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REMOVAL OF LOW-LEVEL RADIOISOTOPES
FROM WASTE WATER BY AEROBIC
METHODS OF TREATMENT
CHARLES HILLMAN LAWRENCE
A DISSERTATION PRESENTED TO THE GRADUATE ODUNCEL OF
THEF UNIVERSITY OF FLORIDA
IN PARTIL FULFILLMENT OF THEF REQUIREM6ENTS FOR THE
DEGREEb OF DOCTOR OF PHIOSOPHY
UNIVERSITY OF FLORIDA
December, 1963
I
__
The anchor expresses appreciation to his graduate committee,
Professor F. N. Gilcreas, Chairman, Dr. A. P. Black, Professor G. B.
MIorgan, Professor J. E. Kiker and Professor T. deS. Furman, whose
kind help and constructive criticisms were invaluable in conducting
this study and in the preparation of this thesis.
Special appreciation is extended to Professor G. B. Haorgan, who
not only gave generously of his thme and knowledge as a committee
member but also whose photography adds much to the presentation of
this work.
Gratitude is expressed to the staff of Phelps Laboratory for
providing the facilities and helping with many of the laboratory
analyses that wFere required in conducting this tweestigation.
Appreciation is extended to Mr~s. Marjorie D~u~ez who devoted many
hours toward editing and typing the manuscript.
Recognition and appreciation is extended to the U.. S. Publiic
Health Service whose support under the Aublic Realth Training Program
made this study possible.
The author owes his deepest appreciation to his wife and family
for their patience and encouragement throughout this academic phase
of life.
ACKNOULEDGHENTS
TABLE OF CONTENTS
Page
ACKNOILEDG;HENTS . .. .. . .. ... ... . .. ii
LIST OF TABLES ... .. ... .. .. .. .. . .. .. v
LIST OF FIGURES .. ... . .. ... .. .. .. .. .. viii
ABSTRACT ................... ......... x
CHAPTER
I. INTRODUCTION .. .. .. .. .. .. . 1
II. LITERATURE REVIEP .. .. .. .. .. .. .. ... 5
III. PURPOSE AND SCOPE ... ... .. .. .. .. .. 15
nV. DESCRIPTION OF EXERIMENTAL UNITS .. .. .. . 20
V. PROCEDURE ................... .... 40
VI. DISCUSSION OF OBSERVATIONS .. .. ... .. . ... 49
VII. SU~nNEY AND CONCLUSIONS .. .. .. .. .. . ... 64
APPENDICES
A. CHEMICAL ANALYSIS OF LDEMSTONE FILLER MBDIUn .. .. 69
B. CALCULATION OF CONCENTRATION OF RADIOACTIVE MATERIAL
PRESENT AT SELECTED LEVES OF RAD ICTIVfiT .. .. 70
C. STATISTICS OF COUNTING RADIOACTIVE SAMPUES .. .. .. 72
D. TABULATED DATA -- REMOVAL OF SELECTED RADIONUCLIDES BY
PRIMARY SEDIMENTATION .. .. .. .. . . 74
E. TABULATED DATA AND GRAPES -- 15EIKTML OF SELECTED RADIO-
NUCLIDES BT TRICKLING FILTRATION AND SECONDARY
SEDIMENTATION .. ... .. .. .. .. ... . 82
iii
APPENDICES Page
F. TABULATED DATA AND GRAPHS -- REMOVAL OF SELECTED
RADIONUCLIDES BY LAGOONING .. .. .. .. . ... .. 132
G. TABULATED DATA -- RESULTS OF CHEMICAL AND BIOCHEMICAL.
ANALYSES. . . . .. .. . . 143
LIST OFREFERENCES ........... - ..........- 157
BIOGRAPHICAL'SKETCH.. ......... ......--- -- 162
LIST OF TABLES
Table Page
1. CHARACTERISTICS OF SELECTED RADIONUCLIDES .. .. . ... 18
2. RADIONUCLIDE DOSING DATA .. .. .. .. .. .. ... 41
3. SUMMARY OF REMOVAL EFFICIENCIES ACHIEVED BY TRICKLING
FILTRATION AND SECONDARY SEDIHENTATION UNDER EQUILIBRIUM
CONDITIONS . ... .... .. ... .. . . 53
4, SUMMARY OF REMOVAL EFFICIENCIES AND BUFFERING FACTORS
OBTAINED BY LAGOONING .. .. .. .. ... .. .. .. 59
5. REMOVAL OF P-32 BY PRIZIARY SEDIMENTATION ... .. .. 74
6. REMOVAL OF I-131 BY PROMAKE SEDIMENTATION . .. . .. 75
7. REMOVAL OF K-42 BY PRIMARY SEDIMENTATION .. .~ . .. 76
8. REMOVAL OF Ce-141, 144 BY PRIMARY SEDIMENTATION . ... 77
9. REMOVAL OF Fe-59 BY PRIMAKE SEDPMENTATION .. ... .. 78
10. REMOVAL OF Co-58 BY PRIMAKE SEDIMENTATION .. .. .. 79
11. REMOVAL OF Sr-89 BY PRIMARY SEDP1ENTATION .. .. .. . 80
12. REMOVAL OF MFP BY PRIMARY SEDIMENTATION .. .. .. .. 81
13. REMOVAL OF P-32 BY TRICKLING FILTRATION . .. ... .. 82
14. REMDVAL OF I-131 BY TRICKLING FILTRATION . ... . .. 83
15. RENDVAL OF K-42 BY TRICKLING FILTRATION .. .. .. .. 84
16. REMDVAL OF Ce-141, 144 BY TRICKLING FILTRATION . .. .. 85
17. REMOVAL OF Fe-59 BY TRICKLING FILTRATION .. .. .. .. 86
18. REMDWAL OF co-58 BY TRICKLING FILTRATION .. .. .. .. 87
19. REMOVAL OF Sr-89 BY TRICKLING FILTRATION .. . .. ... 88
20. REMOVAL OF MFP BY TRICKLING FILTRATION . .... . .. 89
I
Table Page
21. ACTIVITY OF P-32 IN FILTER SLOPES . .. .. .. .. ... 98
22. ACTIVITY OF I-131 IN FILTER SLOPES .. .. .. .. .. 99
23. ACTIVITY OF K-42 IN FILTER SLIMES .. .. ... ... 100
24. ACTIVITY DF Ce-141, 144 IN FILTER SLIMES .. .. .. .. 101
25. ACTIVITY OF Fe-59 IN FILTER SLIDES . .. .. ... .. 102
26. ACTIVITY DF Co-58 IN FILTER SLIMES .. .. .. .. .. 103
27. ACTIVITY OF Sr-89 IN FILTER SLIMES .. .. .. ... 104
28. ACTIVITY OF MFP IN FILTER SLIMES ... .. .. .. .. 105
29. RENDVAL DF P-32 BY SECONDARY SEDIMENTATIONJ .. .. .. 114
30. REEDWAL OF I-131 BY SECONDARY SEDIMENTATION . .. .. .. 115
31. REEDVAL OF K-42 BY SECONDARY SEDIMENTATION .. .. .. 116
32. REMDVAL OF Ce-141, 144 BY SECONDARY SEDIMENTATION . ... 117
33. REMOVAL OF Fe-59 BY SECONDARY SEDIMENTATION .. .. .. 118
34. RENBDVAL OF Co-58 BY SECONDARY SEDIMENTATION . ... .. 119
35. REMOVAL OF Sr-89 BY SECONDARY SEDIMENTATION .. .. .. 120
36. RENDVAL OF MFP BY SECONDARY SEDINENTATION .. .. ... 121
37. ACTIVITY OF P-32 IN SECONDARY SLUDGE .. .. .. .. .. 124
38. ACTIVITY OF I-131 IN SECONDARY SLUDGE . ... .. 124
39. ACTIVITY OF K-42 IN SECONDARY SLUDGE .. .... .. 125
40. ACTIVITY OF Ce-141, 144 IN SECONDARY SLUDGE . .. .... 125
41. ACTIVITY OF Fe-59 IN SECONDARY SLUDGE .. .. .. ... 126
42. ACTIVITY OF Co-58 IN SECONDMDE SLUDGE . .. ... . .. 126
43. ACTIVITY OF Sr-89 IN SECONDARY SLUDGE .. .. ... .. 127
44. ACTIVITY OF MFP IN SECONDARY SLUDGE . ... ... .. 127
Table Page
45. REHDELAL OF P-32 BY IAGOONING .. .... .. .. .. 132
.46. RENDELLL OF 1-131 BT ILAGOOING .- . ... .. .. . .. 133
47. Bl>KOYAL OF Ce-141, 144 BT LAGOON1INGC .. .. .. ... 133
48. READELLt OF Fe-59 BY LAGO0NiNG ... . ... . . . 134
49. REPIDELL OF Co-58 BT LAGOONIN~G . .... .. .. .. .. 134
50. RgEHOlML OF Sr-89 BT IAGOONING ... .. .. .. .. .. 135
51. REMBELL OF MFF BY LAGDONING . ... .. .. . 35
52. PRIMARY SEDTHER~T TION BAISINO DhZA .. .. .. .. ... 143
53. TRBICKLING FILEE DATIA (BOD in ag/1) .. ... .. .. 145
54. TRICKLING FILE DATA (Percentage Reduction in BOD) .. 147
55. TBIRICKLG FILSEBR BAth (Ttal Nitrogen in ag/1) .. .. .. 149
56. TRICKLING FILER DATA (Percentage Reduction in Total
Nitrogen) .. .. .. ... ... .. .. .. . .. 151
57. TRICKLING FIL2ER D1ATA (Nitrates in ag/1) . .. .. .. 153
58. TRICKLLING FILTER DATA (Percentage Nitrification) . .. .. 155
vii
LIST OF FIGURES
Figure Page
1. GENERAL VIEW OF THE EXPERPIMNAL. PRPIARY SEDTHENTATION
BASIN ... .. ... .. .. .. .. . -. .. 22
2. .SECTIONAL VIEW OF THE PRICDIRY SEDIHENTATION BASIN
ISOTOPIC DOSING DEVICE .. ... .. .. .. .. .. 24
3. GENERAL VIEW OF THE EXPERIMENTAL TRICKLING FILTER .. 31
4. DOSING DEVICES USED IN THE APPLICATION OF SEWAGE AND
RADIDISOTOPES TO THE EXPERIMNTALL TRICKLING FILTER .. 33
5. GENERAL VIEW OF THE EXPERINENTAL. LAGOON .. .. ... 37
6. AVERAGE REMDVAL OF SELECTED RADIONIDCLIDES BY PRIMARY
SEDIMENTATION .. .................. 51
7. RELATION OF BOD, NITRATIES AND TOTAL NITROG;EN WITH DEPTH
INIFILTER................... ..... 62
8. BEENDVAL OF P-32 BY TRICKLING FILTRATION .. ... .. 90
9. REEDWAL OF I-131 BT TRICKLING FILTRATION .. . ... 91
10. REMOVAL OF.K(-42 BY TRICKLING FILTRATION .. .. .. .. 92
11. RENJDVAL OF Ge-141, 144 BY TRICKLING FILTRATION . ... 93
12. REMDVAL OF Fe-59 BY TRICKLING FILTRATION . .. ... 94
13. REMORAL OF Co-58 BY TRICKLING FILTRATION . .. ... 95
14. RENPDVAL OF Sr-89 BY TRICKLING FILTRATION .. .. .. 96
15. REN3CDRAL OF MIFP BY TRICKLING FILTRATION .. .. .. .. 97
16. ACTIVITY OF P-32 IN FILTER SLIMES . ... .. .. .. 106
17. ACTIVITY OF I-131 IN FILTER SLINES .. . .. 107
18. ACTIVITY OF K-42 IN FILTER SLIDES .. .. .. .. .. 108
19. ACTIVITY OF Ce-141, 144 IN FILTER SLINES .. . ... 109
Figure Page
20. ACTIVITY OF Fe-59 IN FILTER SLINES . .... . .. .. 110
21. ACTIVITY 07 Co-58 IN FILTER SLINES .. ... .. . .. 111
22. ACTIVITY OF Sr-89 IN FILTER SLIDES . ... .. ... 112
23. ACTIVITY OF MFP IN FILTER SLICES .. ... .. .. .. 113
24. RENDVAL OF P-32, I-131, K-42, AND Ce-141, 144 BY
SECONDARY SEDIMENTATION .. .. .. .. ... . . 122
25. REMOVAL OF Fe-59, Co-58, Sr-89, AND MFP BY SECONDARY
SEDIME~NTA1ION . .. .. . .. . ... . 123
26. ACTIVITY OF P-32, I-131, AND Co-58 IN SECONDARY SLUDGE . 128
27. ACTIVITY OF K-42 IN SECONDARY SLUDGE .. . . 129
28. ACTIVITY OF Ce-141, 144 IN SECONDARY SLUDGE .. . 130
29. ACTIVITY OF Fe-59, Sr-89, AND HFP IR SECONDARY SLUDGE . 131
30. RENDVAL OF P-32 BY LAGOONING . .. . . .. .. 136
31. REMOVAL OF I-131 BY LAGOONINlG . . . .. . 137
32. REMBOVAL OF Ce-141, 144 BY LAGOONING .. .. .. . 138
33. REMOVAL OF Fe-59 BY LAGOON1ING .. .. .. . . . 139
34. 252290. DF Co-58 BY LAGOONING .. .. .. .. .. . 140
35. RENDVAL OF Sr-89 BY LAGOONING . . . .. .. . 141
36. REMOVAL OF MFP BY LAGOONING .. . .. .. .. . 142
Abstract of Dissertation Presented to the Graduate
Council in Partial Fulfillaent of the Requirements
for the Degree of Doctor of Philosophy
REHDVALI OF LOW-FLEVEL RADIOISOTOPES FROR YASTEg
RATHER aT saEOBIC BTHsoDs OF TREA'DeNT
By
Charles Hillaan Lawrence
December, 1963
Chairman: Professor F. W. Gilcreas
major Department: Civil (Sanitary) Engineering
This investigation evaluated the removal of low-level radionuclides
from waste water by a complete sewage treatment plant operating under
field conditions. A pilot shee treatment plant employing primary
sedimentation, trickling filtration, and lagooning was utilized. These
processes were subjected to a series of eight experiments involving
phosphorus-32, todine-131, potassium-42, ceriurm-141, 144, iron-59,
cobalt-58, strontion-89, and mixed fission products.
ELhe results indicated that primary sedimentation was relatively
ineffective in removing colloidal and dissolved radionuclides from
sewage. After two hours of continuous isotopic dosing, the effluent
activity approached equlbrium conditions and the average rate of
removal for all materials investigated stabilized at approximately
9 per cent.
TIhe effectiveasess of the trickling filtration process in the
treatment of low-level wastes was 10mited to the ability of the filter
to remove the radioactive components from the main waste stream and to
concentrate them in the solids leaving the filter in a settleable form.
All radionuclides experienced significant uptakse in the filter but, in
some cases, extensive re-entrainment occurred before final removal could
be effected. Consequently, the treatment efficiency of the over-all
process was controlled by the removal accomplished by secondary
sedimentation. The following treatment efficiencies were observed under
equillbrium conditions: 60 to.70 per cent for ironr-59 and cobalt-58;
40 to 50 per cent for ceriumn-141, 144 and mixed fission products;
approximately 25 per cent for potasstum-42 and strontium-89; and less
than 5 per cent for todine-l11 and phosphorus*32.
