&EPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/7-79-127
August 1979
Research and Development
Electroosmotic
Drying of Slime
Consistence Wastes
Interagency
Energy/Environment
R&D Program
Report
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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. Socioeconornic 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 INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
systems; and integrated assessments of a wide range of energy-related environ-
mental issues.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/7-79-127
August 1979
ELECTROOSMOTIC DRYING OF SLIME CONSISTENCE WASTES
Kazimierz Ukleja
Central Research and Design Institute for Open-pit Mining
Poltegor
51-6l6 Wroclaw, Poland
Project Number 05-53^-2
Project Officers
Russell Fitch.
John Hardaway
Cooper Wayman
Regional Office, Region VIII
U. S. Environmental Protection Agency
Denver, Colorado 80203
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 1*5268
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DISCLAIMER
This report has been reviewed by the U. S. Environmental Protection Agency
Region VIII Office and the Industrial Environmental Research Laboratory-
Cincinnati and approved for publication. Approval does not signify that
the contents necessarily reflect the views and policies of the U. S. Environ-
mental Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
11
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FOREWORD
When energy and material resources are extracted, processed, converted
and used, the related pollutional impacts on our environment and even on our
health often require that new and increasingly more efficient pollution con-
trol methods be used. The U. S. Environmental Protection Agency through its
Regional Offices and Office of Research and Development is striving to develop
and demonstrate new and improved methodologies that will meet these needs both
efficiently and economically.
The effort reported here was conducted as part of the Environmental
Protection Agency's Scientific Activities Overseas Program and was a cooper-
ative venture between Region VIII and the Industrial Environmental Research
Laboratory-Cincinnati. The research was conducted by Poltegor, the Central
Research and Design Center for Open-pit Mining, Wroclaw, Poland.
In this report methods to dewater the tailing slimes produced during
sulfur processing are described. The semifluid character of the material
presents significant handling and disposal problems. In a dewatered form the
slime would not only present less environmental problems, but also has the
potential to be used as an agricultural soil amendment.
Results of this work will be of interest to persons concerned with the
disposal of slime-like tailings material, e.g., phosphate and sand and gravel.
The methodology developed here probably has potential application in these
areas.
For further information contact Region VIII or the Resource Extraction
and Handling Division, lERL-Cincinnati.
Alan Merson
Regional Administrator
Denver, Colorado
David G. btepnan
Director
Industrial Environmental Research Laboratory
Cincinnati
111
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SCIENTIFIC ACTIVITIES OVERSEAS
(Special Foreign Currency Program)
Scientific Activities Overseas, developed and implemented under the
Special Foreign Currency Program, are funded from excess currencies
accruing to the United States under various U.S. programs. All of the
overseas activities are designed to assist in the implementation of the
broad spectrum of EPA programs and to relate to the world-"wide con-
cern for environmental problems. These problems are not limited by
national boundaries, nor is their impact altered by ideological and re-
gional differences. The results of overseas activities contribute directly
to the fund of environmental knowledge of the U.S., of the host coun-
tries and of the world community. Scientific activities carried out under
the Program therefore offer unique opportunities for cooperation between
the U.S. and the excess foreign currency countries. Further, the Pro-
gram enables EPA to develop productive relationships between U.S.
environmental scientist and their counterparts abroad, merging scienti-
fic capabilities and resources of various nations in concerted efforts
toward U.S. objectives as well as their own.
Scientific Activities Overseas not only supplement and complement
the domestic mission of EPA, but also serve to carry out the mandate
of Section 102 (2 (E) of the National Environmental Policy Act to "reco-
gnize the world-wide and long-range character of environmental problems,
and where consistent with the foreign policy of the United States, lend
appropriate support to initiatives, resolutions, and programs designed
to maximize international cooperation in anticipating and preventing a
decline in the quality of mankind's world environment".
This study has been funded from Public Law 480. Excess foreign
currency money is available to the United States in local currency in
a number of countries, including Poland, as a result of a trade for U.S.
commodities. Poland has been known for its extensive mining interests,
environmental concern, and its trained and experienced engineers and
scientists in this important energy area.
IV
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ABSTRACT
The objective of this research is the examination of field techniques
that remove water from sludge -tailings produced as a waste during
floatation of sulphur ore. The research was conducted with the idea of
utilizing these wastes in agriculture as a soil amendment useful to
neutralize acid soils. The main hindrance to economic utilization of this
type of wastes is their semifluid character. This fluid character persists
for many years, making it impossible to economically excavate and
transport the material for agricultural use. The technique investigated
for draining the sludge is comprised of a three stage system of drying
as follows:
(l) gravitational draining of water impounded in the bowl of the sedi—
x/
mentation basin; '
(2) draining a substantial part of the water in the sludge using electro-
osmosis which allows removal and some transport of the sludge;
and
(3) further drying to a relatively dry, plastic state by spreading under
conditions that facilitate atmospheric drying, or adding dry material
to the electroosmotically dewatered sludge.
The technical aspects of working with various types of excavating
equipment of transportation with lorries and trailers, the storage, the
mixing of sediments with fly ashes collected by electrofilters in power
plants fired with bituminous coal or lignite, and distribution on cultivated
lands was also examined. The stages of drying are discussed in more
detail below.
x/ The term sedimentation basin is used to denote a tailings disposal
area.
v
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1. Gravitational drainage of water accumulated on the basin formed
on top of the sediment 'was accomplished in stages by:
- syphoning water from the basin and discharging the water
beyond the pile;
- digging sumps in bottom of water - accumulating bowl and pum-
ping water as it drained to these sumps;
- sloping the surface toward the low areas and digging of ditches
from the low areas toward the edge of the basin;
- installation of a pipe from the ditch over the edge of the pile
to permit continued gravitational discharge from the pile.
The objective of these operations was to keep infiltration of
precipitation to a minimum.
Considerable technical difficulties were encountered during the
construction of this gravitational drainage system. The semi-fluid
character of the sediment made the use of mechanized equipment
impossible and open ditches continually filled with sediment. These
problems were complicat ed by frequent rains. The ditches had to
be systematically deepened since it was impossible to achieve the
full depth until the material had dried.
2. Drainage of excess water incorporated in the sludge (fluid sedi-
ments ) required the following procedures:
- laboratory and field investigations to determine the physico -
chemical characteristics of sediments that affected dewatering;
- laboratory model and field tests to determine the important varia-
bles for efficient design and execution of electro-osmotic draining,
including identification of the best arrangement of the electrical
field to induce the electro-osmotic phenomenon;
- small scale field investigations of electroosmotic draining on a
relatively small sedimentation basin in Ogorzelec (fig. 2) in order
to correlate laboratory and field tests;
VI
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- installation and operation of an electro osmotic system on the large
sedimentation basin in Ogorzelec (fig. 2);
- refinement of the electroosmotic system using 8 tests (fig. 73-80)
of different field arrangements amounts of current and periods of
current application;
- systematic meteorological tests, comprised of measurements of
atmospheric precipitation, evaporation, air and soil temperatures,
wind velocity and insolation;
- periodic measurements of subsidence of the surface of the large
sedimentation basin in order to calculate total losses of water
from sediment during draining.
One of the main tasks of these investigations was the determi-
nation of an optimal arrangement of the electroosmotic field. On the
small experimental sedimentation basin in Ogorzelec the battery of
filtercathodes was placed in the central part, where the material
contained the most water and the material contained the highest
fractions of clay-sized particles. The perforations cut in the wall
casings of the filtercathodes were very small (diam 4 mm) to pre-
vent inflow of tailings, but they quickly became plugged. When
large holes were used (4 x 50 mm), it was also necessary to pack
the holes with nylon gauze. This packing hindered the installation
of pipes, and reduced the electric resistance of the filtercathodes.
Moreover, the filtercathodes were often surrounded by water during
the periods of rain. The coarser grain material surrounding the ano-
des dried out and thus caused an increase in electrical resistance.
To circumvent these problems in the large settling basin, the filter-
cathodes were placed in the intermediate zone between the clay-rich
materials in the inner part of- the sedimentation basin and the sandy
material forming its external embankment. The bat tery of anodes was
placed in the central part of the sedimentation basin.
This change in arrangement also allowed easy access to filter-
cathodes independent of weather conditions, and pumping of water
Vll
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from the zone of highest content to a zone containing less water
and thus provided more favourable conditions for water to flow to
the filtercathodes.
The tests involving the application of current at varying times
and rates were designed to determine an optimal rate for dewate-
ring. These tests show that the optimal application (test § 8)
re quires 1.34 kWh electric power to produce 1 1 of water. The
electroosmotic system was designed to reduce the water in the cen-
tral zone of the sedimentation basin by about 10 percent. At the
resulting water concentration it appeared possible to begin to work
the material with mechanical equipment such as shovels.
3. The shovels were used to place the material in simulated windrows
(about 2 m high) where they were open to the atmosphere.
It was found that the material dried best when it was placed on dry,
permeable soil (as opposed to soils with a shallow water table or
on polyurethane sheets ).
The drying of the windrows was enhanced if they were placed
in a manner that exposed, them to the sun and the prevailing winds.
The material removed from the basin was also mechanically mixed
with dry fly ash from power plants fired with either bituminous or
brown coal (lignite). Such mixing resulted in the:
(l) Immediate drying of sediment to optional consistency (depen-
dent on proportion of components), and
(2) A more suitable mixture with respect to use in agriculture
(and use of the waste fly ash).
The experiments of fly ash mixing included transportation to and
spreading on agricultural land.
Mechanical handling of the wastes was most efficiently achieved
using draglines. Power shovels were not efficient since the material
stuck to the walls of the buckets. Special equipment was designed
to alleviate the problem with power shovels. An electrical current
was applied to the shovel for a short period to release the clayey
sediment.
VI11
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The results of this research work present one of many possible
technologies for drying semi-fluid sediments. Due however to variety
of physical-chemical properties of fluid industrial wastes, to the diffe-
rent systems of deposition and to various climatic conditions, the ques-
tions posed by drying other wastes will require performance of additio-
nal research in this respect.
This report was submitted in fulfillment of project number 05-534-2
between the United States Environmental Protection Agency and the
Central Research and Design Institute for Openpit Mining, POLTEGOR,
51-616 Wroclaw, Rosenbergow 25, Poland.
IX
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CONTENTS
Foreword ill
Scientific Activities Overseas iv
Abstract v
Figures xii
Tables xvii
Acknowledgments xx
1. Introduction 1
2. Conclusions 2
3. Recommendations 6
4. The Description of Project Outlines 9
5. Discussion of Literature 15
6. Description of the Flotation Sediment (Tailings) Basin
in Ogorzelec 20
7. Preparatory Studies for the Design and Construction of
a Subsurface Drainage System for the Tailings at
Ogorzelec . 49
8. Installation of Electroosmotic Drainage System on the
Main Sedimentation Basin in Ogorzelec 108
9. Drainage Produced by Electroosmotic System on the Main
Sedimentation Basin in Ogorzelec 118
10. Effects of Electroosmotic Draining of Main Sedimentation
Basin 149
11. Post - Electroosmosis Drying of Tailings Under
Atmospheric Conditions 167
12. Decreasing the Water Content of Postflotation Tailings
by Mixing with Dry Materials 188
13. Prognosis for Drying Tailings in Different Climatic
Regions 199
14. References 204
15. Glossary 209
xi
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FIGURES
Number Page
1 Location of the flotation sediment (tailings) basins in
the area of Ogorzelec 21
2 Surface configuration of sedimentation basin of flotation
tailings 22
3 General view of sedimentation basin in Ogorzelec .... 23
4 Example of distribution of size fractions within the
bounds of sedimentation basin through adoption of
chamber sedimentation method 25
5 Cross section of sedimentation basin (conditions before
drying) 25
6 Extreme limits of grain size distribution curves - outer
zone (embankment) 29
7 Extreme limits of grain size distribution - inner zone 29
8 Distribution of water content in top layer of the main
sedimentation basin, directly after drainage of sur-
face water 31
9 Meteorological station in Ogorzelec 40
10 Meteorological station in Ogorzelec - general view . . 41
11 Shielded evaporimeter installed on the main sedimenta-
tion basin 41
12 Meteorological station - soil thermometers 41
13 Meteorological station - poluviograph 42
14 Meteorological station - heliograph 42
15 Meteorological station - wild evaporimeter under umbrella
roof 42
16 Monthly values ofN atmospheric precipitations of soil
temperature and of air temperature 1975-1977 at
Paprotki and Ogorzelec 47
17 Monthly values of actual insolation, partial air saturation
and wind velocity in station Ogorzelec 48
xii
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Number
18 Research stand no. 1 - reservoir for model tests . . .
19 Fragment of model stand no. 1 - after filling with sedi-
ment 50
20 Schematic of electrical system for research model no.l 51
21 Average totalized water yields with constant current
intensity - tests 7.1.A. and 7.1.B 51
22 Dimensional sketch of container for model tests - con-
figuration no. 2 54
23 Method of collecting tailings to minimize disturbance
for model tests 54
24 View of container for model tests - configuration no. 2 55
25 Container for model tests filled with tailings 55
26 Standard steel filter-cathode-lead coating 55
27 Filter-cathode wrapped with nylon gauze 55
28 Schematic for electrical system used for standard filter
(without shield) - tests 7.3.G 59
29 Schematic of electrical system used for filter with
gravel pack sheld - test 7.3.H. 59
30 Change of resistance with time. Tests 7.3.G. and. 7.3.H. 61
31 Water yields with time. Tests 7.3.G. and 7.3.H 63
32 General view of test configuration no. 3 64
33 General view of test configuration no. 4 64
34 Scheme of test configuration no. 4 66
35 Scheme of electric connections of test configuration
no. 4 67
36 Element of test configuration no. 4 68
37 View of surface of the container during tests - filter-
cathode without filtration shield (conf. no. 4) ... 68
38 View of the container surface during the tests -
filtercathode shielded with nylon gauze (conf. no.4) 69
39 View of the container surface during tests - filtercatho-
de surrounded by gravel packing (conf. no. 4) .- . 69
40 Change in resistance with time. Tests 7.4.I., 7.4.J.,
7.4.K * 72
41 Water yields with time. Tests 7.4.1., 7.4.J., 7.4.K. ... 73
42 Electrical wiring diagram used for simulating electro-
osmotic dewatering of tailings examined under the
microscope 75
xiii
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Number
43 Scheme of laboratory sedime ntation basin used to
investigate changes in tailings sediment structure 77
44 Structure of tailings before electroosmosis 81
45 Aggregate structure at start of the electroosmosis . . 81
46 Increased size of aggregated particles and transforma-
tion to cell-like structure 82
47 Unstabilized cell structure 82
48 Stabilized cell structure with captive solution or gas 83
49 Qualitative diagram of structural changes intensity in
time 83
50 Chart of water discharge rate from cathodes. Conti-
nuous flow of current E = 0.23 V/cm 86
51 Chart of water discharge rate from cathodes. Variable
direction of current passage. E = 0.23 V/cm . . . 86
52 Chart of water discharge rate from cathodes. I nter-
mittent flow of current. E = 0.23 V/cm 86
53 Chart of water discharge rate from cathodes. Conti-
nuous current passage. E = 0.5 V/cm 89
54 Chart of water discharge rate from cathodes. Variable
direction of current flow. E = 0.5 V/cm 89
55 Chart of water discharge rate from cathodes. Intermittent
flow of current. E = 0.5 V/cm 89
56 Diagram of water discharge rate from cathodes with
growing electric field intensity 90
57 Water content to depth of 5 cm of tailings in laboratory
sedimentation basin after 283.5 hours of current
passage with increasing field intensity from 0.23
to l.O V/cm 90
58 Plan of the small sedimentation basin showing locations
of anodes and cathodes 98
59 Electroosmotic tests area on the small sedimentation
basin - after completion of drainage tests 1Q3
60 Emplacement of syphon in bowl of main sedimentation
basin 103
61 Temporary syphon arrangement for gravity drainage
of surface water 105
62 Permanent gravity drainage from the sediment basin
bowl with placed syphon in a ditch 105
xiv
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Number
63 Contour map of the main sedimentation basin bowl. The
107
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
Arrangement of anodes and cathodes within the bowl of
Blockdiagram of the electrical supply system
Typical electrical assembly drawing of feeding system
Sinking filter-cathodes into sediment with the aid of
Spacing of electrodes on main sedimentation basin,
showing the condition of the surface during the
The sedimentation basin surface after a year of
Changes in water yields and efficiencies during tests
1 and 2. Main sedimentation basin in Ogorzelec .
Changes in water yields and. efficiencies during tests 3
and 4. Main basin .
Changes in water yields and efficiencies during tests
Changes in water yields and efficiencies during tests
Changes in water yields and efficiencies during tests
Changes in water yields and efficiencies during tests
Changes in water yields and efficiencies during tests
Changes in water yields and efficiencies during tests
Su face elevation grid system used to measure corn-
Contour map of vertical displacement of the main sedi-
Characteristic profiles of vertical displacement of
^4 %~r fr
109
111
112
114
114
115
115
119
,119
137
139
14O
141
142
143
144
145
150
153
sedimentation basin bowl, taken from successive
elevation measurements 154
xv
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Number
84 Water content of surface layer of tailings after 9 months
of electroosmotic draining 158
85 Water content of surface layer of tailings after 13 months
of electroosmotic draining 159
86 Distribution in depth of water content in tailings on
near - anode area and the interelectrode area prior
to commenced electroosmotic drainage and after its
completion 162
87 Plan of drying the flotation sediments with uti lization
of natural drying 168
88 Plan for decreasing flotation sediments humidity through
mixing with dry components 168
89 The course of monthly component values of water
balance in Ogorzelec in years 1975 - 1977 170
9O Monthly values of precipitation and evaporation in
Ogorzelec for yeras 1975 - 1977 173
91 External shield and water container of evaporimeter . . 174
92 Installation of evaporimeter 's container into external
shield 174
93 Surface of tailings after initial drying period in evapori—
meter 174
94 Experimental windrows "A" and "B", contacting free
water table of the subsoil 176
95 Windrow "C" located on a permeable sandy subsoil . . 176
96 Windrow "D" isolated from subsoil with impermeable
foil 176
97 Monthly values of evaporation computed using empirical
formulae and measured with soil evaporimeters in
Ogorzelec for years 1975 - 1977 185
98 Mixture of tailings with dolomite dust 190
99 Mixture of tailings with ash from bitominous coal .... 190
100 Mixture of tailings with ash from lignite 190
101 Agricultural mixer used-in -field experiments to produce
mixtures of sediment and ash 192
102 Mixture of 75 percent tailings and 25 percent ash,
obtained in field tests 192
103 Spreading of tailings ash mixture of cultivated meadow
using a typical fertilizer spreader '. . 192
104 Climatograms for selected stations in Europe and in
Poland 2OO
xvi
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TABLES
Number
1 Average crops of plants from two series of tests in the
first and second years after treatment ........ 19
2 Physical characteristics of tailings from sedimentation
basin in Ogorzelec (before electroosmoti c draining
initiated) 35
3 Results of basic chemical analyses of tailings 38
4 Long term average data of air temperature and monthly
atmospheric precipitation at the station Paprotki, and
average monthly partial saturation of air humidity,
sums of actual insolation, total solar radiation, and
wind velocity in station Jelenia Gora ........ 44
5 Average monthly values of air temperature in Paprotki
and Ogorzelec, sums of atmospheric precipitation
in Paprotki and Ogorzelec, and sums of insolation,
average monthly humidity undersaturation of air and
wind velocity in Ogorzelec in years 1975 — 1977 . 46
6 Results of test 7.2.C 56
7 Results of test 7.2.D 56
8 Results of test 7.2.E 57
9 Results of test 7.2.P 57
10. Change of resistance with time. Test 7.3. G 60
11 Change of resistance with time. Test 7.3.H. 62
12 Water discharges in time. Tests 7.3.G. and 7.3.H. ... 62
13 Resistance change in time. Model configuration no. 4 . 70
14 Water discharges with time. Tests 7.4.I., 7.4.J., 7.4.K. . 71
15 Electrical resistance of tailings as a function of various
electrode construction, spacing, depth, voltage and
current intensity. Tests I to VII 96
16 Increments of water level in 12 hrs measurement periods 99
17 Increments of water level in 12 hrs measurements
periods after switching off current 100
xvn
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Number Page
18 Increments of -water level in 12 hrs measurements
periods after resumed voltage application on the
electro-filters 1O1
19 Chemical composition of selected tailings samples
located within the electroosmotic zone of the small
tailings pile at Ogorzelec 102
20 Changes in effective depths inside filtercathodes
during electroosmotic draining . . 116
21 Summary of results of electroosmotic drainage tests
performed on the main sedimentation basin in
Ogorzelec 147
22 Tests of the stability of external bench marks .... 156
23 Changes in average humidity contents in near - to -
surface layer of sedimentation basin (to 3 m) in the
course of electroosmotic drainage 161
24 Results of chemical analyses of tailings from Ogorze-
lec before and after electroosmotic drainage under
laboratory conditions 163
25 Results of chemical analyses of water collected, at
various stages of electroosmotic draining under
laboratory conditions 164
26 Results of chemical analyses of ground water
collected during various stages of electroosmosis
of sedimentation basin in Ogorzelec 165
27 Average monthly values of precipitation and. evapora-
tion using evaporimeters with a surface area of
250 cm2 on flat terrain (1975 - 1977 ) 171
28 Changes in water content windrowed. tailings with
time 177
29 Measurements of field evaporation for evaporimeters
placed on varying and aspects 179
30 Average long term (1951-1970) monthly precipitation
and theoretical evaporation at station Jelenia
Gora 186
31 Decrease in water content of post-flotation tailings
after mixing with dry fly ashes 191
32 Results of chemical analyses for the basic compo-
nents in fly ash, dolomite, tailings and mixes
thereof 197
33 Results of chemical analyses for microelement in fly
ash, dolomite, tailings, and mixes thereof 198
XVlll
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Number
34 Average long term monthly sums of atmospheric
precipitation, of potential evaporation according
to Thornthwaite, and of climatic water balance
for selected stations in different climatic zones 202
xix
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ACKNOWLEDGEMENTS
This final report was prepared as a result of research performed
by the Central Research and Design Institute for Open-pit Mining,
POLTEGOR-Wroclaw, POLAND under the agreement no. 05-534-2 with
U.S. the Environmental Protection Agency. The following institutions
cooperated with POLTEGOR during the project duration:
- the Institute of Agro- and Hydrometeorology of the Agricultural
Academy in Wroclaw, which performed meteorological observations
in the region of Ogorzelec and provided analyses of the data;
- the Institute of Geotechnique of the Wroclaw Technical University,
which contributed microscope investigations in electro osmotic drainage
and structural changes in tailings also surveys and observations
of vertical displacement of the talings pond surface in Ogorzelec;
- the Technological - Geological Enterprise of Building Ceramics in
Wroclaw which provided drilling and installation of electrofilters in
the tailing pond.
The project and the final report were directed by Dr. Kazimierz
UKLEJA.
Within POLTEGOR the project was coordinated by Dr. Jacek
LIBICKI, and an behalf of Central Authorities by Dr. Pawel BI/ASZ-
CZYK from the Institute of Environmental Protection in Warsaw.
Project supervision was provided by the following Project Officers
from EPA, Region VIII (Denver, Colorado):
- Mr. John Hardaway
- Mr. Russell Pitch
- Dr. Copper Wayman.
xx
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To all the three above mentioned Project Officers and especially
to Mr. John Hardaway we extend our grateful thanks and acknowledge-
ments for the assistance and advice rendered to us in the course of
the project. We appreciate also the help provided in arranging visits
and discussions with appropriate institutions in the U.S.A., which in
turn gave us the chance to get acquainted with similar research in the
U.S. These visits also helped to gain a better understanding of the
requirements for environmental protection and reclamation in the U.S.A.
Por assistance in organizational and financial matters, we gratefully
acknowledge the services of Mr. Thomas J. Lepine, Chief of the Special
Foreign Currency Program of the EPA, the program that provided the
money for the project. We also extend our acknowledgements to the
specialists from Denver Research Institute, from the Spokane Mining
Research Center - U.S. - Bureau of Mines, from the Appalachian
Region Commission - Washington D.C., from the Monongahela Power
Company, from Peabody Coal Co., from Florida Phosphate in Lakeland,
Florida, from Envirotech - Salt Lake City Utah, from Krebs Engineers
in Menlo Park, and from US Army Engineers Waterways Experiment
Station, for familiarizing us with the problems of storage and drying of
the post-flotation tailings and investigations there of in the U.S.A. All
of which helped us to improve our knowledge of the problem and to
reorient properly our research Work.
XXi
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SECTION 1
INTRODUCTION
Many industries require large amounts of raw materials which have
to be concentrated with water. The large amounts of tailings produced
must then be disposed of.
The fluid character of these spoils often requires disposal in large
sedimentation basins. Such basins use large amounts of arable and
forest lands.
Seldom are there opportunities to store these tailings in abandoned
open pits or on areas not otherwise in demand. The areas used for
disposal of tailings often create a threat of slides to the surrounding
areas.
Independently of the storage site the surface of such tailings is
always very weak. This makes impossible to reclaim their surface and
make it unaccessible for any activity.
These tailings have a potential for good use in agriculture as a
means of improving the structure and fertility of soils. Some tailings
may have a potential to be used as raw materials for building materials.
In some cases these wastes could be used to fill otherwise uneven
terrains. The main obstacle to economic utilization is their semi-fluid
character which prevents handling with mechanical devices and trans-
portation with conventional means. Drying of the tailings is therefore
an important issue and thus constitutes the main subject of this rese-
arch.
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SECTION 2
CONCLUSIONS
1. The test results characterized the clayey material produced during
the process of sulphur ore floatation at Ogorzelec as follows:
- high percentage of clay-sized materials
- high water content - about 54 - 37 percent
2
- bulk density of from 1.64 to 1.9 G/cm
- high CaO content over 40 percent. Si02 content of 12 percent.
The experimental results must also be related to the climatic con-
ditions characterizing Ogorzelec. These conditions are:
A cool, humid climate with considerable frequency and quantity
of precipitation (over 1000 mm annually) and with average annual
temperature + 5.6 C.
2. The region of the sedimentation basin is situated in mountains of
elevation on the order of 870 m, and the sedimentation basin itself
is located at an elevation of 640 m above sea level.
The experiments were conducted during periods of extremely wet
weather and thus the results were achieved under adverse condi-
tions.
The investigations have shown that provision for continued gravity
drainage of sufrace water is a prerequisite for successful electro-
osmotic drainage of sediment. Otherwise the precipitation will enter
into the sediment and defeat the purpose of dewatering. If water
does accumulate on the surface, the current should be withdrawn
from the electroosmotic system to prevent additional infiltration.
-------
3. Various electroosmotic field arrangements produce different drainage
effects. Localization of filtercathodes in the central part of a sedi-
mentation basin causes an inflow of fine - grained sediment into
wells through the casing holes and renders dewatering ineffective.
Further, the area surrounding the anodes dries out quickly, which
increases the resistance to current flow. Placement of filtercathodes
in an intermediate zone (intermediate particle size ) facilitates
efficient and uniform drying.
4. Laboratory tests indicate that electroosmosis also causes a number
of structural changes in the tailings. These changes include:
— reorientation of sediment skeleton elements
- migration of grains towards the electrodes
- formation of unstable aggregates of the very small grains
— suphosis
- formation of cell structures
- chemical corrosion of grains
— stabilization of sediment structure.
The least advantageous effect of electroosmosis on the structure
is the preferred arrangement of particles caused by the variable
direction of current flow. This caused a reduction in permeability.
Periodic interruption of the current flow tended to counteract this
preferential arrangement. During the cessation of current a partial
disintegration of the preferential structures occurs along with further
liberation of water. Upon renewal of current, electroosmotic drainage
continues until the preferred orientation again impedes water drainage.
Each successive break in current supply allows drainage to be
resumed.
5. The time length of switching-on and switching-off of current pro-
ducing the electroosmosis effect has real significance in the eco-
nomy of electric energy consumption and in distribution of this
consumption in time.
Por this purpose 8 tests were performed on the large sedimentation
basin, differing in intensity and in voltage of feeding current, in
cyclicify of its connection and disconnection, and in time of the
3
-------
breaks 'length in field electric supply. As a measure of efficiency
of considered tests was adopted consumption of electric energy per
liter of pumped out water (KWh/l). Comparison of tests shows that
the most advantageous current supply arrangement in respect of
energy consumption is a supply of 400 A current and 86.5 V vol-
tage to the field. A one-day-on, one-day-off cycle gave an efficien-
cy of 1.34 KWh/l . A significant reduction in water discharge after
cessation of current application followed by a fast rise after recon-
necting the current indicates further advantages of a 12-hour cycle.
This cycle has a further advantage in that the current can be swit-
ched off during day and connected at night to utilize current during
the hours of lower demand.
6. The total quantity of water pumped from the filtercathodes during
all the amounts to 104 cubic meters. The elevation surveys of the
surface of the sedimentation basin bowl drawdown indicates a total
3
with drawal of 1346 m . Differences in these values can be explai-
ned by:
- evaporation effects
- electrolysis effects occurring during application of current
- water losses by escape of water down the well.
Further quantitative determination of these factors has encountered
some difficulties.
7. The tests show that the quantity of water drained was affected by
the wet weather, and thus optimal dewatering was not achieved.
However, the ability to gain access to and to work with the tailings
is drastically improved. These positive effects include:
- precipitation does not percolate into the sediment and with the
exception of the top layer of about 30 cm thick;
- pits dug in the sediment to a depth of 2-2.5 m maintain their
vertical walls for longer time, both when they are filled with water
and when empty.
Reconstruction of the soil structure is effected by the electro -
chemical processes occurring during periods of application of
-------
electric current. Such phenomena were identified during microscope
observations.
