.
About 50 mm or about 90 mm.
Testing Operation Prepare two perforated
Put rubber packing in Buchner Funnel and plate.
291
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Place the perforated plate on it. Then lay the filter
paper on (Grade 6), pour water through the filter paper
several times and apply vacuum. Remove the filter paper
with each perforated plate after drying it at 105 to
110°C for 2 to 3 hours. Allow to cool in a desiccator
and weigh to the constant weight (when chemical balance
is used, lighter perforated plate shall be used as a
supplemental weight). Next put the heavier perforated
plate and with the filter paper in the funnel and filter
200 to 400 ml of the test water by means of suction. Then
pour the filtrate into the lighter plate with filter
paper several times and continue the suction. When
filtration is completed take out the perforated plate
with filter paper on it and dry at 105 to 110°C for 2 to
3 hours. Allow to cool in a desiccator and weigh (when
chemical balance is used, the lighter plate shall be used
as a supplemental weight).
Obtain the difference in weight before and after this
operation, and calculate ppm of the suspended substances
contained in the water by the following formula:
s = (a-b) x
Where S = Suspended substances (ppm)
a = Difference in weight before and after
filtration of the test water (mg).
b = Difference in the weight before and after
filtration of the filtrate (mg). (When
chemical balance Is used b = 0)
V = Test water (ml).
Remarks: Same as remarks 2, 3.
FILTRATION THROUGH ASBESTOS LAYER
1) Apparatus Gooch crucible. 25 to 35 ml.
2) Reagents Suspension of asbestos. Add water to 15
g of asbestos for Gooch crucible and after removing fine portion by
decantation several times, add water to make up to a liter.
3) Operation Prepare two Gooch crucibles (same shape and
approximately same weight). After drying, pour about 20 ml of suspended
asbestos solution well-stirred to obtain a layer of asbestos about 3 mm
thick (about 0.3 g)2 and gently apply suction. Place crucibles into
the air oven. After drying for two hours at 105 to 110°C, allow to cool
in a desiccator and measure the weight of each crucible to the constant
weight (when chemical balance is used, lighter crucible shall be used as
a supplemental weight). Attach the heavier crucible to the suction
2. When half the amount of asbestos solution is poured, place the
perforated plate and pour the other half of the solution.
292
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bottle and pour a proper amount (so as to make the suspended matter
after drying over 5 mg) of test water into the crucible and gently
filter by means of suction. At this time, repeat the filtration of the
initial portion of the filtrate.
Next pour a small amount of filtrate through the lighter crucible
several times during suction, when the filtration is concluded, place it
in the air oven and dry for two hours at 105 to 110°C, and allow to cool
in a desicccator. Weigh the crucible, obtain the difference in weight,
and calculate ppm of the suspended matter by the following formula:
S = (a-b) x
Where S = Suspended matter (mg)
a = Difference in weight before and after
filtration of the test water (mg)
b = Difference in weight before and after
filtration of the filtrate (mg). (When
chemical balance is used, b = 0).
V = Amount of test water (ml)
Remark: Sampling method of the test water shall be performed in
accordance with Footnote 1 specified in glass filter method.
When the soluble volatile residue is less than 5000 ppm, refer
to Remark #2.
CENTRIFUGATION METHOD
This method is applicable to samples containing suspended matter
which are very difficult to filter.
1) Apparatus Centrifugal separator about 2000 rpm. Pre-
cipitation tube 50 to 100 ml.