Uptake studies indicated that the removal of low-level radianuclides
within the filter resulted from the concentration of these materials by
the anogleal slimes present throughout the unit. The various rates of
removal with respect to time were comparatively high during the initial
dose:: but gradually decreased to equilibrous conditions which, for all
materials investigated, were attained after approximately 96 doses.
All rates of removal with respect to depth decreased somewhat exponentially
with increasing depth of medium. Optiman filter depth was six feet,
The concentration of radioactive materials by the zoog1eal slices
resulted fran the action of three mechanics, (a) absorption of the
radionuclides by the microbiota in the slime layer, (b) ion exchange
reactions involving the radioisotopes in the vastaestream and the stable
elements associated with the filter solids, (c) adsorption and physical
trapping of the radioactive materials in and on the altae layer.
Absorption and ten exchange appeared to be comparatively ineffective and
highly reversible, especially for radioactive materials present in their
solable form. Adsorption and physical trapping were indicated to be
efficient and relatively irreversible for colloidal radianuctides.
Lagoon studies indicated that the long detention time and intimate
algal-bacterial contact provided by this process were effective in
dilating, delaying and, in most cases, substantially removing usings"
of low-level radioactive materials. The basin had an effective detention
thme of twro days and achieved the following removals approximately
90 per cent for CcrIum-141, 144 and iron-59; 69 per cent for strontiuma-89;
50 to 60 per cent for phosphorus-32, cobalt-58, and aimed fission
products; and less than 1 per cent for todine-131.
The mechanisms indicated to be effective in the removal of
radioactive materials by lagooning were precipitation by chemical,
physical, and biological means and ion exchange reactions Lawolving the
sulspended radionuclides and the stable materials retained in the basin.
Trvalent materials in their colloidal form and divalent elements
biologically significant in trace amounts wrere removed most effectively.
CHAPTER I
INTRODUCTION
Nith the discovery of X-rays by Roentgen in 1895 and of naturally
occurring radioactive materials by Becqueral in 1896, the Nluclear Age
was born. These events caused a sensation among physicists but aroused
little interest in any other area. Twenty-four years later, it was
announced that radioisotopes could be produced artificially. This gave
renewed interest to the physicists and chemists but elsewhere radio-
activity still seemed to be a scientist's toy with little, if any,
practical application. Widespread interest in this new science was not
initiated until 1942, when the first reactor was built and put into
operation ~by Fermi and co-workers under the West Stands of Stagg Field
at the University of Chicago. The success. of this operation gave the
young field of nuclear science an impetus that shows no signs of
diminishing. These events gave rise to a new source of power -- both
stationary and mobile -- and to a source of radioisotopes both of which
have had a profound effect on industry, medicine and research.
The Lapact of this new technology upon the activities of man can
best be, illustrated by the use of a few statistics. In late 1955, there
were 42 nuclear reactors known to be operating in the world with 29 of
these in the United States (1). Twenty more were under construction,
with nine of these in this nation (1). In 1960 there were almost 100
reactors in various stages of design and construction in the United
States alone (2). At+ that time, the U. S. Navy had approximately 61
seagoing reactors either existing or authorized as power plants for an
aircraft carrier, a cruiser, a destroyer, and numerous submarines (2).
On addition to these reactors, it is expected that in the near future
almost every major college and university in the United States will have
reactors for research and instructional purposes and with the azhaustion
of fossil fuels, nuclear reactors will assume an increasing importance
as a source of power. It has been estimated that by 1980, 65 per cent
of all power plants will be operating on nuclear power (1).
As impressive as these figures may seem, they are not as phenomenal
as chose illustrating the growth in radioisotope usage in the' past 17
years. In ~1946, the first year the Atomic Energy Commission (AEC) made
radioisotopes available to the civilian economy, there were only 86 users
of these materials. The Oak Ridge National Laboratory, the principal
supplier of radioisotopes in the United States, made 281 shipments
totaling 8 curies (3). By 1959, a total of 78,598 shipments had been
made to approximately 5,200 organizations and individuals licensed by
the AEC (4). These shipments represented 537,781 curies of radioactivity
(4). In 1962 about 1,100 shipments per month vere sent to 2,700 users
throughout the United States and 57 foreign countries (5).
There is reason to believe that even though the growth of the use
of nuclear energy has been great, the surface of the application of this
new tool has just been scratched. Myriad uses are in the research and
developmental stage while others have yet to be realized or explored.
However, we cannot accept the assets that nuclear technology offers to
us unless we also assumae the responsibility for the Liabilities which
we know to exist.
In practically all cases where radioisotopes are used, radioactive
wastes are produced. As evidenced by the above figures, the treatment
and safe disposal of these wastes could easily become the major problem
which faces the Atomic Age. The extent to which we can safely dispose
of our radioactive wastes could very well limit our exploration of this
new science.
Aside from being a new problem for which we have no backlog of
experience, radioactive waste disposal has certain features heretofore
unencountered in the practice of waste treatment. For example, it is not
possible, by normal physical or chemical means, to destroy or appreciably
alter the property of radioactivity as we can the noxious properties of
other pollutants. Furthermore, the maxhamn permissible levels for
various radionuclides in waste effluents are several orders of magnitude
lower than those for inactive contarminates. However, the most insidious
property of this relatively new waste is that the biological effects of
exposure to ionizing radiation, even at low levels, can be somatically
and genetically cumulative and irreversible (6, 7, 8).
There are two alternatives in dealing with radioactive wastes,
narmely, (a) concentration and containment, and (b) dilution and dispersal.
Concentrated or high-level wastes usually come La anall volumes and the
methods of disposal, even though expensive, are quite effective;
consequently these wastes pose no serious public health problems.
Dilute or low-level wastes come in large volumes and are usually
discharged into the environment. It is the disposal of these wastes
that is causing an increasing concern in the field of public health and
placing an increasing burden on sanitary engineering.
The future release of low-level wastes by dilution into the
environment must be carried out with caution and under strict controls.
Even though the level of activity in the waste may be well within what
is considered safe limits, it can be concentrated physically, chemically,
and biologically in some phase of the environment, thus posing a health
hazard to this or future generations. To prevent the possibility of
such an occurrence, no effort should be termed excessive.
CHAPTER II
LITERATURE REVIEW
Throughout history man has been concerned with, and often plagued
by, the wastes from his activities. In order to protect his health,
comfort, and. property he has been forced, often belatedly, to take
remedial steps leading to the treatment and safe disposal of these
detrimental products. The coming of the Atomic Age has once again
presented this necessity; however, the incurable results will not allow
us to wait until the situation becomes critical to take remedial steps.
The magnitude of the problem of radioactive waste disposal is not
alarming until viewed in the light of present world activities and ~the
predictions of future capabilities. It has been predicted that by 1965
the United Kingdom alone will be deriving 6,000 megawatts from nuclear
power reactors (9). This annual capacity, which is scheduled to increase
in subsequent years, will require the fission of 6 to 8 tons of uranium-
235 and will produce an equivalent weight of fission products which
will have an associated radioactivity of 109 juries (9). In the United
States it has been estimated that the nuclear power industry will have
produced about 3 x 109 curies of radioactivity in 27 x 106 liters of
solution by 1970 and 6 x 1010 curies in' 11 x 108 liters of solution by
the year 2000 (10). Disturbing as these figures are, it must be
remembered that they are estimates for merely the power reactors of
only two countries. These figures must be augmented by the tastes fran
all other reactors of all types in all countries as well as by the wastes
from the rapidly expanding and diversified uses of radioisotopes in
practically all disciplines of science. The escape of a small fraction
of this activity as low-level wastes -- a highly probable occurrence --
could easily result in billions of gallons annually.
Since it is physically and economically impractical to concentrate
low-level wastes, dilution into the enviromnent is the only alternative.
One of the most common and convenient methods of carrying this out is by
discharge ~into the severs (11, 12). Nevertheless, research concerning
the ability of sewerage systems to receive and dispose of radioactive
tastes has not been sufficient to permit formulation of comprehensive
standards. Consequently, the legal limits of disposal of radioactive
wastes in this manner are those outlined in Randbook 69 (13) for
occupational exposure to various radionuclides in water. Admittedly,
the values contained therein were not primarily intended for use in
waste disposal, but they are well founded and offer a reasonable degree
of safety until more applicable guide-lines can be developed.
Other than these limits, it is quite difficult to locate concrete
information concerning the types and quantities of radioactive vastes
that can be safely discharged into the severs. Neal (14) states that
the discharge of liquids to the severs is safe if the average concentra-
tion of radioactivity in the severr does not exceed 10- microcuries per
milliliter and if the transient concentration does not: exceed 10-1
microcuries per milliliter. He further states that tilese limits can be
relaxed if the radioactivity is due solely to a nuclide of low toxicity.
The Radio Corporation of America Service Company (15) gives some slightly
more specific information. Their recommended daily 10mits of discharged
activity per million gallons of sewage are:
"1. One millicurie of stroncium-90 or polonium-210.
2. One hundred millicuries of any radioactive material having a
half-life of less than 30 days.
3. Ten millicuries of any other radioactive material."
These recommendations are rather brief and seem to be based more on
ruiles-of-thurmb than on the chemical, physical, or biological properties
of the wastes or the ability of the sewage treatment plant to remove
any fraction of the radioisotopes.
Once radioactive wastes are discharged to a sewerage system, the
slimes in the plumbing and severs provide the initial biological contact.
Talboys (16), in a laboratory study of the retention of iodine-131 by
bacterial slimes in drains, found that even though this isotope is not
metabolized by the organisms in the slimes, small quantities are retained
by physical adsorption and are subject to removal through successive
flushing. He calculated that any hazard to sever workers exposed to
sewage bearing this isotope, would be quite low. Reid (17) made similar
findings whien~ studying the sorption and metabolic uptake of phosphorus-32
by bacterial slimes.
Considerable attention has been given to the effects of radioactivity
on the organisms responsible for the biological treatment of sewage.
Dobbins et al. (18), using oxygen utilization as a criterion for measuring
oxidation rates in domestic sewage, found that these rates were not
affected by phosphorus-32 in concentrations up to 1 millicurie per liter
and only a small reduction in the rate of oxygen utilization was observed
-8-
at 10 millicuries per liter. Iodine-131 in concentrations up to 10
millieuries per liter produced a decrease in the rate of oxygen utiliza-
tion which resulted in a reduction in the total oxygen demand of about
10 per cent by the seventh day.
The relative ease with which sludge digestion can be reduced to a
small scale has induced considerable experimentation with this treatment
process. Babbitt et al. (19), in laboratory studies with phosphorus-32,
iodine-131, sulphur-35, and calcium-45 found that 100 millicuries per
liter had no measurable effects but 200 millicuries per liter gave a 17
per cent reduction in gas. At the lower concentration, phosphorus was
found primarily in the sludge phase, about 75 per cent of the iodine was
in the liquid phase and about 90 per cent of the sulphur was found to be
concentrated in the solids.
Phosphorus-32, iodine-131, and sulphur-35 were also used by
ERarmeson and Dietz (20) in their study of the effects of radioactive
substances on sludge digestion. They found that 110 millicuries per
liter had no apparent effects and 200 millicuries per liter were required
to produce inhibitory effects. They also found that phosphorus and
sulphur tended to concentrate in the sludge while iodine was more
concentrated in the liquid.
Grune et al. (21, 22), using carrier-free iodine-131, could detect
no significant difference in the gas production of their laboratory
digestors when dosed with up to 300 millicuries per liter. At 600
millicuries per liter a significant reduction occurred in the reaction-
velocity-d'onstant but the ultimate gas production, volatile solids
reduction, and concentration of volatile acids were not affected.
In further studies using carrier-free phosphorus-32, they found signifi-
cant gas reductions at 200, 400, and 800 millicuries per liter. At the
higher dose, a decrease in volatile matter and a tenfold increase in
volatile acids were noted.
Primary treatment processes have received relatively li title
investigation with respect to their ability to treat radioactive wastes.
Belcher (23), in a laboratory investigation concerned with some of the
radioisotopes of interest in the medical profession, found that not more
than 5 per cent of the influent activity was removed from domestic sewage
when subjected to sedimentation.
Secondary treatment processes, on the other hand, have been involved
in several -investigations. Using laboratory scale trickling filters
dosed with domestic sewage, Belcher (23) found that when bromine-82,
iodine-131, sodium-24, phosphorus-32, and cobalt-60 were added to the
sewage the concentration of radioisotopes in the effluent rose to an
apparently steady value after 16 hours. The proportions of the radio-
isotopes removed were 6, 5, 13, 77, and 79 per cent, respectively.
Nevall et al. (24) conducted laboratory investigations on the
removal of plutonium from laundry wastes. They compared a trickling
filter with chemical precipitation and concluded that the trickling
filteer, operating at a 15 to 1 recirculation ratio, gave effective
removal and the resulting sludge volume was only about 4 per cent of
that produced by chemical treatment of these wastes.
Gloyna and Geyer (25), using a synthetic laundry waste and rotary
tubes, simulated an 8-foot trickling filter loaded at 8 million gallons
per acre per day. They found that the slides retained 40 per cent of
the applied cerium-144 and 20 per cent of the applied phosphorus-32.
They concluded that the primary factors which control the removal of
radioactivity by microorganisms are ph, viability of the organisms, type
of isotope, toxicity of the waste to the aderoorganisms, and the ratio
of stable to radioactive isotopes.
Carter (26), using 2-inch diameter laboratory filters dosed with
savage containing carrier-free iodine-131, found that a 6-foot filter
had a removal efficiency of 85 per cent with most of the removal
occur-ring in the first 3 feet. This removal efficiency was found to be
fairly stable at dosing rates from 2 to 6 million gallons per acre per
day.
In a laboratory study using a synthetic waste and a trickling
filter 5 1/2 inches in diameter by 4 feet deep, Klein et al. (27)
concluded' that trickling filters could remove 70 to 85 per cent of the
gross beta activity due to mixed fission products. They also found
that the removal of phosphorus-32 was highly dependent upon the concen-
tration of the stable phosphorus in the waste. In this respect, they
reported that the removal of phosphorus-32 was as low as 20 per cent
at a stable phosphorus content of 6 1/2 milligrams per liter and as
high as 88 per cent when the stable phosphorus content dropped to
1 65/100 milligrams per liter.
Radioactive laundry tastes have also been studied by Wiederhold (28)
who, using a trickling filter constructed from two 30-gallon drums,
concluded that trickling filters not only gave satisfactory removal
of the applied alpha and beta activities but also removal of organic
materials that interfere with subsequent chemical coagulation and flocen-
lat ion.
In treating radioactive laundry tastes of pH 3.0 to 5.0, BOD 200 to
800 milligrams per liter and beta activity of 180 disintegrations per
minute per milliliter on single and two-stage laboratory trickling
filters, Dobbins (29, 30) found the sludge to contain 200 times the
activity of the raw waste. These studies indicated that 90 per cent
of the gross activity of mixed fission products was removed at loadings
of 250 pounds of BOD per acre-foot per day but that removal decreased
with increasing loading rates. It wjas observed that the sludge activity
was essentially independent of the organic loading rate but was dependent
on the activity level of the vaste. The percentage removal of the
various elements were: cerium, 97 3/10; ruthenium, 79 1/10; strontium,
69 4/10; yttrium, .86 7/10; and zirconium-niobium, 79 1/2.
Fowler et al. (31) in studying the retention time of trickling
filter slimes with rubidium, found that adsorption did take place but
was inherently reversible. They observed a slow leaching of the activity
from the filter for 37 hours after dosing occurred.