8. It is advisable to reduce the moisture content (using electroosmotic
systems) to 30-35 percent. This facilitates handling with light me-
chanical shovels. Further drying of sediment, as is required for use
for constructing embankments, or in agriculture, can be achieved
through atmospheric drying.
Atmospheric drying can be achieved by windrowing the material
in mounds 2—2.5 m high, on a permeable subsoil. Rain water must
be quickly drained from the piles.
9. The drained sediments were most effectively handled using draglines.
Use of mechanical shovels would require the use of electrical
current of short duration (about 40 sees.), to empty the bucket of
the sticky sediment.
10. In circumstances where fly ash are available, mixing of the ash
with this sediment results in a mixture with good physical charac-
teristics for treating certain soils (often sandy). However, the
chemical effect of the fly ash on vegetation was not addressed.
Such mixing does not depend on first windrowing and drying the
material and thus has potential advantages.
-------
SECTION
RECOMMENDATIONS
Investigations and observations performed in the course of draining
sedimentation basins in Ogorzelec have shown that the problem of
drying fluid industrial wastes must be considered in connection with the
method of disposal into sedimentation basins, with their economic usa-
bility, with techniques of mechanical handling and transportation and
with the implications of mixing with other components.
In light of the experimental results, a number of general recommen-
dations can be formulated.
1. Prior to disposing of fluid industrial wastes into a tailings sedimen-
tation pond, one should consider the following:
- the eventual economic usability of the wastes;
- whether the wastes will be removed from the sedimentation basin,
or whether they are to remain.
If the waste's are to remain in the sedimentation basin, the final
phase of the deposition should be designed to drain the surface
with a gravitational or assisted discharge of precipitation beyond
the sedimentation basin. This would facilitate reclamation of the
sedimentation basin surface.
In cases where removal of sediment is anticipated, the depositional
process should be designed with drainage systems buried in the
pile.
2. In cases of disposal of fluid wastes in an uncontrolled manner, one
should ensure drainage of surface water, preferably through gravita-
-------
tional flow to a location away from the sedimentation basin. This is
a necessary condition to permit reclamation work of further draining
the wastes.
3. There may be cases where there will be no way to provide gravity
drainage (as for example at Ogorzelec). In such cases the water
should be drained using a syphon or pumps, after which ditches
should be dug to permit gravity drainage.
4. The vertical arrangement of electrodes creates a number of difficul-
ties of technical and exploitational nature, in view of which in future
research one should examine the feasibility of horizontal arrange-
ment of electrodes application with gravitational drainage to the cen-
tral water intake, or to natural flow.
5. The most advantageous arrangement of electrodes was one in which
the anodes were installed in the central, clayey portion of the
sedimentation basin and the cathodes in an intermediate zone, which
contained less water and was comprised of coarser particles.
6. In wastes with high percentages of small grains, voltages (potential
difference of the 0.15 - 0.2 V/cm rank) should be used for relati-
vely long periods of time. This allows:
- smaller consumption of electric power;
- more uniform drainage of the sediment; and
- better effect of soil structure reconstruction in the effect of
electrochemical processes.
The current should be routinely interrupted in order to:
- decrease the power consumption at a cost of only a small decre-
ase in water draining,
- improve the drainage by preventing preferred orientation of clay
particles and reductions 'in permeability caused thereby, and
- decrease the cost of energy by using it only during times of
non-peak (usage).
7. Frequent pumping of the filtercathodes increases the effect of
electro-osmotic draining. There appears to be merit in constructing
-------
a permeable layer at a depth such that water drawn to the cathodes
would constantly drain, by gravity, from the cathodes. Thus incon-
venient pumping would not be required.
8. Por economic reasons it is advised that electroosmotic draining of
sediments be used only to achieve a state that allows handling with
mechanical equipment (in the case of Ogorzelec this moisture con-
tent ranged from 35 to 38 percent). Purther draining of sediments
as may be necessary for use (to water contents of 20-26 percent)
should be achieved through atmospheric (natural) drying or through
mixing with water absorbing components, e.g., with fly ash genera-
ted in power plants.
9. Handling of the partially-dried sediments was best achieved with
light draglines since these had no problem in emptying the bucket.
Clamshell excavators have little difficulty in emptying sediment
containing 35 percent moisture. One should however avoid the use
of power shovels unless its bucket is fitted to provide an electri-
cal current at the time of dumping. The current breaks the bond
between the sediment and the steel bucket.
10. Initially favorable results were indicated when fly ash was mixed
with the partially - dried sludge. Such mixing also has the following
benefits:
- a decrease in number and quantity of sludge and ash in sedimen-
tation basins if the resulting mixture is utilized;
- economic utilization of mixture of both components, with the object
in their use for embankments ' formation, or for soil improvement;
and
- stabilization of fly ash if it is quickly mixed with sludge and not
allowed to remain in settling ponds as a source of fugitive dust.
8
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SECTION
THE DESCRIPTION OP PROJECT OUTLINES
The wastes derived in the processing of various type of minerals
when deposited in tailing ponds may constitute a real harm to the envi-
ronment. This particularly concerns tailings in a fluid, or semifluid form,
causing the risk of breaks of embankments and flooding of their neigh-
bourhood with fluid or semifluid wastes. These may easily occur in the
effect of big sudden showers, tectonic quakes, or other reasons and
could take place mainly in the case of sedimentation basins, elevated
above the terrain level. Moreover they can contaminate the environment
chiefly through a'n infiltration of solutions of disadvantageous pollutants
to the ground and to superficial waters.
To this type of tailing ponds belongs the pond of post-flotation
slimes located in Ogorizelec, where project research was carried out.
This pond was constructed on a slope of a valley in a hilly area.
Its surface is elevated 25 m above the terrain surface and it was filled
with semifluid wastes coming from sulphur ore flotation.
Relatively large amounts of atmospheric precipitation in this region,
and low natural evaporation from the terrain surface hindered natural
drop in moisture content of tailings, during eight years after their depo-
sition there. The above factors and the shape of this tailings pond
bowl were causing also the continuous retention of water to a depth of
1.5 m.
This state required a 3-stage system of slimes dessication which
was investigated during 3 years and is discussed in this report.
-------
THE OBJECTIVE AND PROGRAM OP RESEARCH
The object of this research was to investigate and develop methods
of drying tailings produced in a flotation process for sulphur ore. The
following three phase system of drying was adopted:
- development of system for drainage of shallow "ground water" and
runoff from the surface of the pile;
- withdrawal of ground water contained in the tailings using electro-
osmosis;
- subjecting the partially-dried material to the atmosphere with maximum
exposure to the air or mixing the material with power plant fly ash
to further facilitate drying.
Studies to determine procedures to economically use the tailings
and to transport, store and distribute the dried material on agricultural
lands were also conducted.
Program of research work
The research program was planned to be executed in three stages.
Stage I : (±974/75) Investigations of physical and chemical properties
of tailings laboratory tests of drying utilizing electroosmosis,
the establishment of a reference elevation line for later sub-
sidence measurements and a study of pertinent elements of
the climate in Ogorzelec.
Stage II: (1975/76)
- drainage of surface water from the tailings sedimentation
basin,
- installation of an electrokinetic system designed to dewater
the clayey tailings,
- systematic surveys of progressive subsidence of the sedi-
ments undergoing dewatering and continued measurement
of pertinent climate characteristics in the region of the
sedimentation basin.
10
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Stage III: (1976/77 )
- continued surface and subsurface drainage of the sedi-
mentation basin,
— continued subsidence surveys,
- continuation of observations of climate,
- investigation of mechanical handling of partially - dried
tailings and spreading for natural (atmospheric ) drying,
- investigation of mixing tailings with dry fly ash to reduce
moisture content,
- testing and.distribution of dried tailings for agricultural soil
amendments.
THE SCOPE AND METHOD OF RESEARCH WORK ASSIGNMENTS
The water content of existing tailings sedimentation basins may be
reduced using different techniques depending on the amount of dewa—
tering desired. Where the sedimentation basin is to be revegetated,
surface water may be drained using pumps and a system of open
ditches, or a subsurface horizontal drainage system.
When a removal of the tailings is required in addition to draining
the surface water, subsurface drainage is required to achieve a suffi-
ciently low water content to allow handling with mechanical excavation
and transportation equipment.
The tailings produced by floatation of e.g. sulphur ore have a high
content of clay-sized particles which are difficult to drain. Thus it is
necessary to assist dewatering, in this case through osmosis. When
these tailings must be excavated and transported for such uses as
for agriculture (for a deacidification or other improvement in the soil
structure), then the water content must be even lower than can be
achieved through electro-osmotic draining for a lengthy period. There-
fore in this case atmospheric drying or mixing with fly ash was used
to further dry the tailings.
11
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In order to develop an economic and technically viable dewatering
system, the character of the tailings must be determined and the perti-
nent climatic variables must be measured. To refine the methods of
electro-osmotic drainage, and to identify methods of excavating the
sediments with power shovels and distributing with agricultural equip-
ment, the changes in water content of the tailings must be periodically
measured.
Laboratory tests
Laboratory tests were performed to determine the physical - mecha-
nical and chemical properties of the tailings sediments.
Investigations of the physical characteristics included determination
of the weight and bulk density, natural humidity, grain size distribution,
consistency and of the consolidation index.
The measurements of the mechanical properties also included deter-
mination of the bulk modulus.
The chemical tests included determinations of:
a) for tailings sediment - pH and concentrations of calcium oxide
(CaO), silica (Si02), magnesium oxide (MgO), iron oxide (Pe ()„),
aluminium oxide (Al_0 ), zinc (Zn), sulphur (Sulphide and sulpha-
f.* O
te) (s), chlorine (d), lead (Pb), chromium (Cr), cobalt (Co),
copper (Cu), and manganese (Mn)
b) for water - pH and concentrations of the following ions:
Fe+2, Pe+3, d"1, Ca+2, Mg+2, SO^2, N^NQ j. Mn and Al+3.
*J
Laboratory model tests
Laboratory tests included small scale model tests of various methods
of electro-osmotic draining of sediments. The objective was to select
an optimal variant for specified conditions of a particular tailings sedi-
mentation basin.
12
-------
These model tests were conducted to test the efficiency of drainage
with direct current in the following spatial arrangements:
- a rectangular reservoir with dimensions 300 x 150 x 100 cm, and
varying the configuration of electrodes, current and voltage,
- a round reservoir with dimensions of diam. 40 and h = 30 cm
where the anode is the perimeter of the reservoir and cathodes are
the pipe filters of differing configurations,
- a round reservoir of dimensions diam 40 and h = 30 cm
where the anodes are strips of metal sheet, and cathodes are pipe
filters of differing configurations,
- a round reservoir of dimensions diam. 40 and h = 30 cm
where the anodes are strips of metal sheet, and cathodes are pipe
filters of differing configurations.
The laboratory investigations also included testing variants of mechanical
mixing of the tailings with dry fly dusts.
Climatological investigations
A meteorological station was established in Ogorzelec, to identify
meteorological conditions in the vicinity of the tailings pond. Of special
concern were the precipitation temperatures, and wind patterns charac-
teristic of the area, all of which materially affect the process of field
evaporation.
The process of water evaporation depends as a rule on three fac-
tors: on the amount of thermal energy, on the absorbing capacity of
air for water vapour, and on the degree of air turbulence. Quantitative
determination of solar energy gain in the form of total radiation requires
special tests with costly equipment. Therefore this had to be limited to
measurements of sums of real insolation. Knowing the length of a day,
one can, in an indirect way, determine the solar radiation.
The capacity of the atmosphere to absorb water vapour depends on
the actual temperature of air and on the quantity of water vapour pre-
13
-------
viously contained in the air. The absorption capacity can be expressed
in terms of the remaining water that can be added to attain saturated
conditions. The •water content expressed in millibars (partial pressure)
may easily be converted to grams of •water vapour which a unit volume
of air can absorb. Turbulence can generally be described by the •wind
velocity.
Measurements of other parameters (temperature of air and soil,
vapour pressure) were made to satisfy empirical formulae that evalu-
ate evaporation (formula of Penman (refs. 26, 27), of Turc (ref. 44),
of Thornthwaite (refs. 42, 43).
The phenomenon of evaporation can be very accurately determined
through direct measurements. Por this purpose a Wild 's evaporimeter
with an umbrella shutter was installed.
An essential component element of the water balance of an area is
precipitation. It was measured by means of pluviometers. Precipitation
causes changes in soil humidity, which affects drying. Determination of
the potential for drying tailings under actual field conditions through
empirical formulae which take into consideration the meteorological con-
ditions, should be checked through direct measurements of field eva-
poration. Such measurements were performed at Ogorzelec with the aid
of specially constructed evaporimeters. The construction and operation
of these evaporimeters are discussed later in this report.
14
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SECTION
DISCUSSION OP LITERATURE
Literature reviews included publications on soil mechanics, hydro-
geology, technology of storing the flotation tailings, sedimentology, etc.
Of even greater importance was information concerning the possibi-
lities and methods of drying, digging, and using the tailings economically.
The selection of literature presented below is connected chiefly with
these issues.
The drainage of tailings has been achieved through various methods.
A mechanical method, based on filtering the sediment (vacuum fil-
ters), or on centrifuging water by means of a basket or a casing cen-
trifuge have been used. B.oth methods require a large amount of energy
and achieve an average water content of 40 to 50 percent (refs. 28,29).
This water content is still sufficiently high so as to prevent economic
utilization of the tailings in a number of situations.
Drying at a raised temperature seems also to be uneconomic due
to significant energy requirements and the appreciable cost of the equip-
ment needed for water evaporation (refs. 28, 40).
Among the many other methods of draining tailings, two deserve
further at tention. These are drainage through application of electrical
current and mixing with substances which bond the water.
Electroosmotic drainage of soil is discussed in many papers (refs.
3,4,5,7,15,16,17,18,19,22,24,31,33,34,35,36,37,38,45,46,47,50). Under the
influence of direct current passing through a wet soil, the phenomenon
15
-------
of electroosmosis takes place as well as a number of other occurren-
ces such as: polarization of electrodes, electrolysis of water, soil
heating, and electrocataphoresis.
Part of the current flows through the soil skeleton, and part through
the water contained in pores. Under the influence of direct current
water particles tend to move along the lines of the electric field from
positive pole (anode) to the negative pole (cathode). Negatively
charged silt particles migrate in the opposite direction. Cases may
occur where acid soil components with positive charges migrate to the
cathode, and alkaline particles migrate toward the anode.
While many factors determine the effectiveness of electroosmotic
drainage, the most important ones are the type of soil, the density of
current conducted through the soil medium, the potential (voltage)
charge across the field, the soil humidity, and the temperature. These
variables may be represented by a socalled "coefficient of electro-
osmotic flow" (K^). This coefficient is determined for the specific con-
KJ
ditions in which the process of electroosmotic drainage is carried out
2
and is expressed in cm /Volt-sec.
The tests have shown that K is independent of the content of
xi/
silt despite the fact that these particles normally determine the hydra-
ulic permeability. The amount of electric energy depends on the type
of soil, on the exchange capacity, on the amount of water in the soil/
and on the volume of soil to be drained.
Soils with a fluid consistency have the least overall resistance to
electrical current. Below the limit of plasticity the resistance changes
relatively little, while above it rises rapidly. The relative amounts of
water in a free state and in bonded state are important in determining
resistance. Free ground water (gravitational) conducts the current
best, bonded water conducts water poorly, and hygroscopic water does
not conduct current at all. A decrease in the soil moisture results in
an increase in electric resistance of the soil.
In order to achieve optimal drainage under specific field situations,
it is advisable to first employ laboratory model tests. Analysis of elec—
16
-------
troosmosis show that there are numerous physical elements which
affect the efficiency of electroosmosis and that at least 18 of these
may be modelled (ref. 31).
In order to transfer the results of laboratory tests to field conditions
one must preserve a high degree of geometric similarity and constant
values of variables modelled. If this scaling principle is followed, the
field results may be accurately predicted.
Electroosmosis is a phenomenon that varies with time. Irreversible
chemical changes always accompany it.
Contrary to electrokinetic consolidation electroosmotic drying does
not produce a hard material and the soil is not dried uniformly.
The principal de-watered zone is located by the anode; the inter-
mediate part has a somewhat better consistency than it had before the
process, whilst the zone by the cathode remains essentially as it was
prior to draining. Electroosmosis is adversely affected by the irregular
depositional patterns of a typical tailings sedimentation basin and thus
the desired effect'may not always be achieved.
Another method which promises good drying capabilities is mixing
of the tailings sludge, once it may be handled, with dry, water sorbing
materials (ref. 28). Such substances can be so selected as to incre-
ase the utility of the sediment. Substances could include burnt lime
and a number of waste products such as fly ash from power plants
fired with bituminous or brown coal, waste material from the lime in-
dustry.
Burnt lime reacts easily with water: 1 g of CaO bonds (stoichio-
metrically) 0.32 g of water. This reaction generates also a large
quantity of heat, (16 K cal/mol), which contributes to the evaporation
of water from sediment (ref. 28). The equation for the reaction is:
CaO + HnO = Ca(OH) + 16 Kcal.
tL £
The hydrated lime becomes harder with time as carbon dioxide is
absorbed.
17
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Lime is utilized in Japan, for the dewatering and hardening of river
silts.
If the tailings sludges are dried to such extent that convential
transportation is possible, then material may be utilized for more uses
and over a wider geographical area. For example sediments having
a high shear strength, adequate compressibility and granulometric com-
position can be used as foundation material (ref. 21). Sediments which
have an appropriate chemical composition, an especially high calcium
oxide content and a small proportion of toxic components can be used
in the production of cement (ref. 8).
If the tailings are to be economically used, the options for use will
be enhanced if the locations of use are located close to the mines (26).
Perhaps the widest use of flotation tailings, considering the scale of
utilization, and economic effects, should be in agriculture. •Tailings from
flotation of the sulphur ore, which can be used as deacidifying and
improving soil structure fertilizer (refs. 6,11,12,39), may have a high
potential for such use.
The factor determining the fertilizer value of tailings chemical com-
position. It would be useful as a soil amendment, should contain more
than 40 percent calcium oxide and magnesium oxide and no toxic
admixtures of elements in quantities harmful to plants. It is desirable
if microelements such as the Na, K and Mn are present. The texture
and organic content are also important.
Studies of the use of selected wastes in agriculture were carried
out by the Institute of Cultivation, Fertilization and Pedology in Puiawy
(refs. 11,12). These studies consisted of laboratory tests and field
tests ( a total of 150 tests during a 2 years' period). The generalized
results of these studies are contained in table 1. This table presents
the relative crop yields resulting from various treatments of the soil
with sulphur ore tailings, fly ash (lignite) and lime (per M. Kac -
Kacas (ref. 11).
18
-------
Table 1
Average crops of plants from two series of tests
in the first and second years after treatment
(100 % = crop on soils not treated)
(M. Kac - Kacas. Ref. 11)
' — — >^^ Cultivation and crops
Fertilizer ~~ -— ~^^_^
1. Flotation lime
(of ore) sulphur
2. Ply ash from power
plant ( of lignite )
3. Standard lime
(ground limestone and
agricultural limestone)
Barley
(l-st
year
crops %
113.3
110.9
112.0
Clover
(2-nd
year
crops %
115.3
113.1
114.2
Oats
(l-st
year
crops %
106.0
114.6
109.8
Rye
(2-nd
year
crops %
lll.'S
108.9
108.8
These test results performed on acid and strongly acid soils, show-
that treatment with tailings produces results equal to those resulting
from the use of chemical fertilizer, and the "flotation lime" treatment
produces even better results. Presumably these results are due to the
sulphur content, (ref. 11). Attention is also directed to the satisfactory
results achieved by treating with ashes from power plants.
19
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SECTION 6
DESCRIPTION OP THE FLOTATION SEDIMENT (TAILINGS)
BASIN IN OGORZELEC
Field tests were designed and conducted to determine the best
method of drying and removing saturated flotation tailings deposited in
a sedimentation basin in Ogorzelec, near the Kamienna Gora, Voivod-
ship Jelenia Gora, Poland.
LOCATION OF THE SEDIMENTATION BASIN
The tailings on which field tests were performed were deposited in
two sedimentation basins situated in the valley of Swidnik, a tributary
of the river Bobr. This valley lays between the mountain range Rudawy
Janowickie from the Lasocki Ridge, and the Hills of Lubawska Pass and
is narrow and encised. The valley is oriented SW-NE.
The region is somewhat mountainous. Representative elevations are:
in the South 650 - 830 m, in the West 727-850 m, and in the North
800-850 m (above sea level).
The surface of the study area lays at an altitude of about 620 m.1
2 slope of the valley at the stu>
a Northern exposure (figs. 1,2,3).
The slope of the valley at the study site ranges from 3 to 8° and has
GEOLOGY
The region of the sedimentation basins, the upper part of the
Swidnik valley, belongs to a large geological unit of Western Sudety,
the Karkonosze. This area of the so called "eastern shield" of the
20
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sedimentation basins of
flotation sedimants
FIG.1 LOCATION OF THE FLOTATION SEDIMENT (TAILINGS)
BASINS IN THE AREA OF OGORZELEC
21
-------
IO
M
Fig.2 SURFACE CONFIGURATION OF SEDIMENTATION
BASIN OF FLOTATION TAILINGS
0
t_
+
SO
™:r
r EJ=V—_/^J"* "™ —I— w" "W " "" "" !U~ al^r***-'
^^
_100r
, S-a^VLe1,^, -s^ ",--• - j „„, t 4 „
«^f^-. • "%, ! A li "?4»'
V^^-c ^^wl il -^ •• 4
* ^^haj-j. ""^.S^ /"T"
-------
to
OJ
Pig. 3. General view of sedimentation basin in Ogorzelec.
-------
Karkonosze includes a large granitic intrusive. Rocks of Algonkian
age are located along the contact of intruding granite and paleozoic
formations. These include various types of crystalline schist, quartzite,
gneiss, and amphibolites. In the area of the sedimentation basin these
are covered with a layer of fluvial sediments, including gravels with
cobblestones several centimeters in diameter large, sandy clays, and
clayey gravels. The depth of these sediments varies from 0.5 to 1.5 m.
CONDITIONS OP THE TAILINGS' DEPOSITION AND SEDIMENTATION
The tailings sediments studied are a waste product of an opera-
tion conducted in the 1960 's in an experimental facility for dressing
and processing sulphur ore. The ore was obtained from deposits loca-
ted in the vicinity of the city of Tarnobrzeg.
The flotation tailings were slurried to the sedimentation basin via
pipelines and were discharged along the perimeter of the sedimenta-
tion basin. A number of low, earthen embankments were constructed
along the basin to provide detention of the tailings slurry. Coarser
fractions settled out in the vicinity of these embankments while the
smaller particles were carried on by water toward the center of the
basin (fig. 4). This results in a tailings deposit which may be divided
into two zones, (fig. 5), an outer zone containing a sandy - silt frac-
tion of sediments, and an inner zone containing a clayey-silt fraction.
These differences in granulometric composition of the zones produce
different hydraulic permeability and water yields for the zones.
The tailings at Ogorzelec were deposited in two sedimentation
basins located adjacent to each other (figs. 2,3). The smaller basin
is filled solely with sediments produced from sulphur flotation,1 and
has a depth of from 4 to 10 m. The larger one, called the "main basin",
has a more complex structure, since the upper 10 m contains sulphur
ore tailings and the lower part contains waste products produced
during the dressing of iron sands and barite ore. The external slopes
of both sedimentation basins are partially reinforced by slag, debris
24
-------
FigA EXAMPLE OF DISTRIBUTION OF SIZE FRACTIONS WITHIN
THE BOUNDS OF SEDIMENTATION BASIN THROUGH ADOPTION
OF CHAMBER SEDIMENTATION METHOD .
1-points of tailings discharge. 2 - flow of tailings from bays
of initial sedimentation, 3 - zone of deposition of sand fraction
it -zone of deposition of silt fraction , 5 - zone of deposition of
silt-clay .'ixjction .6 - overflow tower . 7 - pipelines delivering tailings
Fig.S CROSS SECTION OF SEDIMENTATION
(CONDITIONS BEFORE DRYING)
1 - sand - silt sediments
2- silt - sand sediments
3- silt - clay sediments
4 - surface water table
5- overflow tower
6- offtake of surface water
BASIN
25
-------
and filter cake from the sulphur smelting operation that followed the
flotation process.
PHYSICAL AND CHEMICAL PROPERTIES OP TAILINGS
Physical properties
In order to determine the physical properties of tailings deposited
in the flotation reservoir in Ogorzelec, the following laboratory deter-
minations were performed during 1974-76:
— granulometric composition
- water content
- specific gravity
- bulk density
- bulk density of soil skeleton
- limits of consistency.
All analyses were me.de in accordance with procedures contained
in Polish Standards PN-75/B-04481. Samples of the tailings were
collected at 56 points on the main sedimentation basin. The locations
were distributed along 8 profile lines in such a way that in the zone
near the perimeter there were 18 points and in the interior zone there
were 38 points (fig. &)•
At these locations samples were collected at selected depths to
5.5. m. A cylindrical sample collection device fitted with a piston was
used to collect the soft-plastic material. The available equipment did
not permit collection of samples from greater depths. However, a few
samples were collected from greater depths (to 10 m) during the
installation of the electrofilters.
The physical features of the undisturbed (prior to drying) tailings
are presented in the following discussions.
a. Granulometric composition
The grain size distribution was determined for 67 samples collected
26
-------
from various depths and locations along the previously noted profile
lines.
The laboratory methods of sieve and of areometric analysis were
used. The sediment samples, each weighing 40 g, were covered with
distilled water for 24 hours in order to produce a soft-plastic consis-
tency and uniform saturation with water. The sample was first sieved
through a 0.15 mm mesh. That remaining on the sieve was washed off
with distilled water to an evaporator, and desiccated at a temperature
of 105 C. After drying the gravimetric content of particles greater than
0.15 mm was determined. When this large fraction constituted more than
2 percent of the total weight of a sample, the fraction was subjected
to further sieve analysis of the larger fractions.
The material passing through 0.15 mm mesh was poured into a
conical flask. As this sediment coagulates easily, a solution of sodium
hexametaphosphate and anhydrous sodium carbonate was added as an
anticoagulant. Due to the high percentage of calcium in the sediment
(calcium dust), neither ammonia nor water glass could be used as an
anticoagulant.
The solution of sodium hexametaphosphate (technical name calgon)
and anhydrous sodium carbonate was mixed in proportions of 37.7 g
of calgon and 7.94 g of anhydrous sodium carbonate per liter of dis-
tilled water. This anticoagulant was then added to the sediment sample
(40 g mass) at a rate of 10 ml at the time of heating to boiling plus
10 ml after boiling.
After anticoagulation treatment and accurate measurement of the
suspension measurements with an hydrometer were performed at the
following time intervals: 30 sees., 1 min., 2 min., 5 min., 15 min., 30 min.,
1 hour, 2 hrs, 4 hrs, 24 hrs and. 48 hrs. Readings of the hydrometer 's
immersion depth were made using the top level of meniscus and the
observed values were corrected through addition of the hydrometer
correction factor and a correction for the difference of suspension tem-
perature and the calibration temperature for the instrument.
27
-------
The proportional content of particles in sediment was read from
appropriate nomograms prepared for each of the used in research
hydrometers.
The results of each sample analyses were presented in the form
of grain size dist ribution curves. Prom these curves, more comprehen-
sive diagrams for the external and the internal zones of the basin
were prepared (fig. 6,7).
The content of selected particles in the two zones vary widely
from sample to sample, but the following analyses shows that the sands
fraction is almost always minor in the internal zone:
Range in particle sjzes in external zone;
- sand zone 4 - 77 %
- silt zone 19 - 76 %
- clay zone 4 - 20 %
Range in particle sizes in internal zone;
sand zone 0 - 10 %
- silt zone 84 - 86 %
clay zone 4-26 %
The silt fraction predominates throughout the basin. A high sand con-
tent shows only in a small number of samples collected on the fringe
of the sedimentation basin. This type of granulometric composition
of postfloatation wastes is controlled by the processing technology for
sulphur ore. The distribution of particles within the sedimentation basin
is controlled by the method of disposal (figs. 4,5).
b. Water content (w)
The natural water content of the tailings (w) was determined as
the ratio of the water by weight (gw) contained in sediment to the
weight of the soil skeleton (gs), which may be expressed as a percent
as follows:
28
-------
MEAN DIAMETER (mm)
Fig.6 EXTREME LIMITS OF GRAIN SIZE DISTRIBUTION CURVES
-OUTER ZONE (EMBANKMENT)
o
10 -
20
30 -
60
70 -
BO -
90 -
grovel
••
....
—
I
...
_
-—
so
-•
«•
• •
nc
F
1
-
KFTOM7
-
-
- — •
..... .. .
M> « «-
cr Jj o-
r
s
silt
>
-
\
\
,
1
L-
...
\
\
n
--
•>>—
~n
—
^^^^^^^
i —
§«- u> " S
§ § I I
100%
90
80
70
60
SO
40
30
20
10
0
MEAN DIAMETER (mm)
Tig. 7 EXTREME LIMITS OF GRAIN SIZE DISTRIBUTION CURVES
- INNER ZONE
29
-------
w = - . 100 %
Qs
Two 30 g portions of each sample were weighed (to the nearest 0.01 g)
and dried at 105°C. Desiccation proceeded to the point where no further
weight loss was observed. After the determination of the sample weight
the water content was computed.
In order to determine the spatial distribution of water in the main
sedimentation basin samples for analyses were collected from locations
shown in figure 8.
The cylindrical piston sampler did not give reliable results for
these determinations since the depth at which the sample was collected
could not be easily determined. This was represented by the large
scatter of the data. In September of 1976 an improved collection device
was made which allowed accurate sampling to a depth of 3 m. The
results of water content, specific gravity and density analyses for the
period prior to September 1976 were discarded as unreliable.
