EPA-600/2-75-034
September 1975
Environmental Protection Technology Series
TRENCH INCORPORATION OF
SEWAGE SLUDGE IN
MARGINAL AGRICULTURAL LAND
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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EPA-600/2-75-034
September 1975
TRENCH INCORPORATION OF SEWAGE SLUDGE IN MARGINAL
AGRICULTURAL LAND
by
J. M. Walker, W. D. Burge, R. L. Chaney,
E. Epstein, and J. D. Menzies
Biological Waste Management Laboratory
Agricultural Research Service
United States Department of Agriculture
Beltsville, Maryland 20705
for
Maryland Environmental Service
Maryland Department of Natural Resources
Annapolis, Maryland 21401
and
District of Columbia
Department of Environmental Services
Washington, D. C. 20032
Program Element No. 1BB043
Project Officer
D. F. Bishop
Wastewater Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental
Research Laboratory, U.S. Environmental Protection Agency,
and approved for publication. Approval does not signify that
the contents necessarily reflect the views and policies of
the U.S. Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement
or recommendation for use.
11
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FOREWORD
Man and his environment must be protected from the adverse
effects of pesticides, radiation, noise, and other forms of
pollution, and the unwise management of solid waste. Efforts
to protect the environment require a focus that recognizes
the interplay between the components of our physical environ-
ment—air, water, and land. The Municipal Environmental
Research Laboratory contributes to this multidisciplinary
focus through programs engaged in
• studies on the effects of environmental contaminants
on the biosphere, and
9 a search for ways to prevent contamination and to
recycle valuable resources.
This report describes an approach for the recycling of val-
uable resources in sludges from biological wastewater treat-
ment plants and indicates the potential beneficial effect of
the recycling on part of the biosphere. The report also
summarizes a study of the effect of environmental contaminants
in the sludge on the biosphere.
A.W. Breidenbach, Ph.D.
Director
Municipal Environmental
Research Laboratory
1X1
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ABSTRACT
Entrenchment is a feasible method for simultaneously disposing of
dewatered sewage sludges (15-25% solids) and improving marginal land for
plant growth. The primary problem is to avoid pollution of groundwater
with nitrate-nitrogen. Recommendations are given for running a sludge
trenching operation. In the study, application rates were 800 and 1150
metric tons/hectare (350 and 500 tons/acre) dry solids, respectively, in
trenches 60 cm (2 feet) wide x 60 cm deep x 60 cm apart and 60 cm wide x
120 cm deep x 120 cm apart.
Entrenchment prevented contamination of surface water, buried pathogens
permitting their demise during sludge decomposition, promoted slow
nitrogen release, and favored denitrification.
Nineteen months after sludge entrenchment, fecal coliform and salmonella
bacteria had not been detected in sandy soil more than a few centimeters
from the entrenched sludge. No significant downward movement of heavy
metals had been detected, and metal uptake by crops had been moderate.
Nitrate movement had occurred, causing increased levels in underdrained
water. Groundwater in monitoring wells did not show increases in any
pollutants that might have come from the sludge except chloride.
The Agricultural Research Service, in cooperation with the Maryland
Environmental Service and the District of Columbia, has submitted this
report in partial fulfillment of Contract No. 68-01-0162 under the
partial sponsorship of the Environmental Protection Agency. The report
covers research work conducted from January 1972 to January 1974.
IV
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CONTENTS
DISCLAIMER
FOREWORD
ABSTRACT
LIST OF FIGURES
LIST OF TABLES
ACKNOWLEDGMENTS
SECTIONS
I SUMMARY AND CONCLUSIONS
II RECOMMENDATIONS
III INTRODUCTION
IV FIELD ENTRENCHMENT OF SLUDGE
SITE CHARACTERISTICS
Groundwater
Drainage
Soil
Wells
SLUDGE INCORPORATION
Engineering Report - Whitman, Requardt and
Associates
Introduction
Site Preparation and Maintenance
Transportation
Operation
Conclusions and Recommendations
ARS Observations on Sludge Incorporation
Timing
Tillage After Incorporation
Incorporation Equipment and Facilities
Page
11
iii
iv
ix
xiv
xviii
1
7
12
14
14
14
14
20
23
29
29
29
29
31
33
37
39
39
39
42
v
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Trench Spacing and Sludge Application Rate 43
Liquid Sludge Incorporation 46
Odor 47
Sludge Characteristics 47
OTHER PROCEDURES 47
Planting 47
Seedbed Preparation 60
Plant, Soil, and Sludge Monitoring 60
Miscellaneous 67
RESULTS AND DISCUSSION 69
Surface and Underground Water Analysis 69
Coliform and Viruses 69
Ammonium- and Nitrate-Nitrogen 75
Chloride and Conductivity 76
Other Chemical Analyses 81
Entrenched Sludge and Surrounding Soil 81
Introduction 81
Movement and Persistence of Coliform and 87
Salmonellae
Movement and Fate of Ammonium- and Nitrate- 103
Nitrogen
Possibilities for Denitrification 104
Possible Significance of Nitrogen Results 104
Movement of Chloride 104
Movement of Heavy Metals 113
Change in Sludge Physical Properties 113
Changes in Sludge Chemical Properties 122
Plant Response 126
Sweet Corn 1972 126
Rye 1972-73 129
Fescue Growth 1972-73 129
Soybeans 1972 133
Fruit and Shade Trees 1972-73 133
Comparative Crop Response on Plots "a" and "b" 139
V SLUDGE pH TRIALS 142
INTRODUCTION 142
PROCEDURES 142
VI
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RESULTS AND DISCUSSION 145
pH 145
Organic Matter 145
Total Coliform and Fecal Coliform 145
Salmonellae 149
Nitrogen 152
Plant Response 154
VI GREENHOUSE STUDIES - TRENCH SIMULATION 157
INTRODUCTION 157
PROCEDURE 157
RESULTS AND DISCUSSION - EXPERIMENT 1 160
Digested Sludge 160
Sludge and Soil Moisture 160
Plant Growth 161
Gas Analyses 161
Nitrogen in Drainage Water 165
Zinc in Plants 165
Alum-Lime Sludge 165
Plant Growth 165
Gas Analyses 170
Nitrogen in Drainage Water 170
CONCLUSIONS - EXPERIMENT 1 173
RESULTS AND DISCUSSION - EXPERIMENT 2 178
Introduction 178
Soil Moisture 178
Soil and Sludge Nitrogen 178
Gas Analyses 179
Plant Growth 185
Salmonella, Total Coliform, and Fecal Coliform 187
Bacteria
Heavy Metals 191
CONCLUSIONS - EXPERIMENT 2 194
VII VIRUS TRANSPORT THROUGH SOIL 195
INTRODUCTION 195
Vll
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PROCEDURES 195
RESULTS 196
DISCUSSION 199
VIII HEAVY METALS 204
ANALYSES OF BLUE PLAINS SLUDGES 204
Procedures 204
Results 204
ANALYSES OF OTHER SLUDGES 207
PLANT GROWTH STUDIES 211
Procedure 212
Results 214
APPENDIX - REPORT ON COOPERATIVE RESEARCH ON TRENCHING FOR 218
PERIOD MAY 1 - NOVEMBER 1, 1974
Vlll
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FIGURES
No. Page
1 Partial site map 15
2 Soil surface, water table, and impermeable soil boundary
locations determined in January 1972
(A) East-West 16
(B) South-North 17
3 Tile installation 18
4 Well cross-section with water sampler 24
5 Pouring cement grout around well casing 25
6 Grout failure on well 22 26
7 Water vacuum sampling system 27
8 Well sampling 28
9 Plot dimension and tillage 30
10 Sludge incorporation 40
11 Aerial photo of site (May 19, 1972) 41
12 Cement truck for hauling sludge 44
13 Trencher 45
14 Plot plan for crops planted June 1972
(A) Digested, la 50
(B) Digested, Ib 51
(C) Digested, Ha, lib 52
(D) Raw-limed, Ilia, Illb 53
(E) Liquid raw-limed, IVa, IVb 54
15 Plot plan for crops planted in October 1972 with crop
stand ratings (1-poor to 5-very good) made on March 15,
1973
(A) Digested, la 55
(B) Digested, Ib 56
(C) Digested, Ha, lib 57
(D) Raw-limed, Ilia, Illb 58
(E) Liquid raw-limed, IVa, IVb 59
IX
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16 Plot plan for crops planted in early Fall 1973 with crop
stand ratings (1-poor to 5-very good) made on
December 4, 1973
(A) Digested, la 61
(B) Digested, Ib 62
(C) Digested, Ha, lib 63
(D) Raw-limed, Ilia, Illb 64
(E) Liquid raw-limed, IVa, IVb 65
17 Gas sampling system 66
18 Excavation and sampling of entrenched sludge and
surrounding soil 68
19 Schematic representation of entrenched sludge and 90
surrounding soil showing labeling scheme in inches
20 Ammonium- and nitrate-nitrogen in and around entrenched
sludge 17 months after entrenchment
(A) Control (Va) 97
(B) Raw-limed (Ilia) 98
(C) Digested (la) 99
(D) Digsted (la) (19 months after entrenchment) 100
(E) Raw-limed liquid (IVa) (19 months after entrenchment) 101
(F) Digested (Ila) 102
21 Total nitrogen and chloride in and around entrenched
sludge 17 months after entrenchment
(A) Control (la) 105
(B) Raw-limed (Ilia) 106
(C) Digested (la) 107
(D) Digested (la) 108
(E) Raw-limed liquid (IVa) (19 months after entrenchment) 109
(F) Digested (Ila) 110
22 Levels of methane, carbon dioxide, and oxygen 111
(15 cm) below digested sludge in 60 x 60 cm
trench with time after entrenchment
23 Levels of methane, carbon dioxide, and oxygen 111
(15 cm) below raw-limed sludge in 60 x 60 cm
trench with time after entrenchment
24 Levels of methane, carbon dioxide, and oxygen 112
(15 cm) below digested sludge in 60 x 120 cm
trench with time after entrenchment
25 Extractable zinc and copper in and around entrenched
sludge 18 months after entrenchment
(A) Control (Va) 116,
(B) Raw-limed (Ilia) (17 months after entrenchment) 117
x
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(C) Digested (la) (17 months after entrenchment) 118
(D) Digested (la) (19 months after entrenchment) 119
26 Cross-sectional excavation of entrenched digested 120
sludge after 17 months (Oct. 17, 1973) showing
degree of weathering
27 Sweet corn growing on sludge plots, August 1972
(A) Growth on 60 x 60 cm digested sludge 127
disked plot la
(B) Growth on 60 x 60 cm raw-limed sludge 127
plot Ilia
(C) Growth on 60 x 60 cm digested sludge 128
plot Ila
(D) Growth on 60 x 120 cm raw-limed liquid 128
sludge disked plot IVa
28 Rye growing on raw-limed liquid sludge plot IVa 130
in May 1973
29 Fescue in December 1973 growing over entrenched digested 131
sludge on plot la in upper right hand corner above line
and over control V on left side of photo
30 Jefferson peach trees, similarly sized seedlings 138
transplanted into soil between entrenched digested
sludge and fertilized control soil in June 1972,
photographed October 1972
31 Trench and surface plot layout for sludge pH 144
investigations with April 1973 crop ratings
32 Survival of total coliform in entrenched and surface 147
incorporated limed and unlimed raw and digested sludges
33 Survival of fecal coliform in entrenched and surface 148'
incorporated limed and unlimed raw and digested sludges
34 Response of rye and alfalfa to entrenched sludge 156
in May 1973
35 Diagram of trench simulation box 158
36 Penetration of corn roots into a simulation trench 162
of digested sludge - 5 months after planting
37 Appearance of digested sludge in simulated trench 163
after penetration and dewatering by corn roots
during a 5-month growth period
38 Methane, carbon dioxide, and oxygen levels within 164
the simulated trench of digested sludge
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39 Methane, carbon dioxide, and oxygen levels in soil 166
2 cm below the simulated trench of digested sludge
40 Corn root behavior in contact with "trench" of alum- 168
lime sludge - 42 days after planting
41 Corn root behavior in contact with "trench" of alum- 169
lime sludge - 3 months after planting
42 Methane, carbon dioxide, and oxygen levels within 171
the simulated trench of raw alum-limed sludge
43 Methane, carbon dioxide, and oxygen levels in soil 172
6 cm below the simulated trench of raw alum-limed
sludge
44 Total nitrogen (ppm) in trench simulation boxes 176
after 161 days
45 Ammonium-nitrogen (ppm) in trench simulation boxes 177
after 161 days
46 Nitrate-nitrogen (ppm) in trench simulation boxes 178
after 161 days
47 Soil and sludge pH in trench simulation boxes after 180
161 days
48 Methane, carbon dioxide, and oxygen levels in soil
centered 8 cm below the simulated trench
(A) Digested high pH sludge 181
(B) Digested low pH sludge 182
(C) Raw high pH sludge 183
(D) Raw low pH sludge 184
49 Photographs of root distribution in trench simulation 186
boxes after 98 days
50 The MPN/g dry weight of total coliform bacteria in 189
trench simulation boxes after 161 days
51 The MPN/g dry weight of fecal coliform bacteria in 190
trench simulation boxes after 161 days
52 Zinc distribution (DTPA-TEA extractable, yg Zn/g 192
dry soil or sludge) in trench simulation boxes
after 161 days
53 Copper distribution (DTPA-TEA extractable, yg Cu/g 193
dry soil or sludge) in trench simulation boxes
after 161 days
xii
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54 Elution of Xanthomonas £runjL bacteriophage from 197
Galestown-Evesboro sandy loam soil. Rate of
leaching was 1 cm/hour and the column was 8.5 cm
long
55 Distribution of Xanthomonas pruni bacteriophage 198
adsorbed on a column of Galestown-Evesboro sandy
loam soil after 300 ml leaching at 1 ml per hour
56 Elution of poliovirus from Galestown-Evesboro 200
sandy loam soil
57 Comparison of elution curves of poliovirus applied 201
continuously (1 cm per hour) at two concentrations
of Galestown-Evesboro sandy loam soil
58 Distribution of poliovirus adsorbed with depth of 202
columns of Galestown-Evesboro sandy loam soil after
applying continuously in the influent of two concen-
trations of poliovirus for 400 hours at 1 cm per hour
xxn
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TABLES
No_._ Page
1 GROUNDWATER WELLS - DEPTH AND WATER LEVELS - 1972-1973 19
2 ANALYSES OF SOILS FROM TEST TRENCHES 20
3 SOILS AND WATER TABLE IN PROPOSED PLOT AREAS 21,22
4 SLUDGE ENTRENCHMENT DATA 46
5 BACTERIAL AND VIRAL CONTENT OF COMPOSITED ENTRENCHED 48,49
SLUDGES
6 PRECIPITATION AT BELTSVILLE 70
7 SUMMARY OF TOTAL COLIFORM ANALYSES OF SURFACE AND 71
UNDERGROUND DRAINAGE WATERS
8 SUMMARY OF FECAL COLIFORMS AND VIRAL ANALYSES OF 72
SURFACE AND UNDERGROUND DRAINAGE WATERS
9 SUMMARY OF TOTAL COLIFORM ANALYSES OF UNDERGROUND 73
WELL WATER
10 SUMMARY OF FECAL COLIFORM AND VIRAL ANALYSES 74
OF UNDERGROUND WELL WATER
11 COMPARISON OF FECAL COLIFORMS AND NITRATE-NIRTOGEN 76
IN SUBSURFACE DRAIN TILE (RIGHT) AND PLOT WELL 16
12 SUMMARY OF NITROGEN ANALYSES OF SURFACE AND UNDERGROUND 77
DRAINAGE WATERS
13 SUMMARY OF NITROGEN ANALYSES OF UNDERGROUND WELL WATERS 78
14 CHLORIDE ANALYSES OF UNDERGROUND WELL WATER 79
15 CONDUCTANCE OF UNDERGROUND WELL WATER 80
16 ANALYSES OF SURFACE AND UNDERGROUND WELL WATER FOR SO,, 82
P04, Cl, NH4, AND NOs
17 ANALYSES OF SURFACE AND UNDERGROUND WELL WATER FOR: 83
K, Na, Ca, Mg, CONDUCTANCE AND pH
18 ANALYSES OF SURFACE AND UNDERGROUND WELL WATER FOR: 84
Fe, Mn, Zn} Cd, Cr, Ni, Pb, Hg, AND Cu
xiv
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19 ANALYSES OF SURFACE AND UNDERGROUND WELL WATER FOR 85
INORGANIC AND ORGANIC CARBON AND DISSOLVED SOLIDS
20 SURFACE WATER CRITERIA FOR PUBLIC WATER SUPPLIES 86
21 BACTERIA IN ENTRENCHED (60 x 60 cm) DIGESTED SLUDGE 88,89
AND IN SURROUNDING SOIL
22 BACTERIA IN ENTRENCHED (60 x 120 cm) DIGESTED SLUDGE 91
AND IN SURROUNDING SOIL
23 BACTERIA IN ENTRENCHED (60 x 60 cm) RAW-LIMED SLUDGE 92,93
AND IN SURROUNDING SOIL
24 BACTERIA IN ENTRENCHED (60 x 120 cm) RAW-LIMED LIQUID 94
SLUDGE AND IN SURROUNDING SOIL
25 THE pH OF RAW-LIMED SLUDGE INITIALLY AND WITH TIME 95
AFTER ENTRENCHMENT IN PLOT Ilia
26 NITRATE-NITROGEN MOVEMENT INTO SOIL FROM ENTRENCHED 96
SLUDGE
27 CHEMICAL OXYGEN, TOTAL NITROGEN, AND TOTAL CARBON IN 103
SOIL SURROUNDING 60 x 60 cm DIGESTED (NO TOTAL C) AND
RAW SLUDGE TRENCHES 17 MONTHS AFTER SLUDGE ENTRENCHMENT
28 EXTRACTABLE ZINC IN AND AROUND DIGESTED AND RAW-LIMED 114