Activated sludge treatment as a means of radioisotope removal from
liquid wastes was suggested by Ruchhoft (32) as early as 1949. Later,
he and Setter (33) developed an activated sludge from synthetic sewage
for the treatment of radioactive wastes. In subsequent laboratory work
(34), they concluded that the activated sludge process is not efficient
in removing isotopes that are not utilized by, or readily absorbed on
biological floc (e.g. iodine-131), nor is it efficient for removing
radioisotopes that are isotopically diluted with their stable counter-
parts (e.g. phosphorus-32). They did find, however, that the process
gave good removal of plutonium even in the presence of organic sequester-
ing agents.
Belcher (23), as a result of his laboratory research, concluded that
the uptake of sodian~-24 and bromine-82 by activated sludge from sewage
is very slight. In both cases the proportion removed in a 6-hour
aeration period was about 10 per cent.
Kaufnani et al. (35, 36, 37), in their laboratory scale investigations
of the removal of radioisotopes by the activated sludge process, arrived
at the following conclusions.
1. Of the three isotopes studied, strontium-89 experienced the greatest
removal with iodine-131 showing intermediate removal and phosphorus-
32 undergoing the least removal.
2. The removal of radioisotopes, such as the three aboye, depends on
carrier concentration and on the concentration of other isotopes
that exhibit chemical similarity or interference.
3. Batch studies show greater removal than those employing continuous
flow and the removal increases with increasing solids.
4. With slugs of radioisotopes, greater removal is observed with high
solids content but, with continuous radioisotope flow, the converse
is true.
Plutonium bearing laundry waste, in a mixture with settled domestic
sewage, was treated by the activated sludge process by Reading and
co-workers (38). Using 20-liter bottles as aeration units, they found
good removal with long aeration periods followed by filtration of the
effluent. They also observed a high concentration of plutonium io the
zoogleal mass of sludge even when the raw feed was low in radioactivity.
This would necessitate special handling of the excess sludge.
Eden et al. (39), in their laboratory scale investigation of
activated sludge, found that equilibrium between the activities of the
liquid and solid phases was reached after 16 hours aeration. They
obtained removals of 95 per cent for plutonium-239, 89 per cent for
iodine-131, 42 per cent for strontium-90 and ruthenium-106, and 32 per
cent for cesium-134.
In studying the efficiency of sand filters for removing low-level
activity from laboratory tastes, Gemmell (40) observed 98 per cent
removal of the activity for the first 16 dosings (4 days), 70 per cent
removal for the next 10 dosings (2 1/2 days) and only 20 per cent after
37 dosings (9 days). Of the activity absorbed in the bed, 90 per cent
was found in the top 3 inches, 8 per cent in the next 9 inches and the
remaining 2 per cent was located in the lower 5 feet.
Eden- et al. (39), using slow sand filters on the laboratory scale,
found that plutonium-239 and cerian-144 were effectively removed but
iodine-131, strontium-90, and ruthenium-106 experienced a rapidly
decreasing removal efficiency with increased dosing.
Evaluation of the effectiveness of oxidation ponds (lagoons) on the
removal of various radionuclides, has also been the object of investi-
gations on the laboratory scale. Steel and Gloyna (41, 42) found that
iodine-131 was not removed to any great extent but appreciable removal
of mized fission products was experienced. The removal of phosphorus-32
and strontium-89 was found to be dependent upon the concentration of
stable counterparts and chemically similar isotopes.
Gloyna at al. (43), in their experimental work, obtained very low
removals of cesiulm-137 and iodine-131; however, they did find that
-14-
35 per cent of the applied strontium-89 could be removed by a single
laboratory lagoon and up to 80 per cent could be removed by three
lagoons in series. Mixed fission products were found to collect in the
slime and slndge with slow release back to the liquid phase. It was
found that the algae, under optinuum conditions of light, temperature,
pH and nutrients, could remove as much as 95 per cent of the influent
cerium- 141.
berman and Gloyna (44), in summarizing the investigations on the
removal of radioisotopes by oxidation ponds, reached the following
general conclusions.
1. Oxidation ponds can be used effectively to concentrate, delay- and,
possibly, remove radioisotopes from waste streams especially when
the concentration of radioactivity is near the maxirmum permissible
concentration (HIPC).
2. Intermittent slugs of low-level amounts of radioisotopes can be
diluted and, in many cases, removed by the long detention tiums
utilized in oxidation ponds.
3. Where climatic conditions are favorable, oxidation ponds can be
economical both as a BOD reduction device and for treating low-level
radioactive wastes.
CHAPTER III
PURPOSE AND SCOPE
The literature seems to indicate that appreciable work has been
done in the general area of the removal of radioisotopes by sewage
treatment processes. However, upon closer inspection it is apparent
that, for the most part, this work was carried out on a laboratory scale
under exactly controlled conditions and only a few isotopes were used in
investigating a single phase of treatment. In most cases laundry waste,
or a synthetic waste of some type, was used as the vehicle. In a
sizable portion of these studies, interest was centered on the effects
of the radioisotopes on the treatment process rather than the action of
the treatment process in removing the radioisotopes from the vaste stream.
Careful inspection of the experimental results shows that, in some cases,
appreciable disagreements and even contradictory conclusions have
resulted from similar investigations. One case in point is the
ability of trickling filters to remove iodine-131. Carter (26) reported
a removal efficiency of 85 per cent while the value recorded by Belcher
(23) was only 5 per cent.
Unfortunately, conditions developed in the laboratory using small
scale units operating under completely controlled conditions are
incompatible with conditions prevailing in the field. Such laboratory
results may be valid for indicating general trends or for comparison
purposes but they can be grossly misleading when projected to large-scale
-15-
_ __
-16-
field operations. There are probably few other fields of science where
these statements hold more truth than in the field of waste treatment.
The prevalence of laboratory investigations of the various aspects
of biological treatment of radioactive wastes and the virtual nonexistence
of their large scale counterparts, has been noted (45). As pointed out
previously, the savage treatment plant is rapidly becoming the focal
point for the disposal of practically all of the low-level radioactive
wastes from our urban activities. Ip view of this, there is a pressing
need for initial pilot scale research utilizing an entire sewage treatment
plant operating under true field conditions free from the inherent
inadequacies of laboratory scale research and synthetic wastes. It was
this need that provided the purpose for this investigation.
More specifically, the purpose of this investigation was to render
an evaluation of the effects of a complete sewage treatment plant
operating under actual field conditions on sewage that has been
contaminated with a representative spectrum of radioisotopes in low-level
amounts. Of primary interest was not only the fate of the radioisotopes
but also the underlying procedures responsible for their removal.
To achieve this goal, a pilot size sewage treatment plant employing
a standard rate trickling filter and a lagoon was utilized. In order to
facilitate the investigation on this scale and to comply with the
restrictions on the use of radioactive materials and the discharge.of the
resulting wastes to the receiving streams, it was decided that this
study be conducted with relatively short half-life radioisotopes. This,
however, in no way 10mits the scope of this investigation since numerous
such radioisotopes, representing practically the entire range of
-17-
radionuclides, are readily obtainable. The radioisotopes selected were
not only representative of the periodic table but also representative of
the significant fission products as well as being among those considered.
most biologically hazardous.
The radionuclides chosen, along with some of their more important
characteristics, are listed in Table 1. In this tabulation, the
information concerning maximum permissible concentrations and critical :
organs was obtained from the Federal Register (46), handbook 69 (13),
and Radiation Mb~nitoring (47). Data concerning the other characteristics
were obtained from the Badiolog~ical Health Randbook (18).
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I
CH~APTERI IV
.DESCRIPTION OF EXPERIMENTAL UNITS
Introduction
All experimental units and laboratory facilities used in this
investigation are located at the Earle B. Phelps Laboratory for Sanitary
Engineering Research at the University of Florida at Gailnesville. This
laboratory is not only active in waste treatment research but also in
environmental radiation surveillance and the teaching of sanitary science.
At present the pilot sewage treatment plant, operated by the staff of
this laboratory, consists of a primary sedimentation basin, an Imhoff
Cank, an extended aeration unit, two trickling filters, numerous sand
filters, two sludge digesters and a lagoon. These units are arranged so
that they can be operated independently or in practically any conceivable
series and under a wide range of loading conditions. Collectively, they
have a treatment capacity of approximately 60,000 gallons per day. For
'---'- --C'-- ir u== decided to employ those units
under standard loading rates.
The sewage is received at the research laboratory's pilot plant
from the University of Florida campus and included drainage from
dormitories, classroom and laboratory buildings, cafeterias, family
housing units, fraternities, sororities, a milk processing plant, and
the J. Hillis Miller Health Center. It is received at the pilot plant
-20-
at a uniform rate from the campus sewage treatment plant after it has
been screened, comminuted, and degritted. As expected, the strength of
the sewage was found to vary markedly throughout the day and also
throughout the week. Because of the short flow time in the mains, the
savage reaching the plant was normally fresh.
Primary Sedimnentation Basin
The function of a primary sedimentation basin is to provide, in the
initial phases of sewage treatment, a relatively quiescent state so that
those suspended particles having a higher specific gravity than the
liquid phase will settle under the influence of gravity. Thus, the pri-
mary purpose of such a unit is to reduce the solids load on succeeding
treatment processes thereby increasing the treatment efficiency while
reducing maintenance. Most sedimentation basins are designed an a
continuous flow basis and are equipped with any one of a variety of
sludge collection and removal devices. Under normal loading rates, such
treatment units can remove 50 per cent of the influent suspended solids
and 35 per cent of the applied BOD.
The basin employed in this investigation (Figure 1) is rectangular
Tesettling cmarcaent: rs 14 Eee r n rengen, r reer: In n wrus nu
aen infuent: eacrsrouxon cox as werr as rnlluenr atar srrxaus ....
The settling compartment is 12 feet in length, 4 feet in both width and
depth and has a free-board of 1 foot. The effluent from this compartment
flows over a 4-foot long notched weir which leads to a collection trough.
From here it enters a 4-inch diameter pipe leading to an outfall in a
reinforced concrete dosing tank. It was at this outfall that the primary
effluent samples were taken.
-22-
Pig. 1.- General view of the experimental priarynr sedimentation
basin.
-23-
The unit is equipped with two sludge collection hoppers having a
combined capacity of 338 gallons thus giving the basin a total capacity
of 1,778 gallons. For the course of this investigation, this unit
received sewage at the approximate rate of 15 gallons per minute.
Calculations yield a theoretical detention time of 96 minutes, a surface
loading rate of 450 gallons per square foot per day and a theoretical
horizontal velocity of 1/10 of a foot .per minute.
Withdrawal of sludge is accomplished by means of a hydrostatic
pressure of 3 feet. The withdrawal pipes are 4 inches in diameter with
the flow controlled by shear gates located in receiving hoppers adjacent
to the unit.
The dosing device (Figure 2) used in the application of radioisotopes
to this unit was composed of a 55-gallon steel drum equipped with a
polyvinyl chloride discharge line attached to the bottom of a weighted
float. The latter, which was 5 inches in diameter by 3 1/2 inches deep,
projected 1/2 inch above the surface of the liquid in the drum, thus
providing a constant hydraulic head of 3 inches above the intake of the
discharge line. The discharge line itself was 1/4 inch in diameter and
3 1/2 feet long with its lower end attached to a 1/4-inch diameter valve
which passed through the wall of the drum, flush with the bottom.
The discharge of the apparatus as described above would be a function
of the depth of the liquid in the drum. In order to eliminate this
dependency, an air relief line was placed in the discharge line 5 inches
down stream from the intake. This line was composed of a short piece of
1/4-inch diameter polyvinyl chloride tubing connected to the discharge
line through a glass "T" and projected vertically through the surface of
the liquid.
-24-
Scale: 1" =6"
Fig. 2.- Sectional view of the primary sedimentation
basin isotopic dosing device.
-25-
This apparatus was calibrated to deliver a uniform discharge of 1
quart per minute over a span of 45 gallons, starting with the drum full
and continuing to within 6 inches of the bottom. The solution containing
the radioisotopes was added to the basin influent as it entered the
distribution box at the head of the unit. The thorough mixing occurring
at this point insured a complete distribution of the isotopic solution
throughout the incoming sewage before it entered the sedimentation zone
of the unit.
In order to facilitate the dosing and representative sampling of
both the primary sedimentation basin and the trickling filter and to
prevent the radioisotopes in the settling tank effluent from entering the
other units before they could be systematically investigated, it was
decided to operate the primary sedimentation basin on a line independent
of the other units being investigated.
Standard Rate Trickling Filter
Trickling filters are applicable for secondary treatment of wastes
susceptible to aerobic biological processes. They have been used with
success on domestic sewage, industrial wastes and mixtures of industrial
and domestic wastes. They have the ability to recover from shock and
toxic loads and to provide good performance with a minimum of skilled
technical supervision. Probably no other biological treatment process
is so versatile in its application or so dependable in its performance.
These units are normally 6 to 8 feet deep and have stone medium
2 to 4 inches in diameter. They are commonly round in plan and have
some type of rotary distribution for applying the sewage to the surface
of the bed. Collection of the treated effluent requires an under-drain
system which, due to frequent sloughing of solid material from the filter,
usually leads to a secondary sedimentation basin. Standard rate trickling
filters receive hydraulic loadings of 1 to 4 million gallons per acre
per day and under normal conditions, a 6-foot~ filter should remove 80
to 85 per cent of the applied BOD.
The action occurring in such a unit can be described briefly as the
biochemical sorption of the complex organic matter present in savage,
carried out by allowing the sewage to come in contact with the microar-
ganisms active in its degradation. The means of contact is usually
provided by the distribution of primary treated sewage over the top of
a unit containing a coarse medium, the surface of which is coated with
a viscous jelly-like matrix of microorganisms called zoogleal slimes.
As the sewage trickles down through the bed, it passes over the surfaces
of these slimes in a relatively thin film. It is here that the colloidal
and dissolved organic matter is removed from the liquid phase, used as
a source of energy by the biota in the slimes and replaced in the
liquid phase by their stable metabolic products.
It is appropriate that the underlying theory of the stabilization
of organic matter by trickling filters should be presented at this point,
especially since it is expected that this theory will find considerable
application in discussing the ability of a filter to remove radioisotopes.
The early theories concerning: the phenomenon of purification by
trickling filters were generally based on the process of absorption.
In the light of later developments in the chemistry of colloids, the
true mechanism appears to be that of adsorption. Based on this premise,
Buswell (49, 50) developed a more comprehensive theory explaining the
action of these units. His work, which represents the presently
accepted theory, has been summarized by Metcalf and Eddy (51) and by
Fair and Geyer (52) as follows:
"1. In the surface film of liquids, the concentration of dissolved
matter tends to change in such a way as to decrease surface tension.
If, therefore, a substance dissolving in a liquid increases the
surface tension of the solution, the film concentration of the
substance tends to become less; if it decreases the surface tension,
its film concentration tends to become greater. (Most salts and all
strong bases increase the surface tension of water; but, ammonia and
nitric and hydrochloric acids decrease it.) Substances in the
colloidal state are believed to act in a similar way and there are
found in sewage colloidal soaps and proteins that tend to concentrate
in a surface film. These changes in film concentration are not
restricted to the air-liquid interface, but seem to apply also to
the interface between the bacterial slime and the liquid. The
extent of the interface or contact surface is, therefore, important.