A plot of the water content of the near surface layer of the main
sedimentation basin (fig. 8) was prepared on the basis of analyses
of samples collected (with the help of a gimlet), from depths to 1 m.
The figure shows the distribution of water in the near - surface tailings
immediately following the drainage of surface water from the bowl of
the basin. The 50 percent water content isoline conforms to the peri-
meter of the surface pool of water prior to drainage.
The external boundary of the water pool has been used to further
divide the internal zone of the tailings into two parts, A and B, as
shown on figure 8 and used in table no. 2. (Zone B is within the
original water pool; zone A is that portion of the internal zone which
is outside the pool).
The data in table 2 illustrate the water content in the near surface
layer of sediment and also in lower layers (to 9.5 m depth) preceding
the commencement of electroosmotic draining. Changes in water content
occurring with depth in internal zone B, were determined on the basis
30
-------
DISTRIBUTION OF WATER CONTENT IN TOP LAYER OF THE
MAIN SEDIMENTATION BASIN. DI3EOLY AFTER DRAINAGE
OF SURFACE WATER
explanation signes :
v
ojf i sampling locations
jii basin external slope
basin internal slope (boundary between
external and internal zone
initicl range of surface water, (boundary
between A and B internal
sampled drill holes
line of equal water content
-------
of analyses of samples taken from wells drilled specifically for the
electrofilters (locations designated KS, K , K21, K2g, O.C. - fig. 8)
since the piston sampler did not provide accurately locateable samples
as previously discussed.
c. Specific gravity ( ^ )
The specific gravity of the tailings material was determined through
solution of the following equation:
g ~ *t weight of solid
m . + Tm - m') - m
wt v g t wg
volume of solid
where:
Mg = mass of flask and soil dried at 105 to 110 C, in grams
m = mass of flask and distilled water at a temperature 20 C,
in grams
m = mass of flask with soil and water in grams
m. = mass of dry flask, in grams.
The sediment samples used for determinations of specific gravity were
dried at a temperature of 105 C for 24 hours. The sediment was then
ground in a mortar. To the calibrated flask was added 10 g of ground
sediment, and distilled water to half of the measuring flask and was
maintained for 20 minutes in a boiling state. The flask was then cooled
to 20 C and filled up with distilled water, also with a temperature of
20 C, to the measuring mark.
After completing the measurements, the flask was cleaned and
weighed with an accuracy to 0.01 g. Specific gravity determinations
32
-------
were repeated five times for each sample.
Values of designations of specific gravity are presented in table
no. 2.
The tests show that the sediment in the external zone of the sedi-
/vt
3-
o
mentation basin averages 2.72 g/cm , while the internal zone contains
less dense material (2.64 to 2.67 g/cm ).
d. Bulk density ( Q )
Bulk density was determined using cutting cylinder with a volume
3
of 8.6 cm . After filling the cylinder with sediment it was weighed.
Division of the mass by the volume according to the following formula
gives bulk density:
m m . - m.
_ m _ mt t
> ~ V V
P
where:
m = mass of sediment sample in natural state (g)
m
( 3\
v = volume of sample (cm ;
m , = mass of cylinder with sediment (g)
mt
m
't
mass of cylinder (g)
/ 3\
V = internal volume of cylinder (cm ).
Average values of bulk density are as follows: in external zone of
« O
basin - 1.75 g/cm ; in internal zone - from 1.75 to 1.94 g/cm . Results
of determinations are shown in table 2.
33
-------
e. Bulk density of the soil skeleton ( f> d)
Bulk density of the soil skeleton was computed according to the
formula:
-------
Table 2
Physical characteristics of tailings from sedimentation
basin in Ogorzelec (before electro osmotic draining
initiated)
Zone
of se-
dimen-
tation
basin
Exter-
nal zo-
ne
(banks)
Internal
zone
A
Internal
zone
B
Depth
of
sample
0.5-1.0
0.5
1.0
0.2-0.5
1.5
3.5
5.5
7.5
9.5
Numbe
of in-
vesti-
gation
points
18
14
14
5
5
5
5
5
2
1 Num-
ber
of
sam-
ples
15
14
14
5
5
5
5
5
3
Physical changes
Natural
humidity
%
14-34
24
30-38
33
24-37
32
34-54
47
34-52
45
32-41
37
34-39
37
21-37
31
30-33
32
Specific
gravity
g/cm
2.70-2.7^
2.72
2.65
2.65
2.64
2.66
2.66
2.67
extreme values
^ • " , ' ~
average value
Bulk
density
/ 3
g/cm
1.50-2£>9
1.75
1.62-2.00
1.90
1.62-2.01
1.90
L. 69-1. 87
1.74
1.66-1.92
1.74
1.83-1.90
1.86
1.79-1.88
1.85
L.85-2.07
1.93
1.90-2.00
1.94
Bulk
density
of soil
skele-
ton,
(3/r-m3
l.H-1.56
1.40
1.32-1.52
1.44
1.30-1.62
1.45
1.19-1.39
1.20
1.09-1.43
1.19
1.29-1.44
1.37
1.28-1.38
1.35
1.38-1.71
1.48
1.42-1.55
1.47
Figu-
re
sho-
wing
grain
size
distri-
bu-
tion
( i ft £,
'tlg.O
fig.7
35
-------
The average moisture content at the yield point for all samples is
27 percent.
2. Liquid limit
Liquid limit was determined on the Casagrande apparatus. The same
samples used in tests for yield point were used to determine flow limit.
The results were plotted according to the graphical method of liquid
limit determination where the water content is measured as a function
of "blows" the sample has received in the casagrande apparatus. The
water content after the equivalent 25 blows is the liquid limit. The slope
of the line is the flow index. The liquid limits calculated for the sam-
ples were:
Sample no. 1 - 41.0 %
Sample no. 2 - 44.9 %
Sample no. 3 - 48.3 %
Sample no. 4 - 44.3 %
The average of these is 44.7 percent.
The degree of plasticity flow was computed employing the following
formula for. the consistency index where W_ is the water content for
Li
the liquid limit, W is that for the plastic limit and W is the water con-
tent under natural conditions:
W - W
L V\£ _ W
using this degree of plasticity flow, the state of the tailings were
designated as follows:
Sample no. 1 - I = 0.95 - soft - plastic state
Sample no. 2 - I = 0.71 - soft - plastic state
Sample no. 3 - I = 0.52 - soft - plastic state
Sample no. 4 - I = 0.49 - plastic state.
The index of plasticity for each sample was also computed according
to formula:
36
-------
1P - WL - Wp' W
where W and W are as before. The results are:
LJ p
Sample no. 1 = 16.2 %
Sample no. 2 = 14.3 %
Sample no. 3 = 22.8 %
Sample no. 4 = 16.3 %
the average index of plasticity is 17.4 percent.
Chemical characteristics
Chemical analyses of sediment were made using standard analytical
methods for calcium wastes, where such are used to fertilize agricul-
tural lands. Content of particular elements was measured in terms of
selected compounds.
Calcium and magnesium were determined through the composite ver-
senate method or conversion to the oxides CaO and MgO. Results of
chemical analyses are provided in table 32 and 33 and results of
analyses for basic components are contained in table 3.
Samples No. 1,2 and 3 (table 3) represent (respectively) the
external zone:
(l) the intermediate zone,
(2) and the central internal zone,
(3) of the main sedimentation basin.
Sample no 4 was collected from a central part of small sedimentation
basin.
These samples have average contents of calcium (40 % of CaO),
silica (11.6 %) and insoluble compounds in comparison with agricultural
soil amendments. The content of magnesium oxide reaches about 1 per-
cent. The content of sulphur in a sulphide form fluctuates from 0.16 to
2.09 percent. The aluminium oxide content (A12°3^ from i-37 to 4-27
percent and iron oxide content (Pe203) from 0.79 to 1.61 percent.
37
-------
Table 3
Results of basic chemical analyses of tailings
No. and
place of
sampling
1. External zone,
main basin
2. Intermediate
internal zone,
main basin
3. Interior inter-
nal zone,
main basin
4. Internal zone,
small basin
H20
%
18.77
25.48
21.52
27.46
Content in dry mass, in %
CaO
44.61
37.56
38.96
38.03
MgO
0.60
1.07
0.87
0.74
Cl
0.00
0.00
0.00
0.00
s
(sul-
phi-
des)
0.16
2.09
1.93
2.01
Pe2°3
0.799
1.584
1.318
1.617
A12°3
1.37
4.27
3.80
3.96
Si02
10.72
12.02
11.57
12.07
Inso-
lubles
1.85
1.85
2.11
2.61
Losses
after
sin
tering
31.86
34.99
36.07
35.21
oo
-------
DESCRIPTION OP LOCAL CLIMATE IN THE REGION OP OGORZELEC
Method of measurements and discussion of results
Meteorological tests were carried out at the meteorological station
established in Ogorzelec during the period: 1 Jun. 1975 through
30 Jun. 1977. Measurements of temperature and of relative atmospheric
humidity were made with an Augustus psychrometer, placed in a mete-
orological instrument shelter at a height above the ground of 2 m.
Daily values for the 0100 hour were recorded from the hygrothermo-
graphs in accordance with instructions for- the Polish network of mete-
orological stations. Minimum and maximum thermometers were also insta-
lled in the shelter.
Measurements of the soil temperature at depths of 5,10 and 20 cm
were made with soil thermometers. Measurements of minimum tempera-
tures at the soil surface (5 cm above the soil) were obtained with the
minimum thermometer.
Daily sums of precipitation were measured with the Hellman pluvio-
meter with the intake located at a height of 1 m. The intensity of pre-
cipitation during the warm half of the year was measured with a daily
pluviograph.
The wind velocity and direction were determined with a Wilde ane-
mometer, installed 11 m above the surface.
Daily sums of solar insolation were measured with a heliograph
(Campbell - Stokes).
The meteorological measurements have been prepared in a form of
daily average, 10-day average, and monthly average and were speci-
field in working tables. The monthly values were selected from these
comprehensive tables for later presentation in this report.
Evaporation from a free water surface was determined with the
Wilde evaporimeter placed under an umbrella roof, 50 cm above the
soil surface. Measured values were analyzed in the form of daily,
10-daily and monthly sums.
39
-------
E
o
°3
°e
2
b
o o o o
a
0
Fig9 METEOROLOGICAL STATION IN OOORZELEC
EXPLANATIONS
1 — meteorological shelter
2 — check area with no vegetation
2a — minimal-reading soil thermometer
2b - elbow soil •thermometers
3 — Hellmonn's pluviometer
A - pluviograpn
5 - heliograph
6 - Wild' s anemometer
7 - Wild's evaporirneter with umbrella roof
8- soil evaporimeters
-------
Pig. 10. Meteorological station in Ogorzelec — general view.
Pig. 11. Shielded evaporimeter installed on the main
sedimentation basin.
Pig. 12. Meteorological station-soil thermometers.
41
-------
Pig. 13. Meteorological
station —
pluviograph
Pig. 14. Meteorological station
heliogaph.
Pig. 15. Meteorological station -
Wild evaporimeter
under an umbrella roof.
42
-------
Pield evaporation from the tailings was measured directly at the
tailings site using gravimetrical soil evaporimeters, with surfaces of
2
250 cm and depths of 30 cm.
Using the precipitation amount, the quantity of percolation and diffe-
rence in the monolith weight during the period of measurement, the
field evaporation was determined.
Results of meteorological measurements in Ogorzelec during the
investigation
Ogorzelec is included in the zone of moderately cold and relatively
humid climate designated by Schmuck and Sudety (ref. 25). Owing
however to the lack of meteorological stations in Ogorzelec prior to
this research the analysis of climatic conditions was based on data
obtained from 1951 to 1970 at Paprotki (located about 5 km south of
Ogorzelec), and from Jelenia Gora (20 km N.W.). Long term observa-
tions of selected climatic elements at these stations are presented in
table 4.
The characteristic feature of temperatures in the mountains is
temperature smaller difference between summer and winter in compari-
son to the lowlands. Also the daily fluctuations in temperature in the
mountains are more pronounced. At the elevation of Ogorzelec, the
warm temperatures of summer, (i.e., the period with average monthly
temperatures above 15 C) are essentially not present.
Long term precipitation patterns were also determined from data
collected at the Paprotki station, which is situated much like the
Ogorzelec station, on the lee of the mountains. The month with highest
precipitation is July (112 mm table 4). The lowest precipitation occurs
during the winter months. Despite a small distance separating Paprotki
from Ogorzelec, investigations made in 1975/77 suggest that the total
annual precipitation in Ogorzelec is at least 150 mm higher than the
707 mm at Paprotki.
Long term values of other meteorological variables were determined
from measurements at Jelena Gora, little more distant from Ogorzelec
43
-------
Table 4
Long term average data (from the period 1951-1970) of air temperature (t, in C),
and monthly atmospheric precipitation (P, in mm) at the station Paprotki, and
average monthly partial saturation of air humidity, (d, in mbj, sums of actual inso-
lation (s, in hours )4 total solar radiation, (T, in Kcal . cm" ), and wind velocity
(v, in m/sce.) in station Jelenia Gora.
t
P
d
s
T
V
Jan.
-5.0
24
1.2
46
2.0
3.1
Feb.
-3.0
31
1.1
70
3.5
3.0
Mar.
0.6
35
1.9
112
6.8
3.2
Apr.
5.7
50
3.0
133
9.4
2.6
May
9.9
89
3.8
178
12.7
2.4
Jun.
13.5
90
4.8
188
13.5
2.2
Jul.
15.0
112
5.0
189
11.3
2.3
Aug.
14.1
85
4.3
176
11.5
1.9
Sept.
10.8
47
3.5
144
8.1
2.3
Oct.
6.8
56
2.7
110
5.1
2.6
Nov.
1.4
51
1.6
43
2.1
3.0
Dec.
-1.9
37
1.2
37
1.5
2.8
Apr.-
-Sept.
11.5
473
4.1
10O8
68.5
1.4
Year
5.6
707
28
1426
89.5
2.2
-------
since there seemed to be relatively spatial variability (with exception
of partial saturation). Partial saturation is expected to be higher at
Ogorzelec.
Maximum insolation occurs in June and July but the amounts are
not particularly large. The wind velocities are rather low at Jelenia
Gora for locations in valleys.
Detailed characterization of climatic variables at Paprotki and
Ogorzelec during 1975 and 1977 is presented in table (5) and on
figures 16 and 17. These observations indicated no significant devia-
tions from the longer term averages.
The air temperature during 1975 - 1977 at both Ogorzelec and
Paprotki was similar with the exception of June 1975 (Ogorzelec was
cooler by 1.1 C), and June 1976 (Ogorzelec was warmer by 0.7 c)
with respect to long term averages, temperatures during August 1976
were cool and during September 1975 were warmer. The distribution
of precipitation differed between stations. With the exception of Decem-
ber 1975 and July 1976, when the precipitation was almost the same
as in long term, in the remaining months observed were significant
deviations from normal. January 1976 and August 1977 were extermely
wet (500 and 470 % higher precipitation). September 1975 and June
of 1977 were quite dry. In terms of solar insolation June and July of
1976 and August of 1975 were quite sunny. The insolation in June of
1975 and September 1976, and July and August of 1977 was relatively
low.
The partial saturation of air approximated the long term values with
the exception of three consecutive months of 1976 (May, June and
July) exceeding average values by as much as 3 milibars.
The wind velocities consistently followed the long term average
values.
45
-------
Table 5
Average monthly values of air temperature in C in Paprotki
(t ); in Ogorzelec (t ), sums of atmospheric precipitation in
mm in Paprotki (p ) and Ogorzelec (P ); and sums of
insolation in hours (s), average monthly humidity undersa-
tuarion of air in millibars (d) and w ind velocity in m/sec.
(v) in Ogorzelec in years 1975 - 1977
t
*0
1975 Pp
P
o
s
d
v
t
tP
P°
1976PP
o
s
d
v
t
P
t
o
!977Pp
P
o
s
d
v
I
-3.5
-2.6
100
151
40
1.2
3.9
-2.4
-2.1
22
34
29
1.0
In 8
II
-3.0
-2.1
19
26
96
1.3
2.2
-0.7
-0.1
49
78
56
1.3
1.6
III
-2.8
-2.5
15
35
86
1.7
2.2
4.0
4.3
22
45
95
2.5
2.Q
IV
4.2
4.3
16
35
133
2.9
2.1
3.5
3.7
37
70
122
2.7
3.1
V
10.2
10.4
39
73
191
5.8
1.7
9.5
9.9
112
143
145
4.5
1.8
VI
14.0
12.9
87
127
91
4.0
1TQ
13.4
14.1
41
45
253
7.8
1.8
13.9
14.2
116
133
150
5.0
1.5
VII
15.8
16.1
106
179
168
5.7
15.8
16.2
114
112
217
7.7
1.4
13.8
14.2
132
180
148
5.0
1-9
VIII
15.2
15.6
77
53
203
4.9
1 <=;
12.2
12.8
73
87
193
4.5
1.2
13.6
13.9
168
387
116
3.3
1.8
IX
13.6
13.7
20
24
158
4.3
1 Q
10.1
10.1
40
67
98
2.8
1.3
X
5.4
6.2
64
94
90
2.1
1 «
7.9
8.4
63
77
109
2.5
2.3
XI
O.o
0.1
40
54
41
1.2
2 1
3.2
3.3
72
141
27
1.4
2.6
XII
-1.0
-0.9
31
44
26
1.2
3 2
-3.4
-2.9
40
61
25
1.2
2.0
46
-------
P(mm) r
VB vm IX X A! XH ! B III W V VI VB vlfl IX X XI XD
Fig. 16 MONTHLY VALUES OF ATMOSPHERIC PRECIPITATIONS (P IN mm )( OF SOIL
TEMPERATURE (tg) AND OF AIR TEMPERATURE (t.°C) 1975-1977 AT
PAPROTKI AND OGORZELEC
1-long term precipitation 1951-1970 in station Fbprotki . 2 - precipitation in station
Poprotki in years 1970-1977.3- precipitation in station Cgorzelec in years 1970-1977,
4-temperature of soil in station Dgorzelec at 5cm depth , 5-temperature of soil
in station Ogorzelec aMOcm depth. 6- temporature of soil in station Ogorzelec at
20cm depth.7-long term air temperature 1951-1970 at Paprotki. 8-air temperature
1970-1977 at Paprotki , 9-air temperature 1975-1977 at Ogorzelec
47
-------
>__!
vi vn
VDI ix x xi xn i n m iv v vi vn vm ix x xi xn i n m iv v vi VH \ui
1975 1975 1377
Fig17 MONTHLY VALUES OF ACTUAL INSOLATION ( S IN HOURS ) PARTIAL AIR SATURATION
(d IN mb) AND WIND VELOCITY (v IN m/sec) IN STATION OGORZELEC.
1-long term insolation for 1951-1970, 2 - insolation for 1975-1977 , 3 - long term
partial air saturation for 1951 - 197O . 4- partial air saturation for 1975-1977,
5-long term wind velocity for 1951 -1970. 6 - wind velocity for 1975-1977
-------
SECTION 7
PREPARATORY STUDIES FOR THE DESIGN AND CONSTRUCTION
OF A SUBSURFACE DRAINAGE SYSTEM FOR THE TAILINGS AT
OGORZELEC
MODEL TESTS OF ELECTROOSMOTIC DRYING
The tailings in the sedimentation basins are difficult to drain.
It was, therefore, decided to conduct model tests prior to field tests to
determine the optimal values of the current density, the type of elec-
trodes, and the best spatial arrangement.
Research model configuration no. 1
This stand was designed with the objective of observing electro-
osmosis phenomenon in the tailings and to determine the general condi-
tions benefiting draining.
A container of reinforced plates was constructed with dimensions of
300x150x100 cm. The interior of the box was lined with fiberglass,
impregnated with epoxy resin. The resin was applied to seal off the
box and to electrically insulate the box from the sediment.
Electrofilters made of aluminium pipes with diameters 0 40 mm and
0 25 mm were spaced as shown in fig. 18. Pipes were connected in
groups with a flat copper bar. Figure 19 shows the model after filling
with tailings.
A 5 kVA autotransformer and a rectifer on siliceous diodes in
Graetz system were employed. An electric diagram is shown in fig. 20.
49
-------
Pig. 18. Research stand no. 1 - reservoir for model
tests.
Pig. 19. Pragment of model stand no. 1 - after filling
•with sediment.
50
-------
300cm
O
f
3
O~-
-A/VW
Fig.20 SCHEMATIC OF ELECTRICAL SYSTEM FOR RESEARCH MODEL No.1
(1.2.3.4 -INDICATES ROWS OF ELECTRODES)
VOLTS so
Ul
o
1OOQ 20OO 3OOO
SOOC 6OOO TOGO
WATER YIELD (ml)
Fig. 21 AVERAGE TOTALIZED WATER YIELDS WITH CONSTANT
CURRENT INTENSITY - TESTS 7. .1.A AND 7, 1.B
( 1.2.3,4 -INDICATES ROWS OF ELECTRODES)
51
-------
This system can simultaneously produce two different current densities
on two different groups of electrodes.
3
Pour and one-half m of tailings were compacted uniformly in the
box. The electrofilters were purged to remove sludgeand the pipes
connected such that row 2 served as a cathode and wells of row 2
and row 1 were the anode. A constant current of 2 A was applied
giving 0.5 A per well (Test 7.1.A).
A second field was simultaneously created using row 4 as the
anodes and row 3 as the cathodes. A current intensity of 1 A was
applied to these resulting in 0.25 A per well (Test 7.1.B.). The inten-
sity was corrected twice a day at the time accumulated water was
discharged. The average total yields of "wells" of particular rows are
shown on fig. 21. The diagram suggests the rate of current density
has a strong influence on water yield. While most of the water accumu-
lated at the cathodes, small quantities also accumulated at the anodes.
Water in cathodes was a yellowish, light green, while that at the ano-
des was dark grey. This suggested different chemical compositions.
Water chemistry tests were therefore performed. The results are summa-
rized in table 25. The "anode water" contained a large amount of SO ,
which also explains the intense corrosion of the aluminum pipes obser-
ved during the tests.
The corrosion also attacked steel anodes. Additional tests were
performed to identify measures that could protect against corrosion.
Pipe coatings of various types were applied with an epoxy resin. The
value of the resistance between two aluminium pipes without any co-
ating was used was a reference (R=l) to compare the effect of the
anti-corrosion coatings on the efficiency of producing water with given
amounts of current. The following coatings were tried:
- paint containing 80 % of lead minium; R = 5.22,
- paint containing 80 % of lead minium with 5 % carbon black added;
R - 5.3
- paint with 32 % zinc dust; R = 10.8
- paint with 30 % coal dust; R = 16.8
52
-------
- paint with 32 % zinc dust and 5 % coal dust; R = 11
- electrode of carbon black; R = 2.6
These coats greatly increase the contact resistance, and only the
electrodes made of carbon black appear to have potential for use.
However such electrodes are fragile and difficult to fabricate in ade-
quate lengths and thus do not have a practical application.
Additional tests were made on coating steel pipes with lead, using
a method of thermal plating. Given the considerable resistance of lead
to chemical action, one could presume that lead-treated pipes would
have a greatly extended life. The model tests performed on lead plated
pipes confirmed the potential for longer life. However one could not
completely prevent corrosion. Corrosion caused scaling of the lead
plate. It appears that metal scrap might be best for anodes, assuming
that it is expendable, since economical means of controlling corrosion
were not identified. It is advisable to protect the surfaces of the
electro-filters with a thin lead coating.
Model research configuration no. 2
These laboratory investigations were performed on relatively undis-
turbed tailings sediments collected in a cylinder 40 cm in diameter and
3O cm in height (volume 37.68 liters).
These tests were performed to determine changes in resistance
occurring with changes in the type of electrode.
The samples were collected such that after removal of the upper
15 cm of tailings at the field site the cylinder was pressed into the
sediment. After removing the sediment around the sides, the tailings
inside the container were cut from the underlying material with a metal
sheet and rotated by 180° (fig. 22-25).
Cathodes were inserted in the tailings to estimate their electric
resistance (R), calculated from voltage and current measured at 10 min.
intervals.
Por the standard filter - steel pipe coated with layer of lead and
without an outer shield (figure no. 26 and test 7.2.C.) the results are
presented in table 6.
53
-------
4OO mm
/2
Rg,22 DIMENSIONAL SKETCH OF CONTAINER FOR MODEL
TESTS - CONFIGURATION NO. 2
1 - cylinder of steel sheet, 2-textolite plate
. -\\
«
r™
\
~
1 1
^
r'"
^ x
\ V
\^ ^
% X
^ \
w \
\ v
B^ ^
/ «i V-^
«
«
*,
rt
\v
'J,
tv
M
"\
."" \J
Fig.23 METHOD OF COLLECTING TAILINGS TO MINIMIZE
DISTURBANCE FOR MODEL TESTS
1- metal sheet , 2 - tailings
54
-------
Pig. 24. View of container for
model tests - confi-
guration no. 2.
Pig. 25. Container for model
tests filled with tailings.
Pig. 26. Standard steel filter-cathode-lead coating.
Pig. 27. Pilter-cathode wrapped with nylon gauze.
55
-------
Results of test 7.2.C.
Table 6
Electrical
variables
Voltage
u (v)
^^^^^^^•^^^^•^^^MW^^B^P-MM^M*^W«»^^^-^^— ^^^"-^
Current
I (A)
Resistance
R (A)
time
0 min.
18.2
1.30
14.0
10 min.
20.5
I^^^^^^^^^^^^MIW^^.M«««>*M-
1.55
13.4
20 min.
6.6
0.45
14.6
30 min.
7.5
0.51
14.5
The cathode consisting of a steel pipe wrapped in a single nylon
gauze (mesh 1x1 mm test 7.2.D. ) was also tested and
the results are presented in table 7.
Results of test 7.2.D.
Table 7
Electrical
variables
Voltage
U (V)
Current
I (A)
Resistance
R (n)
time
0 min.
7.5
0.48
15.6
10 min.
10.2
0.72
14.3
20 min.
13.6
0.98
14.0
30 min.
14.6
11.0
13.2
The experimental results using a cathode doubly - wrapped with
nylon gauze are presented in table 8 (test 7.2.E. ).
56
-------
Results of test 7.2.E.
Table 8
Electrical
variables
Voltage
u (v)
Current
I (A)
Resistance
R (a )
time
0 min.
10.6
0.44
24.1
10 min.
13.0
0.57
22.8
20 min.
21.0
1.06
19.8
30 min.
25.5
1.35
18.9
A fourth filter arrangement consisting of gravel packing was also tested
(test 7.2.P. ). The results are indicated in table 9.
Results of test 7.2.F.
Table 9
Electrical
variables
Voltage
U (V)
Current
I (A)
Resistance
R (Q )
time
0 min.
8.8
0.12
73.2
10 min.
7.7
0.106
72.6
20 min.
20.3
0.15
68.7
30 min.
11.0
0.17
64.7
57
-------
Analysis of these results indicates that the unwrapped filter has the
lowest resistance. Thus such filters require the least amount of elec-
trical energy for unit discharges of water. The standard filter has one
fundamental drawback, that is the need to make numerous very small
holes to allow water to seep in and to keep the tailings out of the
casing. The addition of a nylon gauze increases the resistance a small
amount but this increase appears to decrease slightly with time. If the
gauze simplifies the construction of the perforations, the gauze could
be useful.
It may be possible that after a certain time the resistance of the
wrapped cathodes will approach the values of the unwrapped, standard
cathodes. Considering these observations systematic model tests were
iniated to determine the effects of a filtration shield on the resistance
and on the inflow of water to the filters.
Model research configuration no. 3
This configuration was used to further investigate relationships
between resistance and water discharges with gravel filtration shields.
Two models were constructed in containers just as for configuration
no. 2. The initial water content of the tailings was 36.48 percent.
The positive electrode, the anode, was the wall of the container.
The cathodes were a standard filter without a shield (test 7.3.6.) and
a filter with a gravel packing (test 7.3.H).
After installing the filters, both cathode arrangements were fed with
direct and uniform current from two feeders (fig. 28, 29 ). Measurements
included current (l), the corresponding voltage (u) and the water
discharges (Q). The results of these measurements are presented in
tables 10 and 11.
Graphical representation of the change in resistance with times for
the two tests is shown in figure 30. Resistance initially decreased
during both tests. It then rose to values essentially equal.
58
-------
.'3
T- --WWWr- 1 00
rig.78 SCHEMATIC FOR ELECTRICAL SYSTEM USED FOR STANDARD
FILTER (WITHOUT SHIELD) - TEST 7.3. G.
1- contoinar with pulp . 2 - pressure load , 3 - standard filter .
A-D.C. fepcl , 5 - wa'er reservoir
Fig 29. SCHEMATIC OF ELECTRICAL SYSTEM USED FOR FILTER WITH
GRAVEL PACK SHIELD - TEST 7.3.H.
1 - container with pulp . 2 - pressure load , 3 -filter.
4 - gravel packing, 5-D.C.feed , 6 - water reservoir .
59
-------
Further changes in the resistance indicated cracking of tailings and
for this reason are not taken into account.
It was found that the filter packing presents considerable resistance
with electrolyte, i.e. with water discharged under the action of electro-
osmosis. The water discharges of the two tests varied some what
(table 12 and fig. 31) which indicates some restriction to flow caused
by the gravel packing.
Valid comparisons of resistance were obtained during a period of
2 days. Continuation of the tests was not appropriate since the sedi-
ment was cracking. It was therefore decided to perform another com-
parison test of 3 filters with a different arrangement and power supply.
Table 10
Change of resistance with time R = f (T)
Test 7.3.G.