ENTRENCHED SLUDGE WITH TIME
29 EXTRACTABLE COPPER IN AND AROUND DIGESTED AND RAW-LIMED 115
ENTRENCHED SLUDGE WITH TIME
30 WATER CONTENT OF SLUDGES AFTER ENTRENCHMENT 121
31 CHEMICAL CHARACTERISTICS OF RAW-LIMED SLUDGE (60 x 60 cm) 122
AS INFLUENCED BY DECOMPOSING (17 MONTHS AFTER ENTRENCHMENT)
32 CHEMICAL CHARACTERISTICS OF DIGESTED SLUDGE (60 x 60 cm) 123
AS INFLUENCED BY EXTENT OF DECOMPOSITION (17 MONTHS AFTER
ENTRENCHMENT)
33 CHEMICAL CHARACTERISTICS OF DIGESTED SLUDGE (60 x 60 cm) 124
AS INFLUENCED BY EXTENT OF DECOMPOSITION (19 MONTHS AFTER
ENTRENCHMENT)
34 CHEMICAL CHARACTERISTICS OF DIGESTED SLUDGE AS INFLUENCED 125
BY EXTENT OF DECOMPOSITION (19 MONTHS AFTER ENTRENCHMENT)
35 UPTAKE OF HEAVY METALS BY KENTUCKY-31 TALL FESCUE 134,135
36 FRUIT TREE STATUS ON DECEMBER 4, 1973 136,137
xv
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37 HEAVY METAL LEVELS IN PEACH TREE LEAVES 139
38 SHADE TREE STATUS ON DECEMBER 4, 1973 140,141
39 INITIAL CHARACTERISTICS OF DIGESTED AND RAW SLUDGES 143
40 ENTRENCHED AND SOIL-MIXED SLUDGE pH WITH TIME 146
41 SURVIVAL OF SLAMONELLA BACTERIA IN ENTRENCHED AND 150
UNLIMED RAW AND DIGESTED SLUDGE
42 SURVIVAL OF SALMONELLA BACTERIA IN SOIL SURFACE 151
INCORPORATED LIMED AND UNLIMED RAW AND DIGESTED SLUDGE
43 NITRATE AND AMMONIUM NITROGEN WITH TIME AFTER 153
ENTRENCHMENT OF LIMED AND UNLIMED RAW AND DIGESTED
SLUDGES IN SOIL
44 NITRATE AND AMMONIUM NITROGEN WITH TIME AFTER SURFACE 155
INCORPORATION OF LIMED AND UNLIMED RAW AND DIGESTED
SLUDGES IN SOIL
45 NITROGEN COMPOUNDS IN DRAINAGE WATER FROM A TRENCH 167
SIMULATION BOX CONTAINING DIGESTED SLUDGE
46 ZINC CONTENT OF WHOLE CORN PLANTS GROWING IN A TRENCH 167
SIMULATION BOX CONTAINING DIGESTED SLUDGE
47 NITROGEN COMPOUNDS IN DRAINAGE WATER FROM TRENCH 173
SIMULATION BOX CONTAINING ALUM-LIME SLUDGE
48 SOIL MOISTURE PERCENT IN TRENCH SIMULATION BOXES AT 175
10 AND 40 cm
49 HEIGHT AND STEM DIAMETER OF CORN PLANTS GROWING IN 185
TRENCH SIMULATION BOXES AFTER 87 DAYS
50 MOST PROBABLE NUMBER (MPN) OF SALMONELLA, TOTAL 188
COLIFORM AND FECAL COLIFORM BACTERIA IN SLUDGES
USED FOR GREENHOUSE TRENCH SIMULATION BOX STUDIES
51 ANALYSES OF BLUE PLAINS SLUDGES, FEBRUARY 8-14, 1972 205,206
52 ANALYSES OF BLUE PLAINS SLUDGE AS INFLUENCED BY LIME 208
53 ANALYSES OF BLUE PLAINS SLUDGES, APRIL 1974 209
54 MEAN ELEMENTAL CONTENTS OF BLUE PLAINS SLUDGE 210
55 HEAVY METAL CONTENTS OF WASHINGTON AREA WASTEWATER 211
TREATMENT PLANT SLUDGES
xvi
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56 HEAVY METAL CONTENT OF VARIOUS SEWAGE SLUDGES 212
57 YIELD OF VARIOUS CROPS IN EVESBORO LOAMY SAND AMENDED 213
WITH BALTIMORE DIGESTED SLUDGE, EQUIVALENT RATES OF
ZINC AND COPPER, PEAT, AND FERTILIZER ONLY
58 ZINC CONTENT OF LEAVES OF VARIOUS CROPS GROWN IN 215
EVESBORO LOAMY SAND AMENDED WITH DIGESTED SLUDGE,
EQUIVALENT RATES OF ZINC AND COPPER, PEAT, AND
FERTILIZER ONLY
59 COPPER CONTENT OF LEAVES OF VARIOUS CROPS GROWN IN 216
EVESBORO LOAMY SAND AMENDED WITH DIGESTED SLUDGE,
EQUIVALENT RATES OF ZINC AND COPPER, PEAT, AND
FERTILIZER ONLY
APPENDIX TABLES
1A NITRATE-NITROGEN MOVEMENT INTO SOIL FROM ENTRENCHED 222
SLUDGE
2A AMMONIUM-NITROGEN MOVEMENT INTO SOIL FROM ENTRENCHED 223
SLUDGE
3A THE pH OF ENTRENCHED SLUDGE AND SURROUNDING SOIL 224
4A CHLORIDE MOVEMENT INTO SOIL FROM ENTRENCHED SLUDGE 225
5A TOTAL AND DTPA EXTRACTABLE ZINC MOVEMENT INTO SOIL 226
FROM ENTRENCHED SLUDGE
6A DTPA EXTRACTABLE AND TOTAL COPPER MOVEMENT INTO SOD 227
FROM ENTRENCHED SLUDGE
7A TOTAL COLIFORM MOVEMENT INTO SOIL FROM ENTRENCHED 228
SLUDGE
8A CONTENTS OF NH4-N, N03~N, AND Cl IN UNDERGROUND, DRAINAGE, 229
AND STORED WATER FROM TRENCH AREA
9A ELEMENTAL CONTENT OF FESCUE HARVESTED OVER THE 60-60-60 230
ENTRENCHED SLUDGE AFTER 25 MONTHS
10A ELEMENTAL CONTENT OF FESCUE AND ALFALFA GROWING OVER 231
AND BETWEEN 60-60-60 DIGESTED SLUDGE TRENCHES AFTER
25 MONTHS
xvi i
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ACKNOWLEDGMENTS
We gratefully acknowledge the considerable efforts of many individuals
and organizations who have contributed significantly to the project
described herein. In particular, we acknowledge the help and support
of officials and citizens of Prince Georges County, the District of
Columbia, the Maryland Department of Health and Mental Hygiene, the
Maryland Department of Natural Resources, and the EPA Municipal
Environmental Research Laboratory, Cincinnati, Ohio.
Cooperating scientists and support personnel in ARS who have contri-
buted include: J. 0. Legg, W. D. Kemper; J. V. Lagerwerff, J. M.
Taylor, N. K. Enkiri, A. V. Gibson, L. E. Gross, J. B. Munns, A. R.
Kaminski, M. L. Terwilliger, M. R. Peters, and S. M. Hoffman. Support
personnel employed by MES on the work have been: M. C. White, J. C.
Baxter, D. Mosher, L. C. Olver, T. L. Lathan, W. T. Palmer, and
J. Marmelstein. Also acknowledged is the work of W. H. Harrington
and R. H. Becker or Whitman, Requardt, and Associates.
xvin
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SECTION I
SUMMARY AND CONCLUSIONS
GENERAL
Research and demonstrations in the field and laboratory have shown that
digested and limed undigested (raw-limed) dewatered sewage sludges (18
to 25% solids) can be incorporated into soil in small closely spaced
trenches without odor problems or the hazard of surface water runoff.
In the field approximately 1 hectare (2.5 acres) was trenched and
filled with the dewatered and liquid sludges in test plots in 2 hectares
of a 10-hectare watershed.
DRAINAGE AND WELLS
The water table of the test area was determined by drilling 40 test
wells. Drain lines and diversion ditches were installed to carry ground-
water and surface water from the entrenchment area into a 0.4 hectare
(1 acre) pond constructed to hold 3750 cubic meters (1 million gallons)
of water. The 40 test wells were also used to monitor the entrenchment
site and adjacent areas.
TRENCH SPACING AND SLUDGE APPLICATION RATE
Dewatered sludges (20 to 25% solids) were placed in trenches that were
either 60 cm (2 feet) wide by 60 cm deep by 60 cm apart (60 x 60 x
60 cm) or were 60 x 120 x 120 cm. Resulting rates of dewatered sludge
application in the filled trenches were approximately 800 and 1150 dry
metric tons/hectare (350 and 500 dry tons/acre) respectively.
Limed liquid undigested (raw) sludge (5 to 8% solids) was placed in
trenches that were 60 x 120 x 240 to 320 cm. The wider spacing between
trenches was necessary because of the instability of the sandy soils
when the trenches were half filled with liquid sludge. If more than
half filled, sludge would overflow from trenches when backfilled with
soil. The resulting rate of liquid sludge entrenchment was 125 dry
metric tons/hectare (55 dry tons/acre).
HAULING AND INCORPORATION
While dump trucks and front-end loaders were successfully used to haul,
move, and place large amounts of sludge in our test plots, the method
produced considerable soil surface contamination, and equipment bogged
down during rainy weather.
The trencher used for the simultaneous digging of the trenches and
covering of the trenches previously filled with sludge was generally
satisfactory. Some slippage of the trencher occurred but the addition
of cleats to the metal tracks should minimize the slippage. Narrow
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spacing between trenches was possible because of the digging mechanism
which was moveable from side to side behind the metal tracks.
TILLAGE
The plots were either left in ridges; leveled and disked; or leveled,
disked, and cross-ripped. There was no apparent harm in leaving the
area ridged for a time, but it was difficult to establish a satisfactory
ground cover on the ridged soil even by hydroseeding. Ripping the
sludge at right angles to the trenches did not cause significant sub-
surface mixing of sludge nor did it improve crop growth. Because of the
softness of the area, a tracked vehicle was needed to pull the ripping
equipment. Leveling the ridges over the trenches left a layer of soil
28 to 35 cm (10 to 15 inches) thick over the sludge and original soil
surface. This soil covering had to be limed and fertilized or treated
with digested sludge at a rate of 35 to 60 dry metric tons/hectare (15
to 25 dry tons/acre) prior to seeding to establish a crop. Irrigation
was also necessary on this very sandy soil.
It was very difficult to cultivate the area in which the liquid sludge
was entrenched because of the wet soil conditions.
CROP GROWTH
Kentucky-31 tall fescue grass, corn, soybeans, alfalfa, and fruit and
shade trees were successfully grown on the test plots. Corn growth was
initially inhibited by the recently entrenched sludge because of high
concentrations of ammonia, low concentrations of oxygen, and the presence
of unidentified volatile compounds. This initial toxic response was not
apparent in tall fescue.
Crop growth was poorer where sludge was deeper below the surface and
where spaces between trenches were greater. Growth was particularly
poor on the limed liquid undigested sludge plots where the spacing
between trenches was 240 to 300 cm (8 to 10 feet).
NITROGEN
Analyses of well waters did not show increased concentrations of nitrate
or ammonium nitrogen, and concentrations of these two nitrogen forms in
the holding pond have not exceeded drinking water standards. Compara-
tively, in part of the underground drainage water which empties into the
pond, nitrate levels have steadily increased to levels above drinking
water standards. Probably subsurface water with low levels of nitrate
and ammonium nitrogen have also been entering the pond and causing some
dilution. It is not known whether there has been loss of these two
forms of nitrogen by some other mechanism. The pond water has been dis-
charged directly into normal drainage channels because of continued high
quality of the water. Irrigation equipment is available for land treat-
ment of the pond water if its quality degenerates.
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There was evidence of increasing movement of nitrogen downward from the
entrenched sludge with time. As plant roots penetrated, the sludges
became more aerobic which allowed nitrate to form, less denitrification
to occur, and more water to leach through, carrying the nitrate along.
Entrenched sludges were aerobic first on the top and later on the sides
as roots penetrated and dewatered the sludge. A much slower rate of
sludge dewatering occurred in the absence of roots.
Denitrification of the nitrate to nitrogen gas apparently occurred to
the greatest degree under the 60-cm deep limed undigested (raw-limed)
sludge trench. While nitrate-nitrogen concentrations were greatest in
the raw-limed sludge, there was less nitrate-nitrogen 30 to 60 cm below
in the soil than under the 60 cm deep digested sludge trench.
Biological denitrification requires an organic energy source and low
oxygen levels. Greater levels of organic materials moved into the soil
from the raw-limed than from the digested entrenched sludges and pro-
vided a greater potential for denitrification. Originally, oxygen
concentrations were rather low under the trenches, but they increased as
the sludges dewatered.
There has been little nitrogen movement from the digested 120-cm deep
trenched sludge. Digested sludge in the 120-cm deep trenches has not
dewatered to as great an extent as in either the raw-limed or digested
60-cm deep trenches. Thus, any small amount of nitrate that may have
formed was not subjected to much leaching and probably was denitrified.
It is not known how much nitrogen may later move from the 120-cm deep
trenches as more dewatering of the digested sludge occurs or how fast
the dewatering will occur. From the standpoint of nitrogen movement and
loss after 18 months of study, digested sludge should be placed in the
deep trenches. From a crop benefit standpoint, however, the 60-cm deep
trenches with the 60-cm spacing between the trenches was best. In the
soil at the test site it was not advisable to narrow the spacing between
the 120-cm deep trenches more than the 120-cm edge to edge spacing used
because of potential trench wall collapse, when digging and filling.
In contrast to the 120-cm trenches filled with digested sludge, nitrate-
nitrogen movement was appreciable under a 120-cm deep raw-limed liquid
sludge trench. Here there was close contact between the soil and sludge.
This promoted rapid microbial conversion of the sludge nitrogen to the
mobile nitrate form. Conditions for appreciable loss of nitrogen by
denitrification were apparently unfavorable.
CHLORIDES AND CONDUCTIVITY
Elevated chloride concentrations, but still within drinking water
standards, were detected in 3 of 40 test wells. These chlorides appar-
ently came from the entrenched sludges. Elevated conductivities, indica-
ting increased salt concentrations, were detected sporatically in
several of the wells and may have resulted from surface contamination
rather than from contamination from entrenched sludges.
-------
Chloride moves through the soil at about the same speed as nitrate.
While chloride is immediately present in sludge, nitrate must be formed
biologically. Furthermore, nitrate can be lost 'to the atmosphere by
denitrification. Therefore increases in chloride concentrations appear
to be a good indicator of the potential contamination in groundwater
from entrenched sludge, but increases in chloride concentration does not
necessarily mean that nitrate contamination will follow.
PATHOGEN MOVEMENT
There was no detected movement of fecal coliform or salmonella bacteria
out of the entrenched sludge into the surrounding soil or down to the
groundwater. Since viruses were not detected in the entrenched sludges,
movement of viruses from the trenches in the field was not measured.
The movement of polio and bacterial viruses with percolating water was
studied in the laboratory utilizing disturbed columns of the coarse-
textured soil from the trenching site. The soil columns were capable of
removing large quantities of viruses from percolating water, but rapid
leaching of the columns after application of large quantities of viruses
resulted in some virus transport through the columns. From the results
of the column studies, the quantities of water required to move viruses
in a similar way in the field to a water table at 150 cm (5 feet) of
depth greatly exceeded that expected in normal rainfall events.
Subsequent adsorption of any dispersed virus by the soil should limit
further movement during later rainfall events.
Viruses have been found even in anaerobically digested soil sludge by a
number of investigators, but the quantities present are much lower than
the amounts applied to the soil columns in our studies. Thus if all the
viruses were released from a sludge applied to soil in this study, the
relatively great amount of adsorptlve soil surface would preclude viruses
reaching the groundwater under any reasonable rainfall pattern. Other
adsorption studies, in our laboratory, however, have shown that not all
soils are capable of adsorbing viruses. As an added precaution against
viruses moving into groundwater, an entrenchment site should be chosen
that contains a soil capable of adsorbing viruses. The mechanism of
virus sorption as yet has not been defined for soil and is under study.
PATHOGEN PERSISTENCE
Liming raw sludge to a high pH decreased tremendously the numbers of
salmonella and fecal coliform bacteria. Several months after entrench-
ment, the sludge pH dropped and these organisms increased in number.
This increase was only temporary and their numbers soon began to
decrease with time. Salmonella bacteria persistence was for less than
10 months. Total and fecal coliforms greatly decreased in numbers with
time, but low levels of these organisms were still found after 2 years.