"2.- At the jelly-sewage interface the following occurs:
a) The substances concentrating at the interface are adsorbed to
the contact surfaces and thus removed from the sewage being~
filtered ;
b) The adsorbed substances are attacked by the enzymes and living
organisms present in the slime;
c) As rapidly as these substances are removed by digestion or
direct absorption into the living cells, others come to the
interface and further removal is effected;
d) In the presence of air, the products of decomposition of organic
matter are chiefly carbon dioxide, nitrates, and a humus-like
residue. The gas escapes .. nitrates, being salts, increase
the surface tension of water and therefore pass from the
interface into the flowing sewage; the humus-like residue must
either be removed .. or sloughed off from time to time. .
It is an important fact that -the humus .. settles readily,
unlike the colloidal matter from which it largely originated."
This summnary omits a very important hypothesis that was proposed by
Buswell. This hypothesis was that the rate of purification is directly
related to the law of mass action. Simply, this law states that the rate
at which a reaction occurs is in direct and constant proportion to the
concentration of the reactants. Incorporation of this law into the
above summary yields the presently accepted theory of trickling filter
operation.
In summaryv the action of a trickling filter can be described as
follows: removal of colloidal and dissolved material by adsorption on
the zoogleal surfaces; oxidation of the organic material by the biota
which constitutes the zoogleal mass; resolution and sloughing of the
oxidized material and its passing from the filter. The removal of
organic -material by adsorption on the bacterial jelly seems to be a
concentration phenomenon, with the rates of removal and oxidation being
dependent on the rate of oxygen transfer, temperature and the surface
area involved.
The filter used in this study is 8-feet deep and has an inside
diameter of 6 1/2 feet, thus giving a surface area of 33 18/100 square
feet and a medium volume of 9 6/10 cubic yards. The filter tank is
constructed of 3/8-inch steel plates, circular in plan, with a sloping
concrete bottom covered with formed tile under-drains which lead to a
4-inch diameter effluent line. This line outfalls into a 12-inch
diameter semi-circular trough leading to the secondary sedimentation
basin.
The sampling ports consist of short 6-inch diameter nipples, which
are welded to the steel shell of the filter.. There are 16 of these
nipples, w ich are aligned in pairs in order to support, on the inside
of the filter, two facing 4-inch steel channels separated by 3/4 of an
inch and extending across the filter. These channels have triangular
shaped cuts in their flanges to facilitate the passage of sewage, They
are positioned-so as to form a 3 1/2-inch by 3 1/2-inch opening through
which liquid and slime samples may be taken without being obstructed by
the medium. Each part has a small metal bar welded horizontally across
the middle of the opening. Each pair of bars supports a flattened 1-inch
diameter aluminum conduit cut the length of the channel and used for
mounting the glass slides employed in sampling the filter slimes.
Sampling ports are located at the 1/2 and 1 foot depths and at each foot
thereafter for a total depth of 7 feet. The samples representing the
B-foot depth are taken at the point where the filter effluent empties
into the secondary influent trough. In order to prevent short-circuiting
of the sewage as it passes through the filter, all channels are placed
in different vertical planes.
Liquid samples were collected at the various sampling ports by
means of aluminum sampling troughs, which are semi-circular In shape,
3 inches wide and 8 feet long. At one end of the trough is an outlet
nipple onto which a length of 3/4-inch diameter garden hose is connected
to allow the continuous filling of the 600-milliliter beakers in which
the samples were collected. A general view of the filter showing the
ports and the equipment used in sampling appears in Figure 3.
The medium used in the experimental filter is a native limerock
furnished to the U~niversity of Florida by the West Coast Rock Company
of Fort Myers, Florida.a These heavy and fairly uniform stones have an
average size of 4 inches, which exceeds the maximum value given in the
"Sewerage Guide" of the Florida State Board of Health. The stones have
porous and irregular surfaces that provide an excellent foundation for
the growth of the zoogleal slimes. In order to prevent the formation of
open pockets under the channels, to hold settling to a minimum and to
insure even distribution of sewage throughout the filter, the medium
was hand-placed. This limerock is performing excellently as a filter
medium and has shown no evidence of settling or deterioration after
almost 5 years of use.
The sewage being treated by this unit receives primary sedimentation
in an Imboff tank before being discharged into a large reinforced
concrete receiving tank. From here the sewage is pumped at a constant
rate by a centrifugal pumap to an elevated dosing chamber. Part of the
flow coming into this chamber flows over an adjustable veir into a
bell siphon chamber, the head on this weir being kept constant by twe
large overflows that return the excess sewage to the receiving tank.
aA complete chemical analysis of this material appears in Appendtz A.
-31-
Fig. 3.- General view of the experimental trickling filter.
The sewage is then siphoned to a distribution box from which it flows
over a series of adjustable weirs, one of which leads to the filter being
Investigated. Mechanically driven rotary distribution arms operating at
a rotation rate of 1 revolution per: minute provide a uniform distribution
of the sewage over the filter medium.
For the course of this investigation, the bell siphon cycle was
maintained at a constant 7 3/4 minutes which was divided into a 2 3/4-
minute dosing period and a S-minute resting period. The distribution
weir was adjusted to send approximately 17 gallons per cycle to the
filter. This corresponds to a hydraulic loading rate of 4 1/10 million
gallons per acre per day.
The device used in the application of radioisotopes to the influent
of this unit was basically composed of a. float switch, a-Sligma Motor pump
and a holding tank. The float switch was mounted on a vertical support
bolted to the wall of the bell siphon chamber and the float was allowed
to fluctuate with the liquid level in this chamber. The pump, powered
by a 1/20-horsepower electric motor operating through a gear box, was
housed on a platform over the distribution weirs. The holding tank,
which was located adjacent to the pumap housing, was constructed from a
14-gallon polyethylene carboy equipped withi a bottom drain connected to
a 3/16-inch diameter rubber tube. The shielding for this container was
provided by a 1/8-inch thick steel tank, 15 inches in diameter by 30
inches deep and equipped with a twist-lock lid. The rubber tubing
connected to the bottom of the carboy projected through the bottom of
the steel tank, extended through the pump, and terminated on the down-
stream side of the veir which dosed the filter. The arrangement of these
units is shown in Figure 4.
-33-
Fig. 4.- Dosing devices used in the application of sewage
and radioisotopes to the experimental trickling filter.
As the level of the sewage in the siphon chamber rose to the point
at which dosing started, a stop on the float staff, acting through the
float switch, started the electric motor which operated the pump. The
latter pumped the isotopic solution from the holding tank to the sewage
being sent to the filter. The turbulence provided by the drop from the
weir to the filter influent~ line along with the mixing occurring in the
influent line and' the distributor arm nozzles, provided a complete
distribution of the isotopes throughout the sewage. As the level of the
sewage in the siphon chamber dropped to the point where the siphon was
broken, a second stop on the float staff switched off the pump.
This dosing device was calibrated to deliver approximately 3150
milliliters of isotopic solution per dosing cycle. Under the installation
and operating conditions used, the discharge of the pump was independent
of the liquid level in the holding tank.
The device described above permitted the application of a fairly
small but reasonably uniform dose of radioisotopes to only that portion
of the sewage going to the unit under investigation and only during that
part of the cycle that the unit was actually receiving savage. The
transfer of the isotopic solution from the holding tank to the sewage was
carried out with an externally applied pumping device operating on a
completely closed system equipped with readily accessible and easily
replaced component parts.
Secondary Sedimentation Basin
The function of secondary settling tanks and the basic principles
by which they operate are practically identical to those of primary
-35-
settling tanks, Generally, design criteria for sedimentation tanks apply
equally well to both types of basins. The principal difference between
the two units is the type of suspended solids encountered.
The effluent from trickling filters contains large quantities of
settleable organic matter, particularly when the filter is undergoing
the process of "unloading." This material is more putrescible, has a
Higher oxygen demand and is lighter and more flocculent than the sludge
from primary tanks. Generally, sedimentation of the filter effluent to
remove this material is required; consequently, secondary sedimentation
is commonly considered part of the over-all process of stabilization by
trickling filters. As a result of this, treatment criteria for this
unit are usually integrated into a single set of values for the complete
process.
The secondary sedimentation basin used in this investigation was
constructed from a section of precast concrete pipe 5 feet in diameter
and 4 feet long. The sedimentation zone has a liquid depth of 2 feet
and a free board of 6 inches, the latter being provided by the bell of
the pipe. Sludge collection is carried out in a conical shaped hopper
that accounts for the lower 2 feet of the basin. The trickling filter
effluent enters the unit through a 4-inch diameter pipe which passes
through the sedimentation zone to the center of the basin where it
empties into a 12-inch diameter down-draft tube that acts as a submerged
inlet and an influent baffle. From here the liquid rises up through
the sedimentation zone and over an annular overflow weir which is 2 feet
in diameter and concentric with the down-draft tube. The secondary
effluent is then collected in a channel behind the veir and allowed t~o
___~
leave the basin through a 4-inch diameter pipe. The unit is equipped
with a pump for sludge removal and has a theoretical detention time of
2 hours in the sedimentation zone.
En accordance with the concept that thle secondary settling tank is
part of the trickling filter process, this unit was investigated in
conjunction with the filter. Bothl units were dosed simultaneously and
sampled concurrently. The radioisotopes reaching the settling tank
during any one dose were the same ones leaving the filter during the
same dose with no additional activity being added and with no operational
changes. In this manner both mutually dependent units were investigated
without violating the unity of the process or the continuity of treatment.
Lagoons or stabilization ponds are relatively shallow basins built
for purposes of treating raw, primary or secondary wastes by storage
under conditions that favor natural biological treatment, and accompanying
bacterial reduction.' When used to treat secondary effluent, as was the
case in this investigation, they are frequently called "polishing ponds"
-- the name arising from the fact that they provide the finishing
treatment in cases where a high degree of stabilization is desired before
the effluent is discharged to the receiving stream. Used in this
capacity, they can furnish an effluent having a low BOD and coliform
bacterial content and a dissolved oxygen content often in excess of
saturation.
The unit used in this investigation (Figure 5) has an effective
length of 23 1/2 feet and an effective width of 12 feet. It is of
Fig. 5.- General view of the experimental lagoon.
masonry construction with 19 equally spaced around-the-end baffles, each
11 feet long and turned width-wise in the basin. Essentially, this
forms a channel 1 foot wide, 2 feet deep and over 200 feet long.
A Hoyno worm-type pump supplied secondary effluent to this unit
through a 1-inch diameter line, the intake of which was located just in
front of the effluent weir of the secondary sedimentation basin. By use
of a timer, the 3/4-horsepower electric motor that operated the pump
was allowed to run 1 minute out of every 3. This gave the lagoon an
average influent of 1/2 of a gallon per minute which corresponds to a
theoretical detention time of 4 3/4 days. To prevent back-siphoning
through the pump and to provide a representative influent sampling
point, an air gap was provided between the influent line and the surface
of the liquid in the influent channel of the lagoon. Control of the
liquid level-in this basin was provided by a V-notch weir at the
effluent end. This weir also functioned as the effluent sampling point.
In keeping with the role of this unit as a polishing device, it was
decided that no additional isotopes would be added to the influent of
this basin. True field conditions dictate that not only the amount but
also the physical and chemical characteristics of the isotopes in the
influent of this unit be identical to those in the effluent of the
secondary sedimentation basin.
Since the primary and secondary units used in this investigation
wFere operated on two separate lines with each line being dosed at
different times, only half of the total flow through this portion of
the pilot plant was contaminated with radioisotopes at any one time.
This gave an isotopic dilution factor of 1 to 1 when these two flows
-39-
were combined. An additional dilution of 1 to 1 was obtained when this
combined flow was added to the effluent from the other units of the
pilot plant. The effluent from the entire pilot plant was then allowed
to enter an underground conduit wh~ere-it was diluted with surface
drainage having a dry weather flow in excess of 80,000 gallons per day.
The addition of the effluent from the campus sewage treatment plant to
this stream resulted in a further dilution of 10 to 1. Thus, the
effluents from the units under investigation were diluted to less than
1 part in 80 before being discharged to a 1-acre restricted use pond.
This dilution factor plus the use of short half-life radioisotopes in
low-level amounts, prevented the development of any radiation hazards
even if there had been no removal or buffering action by the units under
investigation.
CHAPTER V
PROCEDURE
The radioactive materials used in this investigation were arranged
in eight experiments with three replications each. Six of these
experiments were concerned with individual radioisotopes, one experiment
was carried out with a mixture of two isotopes of radio-cerium and the
final experiment was conducted using mixed fission products. In order
to minimize the accumulation of activity within the treatment units,
these materials were arranged for investigation in order of increasing
physical half-life; however, the chemical characteristics of some of
the selected radionuclides precluded rigid adherence to this scheme and
minor modifications were required. The materials used, the order of
their application, their chemical form and influent concentrations are
shown in Table 2.
In order to determine the proper dosing duration, the location of
representative sampling points and an adequate sampling frequency for
each unit and to evolve a systematic sample processing procedure, an
intensified and extended sampling program was conducted during the
initial run of the first experiment. The results of this preliminary
study indicated that equilibrium of the effluent activity was reached
within 2 hours in the primary sedimentation basin, within 12 hours in
the trickling filter and secondary sedimentation basin and within 6 days
in the lagoon. On the basis of this information, a week was allowed
-40-
TABIE 2
RADIONUCLIDE DOSING DATA
a Approximate b
Experiment Radionuclide Chemical Forma Influent Concentrations
(pc/ml)
1 P-32 PO4 in dilute HC1 10 80
2 I-131 I- in basic Na2SO0 20
3 K-42 KC1 in dilute HC1 10 200
4 Ce-141,144 CeCly in dilute HC1 100
5 Fe-59 FeC13 in dilute HC1 30
6 Co-58 CoC12 in dilute HCI 45
7 Sr-89 SrC12 in dilute H01 100
8 MFP Nitrates in dilute RNO3 50
aFor dosing purposes, all radioisotopes were diluted with tap water and
the pH was adjusted to correspond to that of the original solution.
bCalculations expressing the influent concentrations in milligrams per
liter are illustrated in Appendix B.
for each of the three replications of each experiment and an additional
week of normal operation was provided between experiments in order to
substantially eliminate the preceding radioactive materials from the
treatment units. The detailed sampling procedures applied to the
individual units are outlined in the following sections.
Primary Sedimentation Basin
Immediately preceding each run, influent flow measurements were
made, influent and effluent background samples were taken and the dosing
solution was prepared and assayed. After dosing started, effluent
samples for radiological analysis were taken every 5 minutes for the
first 30 minutes then at 10-minute intervals for the next 2 1/2 hours.
Trickling Filter
Six days prior to the start of each run, six glass slides were
attached to each of the eight holding plates which were then inserted
into their respective sampling ports. Immediately preceding each run,
three of these slides from each port were removed, allowed to drain well
and the accumulated biological growth was transferred to 100-milliliter
beakers with the aid of a clean rubber policeman and 4 milliliters of
distilled water.
Liquid samples for radiological analysis were taken from the filter
influent, the 2-, 4-, and 6-foot ports and the filter effluent at time
zero and at the and of 2, 4, 8, 12, and 24 hours of isotopic dosing.
At this time, the three glass slides remaining in each of the eight
) sampling ports were removed and processed as described above. All
preliminary liquid samples were 600 milliliters in volume and in order
to eloninate any variations between individual doses, these samples
were all collected during the same dosing cycle. Proper evaluation of
the filter per se required the removal of the settleable material from
all liquid samples taken from the various ports. This was accomplished
by providing the preliminary samples with 1 hour of quiescent
sedimentation before the final samples were decanted into 100-milliliter
beakers.