Measure-
ment
1
2
3
4
5
6
7
8
9
10
11
12
13
Current
(A)
0.75
0.75
0.75
0.75
0.75
0.75
0.75
0.75
0.43
0.610
0.750
0.53
0.47
Voltage
(V)
9.6
9.5
9.2
8.8
8.6
14.4
14.7
19.6
21.5
28.8
29.0
29.3
28.7
Resis-
tance
(H)
12.8
12.6
12.2
11.7
11.5
19.2
19.6
26.2
50.0
47.8
38.7
55.3
61.1
Time of sampling
Day
29 Jan.75
_ ii _
__ ii _
_ ii _
_ n _
30 Jan.75
— " _
- " _
31 Jan.75
_ " _
_ " „
1 Feb. 75
3 Feb. 75
Hour
10.00
10.10
10.30
11.40
14.07
9.15
12.10
15.30
9.00
10.30
15.30
7.90
8.00
60
-------
50 55 60 65 70 75 80 95 90 95 100 130 135 14O
*-T(h)
Fig.30 CHANGE OF RESISTANCE (R) WITH TIME(T).
TESTS 7.3.G and 7.3.ff. c-appearance of sediment fissures.
-------
Change of resistance with time R
Test 7.3.H.
Table 11
f (T)
Measu-
rement
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Current
(A)
0.750
0.750
0.750
0.750
0.750
0.750
0.750
0.750
0.750
0.620
0.530
0.200
0.735
1.10
Voltage
(v)
29.5
21.5
19.7
18.7
18.1
17.5
17.0
17.3
28.2
29.3
29.6
30.0
22.5
20.8
Resistan-
ce
(A)
99.2
28.6
26.3
25.0
24.2
23.2
22.7
23.1
27.7
47.3
55.8
60.0
30.6
18.9
Time of sampling
Day
Jan.29,75
Jan.29,75
Jan.29,75
Jan.29,75
Jan.29,75
Jan.29,75
Jan.29,75
Jan.30,75
Jan. 3 0,7 5
Jan.30,75
Jan.30,75
Jan.31,75
Peb.1,75
Peb.3,75
Hour
10.00
10.15
10.37
11.27
11.53
13.02
14.29
9.15
12.10
14.10
15.30
9.00
7.00
8.00
Table 12
Water discharges in time Q = f(T)
Tests 7.3.G and 7.3.H.
Dis-
charge
1.
2.
3.
4.
5.
6.
7.
a.
Time of measurement
Day
Jan.29,75
Jan.30,75
Jan.30,75
Jan.31,75
Peb.1,75
Peb.3,75
Peb.4,75
Peb.5.75
Hour
15.00
9.00
15.30
10.30
10.00
14.30
10.30
13.00
Water discharge in g.
Test 7.3.G.
233.2
538.8
214.5
265.0
164.6
31.9
2.5
2.2
Test 7.3.H
236.8
537.0
277.7
118.0
34.2
66.6
10.6
4.1
62
-------
Ch
9
UJ
10 20 3O 1.0 50 60 70 90 90 100 110 120 130 140 150 !SO 170 180 190 2OO
T(h)
Fi£.31 V/ATES YIELD'S WITH TIME TESTS 7.3.G and 73 H
-------
Pig. 32. General view of test configuration no. 3.
Pig. 33. General view of test configuration no. 4.
-------
Model test configuration no. 4
This investigation was made in cylindrical containers identical to
those previously described with a water content of 36.6 percent.
The configuration was composed of 3 containers connected to the
same circuit. Each container had different cathodes. (Pig. 33).
To avoid the abrupt changes (increases) in resistance caused by
dessication cracks in the sediment, flexible steel strips were used such
that they would remain in contact with the tailings as it deformed
(fig. 34).
The method of providing power to the electrodes was also modified
to avoid differences in the averaged values of the electric current
intensity for any of the 3 cathode configurations (fig. 35).
During the tests the current intensity was varied. Changes were
monitored.
Using the relationship R = —, values of resistance were obtained
(table 13).
The cathode filters tested were: a standard cathode (used in test
7.4.I.), a cathode wrapped in nylon gauze mesh (l x 1 mm mesh used
in test7.4.J^ and a cathode with gravel packing (used in test 7.4.K.).
The nylon gauze wrapping produced the largest amounts of water
(figure 41, table 14). The resistance of the gravel - packed cathodes
rose appreciably (figure 40) and produced less water (figure 41).
Considering that the wrapped filter will sink into the tailings as
easily as the standard filter, the wrapped filter will likely be the more
preferable configuration.
65
-------
Fig.34 SCHEME OF TEST CONFIGURATION No 4
I.II.Ill - containers , 1 - filtercothode , 2 - onode .3- insulating foil. 4- nylon gauze . 5-washers .
6-lead, 7- base . 8-tailings . 9- gravel packing . 10- water catchment vesiel.
-------
Rg.35 SCHEME OF ELECTRIC CONNECTIONS OF TEST CONFIGURATION No*
1 - DX feed . 2 - cathode without filter . 3 - cathode with nylon gauze .
4 -cathode .with gravel packing •
-------
Pig. 36. Element of test
configuration no. 4.
Pig. 37. View of surface of the container during tests —
filtercathode without filtration shield (configuration
no. 4).
68
-------
Pig. 38. View of the container surface during the tests -
filtercathode shielded with nylon gauze (configuration
no. 4).
Pig. 39, View of the container surface during tests - filter -
cathode surrounded by gravel packing (configuration
no. 4).
69
-------
Table 13
Model configuration no. 4
Resistance change in time R = t(T)
Mea-
sure-
ment
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
Current
(A)
0.250
0.295
0.258
0.220
0.240
0.245
O.278
0.140
0.178
0.218
0.217
0.290
0.295
0.274
0.218
0.295
0.252
0.305
0.250
0.225
0.305
0.330
Voltages
Ul
(v)
3.5
3.2
2.7
3.0
3.4
3.9
4.4
3.0
3.4
3.8
3.7
4.8
4.8
4.6
4.2
5.4
5.1
6.0
5.8
6.4
7.4
10.0
U2
(v)
4.3
4.5
3.9
4.2
4.4
5.9
6.6
6.3
8.2
10.5
12.0
17.8
17.8
14.2
7.5
11.5
9.6
11.7
10.4
7.9
8.4
21.8
U3
(v)
5.7
5.8
4.8
4.6
6.8
7.9
9.7
9.9
14.9
21.0
24.6
33.6
32.9
36.7
44.0
40.0
51.0
56.0
57.0
63.5
67.5
59.0
Resistance
R.«
Oft)
14.0
10.7
10.7
13.6
14.3
15.9
15.8
21.4
19.1
17.4
17.0
16.5
16.3
16.8
19.3
18.3
20.2
19.7
23.2
28.4
24.2
31.5
R2
(fl)
17.2
15.5
15.5
19.1
28.5
24.0
25.7
45.0
46.0
48.2
55.4
61.5
60.4
52.0
34.2
39.0
38.0
38.4
41.6
55.0
30.8
66.0
R3
(H)
22.8
19.6
19.0
20.0
28.4
32.2
34.7
70.7
84.0
96.5
113.0
114.0
112.5
134.0
202.0
135.0
202.0
184.0
228.0
282.0
221.0
179.0
Time of
measurement
Day
Mar.19
Mar. 19
Mar.19
Mar. 20
Mar. 20
Mar. 21
Mar. 21
Mar. 21
Mar. 2 5
Mar. 2 6
Mar.27
Mar. 2 8
Mar. 2 8
Mar. 2 9
Apr. 1
Apr. 1
Apr. 2
Apr. 2
Apr. 3
Apr. 4
Apr. 4
Apr. 5
Hour
12.00
13.00
14.00
7.30
14.30
8.00
15.0O
7.00
7.30
7.30
7.30
9.00
15.00
8.00
8.30
15.00
7.00
13.00
8.00
8.00
14.00
10.00
-J
o
-------
Table 14
Water discharges with time CD = f(T)
Tests 7.I.I., 7.4.J., 7.4.K.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Time of measurement
Day
Mar. 19
Mar. 19
Mar. 20
Mar. 21
Mar. 21
Mar. 24
Mar. 25
Mar. 26
Mar. 27
Mar. 28
Mar. 29
Apr. 1
Apr. 4
Apr. 5
Hour
12.00
15.0O
7.00
8.00
15.00
7.30
7.30
7.30
7.30
9.00
8.00
8.30
8.00
10.00
Water discharge in g
Test
7.4.1.
0
50.6
202.3
260.0
48.0
98.0
26.1
14.8
8.1
16.1
4.6
7.8
13.8
93.0
Test
7.4.J.
0
55.9
219.8
256.0
65.4
278.0
61.3
48.1
37.1
53.9
11.0
12.8
14.3
66.9
Test
7.4. K.
0
53.8
216.1
193.0
52.8
128.0
50.2
43.8
33.8
63.6
4.1
8.2
9.2
46.6
71
-------
to
UJ
10 «„ 30 , „ 50 _„ 70 „ SO
130 ... 150 lfn 17O .an 1BO ,~,~ 210 „„ 230
i.0 ~ 60 ' 80 " 100 110—140 '- 160 "" 190 '"300— 230™ 24O — 260* " Z8O*~ 300*'" 320*™ 34O—360— 380 — 40O
rig.AO CHANGE IN RESISTANCE (R)WITH tKE(T). TESTS 7.i..| ,7.4.J , 7.4.K
TIME
-------
Qw(cm ) M
co
UJ
>
IT
UJ
50 jo ?b so K ,00"° 120 ™ 140 '*« 160 "° 180 »° 200 ™> 220 °° 240 iso 250*" 280 'M 3COJM 320 B0 340^360 i7D 3SO 39° 40O 4'°420
TIME
. T(h)
WATER YIELDS WITH T!ME-TH3T.S 7.4 ) ,74.3 , 7.i.K
-------
INVESTIGATIONS OP CHANGES OCCURRING IN THE SEDIMENT
STRUCTURE DURING ELECTROOSMOTIC DRAINAGE
Method of investigations
The research work program comprised observation of microscopic
changes in the sediment structure. Investigations of the influence of
structural changes on the efficiency of electroosmotic draining perfor-
med while current was applied to the tailings.
Microscopic investigations
A polarizing microscope of Amplival type (Carl Zeiss) with a
transposing set and basic micro-slide apparatus with copper electro-
des was used.
The sediment samples were magniffied from 156 to 720 times. The
field force of various tests was varied at 0.23 V/cm, 0.5 V/cm, 1 V/cm
and 2V/cui.Por each field force 3 test versions of current application
were performed.
a) constant current
b) change in direction of current
c) intervals in current supply.
Each test was repeated 5 times on fresh tailings. Sixty tests were made,
not counting the first trials. The sediment samples were moistened with
1.5 g of the water that was drawn off the field site. In effect a trans-
parent suspension was formed and the increased surface tension pro-
fived adherence.
With magnifications of over 240 times a problem occurred since the
covering glass obstructed the microscope lens. The covering glass had
to be removed from its frame. This allowed increased evaporation of
the suspension and observations were limited to 10 min.
In addition to these observations of tailings during electroosmos i s,
sediment subjected to previous electroosmosis in a laboratory reservoir
74
-------
FigA2 ELECTRICAL WIRING DIAGRAM USED FOR SIMULATING
ELECTROOSMOTIC DEWATERING OF TAILINGS EXAMINED
UNDER THE MICROSCOPE-
1.2 - output . 3 - input
75
-------
were examined. These samples were collected (at selected times) from
locations near the anode the cathode, and from the middle of reservoir.
Investigations performed on miniature reservoir
The laboratory reservoir was a plastic vat. The bottom of the vat
was fitted with iron pipes with slit perforations, which served as elec-
trofilters. These filters were wrapped with a double layer of nylon
gauze to keep sediment out. The electrodes were fed from the same
electrical arrangement used for the microscope observations. The
reservoir was placed on a stand which permitted easy access.
A schematic of the reservoir is presented in fig. 43.
Microscope observations of the effects of electroosmosis
Microscopic analysis showed the undrained tailings to have a typi-
cal aggregate structure. Individual grains have small to average diame-
ters. Large grains do not appear within the clay-silt aggregate. Rather
the tailings skeleton is composed of aggregates of small particles and
individual larger grains. The pore spaces range up to 0.03 mm in
diameter. The mineral particles in aggregates do not show a preferred
spatial orientation (geometric), nor any optical pattern (fig. 44).
A temporary and local movement of material and a reorientation of
grains is observed for a short period after the solution is prepared.
The observations were carried out using the variations of current flow
discussed in the following sections.
Electric field with intensity E = O.23 V/cm
a) constant current
Upon application of the D.C. voltage, the following phenomena occur:
- individual grains migrate toward aggregates of smaller particles and
become incorporated therein. The migration is step-wise toward the
nearest anode or cathode
76
-------
Fig.43 SCHEME OF LABORATORY SEDIMENTATION BASIN USED
TO INVESTIGATE CHANGES IN TAILINGS SEDIMENT STRUCTURE.
K - cathodes, A-anodes. 1-measuring cylinders ,2 -gauze,
3 - rubber connections , U - clamps supporting electrodes
S - location of sample collection for microscope tests.
77
-------
- grains within the aggregates rotate in a sporadic step-wise manner
- a "cell-like" structure is created around the pores with diameters
exceeding a number of times the diameters of grains, by chains of
aggregates which may surround pores (fig. 48),
- stabilization of skeleton (after 9 to 10 min. of voltage application);
b) Changes in the direction of current (change of poles)
In the initial phases, i.e. immediately applying the voltage, the
tailings behave as described for case a. At the first signs of stabili-
zation the direction of electric current flow was reversed. This did
not produce the expected changes in particle movement but instead
no changes were initially observed. After a period of about 1 minute,
sporadic rotations of single grains located in external parts of aggre-
gates were observed. These movements did not persist. The current
was reversed every 3 minutes. After each successive change sporadic
the rotations became progressively less frequent and. after a fourth
change, no movement of the grains was noted.
c) Intermittent flow of current
In this test, the current flow was interrupted every 3 minutes.
A constant value of current was applied and the intensity of the field
was kept the same. The test involved 3 periods of current flow and
3 periods of no current flow.
The observations may be described as follows:
- The first period of current flow was characterized by phenomena
similar to those in case a;
- Pause. When the current was turned off, there were no changes in
the particle distribution. On the average of 15 seconds into the
cessation of current, some components of the skeleton rotated and
there was a spreading of the aggregates, probably induced by loo-
sening of the intergrain bonds in aggregates;
78
-------
- Resumed flow of current. Rotation of single isolated grains. Compac-
tion of the structure of aggregates. Migration of a few grains and
aggregates toward the electrodes. Stabilization of the structures.
Electric field with intensity E = 0.5 V/cm
a) Constant flow of current
Application of a higher field intensity (E) produced structural
changes in the tailings analagous to those observed at lower intensi-
ties. The only differences observed were the intensity and duration of
movement. The following phenomena were observed:
- the migration of individual grains toward the aggregates of small
grains and a decrease in inter—grain spaces within aggregates
- the rotation of grains within aggregates
- the migration of individual grains toward the electrodes
- the formation of cell-like structure
- the stabilization of the structural skeleton.
These movements were observed to occur -with greater intensity in
the case of a lower field intensity, i.e. more grains moved within the
suspension. But the movements stopped earlier, and the structural
skeleton appeared stable after 6 to 7 minutes.
b) Varied direction of the current flow
Regular reversal of the polarity of the current field caused particle
movement similar to that observed, under the lower intensity field.
Sporadic rotational movements of individual grains within the aggrega-
tes, and occasional rotational movements of whole aggregates were
observed.
79
-------
c) Intermittent flow of current
Interruption of current caused a partial disruption of structural
rearrangement of the particles. During the periods of no currents, the
following movements were observed:
- the rotation of certain components, and
- a loosening of aggregates.
Upon resumption of current flow, agglomeration of the aggregates
reoccurred.
Electric field with intensity E = 1 V/cm and E-2V/cm
These tests were carried out following the previously described
scheme. Despite higher gradients of voltage, the observed changes
were of a similar nature as those previously described. The noticeable
difference was the shorter time required to achieve structural stabili-
zation.
The qualitative character of these structural changes is shown by
fig. no. 49.
Electric field with increasing intensity, (E) from 0.23 V/cm to 2 V/cm
Microscope observations of structural changes were also made as
the electric field was varied in a step—wise manner. Each field intensity
was applied for 3 minutes. Three sets of step-wise increases were
used as follows: 0.23 - 0.5 -IV cm; 0.5 - 1.0 - 2.0 V/cm and
1.0 - 2.0 V/cm.
It appears from observations of these tests that the tailings struc-
ture can be more easily activated (mobilized) using higher field inten-
sity (E). However mobilization of the particles by step-wise application
of a higher E does not cause an intensive movement characteristic
of the previously-described applications of consistently high intensities.
The first field intensity trial (i.e. from 0.23 to 0.5 and 1.0 V/cm did
not give visible results.
80
-------
Pig. 44. Structure of tailings before electroosmosis.
Light color-water, dark - sludge. Nicols II
Magnified 270 times.
Pig. 45. Aggregate structure at start of the electroosmosis
process, light color-water, dark - sludge.
E = 1 V/cm. Nicols II, Magnified 270 times.
81
-------
Pig. 46. Increased size of aggregated particles and trans
formation to cell-like structure, E=l v/cm. Nicols II
Magnified 270 times.
Pig. 47. Unstabilized cell structure. E = 1 V/cm. Nicols II,
Magnified 270 times.
82
-------
Pig. 48. Stabilized cell structure with captive solution or gas,
E = 1 V/cm. Nicols II, Magnified 270 times.
10 V/cm
0,23 V/cm
TIME
Pig. 49. Qualitative diagram of structual changes intensity
in time.
83
-------
Laboratory investigations carried out in simulated reservoir
Investigations of the dewatering phenomena were performed in the
small laboratory reservoir using electrical fields of intensities the same
as those used for the microscope observations (E = 0.23 V/cm and
0.5 V/cm). In addition a single test "was performed under conditions of
an increasing electrical field intensity.
Measurements of the rate of solution discharge (Q/t) from the
laboratory reservoir were carried out to compare the rate of electro-
osmotic draining with the observed changes in the structure of the
tailings material. Independent of the measurements of discharge, mea-
surements of changes in the water content of the tailings were also
conducted.
These tests were performed on tailings collected from the sedi-
mentation basin of Ogorzelec. The samples were collected from the
area between the anodes and cathodes from depths of 0.5 to 0.8 m.
Each test in the laboratory reservoir was conducted on a fresh
sample of tailings. The tailings were allowed to drain for two full days
prior to testing. The results of these tests are described in the follo-
wing sections.
Electric field with intensity E = 0.23 V/cm
a) Constant current flow
All the tests lasted for 221 hours, not including the preceding two
days provided for gravitational drainage. The maximum drainage flow
occurred 6 hours after application of current to the laboratory reservoir
(9.5 ml from three filtercathodes per 1 hour).
After that value was reached, the yield of fluid began to slowly
decrease. Between the 29 and 31 hour of the test an increase in
yield of short duration (maximally 8.5 ml/h) was measured. After
216 hours of current flow no discharge was evident.
84
-------
The change in drainage with time is shown on fig. 50. The surface
of the tailings formed cracks as the draining progressed.
Within the first phase of this test the drainage was almost colo-
urless, and contained a small amount of suspended material which
quickly settled out. Starting at the 9 hour of the tests, the solution
became canary yellow and then progressed to a willow-green colour,
and, after 40 hours, it was dirty-green. Still later the drainage became
pale brown, but by the end of the test it was again colourless and
clear.
After a week the various colours of the drainage, which was stored
in open containers, disappeared. A whitish "sediment" was deposited
in the bottom of the sample containers and was observed at the sur-
face of the water sample.
Samples of the tailings taken 50 hours after electroosmosis and
examined under the microscope showed that little, transparent solution
rings were formed around the grain aggregates. These are gel-like
and turbid. These' grains are spherical, as a result of chemical corro-
sion and not of any rolling action. Despite high sphericity degree the
grains closely adhered to one another (fig. 47).
The gel-like rings disappeared with time (tests after 170 hours
of experimentation). Most likely they may have undergone a transfor-
mation during coagulation or crystallization processes. The character
and the advancement of chemical processes were difficult to estimate.
b) Variable direction of current flow
Another tailings sample was subjected to reversals of polarity
every 24 hours. The intensity of the electric field was kept constant
at E = 0.23 V/cm. During the first full day the color of the drainage
and the rates of drainage were similar to those of the previously -
described experiment (a) (see figure 51).
At the moment of the current reversal (i,e. when a cathode became
an anode, and anode became cathode) the rate of water outflow decre-
85
-------
20 U> ' 60 K CO 120 140 »0 180 200 220
TIME
Fig. 50 CHART OF WATER DISCHARGE RATE FROM CATHODES.
CONTINUOUS FLOW OF CURRENT E-O,23V/cm
| [h J
10 20 30 00 50 60 TO BO 90 100 I [h]
TIME
Fig. 51 CHART OF WATER DISCHARGE RATE FROM CATHODES.
VARIABLE DIRECTION OF CURRENT PASSAGE E-O.23V/on
a - time of chonge in direction of current passage
20 W 60 BO ttO 120 »0 SO HO 200 220 '
Fig. 52 CHART OF WATER DISCHARGE RATE FROM CATHODES.
INTERMITTENT FLOW OF CURRENT E-0.23V/cm
P - tim« of interruption in current flow.
86
-------
ased almost by half (fig. 5l). By the fourth hour after the reversal
the drainage had increased almost to the value measured before the
reversal. Then drainage began to slowly decrease.
The second polarity reversal (after 48 hours) also caused a
sudden reduction in the discharge,' which after 50 hours of test began
to recover. A maximum was achieved in the 52 nd hour, and afterwards
the water outflow decreased. The discharge at the end of this rever-
sal period (72 hours) was, however, higher than during the 48th hour
of the test.
After the third reversal of current, the discharge decreased again,
but subsequent changes in the current flow direction did not produce
measurable changes in the solution outflow rate. The test lasted for
103 hours.
c) Intermittent current flow
This test examined the effects of regular interruptions of current
on the drainage. The current interruptions normally lasted for 2 hours
after 22 hours of current application. A constant electric field intensity,
(E = 0.23 V/cm) and a constant direction of current flow was employed.
During the initial application of current, the outflow was the same
as observed for the previously described experiments. After cessation
of current the outflow decreased slightly from 9 ml/h to 7-9 ml/h, and
during the two-hour period it stayed at this range.
At the moment of current reapplications the discharge began to
increase to 12.5 ml/h during the second hour after reapplication. Then
the drainage decreased again. Further investigation shows that interrup-
tions in the current supply cause-a slight decrease in flow which is
followed by an increase when the current is reapplied. The increase
may amount to two times the flow rate existing immediately before the
cessation of current. The character of the changes in discharge is
illustrated in fig. 52.
87
-------
Electric field with intensity, E = 0.5 V/cm
Tests employing an electric field intensity (E) of 0.5 V/cm were
carried out in the same manner as those using E = 0.23 V/cm, i.e.:
a) with constant current flow
b) with varied direction of current flow
c) with intermittant current flow.
Generalizing the results, it can be said that no significant differences
in reaction were observed with the exception that the quantity of water
discharged was greater in the case of the higher field intensity. The
values of discharges resulting from the higher field intensity are pre-
sented in figures 53-55.
Step-wise increases in the electric field intensity (E) from 0.23 V/cm
to 1 V/cm
These tests were initiated with the lowest field intensity E =
= 0.23 V/cm. After 91 hours of electroosmosis the intensity of electric
field was raised to E = 0.5 V/cm. This value of E was maintained to
the 139 th hour. Then the electric voltage was increased to E-l V/cm.
This value was maintained through the 216 th hour and then the test
was concluded.
The changes in water outflow with increasing electric field intensity
(E) are shown on fig. 56. It appears that due to the progressive
increases in the field intensity there was prolonged drainage such that
a greater quantity of water was discharged than during the other tests.
Correlation of microscope observations and drainage measurements
using the laboratory reservoir
Electroosmosis produces different reactions in differing unconsoil-
dated materials. It is therefore necessary to investigate these differen-
ces prior to installation of a drainage system in the field so as to
obtain optimal drainage. The model tests conducted in the laboratory
88
-------
Q/t
J 16 '
Vt •
III 1?
tJ 10
oc ^
- t.
5
-J ,
U. '
M
"-
(
\
!
~
i
LJ
I r
s. J
^-J*
\
\
^
\
fVi_;
"~v\
m w so eo wo no no » 'M
TIME
Fig-53 CHART OF WATER DISCHARGE RATE FROM CATHODES
CONTINUOUS CURRENT PASSAGE E-O.5V/cm
Q/t
[ml/h]
ill
In
V
/ •
i
***- *>
\
V
y
fi
- — ^ —
-i —
-uf
-vv-
5 >•'-—
0 10 20 30 (.0 50 60 70 80 .r-.-,
TIME
Rg.54 CHART OF WATER DISCHARGE RATE FROM CATHODES.
VARIABLE DIRECTION OF CURRENT FLOW E»0,5V/cm
0 - time of change in current flow direction
Q/t
(mini]
5
o
Fig.55. CHART OF WATER DISCHARGE RATE FROM CATHODES.
INTERMITTENT FLOW OF CURRENT E-O.5V/cm
P - time of interruption in current flow.
89
-------
Q/t 1
[ml/h]
16 •
1! -
£ ,0.
2 ••
6 -
5 ...
9 -
E- 0,23 V/em I E-0,5 V /cm
^
r-=
i_— — — • (
-----
3F
P—^
rv^**^
P"
—
E- 1,0
L
-IU
._..
V/cm
N;
^
0 20 (tO 60 80 100 BO WO 160 180 300 220 1 [ h]
TIME
Fig. 56 DIAGRAM OF WATER DISCHARGE RATE FROM
CATHODES WITH GROWING ELECTRIC FIELD INTENSITY ( E )
09
©
0
Fig. 57 WATER CONTENT TO DEPTH OF 5 CM OF TAILINGS IN
LABORATORY SEDIMENTAT ION BASIN AFTER 283.5 HOURS
OF CURRENT PASSAGE WITH INCREASING FIELD INTENSITY
FROM 0.23 TO 1.0 V/cm
"1.2 14 -points of sample collection
.—-35 -line of equal humidity values{35% )
9O
-------
reservoir and the microscope observations of structural changes during
electroosmosis provided much information in this regard. Through com-
parison of the changes in structure with the drainage rates showed
that for the tailings material, the drainage rates are related, to a large
degree, with the structural modifications of the sediment during passage
of the current. Presented below are tables giving a summary of corres-
ponding discharge characteristics and structural changes during elec-
troosmosis:
a) Continuous flow of current applied to tailings
Drainage - water outflow
Test made in laboratory reservoir
Structural changes
Observed under microscope
Elapsed
time of tests
Discharge rate
Manifestations of structural
rearrangemept
Start of elec-
trodrainage
Systematic incre-
ase in rate of
water outflow-
Migration of some individual grains
to existing aggregates of particles,
Reorientation of individual "loose"
grains and of grains in aggregates
4-8 hours
Maximum discharge
rate
As above. Compaction of structure
into aggregates of particles.
Formation of large pore spaces
within these aggregates
8-26 hours
Discharge decre-
ased
Reorientation of single grains.
Partial colmatation. Rings of gel-
like substances formed around
the aggregates
26-50 hours
Initial increase in
discharge followed
by a systematic
drop in discharge
rate
Reorientation of single grains.
Compaction of aggregate structu-
res. Formation of additional voids,
Smaller quantity of gel-like rings.
Formation of cell-like structure
About
50 hours
Short duration
increase in dis-
charge rate
Further reorientation of individual
grains. Sporadic occurrence of
gel rings (probable partial lea-
ching and partial coagulation of
gels). Local voids within cells
filled with solution
91
-------
Drainage
1
Final phase.
To 221 hours
2
Systematic decre-
ase in discharge
rate until discharge
cleared
Structure
3
Par advanced colmatation of
inter-aggregate spaces. Cell-like
structure. Stabilization of struc-
ture
b) Varied direction of current flow applied to tailings
Drainage
Structure
0—6 hours —
Start od elec-
tro-drainage
Systematic incre-
ase in water out-
flow
Migration of some individual
grains to the existing aggregates
of particles. Reorientation of
individual grains. Sulphosis.
Formation of large pore spaces
6-24 hours
Slow decrease in
discharge with
time
Reorientation of single grains.
Partial colmatation
25-48 hours-
Reverse di-
rection of
current flow
Distinct decrease
in discharge rate
Reorientation of some individual
grains and whole aggregates.
Local "loosening" expansion of
structure. Stabilization of struc-
ture •with, increasing time
49-72 hours-
R eve rs e dir e c-
tion of current
flow
During first 2 hours
a significant decre-
ase in discharge.
Later on an incre-
ase in discharge
to the equivalent
of the previous
day.
Reorientation of components.
Sporadic movement of aggregates.
Progressive stabilization of struc-
ture
73—96 hours-
reverse direc-
tion of current
flow
Decrease in dis-
charge rate
Reorientation of individual grains,
formation of cell-like structure.
Structure stabilization.
97-103 hours-
Successive
changes in
current flow
direction
Low discharge
rate maintained
Cell-like structures formed.
Structural stabilization
92
-------
c) Intermittent flow of current applied to tailings
Drainage
Structure
2
0-24 hours -
Continuous
current
A steady increase
followed by a de-
crease in the
discharge rate
Aggregation and reorientation of
grains. Suphosis. Formation of
large pore spaces. Partial colma-
tation
25-26 hours
First break in
current supply
Decrease in solu-
tion discharge rate
Reorientation of some grains.
Loosening of intergrain bonds with
aggregates. Partial decolmatation.