While only the salmonella bacteria are pathogens, their potential for
producing disease due to their presence in the trenches in a well managed
site should be extremely low. We did not measure persistence of other
-------
human pathogens in the entrenched sludge. Most human pathogens, once
reduced to very low numbers by liming or some other process, cannot
reproduce outside the human host.
HEAVY METALS
The metal contents in samples of sludge composted over 24-hour periods
at Blue Plains varied considerably over the 2-year period covered by
this study (zinc - 1610 to 2340 ppm, copper - 650 to 720 ppm, nickel -
46 to 94 ppm and cadmium - 13 to 24 ppm). On the other hand variation
in metal contents of 24-hour composites taken over a one week period
were very small. Variation in the metal content of individual grab
samples of sludges taken at different times during 24-hour periods were
of the same order of magnitude as the variation observed in the com-
posted samples over the two-year period. Hence, it is necessary to think
in terms of average metal content in sludges. Metal concentrations
determined in a properly taken 24-hour composite sample were a good
representative average.
There was essentially no movement of zinc or copper out of entrenched
raw-limed sludge. On the other hand, some movement of zinc occurred
from the shallow but not the deeper digested sludge trenches. This
movement of metals from the shallow entrenched digested sludge seemed to
be associated with aerobic decomposition of the sludge accompanied by
oxidation of large quantities of ammonium to nitrate and a resulting
reduction in pH of the sludge and surrounding soil.
Heavy metal uptake in the crops from the entrenched sludges did not seem
to be excessive in preliminary tests. For example, zinc contents in
fescue were 91 ppm growing over 60-cm deep digested sludge trenches, 31
ppm growing over 60-cm deep raw-limed sludge trenches, and 50 ppm in an
entrenched control area without sludge. The lower concentrations of
heavy metals and the elevated pH which insolubilized metals probably was
responsible for less uptake by fescue from the entrenched limed un-
digested sludge relative to the digested sludge. Relative to the con-
trol, the lower uptake may have been a result again of the higher pH
which insolubilized metals. Also sludge phosphates and organic matter may
have sequestered soil metals making them less available.
As the entrenched sludges became aerobic, DTPA-TEA extractable metals
increased. Extractable copper increased 8-fold changing from the sul-
fite to the sulfate form. Research is underway to determine if metals
like zinc and copper become more available to plants as the sludge
decomposes in trenches.
In laboratory studies, a wide range of metal tolerances among different
species of crops were observed. In general, grasses were most tolerant
and absorbed the least amount of metals. Vegetables were least tolerant
and absorbed high quantities of metals. Zinc and cadmium were absorbed
and readily translocated to plant tops while copper was not. In excess
in plants, these metals interfere with iron uptake-transport and cause
-------
stunting of plant roots and tops. Soil and sludge pH was the most
important single factor affecting metal availability to plants. At pH 7
metals were perhaps ten times less available and toxic to plants than at
pH 5. A second important soil factor was cation 'exchange capacity. At
a higher cation exchange capacity, more metals are held and are less
available to plants. Hence, trenching sites can be managed to reduce
metal uptake by selecting tolerant crops, liming to neutral pH, and
selecting soils with higher cation exchange capacities.
TRENCH SIMULATION
Simulated trenches of sludges in boxes permitted detailed studies over a
shortened time period. The results revealed (a) more rapid root pene-
tration by corn roots into digested than raw sludge, (b) an anaerobic
period in the entrenched sludges and in the soil below prior to root
penetration, (c) little, if any, water movement directly through
entrenched sludge before dewatering by roots or shrinking and cracking,
and (d) the likely occurrence of denitrification in digested and raw
sludge with less nitrification and/or greater denitrification under the
raw than digested trench.
There was considerably more ammonium movement out of raw-limed trenches
in the laboratory than observed in the field. This possibly resulted
from irrigated water dissolving ammonium at the sludge surface and then
bypassing the soil below by moving through the box soil interface.
As in the field there was little if any movement of metals out of
entrenched sludge. Fecal coliform and salmonella bacteria, which have
the ability to grow outside their hosts, grew to detectable levels in
the high pH sludges only after the sludge pH decreased.
LIMING SLUDGE
Liming sludge at the time of dewatering at the wastewater treatment
plant to a pH of approximately 11.5 was desirable because it reduced the
levels of pathogens in the sludge. Liming was also desirable because
movement of metals out of entrenched sludge into soils was minimized,
and metal uptake by plants was reduced. In addition to these process
effects, lime is needed in most of our Eastern United States' soils for
good crop growth.
ESTIMATED COSTS
The costs for entrenching dewatered raw-limed sludges obtained from Blue
Plains during interim treatment (400 filter cake tons per day) were
estimated by a consulting firm. Operating and capital costs were
estimated at approximately $10.00 per filter cake ton ($50.00 per dry
ton) with capital costs amortized over a 2-year period. The costs did
not include sludge transport.
-------
SECTION II
RECOMMENDATIONS
GENERAL
Trenching is a suitable procedure for high rate disposal and application
of sewage sludge to land. Trenching is an appropriate system to use
when low-rate (fertilizer-rate) surface application of sludge is not
feasible, e.g., with undigested (raw) sludge. Properly used, trenching
is environmentally safe and compatible with use of the land for some
agricultural purposes. Trenching is not appropriate in some prime agri-
cultural land because of subsoil being brought to the surface and the
amount of trace elements applied. However, since the effects of
trenching have been studied for a short time under limited conditions,
any immediate plan to use trenching in large scale land application of
sludge should include careful monitoring.
DESIRABLE SITE CHARACTERISTICS
A good site should have: a deep water table or a substratum suitable
for establishment of a drain system, a good location for a holding pond,
good vehicular access, a rural location as near to the sludge source as
possible, slopes less than 10 to 15 percent where sludge is to be
applied, and soil of marginal agricultural value — first choice would
be a heavy soil underlain with an impermeable stratum. Sites with sandy
soils may be helpful for wet weather operations. It also may be neces-
sary to construct temporary field roads and to pump sludge for all
weather operation. If fissured rocks are present, they should be at
least three meters (ten feet) below the surface.
SURVEY
To determine its suitability, the potential trench application site must
be studied carefully to characterize: (a) the surface and subsoil pH,
texture, and cation exchange capacity; (b) the topography; (c) the
distance to fissured rock; (d) location of any hard, impervious layers;
(e) location of permanent and perched water tables; (f) the direction
and flow of underground waters; (g) potential for underground drainage;
(h) areas for suitable waterholding ponds; and (i) adequate access for
heavy trucks and other field equipment; and (j) test trenches to deter-
mine ease of digging and side wall stability.
SITE DRAINAGE
When the water table is shallow, as a minimum safety precaution, a
perimeter drainage network should be installed with an average depth of
120 to 150 cm (4-5 feet). In climatic areas with appreciable rainfall,
-------
pond storage capacity should be able to hold drained water for approxi-
mately two months. If contaminated, the water could be applied on
surrounding land for purification by crop utilization and percolation
through soil. Drainage and surface water control'should be under the
guidance of an agency like the Soil Conservation Service.
TRENCHES
Trenches should be dug on the contour. The trenches should then be
covered the same day that they are filled. A trenching machine should
have cleated tracks and a rear-mounted digging wheel that is movable
from side to side and tiltable. For maximum benefit and decreased
nitrate hazard, limed sludges should be placed in trenches no more than
75 cm (30 inches) deep and 60 cm (24 inches) wide and 60 to 75 cm (24 to
30 inches) apart edge to edge. Sludges placed in narrow trenches (less
than 60 cm (24 inches) wide) would result in greater soil sludge contact
and more aerobic conditions. Narrow trenches would probably favor more
rapid nitrification with less denitrification, and consequently increase
the danger of nitrate pollution of groundwater.
SLUDGES
Dewatered sludges should be entrenched at high disposal rates (350 dry
metric tons/hectare) when surface application and mixing into the soil
surface at fertilizer or soil conditioning rates (25 to 125 dry metric
tons/hectare) is not possible. The low-rate application of sludge to
the soil surface compared with high-rate application in trenches would
yield better agricultural benefit of sludge nutrients and avoid the
potential movement of nitrate and excessive metal accumulation in soils.
Undigested primary or secondary sludges should first be limed and
dewatered before entrenchment. The pH of the sludge at dewatering
should exceed 11.5 to reduce survival of pathogens and to lower the
potential for metal accumulation by crops. The metal content of sludges
should be known and be as low as possible to further decrease potential
for excessive uptake of metals by crops.
Undigested sludges unless stabilized should not be applied to land
except in trenches because of the potential pathogen hazard and odor
problem associated with surface incorporation. Metal content is less,
and apparently risk of nitrate movement is less from a given volume of
undigested than of digested entrenched sludge from the same wastewater
treatment plant.
HAULING AND FILLING
A sealed concrete mixer type truck is recommended for hauling the sludge
from the wastewater treatment plant to the trench incorporation site.
This truck could also then be driven directly to the trenches when the
soil is dry and capable of bearing the load. The sludge with up to 30%
solids content could then be unloaded from the concrete truck via its
-------
own extended discharge chute. In wet weather, the concrete truck could
discharge the sludge into a trailer outfitted with a peristaltic type
pump. A bulldozer could then pull the high flotation trailer near the
trench so that the sludge could be unloaded via the pump through pipe
and flexible tubing into the trenches.
PREPARATION FOR SEEDING
To prevent erosion and permit soil stabilization, the trenched area
should be left ridged until weather is suitable for leveling and seed-
ing. When leveling freshly filled and covered trenches, a bulldozer or
some other suitable tracked vehicle should be used at right angles to
the trenches. Deep cross-ripping of the entrenched sludge is unneces-
sary in sandy soil. Its possible benefit should be determined in clay
soil. Based on soil tests and the crop to be grown, fertilizer and lime
should be applied and worked into the soil surface. The lime and ferti-
lizer requirement could be reduced by surface application of approxi-
mately 25 to 60 dry metric tons/hectare (10 to 25 dry tons/acre) of
digested dewatered sludge.
CROPS
Crops should be limited to grass the first year. Initially the trenches
can be leveled and cultivated only at right angles. If row crops are
subsequently grown, they should be planted on the contour to prevent
excessive erosion. Because of uncertainty on availability of metals to
crops grown on trenched soils, the crops should not be used as food
until analyzed to determine their safety.
MONITORING
Since little is known about the long-term effects of trenching on the
environment, monitoring for environmental impact of large-scale trenching
operations is essential and should be the responsibility of a qualified
trained individual working for a governmental institution, such as the
State Department of Health. Until long-term background data is accumu-
lated, monitoring should begin before sludge is applied and continue for
at least five years after application. The suggested level for classi-
fication as a large-scale operation is 10 tons of sludge (dry weight
basis, population of 100,000) or more per day. Monitoring needs for
small-scale operations (less than 10 dry tons per day) would be very
site specific. Thus the monitoring requirements for small operations
should be determined on a case by case basis and should be proportional
to the magnitude of the specific local environmental risk.
For large-scale operations background samples should be taken from
strategically located groundwater wells a month or two before sludge is
applied. These wells should be located both inside and on the down flow
side of the underground water coming from the entrenchment site. The
minimum background analyses should include some of the following determ-
inations: fecal coliforms, PCB's, chlorinated hydrocarbon pesticides,
-------
alkalinity, organic nitrogen, nitrate-nitrogen, ammonium-nitrogen,
chlorides, pH, COD, zinc, cadmium, copper, and specific conductivity. A
similar analysis of the critically located wells for the background
parameters should be made 6 to 12 months after sludge incorporation and
then yearly for at least five years if contamination is indicated. Water
in all wells should be sampled monthly to trimonthly depending upon
location, and analyzed for chloride and nitrate-nitrogen. Increased
concentrations of chloride would probably be the first indicator of
sludge contamination in wells.
At least two sets of background analyses, preferably at three-month
intervals, may be made of some of the residential wells located within
perhaps a 1.6 kilometer (one mile) radius of the area of sludge entrench-
ment.
Composite samples should be collected and analyzed from streams draining
the area, from major subsurface collector lines draining the area, and
from ponds holding drainage water. This sampling should begin two
months before sludge application, continue at monthly intervals there-
after, until one year after all sludge has been incorporated, and then
periodically for two to four years. Minimum analyses of these samples
should include fecal coliforms, pH, dissolved oxygen, COD, chloride, and
nitrate-nitrogen.
Before sludges are entrenched, they should be continuously monitored
during each day for pH at the treatment plant. At the time of dewater-
ing the pH should exceed 11.5.
Crops grown on the trenching area should be sampled and analyzed annually
for at least five years for uptake of zinc, copper, cadmium, nickel,
lead, and mercury. The same crops grown on nearly similar soils should
be similarly analyzed as a control.
RESEARCH
A portion of the funds for trenching operations should be allocated for
research to determine the environmental effects of even larger scale
trenching operations than previously studied. Research should be dir-
ected to determine the hazards of surface and ground water pollution
caused by using various kinds of sludges in various types of soils and
to obtain the optimum trench dimensions for maximum leaching with mini-
mum damage to the environment. More information is needed on how these
factors influence pathogen survival and movement, nitrogen mineraliza-
tion and movement, the fate of sludge borne trace elements toxic to
plants and animals, and the growth of crops.
SUMMATION
These recommendations on trenching procedures are based on data from
experiments over a relatively short time. We believe, however, that
this research shows that dewatered sludge can be trenched safely by
10
-------
following our present recommendations. The most likely difficulty is
that excessive nitrogen from the sludge might reach underground water.
This nitrogen problem can be minimized by underdraining the entrenchment
site and retaining the drained water for irrigation of surrounding land
or by choosing soils through which movement is- minimized.
11
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SECTION III
INTRODUCTION
The lack of acceptable procedures for sewage sludge disposal limits the
effectiveness of wastewater treatment.
In general better wastewater treatment generates more sewage sludge
requiring disposal. The situation at the Blue Plains wastewater facil-
ity, which serves two million people in the Metropolitan Washington,
D.C. Area is a good illustration.
Federal regulations require that Blue Plains institute interim and ulti-
mately advanced wastewater treatment to reduce the solids entering the
Potomac River in its treated effluent. The Blue Plains plant treats
approximately one million cubic meters (300 million gallons) of waste-
water per day and, in 1971, generated between 200 and 300 tons (40 to 60
tons of solids) per day of digested sewage sludge. This was combined
sludge, from primary and modified waste activated (secondary) treatment
of the wastewater, which had undergone high rate anaerobic digestion for
an average of 14 days at 35°C (95°F). This combined sludge before
digestion will be referred to as raw or undigested sludge in this report,
and after anaerobic digestion as digested sludge. By instituting full
interim treatment (addition of chemicals to remove phosphate as well as
solids), the amounts of raw sewage sludge generated would at least
triple. With full advanced treatment, raw sludge levels will increase
even further.
Prior to 1973, the Blue Plains plant digested and then held their diges-
ted sludge on a drying field before ultimate disposal on land. The
field has since been used for new plant construction. Additional
digestors are not being built because incineration was the planned
method of sludge disposal when full advanced wastewater treatment was
realized. Blue Plains has been unable to institute interim treatment on
any regular basis because environmentally and/or politically acceptable
alternatives did not exist for disposal of the resulting raw sludges.
Disposal in landfills has been prevented because sites are unavailable
and because landfilling raw sludge in large quantities is particularly
difficult.
The District of Columbia Government (DC); the Environmental Protection
Agency (EPA); the Maryland Environmental Service (MES); and other State,
County, and local agencies and groups launched a cooperative effort with
the Agricultural Research Service (ARS) of the United States Department
of Agriculture, to find an environmentally acceptable procedure for
sewage sludge disposal that also is beneficial to soil and crops. Early
in 1972, ARS scientists, in cooperation with these other agencies, began
a comprehensive research-demonstration study on evaluating the trenching
12
-------
of raw and digested sewage sludge as a means of improving the agri-
cultural potential of marginal soils and at the same time providing an
economically feasible, environmentally sound, and politically accept-
able alternative for sewage sludge disposal. These studies included:
(1) large-scale field trial to determine feasible all-weather procedures
for hauling and incorporating sewage sludge into the soil in trenches;
(2) characterization of the site prior to treatment with respect to its
hydrologic properties and the biological and chemical properties of the
surface and underground water and the soils; (3) testing of a drainage
control system for the site; (4) establishment of a monitoring program
by which the movement, form, persistence, etc., of sludge nitrogen,
heavy metals (zinc, copper, cadmium, nickel, etc.) and pathogens could
be followed in ground and surface water and in plants growing on the
site after sludge incorporation into the soil; and (5) supportive
laboratory and greenhouse studies.
This cooperative project was formally initiated on April 20, 1972, by
signing of Contract No. 72374 between Maryland Environmental Services
(MES) and the Government of the District of Columbia (DC), and Coopera-
tive Agreement No. 12-14-100-11, 191(41) between MES and the Agri-
cultural Research Service (ARS). The research covered in this report
was conducted from January 1972 to January 1974.
13
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SECTION IV
FIELD ENTRENCHMENT OF SLUDGE
SITE CHARACTERISTICS
The experimental site was selected only after inspection of several
possible sites. The 35-hectare (75-acre) site selected offered excel-
lent possibilities for soil improvement by sludge entrenchment, for
monitoring, and for drainage control. It was readily accessible to
heavy equipment, distant from residential development, and because of
its very sandy textured soils offered a sensitive test for movement of
pollutants from entrenched sludge into the groundwater.