Secondary Sedimentation Basin
Liquid samples for radiological analysis were taken from the
influent and effluent of this unit at time zero and after 2, 4, 8, 12,
and 24 hours of filter dosing. Representative samples of secondary
sludge for each of these times were obtained by allowing 600 milliliters
of the basin influent to undergo quiescent settling for 1 hour. At this
time, 3 milliliters of the settled material were removed with a dropper
and transferred to a 100-milliliter beaker.
The long detention time and buffering capacity of this unit permitted
a less intensified sampling frequency but required an extended sampling
duration. It was found that the action of this unit could be adequately
described by taking influent and effluent samples for radiological
analysis every 24 hours starting simultaneously with the filter dosing
and continuing for 6 days.
Sample Preparation
All liquid samples except for those from experiments 2 and 3 were
prepared for counting by the following method. After obtaining the
samples as described above, 50 milliliters of each were transferred with
a graduated cylinder to clean 100-milliliter beakers and allowed to
evaporate to dryness in a 103o C forced-air drying oven. The residue
obtained was transferred from the beakers onto planchets by successive
washing and scrubbing with a clean rubber policeman and distilled water.
'TwJo drops of 2N hydrochloric acid were added to the first of the four
wash waters. The residue on each planchet was then evaporated to
dryness under heat lamps.
All sludge and slime samples except for those from Experiment 2
were prepared for counting by transferring the samples directly to dried
and tared planchets and evaporating them to dryness under heat lamps.
After counting, these planchets were stored in a desiccator for at least
12 hours before the final weights were taken.
The instability of iodine in acid or -weakly basic solutions at
elevated temperatures required modification of the sample drying
procedure. For this experiment, all liquid samples were made basic to
phenophtalein with 2N sodium hydroxide before being placed in the 103o C
oven. After drying, the residues were transferred from thle beakers to
the planchets by normal washing procedures, omitting the 2N acid in the
first wash. The planchets were then allowed to evaporate to dryness in
a 700 C oven before counting. The sludge and slime samples for this
experiment were collected in the previously described manner, made basic
by the addition of two drops of 1/2DN sodium hydroxide and transferred
to the pre-weighed planchets. They were then dried at 700 C and counted
by the normal procedure..
The short half-life of potassium-42 (Experiment 3) necessitated the
elimination of the lengthy evaporation time required by the liquid
samples before their residue could be transferred. It was found that
two half-lives could be saved between the sampling and counting stages
by transferring exactly 4 milliliters of each sample directly to their
respective planchets and evaporating them under the heat lamps. Even.
though low count rates were obtained with these small samples, the
reproducibility obtained by this method was as good as that which would
have been obtained by the normal method and only 1/4 the quantity of
isotopes was required.
-45-
Counting Technique
For Experiment 1 all samples were placed on copper planchets having
a sample deposit area of 8 square centimeters and subjected to gross
counting in a Nuclear-Chicago automatic counting system having an
efficiency of 35 per cent for thallium-204. This counting sequence was
composed of an end window proportional counter, a Model C-110 B sample
changer and a Model 186 scaler. The counter was operated at 2150 volts
and supplied with "PR" counting gas under slight pressure. For the most
part, this system was operated on a pre-set count mode with the counting
times being recorded on a Model C-111 B printing timer.
Prior to Experiment 2, a Baird-Atomic automatic counting system
became operational and since it allowed considerable flexibility in
operation, it was used for this and all subsequent experiments. This
system, which had an efficiency of 40 per cent for thallium-204,
consisted of a Model A-227 gas flow end window proportional counter,
a Model 750 sample changer and a Model 132 scaler. All samples were
prepared on stainless steel planchets 5 centimeters in diameter and
subjected to gross counting at 2050 volts using "PR" counting gas
supplied under low pressure. This system was also operated on a pre-set
count basis and the counting times were recorded on a Clary print-out
timer.
In order to eliminate as much counting variability as possible,
all samples taken from the same treatment unit and having related
sampling times were grouped into sets and counted during the same
counting sequence. All samples were counted at least twice with a
background determination included in each counting run. For purposes
of assessing the normality of operation of the instrumentation, no less
than two uranium standards were included in each counting operation.
Since all samples from the same experiment were placed on the same
type and size planchet and counted on the same instrument, no corrections
for geometry or backscatter were necessary. The use of a systematic
handling procedure and relative counting techniques eliminated the need
for all counting corrections except background and decay, the latter
being required for Experiment 3 only.
The activity of all liquid samples was reported in counts per
minute per 50 milliliters with the exception of the corresponding data
Erom Experiment 3 which were based on a sample volume of 4 milliliters.
To gain maximan reproducibility and minimum variability, the activity
of all sludge and slime samples was reported in counts per minute per
milligrarm of dry solids.
Both counting systems could be operated automatically, which was
the method of choice. however, the activity level of various samples
differed widely, thus the attainment of ideal counting statistics would
require mannal operation in cases where fast counts would introduce time
errors and where long counts would not be compatible with efficient use
of the equipment. As a compromise between these extremes, the Nuclear-
Chicago instrument was operated so as to obtain minimum counting times
of 30 minutes for background samples and minimum total counts of 4000
for faster samples. In the latter case, no counting time of less than
5 minutes was recorded.
The Baird-Atomic system provided greater flexibility of operation
in that it allowed background samples to be counted for total counts of
900 while the faster samples were counted for 9000 counts. This was
accomplished by an auxiliary circuit which stopped the count at 900 if
the activity of the sample w~as less than 150 counts per minute. Here
again, the minimum counting time for background samples was 30 minutes
while the faster samples were counted for at least 5 minutes.
Counting statistics applicable to .the above counting conditions can
be found in Appendix C.
Chemical and Biochemical Sampling
In order to evaluate the major parameters of treatment plant
performance and to illustrate that the plant employed in this investigation
was indeed operating under normal field conditions and attaining typical
treatment efficiencies, the two major units -- the primary sedimentation
basin and the trickling filter -- were subjected to a chemical and
biochemical sampling program at the end of each run.
The sampling program applied to the primary settling tank was
carried out by taking 1-hour composite samples from the influent and
effluent of the basin. These samples, which were 1 gallon in volume,
were analyzed for BOD and suspended solids.
The trickling filter was evaluated by obtaining samples from the
influent, all ports and the effluent. The samples were composite over
at least three dosing cycles and were. 1 gallon in volume. In keeping
with the concept that secondary sedimentation is an integral part of
the trickling filter process, all preliminary samples were allowed
1 hour quiescent sedimentation before the final samples were taken.
These samples were then analyzed for BOD, nitrates, and total nitrogen.
-48-
All chemical and biochemical analyses were conducted in accordance
with the procedures outlined in Standard Methods for the Exarmination of
Water and Wastewater (53) .
CHAPTER VI
DISCUSSION OF OBSERVATIONS
General Considerations
In this study, relative counting techniques were utilized and a
comparative analysis of the data was employed. Consequently, it was
not necessary to correct the observed counts to absolute units of
radioactivity. Since all radioactive samples from the same experiment
were counted under virtually identical conditions in the same instrument,
the relation between the observed activity and the true disintegrations
was essentially constant. Application of an appropriate correction
factor would have changed the absolute values of these data but would
not have altered the relative magnitude of the established relationships.
The chemical forms and influent concentrations of the radioisotopes
used in each experiment are tabulated in Table 2. In preparing these
materials for dosing, the pH of each solution was adjusted so as to
maintain the solubility of the radionuclides. Upon dosing, however,
this solution was diluted into sewage having an average pH of 7.8. The
characteristics of these materials in dilute solutions having slightly
basic pH values indicate that all radioisotopes used, except cerium,
iron, and cobalt which are known colloid formers, remained in their
ionic form.
All experimental studies conducted during this investigation were
undertaken at levels of activity that could be reasonably expected under
-49-
actual field conditions. Even though relatively high counting rates were
often produced, the concentrations of radioactive materials were still
very law. This is illustrated in Appendix B which gives the influent
concentrations (in ag/1) of the radionuclides used in each experiment.
Examination of these values indicates that the addition of radioactive
materials in the concentrations used did not appreciably alter the
nature or amount of soluble or insoluble solids present in the waste.
Removal by Primary Sedimentation
Tabulated data from the series of studies concerning this unit are
contained in Appendix D. inspection of these data permits two conclusions
to be drawn. The first is that after the effluent activity approached
equilibrium conditions, very little removal of soluble or colloidal
radionuclides was accomplished by this treatment process. The steady
state removal values varied from near 0 to 15 per cent with most falling
between 5 and 10 per cent. The highest values recorded were obtained
in the potassium-42 experiment but it is believed that this apparent
increase in treatment efficiency resulted from the physical decay of
this short half-life isotope rather than from actual removal by the unit.
The second conclusion is that all removal patterns were quite
similar and, within the ranges investigated, seemed to be independent of
the amount as well as the chemical and physical properties of the
radionuclides utilized. Due to these similarities, the removal patterns
from all experiments were averaged and the results are presented
graphically in Figure 6. Nbtle the particular shape of this curve is a
function of the design and operation of the basin investigated, it is
I I IO O l l O O l i
C
O
O *-
~o
.0
u
*00 C
08 r
"c .-
0
o
la
characteristic of the effluent patterns from this type of unit. In
general, this figure indicates that after approximately 2 hours of
continuous isotopic dosing, the effluent activity approached equilibrium
conditions and that once these conditions were attained, the rate of
removal stabilized at approximately 9 per cent.
The principal action occurring in treatment units of this general
type is the physical removal of settleable solids by gravitational
sedimentation. Since the nature of the radioactive materials used in
this investigation did not permit them to be readily removed in this
manner, the mechanism of removal appears to have been the sorption of
the radionuclides by the settleable solids inherent in the waste. The
operational characteristics of this treatment process and the nature
and amount of settleable solids normally present in a waste of this type,
indicate that the efficiency of this proposed mechanism would be low
for colloidal and dissolved radioisotopes. This is substantiated by
the observed data.
Removal by Trickling. Filtration
Basic data and graphs concerning the experimental studies conducted
on the trickling filtration and secondary sedimentation processes are
contained in Appendix E. The various treatment efficiencies attained
by these units operating under equilibrium conditions are summarized
in Table 3. In studying Figures 16 through 23 and 26 through 29, it
should be remembered that the observed activities (in c/m/mg) were
dependent, to a large extent, on the influent concentration as well as
the physical half-life of the radioactive material investigated.
Average Percentage Average Percentage
Radionuclide Removal by Various Removal in Secondary
Depths of Filter Mledium Sedimentation Basin
2' 4' 6' 8'
K-42 15 35 45 49 27
Sr-89 24 27 37 42 23
I-131 26 42 53 61 3
P-32 32 36 43 46 0.4
MFP 40 48 61 63 40
Fe-59 46 SS 72 65 70
Co-58 48 66 80 81 64
Ce-141, 144 57 63 78 81 48
TABLE 3
SUMMARY OF REMOVAL EFFICIENCIES ACHIEVED BY
TRICKLING FILTRATION AND SECONDARY SEDIMENTATION
UNDER EQUILIBRIUM CONDITIONS
Since these conditions varied from one experiment to another, these figures
should be used only in making comparisons and observing general trends.
The trickling filter data represented graphically in Figures 8
through 15 permit several general observations to be made. One of the
most significant of these is that all radioactive materials investigated
experienced some degree of removal by this unit. Figures 16 through 23
not only substantiate -the fact that this removal did occur but also
indicate that the observed uptake resulted from the concentration of
these materials by the zoogleal slimes present throughout the filter.
Considering the presently accepted theory of trickling filter operation,
the extent of the slime-liquid interface available for transfer within
this unit and the relatively low concentration of radioactive materials
used, it is understandable how such a removal could be obtained.
Another general trend recognizable in Figures 8 through 15 is that
most removal patterns exhibited a high initial uptake followed by a
somewhat asymptotic approach to equilibrium conditions. This is a
fairly common characteristic of most chemical and biological systems
and results from the gradual satisfaction of a comparatively high
initial uptake capacity being superiuposed on a steady rate of removal.
A noted exception to this general behavior occurred during the
phosphorus-32 experiment and was observed to coincide with a noticeable
sloughing caused by a sharp, early morning rise in both the organic
loading rate and the ambient temperature.
All filter uptake patterns indicate that the various rates of
removal reached their equilibrium values approximately 12 hours (96
doses) after isotopic dosing started. This conclusion is supported by
-55-
the action occurring in the secondary sedimentation basin. Figures 24
through 29 show that, in general, the secondary sedimentation removal
patterns and the activity of the secondary sludge, both of which depend
on the action occurring in the filter, had attained their steady state
conditions within 12 hours. These observations seem to indicate that the
achievement of equilibrium conditions was a function more of the number
of doses applied than of the physical and chemical characteristics of
the radionuclides investigated.
The filter uptake patterns also indicate that the rate of removal
with respect to depth generally decreased throughout the filter. This
is illustrated in Table 3 which summarizes the various removal
efficiencies observed after 24 hours of dosing. This table shows that
in all experimental studies undertaken, the highest removals per increment
of depth were obtained in the first 2 feet of medium and, in most
experiments, this portion of the filter accomplished over half of the
uptake attained by the entire unit. The middle 4 feet gave intermediate
treatment while no appreciable removal was realized by the lower 2 feet
of the filter bed. The activity of the filter slimes, shown graphically
.in Figures 16 through 23, express general agreement with this uptake
pattern .
This somewhat expOneHtial rate Of removal is understandable since
the uptake of soluble and colloidal radionuclides by this treatment
process is dependent on the sorptive capacity of the zoogleal slimes
present at the various depths in the filter and the concentration of
radioactive materials available for removal at each level. Both of these
factors were observed to decrease with increasing depth of filter medium.
A careful study of Table 3 indicates that by ranking the various
materials investigated according to their corresponding degrees of
removal, it is possible to distinguish two definite groups, separated
by mixed fission products (MFP). The first group, which contains
potassiumo-42, strontium-89, iodine-131 and phosphorus-32, experienced
an1 uptake of approximately 50 per cent by an 8-foot filter. The second
group, which contains tron-59, cobalt-58, and cerium-141, 144,
experienced a comparable removal in the first 2 feet of medium and
almost twice this value in the full 8-foot depth. Mixed fission
products, which contain representative members of both groups, gave
intermediate treatment. The treatment efficiencies obtained by the
secondary sedimentation basin not only confirm this general division
but also provide an indication of the nature and effectiveness of the
action occurring in the filter.
Correlation of the various removal patterns and treatment
efficiencies obtained in both~ the trickling filter and secondary
sedimentation basin with the physical and chemical characteristics of
the radioactive materials investigated, indicates that the mechanisms
of uptake in the filter can be classified into three general categories.
The first of these concerns the radionuclides that are significant in
cell metabolism. In this case, the effective mechanism of removal
appears to be the absorption of the radioactive materials by the
microorganisms present in the sougleal slime layer. The radionuclides
in this category have to compete with their stable counterparts in the
removal process; therefore, the uptake efficiency is dependent on the
concentrations of stable isotopes present in the waste. Since sewage
-57-
normally contains comparatively high concentrations of the elements
essential in cell metabolism, the isotopic dilution factor of this
waste is relatively high. Consequently, the potential uptake capacity
of metabolically significant radionuclides by the trickling filter
process is somewhat low. This is illustrated by the phosphorus-32
uptake data summarized in Table 3. This table shows that in the presence
of 5 to 7 milligrams per liter of stable orthophosphates, the experimental
filter used in this investigation accomplished a relatively low uptake
of 46 per cent.