27-48 hours-
Resumed
current flow
Initial increase in
discharge, fol lo-
wed by a decrease
Aggregation and reorientation of
grains. Suphosis. Formation of
large pore spaces. Colmatation
49-50 hours-
Second break
Decrease in dis-
charge rate
Reorientation of grains. Loosening
of aggregates. Partial decolmata-
tion
51-119 hours-
Resumed
current flow
Increase in rate
during first three
hours then a gra-
dual decrease
Occasional reorientation of grains.
Extensive compaction of structure
in aggregates. Colmatation.
Formation of cell-like structures.
120-121 hours
Third break.
Discharge rate
decrease.
Reorientation of individual grains,
partial decolmatation and splitting
of some cell structures
122-143 hours
Resumed
current flow
At first rapid incre-
ase in discharge,
then a slow decre-
ase
Reorientation of individual grains.
Compaction of aggregates. Forma-
tion of cell-like structures.
Stabilization of structure.
Successive
interruption
in curren t
flow up to
the 223-rd
hour
Similar as in third
break and subse-
quent period of
current flow as
previously descri-
bed
Continuation of structural modifi-
cations described for preceding
period
b) Increasing electric field intensity applied to tailings
Drainage
1
Through 92 nd
hour-0.23 V/cm
2
Same as described
for continuous flow
of current
Structure
3
Same as described for
flow of current
continuous
93
-------
Drainage
1
93-139 hours-
0.5 V/cm
140-216
hours -
1.0 V/cm
2
Initial increase in
solution discharge
rate followed by
a decrease with
time
As ab ove
Structure
3
Reorientation of individual grains.
Reconstruction of some aggrega-
tes. Development of voids among
aggregates. Formation of cell-like
structures. Stabilization of struc-
ture
As above
Summary of the test results
a) The effect of electroosmosis in tailings material differs according
to the character of the electric field (constant, varied, periodically
interrupted).
b) The internal structural changes occurring during electroosmosis
have great influence on the effects of water discharges. These struc-
tural changes are:
- re orientation of the particles
- migration of grains toward the electrodes
- aggregation of grains
- suphosis
- formation of cell—like structures
- chemical corrosion of grains
- stabilization of the structure in its rearranged form.
c) The least favourable version of electroosmotic draining is that
where the direction of current flow is periodically reversed. Changes
in direction of current flow caused insignificant rearrangement of the
structure. But the solution which had migrated during current passage
in one direction was forced to retrace its flow path when the current
was changed. Therefore drainage from the interior of the tailings was
quite limited. With each change in the direction of electric current,
drainage was reduced.
94
-------
d) The highest drainage rates occurred during the tests of perio-
dically interrupted current supply. During interruptions in current supply,
a partial "splitting" of the aggregated particles occurs and allows the
solution to move. When the current supply is resumed, the water is
initially free to move to drainage points. Drainage continues until the
aggregate structures are again formed. Each successive break in current
causes freeing of a portion of the captive water. This water has a
very limited potential to be recaptured by the sediment.
e) Some structual changes of the sediment result from chemical
reactions. The chemical processes infrequently observed to take place
in sediment included: corrosion of grains, formation and disappearance
of gel-like rings around aggregates, and changing colours of discharged
solutions.
f) Once stable cell—like structures and compact aggregates are
formed the drainage of water (solution) stops, despite high water
content of the sediment. The water is confined in these structures. To
further reduce the water content, these structures must be broken.
This is partially accomplished by the periodic interruptions of current.
ADDITIONAL MEASUREMENTS AT FIELD SITE
In order to answer a number of questions that arose during the
laboratory tests, additional tests were performed directly at the tailings
disposal site. These tests started with measurements of specific resis-
tance of the sediment.
Its value was determined to be 4.6 . 10 O. /cm. The surface of
electrofilters, the spacing between them and the type of material to be
used was also investigated in the field. Electrodes constructed of alu-
minium with diameters 50.125 and 150 mm, were driven into the tailings
to a depth of about 2 m with spacings of 5 and 10 m. Steel electro-
des, with diameters of 200 mm were also tested (Tests I to VII ).
Detailed results of these tests are presented in table 15.
95
-------
Table 15
Electrical resistance of tailings as a function of
various electrode construction,1 spacing, depth,
voltage and current intensity
(Tests I to VII
Test
no.
I
II
III
IV
V
VI
VII
Electro-
de
diameter
(mm)
50
125
200
50
125
150
200
Length
of elec-
trodes-
depth of
sinking
(m)
2.40
1.90
1.90
2.30
1.90
2.0
1.90
Spacing
of
electro-
des
(m)
5
5
5
10
10
10
10
Applied
voltage
(v)
35
53
46
74
57.5
48
23.5
Current
intensity
(A)
5
10
10
10
10
10
5
Electri-
cal
resistan-
ce
CQ)
7.0
5.3
4.6
7.4
5.75
4.8
4.7
Material
of elec-
trodes
aluminiun
aluminiurr
steel
aluminium
aluminium
aluminiun
steel
Additional initial tests were made with steel electrodes sunk to a
depth of 7 m, spaced 10 m apart, in two configurations: one anode and
one cathode (electrical resistance amounted to 1.9.Q ), and one anode
with two cathodes (electrical resistance was 1.36 H).
These same arrangements were tested for a fortnight and electric
resistances increased to 2.1 12 and 1.4lH respectively. These incre-
ases in resistance (by about 10 %) were caused by the corrosion of
the steel pipes, some thing one has to deal with in draining a sediment.
These investigations showed that the electrical resistance, notably
the most essential value to permit efficient design of an electro osmosis
system, must be calculated from field tests.
The results of the field tests were used to design an electroosmosis
dewatering system for installation in the smaller of the two tailings piles
at Ogorzelec.
96
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ELECTROOSMOTIC EXPERIMENTAL STATION CONSTRUCTED ON
THE SMALL SEDIMENTATION BASIN IN OGORZELEC
In the process of initial tests made on the laboratory reservoir,
and the investigations on the main sedimentation basin, large divergen-
ces between the laboratory and the field values of electrical resistance
were measured. Differences were also found between the laboratory,
and field water discharges. In order to acquire the data necessary to
design an adequate drainage system for the main sedimentation basin
in Ogorzelec an electroosmotic system was installed on the small sedi-
mentation basin containing the same and identically stored sediment
and located adjacent to the main basin.
The installation was constructed in accordance with the diagram
of fig. 58. It consisted of 4 steel filtercathodes, 6 m long, with 34 cm
diameters. Filter — cathodes were perforated with 4 mm diameter holes
in a 100 x 100 mm pattern.
The anodes consisted of pipes with 10O mm diameters, were 6 m
long and were not perforated.
The filter - cathodes were sunk along the axis of the sedimentation
basin, at 1O m intervals, and were surrounded by 20 anodes, located
11 m from the axis of the filtercathodes.
The number of anodes was chosen so that the sum of their surfa-
ces would be approximately equal to the sum of surfaces of the filter-
cathodes.
Groups of anodes and cathodes were connected with a copper lead
of a 25 mm2 section. These leads were supplied from an 80 ampere
supply.
Initially no voltage was applied to the electrodes, in order to observe
eventual discharges of water expected to take place without electroosmo-
sis.
Por a period of one and a half month there was no discharge of
water observed. Thus it was demonstrated that it was not possible to
97
-------
Fig.58 PLAN OF THE SMALL SEDIMENTATION BASIN
SHOWING LOCATIONS OF ANODES AND CATHODES
explanation
altitude point on the ranstruction
L J mssofifij bt/tltfing
(*J deciduous (rpp
O cat-bodes
• • anodes
98
-------
collect any water at the electrodes through natural drainage.
A voltage of 40 V was then applied to the electrodes. This caused
a flow of current (82 A) between the electrodes. Assuming a uniform
current propagation, this is equivalent to 20.5 A per filter-cathode.
After current application for 18 hours ' measurements made of the
water columns in the filter cathodes gave the following results:
A-well - 24 cm, B - 52 cm, C - 53 cm, D - 63 cm. Calculating volu-
mes gives 6.6 liter; 14.3 1; 14.5 1; and 17.3 1 respectively.
The accumulated water in wells was pumped out and to find out
whether the application of current would result in gravity drainage, the
voltage was removed. The water levels indicated that the discharge
rates decreased to nil over the four hour period that current was not
applied. The voltage was reapplied and systematic measurements of
the water level increments continued for 18 days, at dates provided
in table 16.
Table 16
Increments of water level in 12 hrs measurement periods (in cm)
Date of
measure-
ment
Apr, 30
May 2
May 4
May 6
May 9
May 13
May 16
May 18
w e 1 1 s
A
22
26
25
20
21
26
27
28
B
78
41
62
53
50
56
58
58
C
69
43
60
60
65
63
67
65
D
83
84
90
80
83
86
89
90
Measurements of the water inflow rate in consecutive days of the
research period were performed according to foEowing plan:
- pumping out of accumulated water in well,
- measurement of water table level in emptied wells
99
-------
- repeated measurements of water table level after 12 hours time
In order to determine the electroosmotic actual water discharges
from a well measurements were made (table 16) only for periods in
which no precipitation occured. After 18 days of operation, on May 19
the voltage was again removed from the electrofilters and water was
removed from wells. The water levels were observed during following
14 days and found to systematically decrease (table 17).
Table 17
Increments of water level in 12 hrs measurement periods
after switching off current ( in cm)
Date of
me as ur ement
May 20
May 21
May 22
May 23
May 27
May 29
Jun. 1
Jun. 3
Jun. 5
Wells
A
20
20
18
16
10
9
5
0
0
B
40
38
36
30
25
20
15
5
0
C
50
43
40
40
35
30
20
10
0
D
60
60
60
60
50
45
40
20
i
5
This experiment showed that after a long period of electro osmosis,
gravity drainage may continue for a while, but will decrease with time.
The reduced drainage can be attributed to the plugging of the particle
skeleton of the tailings. When after emptying of wells on June 8 the
voltage was reapplied, water began to discharge again. However, the
discharge rates were essentially equal (table 18).
100
-------
Table 18
Increments of water level in 12 hrs measurement
periods after resumed voltage application on the
electro-filters (in cm)
Date of
measurent
Jun. 10
Jun. 11
Jun. 13
Jun. 16
Jun. 19
Jun. 20
Jun. 23
Wells
, A
10
9
10
10
11
11
12
B
10
10
10
11
12
12
13
C
11
10
10
11
11
11
12
D
12
12
12
11
12
13
13
After repeated reapplied voltage on June 8, was observed that
water collects not only in the cathode wells, but also in depressions
formed around the filter - cathodes. The quantity of this water was
difficult to measure. Its presence suggests that the holes in the filter-
cathodes were plugging. Further, of this phenomenon indicated the
cathodes were corroding during the period when no voltage was applied.
Corrosion caused visible plugging of the small (0 4 mm) perforated
holes in the electrofilter. Therefore the water attracted to the electro-
filter is forced to the surface through voids formed by escaping gases
produced in the process of electrolysis. In the light of these observa-
tions we believe that current should be applied to the filters immedia-
tely after their emplacement in the sediment, and that current should be
maintained throughout the entire time of operation. In this manner the
corrosion is controlled and the gases pass through the perforated holes
thereby keeping them unplugged.
In the course of collecting samples for water content determinations
toward the termination of the tests, it was noted that the force nece-
ssary to drive the sampler into the tailings increased. If this increased
101
-------
structural resistance was to be explained only by a decrease in water
content, the areas of tailings located adjacent to the cathodes, where
water accumulates, should be easier to penetrate. However, these are-
as were not easier to penetrate.
In order to investigate this phenomenon, the chemical compositions
of samples were measured. Samples from areas near the cathodes were
compared with samples from between the electrodes. The results are
presented in table 19. These comparisons did not reveal any signifi-
cant differences. It was concluded that the increase in strength of the
tailings could be explained only by increased stabilization of the struc-
ture ("petrifaction") throughout the area affected by electroosmosis.
Table 19
Chemical composition of selected tailings samples located
within, the electroosmotic zone of the small tailings pile
at Ogorzelec
sinter, losses
Si02
Fe2°3
CaO
MgO
S°3
Sample B taken
by cathode
27.70 %
9.80 %
0.74 %
4.10 %
40.00 %
1.30 %
16.33 %
99.97 %
Sample D - zonej
between the electrodes
25.80 %
9.35 %
0.44 %
3.55 %
41.80 %
1.80 %
17.22 °/o
99.96 %
During the course of current application and drainage a systematic
subsidence surface of tailings pile in the experiment area was noticed.
The measurements showed that in relation to the initial elevation the
sediment surface was lowered an average of 15 cm. This is attributed
to compaction attendant on the loss of water. One may then estimate
102
-------
Pig. 59. Electroosmotic test area on the small sedimentation
basin - after completion of drainage tests.
Pig. 60. Emplacement of s'yphon in bowl of main
sedimentation basin.
103
-------
the total quantity of "water removed from the tailings from the amount of
3
subsidence at about 150 m if all subsidence is the result of water
drainage.
Approximately 800 kVh of electrical energy were used during the
experiment. This is the total energy, including energy used for electro-
osmosis and to operate the pumps. Therefore using the 150 m as
o
the amount of -water removed, the unit energy requirement was 5.3 kVh/m .
The following conclusions were drawn from the tests conducted on
the small tailings pile and influenced the design of the drainage system
for the large (main) sedimentation basin.
- Wells placed in the tailings will not accumulate water unless electro-
osmosis is used.
- After application of an electrical field, gravity drainage to the catho-
des will continue but at an ever-decreasing rate so that drainage
stops in a short time period.
- When the current is interrupted, the small holes in the cathode are
quickly blocked with corrosion products. Thus the holes must be larger
and current must be applied almost continuously.
- The filtercathodes should not be placed in the center of the reservoir
but in the intermediate zone. One will thus obtain a movement of
water from the zone of fine clay and silt material to the zone of
sandy material and will limit plugging of the holes in the cathode
(and will allow construction of larger holes).
DRAINAGE OP WATER IMPOUNDED IN THE BOWL OP THE MAIN
SEDIMENTATION BASIN
It was deemed infeasible to work on the main sedimentation basin
until the water impounded in the surface bowl had been removed. The
overflow tower originally used had been filled with silt and could not
be used. Therefore a siphon arrangement was employed using rubber
pipe of 120 and 180 mm diameter (fig. 61). The water remaining in a
few depressions after siphoning was pumped over the embankment.
104
-------
FiQ61 TEMPORARY SYPHON ARRANGEMENT FOR GRAV!TY
DRAINAGE OF SURFACE WATER
Vwoter 2 valve. 3-connector with vdv.. * - i"*»rc.d
rubber hose. 5-valve. 6-embankment of tolling, pto.
GRAVITY DRAINAGE FROM THE SEO^ENT BASIN
BWW. WITH HOSE PLACED IN tHT
1-droinoge from well . ' earm «u. '
4-embankment of tailings pile
105
-------
A ditch was cut through the embankment to prevent accumulation of
precipitation and percolation into the tailings. The ditch varied in depth
from several centimeters in the center of the pile where it was linked
to several ditches, to a depth of 3.5 m through the embankment.
The rubber pipe used as a siphon was then buried in the ditch
to serve as a conduit (fig. 62-63). It •was felt that the open ditch could
be subjected to excessive erosion if it were left standing. This affor-
ded control of the run-off, which was all the more important once waters
pumped from the filter - cathodes were also discharged through this
pipe.
106
-------
o
-0
Fig. 63 CONTOUR MAP OF THE MAIN SEDIMENTATION
BASIN BOWL. THE POSITION AFTER DRAINAGE
OF SURFACE WATERS.
explanation :
v. .•' System of surface drainage system and
~\ cross -out through embankment
\
to the river
-------
SECTION 8
INSTALLATION OP ELECTROOSMOTIC DRAINAGE SYSTEM
ON THE MAIN SEDIMENTATION BASIN IN OGORZELEC
DESCRIPTION OP THE DRAINAGE SYSTEM
On the basis of analyses of research results from both the model
tests and the field tests, and from investigations of physical characte-
ristics of sediment, care was taken to install the optimal electro-osmotic
drainage system.
The principal design considerations were the shape of the electric
field, the spacing of the electrodes, and the choice of suitable electri-
cal supply and wiring.
The shape of electric field and the^ spacing of electrodes
The most advantageous configuration for the electrodes, considering
favorable conditions for current propagation is an arrangement where
the distances between the sets of anodes and cathodes are equal in
all directions. It is therefore a configuration consisting of regular, con-
centric geometric shapes.
In the case of the main sedimentation basin, the shape of the pile
and the resulting horizontal distribution of water within the sediment
suggested that two concentric ellipses of electrodes could be used.
Anodes and cathodes were located at regular distances along these
ellipses. The anodes were located along the interior ellipse while the
filter cathodes were located outside in the sandier, intermediate zone.
108
-------
Fig.64 ARRANGEMENT OF ANODES AND CATHODES WITHIfl
THE 80WL OF THE MAIN SEDIMENTATION BASIN
explanation:
21
o cathodes No
•• anodes
m electrical supply system
0 10 20 3O 40 SOm
-------
An additional line of anodes was placed along the axis of the inner
ellipse (fig. 58, 64).
The elipse of cathodes, designed to permit pumping of accumulated
water, were located almost at the demarcation line of silty-clay and
silty-sand tailings. Thus the water would accumulate in areas where its
movement was facilitated.
Electrical supply and connection to anodes and cathodes
The twenty-nine filter-cathodes were connected in two groups of
14 and of 15 wells to permit independent operation of either group.
The anodes (a total of 50) were connected in one group (fig.-64).
Each electrode within a group was connected with single strand
O
copper leads (180 mm sections). The leads were brass welding to
obtain maximum conduction. Each group of electrodes was connected
to the electrical supply system in a similar manner.
The electrical supply system consisted of transformer- and a recti-
fier (fig. 6?) connected as shown on fig. 65. The system also provided
power for a pump used to remove water from the filter cathodes.
The transformer (100 kVA, 380/173/86.5 v) provided after a recti-
fication, a current of 450 A, i.e. or about 15 A per filtercathode during
operation of the entire field of electrodes (29 filtercathodes ).
The rectifier used (PK—09/0.25 type) provides rectification of cur-
rents to 1000 A with voltage of 250 V. The method of a wiring diagram
for the supply system is shown on an assembly drawing (fig. 66).
Electric power was supplied to the system through an electric substa-
tion located on the premises of neighbouring workshop "Inco".
CONSTRUCTION AND INSTALLATION OP ELECTRODES
The anodes consisted of 50 steel electrodes in a shape of pip«
with diameters of either 115 mm or 298 mm. The anodes were reinfor-
ced with scrap metal. The anodes were emplaced to depths of 10 m
110
-------
1.
OG 3x95+35
OG 3x95+35 .
'
OG 3x95 + 35
'
1x00180 _
1x00180 ^
•J
r5
BLOCK DAGRAM CF THE ELECTRICAL SUPPLY SYSTEM
1 - to rr;a;n dirrtriD'jtion board
2 - connecting box
3- h-ansfcrnner 3CO/175/100
A-rc-.^-ir P-'-09/0,25
5 ~ic eledrofiltorj ( a!->-.iss end cathodes )
-------
to
100A |SC400—-/
Fig.66 TYPICAL ELECTRICAL ASSEMBLY DRAWING OF FEEDING SYSTEM CONNECTIONS OF POWER SUPPLY SYSTEM.
1- rectifier , 2-to eiectrofilter ,3-signalling diode fuse burnout ,4-Cu-rod 100 mm2, 5-transformer 380/175/100V
6-swilchboard 380/220V
-------
measured from the terrain surface. The anodes had no perforations.
The cathodes consisted of 29 steel pipes with inner diameters of
298 mm. These were also emplaced to depths of about 10 m.
Every cathode also served a filtering well which collected water
freed from the sediment by electroosmosis draining. Therefore the
cathodes were perforated along the entire length. The holes were of
rectangular slits with dimensions of 5 x 50 mm (fig. 68) and were
spaced in such a way that within one meter of pipe there were 10
holes. The total surface area of the filter cathodes was about 340 m .
The surface area on the anodes was about the same. Drilling opera-
tions for emplacement of the electrodes were conducted from February
to May of 1976. Drilling was started during the winter season since
the surface was frozen and access was facilitated.
A light weight steel tripod system was used to drive the electrodes
into the soft, plastic tailings, (fig. 69). In the course of driving the
electrodes, the phenomenon thixotropic fluidization of the sediment was
observed.
Tailing was removed from the electrodes using a core drill. Sedi-
ment removal began after all electrodes had been installed so as to
avoid having to redrill the slotted cathodes. A few wells were emptied
with a combined method using a core drill and a bailer after adding
water to the tailings in the well.
Prom four of the filter-cathodes and from one of anodes (the central
well) the samples of sediment were taken to a depth of 9 m.
The filtercathodes were driven to a maximum depth of 10 m and the
average depth of emplacement was 9 m. With time the tailings entered
the cathodes through the slits and tailings flowed into the open end of
the pipe such that the effective depth of the cathode was reduced.
The table no. 20 represents effective depths of filtercathodes on 16 Sept.,
1976, (two months after commenced electroosmotic drainage) and on
15 Feb., 1977, after partial cleaning of filtercathodes of intruding tailings.
113
-------
Pig. 67. Complex of feeding the draining installation.
Pig. 66. Piltration holes in filter - cathodes.
114
-------
Pig. 69. Sinking filter—cathodes into sediment with the
aid of vibrohammer.
•-.
Pig. 70. Removal of sediment from filtercathodes.
115
-------
Table 20
Changes in effective depths inside filtercathodes during
electroosmotic draining
!
No. of
'. filter
cathode
1
1
2
3
4
5
6
7a
8a
9a
lOa
lla
12a
13
14
15
16
17
18
19
20
21
22
23
24
25
Distance of top
edge from sur-
face
(protruding)
m
2
1.05
0.82
0.66
0.66
1.15
0.68
0.64
0.56
0.53
0.90
0.68
0.61
0.49
0.63
0.57
0.55
0.63
0.54
O.55
0.57
0.60
0.42
0.57
0.57
0.68
Distance from the bottom to the
surface
m
i
Sept. 16,1976 Peb. 15, 1977
3 i 4
3.49
2.42
2.27
2.54
2.77
3.56
4.46
4.48
4.77
3.56
4.19
5.03
3.87
3.66
3.12
3.73
3.71
3,21
3.37
2.90
3.18
2.13
2.63
2.54
4.85
4.18
3.64
4.74
3.95
4.82
5.91
6.19
6.27
4.45
5.52
5.79
5.17
4.12
5.03
5.35
5.17
4.76
4.75
4.03
4.10
2.38
3.63
3.43
2.78 1 3.42
116
-------
Continuation table 20
1
26
27
j 28a
29
2
0.85
1.24
0.56
0.68
Total:
3
2.91
3.11
4.62
3.27
98.28
1
4
3.75
4.16
6.24
6,52
136.32
117
-------
SECTION 9
DRAINAGE PRODUCED BY ELECTROOSMOTIC SYSTEM
ON THE MAIN SEDIMENTATION BASIN IN OGORZELEC
GENERAL REMARKS
The principal investigations of electro osmotic drainage of postflo-
atation tailings were performed under field conditions on the main sedi-
mentation basin in Ogorzelec, from 21 July 1976 to 31 August 1977.
This work was carried out using the installation described in the pre-
vious chapter, and consisted of a number of tests conducted under
differing rates of electric supply, periods of current flow and breaks
in supply, and also weather conditions obtaining during the tests.
The specific test conditions used to investigate the effects of
varying the electric field were:
- A continuous power supply to all electrodes
— A continuous supply to all electrodes with periodic interruptions in
current for short times
- A supply to all electrodes with long interruptions in current
- A supply of short duration to all electrodes with long interruptions
in current
- A continuous power supply to one half of the cathodes
- An alternating supply to each half of the field
- An intermittent supply to all electrodes with day-long periods of
supply and interruptions in supply.
The normal intensity of the current supplied to the electrodes was
usually 400 A to all electrodes and 200 A to half the cathodes. The
118
-------
Pig. 71. Spacing of electrodes on main sedimentation basin,
showing the condition of the surface during the
initial phase of experiment.
Pig. 72. The sedimentation basin surface after a year of
drainage.
119
-------
weather, mainly precipitations, had considerable influence on the effec-
tiveness of electroosmosis despite the existence of the surface drainage
network. Rain water did accumulate within the bowl of the sedimentation
basin. This happened during heavy rains and during sudden spring
thaws. During such periods the current was switched-off to forestall a
forced flow of rain water into the sediments toward the cathodes.
Maintenance of the surface drainage network was difficult owing to con-
tinuing subsidence of the sedimentation basin bowl, and also to infiltra-
tion of tailings into the ditches and into the rubber hose which conve-
yed water beyond the embankment. This impediment to surface drainage
caused direct inflow of water into the filtercathodes, and distorted the
measurements of discharges resulting from electroosmosis. However,
such blockages occurred only sporadically. During the whole research
period the accumulating water in filtercathodes was being removed with
the help of plunger pumps, type NDMU 1 /2 inch, with an output to
100 1/min. and maximum water rise head 9 m. The pumping operations
were performed at irregular time intervals (from few to several days)
usually after a complete filling of wells with water.
Additionally, the wells were always emptied regardless of water
amounts before the start of new test.
The rate of water inflow into wells was determined by way of me-
asurements of the water table level in reference to the top edge of
filtercathodes. These measurements were performed in all wells at re-
gular time intervals (every two days) with an accuracy to 1 cm. Used
for this purpose was measuring tape ending in so called hydrological
whistle. The position of water table level was also measured before
and after each pumping operation.
On the basis of these measurements were determined the total
water discharges and average discharges for typical well during the
time period of each test duration, also total volumes of pumped out
water were measured.
The changes in the drainage from the main sedimentation basin
with time during the electroosmotic drainage process are shown in
120
-------
figures 73-80. These diagrams show water inflow rates (in the form
of well yields) to the filtercathodes of both the entire arrangement
(curve "A") and the deepest weEs (curve «B"). The diagrams also
show variations in the pov/er supplied to the drainage system and
indicate the dates of water pumping from the filtercathodes.
Yield of wells are making the resultant increases in water quantity
obtained in wells in the effect of water inflow induced by electroosmo-
tic phenomenon, and water losses caused by infiltration into permeable
layers of sediment. A supplementary role are fulfilling the plotted at
the same axis of time the diagrams of daily sums of atmospheric pre-
cipitation and of the efficiency of group of deepest wells.
Through efficiency of deepest wells one understands the percen-
tage ratio of filtercathodes yields in this group to the yields of all
other filtercathodes.
As a norm of efficiency of filtercathodes is taken the percentage
ratio of total yields of 7 deepest wells to the total of effective depths
of the whole battery of filtercathodes.
DISCUSSION OP THE TESTS
The tests started with observations of gravitational inflow of water
to filtercathodes before applying current. After one week quantities
(about 10-15 liters) of strongly polluted water also containing sediment
were found. The inflow of pulp through the filtration holes in the cat-
nodes and the entrance of tailings through the bottom opening of the
cathodes was also observed. As noted earlier, this inflow resulted in
a reduction in the efficiency of the cathodes.
Similar inflow of tailings occurred into the anodes where the level
of tailings rose (within the pipe) above the surface elevation on the
tailings pond.
On Aug. 21, 1976 the water accumulated in filtercathodes was
pumped out and electric power applied thereby starting the cycle of
tests of electroosmotic draining of the sedimentation basin.
121
-------
In the following discussion of tests is considered the time of tests
duration, periods and conditions of current supply, average well yields
and total water yields in all wells. Average well output is the mean
rate of water inflow during test time in a single well. Total water yield
is the quantity of water which flows into all wells during the whole
period of the test duration.
Test no. 1 is summarized in the following table.
Summary of test no. 1
Continuous supply to all cathodes with 2-3 day interruptions
in current supply
Period
of te<^t
WJ. l-CTO {,
duration
Jul. 21 -
Sep. 20
1976
(fig, 73)
Time
of test
durations,
days
1 446,7
Supply
periods,
days
total
1064,0
Breaks
in supply
days
total
382,7
Current
intersity,
A
400
Average
well
yield
during
test
1/h
12,4
Total
water
dischar-
ges
1
17 939
Changes in discharge from the filtercathodes with time are presen-
ted in fig. 73. The diagram shows that each time current is reapplied
the yield of the wells increases. In succeeding days of electroosmosis
the yields decrease in an irregular manner. During the periods of power
interruption the well yields decreased quite rapidly.
Pumping of the wells enhanced the drainage of water into the
cathodes considerably since the water accumulated around the cathodes
would then drain under the higher potentiometric head conditions.
The third factor in addition to the electric supply and well pumping
procedures that determine the output of a well is precipitation. The
extent to which this factor affects the water inflow into the filtercathodes
depends on the efficiency of the surface drainage system. Small amo-
unts of precipitation occurring in short periods of time does not alter
122
-------
the well discharges. However, precipitation with great intensity and long
duration does. One can observe on fig. 73 sudden increases in filter-
cathode outputs caused by in filtration to the wells after heavy rains.
The peak discharges are displaced in time due to the retention capa-
bility of the tailings.
The efficiency of the group of deepest wells, during this test was
highest during the periods of rains and during interruptions in supply.
This leads to the conclusion that the effective depth of the filtercatho-
des has a bearing on the capability of receiving rain water. This
increased efficiency may be related to the increased potentiometric
head created by pumping from deeper in the tailings pile.
The results of test la are summarized in the following table:
Summary of test la
Continuous supply of all electrodes with 2-3 days 'breaks
in electric supply
The period
of test
duration
Time
of test
dura-
tion
days
Periods
of supply
days
total
Breaks
supply
days
total
Current
intensity
A
Average
well
out put
1/h
Total
water
yields
1
Dec. 27,76
— Jan. 6,
1977
(fig. 75)
264,7
168,0
96,7
400
9,0
2 382
i
Changes in the yields of the filtercathodes with time for test la are
presented in fig. 75.