Survey of Groundwater and Underlying Impervious Clay
Beginning in December 1971, about 50 soil borings were made by the
Maryland Department of Natural Resources. Thirty of these borings were
used to map the water table and underlying impervious clay layers. About
40 were later used as access wells into the groundwater for study of
possible contamination from the sludges. Pertinent boring data used to
locate drain lines, pond, and sludge incorporation sites are given in
Table 1. The locations of approximately 25 wells are shown in Figure 1.
Water tables below the plot sites varied approximately as shown in Table
1. The water table remained quite high during 1972 because of the
unusually high amounts of rain.
The water table and underlying impervious clay layers are shown in
Figure 2.
Tile Drainage and Pond Installation
Based upon the groundwater profile in Figure 2, diversion drains were
installed along the east and west edges. A drainage catchment pond was
also constructed down slope with sufficient capacity to hold about one
month's normal drainage from the site. Location of drains and pond are
shown in Figure 1.
Test ditches showed that because the soil was so sandy (Table 2) and
wet, open ditches for conventional tile laying would collapse. There-
fore a special trenching machine was used with shields behind the trench-
ing wheel. This machine from Robert Vincent Company, Inc., automatically
laid a 10- or 12.5-cm (4- or 5-inch) corrugated slotted plastic drain
tube (Figure 3). A laser beam guidance system permitted accurate place-
ment of the line on a 0.1 and 0.2% grade. Before the drain tube was
installed it was wrapped with a fine-mesh polypropylene screen (polyfiber
"GB") to prevent sand-clogging. Plastic drain tubes with screening as
part of the fabrication have become available commercially since the
installation of the drainage system.
14
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(Approx. Scale -- 1 cm = 24 m)
Wooded
m / 24
/ Plot 16 /
]62
Figure 1. Partial site map.
-------
' Soil Surface
r^ Water Table
_^V v^ Impermea^/e Boundary
90 .
Distance. (Meters)
(A) East-West
Figure 2. Soil surface, water table, and impermeable
soil boundary locations determined
in January 1972.
16
-------
Soil Surface-+Q*£_
Wafer Table-+B---
ITm permeable
_5.C.S
/«?0 oZVO 300 360
Dfstance (/defers)
4-3.0
(B) South-North
Figure 2 (continued) Soil surface, water table, and
impermeable soil boundary locations
determined in January 1972.
17
-------
Figure 3. Tile installation
18
-------
Table 1. GROUNDWATER WELLS - DEPTH AND WATER LEVELS - 1972-1973
4
Well
No
1
2
3
4
5
6
7
8
9
10
11
12
13
14
16
17
18
19
20
21
22
23
24
26
Oft
£v
**n
Jv
31
oo
J^
34
36
61
62
63
40
42
44
46
48
er\
J\J
52
54
55
r
To
bottom
13.4
10.4
8.2
6.9
4.4
1.5
8.6
10.2
10.3
6.9
4.9
12.2
7.3
8.3
4.8
4.8
7.9
4.1
6.2
3.0
2.6
4.1
3.8
14.6
-it c
!_>._>
1 A ^
1O . j
17.1
5C
. ->
8.5
5.4
11.6
11.7
12.3
5.4
4.9
4.1
5.9
5.6
1 Q 1
1J. 1
4.1
4.1
4.0
To
impervious
layer
11.2
9.1
10.7
7.4
2.0
1.4
8.0
8.8
13.4
5.1
1.9
6.3
6.6
6.2
1.5
2.5
5.7
2.2
4.4
1.9
1.9
1.9
1.4
13.3
On
. 7
-Ofi c;
^tLO • «>
?
-»^ R
**J.O
>5.8
3.8
10.1
11.0
>12.2
3.7
3.7
3.4
4.6
3.0
01
. 1
3.7
1.4
>3.7
Depth
**
Of grout
4.3
3.0
3.4
2.4
2.4
0.6
3.0
3.6
3.6
2.4
1.2
2.7
3.6
3.6
1.2
1.8
3.0
1.8
2.1
1.5
0.3
1.8
1.8
1.2
_ J_
~ ~ " T
_ _l_
* i
4.0
3C
• O
3.6
3.6
3.0
3.0
4.0
2.7
2.4
2.1
3.0
3.0
--- +
2.1
2.1
2.1
in mete
Jan
72
9.0
8.2
5.9
3.0
0.8
0.1
6.2
7.6
8.5
4.6
1.2
5.5
5.7
6.6
0.9
2.3
6.1
2.3
2.7
0.9
1.1
0.8
0.8
10.2
J.»
ory
j
cry
._-
4C.
• D
7.5
2.1
...
...
_ _ _
— — —
rs
June
72
9.1
8.0
5.9
3.1
1.4
0.2
5.9
7.6
8.5
4.5
2.0
5.7
6.3
1.3
2.3
5.9
2.4
2.1
1.4
1.6
1.5
1.3
10.1
j
ory
j
cry
13.5
j
ory
7.0
2.4
5.7
7.6
9.2
0.8
1.2
1.0
1.7
1.7
i
ory
2.0
0.2
1.2
To water
Oct
72
9.8
8.5
6.6
3.8
1.9
0.5
6.7
8.4
dry
5.9
2.6
6.2
6.5
7.2
2.0
3.0
6.9
3.6
3.5
2.0
0.9
2.3
1.5
10.9
13.7
7.9
3.4
6.8
8.6
10.1
0.6
2.7
0.6
0.9
2.8
3.5
0.4
2.0
surf a
Jan
73
9.1
8.1
6.1
3.3
1.2
0.1
6.2
7.8
8.7
4.6
1.1
5.5
5.9
6.6
0.9
2.3
6.0
2.2
2.5
0.9
0.2
0.8
0.5
10.6
13.7
7.4
2.2
6.4
8.3
9.9
0.3
0.5
0.2
0.5
0.4
0.8
0.1
0.6
ce
June
73
8.9
8.0
6.1
3.2
1.5
0.7
6.1
7.7
8.5
4.6
2.2
5.4
5.8
6.5
1.2
2.3
6.0
2.5
2.7
1.3
1.5
1.6
1.2
10.3
13.5
7.2
2.4
5.9
7.8
9.4
0.8
1.2
1.0
1.6
1.4
1.8
0.6
1.3
Oct
73
9.6
8.4
6.5
3.7
1.9
1.1
6.7
8.4
9.1
4.9
dry
6.1
6.2
6.8
2.1
3.0
6.6
3.4
3.4
2.7
2.8
2.5
10.9
13.7
7.9
3.5
7.0
8.8
10.3
2.3
4.0
2.5
3.3
4.0
3.8
1.8
2.8
* See Figure 1 for well location.
** Filled with sand to grouting depth before grouting.
+ Not grouted.
19
-------
Table 2. ANALYSES OF SOILS FROM TEST TRENCHES
Location
Near well 4
245 m back along
drain tile & ditch
along gravel road
*
Sample
Depth, cm
5
6
7
8
9
10
0-15
30-75
90-150
210-240
20-38
60-75
Total % sand
Near well 6
1
2
3,
4
20-30
90-120
150-250
210
74
87
86
81
63
82
94
100
63
27
* Samples 1-8 were from areas that caved in and samples 9-10 did
not cave in»
The pond was designed by the Soil Conservation Service, USDA, and built
by the Agricultural Research Center. It is approximately 0.4 hectare
(1 acre) in area and 165 cm (5.5 feet) deep (3760 cubic meter (1 million
gallon) capacity, equivalent to about 1 month's drainage.) A stand pipe
outlet 30-cm (12-inches) in diameter and valved bottom drain 20~cm
(8-inches) in diameter were installed to regulate the pond water level.
The two drain lines shown in Figure 1 drained directly into the pond. In
addition a diversion terrace was built to direct surface runoff into the
pond from the east side. Surface runoff from the west half of the plot
area was intercepted along the access road and diverted into drain line
"B" by means of a gravel sump. Hence, line"A" emptied only underground
water into the pond, whereas line "B" also handled surface runoff.
Soil Characteristics
The entire region to the south and including much of the plot area
consisted of sandy soils. Specific soil types in the plot areas, as
determined from the Prince. Georges County Soil Survey Report and by
mechanical analyses, are given in Table 3. The sandy soils in plots la-
IVa (Figure 9) were generally deeper than those in plots Ib-IVb which
were underlain more closely by clay. The range in depths and texture
present permitted trenching in soils of somewhat different character-
istics. In general, infiltration rates of rainwater into these porous
sandy soils were high and provided a rather severe test for movement of
20
-------
Table 3. SOILS AND WATER TABLE IN PROPOSED PLOT AREAS
Plot
Proposed treatment
width x depth Number
x edge to edge
cm
Digested
60 x 60 x 60 la
Digested
60 x 120 x 120 II a
Raw- limed
60 x 60 x 60 in a
Raw- limed liquid,
60 x!20 x 240 IV a
Control,
60 x 60 x 60 v a
Digested
60 x 60 x 60 i b
Digested
60 x 120 x 120 II b
Raw- limed
60 x 60 x 60 III b
Raw- limed liquid,
60 x 120 x 240 IV b
Soil analysis**
Depth to
GrOundwater Clay
m
0.8-4.
1.8-4.
0.8-1.
1.8-4.
0.6-2.
0.5-1.
1.1-2.
0.5-1.
1.1-1.
,6
6
4
6
1
5
4
5
5
m
1.8-4.6
3.4-5.2
1.5-1.8
2.1-4.6
0.9-2.1
0.6-1.5
1.5-2.4
0.9-1.5
1.2-1.5
*
Soil type
Mostly GeC
a little KeB2
GeC
GeC
GeC
GeC
Mostly KeB2
a little GeC
StB2
Partly StB2
partly KeB2
Mostly StB2
a little KeB2
PH+
5.3
5.2
5.0
5.1
5.4
5.6
5.2
5.0
5.2
Total N
^g/g
282
318
323
276
334
379
271
334
285
++ Soil fractions**
0,
c
i
0.
0.
0.
0.
0.
0.
0.
0.
0.
,M.
I
36
39
55
29
62
69
34
39
31
Sand
%
80
74
77
78
81
79
68
74
74
Silt
°L
15
18
15
15
13
15
24
20
18
Clay
%
5
8
8
7
6
6
8
6
8
Continued
-------
Table 3 (continued). SOILS AND WATER TABLE IN PROPOSED PLOT AREAS
Plot
Soil analysis
Proposed treatment Depth to
width x depth Number Ground-water Clay
x edge to edge
Soil type3
PH + Total
Soil fractions *+
O.M. Sand Silt Clay
Control,
60 x 120 x 120
Control,
60 x!20 x 120
Pond
V b 1 2.4-4.6 3.7-5.5 GeC
V b 2 1.5-2.4 1.8-2.4 StB2
0.1-0.5 0.3-0.8 Ek
5.2 316
5.4 210
0.46 75 16
0.27 72 18 10
* Soil type code from Soil Survey Manuel for Prince Georges County: GeC = Galestown - Evesboro sandy loam;
KeB2 = Keyport find sandy loam; StB2 = Sunnyside fine sandy loam; Ek = Elkton silt loam.
** Sampled to depth trenches were to be dug.
+ Analyses by USDA-ARS, Beltsville, Maryland.
++ Analyses by USDA-ARS, Beltsville, Maryland on dry weight basis.
*+ Analyses by USDA-ARS, Beltsville, Maryland, and USDA-SCS, Beltsville, Maryland.
-------
pathogens and nitrogen into groundwater. The soils were moderately to
strongly acidic. The soil in the pond area was an excellent fine-
textured material for pond building with very low seepage.
Wells
All the wells in the immediate plot area were drilled, grouted and
sampled in April before sludge incorporation.
Drilling—A drilling rig with 15-cm (6-inch) augers, operated by the
Maryland Department of Natural Resources, was quite suitable for making
borings and taking boring samples up to a depth of about 15 meters
(50 feet). After drilling each well, a 5 - cm (2-inch) diameter poly-
vinyl chloride (PVC schedule 40) plastic pipe was installed into the
well. Each pipe was slotted at 7.5 cm (3-inch) intervals over a 150 cm
(5 foot) distance at the bottom, and the bottom end capped. A diagram
of a well in cross-section is shown in Figure 4.
Grouting
After drilling the wells and casings were covered with plastic until
they were grouted. The grouting procedure was recommended by Elmer
Jones, ARS, Beltsville, Maryland. It consisted briefly of mixing Type 3
Portland cement for 10 to 15 minutes in a mortar mixer using exactly 10
parts cement to 6 parts water. The cement was then screened through
0.6 cm (0.25 inch) hardware cloth into a large container which had a
3.2 cm (1.25 inch) clear plastic drain line in the bottom. The con-
tainer, which was in a pick-up truck, was then driven to the different
wells. The cement-water mixture flowed freely from the container and
remained quite fluid (suitable for grouting) for several hours. Just
prior to grouting, sand was packed around the plastic casing to grouting
depth as given in Table 1. A funnel connected to a 3.2 cm (1.25 inch)
pipe 240 cm (8 feet) long was inserted into the 15 cm (6 inch) bore
hole on the outside of the 5 cm (2 inch) casing. The cement grout was
then poured into the funnel through a 0.6 cm (0.25 inch) hardware cloth
screen (Figure 5). By grouting in this manner, water samples were
pulled from the entire water table through the sand around the casing.
If water were to be sampled from a specific location in the water
table, grouting was installed to nearly that depth with the casing open
only at that depth. The cement grouting was used to prevent surface
water from running down the outside of the casing. Except in well 22
the procedure was very successful in achieving its purpose. Well 22,
with an unfavorable ratio between cement and water, was grouted too
shallow, cracked and allowed surface water penetration as shown in
Figure 6.
Sampling -- Water was sampled from the wells for chemical and biological
analyses by a. sampling system shown diagrammatically in Figure 7 and
pictorially in Figure 8. The plastic-covered weight, tubing, glass T
and cap (all 0.9 cm (0.38 inch)ID) were sterilized in an ethylene oxide
chamber prior to being permanently placed in each well. Initially a
23
-------
Grout
(15-33 cm)
in soil
Slots
(150 cm)
in aquifer
f Syringe Cap
To Vacuum
""*""'*—'—• Glass T
""""'"— --— End Cap
_— — - -___. _ .. _ ,. — PVC Well Casing
Flexible Vinyl Tubing
Water Inlet Holes
(5 mm I.D.)
Sealed PVC Pipe
Around Weight
Slots for Water Intake
•-+'JL^LJ^— ^^—,- End Cap
Figure 4. Well cross-section with water sampler.
24
-------
Figure 5. Pouring cement grout around well casing.
25
-------
Figure 6. Grout failure on well 22,
26
-------
150 c
Sterile Syringe (30 ml.) (water for bacterial analysis)
Rubber Syringe Cap
Vinyl Clear Flexible Tubing (0.9 cm I.D. x 1.6 cm O.D.)
v 1
Glass T
(0.9 cm I.D.)
Vise-Grip Clamps
Vacuum
Pump
110 V
1/3 HP
Cotton
Drierite
4 liter Filtering .
Flask Filtering Flask
(water for viral and Clic^uid and/aPor
chemical analysis) water trap)
Generator (gasoline-
powered) 1200 watts
Figure 7. Water vacuum sampling system.
-------
Figure 8. Well sampling.
28
-------
volume of water was withdrawn from the well equal to that contained in
the casing and then discarded. Then the tubing was clamped off below
the glass T and a 90-ml water sample was withdrawn through a rubber
serum bottle cap with a 30-ml disposable syringe and 18 gauge needle.
For this purpose there were about 150 cm (5 feet) of tubing between the
well cap and the glass T outside the well. The serum bottle cap surface
had been sterilized with alcohol prior to insertion of the sterile
syringe needle. The sample was collected into the syringes and ejected
into a sterile bottle. This sample was saved for total coliform, fecal
coliform, and in some cases salmonella analyses. For Large samples for
virus and chemical analyses the clamp was removed, suction reapplied,
and a 4-liter filtering flask filled with sample water. These large
samples were placed in 1.9- and 3.8-liter (1/2-and 1-gallon) plastic
milk cartons, capped and refrigerated until analyses were made. A 7.5-
cm (3-inch) casing, which would provide a larger volume of accumulated
water and permit sampling by bailing as well as by vacuum, might prove
more useful for future wells.
SLUDGE INCORPORATION
Two separate discussions of sludge entrenchment are included in this
report. The first is written from an engineering viewpoint and the
second from an agricultural and environmental research viewpoint.
Engineering Report by Whitman, Requardt and Associates (WR&A)
Introduction — The Sludge Utilization Pilot Project performed at the
Agricultural Research Center in Beltsville, Maryland, was conceived as a
means of developing a safe and efficient manner for tilling sludge into
the soil using standard items of equipment readily available on a rental
basis. In addition, the project was planned to provide soil scientists
at the U.S. Department of Agriculture Plant Industry Station an oppor-
tunity to compare the effect upon crop production of the treatment of a
sandy soil with a variety of sludges applied at various dosage rates.
The prime effort was directed toward simulating as nearly as possible
the full-scale full-time operation at Cheltenham, Maryland, planned for
the interim treatment period at the Blue Plains Plant.