The low removal of phosphorus-32 obtained in the secondary
sedimentation basin indicates that as the filter slimes gradually
sloughed off (due to continuous replacement procedures) and passed
from the filter, the radiophosphorus which had undergone preliminary
removal by the viable slimes in the unit was re-entrained in the waste
stream and was no longer associated with settleable solids. This leads
to the general observation that the over-all process of trickling
filtration and secondary sedimentation was relatively ineffective in
removing this radionuclide from sewage.
The second category of uptake mechanisms concerns the radioactive
materials that are present in the vaste in their soluble form but are
not significant in cell metabolic processes. In this case the uptake
mechanism appears to be that of ion exchange. The radionuclides subject
to removal in this manner must not only compete with their stable
counterparts but also with all other elements that have similar ionic
properties or chemical behavior. This indicates that the isotopic and
chemical dilution resulting from the wide range of stable materials
____ __
-58-
normally present in sewage, would limit the efficiency of this uptake
mechanism. This is substantiated by the potassium-42, strantium-89,
and iodine-131 data shown in Table 3. The relatively low removals
indicated in this table are understandable since these materials had
to compete with their chemically similar counterparts -- sodium, calcium,
and chlorine -- present in the sewage. The low removal efficiencies
obtained by secondary sedimentation indicate a re-entrainment similar
to that explained above and lead to the same general conclusion
concerning the ability of this treatment sequence to effectively remove
these radionuclides from sewage.
The third general category of uptake mechanisms concerns the
non-metabolically significant radionuclides that are present in the
waste in their colloidal form. Here, the indicated modes of removal
are adsorption and physical trapping of these materials on and in the
zoogleal slime layer. According to the presently accepted theory of
trickling filter operation, this uptake mechanism should be relatively
effective in removing colloidal matter from the waste stream. This is
supported by the iron-59, cobalt-58, and cerium-141, 144 data summaarized
in Table 3. As pointed out previously, these materials experienced a
higher uptake than that indicated for the other radionuclides investigated.
The comparatively high removal obtained by secondary sedimentation
indicates that this uptake mechanism was effective in removing these
colloidal radionuclides from the waste stream and associating them with
the filter solids that eventually reached the secondary sedimentation
basin in a settleable form.
Removal by Lagooning (Polishingi Pond)
The tabulated data concerning this series of investigations are
contained in Appendix F. Pertinent data derived from the influent and
effluent activity patterns shown in Figures 30 through 36 are summarized
in Table 4. In determining the various percentages of removal shown in
this tables, the total activity going into the basin over each 20-day
study period was compared to the total activity leaving the basin during
the same period. Since these activities were proportional to the areas
under their respective influent and effluent curves, the indicated
removal values were obtained by determining and comparing the appropriate
areas.
TABLE 4
SUMMARY OF REMOVAL EFFICIENCIES AND BUFFERING
FACTORS OBTAINED BY LAG00NING
Radionuclide Removal Efficiency Buffering Factora
(Percentage)
I-131 0 3.1
P-32 54 6.6
Co-58 55 3.3
HFP 58 7.0
Sr-89 .69 9.7
Fe-59 86 13.
Ce-141, 144 93 15.
aRatio of peak influent activity to peak effluent activity, averaged
over all three dosing sequences.
-60-
Inspection of Table 4 and Figurea 30 through 36 indicates that the
relatively long detention time, the intimate algal-bacterial contact and
the high dilution factor provided by this treatment process was effective
in delaying, buffering and, in most cases, appreciably removing low-level
"slugs" of the radionuclides investigated. The evident correlation of
the buffering factors with the removal efficiencies points out that the
ability of this unit to buffer "slugs" of radioactivity was not only
dependent on the design and operation of the basin but also on the
extent of the removal obtained within the unit. As indicated in the
above table, the observed buffering factors varied from a minimum of 3.1
for I-131 to a maximum of 15 for Ce-141, 144. The lower value, which
was obtained under the conditions of zero removal, indicates the
dilution factor of the basin.
The various influent and effluent activities observed represent
the total amount of radioactivity entering and leaving the basin
regardless of chemical or physical form or biological association;
therefore, the various removal efficiencies indicated in Table 4
represent the actual removal occurring within the unit. Since the
half-lives of the indicated radionuclides were relatively long compared
to the observed median detention time (2 days) of the basin, radioactive
decay had no appreciable effect on these removal, efficiencies. These
considerations indicate that the observed removals resulted from the
deposition of the radionuclides within the unit. In view of this, the
indicated mechanisms of removal are precipitation by chemical, physical,
and biological means and ion exchange reactions involving the radio-
nuclides entrained in the waste stream and the stable materials retained
in the basin.
-61-
The effectiveness of these mechanisms operating under the conditions
of prolonged detention and intensive biological contact, is illustrated
by the various removal efficiencies obtained. Except in the case of
I-131, which exhibited a positive aversion to removal by these processes,
all radionuclides investigated, especially colloidal cerium and iron,
experienced significant removal.
Chemical and Biochemical Analyses
Investigational data concerning the chemical and biochemical
parameters of treatment plant performance are tabulated in Appendix G.
The trickling filter data summarized in Tables 54, 56, and 58 are
presented graphically in Figure 7.
Inspection of Table 52 indicates that during the course of this
investigation, the pilot plant influent contained, on the average,
135 milligrams per liter of suspended solids and had an average BOD
equal to 170 milligrams per liter. The pronary sedimentation data
indicate that the unit used in this investigation accomplished an
average BOD reduction of 28 per cent and an average reduction in
suspended solids of 41 per cent. Both of these values fall within
reasonable limits of operation for basins of this type.
Tables 53 through 58 show that the filter utilized in this study
achieved average reductions in BOD and total nitrogen of 89 and 84 per
cent, respectively, while effecting an average nitrification of 67 per
cent. The various curves in Figure 7 indicate that the major portion
of the observed treatment occurred within the first 5 feet of filter
medium. These observations are within the ranges of normal operation
Q
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o~m~~o~n-t~~u
-63-
and are in general agreement with the results of prior investigations
conducted on this unit by Hagan (54), Vitaret (55), and Priede (56).
En general, the primary sedimentation basin and trickling filter
employed in this investigation were observed to be operating under
normal field conditions and attaining typical treatment efficiencies
throughout the course of the experimental work. The presence of
radioactive materials in the waste stream in the amounts used in this
investigation had. no apparent effects of these treatment processes.
~
CHAPTER VII
SUMMARY AND CONCLUSIONS
This investigation was concerned with evaluating the removal of
low-level radionuclides from waste water by a complete sewage treatment
plant operating under actual field conditions. In making this evaluation,
a pilot size treatment plant employing primary sedimentation, trickling
filtration, and lagooning was utilized. These treatment processes were
subjected-to a series of eight experiments involving phosphorus-32,
iodine-131, potassium-42, cerium-141, 144, iron-59, cobalt-58,
strontium-89, and mixed fission products.
Based on the results of the various radiological, chemical and
biochemical determinations made during these experiments, the following
conclusions have been drawn.:
1. Primary sedimentation is relatively ineffective as a process for
removing colloidal and dissolved radionuclides from sewage. After
equilibrium of the effluent activity is established, removals of
less than 10 per cent can be expected.
2. The effectiveness of the trickling filtration process in the
treatment of low-level wastes is limited to its ability to remove
the radioactive components from the main vaste streak and to
concentrate these materials in a relatively small volume of solid
natter which, after passing from the filter, can be removed by
sedimentation. Even though significant removal may occur within
the unit, the uptake mechanism may become reversible and the materials
preliminarily removed in the filter may become re-entrained La
essentially their original form. Consequently, the treatment
efficiency of the over-all process of trickling filtration is
reflected in the removal accomplished by secondary sedimentation.
The approximate over-all removals that can be expected under the
conditions of normal plant operation are: 60 to 70 per cent for
iron-59 and cobalt-5i8; 40 to 50 per cent for cerium-141, 144 and
mized fission products; approximately 25 per cent for potassium-42
and strontium-89; and less than 5 per cent for iodine-131 and
phosphorus-32.
3. -The uptake of low-level radionuclides within a filter results from
the concentration of these materials by the soogleal slimes present
throughout the unit. The rate of removal with respect to time is
comparatively high during the initial doses but gradually decreases
to equilibrium conditions. The attairnment of stable uptake
conditions is more a function of the number of doses applied than
of the characteristics of the radioactive materials in the waste.
Plants employing shorter dosing cycles than 7 minutes can expect to
achieve equilibrium conditions in less than 12 hours (96 doses).
The rate of removal with respect to depth decreases somewhat
exponentially with increasing depth of medium. The optimum filter
depth' is 6 feet.
4. The concentration of radioactive materials by the zoogleal slimes
in a trickling filter results fran the action of three removal
mechanisms, (a) absorption of~the radionruclides by the microbiota
-66-
in the slime layer, (b) ion exchange reactions involving the radio-
isotopes in the waste stream and the stable elements associated with
the filter solids, (c) adsorption and physical trapping of the'
radioactive materials on and in the zoogleal slime layer. The
effectiveness of these uptake mechanisms is a function of the
chemical and physical properties of the radionuclides and the
concentration of their stable counterparts and chemically similar
materials in the waste. As a result of the isotopic and chemical
dilution provided by sewage, the mechanisms of absorption and ion
exchange are relatively ineffective and highly reversible; consequently
soluble radionnelides are not effectively removed. Colloidal
radionuclides, being more amenable to removal by these mechanisms
especially by adsorption and physical trapping, are efficiently and
effectively removed.
5. The comparatively long detention time and intimate algal-bacterial
contact provided by lagoons are effective in diluting, delaying
and, in most cases, substantially removing "slugs" of low-level
radioactive materials. Basins employing effective detention times
of 2 to 3 days can azpect to attain the following removals:
90 per cent for cerium-141, 144 and iron-S9; 70 per cent for
strontium-89; 50 to 60 per cent for phosphorus-32, cabalt-58 and
mixed fission products; and less than 1 per cent for iodine-131.
6, The mechanisms effective in the removal of radioactive materials
by lagooning are, (a) precipitation by chemical, physical, and
biological means, (b) ion exchange reactions involving the .
-67-
suspended radionuclides and the stable materials retained in the
basin. These mechanisms are most effective in removing trivalent
materials in their colloidal form and divalent elements biologically
significant in trace amounts.
7. Savage treatment plants operating under normal field conditions are
able to receive and dispose of low-level radioactive wastes with no
apparent decrease in treatment efficiency or changes in operational
procedure required.
APPENDICES
APPENDIX A
CHEMICAL ANALYSIS OF LPMESTONE FILTER MEDIUM
Percentage by Weilhta
0.14 i 0.03
1.52 i 0.14
trace (<0.01)
0.35 i 0.04
3.14 i 0.12
42.62 i 0.41
8-48 i 0.22
36.42 i 0.14
1.88 i 0.10
1.78 + 0.04
Constituent
I120 (103o C)
CO2 (6000 C)
PO
Mg +
Combined Oxtides
Ca
Silica
CO3
SO
Fe
average results of three stones picked at random.
-69-
APPENDIXB
CALCULATION OF CONCENTRATION OF RADIOACTIVE MATERIAL
PRESENT AT SELECTED LEVELS OF RADIDACTIVITI
The concentrations of radioactive materials present in low-level
wastes are usually very small. When the level of activity in picocuries
per milliliter is known for a particular radioisotope, its concentration
per milliliter may be calculated using the following relationship:
2.2 x A
where N is the number of unstable atoms present per milliliter, A is the
level of activity in picocuries per milliliter and A is the disinte-
gration constant obtained by dividing 0.693 by the appropriate half-life
T, expressed in minutes.
To express this concentration in terms of milligramns per liter, N
anst be multiplied by the proper atomic weight in grams, divided by
Avogadro's number then mu~ltiplied by -106. Arrangement of these
calculations into a single equation yields:
Con. (g/1 =A(pgaml) x 2.2 x T~min) x N~W(fms) x 106
0.693 x 6.023 x 1023(atoms/mole)
Indicated calculations for the activity levels used in this
investigation have been made and the results are tabulated below.
-71-
Activity
(pc/ml)
10 80
20
10 -200
100
30
45
100
50
Concentration
(mgi/1)
3.5 x 10-11 2.8 x 10-9
1.6 x 10-1
1.7 x 10-1 3.3 x 10-1
2.8 x 10
6.0 x 10-1
1.4 x 10-
3.6 x 10-
Radionuclide
P-32
I-131
K-42
Ge-141, 144
Fe-59
Co-58
Sr-89
MPP
APPENDIX C
STATISTICS OF CDUNTING RADIOACTIVE. SAMPLES
Data obtained from most counting processes are known to follow a
Poisson distribution, an outstanding property of which is that its
standard deviation, 6. ,is the square root of its mean, /y
Unfortunately, in most experimental work, the true population mean is
an unknown quantity. In such cases, the best estimate of 70 can be
obtained by making a number of observations, N, and calculating their
mean 5. The best estimate of r- symbolized by drN), can then be
obtained by taking the square root of N.
However, in counting radioactive samples, it is not the standard
deviation of the cotal count that is of concern but rather the standard
deviation of the count rate, R', where
In this expression, N represents the observed count recorded in time t.
Since the accuracy of any count rate increases with increasing time of
observation, the desired standard deviation must not only be a function
of the observed count: rate but also a function of the time over which
this rate was determined. Applying the usual statistical methods for
propagation of error to the Poisson distribution:
In actual practice, all counting instruments have a background
counting rate, B, which contributes to the gross counting rate, R .
The sample counting rate, R, can be calculated as follows:
R =Ro- B
Applying the statistical methods for propagation of error yields:
Ro B
q-(R) =(t 2
where tl and t2 are the times over which gross and background counting
rates were determined.
Using gross counts of 4,000 and 9,000 observed over a minimum
counting time of 5 minutes and a background of 15 counts per minute
observed over a minimum time of 30 minutes, the following standard
deviations and associated counting errors may be calculated.
a-(R) =.(0 12.6 c/m e = 1.96 x 12.6 = 24.7 c/m
p-(R) = (1 = 19.0 c/m e = 1.96 x 19.0 = 37.2 c/m
TABULATED DATA -- REMoVAL OF SELECTED
RADIONUCLEDES BY PRIMARY SEDIMENTATION
TABLE 5
REMOVAL OF P-32 BY PRIMARY SEDIMENTATION
Time Run la Run 2b Run 3c A~verage
in Eff. % Eff. X Eff. %
Minutes c/m Removal c/m Removal -c/m Removal Removal
0 3.47 -- 2.49 -- 6.80 -
5 1.57 99.79 2.41 99.94 6.35 99.69 99.8
10 2.75 99.64 7.52 99.81 7.13 99.65 99.7
15 6.26 99.18 266.0 93.41 299.5 85.18 92.6
20 245.6 67.86 836.3 79.27 691.7 65,78 71.0
25 346.6 54.64 1621. `59.83 985.5 51,24 55.2
30 428.8 43.89 2027. 49.78 851.6 57.87 50.5
40 518.0 32.21 2280. 43.49 1483. 26.61 34.0
50 568.6 25.59 2445. 39.42 1394. 31.04 32.0
60 601.4 21.29 2579. 36.20 1124. 44.38 34.0
70 597.6 21.79 2706. 32.97 1606. 20.54 25.1
80 651.27 19.48 2847. 29.45 1628. 19.48 22.8
90 631.8 17.32 3177. 21.28 1560. 22.84 20.5
100 699.8 8.42 -- -- 1633. 19.21 13.8
110 -- -- -- -- 1782. 11.82 11.8
120 687.0 10.09 -- -- 1750. 13.40 11.8
130 707.6 7.40 -- -- 1857. 8.12 7.76
140 684.6 10.41 -- -- .1893. 6.34 8.38
150 -- -- -- -- 1864. 7.77 7.77
'160 -- -- -- -- 1809. 10.51 10.5
170 -- -- -- -- 1857. 8.12 8.12
180 -- -- -- -- 1816. 10.17 10.2
alnfluent activity was 764.1 c/m.
blnfluent activity was 4035 c/m.