2) Operation Pour a proper amount of test water (so as to
make suspended matter exceed 5 mg) into the precipitation tube. After
balancing each tube, centrifuge at about 2000 rpm for 20 minutes and
precipitate the suspended matter in the test water. Remove the super-
natant liquid by decanting3_ To the precipitate add about 10 ml of the
3. When the determination of soluble evaporated residue is per-
formed successively, keep the supernatant liquid. There should be a
certain degree of difference in density between the dispersed phase and
the dispersion medium to make the application of the centrifuge pos-
sible. When a particle of mass mg is centrifuged at an angular velocity
of w rad/sec, at a position of r cm from the center of rotation, cen-
trifugal force which the particle receives is as follows. Suppose that
the mass of the dispersion medium expelled by a partical is mg
o
then F = (m-m1) w r
Suppose that the specific centrifugal force is RCF and rotational fre-
quency per minute is N (rpm)
£ */ O
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the water and once again centrifuge and discard the supernatant liquid
by decanting.
Transfer the precipitate into an evaporating dish which has been heated
to a temperature of 105 to 110°C for 2 hours, allow to cool in a des-
iccator and weigh. (When chemical balance is used, evaporating dish of
the same shape shall be used as supplemental weight after the blank test
for it is performed). Then obtain the difference in weight before and
after this operation. Calculate the ppm of the suspended matter by the
following formula:
S = a
Where S = Suspended test matter (ppm)
a = Difference in weight before and after
evaporation of the test water (mg)
V = Amount of test water (ml)
METHOD OF CALCULATION OF SUSPENDED MATTER
FROM THE DIFFERENCE IN EVAPORATED RESIDUE
Calculate the suspended matter from the difference between the total
evaporated residue and the soluble evaporated residue.
A = B - C
Where A = Suspended matters (ppm)
B = Total evaporated residue (ppm)
C = Soluble evaporated residue (ppm)
(3. cont.) p 2
then RCF = 7^~ryq = — = 0.00001118 rN^
From the above equation, it is clear that the centrifugal force near the
surface and that at the bottom portion of the liquid are different. For
instance, when N = 2000 rpm and the distance between the surface of the
liquid in the precipitation tube and the center of rotation is 5 cm (r =
5 cm), RCF is 223g and when the distance between the bottom of precip-
itation tube and the central axis of rotation is 13 cm, RCF becomes
581g.
Therefore, the RCF value near the surface and that at the bottom shall
be reported respectively.
Depth of liquid layer (RCF at ^b.tto.^RCF^th. surface)
x (Distance down to bottom)
In this test, centrifugal separator of which the bottom is 13 cm away
from the central axis of rotation at a rotational frequency of 2000 rpm
is regarded as the standard.
294
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-77-083
3. RECIPIENT'S ACCES
MBtGEMENT OF BOTTOM SEDIMENTS CONTAINING TOXIC
SUBSTANCES: Proceedings of the Second U.S.-Japan Expert;
Meeting — October 1976, Tokyo, Japan
5. REPORT DATE
July 1977
< 6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Spencer A. Peterson and Karen K. Randolph, editors
8. PERFORH
JRGANIZ
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Research Laboratory--Corvallis, OR
Office of Research and Development
U.S. Environmental Protection Agency
Corvallis, Oregon 97330
10. PROGRAM ELEMENT NO.
1BA608
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
same
13. TYPE OF REPORT AND PERIOD COVERED
In House
14. SPONSORING AGENCY CODE
EPA-600/02
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The United States-Japan Ministerial Agreement of May 1974 provided for the
exchange of environmental information in several areas of mutual concern.
This report is the compilation of papers presented at the Second U.S.-Japan
Experts' Meeting on the Management of Bottom Sediments Containing Toxic
Substances, one of the 10 identified problem areas.
The first meeting was held in Corvallis, Oregon, in November 1975. The
second meeting (at which these papers were given) was hosted by the Japanese
Government in October 1976. The 1977 meeting is scheduled for Washington, D.C,
in the fall.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
cos AT I Field/Group
water reclamation
sanitary engineering
contaminants
water pollution
ocean bottom sediments
freshwater bottom sediments
toxic sediments
mercury, PCB contamina-
tion of sediments
water pollution
pollution elimination/
control
06/F
08/A,C,J,H
13/B,J
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
301
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (R«v. 4-77) PREVIOUS EDITION is OBSOLETE
295
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