Site Preparation and Maintenance — Before beginning actual operation,
the plots were laid out in the field. The layout permitted a comparison
on a plot-to-plot basis of the operation of equipment in two slightly
different types of soil. All of the entrenching studies were performed
in each type of soil by dividing each of the plots into two parts as
shown in Figure 9. The field layout was selected to provide adequate
access to all plots and to shield, as much as possible, the sampling
wells from the expected traffic flow pattern. Two access roads to the
plots were constructed with bank run gravel, and a road was prepared to
provide for one-way traffic around the field site. A terrace, which ran
through all of the plots, was leveled to facilitate the operation of the
equipment.
29
-------
Tr Number of Trenches
Leveling, Disking and Rippino
Leve/inq and ^ ' '
Left
In Ridges
Back-filled
Figure 9. Plot dimension and tillage.
-------
During the course of the project, the main one-way route was graded as
much as possible to allow free flow of traffic. However, excessive
amounts of rain and heavy traffic during the project at times made
portions of the road impassible. The application of bank run gravel to
the road provided only a temporary solution between rain showers.
Finally, with the addition of a large amount of crusher run gravel
(especially at low spots where trapped surface water made the base
spongy), the road was reconstructed to better than its original con-
dition.
Transportation — Three different modes of transport were necessary
because of the nature and variety of sludges in the pilot project and
the physical restrictions of the outloading facilities at the various
plants producing these sludges.
The digested sludge filter cake was hauled from Blue Plains in tandem
wheeled dump trucks at a rate of approximately 12.5 cubic meters
(16.5 cubic yards) per load. The total quantity transported in this
manner was about 3200 cubic meters (4200 cubic yards).
The initial plan called for the trucks to drive directly onto the plots
and discharge their contents onto the ground adjacent to the trench.
Front-end loaders then gathered up the material and placed it in the
trench. This approach immediately proved unsatisfactory because the
trucks, forced to drive through the sludge on the ground, picked up
sludge on their tires. In order to minimize the amount of sludge
carried onto the highway, the trucks were routed along 915 meters
(3000 feet) of earth road before returning to the main thoroughfare.
The front-end loaders also had to maneuver through the sludge on the
ground, and due to the slippery nature of the material, the operation of
equipment was difficult and frequently was interrupted. The portion of
the plot serving as access to the trenches finally became covered with a
layer of sludge making movement nearly impossible. Indeed, the top
layer of sludge-impregnated soil had to be removed in order to allow
efficient operation of the equipment.
As a result of these difficulties, it was decided to excavate a series
of shallow rectangular storage bowls, so that sludge could be discharged
into the bowls at the sides and the loaders could enter the bowl at the
ends to transport the sludge to the trenches. This method was suc-
cessful and was used throughout the remainder of the pilot operation,
both for handling the digested sludge filter cake from Blue Plains and
the raw sludge filter cake from Fairfax County.
The various raw-limed sludge filter cakes were transported to Beltsville
from three water pollution control plants in Fairfax County, Virginia:
the Little Hunting Creek Plant, the Dogue Creek Plant and the Lower
Potomac Plant. The planned system for transport of raw-limed filter
cake involved placing an 18-meter (20-yard) Dempster Dinosaur container
at each of the three plants to collect the sludge and setting up a pick-
up schedule in which full containers were delivered from each plant to
the field site and replaced with empty containers from the site. The
31
-------
Little Hunting Creek Plant and the Dogue Creek Plant, however, produced
relatively small amounts of sludge. In addition, handling of the con-
tainers from the Dogue Creek Plant was difficult since the sludge was
low in solids (15%) and overflowed the sides of the container when it
was loaded onto the truck for hauling. Transport of sludge from three
plants also created an intricate hauling schedule which the contractor,
because of other commitments, was unable to meet. For these reasons,
sludge was ultimately taken only from the Lower Potomac Plant. With
transport from only one plant the container was left on the truck and
the entire vehicle was positioned under a discharge chute for filling.
Sludge from this chute tended to form mounds in the container. Despite
frequent shifting of the container during filling, it was necessary to
manually rake the sludge in the container for optimum use of its capa-
city. Upon arrival at the field site, sludge was discharged into shallow
sludge bowls near the two plots designated to receive raw-limed filter
cake.
The low rate of sludge production at. the Fairfax County plants as com-
pared with the time required for placing the sludge into the trenches,
the lack of supervision during the filling of the containers (the units
were not filled as much as they could have been), and the transport of
sludge only in the evenings and on weekends produced a very inefficient
operation. Arrival of the sludge at the site during periods of non-
operation increased storage times and contributed to an odor problem at
the site.
Raw-limed liquid sludge was transported in 23 cubic meter (6,000 gallon)
tank trucks which contained tank pressurization for pneumatic discharge.
In the initial plan, the trucks were to drive to the edge of the receiv-
ing plot and with assistance of the pneumatic system, if required,
discharge the sludge by gravity directly into the ends of the trenches.
During operation at the first liquid sludge plot, the wet conditions at
the site prevented driving the trucks directly to the plot. Hence, the
trucks were positioned on the access road and approximately 90 meters
(300 feet) of 15-cm (6-inch) aluminum irrigation pipe was used to trans-
port the sludge pneumatically into the trenches. The length of the
pipe, its large size, and an uphill pumping direction prevented effi-
cient operation. There was excessive bypass of air through the pipe, and
sludge was transported in slugs. The lengths of pipe sections also did
not correspond to the trench spacing and frequent disassemblies and
relocations of the pipe were necessary.
The second plot receiving the raw-limed liquid sludge was directly
adjacent to the main access road. It was possible to position the truck
at the end of the trenches and satisfactorily discharge the sludge by
gravity into the trenches.
With the pilot experience, the method of transporting sludge recommended
for the interim project at Cheltenham, Maryland, is the containerization
concept. Sludge should be sealed in steel, water-tight containers, and
transported to the tilling site on tractor-trailer flatbed trucks.
32
-------
Operation — (a) General — The sludge placement operation at the pilot
project was devised to test equipment and procedures on a controlled
small scale basis for their applicability to large scale projects. A
Final Site Plan, including a brief description of the test operations
(treatments), is shown in Figures 1 and 9.
(b) Treatment I — The plot for developing full-scale entrenchment pro-
cedures consisted of one 0.6 hectare (1.5 acre) approximately 150 meters
(500 feet) long and 40 meters (130 feet) wide. The area received
digested sludge filter cake of approximately 22% dry solids. These
sludges were incorporated into trenches 60 cm (2 feet) wide, 60 cm
(2 feet) deep, and 60 cm (2 feet) apart, edge to edge (60 x 60 x 60 cm).
The plot was laid out on a slope having a grade of approximately 10% and
the trenches followed the contours in the area. The soil on half of the
plot was a sandy loam; and that on the other half was similar but
included a small precentage of clay.
The operations were begun by first excavating an initial trench along
the entire uphill edge of the plot. As digested sludge filter cake
arrived from Blue Plains, it was stockpiled in four storage bowls
strategically located around the plot. Two front-end loaders, a wheeled
loader (3.4 cubic meters (4.5 cubic yards) bucket) and a tracked front-
end loader (1.9 cubic meters (2.5 cubic yards) bucket) carried the sludge
from the bowls and placed it into the initial trench. After half of the
initial trench was filled, the trencher began to excavate a second
trench parallel to the first trench, and discharged spoil over the
sludge placed in the first trench. After sludge had been placed along
the entire length of the first trench and the second trench had been
excavated, sludge was placed in the second trench and the third trench
was excavated. This procedure continued until the entire 0.6 hectare
(1.5 acre) plot had been treated.
Since the front-end loaders had to drive into the bowls to remove the
sludge, there was some sludge carried into the field by the equipment.
The sludge on the field later caused slippery conditions, especially
after rain. A portion of the plot became difficult to work after rain
because an underlying impervious clay layer had trapped water near the
surface. The frequent traffic of heavy equipment across this area
produced a spongy surface after heavy rain which made travel through the
area impossible. In addition, the breaking up of the soil all of the
way down to the clay barrier caused caving of trenches excavated in this
area. However, with careful equipment operation, the area was trenched
and the work in Plot I was completed.
Based on an average specific weight of 1000 kg/cubic meter (1700 pounds/
cubic yard), the estimated total volume of sludge placed in Plot I was
1770 cubic meters (2320 cubic yards). The estimated dosage in this plot
was 650 metric tons of dry solids/hectare (290 tons/acre). The design
dosage was 670 metric tons of dry solids/hectare (300 tons/acre). The
deficit was caused by a wider trench spacing than that planned, but was
minimized by some overfilling of the trenches. The loader bucket
33
-------
volumes were such that two placements had to be made with each bucket
load, and difficulty in controlling the amount of sludge discharged
caused the overfilling. Sludge also was tracked onto the plot from the
storage bowl by the equipment.
There was a definite odor problem during the operation because of the
open storage of sludge for a period of time prior to placement in the
trenches and because of a lack of odor control provisions at the site.
However, once the sludge had been placed into the trenches and covered,
the treatment of the entire plot completed, and the storage bowls filled
and covered, the odor diminished appreciably.
Two basic types of equipment were utilized in the entrenchment opera-
tion. A tracked off-set wheel type trencher excavated trenches and
simultaneously back-filled the sludge placed in previously excavated
adjacent trenches. The lateral position of the trenching wheel could be
offset to allow the machine to operate close to another trench and the
wheel could be rotated so that it could be kept in a vertical position
for ground slopes up to 12% maximum grade. The unit was equipped with a
spoil conveyor which could place the spoil up to 3 meters (10 feet)
away. The particular trencher used in this project performed effi-
ciently in dry weather, but with the absence of grouser bars on the
track pads, became unstable in wet weather. The tracks offered no
traction on muddy ground, and when the machine slipped sideways away
from the trench, the trenching wheel became twisted in the trench
and the machine had to be pulled free. Operation of the trencher in
poorly drained areas of the plot was tedious, and the filling of certain
short sections of trench had to be omitted.
It was necessary for the trencher operator to see the previous trench in
order to use it as a guide for excavating a new trench. However, the
trencher was constructed with the operator's seat only on one side.
Hence, the previous trench could only be seen clearly when operating in
one direction. For the short length of the trenches, trenching in one
direction proved an efficient means of operation. Initially, it was
planned to excavate with the trencher wheel perpendicular to grade.
However, observation of actual operation indicated that it was easier
for the trencher to tilt the wheel such that it was always vertical.
Tilting of the wheel to the vertical eliminated excessive strains on the
structure of the machine, but increased the tendency of the downhill
side of the trench to collapse. The operation of the trencher in this
plot was rarely slowed, except in wet weather or when a rock became
jammed in the spoil conveyor and had to be removed by hand. The
trencher operated at speeds up to 7.5 meters (25 feet)/minute in the dry
sandy loam.
The front-end loaders, employed to place sludge into the trenches,
worked well in dry weather. The wheeled loader was fast and maneuver-
able, while the tracked loader was slower and tended to tear up the
surface of the ground when adequate space was not available for man-
euvering. However, during wet weather the wheeled loader frequently
34
-------
lost traction. While the tracked model with good wet weather traction
was able to maneuver out of bad situations, the maneuvering tended to
tear up the surface of the ground, making further operation difficult or
sometimes impossible. Nonetheless the tracked loader was much better
suited for operation in wet weather.
(c) Treatment II - A second plot (Number II) consisted of two 0.1-
hectare (0.25 acre) subplots, each approximately 27 meters (90 feet)
wide and 37 meters (120 feet) long (check plot excluded Figure 9).
Approximately 410 cubic meters (540 cubic yards) of digested sludge
filter cake of 22% dry solids was applied in each subplot for an average
dosage rate of 908 tons dry solids/hectare (405 tons/acre). The sludge
was placed in trenches 60 cm (2 feet) wide, 120 cm (4 feet) deep and
120 cm (4 feet) apart, edge to edge (60 x 120 x 120 cm). When the
contents of one 3.4 cubic meter bucket load were placed in the trench,
the material filled the trench to the top, with about 10 cm overfill.
An increase in trench volume of about 2% due to caving contributed to a
total increase in sludge volume of approximately 10% over the antici-
pated level.
The plot development was basically the same as for Plot I. Each of the
two subplots were worked separately since they were located on opposite
ends of the site. The rate of operation of the trencher was consider-
ably slower than in Plot I because of the increased depth of the trench
and because there was some caving of the sandy trench walls during the
operation. The force exerted on the side walls of the newly excavated
trench by the weight of cover on top of sludge placed in trenches on the
uphill side of the new trench contributed to the wall collapse. When
approximately six trenches had been filled, the combined load of all of
these trenches was transmitted through the plot to the earth barrier on
the uphill side of the trench undergoing excavation. As earth was
removed from the ground to make the trench, the side force on the uphill
sandy barrier resulted in caving of the trench wall. When this occurred
at the immediate point of trenching, it was necessary to stop the for-
ward motion of the machine and remove the excess earth. However, when
caving occurred after the trencher had passed, no remedy was possible.
Caving-in at the machine produced an increase in the dosage while
caving-in after the trencher had passed did not. Caving-in due to the
uphill surface loading could be controlled by periodically skipping a
trench and thereby creating a barrier strong enough to withstand the
load forces. Alternatively, the trencher could be started on the down
slope side of a site, providing the slope is not so steep that the
trencher slips into the previously dug trench.
The test operation located in the sandy loam with clay experienced more
severe wall collapse than in sandy soil alone. After the passage of the
trencher through soil pockets with heavy clay concentration whose bound-
aries were close to the trench walls, the remainder of the clay pocket
in the side wall of the trench fell away into the bottom of the trench.
35
-------
(d) Treatment III - A third plot (Number III) was used to study the
effects of emplacement of raw-limed sludge filter cake averaging about
20% dry solids into the soil. The plot consisted of two 0.05-hectare
(0.12-acre) subplots, each approximately 37 meters x 14 meters (120 feet
x 45 feet), located at opposite ends of the site. Approximately 190
cubic meters (250 cubic yards) of sludge were placed in each subplot,
for an estimated dosage of 735 metric tons dry solids/hectare (320
tons/acre). The operation was identical to that used in Plot I. With
the low sludge production of the Fairfax plants, the filling of these
plots proceeded at a rate of one or two trenches at a time. The raw-
limed sludge exhibited handling characteristics similar to the digested
filter cake. It was again somewhat difficult to control the amount of
sludge discharged from the front-end loader buckets and approximately
25% overfilling occurred.
(e) Treatment IV - A fourth (Number IV) plot consisted of two 0.05-
hectare (0.12-acre) subplots with trenches 60 cm (2 feet) wide and
120 cm (4 feet) deep. The planned spacing of the trenches was 180 cm
(6 feet) apart, edge to edge. The trenches were filled approximately
one-half full with raw-limed liquid sludge (8% dry solids) delivered to
the site from the Blue Plains plant in tank trucks. Since only one tank
truck was available during the project, the rate of delivery of sludge
to the site was too slow to allow the trencher to backfill a previously
excavated trench immediately after sludge was discharged into it.
Therefore, it was planned to excavate all the trenches in the plot in
advance to avoid tying up the trencher for a long period of time. As
the trenching of the first of the subplots proceeded, it was quickly
learned that edge to edge spacing had to be increased to between 240
to 300 cm (8 to 10 feet).
The method used to fill the trenches has been described previously. The
intended method for covering the trenches filled with liquid sludge was
to begin at one edge of the plot and to push the spoil into the trench.
During actual operation, a number of methods were tried. The crawler
front-end loader attempted to push the spoil into and over the sludge.
The motion of the soil along the ground surface caused the sides of the
trenches to collapse, and sludge was forced out of the trench onto the
ground. The second method employed the front-end loader to pick up the
spoil and place it on top of the sludge. Along those portions of the
trench which were narrow, this worked fairly well since the earth could
bridge the distance between the trench walls and form a cover over the
sludge. However, along those wider portions of the trench where caving
had occurred during excavation, placement of soil on top of the sludge
merely displaced the sludge, and again it overflowed the sides of the
trench. The method which proved most satisfactory involved using a
small tractor dozer equipped with a three-directional positioning blade.
The dozer had sufficient space between its tracks to straddle the trench
and was light enough so that it did not overburden the trench Walls. In
moving along the trench, the blade pushed soil from the stockpile on
each side of the trench onto the sludge. There was very little dis-
placement of the sludge to the surface since the trench was closed in a
36
-------
zipper-like fashion. The addition of soil from each side of the trench
enhanced the possibility of the soil bridging over the sludge.
(f) Treatment V - The fifth plot (Number V) consisted of a total of
0.1 hectare (0.25 acre) of land subdivided into smaller sections and
located strategically around the site. Sludge was not applied in this
operation, and the trenches excavated were backfilled immediately.
Approximately 0.05 hectare (0.12 acre) was positioned between the two
halves of Plot I, and was worked as a part thereof. About 0.02 hectare
(0.06 acre) was attached to each part of Plot II, and to one of the Plot
III subplots. These plots were employed as controls and while they
received no sludge, they did undergo the variety of tilling operations.
(g) Tilling - In order to compare various methods of tilling sludge into
the soil, each of the subplots was subdivided into three sections, one
for each of three tilling methods. One tilling method consisted of
leaving the windrows that were created during the entrenching operation
undisturbed. The second tilling method consisted of leveling the wind-
rows with a large tractor dozer (270 Hp, 28,000kg (62,000 Ibs)) approxi-
mately 1 week after the sludge had been placed in the trenches.