The results of test Ib are presented in the following table.
123
-------
Summary of test no. Ib
A supply to all electrodes with 2-3 day interruptions
current supply
The period
of tests
duration
Jan. 28 -
Feb. 10,
1977
(fig. 76)
Time
of test
dura-
tion
days
311,6
Periods
of supply
days
total
205,0
Breaks
in supply
days
total
106,6
Current
intensity
A
700
Average
well
out put
1/h
18,5
Total
water
yields
1
5 764
The changes in yields from the filtercathodes during test Ib are shown
in fig. 76.
As opposed to previous tests a much higher intensity of electric
current (700 A) was applied during test Ib. This higher current gre-
atly increased the water yields. Thirteen hours after current was
applied the well yield was measured at 60.1 1/h. Figure 76 shows that
precipitation was measured at the time. This yield was followed for the
next 4 days by a reduction in the yield to 10 1/h. Further testing re-
sulted in an average yield of about 13 1/h. During the entire period
of the test, the rate of water inflow into the cathodes averaged 18.5 1/h.
The efficiency of the group of deepest wells was generally small, howe-
ver it increased considerably after disconnection of current and with
the occurrence of rain. The period of test Ib was characterized with
the occurrence of only a small rain, which permits a. more accurate
assessment of the effect of electroosmosis on drainage. After a lapse
of one full day from the time the wells were pumped dry, the electric
supply was again applied to all electrodes. This produced a rapid in-
crease in water yields induced by both the reapplication of current and
the increase in flow caused by pumping the filtercathodes. During a
period of 2 days the yield of electrodes rose from 3.2 1/h to 17 1/h.
Then, however, the yields fell by almost 50 percent. Similarly to that
124
-------
observed in the previously described test, the break in supply clearly
produced a decrease in water yields. The relative efficiency of the
group of deepest wells increased.
The results of test Ic are summarized in the following table.
Summary of test no. Ic
A supply to all electrodes, with periodic inter -
ruptions in supply of current
The period
of test
duration
May 1 -
May 19,1977
(fig. 79)
Time
of test
duration
days
456,4
Periods
of supply
days
total
333,0
Breaks
in supply
days
total
123,4
Current
intensity
A
400
Average
well
out put
1/h
9,4
Total
water
yields
1
4 290 ;
Changes in water yields with time for test Ic are diagramed on fig. 79.
In this test the periods of current supply are characterized by an in-
crease in water discharges, and the periods of no supply by a slight
decrease. The long term average yield (9.4 1/h) was positively affec-
ted by appreciable rain that occurred during the tests. The efficiency
of the group of deepest wells was markedly below that observed for
other tests.
The results of test Id are summarized in the following table.
Summary of test no. Id
A supply to all electrodes with short interruptions
in current supply
The period
of test
duration
May 30 -
Jul. 29,1977
(fig.80)
Time
of test
duration
days
1462.2
Periods
of supply
days
total
1248.0
Breaks
in supply
days
total
214.2
Current
intensity
A
400
Average
well
out put
1/h
12.5
Total
water
yields
1
18 277
125
-------
The diagram of changes in filtercathode yields for test Id is fig. 80.
The period of test id was characterized by frequent and appreciable
rain. The effect of these rains is reflected clearly in subsequent incre-
ases in water yields of filtercathodes and in a relatively high average
output of wells of 12.5 1/h.
During the entire test the efficiency of the deepest wells was below
normal. The reasons for this are likely related to the times of rain
being different than the times of pumping. Test Id was interrupted du-
ring days 30 July - 5 Aug. 1977, when torrential rains fell in the area.
The rains caused flooding of the sedimentation basin bowl. After the
water was removed and the wells pumped out, more rain occurred on
5 July 1977 and the test was discontinued.
The general results of test no. 2 are summarized in the following
table.
Summary of test no. 2
Current supply to all electrodes with short
interruptions in supply (3-5 hours)
The period
of tf^ctf
duration
Sept. 20 -
Oct. 18.76
(fig. 73)
Time
of test
duration
days
673.2
Periods
of supply
days
total
631.5
Breaks
in supply
days
total
41.7
Current
intensity
A
400
Average
well
out put
1/h
10.7
Total
water
yields
1
7 203
Changes in well yield with time for test no. 2 are diagramed in fig. 73.
The initial phases of test no. 2 indicated a temporary increase in water
yields. The water yields during periods of electrical supply were similar
to those of test no. 1. The short duration (few hours) interruptions in
current supply produced increases in filtercathode water yields upon
resumption of current. During the period 13-14 Oct. 1976 a negative
yield of the wells, was noted i.e., the water was moving into the sedi-
ment despite the fact that the electrical supply was connected to the
126
-------
whole field. This phenomenon appeared most clearly in the group of
deepest wells. In fact, these deep wells had a low efficiency during the
entire test. Intensive rains started on 18 October and lasted to 25 Octo-
ber, 1976. The test (no. 2) was therefore terminated.
The results of test no. 2a are summarized below.
Summary of test no. 2a
Current supply to all electrodes with short
interruptions in supply
Period of
test
duration
Jan. 6 —
Jan. 26.1977
(fig. 75)
Time of
test
duration
days
455.3
Supply
periods
days
total
422.0
Breaks
in supply
days
total
33.3
Current
intensity
A
400
Average
well
yield
1/h
9.1
Total
water
yields
1
4 143
Changes in water yields with time during test no. 2a are presented in
fig. 75.
The trends of water yields during test no. 2a were similar to that
occurring during test no. 1. A few days after connecting the current
supply an increase in the water discharge was observed. In subsequent
days a small decrease occurred. Pumping out of the wells increased
the well yields. The 3 to 4 hour interruptions in supply did not mater-
ially influence water yields. The test was characterized by no precipi-
tation and thus the well yields were not affected by inflow of surface
water. The group of deepest wells produced water at half the rate of
the entire system.
The results of test no. 3 are summarized below.
127
-------
Summary of test no. 3
Continuous current supply to all electrodes
with long interruptions in supply (4 to 6 days)
The test
duration
period
Oct. 25 -
Nov. 12.76
(fig. 74)
Test
duration
time
days
458.0
Supply
periods
days
total
275.0
Breaks
in days
total
183.0
Current
intensity
A
400
Average
well
out put
1/h
9.2
Total
water
yields
1
4 214
Piltercathode water yield changes with time for test no. 3 are presen-
ted in fig. 74.
During the 11.4 days of current supply during test no. 3, changes
in well output were similar to those observed for other test. Toward
the end of the supply period, rain occurred and an appreciable incre-
ase in water inflow was measured. After disconnecting the supply and
after a similar precipitation, even a much smaller and temporary incre-
ase in well output was measured.
The average output of filtercathodes was positively influenced by
the rain.
The results of test no. 3a are summarized below.
Summary of test no. 3a
Continuous current supply to all electrodes
with longer periods of interruptions in supply
Test
duration
period
Feb. 10 -
Feb. 20.
1977 ,
(fig.no.76)
Test
duration
time
days
263.9
Supply
periods
days
total
135.0
Breaks
in supply
days
total
128.9
Current
intensity
A
400
Average
well
output
1/h
16.6
Total
water
yields
1
4.380
128
-------
The changes in water yields from the filtercathodes during test no. 3a
are shown in fig. 76.
The initial application of current was followed by a five-day inter-
ruption in supply, during which an appreciable, although short, increase
in the rate of water inflow to filtercathodes took place. During a period
of the test (12 to 14 Feb. 197?) the filtercathodes were cleaned of
tailings which had entered through the perforations and bottom of the
wells. This had the effect of deepening the wells and changed the per-
centage ratio of the effective volume of the deep wells (nos. 7,8,9,10,
11,12 and 28) to the volume of all wells (B/A). The ratio was 29.6
percent and considered to represent the normal efficiency of the group
of deepest wells. The deepening of all wells caused the efficiency of
the group of deepest wells in subsequent test periods, to undergo a
downrating, despite still existing appreciable differences in depths. The
period of supply in this test proceeded typically.
The results of test no. 4 are summarized below.
Summary of test no.4
Electric supply with short periods of supply
and long interruptions in this supply to well
electrodes
LjQ Y*\ (~V/~J
f-\f •f-ClC'4-
duration
Nov. 12 -
Dec. 27.76
(fig. 74)
Test
duration
time
days
1 079.4
Supply
periods
days
total
130.0
Breaks
in supply
days
total
949.4
Current
intensity
A
400
Average
•well
yield
1/h
9.0
Total
water
yields
1
9 715
The changes in water yields for test no. 4 are illustrated in fig. 74.
Very long interruptions in the electric supply were necessitated by in-
tensive and continuing rains. During the entire test period there were
only ten days without precipitation. Hence an appreciable amount of the
filtercathode yields can be attributed to infiltration of rain water.
129
-------
Figure 74 shows clearly an increase in water inflow after pumping.
Obiously this was caused by the increased potentiometric head diffe-
rence between the water in the well and that in the tailings. Experience
shows that the relatively high efficiency of the deep wells during two
time periods is related to the infiltration of rainwater.
The results of test no. 5 are presented below.
Summary of test no. 5
Continuous electric supply to one half of the cathode
field
The period
of test
duration
Feb. 20 -
Feb. 28
1977
(Pig. 76)
Test
duration
time
days
216.8
Supply
periods
days
total
130.0
Breaks
in
days
total
86.8
Current
intensity
A
200
Average
well
1/h
14.0
Total
water
1
3 035
The diagram of water discharge versus time, is provided in fig. 76.
Electric current was applied to half of the cathodes (nos. 2-15) and
all anodes. At the time the current was switched from the entire field
of cathodes to one half of them, (with a simultaneous reduction in
current intensity from 400 to 200 A) the water yields began to slowly
decrease. The occurrence of appreciable rainfalls by the end of the
test period caused a sudden increase in water discharge, even when
the electric supply was interrupted. The efficiency of the deepest wells,
despite the fact that six of them remained activated, was very low.
This efficiency did increase considerably during the period of rain.
The average yield of wells during the entire test period was rela-
tively high (14.0 1/h).
130
-------
The results of test no. 5a are summarized below.
Summary of test no. 5a
Continuous supply to one half of the cathode field
Test
duration
period
Mar. 12 -
M±97726'
(Pig. 77)
Test
duration
time
days
360.1
Supply
periods
days
245.5
Breaks
in
supply
114.6
Current
intensity
200
Average
well
out put
1/h
8.2
Total j
water
yields
1
2.953
The water yields of cathodes during test no. 5a are shown in fig. 77.
The period of this test was marked by very little precipitation. The
same group of cathodes used in test no. 5 was connected.
After initial application of current and emptying the filtercathodes,
a sudden increase in the water discharges occurred. The water yields
remained constant for 2 days. During the next 2 days a rapid decline
in the discharge rate was observed. The yields continued to decline
at a slow rate through to the end of the test. A full day break in the
current supply produced a faster decline in yield. Resumption of the
electric supply for a period of one day reduced the rate of decrease
slightly.
The efficiency of the deepest filtercathodes stayed below what was
considered to be the normal level.
The results of test no. 6, consisting of observations made during.
a prolonged period of no current application, are summarized below.
131
-------
Summary of test no. 6
Prolonged time period without electric supply to
any electrodes
Test
duration
period
Feb. 28 -
Mar. 12.
1977
(fig. 77)
Test
duration
time
days
315.0
Periods
of supply
days
total
_
Breaks
in supply
days
total
315.0
Current
intensity
A
_
Average
well
out put
1/h
2.2
Total
water
yields
1
693
After a long period of experimenting with various electroosmosis
procedures, a 13 day period of no current application was used to
indicate whether there were any residual impacts on water inflow to
the filtercathodes. The results of water yield measurements made during
this test (no. 6) are shown in fig. 77.
The maximum well output (19 1/h), was observed after one day and
after rain. During intervening periods of no rain, negative discharge
rates (inflow to sediment) were observed twice during the test. This
observation prompted a hypothesis that after a long period of electro-
osmosis and drainage, the structure of the sediment changes to permit
gravity drainage to some degree. The efficiency of deepest wells was
not determined due to their "negative" yields (i.e., infiltration into the
tailings). It was established that infiltration of water into tailings from
this group of deep wells was smaller than from the other shallow wells.
Two additional teste to determine how the tailings drained during
periods of no current supply were conducted. The results of tests nos.
6a and 6b are summarized below.
132
-------
Summary of test no. 6a
Prolonged time period without electric supply
Test
duration
period
Apr. 8 -
Apr. 18.
1977
(Pig.no.78)
Test
duration
time
days
263.5
Supply
Periods
days
total
—
Breaks
in supply
days
total
263.5
Current
intensity
A
_
Average
well
output
1/h
21.1
Total
water
yields
1
5 560
During the period of test 6a considerable rainfall occurred causing an
appreciable infiltration of rainwater to the wells. Accumulation of rain-
water in the basin occured to such a large degree that the level rea-
ched the top of some of the cathodes. This water flowed directly into
the wells.
The results of test no. 6a are summarized below.
Summary of test no. 6b
Time period without electric supply
The
duration
period
May 19 -
May 30.77
(Pig.no.79 )
Test
duration
time
days
215.6
Supply
periods
total
days
Breaks
in supply
days
total
215.6
Current
intensity
A
Average
well
out put
1/h
14.7
Total
water
yields
1
3 169
The high water yield resulted from the high amount of precipitation
that occurred at the beginning of the test. During one day, 72 mm of
rain flooded the sedimentaion basin bowl and caused a direct inflow of
rain water to filtercathodes just as it had during test 6a.
133
-------
In subsequent days the well yields decreased and became negative
i.e., the water flowed into the tailings.
The results of test no. 7 are summarized in the following table.
Summary of test no. 7
Alternated supply of current to each half of the
cathode
Test
duration
period
Mar. 26 -
Apr. 8. 77
(Flg.no.78)
Test
duration
time
days
312.0
Supply
periods
days
312.0
Breaks
in supply
days
_
Current
intensity
A
200
Average
well
out put
1/h
10.7
Total
water
yields
1
3 338
The changes in water yields with time during test no. 7 are illustrated
in fig. 78. The two sets of cathodes were alternatively supplied with
current for this test. The first group was composed of cathodes nos.
2-15, and the second group of cathodes nos. 1,16 - 29. The current
supply was switched every 2 to 4 days.
The average well output of the whole field for test no. 7 was
about equal to that measured for other tests. Increases in yields were
produced each time the current was applied to the second group of
cathodes, but a decrease in yield occurred in the first group. This
was likely caused by the use of the first group of cathodes (only) in
tests nos. 5 and 5a.
When there was a continuous electric supply it caused inflow
of rainwater and appreciable drainage and increased the resistance
of sediment in the zone between anodes and cathodes nos. 2-15 (the
first group ).
134
-------
The results of test no. 8 are summarized in the following table.
Summary of test no. 8
Intermittent electric supply to all electrodes. Pull day
periods of supply and interruptions.
Test
duration
period
Apr. 19 -
May 1, 77
(Pig.no.78)
Test
duration
time
days
335.9
Supply
periods
days
total
178.0
Breaks
in supply
days
total
157.9
Current
intensity
A
400
Average Total
•well -water
output yields
1/h 1
13.6 4 568
The variations in water yields with time are shown in fig. 78.
The test was characterized by a high average well output (13.6 1/h).
The yields were affected by inflow of rain water, but the greatest
influence on water yields in filtercathodes appears to have been the
method of applying the electrical supply. When the current was applied,
the yields increased.
The efficiency of the deepest cathodes was below the expected
level throughout most of the test.
INTERPRETATION OP TEST RESULTS
Comparisons of the efficiency of the electroosmosis tests are
complicated by the influence of precipitation. Despite the surface
draining system precipitation caused varying amounts of water inflow
into the tailings. Attempts were made to repeat tests in different weat-
her conditions to make allowance for the precipitation factor in consi-
deration of test results.
As another measure of efficiency the consumption of electric power
per unit of drained water was used. Values of electric power consumed
during the various tests, expressed in kilowatthours, are given in
135
-------
EXPLANATION FOR FIGS.73-80
I. DIAGRAM OF CHANGES IN WATER INFLOW RATE TO FILTERCATHODE5
~ WITH TIME
-y- overage velocity of water Inflow to f«tercalhod«t, efficiency" of flltercathodes I/h )
t Hme (doyj)
changes in ..efficiency" of the whole complex of filtercatnodes and overage
efficiency of filtercathodes during test
_ changes in.efficiency" of the group of deepest filtercathodes lnos.7-12.28)
' N.
K continuous electric supply to all electrodes . current intensity 400 A
and interruption in electric supply
electric supply to all anodes and to first group of filfercothodeslnos. 2-15) intensity 200 A
electric supply tool! anodes and to second group ot filteraothodes(nos.1.16-29) intensity 200A
I. DIAGRAM OF TOTAL DAILY OF PRECIPITATION.
P daily total of precipitation (mm)
jn_. DIAGRAM OF EFFICIENCY OF GROUP OF DEEPEST FILTERCATHOOES (NOS.7-12 .28)
JJ_ efficiency of the group deepest filtercathodes -calculated as the water yield
A of (he deepest cathodes (8) divided by the water yield of all cathodes (A)
„ i standard of efficiency - percentage ratio of total depth of filtercathodes as
' ° driven for group of deepest wells compared ID the entire complex of filtercathodes
316°/ JK standard of efficiency - calculated as the percentage ratio ot effective
and 296% filtationteffective depth ot depth of cleaning wells ot sediment) of the
group of deepest wells and of Ihe whole flltercathode complex
change of the II standard of efficiency on the date when Ihe filtercathodes
were cleaned of Idlings that had entered the cathodes
136
-------
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R9.73 CHANOES IN WATER YIELDS AND EFFICIENCIES DURING TESTS 1 AND 2. MAIN SEDIMENTATION BASIN IN OGORZELEC. 21JUL - JS OCT 76
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CURRENT APPLIED
Figure 73 - Continuation
138
-------
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Rg.74. CHAN6ES IN WftTER YIELDS AND EFFICIENCIES DURING TESTS 3 AND*. MAIN SEDIMENTATION BASIN 25 OCT - 26 DEC 76.
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CURRENT APPLIED
Fig.TS CHANCES IN WATER YIELDS AND EFFICIENCIES DURING TESTS lo
AND Zo.MAIN SEDIMENTATION BASIN 27 DEC-25 JAN 77
140
-------
CURRENT APPLIED
Ha* CHANGES IN WATER YIELDS AND EFFICIENCIES DURING TESTS 1b,3a ,
AND 5. MAIN SEDIMENTATION BASIN 28JAN - 38 FEB 77.
141
-------
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CURRENT APPLIED
CHANGES N WATER YIELDS AND EFFICIENOES DURING TESTS 6
AND So. MAIN SEDIMENTATION BASIN !FEB- 26MAR 77.
142
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Fig 78 CHANGES IN WATER YIELDS AND EFFICIENCIES DURING TESTS 7
AND 60 . MAIN SEDIMENTATION BASIN 26 MAR - 18 APR 77.
143
-------
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CURRENT APPLIED
Fig. 79 CHANGES- IN WATER YIELDS AND EFFICIENCIES DURING TESTS 8.1c AND 6b. MAIN
SEDIMENTATION BASIN 18 APR - 30 MAJ 77.
144
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Fig. 80 CHANGES W WATER YIELDS AND EFFICIENCO DURING TEST W. MAIN SEDIMENTATION BASIN 30 May-4AUO 77.
-------
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CURRENT APPLIED
Figure 80 - Continuation
146
-------
table 21. This table also contains a listing of the total water dischar-
ges, along with the conditions time, and amount of electric energy
applied during the individual tests.
Table no. 21
Summary of results of electroosmotic drainage tests
performed on the main sedimentation basin in Ogorzelec
Test
designa-
tion
1
1A
IB
1C
ID
2
2A
3
3A
4
5
5A
7
8
Total
water
output
1
17.939
2.382
5.764
4.290
18.277
7.203
4.143
4.214
4.380
9.715
3.035
2.953
3.338
4.568
Average
current
A
406
400
700
400
400
400
400
400
400
400
200
200
200
400
Average
voltage
V
86.5
86.5
173
86.5
86.5
86.5
86.5
86.5
86.5
86.5
86.5
86.5
86.5
86.5
Total
time of
electric
supply
h
1064
168
205
333
1248
631.5
422
275
135
130
130
245.5
312
178
Amount
electrical
energy
consumed
kWh
37.367
5.813
24.826
11.522
43.181
21.850
14.601
9.515
4.671
4.473
2.237
4.247
5.368
6.159
Electrical
energy
used per
liter of
water
removed
kWh/1
2.08
2.44
4.30
2.68
2.36
3.03
3.52
2.25
1.0 6X
0.46X
0.73X
1.43
1.61
1.34
x - denotes ratios noticeably affected by inflow of precipitation
When comparing the electrical energy used for the various tests,
the results of tests no. 3A, 4 and 5 should be omitted due to the
effect of inflow of precipitation which lowered the apparent energy
requirements.
147
-------
Of the remaining tests, the most efficient use of electricity appeared
to have been during tests 8 (l.34 kWh/l), 5A (l.43 kWh/l), and 7
(1.61 kWh/l). These tests were conducted using the following electri-
cal supply methods:
- test 8 intermittent supply to all electrodes (400 A, 86.5 V) alternating
full day periods of current application and interruption
- test 5a continuous supply to one half of the cathodes (200 A,
86.5 V)
- test 7 alternating supply to each half of the field (200 A, 86.5 V).
The electric energy consumption during the other tests usually
significantly exceeds 2 kWh/l.
The highest value of this indicator (4.30 kWh/l) and thus the
lowest efficiency occurred for test no. 1 B, when all cathodes were
employed with 2 to 3 day interruptions in supply of a high current
intensity of 700 A and a voltage of -173 V.
148
-------
SECTION 10
EFFECTS OP ELECTROOSMOTIC DRAINING OP MAIN
SEDIMENTATION BASIN
CHANGES IN ELEVATION OP THE SEDIMENTATION BASIN SURFACE
The objective and scope of measurements of vertical displacements
of the sedimentation basin bowl.
It was assumed that an effect of drying would be the compaction
and vertical displacement of the surface of the tailings. Thus the
elevations of the bowl area were measured before and after removing
water.
The measurements performed with tachymetric method were based
on a polygon network in the form of an independent, closed traverse.
This network was tied to the existing national levelling net. The me-
asurements were used to prepare contour maps for working purposes.
Reference line
For the purposes of periodic observations of any vertical displa-
cements of the main sedimentation basin bowl a network of measure-
ment points was established at the locations shown in fig. 81. A grid
system of 10 m x 10 m was used and wooden piles 1 m long and 6
to 10 cm in diameter were driven at the grid intersections. The grid
locations were identified using the alphanumeric (designations shown
in figure 81.
149
-------
(Jl
o
Fig 81 SURFACE ELEVATION GRID SYSTEM USED TO
MEASURE COMPACTION OF MAIN SEDIMENTATION
BASIN .
explanation:
-^ — limit of surface water pool prior to draining
a f s. 1 s- 17 designations of measured points lines
T notactive over flaw tower
-------
During the initial measurements on 6 Jun. 1975 only 133 of the
total 189 grid intersection points were out of the surface water pool.
This initial limit of surface water is denoted on the drawing with a
dashed line. Only after the surface water was drained could the re-
maining 56 points be measured.
In order to determine the absolute changes in elevation, three bench
marks A, B and C were established on walls of buildings located out-
side the zone of the tailings pile. The position of these buildings is
shown on fig. 2.
Method of measurement
The elevations of the network of survey points (fig. 81) were
measured using survey instruments (Koni 007 - Carl Zeiss). Measure-
ments were made during the period from June of 1975 to September
1977. The first measurement was made on 6 Jun.-1975, and six mea-
surements were made subsequently. The measurements were usually
conducted from five instrument locations. The network was always
closed to ~ 5 mm or less. Observations were started and completed
at location pt 13 d, the height of which was determined each time by
reference to the off-site bench marks.
During the first measurements prior to drainage, the points under
the water surface were levelled with the use of a levelling staff loca-
ted equipped with a special stand to prevent excessive sinking of the
staff. The accuracy of these readings made with respect to the water
table could not be better than - 2 cm. Por this reason the data of the
remaining points of the network were computed in centimeters, for the
first measurement. In subsequent measurements when all points were
clear of standing water the readings on the staff were made in mm.
During the second set of measurements, made on 28 Sep. 75, the
difference in elevations between the post tops measured in the previo-
usly submerged area and the tailings surface was accurately determi-
ned for the first time.
151
-------
The following relationship was used to determine whether the area
was stable:
(h - h') d = 2 m Vn + n
v ' max o T
where:
h and h ' - elevation among inspection bench marks taken from
initial measurement (h) and a later measurement (h');
m
o
- average error of a typical elevation survey (for one
stand of levelling instrument), for which a value of
m = - 0.1 mm was adopted
n - n' - number of stands of levelling instrument in initial (n)
and in later (n ') measurements.
Description of the survey results
During the experiment (June of 1975 to September of 1977),
49 of the elevation piles were destroyed, of which 34 were restored,
some two times.
Vertical displacements for these points were calculated as a sum
of differences between subsequent measurements of the elevation and
the initial measurements, and do not represent continued subsidence.
Differences between actual and initial observation are presented as
a numerical value and the direction of the displacement of the point
is expressed in - mm. The total reductions in elevation through the
experiment are contoured in fig. 82. Three profiles of subsidence
developed from each of the six measurements are presented in fig. 83.
Profiles along line 9-9 (profile A) characterize progressive subsidence
with time across the middle of the tailings pile. The other profiles
(B and C) are located perpendicular to line 9-9 at points "i" and "o"
(see fig. 82 for locations).
The profiles clearly show that the embankments of the tailings
pile remained stable as the bowl subsided.
152
-------
H
01
Fig 82 CONTOUR MAP OF VERTICAL DISPLACEMENTS OF THE
IAIN SEDIMENTATION BASIN BOWL 6 JUN 75 - 8 SEP 77
explanation:
initial rang* of surface water
- -W?-^ tine of equal values of subsidence (300 mm)
* * profile lines
0 TO 3O 30 40 5pm
-------
cdefghij kllmnoprs
Fig, 83 CHARACTERISTIC PROFILES OF VERTICAL
DISPLACEMENTS OF SEDIMENTATION BASIN
BOWL . TAKEN FROM SUCCESSIVE ELEVATION
MEASUREMENTS (SEE FIG. 82 FOR LOCATIONS ).
A-profiles of line 9-9
B -profiles I - I
C - profiles o- o
KAY TO DATES OF MEASUREMENTS
© 6VI.197E
© 281X75
<2> 11.V.76
25.K76.
© 25.lll.77
© 2CIV.77.
® 8IX. 77.
Odoys
114
129
137
181
83
111
Od
t!4
243
380
561
6U
755
154
-------
The irregular character of the profile lines reflects differential
settling throughout the basin. The parallel nature of successive pro-
files suggest that the differential settling was caused by differences
in the permeability of the tailings material. The rate of subsidence
varied by season. Greater displacements were observed in the spring,
smaller in autumn.
Figure 82 uses the difference between the initial elevation and
those measured on 8 Sep. 77 as the basis for the subsidence con-
tours. The contour interval is 50 mm.
Vertical displacements greater than 50 mm occur only on the boun-
dary of the original surface water catchment area (on the drawing this
boundary is marked with dashed line) and attain maximal values in
three areas located in the middle of the tailings basin bowl.
The values of displacements presented are absolute displacements,
since all measurements were tied to stable bench marks, located out-
side the tailings pile area. (Fig. no. 2). Stability of the inspection
bench marks is demonstrated in table 22. Periodic measurements bet-
ween bench marks C and B, B and A, and A and 13d (where the
bench mark 13d is located within the network of points,' indicate that
differences ( d. , column 10, table 22) between the initial measurements
h', and later measurements are within limits of accepted criterion of
stability, d. max, (column 11), i.e. d. < d. max.
These analyses showed that the bench marks A, B and C were
stable for the duration of the surveys. However, in the case of eleva-
tions for A-13d d < d max. for all measurements. Hence this point
I ^ i-
was not stable and the elevation of point 13d was computed for each
measurement. For calculation of the dj max value, mQ = - 0.1 mm was
used. Calculated m values for the measurements (col. 9) were obtai-
ned within limits of 1 0.04 to - 0.08 mm.
155
-------
Test of the stability of external bench marks
Table 22
Obser- Bench
vation mark
day
1
0
Jun. 6,
1975
1
Sep. 28,
1975
2
May 11,
1976
3
Sep.25,
1976
4
Mar. 2 5,
1977
5
May 20,
1977
6
Sep.8,
1977
2
C
B
A
13d
C
B
A
13d
C
B
A
C
B
A
13d
C
B
A
13d
C
A
B
13d
C
A
B
13d
Eleva- Num- Weight
tion ber of 1 h
. , P=~~ avr
stands n
n
3
C-B
B-A
A-13d
C-B
B-A
A-13d
C-B
B-A
A-13d
C-B
B-A
C-B
B-A
A-13d
C-B
B-A
A-13d
C-B
B-A
A-13d
4
1
3
4
1
3
5
1
3
6
1
3
5
1
5
8
1
3
5
1
3
4
5
1
0.33
0.25
1
0.33
0.20
1
0.33
0.17
1
0.33
0.25
1
0.25
0.12
1
0.33
0.20
1
O.33
0.25
6
1542.40
7 6 88.' 65
2754.30
•
1542.36
7688.20
2752.32
1542.70
7689.15
2752.55
1542.60
7689.02
2751.62
1542.35
7689.15
2751.78
1542.40
7689.00
2751.70
1542.30
7689.40
2747.00
d
7
0.1
0.10
0.3O
z:
0.15
0.05
0.05
T.