Cfnfluent activity was 2021 c/m.
APPENDIX D
-74-
Time Run La Run 2b un 3c Average
in Eff. % Eff. % Eff. % %
Minutes c/m Removal -c/m Removal c/m Removal Removal
0 1.11 -- 1.43 -- 1.75 -
5 1.17 99.62 1.56 99.57 1.83 99.45 99.6
10 2.25 99.27 5.25 98.56 9.40 97.16 98.3
15 21.77 92.96 71.82 80.26 73.15 77.93 83.7
20 59.29 80.83 85.30 76.55 103.9 68.66 75.3
25 80.36 74.01 115.4 68.28 118.7 64.19 68.8
30 193.0 37.S7 192.2 47.17 143.0 56.85 47.2
40 183.2 40.75 229.7 36.84 185.3 44.11 40.6
50 196.8 36.36 278.4 23.47 212.4 35.93 31.9
60 199.1 35.60 303.1 16.67 223.3 32.63 28.3
70 216.3 30 .05 316.9 12.89 247,8 25.25 22.7
80 252.1 18.49 278.4 23.47 239.8 27.66 23.2
90 231.3 25.17 287.4 20.98 235.4 28.99 25.0
100 249.1 19.46 320.2 11.98 243.5 26.54' 19.3
110 261.6 15.41 323.5 11.06 268.0 19.15 15.2
120 250.0 19.16 308.4 15.23 263.8 20.41 18.3
130 273.3 11.63 308.0 15.32 287.4 13.31 '13.4
140 278.0 10.10 338.1 7.05 294.0 11.31 9.79
150 273.7 11.49 331.7 8.83 301.4 9.07 9.80
160 269.8 12.76 325.8 10.43 297.5 10.25 11.2
170 279.1 9.75. 312.2 14.17 297.9 10.13 11.4
180 272.5 11.86 324.8 10.70 287.8 13.19 11.9
-75-
TABLE 6
REMOVAL OF I-131 BY PRIMARY SEDPMENTATION
alfluent activity was 309.2 c/m.
blnfluent activity was 363.8.c/m.
cInfluent activity was 331.5 c/m.
Time Run 1 Run 2a Run 3b Average
in Eff. % Eff. Eff. Z Z
Kinutes c/m Removal c/m Removal c/m Removal Removal
0 -- -- 0.69 -- 0.00 ---
5 -- -- 0.77 97.40 0.00 100.0 98.7
10 -- -- 1.52 94.87 0.00 100.0 97.4
15 -- -- 3.23 89.10 7.92 87.85 88.5
20 -- -- 8.21 72.29 15.49 76.24 74.3
25 -- -- -- -- 23.11 64.55 64.6
30 -- -- 13.55 54.27 23.94 63.28 58.5
40 -- -- 14.73 50.29 25.09 61.51 55.9
50 -- -- 17.97 39.35 36.06 44.68 42.0
60 -- -- 18.73 36.79 33.89 48.01 42.4
70 -- -- 19.27 34.96 41.36 36.55 35.8
80 -- -- 17.32 41.55 45.73 29.85 35.7
90 -- -- 20.18 31.89 49.02 24.80 28.4
100 -- -- 21.22 28.38 47.30 27.44 27.9
110 -- -- 19.88 32.91 48.61 25.43 29.2
120 -- -- 21.12 28.72 48.15 26.14 27.4
130 -- -- 25.24 14.82 52.90 18.85 16.8
140 -- -- 23.75 19.84 57.93 11.14 15.5
150 -- -- 26.08 11.98 55.09 15.49 13.7
160 -- -- 25.63 13.50 59.02 9.47 11.5
170 -- -- 25.96 12.39 59.87 8.16 10.3
180 -- -- 25.58 13.67 57.81 11.32 12.5
a~nfluent activity was 29.63 c/m.
blnfluent activity was 65.19 c/m.
TABLE 7
REMDVAL OF K-42 BY PRIMARY SEDIMENTATION
TABLE 8
REMIDVAL. OF Ce-141, 144 BY PRIMARY SEDPIENTATION
51m Rn a Rn b un 3c Average
in Eff. % Eff. % Eff. I %
H~inutes c/m Removal c/m Removal c/m Removal Removal
0 5.94 -- 1.87 -- 6.94 --
5 3.95 99.90 2.08 99.96 4.07 99.92 99.9
10 32.79 99.15 3.63 99.93 8.72 99.82 99.6
15 797.4 79.26 413.7 91.68 163.7 96.69 89.2
20 1783. 53.63 1240. 75.06 1205. 75.63 68.1
25 2192. 42.98 1597. 67.89 2566. 48.09 53.0
30 2294. 40.33 2603. 47.66 2967. 39.97 42.6
40 2277. 40.79 3236. 34.94 2808. 43.19 39 .6
50 2464. 35.91 3587. 27.88 2448. 30.23 31.3
60 2665. 30.68 3370. 32.24 3332. 32.58 31.8
70 2618. 31.89 3645. 26.71 3345. 32.32 30.3
80 3017. 21.53 3784. 23.91 3690. 25.33 23.6
90 2939. 23.56 4023. 19.12 3752. 24.08 22.2
100 2817. 26.74 4464. 10.24 3952. 20.05 19.0
110 3247. 15.54 4532. 8.88 3817. 22.78 15.7
120 3187. 17.12 4356. 12.42 3768. 23.76 17.8
130 3516. 8.55 4464. 10.24 4158. 15.87 11.6
140 3475. 9.62 4335. 12.85 4187. 15.29 12.6
150 3379, 12.11 4005. 19.48 4293. 13.14 14.9
160 3435. 10.66 4212. 15.31 4278. 13.44 13.1
170 3357. 12,68 4293. 13.69 4399. 11.01 12.5
180 3475. 9.62 4789. 4.52 4272. 13.56 9.23
alnfluent activity was 3845 c/m.
blnfluent activity was 4974 c/m.
clnfluent activity was 4943 c/m.
Time Run 11 Run 2b Run 3C Average
in Eff. %1 Eff. % Eff. 7. 1
Minutes c/m Removal c/m Removal c/m Removal Removal
0 6.92 -- 3.19 -- 1.22 -- -
5 10.03 98.27 4.40 99.04 0.63 99.90 99.1
10 23.89 95.88 2.75 99.40 2.70 99.56 98.3
15 195.0 66.38 43.46 90.55 28.93 93.65 83.5
20 248.0 57.25 114.0 75.22 113.0 81.56 71.3
25 288.5 50.26 177.5 61.41 256.5 58.13 56.6
30 243.3 40,81 213.0 53.69 302.2 50.68 48.4
40 255.3 38.75 272.2 40.81 378.6 38.21 39.3
50 428.2 26.18 322.8 29.80 382.2 37.62 31.2
60 415.3 28.39 301.9 34.35 415.6 32.16 31.6
70 437.2 24.61 351.2 23.63 401.5 34.47 27.6
80 422.0 27.27 375.0 18.44 472.2 22.92 22.9
90 460.2 20.65 414.3 9.92 512.3 16.38 15.7
100 454.8 21.58 445.5 3.12 559.8 8.63 11.1
110 515.4 11.15 413.7 10.04 549.1 10.38 10.5
120 532.0 8.27 427.0 7.16 526.0 14.15 9.86
130 493.9 14.85 403.5 12.25 591.1 3.51 9.87
140 553.3 4.60 401.6 12.67 543.4 11.31 9.53
150 522.9 9.84 427.5 7.04 588.5 3.94 6.94
160 550.5 5.09 403.5 12.25 563.1 8.09 8.48
170 521.4 10.11 395.8 13.94 549.6 10.30 11.4
180 525.7 9.36 421.7 8.29 530.1 13.48 10.4
TABLE 9
RENGVALL OF Fe-59 BT PRPIARY SEDIMENTATION
aInfluent
blnfluent
Clnfluent
activity was 580.0 c/m.
activity was 459.9 c/m.
activity was 612.6 c/m.
Time Run la Run 26 Run 3c Average
in Eiff, r Eff. % Eff. Z %.
Minutes c/m Removal c/m Removal c/m Removal Removal
0 2.65 -- 2.44 -- 1.36 ---
5 2.61 99.15 1.75 99.33 2.58 99.26 99.2
10 2.82 99.08 5.18 98.01 1.59 99.54 98.9
15 38.24 87.51 29.67 88.61 8.00 97.71 91.3
20 88.43 71.13 77.22 70.37 73.21 79.00 73.5
25 125.3 59.10 105.5 59.52 132.4 62.01 60.2
30 138.5 54.76 145.9 44.01 173.8 50.16 49.6
40 133.8 56.31 148.9 42.87 165.5 52.52 50.6
50 154.9 49.42 172.2 33.93 186.9 46.40 43.2
60 179.9 41.26 188.9 27,49 208.6 40.17 36.3
70 181.7 40.68 196.6 24.56 240.0 31.16 32.1
80 206.9 32.44 221.7 14.94 244.7 29.81 25.7
90 220.5 28.01 232.1 10.92 266.2 23.65 20.9
100 256.0 16.40 231.9 11.02 287.2 17.63 15.0
110 267.6 12.61 243.0 6.77 296.3 15.01 11.5
120 261.4 14.64 223.7 .14.17 296.3 15.01 14.6
130 271.4 11.39 232.8 11.66 315.9 9.39 10.8
140 276.0 9.87 231.6 11.13 302.6 13.21 11.4
150 264.9 13.50 241.7 7.25 300.1 13.91 11.6
160 289.9 5.33 250.4 3.90 326.2 6.44 5.22
170 290..8 5.06 255.6 1.91 327.9 5.95 4.31
180 277.6 9.34 241.6 7.28 321.2 7.87 8.16
TABLE 10
RENDVAL OF Co-58 BY PRIMARY SEDPIENTATION
aInfluent activity was 306.2 c/m.
b
Influent activity was 260.6 c/m.
CInfluent activity was 348.6 c/m.
Time Run 1 Run 2a Rhun 3b Average
in Eff. %Eff. % Eff. I %
Minutes c/m Removal .c/m Removal c/m Removal Removal
0 -- -- 17.81 -- 4.15 --
5 -- -- 20.85 99.49 4.33 99.79 99.6
10 -- -- 18.61 99.54 44.13 97.90 98.7
15 -- -- 555.8 86.36 410.8 80.44 83.4
20 -- -- 870.5 78.63 817.3 61.08 69.9
25 -- -- 1279. 68.60 1176. 44.00 56.3
30 -- -- 1649. 59.51 1311. 37.57 48.5
60 -- -- 1876. 53.94 1385. 34.05 44.0
50 -- -- 2317. 43.11 1423. 32.24 .37.7
60 -- -- 2648. 34.99 1480. 29.52 32.3
70 -- -- 2655. 34.81 1652. 21.33 28.1
80 -- -- 2713. 33.39 1619. 22.90 28.1
90 -- -- 2889. 29.07 1740. 17.14 23.1
100 -- -- 2889. 29.07 1815. 13.57 21.3
110 -- -- 3026. 25.71 1837. 12.52 19.1
120 -- -- 3200. 21.43 1888. 10.10 15.8
130 -- -- 3501. 16.04 1921. 8.52 11.3
160 -- -- 3950. 3.02 1837. 12.52 7.77
150 -- -- 3674. 9.80 1968. 6.29 8.04
160 -- -- 3734. 8.32 1860. 11.43 9.87
170 -- -- 3886. 4.59 1892, 9.90 7.24
180 -- -- 3833. 5.89 2000. 4.76 5.33
-80-
TABLE 11
RENDOVAL OF Sr-89 BY PRPIARY SEDIMENT~ATION
alnfluent activity was 4073 c/m.
blafluent activity was 2100 c/m.
a b c
Time Ru~n 1 Run 2 Run 3 Average
in Eff. 7. Eff. ;b Eff. % %
Minutes c/m Removal c/m Removal c/m Removal Removal
0 9.63 -- 3.70 -- 3.60 -
5 12.25 99.40 31.67 98.37 ~ 3.78 99.80 99.2
10 139.6 93.18 185.9 90.43 61.40 96.72 93.4
IS 644.0 68.52 295.5 84.79 112.3 94.00 82.4
20 730.4 61.37 583.1 69.99 480.4 74.34 68.6
25 912.1 55.42 736.3 62.10 700.1 62.60 60.0
30 1004. 50.93 936.3 51.81 906.7 51.57 51.4
40 1310. 35.97 1051. 45.91 1060. 43.38 41.8
50 1344. 34.31 1377. 29.13 1143. 38.94 34.1
60 1681. 17.84 1333. 31.40 1198. 36.00 28.4
70 1768. 13.59 1388. 28.56 1301. 30.50 24.2
80 1734. 15.25 1375. 29.23 1450. 22.54 22.3
90 1727. 15.59 1499. 22.85 1598. 14.64 17.7
100 1668. 18.48 1578. 18.78 1488. 20.51 19.3
110 1724. 15.74 1897. 2.34 1637. 12.55 10.2
120 1675. 18.13 1778. 8.49 1619. 13.51 13.4
130 1700. 16.91 1699. 12.56 1694. 9.51 13.0'
140 2040. 0.29 1647. 15.23 1833. 2.08 5.87
150 2022. 1.17 1778. 8.49 1687. 9.88 6.51
160 1938. 5.28 1764. 9.21 1747. 6.68 7.06
170 1885. 7.87 1807. 7.00 1760. 5.98 6.95
180 1834. 10.36 1796. 7.57 1830. 2.24 6.72
-81-
TABLE 12
REMOVAL OF MFP BYT PRIMARY SEDPIENTATION
alnfluent
blnfluent
cInfluent
activity was 2046
activity was 1943
activity was 1872
TABULATED DATA AND GRAPHS -- REMOVAL OF SELECTED
RADIONUCLIDES BY TRICKLING FILTRATION AND SECONDARY SEDIN~ENTATIDE
TABLE 13
REMDVAL OF P-32 BY TRICKLING FILTRATION
Depth Time Run 1 Run 2 Run 3 Average
in in Net 1 Net 1 Net % I
Feet Hlours c/m Removal c/m Removal c/m Removal Removal
0 5.46 -- 38.76 -- 0.92 -- --
2 5.56 -- 42.80 -- 19.46 -- --
4 0 5.08 -- 32.96 -- 24.09 -- --
6 3.65 -- 32.08 -- 31.31 -- --
8 4.91 -- 32.86 -- 21.04 -- --
0 249.0 -- 2002. -- 2331. -- --
2 216.8 12.93 1824. 8.91 2490. 0.00 7.28
4 2 183.3 26.39 1224. 38.85 1759. 24.54 29.9
6 148.4 40.38 1225. 38.81 1454. 37.60 38.9
8 115.7 53.52 1062. 46.97 1333. 42.81 47.8
0 213.6 -- 3568. -- 2601. -- --
2 195.5 8.47 3303. 7.42 3109. 0.00 5.30
4 4 191.0 10.62 3229. 9.49 2620. 0.00 6.70
6 145.2 32.03 2229. 37.52 1994. 23.35 31.0
8 116.6 45.42 2153. 39.65 2012. 22.63 35.9
0 232.5 -- -- -- 3362. -- --
2 193.5 16.70 -- -- 3254. 3.20 9.95
1 8 190.8 17.92 -- -- 2707. 19.46 18.7
6 147.6 36.51 -- -- 2247. 33.17 34.8
8 119.1 48.79 -- -- 2082. 38.07 43.4
0 415.7 -- 2511. -- 3480. -- --
2 279.6 32.73 1835. 26.92 2774. 20.29 26.6
4 12 240.9 42.06 1679. 33.13 2634. 24.31 33.2
6 233.0 43.94 1484. 40,91 2175. 37.49 40.8
8 220.2 47.03 1397. 44.39 2055. 40.94 44.1
0 452.0 -- 2573. -- 3323. -- --
2 270.1 40.09 1605. 37.61 2076. 19.49 32.4
4 24 277.6 38.55 1534. 40.40 2320. 30.20 36.4
6 237.2 47.53 1436. 44.20 2037. 38.70 43.5
8 209.5 53.66 1409. 45.24 2052. 38.26 45.7
APPENDIX E
Depth Time Run 1 Run 2 Run 3 Average
in in Net Z Net Z Net % 7.