After 3 weeks the section of the plot was prepared for revegetation by
drawing a disk harrow with 50-cm (20-inch) diameter blades with a
crawler tractor dozer, both perpendicular to the trenches and later
parallel to the trenches. The time between leveling and disking allowed
stabilization of the sludge/soil mixture and development of a firm
foundation for moving equipment over the area in any direction.
The third tilling method consisted of leveling the windrows and then
drawing a pair of ripper shanks mounted on a larger crawler tractor
(385 Hp, 37,000 kg (82,000 Ibs)) perpendicular to the trenches. The
shanks were spaced approximately 3 meters (10 feet) apart and penetrated
into the ground a distance of about 1 meter (3 feet). While ripping
provided some local mixing action and pulled some sludge to the surface,
a thorough mixing of the sludge and the earth was not achieved by making
a single pass with 3 meter spacing through the section of the plot. The
barrier walls between the trenches, which would normally provide a
foundation for equipment support, were sufficiently broken down by the
ripping action to prohibit several passes through the section with all
heavy equipment except the largest crawler tractor. Approximately 3
weeks after the ripping was completed the section was disked. This
period of time again allowed sufficient time for the earth/sludge
mixture to stabilize, and the smaller tractor was able to traverse the
plot parallel to the trenches without difficulty.
Conclusions and Recommendations — The procedure for applying sewage
sludge to the soil demonstrated during the pilot project at Beltsville
was successful. A wheel type offset trencher to backfill one trench
while excavating a new one was efficient. The use of shallow bowls for
temporary storage of sludge between the time of arrival from the treat-
ment plant and the time of placement in the trenches provided a suitable
37
-------
stop-gap means of separating the sludge transport function from the
sludge placement operation during the pilot operation. Front-end
loaders can be employed to transport sludge in the field from the
storage bowls into the trenches.
The overall operation at Beltsville worked best in dry weather. With
the available equipment it was nearly impossible to run a smooth and
efficient operation during periods of heavy rain. The principle equip-
ment responsible for successful operation during dry weather, the
wheeled front-end loader, was also the main cause for failure during wet
weather. This machine had the speed and capacity to swiftly move the
material about the site and place it in the trenches. However, on wet
ground it lost traction and mired itself into the ground. The loader
was able to extricate itself in most situations, but the required
movement rendered the ground surface impassible. A tracked front-end
loader was also used in the project, but this machine, while operable
under wet conditions, did not have the required speed to keep up with
the work.
An additional wet weather problem resulted from poor access to the
temporary storage bowls. Further, the use of bank run gravel in
the construction of secondary access roads was not suitable for support
of heavy vehicles under wet weather conditions. The dump trucks used in
transporting sludge to the site became bogged down once they left the
main access road. Their extrication became a full-time effort, and the
operation was forced to cease until the site had dried considerably.
All of the tracked equipment was stable on the wet ground, except that
the trencher had no grouser bars on its track pads and exhibited some
tendency to slip.
A final source of concern was the odor evident around the storage bowls,
especially those in which digested sludge was placed. The odor problem
intensified when the sludge was left uncovered for extended lengths of
time, especially during the periods of work stoppage after rain.
Based on experience at the pilot project, the methods developed in the
project were adequate for dry weather operation. In wet weather, while
equipment with tracks were operable, the operation was considerably
slower. For large scale all-weather operation such as that planned at
Cheltenham, Maryland, (discussed in a WR&A report entitled "Sludge
Utilization Project" of August 1972) it is recommended that the sludge
entrenching operation approximate a closed system. To achieve a closed
system the front-end loader/storage bowl system should be replaced with
a specially designed vehicle capable of conveying sludge from a hopper
directly into a trench, while moving parallel to the trench. The sludge
should be transported to the site in sealed water-tight steel con-
tainers, and be transferred by crane into the hopper on the special
vehicle. For all weather operation, the trencher should be fitted with
grouser bars on its track pads.
38
-------
All access roads must be constructed with crushed rock so that the
containers can be transported directly to the tilling site under all
weather conditions. The problem of odor should be minimized by main-
taining a pH of 11.5 or above in the sludge. An emergency system for
odor masking should also be available at the site. The use of the crane
for handling containers should provide the necessary separation of field
operation from over-the-road transport operations. In case of emer-
gency, or when special equipment is not available, the same crane can be
used in conjunction with the front-end loader/storage bowl system to
discharge sludge from the containers into the bowls. A better system
for hauling and entrenching sludge using standard equipment is described
in a later section of this report.
ARS Observations on Sludge Incorporation
Plots were laid out during the last week of April and sludge incor-
poration began at the site on May 1. The final plot layout, with
subsequent final tillage operation, is shown in Figure 9. Identifi-
cation of the entrenchment treatments are given in Table 3.
Timing — Equipment was trucked 'to the site on Monday, May 1, 1972, with
WR&A coordinating the field site work of F. E. Gregory and Sons the
principal contractor and transportation. The equipment used for sludge
entrenchment included that shown in Figure 10. On May 2 operations
began with treatment Ila being completed in about 6 hours, and treat-
ments la, Ib, and Ilia, were initiated. On May 3 rain forced a halt to
the operations indicating the unsuitability of the roads and equipment
for all weather operations. Trenching operations were resumed May 5 and
plots la and Ib were completed on May 8 for a total operating time of 27
hours. A wet area in plot Ib slowed operations considerably and work on
other plots also occurred during that period. Plot lib was begun and
completed in 6 hours on May 6, 1972'and plot Ilia was completed. Plot
Illb was begun on May 6 and continued through to May 11 as the raw-limed
sludge cake slowly arrived. With only one tank truck in operation the
liquid sludge was put into plot IVa on May 10 and 11 and into plot IVb
on May 12.
The time schedule for the arrival of trucks carrying sludge was excel-
lent. Staking in the plot area with metal posts and flagged string
helped traffic control and avoided damage to the groundwater wells.
Tillage After Sludge Incorporation — The tillage treatments are shown
in Figure 9. The tilled plots, the plot area, and the pond are shown in
the aerial photograph (Figure 11). It was necessary to level the
ridges with a dozer before disking and ripping and to backfill the
trenches in the liquid plots IVa and IVb with a small John Deere dozer
and multiposition blade. It was very difficult to perform any tillage
operations on plot Ib because of the extremely wet conditions. The
sandy soil in plot Ib was rather closely underlain with clay. These
conditions, along with all the rain and traffic, caused the plots to
become very unstable.
39
-------
fc k- 'L
p«^in • -i * Y_-" •Wr-f
Figure 10. Sludge incorporation.
40
-------
Figure 11. Aerial photo of site (May 19, 1972)
-------
One month after sludge incroporation and disking it was possible to run
a wheeled tractor perpendicularly across the trenches on all plots
except Ib. Ripping was initially attempted with a D-8 dozer and a
trailing ripper shank about 75 cm (2.5 feet) deep. This ripping method
was unsuitable. A D-9 dozer with two 120 cm (4 foot) long hydraulically
operated ripper shanks was satisfactory. The ripping was done at right
angles to the trenches.
Disking was performed with a D-6 dozer pulling a 50-cm (20-inch) farm
disk. The disking satisfactorily smoothed the field but did not bring
sludge to the surface.
Incorporation Equipment and Facilities — (a) General - In spite of
difficulties with rain and inexperience with the new type of tillage
operations, the job was completed with standard equipment.
(b) Roads - If trucks enter the field site, roads must be stabilized
with gravel or crushed stone or rain will make the roads difficult to
use. During the pilot project over 25 mm (1 inch) of rain fell on the
second day of operations and another 25 mm fell before operations were
complete. Road maintenance required many loads of bank run gravel and
crushed stone. Also required was the constant use of a road grader,
the D-8 dozer, and the loaders for smoothing roadways and assisting
mired equipment.
(c) Loaders - Under dry conditions the rubber tired C977 front-end
loader was very satisfactory, being fast and nondestructive of sod. In
the rain this machine lacked traction and was out-performed by a slower
and smaller tracked loader although the latter badly tore up the sod.
Both loaders spilled considerable amounts of sludge on the soil surface
when moving it from the stockpiles to the trench.
(d) Trucks - The 12 cubic meter (16 cubic yard) dump trucks were not
completely satisfactory for hauling sludge. About 10% of the sludge did
not empty from the trucks, and some adhered to the tires and bodies
during filling, hauling, and dumping. The sludge spilled along the
highway, necessitating truck cleaning facilities at disposal fields.
Sludge placement into pits from trucks proved most feasible for con-
fining sludge while filling loaders.
(e) Recommendation for Road and Field Handling of Sludges - Because of
the initial pilot experiences in hauling sludge in dump trucks and
filling trenches with front-end loaders, a new system was proposed by
WR&A in a report written for the Maryland Environmental Service in
August 1972, entitled "Sludge Utilization Project." WR&A recommended
hauling sludge in covered 10 cubic meter (12 cubic yard) containers that
could be hauled on flat body trucks, tractor trailers, or by rail.
These containers were to be emptied into a specially designed field
42
-------
hopper at the site. The 27.5 cubic meter (36 cubic yard) field hopper
would be mounted on high flotation tires or tracks and be pulled with a
tracked vehicle to the trenches where sludge could be augered and
conveyed into the trenches.
Further experience revealed a considerably less expensive alternative.
Sludge could be hauled in 12 cubic meter (16 cubic yard) concrete mixer
type trucks as shown in Figure 12. In good weather these trucks pull
into the field and discharge their sludge directly into the open
trenches via their own extended discharge chutes. Alternatively, in dry
weather or in wet weather, when the soil is incapable of bearing the
load, the trucks can discharge the sludge into the hopper of a peri-
staltic pump which forces sludge through flexible and solid tubing into
the trench. The solid tubing is attached to the front of a tracked
vehicle that drives beside the open trench. The peristaltic pump system
was proposed by Resources Management Associates for filling trenches
with Blue Plains raw-limed sludge at a. 36-hectare (90-acre) site in
Montgomery County, Maryland.
(f) Trencher - The trencher was sufficiently versatile for trenching. It
should have tracks with cleats to prevent slippage. The trencher is
shown in Figure 13 digging a new 120-cm (4-foot) deep trench and simul-
taneously covering the previous trench now filled with sludge. Because
of the wet ground and the spilled sludge the trencher slipped and caused
uneven trenches. Furthermore, a dozer had to scrape off the surface
occasionally to permit trencher operation. Two men worked with the
trencher operator to help keep proper spacing between trenches and to
keep them straight.
Trench Spacing and Sludge Application Rate — (a) Spacing - The planned
spacing between 60 cm (2 foot) and 120 cm (4 foot) deep trenches was 60
and 120 cm, respectively. The actual spacings were generally greater
(Table 4). The wider spacing occurred in the large 60 cm deep trench
test area (la and Ib) because wet soil caused trencher slippage down
hill away from the previous trench. The spacing between 60 cm deep
trenches in plots Ilia and Illb averaged 60 cm as planned because the
soil was nearly level or sloped slightly towards the area already
trenched. The spacings in the 120 cm deep plots Ila and lib were wider
than planned for the reasons cited for plots la and Ib and because the
very sandy soil caved in occasionally when trenches were 120 cm deep.
(b) Application Rates - Rate of application is dependent upon trench
spacing, degree of fill with sludge, and sludge solids content. Digested
sludge from the Blue Plains plant had been stockpiled for 2 or 3 months
and hence its solids content was higher than the expected 20% (Table 4).
As previously stated the spacing for digested sludge was wider than
anticipated. Combining a greater sludge solids content and a wider
spacing than anticipated with overfill of trenches resulted in the rates
of application for digested sludge given in Table 4. Raw sludge appli-
cation rates were as projected. Width between trenches was as predicted
while sludge solids content was less and filling was greater than planned
43
-------
Figure 12. Cement truck for hauling sludge.
44
-------
Figure 13. Trencher
-------
Table 4. SLUDGE ENTRENCHMENT DATA
Treatment
a & b
I
II
III
IV
V a
b
Trench
depth
cm
60
120
60
120
60
120
*
Spacing
between
trenches
cm
90
150
65
260
90
150
#*
Sludge type
Digested
Digested
Raw- Limed
Raw- Limed
None
None ,.,
Solids
27.6
27.6
18.5
9.3
NA
NA
Rate,
dry metric
tons/ha
830
1150
740
130
0
0
* Spacing is edge to edge.
** Digested and liquid raw-limed from Blue Plains and dewatered
raw-limed from Fairfax plants.
+ Assuming 1.0 wet metric ton per cubic meter of wet sludge,
trench 10% overfilled, and trench width of 60 cm.
Liquid Sludge Incorporation — The procedure for incorporating liquid
sludge in the soil was unsatisfactory. The spacing between trenches for
liquid sludge application in plots IVa and IVb was larger than for
sludge cake (Table 4), because all trenches had to be dug before any
liquid sludge was applied (because of hauling problems and the desire
not to backfill immediately). Backfilling was delayed in order to
determine if dewatering would occur and whether more liquid sludge
could be applied. Dewatering occurred only very slowly and little
additional sludge could be added. In addition, the trench sides caved
in because of all the liquid, the sandy soil texture, and machinery
and spoil burden forces.
Based upon the field experience with liquid sludge, the 120 cm deep
trenches should be filled to not more than 1/3 to 1/2 full and then
immediately backfilled as new trenches are dug. Spacing between
trenches depends upon the ability of the soil between the trenches to
withstand the hydraulic pressure of the liquid sludge and the other
forces.
46
-------
Odor — Some odor problems occurred during incorporation of the aged
digested sludge. There should be less problem with odor when incorp-
orating freshly dewatered sludges by the clean system recommended in the
previous section. Liming also retarded odor in the raw sludge. Odors
rapidly subsided when sludges were entrenched. Very strong, objection-
able odors occurred after placement when the raw-limed plots were disked
The odor persisted, however, only for 1 or 2 days.
Sludge Characteristics — Approximately 25 out of the 250 truckloads of
digested sludge were sampled for analyses. The digested sludges ranged
in solids content from 18 to 35% with most samples ranging from 25 to
29%. The pH ranged from 6.3 to 7.3.
Twenty-three of 36 loads of raw-limed sludge from Fairfax, Virginia,
were also sampled. The solids content of three loads sampled from the
Dogue Creek Plant ranged from 12 to 14% solids and the pH varied from
11.6 to 12.0. The solids content of the sludge from the Little Hunting
Creek Plant was 12.4% and the pH 11.4. The other 19 sampled loads were
from the Lower Potomac Plant. Most of the Lower Potomac sludges had
solids content ranging from 17 to 23%. Two loads were 34% solids. The
pH of most Lower Potomac sludges ranged from 9.6 to 12.0. Three loads
apparently did not receive lime treatment. Their pH was 6.2 to 6.6.
Sludges were composited and analyzed as shown in Table 5. These com-
posited samples were sent to EPA in Cincinnati, Ohio for bacteriological
and viral analyses. Liming very strikingly reduced the contents of
coliform bacteria and other measured pathogens. The data shows that
liming above a pH of 11.5 was necessary to markedly reduce levels of
bacteria. Subsequent tests, however, indicated that salmonella and
fecal coliform bacteria were apparently reproducing again as soon as the
pH decreased with the conversion of Ca(OH)2 to CaC03- Fecal coliform
counts were fairly high in the unlimed digested sludge even though it
had been stockpiled for 2 months or longer.
OTHER PROCEDURES
Planting
Early Summer 1972 — After leveling and disking, the entrenchment plots
were planted in early June with strips of two sweet corn varieties, two
soybean varieties, and Kentucky-31 tall fescue (Figure 14.) Six species
of fruit trees and 11 species of shade trees were also planted, mostly
in the plots with ridges.
Fall 1972 — Balbo rye was seeded in late October 1972 in the areas
previously seeded to corn and soybeans. Several test strips of alfalfa
were also planted (Figure 15).
Early Summer 1973 — After the growth and harvest of rye, the areas were
rototilled and fescue was seeded into the bulk of the plots where rye
47
-------
* ** +
Table 5. BACTERIAL AND VIRAL CONTENT OF COMPOSITED ENTRENCHED SLUDGES
Sample Description
Total count
Fecal
coliform
*+ **
Fecal Salmonella shigella Virus
streptococci species
-P-
oo
1 Composited samples of
Fairfax, Va., raw-
limed sludge with low
pH (below 11.5)4*
50,000/g
2 Composited samples of
Fairfax, Va., raw-
limed sludge with
high pH (above 11,5)*** 11,000/g
3 Liquid sludge,
composited-Blue
Plains, pH less
than 11.5
<30/g
<10/g
5,000/g <30/g
<10/g
<30/g
<30/g negative
<30/g 0.2/g
6.7 x 107/100 ml 7,500/100 ml 44,000/100 ml <30/100 ml <30/100 ml 0.7/g
4 Liquid sludge,
composited-Blue
Plains, pH more
than 11.5***
5 Composited samples
of Blue Plains
digested sludge
hauled 5/2-3/72
6 Composited samples
of Blue Plains
digested sludge
hauled 5/5/72
225,000/100 ml <250/100 ml <250/100 ml <30/100 ml <30/100 ml 0.7g
2_56 x 108/g
3.6 x 10b/g
23,000/g
7,500/g
39,000/g >36/g <30/g negative
8,000/g >36/g <30/g 1.0/g
Continued
-------
* ** +
Table 5 (continued). BACTERIAL AND VIRAL CONTENT OF COMPOSITED ENTRENCHED SLUDGES
Sample Description
Total count"*" Fecal Fecal Salmonella Shigella+ Virus'
coliform streptococci species
Composited samples
of Blue Plains
digested sludge
hauled 5/6/72
Composited samples
of Blue Plains
digested sludge
hauled 5/8/72
4.0 x 10 /g
2.5 x 10 /g
14,000/g
62,000/g
27,000/g
>36/g
16,000/g >230/g
<3Q/g negative
<3Q/g negative
*
**
+
Bacterial analyses by B. A. Kcnner, EPANERC, Cincinnati, Ohio
Viral analyses by the Virus Laboratory, EPA, NERC, Cincinnati, Ohio
All counts on a dry weight basis.