0.15
0.00
0.30
H
0.10
0.35
0.15
n
0.05
0.30
0.15
C
0.10
0.20
0.10
SI
0.20
0.40
0.50
zr
pdd
8
0.0100
0.0033
0.0225
0.0358
0.0225
0.0008
0.0005
0.0238
0.0225
0.0000
0.0153
0.0378
0.0100
0.0404
0.0056
O.O560
0.0025
0.0225
0.0027
0.0777
0.010O
0.0132
0.0020
0.0252
0.0400
O.O528
O.O625
0.1553
m _+i 1/PcCT d _h ^h
o~~*2 If r i~ i" i
average
error
9 10
+ 0.05 these
~ are H
-0.04
+ 0.04 -O.45
-1.98
+O.30
- 0.05 +0.5O
-1.75
+0.20
± °-°7 -IS
-0.05
O.OO
+ 0.04 +0.35
-2.60
-0.1O
+ 0.11 +0.75
-7.30
d. = - 2m l|n+n
I 0
max
m =0.1
used
11
1
+
+
+
I-HI+I +
1
+
+
+
1+1+1+
0.28
0.49
0.60
0.28
O.49
0.63
0.28
0.49
0.60
0.28
O.57
0.69
O.25
0.49
0.60
0.28
0.49
0.56
01
-------
CHANGES IN TAILINGS MOISTURE CONTENT
In the effect of electroosmotic draining of the main sedimentation
basin, there was observed general fall in the water content in tailings.
In order to determine spatial changes in the humidity of sedimentation
basin, samples for analyses were being collected from a determined
grid of investigated points (fig. 8, 84, 85) essentially to a depth of
3 m. In the course electrodes ' installation, vertical profiles of initial
humidity to a depth of 10 m were made, and after completion of elec-
troosmotic drainage - profiles of final humidity to 4.5 m depth were
made.
In initial distribution of humidity in the near-to-surface layer of
tailings (to 3m) one can observe a clear horizontal zoning (fig. 8).
In external zone (embankment), the humidity assuming values from
18.5 to 31 percent, on average amounted to 23.5 percent.
In internal A zone (between internal slope and the line of initial
reach of water table, extreme values of humidity were shaped from
30 to 35 percent, on average - 32.7 percent. In the enclosed with
line of initial reach of water table (isoline 50 %) internal B zone the
humidity of tailings was more than 5O %.
In further observations of tailings' humidity changes,1 the following
zonal partition was adopted based on the distribution of electrodes
within the bowl of the sedimentation basin:
- external zone (embankment) \5»
- internal zone outside the cathodes (between the line of cathodes
and internal slope of sedimentation basin)
- interelectrode zone (between lines of cathodes and anodes)
- near-anode zone - the center (inside the lines of anodes).
Initial humidity between the lines of cathodes and internal slope amo-
unted on average to 40.6 percent (table 23).
Investigations made after 9 months time from the start of electro-
osmotic draining (in May 1975) showed changes in humidity within
the reach of particular zones.
157
-------
p
Ul
03
Fig84. VWttER CONTENT OF SURFACE LAYER OF TAILINGS AFTER
9 MONTHS OF ELECTROOSMOTIC DRAINING
explanation:
v 11
°,"*-?? designation of measurement points and of sediment water content^
11111! r txisin external slope
_^^r^ basin internal slope t bounder/ between external,
and internal zone A)
3O— line of equal water content.%
cathode's line
anodes line
-------
RgBS WATER CONTENT OF SURFACE LAYER OF TAILINGS AFTER
13 MONTHS OF ELECTROOSMOTIC DRAIN4NG
v ^ exploration:
°i3.22 designation of measurement points ond of sediment water content.%
/ III ll ll basin external slope
basin internal slope t boundary between external and
'
infemol „„, A)
/ [ *°^- |iTO Of equal wat.r content, %
~~~— — _ , cathode's line
------ anodes line
, _
/ III! II [I I
I''''
N
0 m 20 30 *0 50m
-------
In external zone was observed (embankment) a small rise in humi-
dity to average value of 25.3 percent, and its significant differentiation
in particular points (from 15 to 34 percent). In internal zone outside
the cathodes line the average humidity dropped from 40.6 percent to
36.0 percent, by a significant differentiation in extreme values (fig. 84).
In interelectrode and near-anode zones average humidity was determi-
ned respectively as 38.8 percent and 41.6 percent (table 23). Initial
humidity in both zones was more than 50 percent.
After a lapse of further four months, therefore after 13 months of
electroosmotic draining of the sedimentation basin, final analyses of
humidity of samples collected from fixed test points were made. Distri-
bution of average humidities within the sedimentation basin bowl reach
was as follows:
- external zone - 24.4 percent (fall by 0.9 %)
- internal zone outside the cathodes - 34.4 percent (drop by 1.6
percent)
- interelectrode zone - 39.6 percent (increase by 0.89 %
- near anode zone — 42.3 percent (increase by 0.7 %).
Increase in final humidity content in relation to intermediate (after
9 months) humidity ensues largely from the occurrence in preceding
the measurement considerable rains (see diagram of precipitation fig.80).
Average humidity of near-to-surface layer within the limits of the
whole bowl of sedimentation basin (average for all investigated points)
was falling during the tests ' period, assuming values: above the
36.2 percent at the moment of commenced electroosmotic draining,
33.1 percent after 9 months of draining and 31.8 percent after further
four months at time of finished tests (table 23).
Observed in all zones, with the exception of embankment, was
a fall in moisture content, despite the feeding the tailings with rain
water. Main factors enabling the lowering of humidity in the area
outside the line of cathodes was surface drainage and gravitational
flow of water to filtercathodes (wells), while in electric field, apart
from the just mentioned factors - the electroosmotic flow of water to
160
-------
Table 23
Changes in average humidity contents in near-to-surface
layer of sedimentation basin (to 3 m) in the course of
electroosmotic drainage
Period
of electro-
osmotic
drainage
0 months
9 months
13 months
external
f
(emban-
kment )
23.59 %
25.3 %
24.4 %
zone
internal
outside
cathode
line
4O.6 %
36.0 %
34.4 %
inter -
electrode
> 50 %
38.87 %
39.6 %
near
anode
(center)
>50 °
41.6 %
42.3 %
Whole
area of
bowl
> 36.2 %
33.1 %
31.8 %
filtercathodes and the presumably - gravitational discharge to subsoil
unplugged soil pores. The evaporation from surface in conditions of
local climate in Ogorzelec did not have greater significance in the
water balance of tailings.
In accordance with the principle of moisture content distribution
in soil subjected to electroosmotic drainage one could expect best
results of drying in near-to-anode zone and in adjoining it part of
interelectrode zone. However, despite the obtention of a relatively signi-
ficant fall in humidity, it remained highest in that part of electric field.
This can be explained mainly by the morphology of the surface of
sedimentation basin (fig. 63), causing drifts of rain waters towards the
center of the bowl, and their percolation into the tailings through the
network of fissures formed in the course of drying. Thus, under the
partly dry surface of tailings was formed a layer reaching deep to
2.5 - 3.5 m with a higher humidity. This situation is evident in the fig.
86, showing vertical profiles of tailings humidity contents before and
after the electroosmotic drainage.
In the course of "b" curves clearly marks itself the layer with a
raised humidity at depths 0.3 - 3.5 m in the near - anode zone, and
0.7 - 2.5 m in interelectrode zone.
161
-------
NEAR - ANODE AREA
INTERELECTRODE AREA
to
WATER CONTENT ( °/o )
10 20 30 4O SO
Zone of (increased
\ Water I content \ I
\ t • I \ r I \ \ I
\
~7
/b
WATER CONTENT ( °/o )
1O 2O 3O 4O SO
Rg.86 DISTRIBUTION IN DEPTH OF WATER CONTENT IN TAILINGS ON NEAR-ANODE
AREA AND THE INTEREUECTRODE AREA PRIOR TO COMMENCED ELECTRO-
-OSMOTIC DRAINAGE (a) AND AFTER ITS COMPLETION (bJ
-------
The comparison of initial and final profiles of humidity affords a
statement, that electroosmotic drainage brought greatest effects in
deeper layers of tailings, below the reach of atmospheric precipitation
influence. Pall in humidity observed in the thin superficial layer is
the effect of evaporation and of drainage of tailings by the grid of
draining ditches.
CHANGES IN CHEMICAL CHARACTERISTICS OP TAILINGS AND IN
WATER CONTAINED IN THEM
During the application of electric current to promote drainage, per-
manent changes in the chemical compounds forming the tailings took
place. The measured percentage content of particular components con-
tained in sediment not .subjected to electro-osmotic drainage, and of
components in sediment subjected to electroosmosis are shown on table
no. 24.
Table no. 24
Results of chemical analyses of tailings from Ogorzelec
before (l) and after (2) electroosmotic drainage under
laboratory conditions. Major components are shown.
(l ) Prior
to electro-
osmosis
(2) After
electro-
osmosis
Content, in
CaO MgO Cl S
sul-
phide
39.79 0.82 0.00 1.55
42.OO - 0.00 2.96
dry mass, %
Fe2°3 A12°3 Si°2
1.33 3.35 11.59
1.24 3.32 11.44
Inso- Losses
lutale after
sinte-
ring
2.10 34.53
3.96 37.03
Comparisons of the data in table 24 suggest that electroosmotic
draining of sediments has caused a small increase in content of calcium
163
-------
components, an increase in the content of sulphur in the sulphide form,
and an increase of insoluble components. These increases are suffi-
ciently small as to be included within standard analytical errors and
cannot be used to project impacts with great certainty.
More pronounced chemical changes were measured in the compo-
sition of water contained in sediment prior to and after electroosmosis.
Results of chemical analyses of water produced in the process
of electroosmosis under laboratory conditions are provided in table
no. 25.
Denotation no. 1 of table 25 characterizes water obtained in cat-
hodes at the beginning of tests, denotation no. 2 describes water
from cathodes after 3 days of drainage duration, and denotation no. 3
characterizes water in anodes after 10 days of tests.
Table 25
Results of chemical analyses of water collected at various
stages of electroosmotic draining under laboratory conditions
(aluminium electrodes )
Deno-
tation
No.
Catho-
de
(start)
Catho-
de
(+3
\ • ^
days )
anode
(+ 10
days )
Dry
resi-
due
g/1
4.22
5.33
49.15
Total
sus-
pen-
sion
g/1
1.52
0.79
15.05
PH „ +2
r Pe
•4-3
Fe
mg/1
none
10.6 detec-
ted
12 4 none
J. ^c*£
detec-
ted
3.7 - " -
Cl~ Ca+2
mg/1 mg/1
- traces
0.4
976.9 141.0
Mg+2
mg/1
1.6
2.3
**?
mg/1
509.6
105.6
Mn
total
mg/1
none
detec-
ted
none
detec-
ted
0.8 4368.0
Al+3
mg/1
none
detec.
ted
none
detec-
ted
2749.8
164
-------
The chemical composition of water obtained during field tests of elec-
troosmotic drainage of the sedimentation basin in Ogorzelec is presen-
ted in table no. 26.
Analyses were performed on water accumulating in depressions on the
surface of the sedimentation basin before electroosmotic draining (l),
and water taken from filtercathodes nos. 3,4,5 after 9 months of drainage
(2). For comparison sake included as "denotation 3" are values of
permitted concentrations of pollutants for surface waters included in
the third class of purity (the lowest) according to Polish Standards.
Table no. 26
Results of chemical analyses of ground water collected
during various stages of electroosmosis of sedimentation
basin in Ogorzelec
LPrior
to
elec-
troos-
mosis
2. During
electro
Dry
resi-
due
eH
1.19
6.61
osmosis
3, Class
III
stan-
dards
1.20
Total pH
sus-
pen-
sion
eli
O.O3 7.6
1.46 12.1
0.05 6.9
Total Fe+ Cl"" Ca* Mg+ S0~ S~ Mn
hard- _ +3 . . ,
Fe total
ness
G.deg. mg/1 mg/1 mg/1 mg/1 mg/1 mg/1 mg/1
47 0 6.02 342.0 0 705.6 - 0.15
84 - - 591.2 0 0.19 563.7
28.8 20 400 fled'Tn 25° °*1 °*8
terms
of hard-
ness
Comparisons of the "before and after" data of tables 25 and 26 indicate
that the chemistry of the ground water changed significantly during
electroosmosis. Differences in chemical composition are characterized
in a general manner by the hydrogen ion concentration (pH). The
165
-------
water in the tailings in the field prior to drainage was slightly alkaline.
During electroosmosis the water in the cathodes became alkaline while
the water in the anodes was acid.
The water in the cathodes during electroosmosis had a higher cal-
cium content and thus a higher hardness than prior to electroosmosis.
The most important changes in chemical composition measured
during electroosmosis process were:
- a major increase in chlorine (Cl~) for water in the anodes;
, f^
- the increase in calcium cation content (Ca ), in water in the
cathodes noted earlier;
—2
- a major increase in SO anion content in water from the anodes,
but an equally significant decrease in this anion in waters from the
cathodes;
Q
- a large increase in the sulphur (s~ ) content in waters from the
cathodes.
These changes adversely affect the quality of water to be discharged
during the electroosmotic process, a fact that is clearly illustrated
when the standards in table no. 26, and these are only class III stan-
dards, are used for comparison. This poor quality may cause problems
in discharging the waters to the surface water system.
166
-------
SECTION 11
POST-ELECTROOSMOSIS DRYING OP TAILINGS UNDER
ATMOSPHERIC CONDITIONS
The utility of drying tailings under natural, atmospheric conditions de-
pends on the precipitation and natural evaporation rate. The determi-
nation of precipitation in a relatively flat area is not difficult; sufficient
accuracy is provided by standard precipitation measurements. Predic-
tion of the water lost by evaporation is more difficult. The best results
are obtained through direct measurement methods. Lysimeters or soil
evaporimeters are generally used for this purpose.
Soil evaporimeters are particularly useful as the elimination of
under-flowing ground water in evaporimeter largely corresponds to
natural conditions of the sedimentation basin. Por this project special
2
evaporimeters were constructed with exposed surfaces of 250 cm
(similar to those used for Wild's evaporimeters), and with depths of
30 cm (fig. 91-93).
Undisturbed samples of tailings weighing 11 to 13 kg were collec-
ted from the tailings pile. The samples were weighed at about 10-day
intervals, on the 1, 11 and 21 of each month. Precipitation was mea-
sured using a Hellman pluviometer installed at a height of 1 m. The
weights of the samples were determined to - 0.01 kg, which with the
given surface of the instrument corresponds to - 0.4 mm of water
gain or loss.
The amount of water that passed through and out of the sample was
measured to - 2.5 ml (which corresponds to - 0.1 mm).
167
-------
Fig.87 PLAN FOR DRYING THE FLOTATION
SEDIMENTS WITH UTILIZATION OF NATURAL
DRYING
1-excavation of tailings and placement in windrows
2-redistribution to second series of windrows for further drying
3-transport and distribution of the dried tailings to agricultural fields
Fig.88 PLAN FOR DECREASING FLOTATION SEDIMENTS HUMIDITY
THROUGH MIXING WITH DRY COMPONENTS
1 -excavation of tailings and delivery to mixing facility
2 - supply of dry components such as power plant ash
3-mixIng facility
4- transportation and distribution of the mixture to the fields
168
-------
In order to obtain information about the feasibility of drying the
drained tailings under shielding from atmospheric precipitation, a por-
tion of the evaporimeters was placed under shutter roofs, identical to
those used for Wild's evaporimeters (fig. 11, 15).
NATURAL DRYING UP THE EXPOSED SURFACE OF THE SEDIMEN-
TATION BASIN
Evaporimeter measurements were initiated in July of 1975 using
one evaporimeter without a precipitation shield and four evaporimeters
with shutter roofs. The instruments were installed at the meteorological
station set up near the sedimentation basin.
In April of 1976 three additional evaporimeters were installed
(one with a shutter roof) directly on the main sedimentation basin.
The measurements at the basin were in complete agreement with the
results of evaporimeters set up at the meteorological station. It is
therefore presumed that the 1975 data are representative of conditions
at the basin.
Results of the observations at the meteorological station for 1975 -
1977 are presented on fig. 89 and in table 27. Precipitation, theoretical
evaporation, pan evaporation and measured evaporation are presented.
Pan evaporation, or evaporation from a free water surface is a valu-
able indicator of the composite influence of meteorological elements, and
it informs us of the water vapour absorption capacity of the air under
field conditions.
Losses of water from tailings are clearly larger from unshielded
evaporimeters than from shielded ones. The relative values of evapora-
tion cannot however, be directly compared. Much higher evaporation
occurs from uncovered evaporimeters as a result of considerable and
frequent additions caused by precipitation. The source of much of the
evaporated water was therefore not the water contained in the sediment,
but rather precipitation. For this reason, the efficiency of drying was
much higher in the case of the shielded evaporimeters.
169
-------
Rg89 THE COURSE OF MONTHLY COMPONENT VALUES OF WATER
BALANCE IN mm IN OGORZELEC IN YEARS 1975-1977
P- atmospheric precipitations. Eo~evaporation according to Bac formula.
Ew-evaporaHon of free water table according to Wild evaporimetor under
umbrella shield. Efl -fck) evaporation measured with unshielded soil evapori-
metere, Ef2~field evaporaKon measured with shielded soil evoporimeters.
170
-------
Table no. 27
Average monthly values of precipitation and evaporation
(in mm) using evaporimeters with a surface area of
250 cm2 on flat terrain.
1975 _ 1977
Year
Month
1975
July
August
Septemb.
October
1976
April
May
June
July
August
Septemb.
October
1977
April
May
June
July
August
Preci-
pita-
tion
186.3
53.1
24.1
93.7
34.5
73.0
45.4
112.2
87.1
67.1
77.5
69.6
142.6
133.1
179.8
387.2
Evapo-
ration
accor-
ding
to
Wild
62.4
54.8
47.3
22.6
41.5
67.3
83.7
84.8
56.7
36.1
38.7
38.1
55.6
55.0
61.8
37.4
Evaporimeters
Without precipitation
cover
Reten- Pil- Eva-
tion trate porat.
+11.6 68.8 105.9
- 6.8 6.4 53.5
-12.4 1.9 34.9
+19.6 38.2 35.9
-22.9 20.3 37.1
- 5.1 12.5 65.6
-31.3 12.8 63.9
+ 38.7 35.9 37.6
- 4.1 28.8 62.4
+11.7 29.2 26.2
+ 8.0 50.1 19.4
-19.6 41.7 47.5
-11.8 45.2 109.2
-11.8 81.8 63.1
+ 1.9 106.5 71.4
+214.6 121.5 51.1
Under precipitation
cover
Reten- Pil- Eva-
tion trate porat.
-27.7 3.8 23.9
-25.4 0.4 25.0
- 9.1 0.2 8.9
- 6.7 0.3 6.4
-37.0 6.1 30.9
-45.3 1.6 43.7
-22.4 0.7 21.7
-12.6 3.3 9.3
-15.4 0.7 14.7
-10.4 1.0 9.4
- 7.8 0.8 7.0
_
-43.6 8.5 35.1
-42.9 3.4 21.5
-13.1 0.8 12.3
-19.8 1.9 17.9
The total water loss from 12 kg of tailings contained in an unshiel-
ded evaporimeter was 1.7 kg in a 4 month period in 1975/ The same
period of 1976, the loss of water was 1.2 kg. However, a new sample
lost almost 3.2 kg or 30 % of its total weight in a four month period
171
-------
in 1976. Obviously the efficiency of drying was related to the amount
of water present.
In the unshielded evaporimeter between the first measurement made
in July 1975, and the last in October in 1975, the weight increased
an average of 0.3 kg.
The total evaporation of shielded samples during the period July -
October of 1975 amounted to 64.2 mm (table 27). This corresponds
to a loss of water from an area of 1 ha of 642 000 liters.
During the 7 months period in 1976 from April to October, the loss
of water from sediment was 136.7 mm, or 1367 m of water for every
hectare of flat area of the sedimentation basin.
During first two months if the sample is protected from precipitation,
the tailings loses about 50 percent of the entrained water, through
the warm half of the year. Similarly to the rate of evaporation, the
vertical filtration (percolation) is greatest immediately after placement
of a newly-collected sample into the evaporimeter. In April of 1976
o
(table 27 ) drainage was 6.1 mm, i.e. the equivalent of 61 m of water
draining from an area of 1 ha. During periods of precipitation (July
in 1975 and October in 1976) the water filtration through 30 cm top
layer of sediment is much greater (68.8 and 50.1. mm respectively).
During the period of investigations only in June of 1976 did atmos-
pheric drying exceed precipitation in an unshielded evaporimeter (fig.90).
During the remaining months of the investigations, much precipitation
occurred and the net decrease in water content of the tailings was
minimal.
During August of 1975 and April of 1976 the apparent increase in
the water content is within the limits of measurement error and thus
is not considered noteworthy.
172
-------
20
LL-LLI
vi vn vm ix x 'xi xn11 'n
1975
m'w'v vi 'vn 'vm' x y xi xn i n in iv v vi vn vm
1976 1977
Fig.90 MONTHLY VALUES OF PRECIPITATION AND EVAPORATION
(in mm) IN OGORZELEC FOR YEARS 1975-1977
1-precipitation , 2-evaporation measured according to
Baca formula , 3 - the area where evaporation exceeds
precipi tation prevalence
173
-------
Fig.91. External shield and
water container of
evaporimeter.
Pig. 92. Installation of evaporimeter 's container into external
shield.
Pig.93. Surface of tailings after
initial drying period in
evaporimeter.
174
-------
ATMOSPHERIC DRYING OF TAILINGS PLACED IN WINDROWS
In comparison to the horizontal surface presented by the tailings
pile, greater surface area "atmospheric drying" for a given amount of
sediment is provided if the material is placed in a windrow with slo-
ping sides. Placement of material in cone-shaped piles may induce
faster drying by virtue of the following:
a) increased exposure to sun if the angles of the piles are construc-
ted perpendicular to the sun "s rays and a resultant transferred
to the pile, causing evaporation
b) greater exposure to the drying action of wind
c) increased surface area for evaporation
d) increased runoff of precipitation from the slopes.
In effect the placement in windrows provides a much more favourable
"water balance". The rate of drying can be further enhanced through
insulation of the pile from porous and wet soils. Isolation of the tailings
from a wet soil eliminates the rise of water through capillary action
and, if the impermeable bottom layer is constructed properly, facilitates
drainage of free water away from the tailings.
In order to determine the efficiency of drying tailings under natural
conditions, several windrows were formed near the sedimentation basin
in Ogorzelec.
Two formed in May of 1974 were used. The first pile contained
tailings taken from the internal zone of the sedimentation basin
("A" pile). The second pile was also taken from the internal zone but
was mixed with dry fly ashes from lignite. The lignite ash comprised
about 15 percent of the total mass of the pile ("B" pile). The average
initial water content of the "A" pile was 38.8 percent and of the "B"
pile, 34.6 percent. Both piles were placed near the lowest,. central part
of the smaller sedimentation basin and therefore, for the duration of
the investigations, had contact with surface water collecting in the sedi-
mentation basin. The windrow was shaped as shown in fig. 94 (two
175
-------
Pig. 94. Experimental windrows "A" and "B", contacting free
water table of the subsoil.
Pig. 95. Windrow "C" located on a permeable, sandy subsoil.
Pig. 96. Windrow "D" isolated from subsoil with impermeable foil.
176
-------
cones joined at their bases. The cones were 1.7 m high. In July of
1976 another windrow (»C» pile) was constructed with sediment having
an initial water content of 34.7 percent. It had a shape of an irregular
cone, and was situated on the crown of the main sediment basin embank-
ment (fig. 95). The soil underneath the «C» pile was sandy. In May of
1977, windrow (»D») with the shape of a low (l.2 m tall) mound
trending W-E was constructed on the small sedimentation basin. It was
isolated from the ground with an impermeable foil (fig. 95).
The surface of all piles was very uneven initially (fig. 95). This
was the effect of stacking with an excavator. With time, as a result
of the plasticity of the sediment and the morphological action of atmosp*
heric agents (precipitation, wind, and thawing) the surface of the piles
became smoother. This had the effect of increasing runoff and decrea-
sing infiltration of precipitation, though it also reduced the surface area.
The measure of the effectiveness of the drying process is the re-
duction in the moisture content of the tailings. The changes in the
water content with time for each of the windrows are presented in table
no. 28.
Table 28
Changes in water content of windrowed tailings
with time (%)
esdgnation |
Q
windrow
0
1
A
Type of tailings
windrow
2
Windrow made of
tailings in contact
with free water
from subsoil
'Initial
water
content
date of
observ.
3
38.8
May,74
Interme-
diate
water
content
date of
observ.
4
32.2
Jan., 75
Interme-
diate
water
content
date of
observ.
5
-
-
Final
water
content
date of
observ.
6
32.3
Sept.,77
Total
decre-
ase in
•water
content
period
in
months
7
6.5
29
177
-------
1
B
C
D
2
Windrow of tailings
layered with ash
in contact with free
water from subsoil
Windrow made of
tailings placed on
sandy subsoil
Windrow of tailings
isolated from sub-
soil
345
34.6 31.2
May, 74 Jan., 7 5
34.7 28.7 26.5
March,? 6 Oct.76 May, 77
37.6
May, 77 - -
6
31.4
Sep.,77
24.6
Sept.,77
29.4
Sept.,77
7
3.2
29
10.1
19
8.2
5
In accordance with expectations, the best effect of drying was
observed on the windrow formed on permeable sandy subsoil. During
the time period of 19 months of observations, humidity of this windrow
fell from 34.7 % to 24.6 %, i.e. by 10 %, indicating further trend to fall.
Good effects gave also isolation of windrow from subsoil with
impermeable material (foil). During the five months time humidity here
fell by 8.2. %. Decidedly poorest effects of drying were recorded on
windrows,1 that had contact with free water table of the subsoil. After
the time of 10 months the process of drying of windrows was checked,
and in further period of observations (20 months), humidity content
stayed withing limits of 31-33%.
EFFECTIVENESS OF DRYING SEDIMENTS FORMED INTO WINDROWS
In forming partially dried sediments into windrows to facilitate atmos-
pheric drying one can expect different results caused by differing
inclinations of slopes and exposures to wind and sun. To determine
the effect of these variables, in 1976 soil evaporimeters were installed
on south - and north - facing slopes of a small pile of tailings (fig. 92)
and also on flat terrain close to this pile. The results obtained are
presented in table 29.
178
-------
Table 29
Measurements of field evaporation for evaporimeters placed
on varying and aspects (surface area i 250 cm2).
Year
1
1976
1976
1977
Month
2
April
May
June
July
August
September
Apr.-Oct.
May
June
10 - dav Drccioi i- Pield evaporation (mm)
1
period tation
in mm
3 4
1 11.5
2 1.5
3 21.7
34.5
1 2.6
2 15.7
3 54.7
73.0
1 5.7
2 39.7
3 0.0
45.4
1 12.3
2 22.1
3 77.8
112.2
1 40.4
2 28.6
3 18.1
87.1
1 5.6
2 55.4
3 16.5-
77.5
Total 496.8
1 32.2
2 91.5
3 18.9
142..6
1 17.6
2 81.9
3 33.6
133.1
Location:
northern flat southern
slope terrain slope
567
10.1 23.2 16.2
9.3 25.7 15.5
8.6 9.3 15.4
28.0 58.2 47.1
27.8 33.6 32.7
2.7 7.7 2.7
35.1 32.1 36.6
65.6 73.4 72.0
26.8 18.9 34.6
23.4 22.8 37.1
20.4 23.5 33.5
70.6 65.2 105.2
15.5 14.6 22.3
13.3 14.9 21.3
15.5 13.5 8.4
44.3 43.0 52.0
34.8 29.9 36.3
17.3 17.2 24.8
24.6 20.9 23.7
76.7 68.0 84.8
8.2 8.0 12.1
0.8 6.8 16.3
11.3 6.7 12.2
2Q.3 21.5 40.6
341.4 354.3 439.5
39.O 43.1 48.5
44.4 58.7 56.5
30.8 26.2 32.2
114.2 128.0 137.2
30.1 27.9 30.9
24.9 17.1 35.1
24.6 20.0 32.3
79.6 65.0 98.3
179
-------
1
1977
1977
2
July
August
May -
August
3 4
1 75.1
2 18.7
3 86.0
179.8
1 260.9
2 59.6
3 66.7
387.2
Total 842.7
1
I, . i . . .
567
9.8 6.3 25.4
28.0 24.8 32.2
41.7 42.6 42.0
79.5 73.7 99.6
25.2 23.5 31.0
15.4 21.2 19.7
23.1 18.6 25.2
63.7 63.3 75.9
337.0 330.0 411.O
The evaporation data in table 29 must be considered only indica-
tive of any differences since no repetitions were used and the area
of the; pile was relatively small and asymmetric.
Despite data defficiencies, evaporation was clearly higher on the
southern slope.
The relatively smaller values of evaporation observed during April
and May of 1976 in comparison to flat terrain are probably a conse-
quence of the lower initial water content of the tailings used. In sub-
sequent months the differences were more pronounced, and in October
of 1976 the loss of water from sediment on southern slope was two
times greater than on the flat area. In the period of greatest water
losses (directly after depositing the tailings), very unfavourable eva-
poration conditions occurred on the northern slope with the exception
of June 1977. In April 1976 the quantity of water evaporated from the
northern slope was almost two times smaller than that evaporated from
the southern slope. The total evaporation from the southern slope
during 1976 was 100 mm higher than that occurring on the northern
slope, and 85 mm higher than that occurring on flat land. The size of
the difference is also affected by the latitude of the site.
It is concluded that placement of the partially-dried tailings in wind-
rows allows a higher evaporation rate than placement on flat land.
In view of the fact that the sun is at its highest angle in Ogorzelec
180
-------
during May through July,1 this period is ideal for efficient drying. Win-
drows with slopes of 20° appear to provide optimal conditions for
drying.