Feet Bours c/m Removal c/m Removal c/m Removal Removal
0 1.39 -- 0.13 -- 0.00 -- --
2 3.78 -- 3.76 -- 0.00 -- --
4 0 9.42 -- 3.33 -- 0.62 -- --
6 5.49 -- 4.18 -- 1.94 -- --
8 6.34 -- 2.55 -- 1.45 -- --
0 430.3 -- 402.4 -- 361.9 -- --
2 228.6 46.86 208.3 48.24 177.8 50.86 48.7
4 2 192.4 55.29 175.9 56.27 140.2 61.27 57.6
6 164.6 61.75 142.8 64.50 128.8 64.40 63.6
8 134.1 68.84 124.0 69.17 123.2 65.97 68.0
0 401.5 -- 378.3 -- 357.9 -- --
2 218.1 45.69 206.4 45.43 216.4 39.54 43.6
4 4 187.9 53.19 175.1 53.70 174.2 51.32 52.7
6 148.9 62.91 147.2 61.10 149.7 58.18 60.7
8 134.1 66.59 132.5 64.97 129.3 63.87 65.1
0 497.3 -- 329.2 -- 426.0 -- --
2 325. 0 34.65 221.6 32.69 285.1 33.09 33.5
4 8 243.4 51.01 163.0 50.49 218.0 48.83 50.1
6 206.0 58.57 139.0 57.77 190.2 55.34 57.2
8 187.2 62.36 121.8 63.02 165.0 61.26 62.2
0 409.6 -- 349.6 -- 354.9 -- --
2 287.5 29.81 247.8 29.13 252.4 28.88 29.3
4 12 214.4 47.67 195.2 44.19 208.2 41.33 44.4
6 176.2 56.98 172.6 50.63 161.4 54.53 54.0
8 153.7 62.48 156.0 55.39 132.9 62.56 60.1
0 435.7 -- 343.2 -- 427.0 -- --
2 321.5 26.21 262.1 23.63 305.4 28.49 26.1
4 24 258.8 40.60 200.8 41.50 238.3 44.20 4.
6 203.4 53.32 172.1 49.85 183.7 56.97 53.4
8 173.5 60.18 140.5 59.06 156.2 63.42 60.9
-83-
TABLE 14
REMDOVAL OF I-131 BY TRICKLING FILTRATION
Depth Time Run 1 Run 2 Run 3 Average
in in Net 9. Net % Net I X
Feet Hours c/m Removal c/m Ramoval c/m Removal Removal
0 0.11 -- 0.00 -- 0.00 -- --
2 0.79 -- 0.00 -- 0.00 -- --
4 0 1.02 -- 0.00 -- 0.09 -- --
6 0.53 -- 0.00 -- 0.00 -- --
8 0.53 -- 0.00 -- 0.00 -- --
0 452.6 -- 19.21 -- 13.17 -- --
2 321.0 29.07 12.11 36.96 9.24 29.84 32.0
4 2 275.5 39.12 11.15 41.96 8.30 36.98 39.4
6 231.0 48.97 8.84 53.98 6.42 51.25 51.4
8 194.6 57.01 8.88 53.77 6.60 49.89 53.6
0 582.8 -- 23.08 -- 15.11 -- --
2 477.8 18.02 17.37 24.74 11.85 21.58 21.4
4 4 367.1 37.01 14.35 37.82 9.53 36.93 37.2
6 349.4 40.04 12.05 47.79 8.32 44.94 44.3
8 257.0 55.90 11.80 48.87 7.29 51.71 52.2
0 317.4 -- 27.56 -- 13.91 -- --
2 279.3 12.02 23.65 14.19 11.11 20.13 15.4
4 8 212.5 33.06 18.70 32.15 9.75 29.91 31.7
6 187.2 41.03 15.14 45.07 7.66 44.93 43.7
8 158.6 50.03 12.69 53.96 7.10 48.96 5.
0 -- -- 13,08 -- 16.30 -- --
2 -- -- 11.25 13.99 13.38 17.91 16.0
4 12 -- -- 9.14 30.12 11.10 31.90 31.0
6 -- -- 7.87 39.83 9.12 44.05 42.0
8 -- -- 5.88 55.04 8.81 45.95 50.5
0 -- -- 15.62 -- 9.64 -- --
2 -- -- 13.72 12.16 7.88 18.26 15.2
4 24 -- -- 10.30 34.06 6.19 35.79 36.9
6 -- -- 8.27 67.06 5.58 42.12 44.6
8 -- -- 7.21 53.84 5.40 43.98 48.9
TABLE 15
RENDAL OF K-42 BY TRICKLINGC FILTRATI~ON
Depth Time lu~n_ 1 un 2 Run 3 Average
in in Net % Net % Net X Z
Feat Houns c/m Remo~val c/m Removal c/m Removal Removal
0 2.19 -- 10.14 -- 34.56 --
2 3.30 -- 17.81 -- 42.59 -- -
4 0 0.87 -- 20.94 -- 37.04 -
6 ~ 3.00 -- 23.31 -- 27.15 --
8 1.73 -- 26.21 -- 34.67 -
0 2324. -- 3882. -- 3600. --
2 931.7 59.92 1226. 68.43 1389. 61.41 63.2
4 2 580.3 75.03 1205. 68.95 1057. 70.65 71.5
6 429.4 81.53 723.5 81.36 622.4 81.60 81.5
8 .221.8 90.46 414.4 89.32 316.6 91.21 90.3
0 3359. -- 3047. -- 3950. -
2 1263. 62.39 965.2 68.32 1480. 62.53 64.4
4 4 857.9 74.46 729.6 76.05 970.9 75.42 75.3
6 624.3 81.41 532.6 82.52 644.0 83.70 82.5
8 467.4 86.09 487.8 83.99 345.9 91.24 87.1
0 3361. -- 4375. -- 3118. ---
2 1500. 55.37 1539. 64.83 1185. 61.99 60.7
4 8 907.1 73.01 1143. 73.88 862.4 72.34 73.1
6 670.1 80.07 786.7 82.02 491.4 84.24 82.1
8 530.4 84.22 612.5 86.00 359.2 88.48 86.2~
0 2997. -- 4486. -- 4021. -- --
2 1342. 55.21 1713. 61.81 1488. 63.00 60.0
4 12 798.9 73.34 1170. 73.91 974.2 75.77 74.3
6 644.1 78.51 807.0 82.01 730.2 81.84 80.8
8 544.3 81.84 673.4 84.99 520.6 87.05 84.6
0 2721. -- 3143. -- 3065. -- --
2 1495. 45.04 1098. 65.07 1224. 60.07 56.7
4 24 802.8 70.49 1058. 66.33 1066. 65.23 63.4
6 631.0 76.81 712.6 77.33 636.8 79.23 77.8
8 630.5 76.83 620.6 80.26 422.9 86.20 81.1
-85-
TABLE 16
REMOVAL OF Ce-141, 144 BT TRICKLING FILTRATION
Depth Time Run 1 Run 2 R~un 3 Average
in in Met 1Net % Net % %
Feet Rours c/m Removal c/m Removal c/m Removal Removal
0 2.40 -- 3.81 -- 5.47 -- --
2 4.99 -- 6.0* -- 5.21 -- --
4 0 6.81 -- 6.63 -- 6.0 -- --
6 5.93 -- 7.17 -- 6.47 -- --
8 10.94 -- 19.33 -- 18.44 -- --
0 287.1 -- 237.3 -- 282.7 -- --
2 127.6 55.57 105.2 55.68 136.1 51.88 54.4
4 2 77.18 73.11 69.93 70.54 89.51 68.34 70.7
6 43.67 84.79 37.18 84.35 42.41 85.00 84.7
8 41.70 85.47 50.28 78.82 50.04 82.30 82.2
0 6.8 -- 312.2 -- 264.4 -- --
2 173.3 52.48 147.5 52.75 131.9 50.11 51.8
4 4 119.9 67.12 96.38 69.13 92.48 65.03 67.1
6 65.26 82.11 59.53 80.93 64.20 75..72 79.6
8 57.84 84.14 66.15 78.81 65.65 75.17 79.4
0 364.1 -- 340.1 -- 287.6 -- --
2 174.8 49.18 178.4 47.54 149.8 47.91 48.2
4 8 150.9 56.16 124.0 63.55 111.6 61.21 60.3
6 92.72 73.06 86.03 74.71 79.02 72.53 73.4
8. 92.09 73.24 69.16 79.67 71.65 75.09 76.0
0 227.6 -- 220.2 -- 198.3 -- --
2 134.7 40.81 127.6 42.04 99.49 49.82 44.2
4 12 109.4 51.94 94.83 56.93 73.69 62.84 57.2
6 58.96 74.09 67.03 69.56 48.72 75.43 73.0
8 60.74 73.31 62.35 71.,68 55.59 71.96 72.3
0 213.1 -- 227.3 -- 191.8 -- --
2~ 119.6 43.85 136.0 40.15 88.61 53.79 45.9
4 24 94.31 55.74 95.49 57.99 77.34 59.67 57.8
6 50.20 76.44 60.00 73.60 65.66 65.76 71.9
8 71.50 66.45 83.62 63.21 66.36 65.40 65.0
TABIE 17
REHDVAL OF Fe-59 BY TRICKLINYG FILTRATION
Depth Thme Rlun 1 Run 2 Run 3 Average
in in Net Z Net % Net %; Z
Feet Hours c/m Removal c/m Removal c/m Removal Removal
0 1.73 -- 3.72 -- 2.93 -- --
2 6.45 -- 6.66 -- 6.33 -- --
4 0 5.59 -- 4.97 -- 6.55 -- --
6 5.35 -- 4.92 -- 5.88 -- --
8 5.24 -- 8.08 -- 6.77 -- --
0 161.2 -- 165.6 -- 162.3 -- --
2 72.62 54.95 74.69 54.89 71.07 56.22 55.4
4 2 54.69 66.07 55.02 66.77 43.90 72.96 68.6
6 24.92 84.54 27.35 83.48 25.03 84.58 84.2
8 22.97 85.75 25.57 84.56 20.71 87.24 85.9
0 184.1 -- 173.6 -- 194.2 -- --
2 88.50 51.94 82.16 52.67 97.01 50.06 51.6
4 4 68.82 62.63 54.16 68.80 57.76 70.26 67.2
6 34.16 81.45 36.49 78.98 35.59 81.68 80.7
8 34.30 81.37 28.05 83.84 29.36 84.88 83.4
0 179.2 -- 178.3 -- 196.1 -- --
2 80.85 54.90 82.23 53.88 99.54 49.25 52.7
4 8 58.52 67.35 53.58 69.95 80.50 58.96 65.4
6 40.66 77.32 38.14 78.61 43.45 77.85 77.9
8 33.80 81.14 31.99 82.06 42.58 78.29 80.5.
O 167.2 -- -- -- \200.0 -- --
2 97.34 41.78 -- -- 111.0 44.50 43.1
4 12 59.61 64.35 -- -- 67.04 66.48 65.4
6 38.44 77.01 -- -- 40.77 79.61 78.3
8 33.82 79.77 -- -- 33.39 83.30 81.5
0 132.7 -- 177.7 -- 144.2 -- --
2 84.75 36.13 80.49 54.70 69.44 51.84 47.6
4 24 51.14 61.46. 55.32 68.86 45.58 68.39 66.2
6 29.17 78.02 27.01 84.80 30.90 78.57 80.5
8 30.64 76.91 31.13 82.48 23.83 83.07 81.0
TABLE 18
REMOVAL DF Co-58 BY TRICKLING FILTRATION
Depth Time Run 1 Run 2 Run 3 Average
in in Net. 1X Net Z Net % %
Feet Bours c/m Removal c/m Rlmoval c/m Removal Removal
0 2.69 -- ~5.26 -- 5.40 -- --
2 9.32 .-- 63.08 -- 84.10 -- --
4 0 5.82 -- 48.58 -- 63.93 -- --
6 4.43 -- 52.48 -- 62.53 -- --
8 3.80 -- 31.48 -- 48.11 -- --
0 1686. -- 1814. -- 1554. -- --
2 628.0 .62.75 1055. 41.84 791.9 49.04 51.2
4 2 465.1 72.41 688.8 62.03 623.2 59.90 64.8
6 216.4 87.16 297.2 83.62 323.7 79.17 83.3
8 120.0 92.88 222.9 87.71 226.6 85.42 88.7
0 ,.1376. -- 2444. -- 1918. -- --
2 802.5 41.68 1440. 41.08 1082. 43.59 42.1
4 4 584.7 57.51 908.6 62.82 809.6 57.79 59.4
6 356.2 74.11 585.5 76.04 437.8 77.18 75.8
8 232.3 83.12 484.1 80.17 366.5 80.89 81.4
0 1550. -- 2102. -- 1633. -- --
2 929.5 40.03 1221. 41.91 1254. 23.21 35.0
4 8 802.5 48.23 1117. 46.86 1053. 35.52 43.5
6 566.5 64.03 702.8 66.57 670.1 58.97 63.2
8 472.4 69.52 579.0 72.45 655.4 59.87 67.3
0 1490. -- 2225. -- 1842. -- --
2 1040. 30.20 1552. 30.25 1441. 21.77 27.4
4 12 764.1 48.72 1338. 39.87 1095. 40.55 43.0
6 691.9 53. 56 1034. 53.53 981.8 46.70 51.3
8 661.6 55.60 1072. 51.82 812.7 55.88 54.4
0 1540. -- 2196. -- 1714. -- --
2 1143. 25.78 1609. 26.73 1397. 18.50 23.7
4 24 1060. 31.17 1589. 27.64 1329. 22.46 27.1
6 919.3 40.31 1243. 43.40 1229. 28.30 37.3
8 847.5 44.97 1183. 46.13 1095. 36.12 42.4
TABLE. 19
REMDWAL OF Sr-89 BY TRICKLING FILTRATION
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