++ Total aerobic counts at 37°C for 48 hrs, samples 1, 5, and 7 had relatively low bacterial counts. The
surviving bacteria were apparently spore- formers (Bacillus _sp.). Numerous fungi also survived, mainly
Asper gillus sp. and Penicillium sp. from their microscopic appearance.
*+ Shi gclla sp. - tests run by best available method and none were detected in any sludge samples.
•+* These pH determinations were made on refrigerated samples about 2 weeks after field delivery and some
warming had occurred. This caused some reduction in pH from that determined on selected samples
immediately after delivery. The fact that the pH was probably higher than when bacteria were determined
likely accounts for the relatively low counts of bacteria in this composited raw- limed sludge.
*** Note the beneficial effect of liming to above pH 11.5
-------
DIGESTED 60xt,0cfn
'/V
RIDGES
-fescue \
DISKED
^banf cutters
L Kent ^
Corn f5llver V?1;
L tochiet ^
DISKED
and
RIPPED
CONTROL
(A) Digested, la
Figure 14. Plot plan for crops planted in June 1972.
50
-------
T
RIDGES
DISKED
Soy-
DIGESTED
N
-fescue
ty-a/
cutler
tenf
_
ier ~^
silver
DISKED
and
cutler
-fescue ^
•2.5-777
(B) Digested, Ib
Figure 14 (continued). Plot plan for crops planted in June 1972.
51
-------
DISKED* RIPPED
CONTROL
+
RIDGED
DISKED
DISKED
and
RIPPED
DIGESTED 60x/20cm
•fescue \
ky-31
Soy-
bean
Corn / iochief*
tertf =5
-fescue {
N
•+- O
17-rr,
•35.5-,
RIDGED
4
DISKED
4
DISKED
RIPPED
*
RIDGED
ON
A.
•rescue
Ky-31
,
bean {_ kenti
Corn
fescue
b
•St.~J.7S™
(C) Digested, Ila,lib
Figure 14 (continued). Plot plan for crops planted in June 1972,
52
-------
X&O
cm
RIDGED
DISKED
N
DISKED
sncl
RIPPED
rescue
ky-3i
kent
iochiefj
Soy- fkent
bean
VesClKZ
a
o
-13
375
DISKED
and
RIPP5D
D/5 KED
RIDGED
DISKED
Co/J TR.OL-
-fescue
Corn
Te
/V
O
Id 2.5^n
•*- 30,-JS-r^
(D) Raw-limed, Ilia, Illb.
Figure 14 (continued). Plot plan for crops planted in June 1972
53
-------
T
DISKED
1
LIQUID RAV/ LI/1 ED
X/3-O
cm
r / iochiefi
Corn (s,lver ^
Soy-
•fescue
ty-3l
A/
le-Kil
•{
1*,'
-H-m
D/5/T£0
.1
iochie-C
•fescue
ETb
A/
(E) Liquid raw-limed, IVa, IVb.
Figure 14 (continued). Plot plan for crops planted in June 1972
54
-------
DIGESTED
' err,
RIDGES
A/
-r
escue
f~-fruit trees
-fescue J
-fruit tre^s
DI5K£D L
alfalfaf
DISKED
and.
RIPPED
CONTROL
Ya
-Fescue
alfalfa
o
o / ~7C~
- oi 6 /o m
-33- m
- 38.76''m
-^d.5 m
75m , 0 m
(A) Digested, la.
Figure 15. Plot plan for crops planted in October 1972 with crop
stand ratings (1-poor to 5-very good) made on
March 15, 1973.
55
-------
DIGESTED
1
Rli
0/f
D/<
o
RIP
conifer frees ->
1GES
-fescue \
(4)
shade "frees^
V.C-4 +
f fruit trees _».
rye J „ ./ ,
xo fruit rrmzs^
)/c£D alWa (
rye/
*/° fecoe {
]P£D al-falfa {
^escue{ comfer ^es^
1 L
-<- 75*77?
*-<2/7W
<-52.5w?
<-VO 7"
+ 4L6'm
+ 5Q-rn
•*- 6/. 75"r/7
<- ^7<--vw
Figure 15 (continued).
(B) Digested, Ib.
Plot plan for crops planted in October 1972 with
crop stand ratings (1-poor to 5-very good) made
on March 15, 1973
56
-------
DIGESTED
DISKED
dni
RIPPED (CONTROL)
RIDGED
DISKED
DISKED
KIPPED
Ha
alfalfa {
1 a "i *-
\ 3) r
fescue |
f r U u r T rs.es — *,
. .1-escue -">
a f a -f ^ ?f v
r ^L
-t-escue r
rye {
& 1
3ir^ir. v
(3ITc3lT(3. r
fescue (
->- 7O w
<- /7 ?"
*• /7-<"r»,
<^ / O 7*7
^7^
*
-------
A/4W LIMED
RIDGED
DISKED
DISKED
and
RIPPED
-fescue{
alfalfa t
-/9. 5 ->
~20 ST
-2.5" 5"
-2'?. 75"
-3/. 5"
DISKED
and
RIPPED
4-
DISKED
RIDGED
-*-
DISKED
and.
RIPPED
-^rescue \
(2) L
com
fer}
mes
CONTROL
alfalfa!
(i)
'(0
alfalfa ;
r
r
shade
fescue |
alfalfa {
i conifer, ^
tre*
(D) Raw-limed, Ilia, Illb.
Figure 15 (continued). Plot plan for crops planted in October 1972 with
crop standing ratings (1-poor to 5-very good) made on March 15, 1973.
58
-------
LIQUID RAW LIMED
DISKED
1
alfalfa {
•fescue (
rye I
a
*- O -rr>
-rrj
1 fescuej
DISKED d|fa|fd {
, r (3-0 i
fescue r
.1 Vr^ '.
V b
^ y^
U 'TV?
•*- fi 75 T^
^14.5*77
(E) Liquid raw-limed, IVa, IVb.
Figure 15 (continued). Plot plan for crops planted in October 1972 with
crop stand ratings (1-poor to 5-very good) made
on March 15, 1973.
59
-------
had been growing. Many shade and fruit trees were replanted. Many died
because they had been planted so late the previous season.
Fall 1973 — Areas were newly seeded to fescue and/or alfalfa that
previously had supported poor stands of alfalfa or fescue (Figure 16).
Also, much of the area left in ridges was now flattened and reseeded
Plots IVa and IVb were releveled before reseeding. Finally part of plot
la and lib were fertilized by a surface addition of digested sludge
before reseeding. The digested sludge was spread by bulldozer on the
soil surface at a rate of about 23 dry metric tons/hectare (10 dry
tons/acre-about 1.2 cm (0.5 inch) deep) and rototilled into the top
15 cm (6 inches).
Seedbed Preparation
All plots received conventional tillage for seedbed preparation. Ferti-
lizer and lime were needed for early growth of crops because of the
infertility of the 30- to 37-cm (12- to 15-inch) layer of subsoil cover-
ing the sludge. Lime additions were at the rate of 3.4 metric tons/
hectare (1.5 tons/acre) of ground calcium limestone in 1972 and the same
rate of ground dolomitic limestone in 1973. All plots received applica-
tions of 225 kg P205, 225 kg K20, and 35 kg N/hectare (200, 200, and
30 pounds/acre).
Most seeding was done with a tractor-mounted cyclone seeder. However,
Kentucky-31 fescue was seeded in 1972 on the ridged plots using a
hydroseeder (courtesy NASA, Buildings and Grounds) and on other plots
by hand with a cyclone seeder. Subsequently fescue and alfalfa were
planted with a tractor-mounted seed drill.
Plant, Sludge, and Soil Monitoring
Gas Analysis — Gas samplers (Figure 17) were installed at a number of
locations in and around the entrenched sludges. The gas sampling system
was developed by John Taylor, ARS. It consisted of a 10 cc disposable
syringe with an on-off teflon valve and a 19-gauge needle. The gas was
pulled into the syringe through a fine pore plastic tubing from a gas
chamber placed in the soil or the sludge. The chamber was a 1.0 cm in
diameter x 2.5 cm long piece of plexiglas tubing with a fine plastic
screen (polyfilter GB) cover glued over the open end. Samples were
taken periodically and analyzed with a gas chromatograph for 02, C02 ,
CH4, and N2.
Plant Elemental Analysis — Samples of the different plant species were
harvested periodically and saved for nutrient and heavy metal analyses.
Plant nutrient contents were determined spectrographically by the Plant
and Soil Analysis Laboratory in Athens, Georgia. Plant heavy metal
contents were determined in our laboratories in Beltsville by Atomic
Absorption Analysis using background correction after dry ashing up to
2 g of representative plant tissue overnight at 480°C, mixing with 20 ml
of IN HC1, and shaking occasionally over a 24-hour period.
60
-------
DIGESTED
H/
60c
RID&ED
+
LEVELED
K//V6
/?73
old rescue^
(2)
r
new -rescue
rw r,
J r,\^
-fescue /
rees -
L truil +r®?S.) T
new fescue<
DISKED
new
alfalfa
DISKED
and.
£
rescue'
(5)
CONTROL
DISKED
old -fescue/
Cs)
O'd -fescue |
neu) al^al-fa'*;
co /l
old fescue
a
\ \
\
-3Jo75
-32. ^
-V05"'
^ fr 7^7
5" 777
(A) Digested, la.
Figure 16. Plot plan for crops planted in early Fall 1973 with crop stand
ratings (1-poor to 5-very good) made on December 4, 1973.
61
-------
DIGESTED
T
RIDGED
f
old -fescue^
(3)
LEVELED
SPRING
I1? 73
'/>
shade -frees
(XV)
(XVI.
fescue
(5)
DISKED
and
(iv)
TruiT Trees
(v)
r
new
lots Cff grdSS
new rescue
old -fescue
(5)
Ib
o
^ISL™
- /'5.25,
Figure 16 (continued).
(B) Digested, Ib.
Plot plan for crops planted in early Fall 1973 with
crop stand ratings (1-poor to 5-very good) made
on December 4, 1973.
62
-------
DISKED
RAPPED
LEVELED
SPRING
DISKED
DISKED
N
la
neuj c3/7a/r
-------
ft AW-LI MED
T
AIDGED
DISKED
DISKED
And.
RIPPED
old -fescue
or <2> <
tjje -fecoe I
xrx L
CS) c
old -fescoc {
^
BEVELED
tueec^s
SPRJNG /?7J
a
W- 1 £T" _«
<- /7 ^T-r
«-
"-33.5 7
DISKED
RIPPED
DISKED
1
LEVELED
SPRING
RID&ED
new -fescue f shade lre (_
rxzw al-falfe ("
very gossy
shade
old -fescue 1
f3t) >
old -fescue
>-*
f
I
I
(
.... b
(D) Raw-limed, Ilia, Illb.
Figure 16 (continued). Plot plan for crops planted in early Fall
1973 with crop stand ratings (1-poor to
5-very good) made on December 4, 1973.
64
-------
LIQUID
-LIMED
T
DISKED
1
old -fescuei
neu -fescue {
en) r
neu alfalfa {
•fescue I
o •>»»
5-m
7.75™
C31
T
RELEVELED
5PRIUG 1173
-L
neu
(2+)
n&u alfalfa (
Uf) \
neu -fescue I
Jit
/3
Figure 16 (continued).
(E) Liquid raw-limed, IVa, IVb.
Plot plan for crops planted in early Fall 1973 with
crop stand ratings (1-poor to 5-very good) made on
December 4, 1973.
65
-------
Figure 17. Gas sampling system.
66
-------
Trenched Sludge and Surrounding Soil — Observation trenches were
periodically excavated at right angles to the trenches (Figure ISA).
Detailed samples were taken from a grid around each trench (Figure 18B).
Wooden tongue depressors were used to sample the soil and the sludge,
and sterile whirlpak plastic bags were used to contain the samples. The
samples were analyzed for total coliform, fecal coliform, and salmonella
bacteria, forms of nitrogen, chloride, and less frequently for soluble
carbon and heavy metals.
Salmonella and coliform analyses were conducted by our laboratories, by
England Laboratories, by Woodard Laboratories, or by the Maryland
Department of Health and Mental Hygiene. Total and fecal coliform
bacteria were determined in test well water by the Most Probable Number
(MPN) methods as described in the 13th edition of Standard Methods
for Examination of Water and Wastewater, APHA, AWWA, and WPCF. For
determination of these organisms and salmonellae in soil, sludge, and
soil-sludge mixtures, approximately 50 g of sample were diluted 1:2 with
sterile distilled water and shaken for 15 minutes at 250 excursions per
minute. A serial 10-fold dilution was made from the suspension.
Fecal and total coliforms were determined in the dilutions by the above
standard procedure. Salmonellae were determined by the MPN technique
using the 10"1 to 10~^ dilutions. Three MPN tetrathionate broth tubes
were inoculated for each dilution. After incubation at 35 to 37°C, a
loop from each tetrathionate broth tube was streaked onto Brilliant
Green Sulfa agar or Bismuth Sulfite agar plates. After incubation for
18 to 24 hours at 35 to 37°C, two to three suspect (pink) colonies were
picked and inoculated onto triple sugar iron agar slants for incubation
at 35 to 37°C for 18 hours. Cultures producing alkaline slants with
acid butts were tested for agglutination with polyvalent 0 and poly-
valent H antisera. Agglutination with both antisera were necessary
as a positive test for salmonella bacteria.
Ammonium and nitrate nitrogen and chlorides were determined on
IN K2S04 and 0.03N^ Al 2(S04)3 extracts of soils and sludges (4 to 1)
using specific nitrogen and chloride electrodes, and total nitrogen was
determined by the Kjeldahl method in our laboratories. Total carbon
was determined by the wet oxidation method and an index of soluble
carbon was determined by running COD with the dichromate method on
water extracts of the soils. Heavy metals were run on ashed samples
of the sludge and on 1-20 extracts of sludges and 1-2 extracts of
soils with 0.005M DTPA, 0.01M CaCl2, and 0.10M TEA at pH 7.3 after
Lindsey and Nowell.
Miscellaneous
Irrigation System — A system for irrigating was assembled in 1972 which
gave partial plot coverage. It was extended in 1973 for irrigating the
entire plot area. The extended system consisted mainly of a Berkely
pump Model B2EQL-30 with Wisconsin VH4D motor, 213 meters (700 feet) of
67
-------
Figure 18. Excavation and sampling of entrenched sludge
and surrounding soil.
68
-------
Akron, 213 meters of ABC, and 427 meters of Wade-Rain 7.5-cm (3-inch)
pipe with necessary fittings including valved-T fittings so that plots
could be irrigated in sections. Rainbird sprinkler heads on 45-cm
(18-inch) risers were spaced as needed. The system also included
183 meters (600 feet) of 10-cm (4-inch) Wade-Rain mainline feeder pipe.
The irrigation water was pumped from the drainage pond.
Fencing — The entire frontage of over 24 hectares (60 acres) along SCS
Road was fenced with a 1.5 meter (5-foot) high galvanized farm fence.
Thus access was limited to the. plot and pond area.
Weather Station — A weather station was installed for securing records
on temperature, precipitation, and relative humidity in the plot area in
July 1972. Precipitation at Beltsville is given in Table 6.
RESULTS AND DISCUSSION
Surface and Underground Water Analyses
Coliform and Viruses — The results of surface and drainage water
analyses for coliforms and viruses are presented in Tables 7 and 8. The
data indicate that the coliform bacteria in the drainage pond for the
most part are a result of surface runoff, because the drainage water in
the subsurface tile in general showed little contamination relative to
that in the surface tile. Note the increased contamination of the
drainage water during late fall and winter. Movement into and/or
persistence in drainage water was apparently greater during this cold
period. From April to August 1973 there was little detectable total or
fecal coliforms in the tile drains or pond. In comparison, the coliform
levels in the stream were high. This stream contamination was appar-
ently from some source other than the sludge plots.
Results of groundwater coliform and viral analyses are presented in
Tables 9 and 10. Viral analyses of well water before and immediately
after sludge entrenchment were negative. Since viral analyses are very
difficult to perform and since the virus levels were so low in the
sludge at time of entrenchment, further viral analyses of underground
well water were not performed. Instead a series of laboratory studies
were run to establish whether virus might move from entrenched sludges
into and through the very sandy soil from the field entrenchment site
(Section VII).