At this northern latitude of 50°, the southern slopes of 20° receive,
in May and in July, an average 8 percent more solar energy than
does flat land. In June the gain of energy is 2 percent greater than
on flat land. This may appear to be a small increase, but in terms of
the absolute increase in solar radiation, the effect of increasing this
sum by 2 percent is significant. The northern slopes of such windrows
receive in May and July 20 percent less, and in June 13 percent less
solar energy compared to flat area. Thus there is a gain in energy on
the southern slope, but a much greater decrease in the amount of
radiation falling on surface of the northern slope. Prom the solar radia-
tion viewpoint an asymmetric pile with a long south-facing slope would
present favorable drying conditions.
•
To acquire a full water balance for the tailings one should include
measurements of the surface water run-off. Measurement of this para-
meter is difficult, especially in the case of irregularly-shaped windrows.
One should also, for the empirical confirmation of the theoretical
relationships described above carry out observations of evaporation
on slopes of various exposures and different slopes.
ASSESSMENT OP CONDITIONS POR DRYING ON THE BASIS OP
METEOROLOGICAL DATA
The period of direct measurements of field evaporation in Ogorze-
lec is too short to draw univocaUy broad generalizations.
The weather conditions in the years of 1975 - 1977 did not
correspond to long term average values, a fact which undoubtedly
affects extrapolation of the data.
Therefore, an assessment of conditions for drying should be con-
sidered on the basis of site-specific measurements of the pertinent
meteorological elements.
181
-------
One should emphasize at the start that climatic conditions of
Ogorzelec are, "with respect to drying tailings, not very favourable.
This station is situated in the mountain climates, typified by high amo-
unts of precipitation and cooler temperatures.
To calculate the amount of evaporation based on meteorological
data, a number of formulae are available?. The selection of one of them
is dictated by the geographic location and the climatic conditions of
the region. The climatic data required are the amount of "water lost to
the atmosphere for a particular type of evaporation (from a free water
table, from the surface of land, or a potential evapotranspiration). The
selection of formula also dictates the ability to extrapolate the results
to other climatic situations. The potential evapotranspiration was com-
puted using the formula of Turc.. Publications and atlases giving this
value for Western Europe are available - ref. 44). Potential evapora-
tion was calculated using the Penman (simplified form - ref. 26) and
Thornthwaite formulae - ref. 43. Also calculated was the theoretical
value of evaporation using the Bac formula (ref. 2) and considering
three basic parameters affecting evaporation (solar radiation partial
saturation of the air and wind velocity). The Bac formula enables an
accurate assessment of the air capacity to absorb water vapour. This
formula was developed to fit the climatic region of Wrociaw,1 but it also
suits mountain regions. It has the form:
E = 3d . v + 4 T
o
where: E - monthly total of evaporation (in mm)
d - average monthly partial saturation of air (in mb)
v - average monthly speed of wind (in m/sec. )
t^
T - monthly sum of total radiation (in Kcal . cm"" ).
The formula of Turc was developed for climatic conditions of
Prance and Northern Africa, and considers temperature of air and
solar radiation, but usually omits variations in the humidity features
182
-------
of air (by using a constant for this variable).
It has the form:
E -
t + 15
[(0.18 + 0.62 -|~) + 5oJ
where:
E - potential evapotranspiration for one month (in mm)
t - average monthly air temperature (in °C)
JQ ~ solar radiation at the atmosphere upper limit
t*^
(in cal . cm~ . 24 hrs day)
S/S - relative insolation.
The Penman formula was developed on the basis of free water table
evaporation data collected in England.The simplified formula considers
only the relative humidity conditions of air and wind velocity, and
omits the temperature of air and solar radiation the equation is:
E = i . 0.36 (e - e) . (l + 0.35 v)
where:
E - sum of evaporation through some time period (in m)
i - length of time period, in days
e - pressure of saturated water vapour (in mb)
e - actual pressure of water vapour (in mb)
- wind velocity at 11 m height above the ground (in m/sec.).
v
The Thornthwaite formula for field evaporation was developed for
climatic conditions of United States. It is based, as a rule,1 on data
concerning the air temperature, and does not consider the humidity
conditions the equation is:
183
-------
10 tm a
Ep = 1.06 (— )
where:
E - monthly field evaporation, equal to the so called "monthly
consumptive use of water" (in cm)
t - average monthly temperature (in C)
T - temperature index equal to sum of 12 monthly values
E
^ i • j • / tm x 1.514
of a thermal index i = ( • ..... v1 ;
a - 6.75 . 10~? . T3 - 7.71 . 10"5 T 2 H- 1.79 .
CLf XL-
. 10"2 . T_ + 0.492.
The monthly sums of evaporation computed with first three formulae
during the period of field tests are presented in fig. 97. The field
measurements of evaporation are also presented. With the exception of
July of 1975, August of 1976 and May of 1977, months when the me-
asured field evaporation was relatively high due to very large amounts
of precipitation, the empirically computed values were considerably
higher than the field-measured sums of evaporation. The values com-
puted -with the Bac formula were closest to the actual value. In 1976
those values calculated using the Turc formula were also close to
those measured in the field.
Sums of evaporation calculated using the Penman and Thornthwaite
formulae were greatly overrated as was expected for the climatic con-
ditions of Ogorzelec and in view of the atypical weather occurring
during the experiments.
An estimate of the accuracy of the predicted potential for drying
under atmospheric conditions may be gained by an analysis of the
184
-------
Elmm]
120
«nn.
TUU
80
Kl
40
20
T
.'
/
J
/
f'
IV
A.
/ \
/ \
f
f
_s££~~
s
'
"""•".^
V
/— —
\'''^~" "•— •
f**\
\
^— — —•.—•'"-
""*"•• ..
VI
~*«»
_.— -•"" *•-- *-~
^^
VE
1977
i
N^
•^T^
^^s^n.
vra
Fig.97 MONTHLY VALUES OF EVAPORATION
COMPUTED USING EMPIRICAL FORMULAE AND
MEASURED WITH SOL EVAPORIMETERS IN OGORZELEC
FOR YEARS 1975 -1977
1 - evaporation according to Penman, 2 - evaporation according
toTurc. 3-evaporation according to Bac , 4-evaporation
according to unshielded soil evaporimeters, 5 - evaporation
according to soil evaporimeters under shield .
185
-------
monthly calculations shown in table 30 for the period 1951-1970.
Table 30
Average long term (1951-1970) monthly precipitation
and theoretical evaporation (in mm) at station Jelenia
Gora
Element of banalce
Precipitation
Evaporation ace.
Evaporation ace.
Evaporation ace.
Evaporation ace.
Thornthwaite
to Bac
to Turc
to Penman
to
Apr.
50
51
37
58
41
May
89
68
68
73
82
Jun.
90
74
87
86
106
Jul.
112
73
88
94
119
Aug.
85
62
75
75
105
Sep. Sum
47
50
50
64
70
473
378
405
450
523
Prom the data shown in table 30 it appears that independently of
the formula used to calculate the evaporation, the water balance is
favourable for evaporation only in April and in September (precipitation
lower than evaporation). The amount of evaporation predicted for April
using the Turc formula is low due to specific features of the mountai-
nous climate in Ogorzelec (the formula considers only temperature and
radiation). Values calculated using the Thornthwaite formula are too high
up, since the formula does not consider humidity conditions and move-
ment of air. The character of these variables in mountain climate limits
the amount of evaporation.
In months during which the possibility to evaporate water to atmos-
phere is greatest (May - July), the effect of drying the sediment is
counteracted by the previously mentioned adverse distribution of preci-
pitation in a mountainous climate (fig. 90). However, on the average
of every .4 years the precipitation in months May - July is lower than
sums of evaporation and drying may be accomplished. On the whole
one can assume that losses of water to the atmosphere by evaporation
amount in the region of Ogorzelec are about 400 mm in the summer
half-yi
land).
O
half-year (April - September) (i.e. 400 m from 1 ha of a flat area of
186
-------
In the event detailed, site-specific climatological data are available,
other formulae are available to calculate evaporation. But if regional
data are used, one must be cautious about site-specific projections.
The accuracy of the calculations is strongly affected by the local topo-
graphy.
187
-------
SECTION 12
DECREASING THE WATER CONTENT OF POST-
FLOATATION TAILINGS BY MIXING WITH DRY
MATERIALS
Mixing dry materials with partially dried tailings can produce more
easily handled tailings independent of atmospheric/climate conditions.
Use of this method also creates possibilities of economic utilization
of o^her industrial waste materials if these are normally of easily dried,
and if they are located nearby. Wastes that could be used as dry
additions and which easily absorb and fix water, include waste lime,
smoke-box dust, and fine grained dolomite wastes.
The usability of the tailings increases when they are mixed with
materials that reduce their original consistency from a plastic to a
granular state. With appropriate selection of components, one can im-
prove the fertilizer value of mixture if the content of elements and
compounds essential for vegetative growth is also increased. However,
prior to mixing with these dry substances, the tailings must be paritally
dried in-place (i.e., in the tailings pond) so as to permit handling with
machinery. The technology of drying tailings by mixing with dry com-
ponents is shown in a schematic form on fig. 88.
LABORATORY TESTS
Laboratory tests of mixing postfloatation tailings with three dry
wastes were conducted. The wastes were:
- fly ash from a power plant burning bituminous coal (Czechnica power
plant);
188
-------
- dolomite waste material as a powder;
- fly ash from a power plant burning lignite (Pqtnow power plant).
Mixing of the wastes and tailings was facilitated using a worm mill,
which pressed the materials through a large mesh steel sieve.
The laboratory tests differed according to the type and amount of
components, but had as their objective the determination of optimal
proportions of components that would assure an acceptable consistency,
humidity and structure of the resulting mixture.
It appears from the tests that the best mixture was obtained with
lignite fly ash. The addition of 15 percent by weight fly ash produces
firm, granular consistency and a satisfactory water content. With the
same humidity of post-floatation sediment, to attain similar effects with
the other wastes required 30 percent by weight of bituminous fly ash
or 40 percent of dolomite dust was required.
These proportions of dry wastes ( <1 % moisture) produced a re-
duction in the water content of the treated tailings from about 27 per-
cent to less than 19 percent.
Figures 98, 99, and 100 show the visual characteristics of a mix
of 85 percent (by weight) tailings mixed with 15 percent of any of
the three dry materials. The differences in consistency, structure and
humidity among particular mixtures are quite evident.
These differences result from differing chemical characteristics of
the dry components, which determine the chemical and physical bonds
of water. The chemical composition of dry components and of mixtures
with tailings is discussed in chapter: Chemical composition of tailings
mixtures and their assessment in agricultural utilization (table 33).
FIELD EXPERIMENTS
Field experiments of methods of producing the mixtures were com-
bined with analyses of their distribution of the resulting mixtures on
arable lands as a fertilizer.
189
-------
Pig.98. Mixture of tailings with
dolomite dust (15 %
gravimetrically ).
Pig,99. Mixture of tailings with
ash from bituminous
coal (15 % gravimetri-
cally).
Fig.100. Mixture of tailings with
ash from lignite (15 %
gravimetrically).
190
-------
Based on the results of laboratory tests, the field tests were con-
ducted with fly ash from the lignite-fired power plant, Patnow.
Components were mixed with the aid of an agricultural mixer-feeder
normally used for fodder, an HO-64 type with a container capacity of
250 1 (fig. 101). It was equipped with two mixing, counterrunning worms
driven by an electric motor and with a distribution worm which dischar-
ged the mixture.
Por the field experiments carried out directly in the sedimentation
basin the tailings used had an average water content of 38.8 percent
and the ash had 0.2 percent moisture. Owing to the high water content
of the tailings, the amount of fly ash added had to be increased.
Satisfactory mixtures were achieved with 75 percent tailings and
25 percent fly ash by weight (fig. 102). Initial water contents of each
component and of the mixture are given in table 31.
Decrease in water content of post-flotation tailings after
mixing with dry fly ashes Table 31
Proportion
tailings /ash
(in % by weight)
80/20
75/25
Water content (in %
tailings fly ash
38.8 0.2
38.8 0.2
gravimetrically )
mixture
27f34
24.3
Decrease '
in water
content
(in %)
11.4
14.5
Despite the fact that water content of the mixture of 75 percent tailings
and 25 percent fly ash is still high it is, however, suitable to be dis-
tributed on fields with standard agricultural machinery. This is possible
as a result of the granular structure created by the fly ash coating
the tailings with thin yet somwehat hard layers. This prevented the
agglomeration of the tailings after mixing. The mixed material does not
absorb humidity from air or subsoil for a reasonable time when stored.
After eight days storage of the mixture, tests were made- to distri-
bute it on soils using a typical fertilizer spreader.
191
-------
Pig. 101. Agricultural mixer used in field experiments
to produce mixtures of sediment and ash.
Pig. 102. Mixture of 75 percent tailings and 25 percent
ash, obtained in field tests.
Pig. 103. Spreading of tailings ash mixture of cultivated
meadow using a typical fertilizer spreader.
192
-------
This spreader consists of steel box the bottom of which is a con-
veyor belt, which transports the fertilizer through a regulating opening
onto two screw-like shafts turning in opposite directions and which
distribute the material onto the field (fig. 103).
The experimental spreading was successful since the mixture
was distributed uniformly over the whole area of a meadow and large
lumps were broken up by the distribution system. This prevented
excessice accumulations of fertilizer which could have covered vege-
tation.
CHEMICAL COMPOSITION OP TAILINGS MIXTURES AND THEIR
ASSESSMENT IN AGRICULTURAL UTILIZATION
The results of chemical analyses of tailings and dry waste mixes
are presented in tables 33 and 34. These analyses include those for
individual wastes as well.as mixtures.
The chemical .analyses were those normally used in Poland for
tests of calcium wastes used in fertilization of soils. Manganese (Mn),
copper (Cu), zinc (Zn), cobalt (Co), chromium (Cr), and lead (Pb)
were measured using atomic absorption. Calcium was determined as
CaO, and magnesium as MgO using a complexometric versenate method.
Arsenic was determined using the distillation method.
The chemical analyses presented in tables 32 and 33 indicate
significantly different chemical compositions for the various samples.
The ten samples were:
Sample no. 1 - bituminous coal fly ash (power plant Czechnica)
This fly ash contains a very small quantity of calcium (as CaO), and
magnesium, small quantities of manganese, copper, zinc and cobalt and
quantities of lead, chromium and sulphide sulphur useful for fertilization.
It contains large quantities of silica (SiC^), and of insolubles (NR),
which comprise more than 80 percent of the material.
193
-------
Sample no. 2 - lignite fly ash (power plant Pq.tnow)
This fly ash contains a high quantity of calcium (as CaO) and a
moderate amount of magnesium. It contains over 44 percent CaO + MgO.
Microelements (Mn, Cu, Zn, Co) occur in small quantities. Lead, chro-
mium, arsenic and sulphide sulphur are present in quantities not har-
ming plants. Content of silica and of insoluble materials is relatively
high.
Sample no. 3 - dolomite dust
This material is characterized by a high manganese content (as MgO),
an average calcium content (as CaO), a small quantity of silica and
insoluble materials. It contains 49 percent CaO + MgO. Microelements
and sulphide sulphur occur in small quantities.
Samples nos. 4,5}6,7 - post - floatation tailings taken from different zones
of sedimentation basin in Ogorzelec
Tailings represented by these samples is characterized by an average
content of calcium (as CaO), of silica, and of insoluble parts. The
magnesium oxide concentrations are low. Microelements (Mn, Cu, Zn,
Co) occur in small quantities. The content of sulphide sulphur, of
aluminium • oxide are generally low to moderately low.
Sample no. 8 - tailings^ mixed with 30 percent bituminous coal fly ash
This mixture contains an average quantity of calcium (as CaO), a rela-
tively large quantity of silica and insoluble materials, and an average
quantity of sulphide sulphur. Magnesium was not detected. The content
of manganese, copper, zinc and cobalt is small. Lead, chromium and
arsenic occur in quantities tolerated by plants. Prom the agricultural
point of view, this mixture has a small fertilization value.
Sample no. 9 - tailings mixed with 15 percent lignite fly ash
The content of calcium (as CaO), silica and insoluble materials in this
mixture is average. The amount of magnesium is low and microelements
194
-------
also occur in small quantities. Sum of calcium and magnesium oxides
exceeds 41 percent. Quantities of lead, chromium, arsenic and sulphide
sulphur are tolerated by plants.
Sample no. 10 - tailings mixed with 40 percent dolomite
This mixture contains an average quantity of calcium (as CaO), is low
in magnesium, silica and insoluble materials, has small amounts of
microelements, and an average quantity of sulphide sulphur. Lead,
chromium and arsenic occur in quantities permissible in fertilizer com-
pounds. Small quantities of silica and insoluble materials are present.
The chemical composition of this mixture indicates that the fertilizer
value of this material is almost as good as dolomite (sample no. 3).
On the basis of the chemical measurements of these waste materials
one can conclude the following:
1. The high calcium content of all samples but number 1 make these
materials similar to the agricultural lime group or to calcium -
magnesium fertilizers.
2. Waste material represented by sample no. 1 (fly ash from Czech-
nica) containing a very low content of lime and magnesium, and
a very high content of silica (Si02) and insoluble materials is,
from the agricultural point of view, not suitable as fertilizer. This
fact does not prejudge its eventual use for other economic pur-
poses.
3. Dolomite powder represented by sample no. 3, due to high content
of magnesium, is included into the group of magnesium fertilizers.
It can also be used as a component of calcium - magnesium mix-
tures.
4. Analysed wastes, from fertilizer value angle, contain the necessary
(for plants) micro-elements (Mn, Cu, Zn, Co). When used as fer-
tilizer these can be a partial source of supply.
5. The quantities of lead and arsenic present are in "trace" amounts.
195
-------
6. To determine real fertilizer values of investigated wastes appro-
priate field tests regarding their influence on crops and on charac-
teristics of soils must be performed.
196
-------
Results of chemical analyses for the basic components
in fly ash, dolomite, tailings and mixes thereof
Table 32
No of HO
sample 0/
1
2
3
4
5
6
7
8
9
10
0.18
0.36
1.02
18.77
25.48
21.52
27.46
19.02
18.96
18.34
Content, dry
CaO
3.90
37.75
29.15
44.61
37.56
38.96
38.03
29.71
34.57
36.35
MgO
1.68
6.72
20.22
0.60
1.07
0.87
0.74
-
6.78
6.61
Cl
O.OO
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
s
s ulphi-
de
0.19
0.16
0.08
0.16
2.09
1.93
2.01
2.27
2.27
2.52
mass (in
Pe2°3
4.60
7.63
O.91
0.799
1.584
1.318
1.617
2.87
2.23
4.33
percent)
A12°3
11.18
4.23
1.13
1.37
4.27
3.80
3.96
8.28
3.67
3.07
Si02
58.50
22.33
3.96
10.72
12.02
21.57
12.07
26.36
15.55
9.53
Ins olu—
ble
22.44
5.55
1.11
1.85
1.85
2.11
2.61
9.19
2.93
3.78
Sinte-
ring
losses
2.45
2,11
43.4O
31.86
34.99
36.07
35.21
29.15
32.56
37.76
VD
-4
-------
Table 33
Results of chemical analyses for microelement in fly ash,
dolomite, tailings, and mixes thereof
No of
sample
1
2
3
4
5
6
7
8
9
10
Mn
O.048
0.300
0.086
0.051
0.072
0.062
0.065
0.060
0.090
0.066
Content
Cu
0.009
0.004
0.006
0.0091
0.0119
0.0091
0.0110
0.006
O.O03
O.O25
of component,
Zn
0.015
O.OO6
0.016
0.004
0.008
0.007
O.OO7
0.006
O.O02
0.007
dry mass
Co
O.O09
0.016
0.012
0.0047
O.O037
O.OO80
0.0105
0.012
O.012
0.014
(in percent)
Pb
0.010
0.012
0.018
0.009
O.010
0.010
0.009
0.012
0.012
0.012
Cr
0.023
O.013
O.OO8
O.O10
0.01O
0.01O
0.01O
0.010
O.OO6
0.00
As
O.0012
0.0005
O.OO13
O.OOO2
O.OO01
0.0002
0.0001
O.OOO5
O.OOO4
O.OO03
00
-------
SECTION 13
PROGNOSIS FOR DRYING TAILINGS IN DIFFERENT
CLIMATIC REGIONS
Results obtained during the investigations performed in the region
of Ogorzelec show the feasibility of drying tailings in that not too
favourable local climate. These results and observations may be
extrapolated to project results in regions with dissimilar climatic con-
ditions. The most important components of the water balance for such
extrapolations are the precipitation and evaporation.
It is essential that the appropriate formula for calculation of eva-
poration be selected, for the differences between particular formulae
are often significant as is shown by the results of calculations in
table 30. The formula of Thornthwaite and the Bac formula were
chosen to best suit the available survey data. Computations were made
for the Birmingham region in England representing a type of moderate
oceanic climate, Nantes in France representing a warm oceanic climate,
and for the same reason, the climate at Tampa in Florida, USA,
According to the Thornthwaite classification, Florida has a moist
subtropical climate, while Poland belongs to the zone of moist continen-
tal climate with cooler summers. In figure 104 are included climatographs
showing the annual variations of the most important meteorological ele-
ments for the locations selected. Wroclaw, Poland is located several
scores of kilometers from Ogorzelec, but since it is in a low lying
region shows much better conditions (climatic water balance) for
"atmospheric drying". Rates of evaporation according to the Bac for-
mula for Nantes and for Birmingham are comparable in relation to other
fprmuale and are considered accurate. The sums of evaporation accor-
199
-------
100'
PPolmml
90
80
70
60
50
'.0
10
V
vn vm ix x xi xn
F?Po!nrm i
KV
70
RPoImm]
90
80
60
50
30
20
10
0
100
nml
90
80
70
60
50
40
30
20
10
0
i n ni iv v vi vn vm ix x xi xn
m iv v vi
ix x xi xi
WROCLAW
JELENIA
GtiRA
-, i
TlKcall
10
P
T[Kcal]
1'frci
I1.;
10
5
(i
5
in iv v vi vn VDI
CLIMATOGRAMS FOR SELECTED STATIONS IN EUROPE AND IN POLAND (on the basis
of average data for 1951 -1970 years)
1-total radiation in Kcal erf?, 2-estimated evaporation on the basis of Box formula inrnrn,
3~ atmospheric precipitations in mm/ 4-air temperature in o centigticfe , 5-the >Ji>-
-------
ding to Bac and Penman differ during the period April - September
in Nantes only 2 mm. The course of line plotted in figure 104 points
to great similarity of the total solar radiation and the temperature dis-
tribution during the year.
In Jelenia Gora the precipitation exceeds the evaporation for many
months the evaporation occurs during the summer months. More favo-
urable conditions for drying occur in Wroclaw, where evaporation is
possible during the period of March - September. Lower evaporation
appears possible at Birmingham conditions of oceanic climate of Wes-
tern Europe. This is the result of the high air humidity. More advan-
tageous evaporation conditions occur near the oceanic climate of
Western Europe characterized by the Nantes station. The small amounts
of precipitation occurring during the summer time high radiation values
and temperature indicate that the potential for "atmospheric drying" will
be good.
Table 34 provides average long term evaporation estimates accor-
ding to Thornthwaite, the precipitation and climatic water balance for
the already considered localities, and for Tampa, Florida. The lack of
evaporation data in the table for Jelenia Gora and for Wroclaw during
the December - February months results from the nature of the formula
used which does not allow for calculation of values during months with
the air temperature below 0 C.
The calculated evaporation amounts for the European stations do
not differ greatly among themselves either during the summer half -
year period or during the year. The higher winter time evaporation for
Birmingham indicates the oceanic location of the station. However the
values for Tampa do not reflect this phenomenon. Correspondence bet-
ween precipitation patterns is evident for the mountain climate of Poland
(Jelenia Gora), Ogorzelec, and in the oceanic climate of Western Europe
(Birmingham); the difference is only 3 mm.
Despite reservations about the amount and intensity of precipitation,
it seems that the region of Florida near Tampa has very favourable
climatic conditions for atmospheric drying of tailings. The number of
201
-------
Table 34
Average long term monthly sums of atmospheric precipitation,
of potential evaporation according to Thornthwaite, and. of
climatic -water balance (in mm) for selected stations in different
climatic zones
"^tj-ltir-Li-i L— -. .. . ,.
i *-ji*-*.uon •-————— •»
t Jan.
Feb. Mar.
Apr.
May
Month
Jun. Jul.
s
Aug.
Sept.
Oct.
Nov.
Dec. Apr.-
Sept.
Oct.-
Mar.
1 Evaporation according to Thornthwaite
Jel.G6ra
(Poland) -
Wroclaw
( Poland ) -
Birmingham
(England) 17
to Tampa
° (Florida) 51
9
9
20 30
47 80
41
45
60
99
82
86
83
140
106 119
114 127
103 110
156 165
105
112
90
158
70
73
64
138
43
39
38
112
16
14
20
67
523
557
16 510
50 856
68
62
141
407
1 Atmospheric precipitation
IT el. Gora
(Poland) 29
Wroclaw
(Poland) 23
Birminham fi
(England)
Tampa
(Florida) 67
34 37
26 28
48 44
70 61
55
40
49
52
89
62
56
75
82 103
63 86
48 68
167 198
[ Climatic water
IJel. Gora
( Poland )
Wroclaw
(Poland)
Birminham
(England) +48
[Tampa
[(Florida) +16
- +28
- +19
+28 +14
+ 23 -19
+14
- 5
-11
-47
+7
-24
-27
-65
-24 -16
-51 -41
-55 -42
+31 +33
95
75
67
204
47
40
58
165
49
35
70
77
42
38
67
45
35 471
31 366
60 346
52 881
226
181
354
372
balance
-10
-37
-23
+46
-23
-33
- 6
+ 27
+ 6
-4
+32
-35
+26
+ 24
+47
-22
-52
-191
+44 -164
+ 2 + 25
158
119
-213
- 35
• Year
591
619
651
1263
697
547
700
1253
+ 106
- 72
+ 49
- 1O
-------
days with precipitation are relatively small, very fewdays are overcast
(minimum of overcast in April), and the number of hours with insola-
tion (according to Kendrew - ref. 14) greatly surpasses the data for
European stations (maximum in May 3000 hours).
203
-------
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Western Europe. 1970. Amsterdam, London, New York.
50. 2inkin, G.N. Elektrochimiceskoje zakreplenie gruntow w stroitelstvie.
Stroit. Izdat., 1966. Leningrad - Moskva.
208
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GLOSSARY
aggregate: Agglomeration of fine grains formed through their merging
in space between larger components of soil skeleton.
aggregation: Proces based on merging soil grains into aggregates and
movement of grains towards the center of aggregate.
anaphoresis: Migration of negatively charged particles towards anode.
deaggregation: Reconstruction or destruction of soil agg e gates.
decolmation: Process of unplugging of closed for water flow soil pores.
electrophoresis: Movement of uniformly charged particles of dispersed
phase of colloidal system contained in an electric field.
electroosmosis: Phenomenon based ©n movement of fluid dispersion
medium of colloidal system contained in electric field, versus
occurring in stable phase dispersed phase.
evaporimeter: Instrument for measuring intensity of water evaporation
from free water table, or from surface of soil.
colmatation: Plugging of soil pores of water passages, mainly in effect
of grains migration.
microelements: Chemical elements occurring in very small trace amounts
in soil, necessary for growth and development of organisms.
suphosis: Removal of some soil grains away from the region contained
by electroosmosis.
209
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-79-127
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
1 ELECTROOSMOTIC DRYING OF SLIME CONSISTENCE WASTES
5. REPORT DATE
August 1979 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Kazimierz Ukleja
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Central Research and Design Institute for Open-pit
Mining, Poltegor
51-6l6 Wroclaw, Poland
10. PROGRAM ELEMENT NO.
1BB610
11. CONTRACT/GRANT NO.
05-531+-2
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Laboratory
Office of Research and Development
U. S. Environmental Protection Agency
Cincinnati. Ohio 1*5268
13. TYPE OF REPORT AND PERIOD COVERED
TP-ingl
14, SPONSORING AGENCY CODE
EPA/600/12
15. SUPPLEMENTARY NOTES
Project supported by PL-WO Special Foreign Currency Program in cooperation with
USEPA. Region VIII, Denver, Colorado.
16. ABSTRACT
The objective of this research is the examination of field techniques that
remove water from sludge tailings produced as a waste during floatation of sulphur
ore. The research was conducted with the idea of utilizing these wastes in
agriculture as a soil amendment useful to neutralize acid soils. The main hindrance
to economic utilization of this type of wastes is their semifluid character. This
fluid character persists for many years, making it impossible to economically
excavate and transport the material for agricultural use. The technique investigated
for draining the sludge is comprised of a three stage system of drying as follows:
(l) gravitational draining of water impounded in the bowl of the tailings basin; v
(2) draining a substantial part of the water in the sludge using electroosmosis
which allows removal and some transport of the sludge; and
(3) further drying to a relatively dry, plastic state by spreading under conditions
that facilitate atmospheric drying, or adding dry material to the electro-
osmotic ally dewatered sludge.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a.
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Dewatering
Sludge
Agronomy
Poland Mine Wastes
Slime Tailings
Electroosmotic drying
Sulfur
Fly ash
Air drying
Soil amendment
43B
48A
50B
68C,D
91A
98D
8. DISTRIBUTION STATEMENT
Release to the public
19. SECURITY .CLASS (This Report)
Unclassified,
20. SECURITY CLASS (This page)
a.ssi fi
21. NO. OF PAGES
232
22. PRICE
EPA Form 2220-1 (9-73)
210
•1 U.S. GOVERNMENT PRINTING OFFICE: 1979 -657-060/543Z
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