The wells were first sampled on April 24 to 28 before the entrenchment
of sludge. Of the 27 sampled, 10 exhibited positive results for
coliforms, but only one of these exhibited positive results for fecal
coliforms. When the wells were resampled in early May, immediately
after application of the sludge, only five remained positive for
coliforms and none were positive for fecal coliforms. In subsequent
tests there were still a few wells positive for total coliforms during
late May and June 1972 and even a well with a low level of fecal coli-
forms. The presence of contamination in these wells prior to the
69
-------
Table 6. PRECIPITATION AT BELTSVILLE
Date
South
farm
Location of weather station
East
farm
Trench
plots
1972
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
Millimeters of rain
139 137
124 138
269 262
106 49
56 47
39 47
128 104
149 167
148 144
37
36
99
179
126
1973
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
66
74
81
152
95
115
66
81
89
76
45
116
69
77
77
170
95
116
74
47
110
87
18
140
69
68
66
84
99
91
104
17
59
48
20
-
application of sludge, the general absence of fecal coliforms, and the
disappearance of contamination in these wells with time shows that this
initial contamination occurred during installation of the wells and was
not a result of bacterial movement from the sludge.
In November 1972 (6 months after sludge application), water from well 22
exhibited MPN of nearly 1,000 total and 7 fecal coliforms per 100 ml.
This contamination persisted through May 1973 with fecal coliforms
occurring again only in April 1973. Well 22 was 2.4 meters (8 feet) in
depth and located less than 3 meters (10 feet) from the raw-limed sludge
plot Illb. In March 1973, well 23, in the same general area as well 22
exhibited total coliform contamination in the water of 9 increasing to
1,000 MPN/100 ml in April and remaining at comparable levels through
70
-------
Table 7. SUMMARY OF TOTAL COLIFORM ANALYSES OF SURFACE AND UNDERGROUND
DRAINAGE WATERS
Date
Before sludge
Apr 72
After sludge
May-Jun 72
Jul-Oct 72
Nov 72-Mar
Apr-Oct 73
Total
Surface and subsurface
tile**
(left)
63-260
8->16,000
<2
73 7-92,000
o , , *+
<3-43
coliforms, MPN/100 ml "
Surface
tile** Pond+
(right)
<2-20
<2-70 13-16,000
<2-2 13-130
<3-130 31-4,300
<3-4 <3-93
Stream"1"1"
49
79->16,000
1,100-4,600
43-2,300
93->ll,000
* Coliform analyses by ARS and by the Maryland Department of Health and
Mental Hygiene. Counts are based upon numbers of positive tubes in
the most probable number method.
** Tile drain location shown in Figure 1.
+ The pond location is shown in Figures 1, 9, and 11.
-H- The stream drains land to the east and does not drain sludge plot area
directly, rather it drains the pond which does drain the sludge plot
area.
*+ The tile line was dry from Aug to Oct of 1973.
71
-------
Table 8. SUMMARY OF FECAL COLIFORMS AND VIRAL ANALYSES OF SURFACE
AND UNDERGROUND DRAINAGE WATERS
Fecal coliforms, MPN/100 ml*
Date Surface and subsurface Surface
tile+ tile+ Pond"1"1"
(left) (right)
*+ **
Stream Virus
Before sludge
Apr 72
After sludge
<2
<2
<2
negative
May-Jun 72
Jul-Oct 72
Nov 72-Mar 73
Apr-Oct 73
<2-16,000
<2
+*
<3-3,300
<3
<2
<2
<3-2
<3
2-280
<2-13
<3-9
<3-4
<2- 1,700
33-110
<3
<3-460
negative
-
-
-
* Coliform analyses by ARS or by the Maryland Department of Health and
Mental Hygiene. Counts are based upon numbers of positive tubes in
the most probable number method.
** Viral analyses by Maryland Department of Health and Mental Hygiene.
+ Tile drain location shown in Figure 1.
++ The pond location is shown in Figures 1, 9, and 11.
*+ The stream drains land to the east and does not drain the sludge plot
area directly, rather it drains the pond which does drain the sludge
plot area.
+* 3,300 counts on Nov 1972 sampling only, rest of samplings <3 counts.
72
-------
Table 9. SUMMARY OF TOTAL COLIFORM ANALYSES OF UNDERGROUND WELL WATER
* ** +
Wells-total coliformS, MPN/100 ml
Date
1-63 22 "••+ 23 16
(except 16, 22, 23)
Before sludge
Apr 72 <2->l,609 <2 <2 <2
After sludge
May-Jun 72 <2-l,700
Jul-Oct 72 <2-70
Nov 72-Mar 73 <3- 1,100
Apr-Oct 73 <3->l,100
Apr 73
May 73
Jun 73
Jul 73
Aug-Oct 73
<2-2
<2
73-1,100
2,400
1,100
<3
240
-
<2
<2
<3-10
1,100
1,100
<3
<3
<3
<2
<2
<3
10
<3
<3
<3
<3
* Well locations given in Figure 1; well 22, three meters away from raw-
limed plot; well 23, eleven meters away from raw-limed plot; and well 16
is within a digested sludge plot.
** Coliform analyses by ARS or by the Maryland Department of Health and
Mental Hygiene.
+ Counts are based upon number of positive tubes in the most probable
number method.
-H- Well 22 was removed after July 1973.
73
-------
Table 10. SUMMARY OF FECAL COLIFORM AND VIRAL ANALYSES OF UNDERGROUND
WELL WATER
Date
Before sludge
Apr 72
After sludge
May-Jun 72
Jul-Oct 72
Nov 72-Mar 73
Apr-Oct 73
Wells* fecal
1-63
(except 16, 22, 23)
<2-2
<2-5
<2-5
<3-7
<3
coliforms**MPN/100 ml"1"
22
<2
<2
<2
<3-7*+
<3-75+*
23
<2
<2
<2
<3
<3
16
<2
<2
<2
<3
<3
Virus"1"4
1-55
negative
negative
-
-
-
* Well locations given in Figure 1; well 22, three meters away from raw-limed
plot; well 23, eleven meters away from raw-limed plot; and well 16 is within
a digested sludge plot.
** Coliform analyses by ARS or by the Maryland Department of Health and Mental
Hygiene.
+ Counts are based upon number of positive tubes in the most probable number
method.
++ Viral analyses by Maryland Department of Health and Mental Hygiene.
*+ 7 fecal coliforms/100 ml were detected in Mar 73 only.
+* 75 fecal coliforms/100 ml were detected in Apr 73, subsequently <3/100 ml
through Jul 73, then well 22 was removed.
74
-------
May. No fecal coliforms were found in this well. Both these wells were
found to be free of bacterial contamination in June 1973, but in July
the total coliform MPN again increased to 240/100 ml.
Wells 22 and 23 failed air pressure tests in June 1974, which indicated
probable grouting leaks. Well 22 was pulled out and examined. There
were only 25 cm (10 inches) of grout rather than the planned 150 cm
(5 feet). Also, the grouting mixture was apparently originally too wet;
hence, strain occurred and a crack developed in the grout (Figure 6)
through which contaminated surface water entered. In contrast, well 16,
which is located directly within a digested sludge trenched area, did
not fail the air pressure test and as yet its water has not shown
coliform contamination. Data presented later in this report more
strongly suggests that bacterial contamination of the underground well
water did not occur by movement through the soil from the trenched
sludge.
Ammonium- and Nitrate-Nitrogen — In contrast with the results on bac-
terial movement, nitrogen apparently has moved in small quantities from
the entrenched sludge through the soil into the subsurface drainage
system. The nitrogen, however, was probably not moving significantly
into underground well water. When fecal coliform and nitrate-nitrogen
concentrations are compared in water from a subsurface drain line and in
well 16 (Table 11), nitrate moved into the subsurface drainage water but
fecal coliforms did not. Neither nitrate nor fecal coliforms moved into
the wells.
As shown in Table 12, the greatest concentration of ammonium- and nitrate-
nitrogen appeared in the pond (15 and 20 ppm respectively) and the
stream (6 and 19 ppm respectively) within a few weeks after completing
the trenching operations. The high concentrations probably reflected a
general contamination of the soil surface with sludge and subsequent
surface runoff into the pond. The relatively high concentrations in the
subsurface tile may have been due to contamination from surface runoff
entering cracks in the settling soil over the newly installed tile.
From July 1972 through August 1973 mineral nitrogen in the pond appeared
to be a result of nitrogen contamination from both surface and sub-
surface drainage from the plots. In any case the concentrations of
nitrogen in the pond and the stream have been at acceptable levels
(Table 12) since June 1972. The nitrogen concentrations in the stream
varied from a minimum of less than 1 ppm to a maximum of 6 ppm, while
those in the pond varied from less than 1 ppm to a maximum of 4 ppm.
A summary of results of well water analyses for ammonium- and nitrate-
nitrogen is given in Table 13. Of the 41 wells sampled from May 1972
through May 1973 only 19 showed ammonium- and nitrate-nitrogen con-
centrations above 1 ppm. Nine of these wells were adjacent to and 10
were distant from the trench area. The highest concentrations occurred
in well 22 with from 6 to 21 ppm of nitrate-N occurring at various
times. Well 22 was adjacent to a trench containing lime treated raw
75
-------
Table 11. COMPARISON OF FECAL COLIFORMS AND NITRATE-NITROGEN IN
SUBSURFACE DRAIN TILE (RIGHT) AND PLOT WELL 16
Fecal coliforms Nitrate - N
Date MPN/100 ml mg/1
Tile Well Tile Well
Before sludge
Apr 72
After sludge
May-Jun 72
Jul-Oct 72
Nov 7 2- Mar 73
Apr-Oct 73
<2
<2
<2
<3-2
<3
<2 <1 <1
<2 <1- 14
-------
Table 12. SUMMARY OF NITROGEN ANALYSES OF SURFACE AND UNDERGROUND DRAINAGE WATERS
Nitrogen, rag/1
Surface and
Subsurface tile Subsurface tile Pond
(left) (right)
NH4-N N03-N NH4-N N03-N NH4~N N03~N
Before sludge
Apr 72 1 1 <1 <1 <1 <4
After sludge
May-Jun 72 <1-1 <1-16
-------
Table 13. SUMMARY OF NITROGEN ANALYSES OF UNDERGROUND WELL WATERS
Date
1-63
NH -N NO -N Date
4 3
(except 16, 22, 23)
Nitrogen in wells,
22**
NH -N NO -N
4 3
mg/1
23
NH -N NO -N
4 3
16
NH -N NO -N
4 3
Before sludge
Apr 72 <1
-------
Table 14. CHLORIDE ANALYSES OF UNDERGROUND WELL WATER
Wells*- chloride, mg/1
Date
1-63** 16 21 22 23 42 62
Before sludge
Apr 72
After sludge
May-Jun 72
Jul-Oct 72
Nov 72-Mar 73
Apr-Oct 73
Nov- Dec 73
Jan 74
0.5-24 1 1
0.5-18 2 2
0.7-18
-
<1-18 28-72 73-36
l-52+ 89-64
1-12 49 21
2 2
2 2
2
47-95 4-8
64-39++ 4-10
6
6
24
42 21
38
27
35-41 24
64
33 20
* Well locations are given in Figure 1; well 16 is within a digested sludge
plot; wells 21, 22, 23 are 3 to 12 m (10 to 40 ft) from sludge plots;
well 42 is 550 m to the north of the entrenchment plots; and well 62 is
150 to 180 m to the southeast.
** Excluding wells 16, 21, 22, 23, 42, 62.
+ Well 40 contained 52 ppm in Dec 72 which decreased to 8 ppm in Jan 72.
4+ Well 22 was removed after Jul 72.
The increase in chloride in well 22 appeared to be both from surface as
well as subsurface contamination (see discussion on well 22 in previous
section on nitrogen). On the other hand increases in chloride in well
21, located about 12 meters (40 feet) from plot lib, apparently were
real. The chloride concentration decreased after peaking in May 1973.
Continued elevated levels of chloride in wells 42 and 62, located seve-
ral hundred yards each from the plot, were indicative of contamination
from some other source. Well 23 was not contaminated with either chloride
or nitrate.
Measured conductivities of well water were much more erratic than meas-
ured chloride concentrations (Table 15). Water from wells 3, 11, 34,
79
-------
Table 15. CONDUCTANCE OF UNDERGROUND WELL WATER
00
o
Date
Before sludge
Apr 72
After sludge
May-Jun 72
Jul-Oct 72
Nov 72-Mar 73
Apr-Oct 73
Nov-Dec 73
Jan 74
2
Wells*- conductivity )jpihos/cm
1-63**
22-200
23-160
28-160
28-313
17-335
20-220
20-280
* Well locations are given in
23 are 3 to 12 m from sludge
and well 62 is 150 to 180 m
** Excluding wells 16, 21, 22,
16 21 22
55 50
60 70 60
_
44-58 173-202 308-353
70-130 201-161 254-151+
180
200 110
Figure 1; well 16 is within a digested
plots; well 42 is 350 m to the north
to the southwest .
23, 42, 62.
23 42
45
60 320
45 320
44-57
71-50 82-315
-
60 300
sludge plot; wells
of the entrenchment
62
120
-
125
110
120
120
21, 22,
plots;
+ Well 22 was removed after Jul 72.
-------
and 40 had elevated conductivities at one time or another, revealing a
wide range in conductivities for the monitoring wells. The wide range
in conductivity measurements in these wells probably had nothing to do
with contamination from sludge. In other wells where chloride con-
centrations in the water increased as well as conductivity, such as well
16, the increase may have been related to contamination from sludge.
The increase in conductivity in well 16, however, did not parallel the
behavior of chloride. From the available data, therefore, it is not
possible to relate conductivity of well water to contamination from
sludge.
Chloride concentrations increased somewhat in drainage and pond water
after entrenchment of sludge (Table 16), probably caused by movement of
chloride from the sludge. Conductivities may also have increased after
sludge entrenchment (Table 17), but the measurements exhibited con-
siderable variability.
Other Chemical Analyses — A series of chemical analyses were performed
on water from selected wells, the drain lines, the pond, and the stream.
Little change occurred in any of the major or minor chemical elements or
constituents (Tables 16, 17, 18, and 19). The native concentrations of
heavy metals (Table 18) in fact were quite low and have not increased.
Concentrations of all measured biological and chemical properties of
underground well water and drainage water have nearly always been less
than would be permitted in public water supplies (Table 20). In
addition, during the study, all underground well water met drinking
water standards.
Entrenched Sludge and Surrounding Soil
Introduction — Periodic chemical and biological measurements of water
under and draining the trenched experimental plots showed that some
sludge components moved through the soil. While indicator fecal coli-
form organisms and heavy metals remained at low concentrations in plot
wells and drainage waters 19 months after sludge entrenchment, total
coliform microorganisms, nitrate, ammonium, and chlorides increased
somewhat. While the observations strongly suggest that the total
coliform microorganisms moved from the sludge down into the soil, these
microorganisms could have come from many sources other than sludge and
they can survive and reproduce in the soil. There is abundant evidence
in the literature that nitrogen, ammonium, and chlorides move through
the soil, but these materials also may come from places other than
sludge, e.g. from fertilizer such as that used around the plot area.
Thus a more direct study of the entrenched sludge and a determination of
possible movement of components through the soil from the entrenched
sludge was needed. Cross sections of entrenched sludge and soil were
therefore exposed periodically for observation and sampled for analysis
(Figure 18). Later data on trench cross section analysis than discussed
in the main body of the text may be found in the Appendix.
81
-------
Table 16. ANALYSES OF SURFACE AND UNDERGROUND WELL WATER FOR SO^, P04, Cl, NH4, AND N03
oo
N5
Source
Underground
well **
water
Surface and
subsurface
(left) tile
drain
Subsurface
(right)
tile drain
Pond
Stream
Date
Apr 72 (Before)4"
May 72 (After)4^
Jun 72
Jan 73
Oct 73
Apr 72 (Before)
May 72 (After)
Jun 72
Jan 73
Apr 72 (Before)
May 72 (After)
Jun 72
Jan 73
Jul 73
Oct 73
Jan 73 (After)
Oct 73
Apr 72 (Before)
May 72 (After)
Jun 72
Oct 73
S°4
4-60
4-66
6-38
-
2-16
4
12
13
-
8
16
16
.
29
24
—
29
4
18
23
8
P°4
<0. 05-1. 95
<0. 01-0. 15
0.02-0.06
0.01-0.08
<0. 01-0. 01
<0.05
0.01
Of02
<0.01
<0.05
<0.01
0.02
<0.01
0.15
<0.01
<0.01
0.01
<0.05
0.03
0.03
0.01
Cl
---- mg/ l
0.2-7.4
1.0-7.1
0.5-6.4
2.5-8.0
5 . 0-44 . 0
1.0
3.7
1.7
12.6
9.6
11.9
11.3
40.0
30.0
22.0
15.0
33.0
1.5
17.3
13.4
32.0
NH4
0
0
0
0-7
1
1
<1
<1
-------
Table 17. ANALYSES'OF SURFACE AND UNDERGROUND WELL WATER FOR: K, Na, Ca, Mg, CONDUCTANCE AND pH
00
OJ
Source
Underground
1 1**
well
water
Surface and
subsurface
(left)
tile drain
Subsurface
(right)
tile
Pond
Stream
* Analyses
** Range of
+ Before si
Date
Apr 72
May 72
Jun 72
Jan 73
Oct 73
Apr 72
May 72
Jun 72
Jan 73
Apr 72
May 72
Jun 72
Jan 73
Jul 73
Oct 73
Jan 73
Oct 73
Apr 72
May 72
Jun 72
Oct 73
(Before)*
(After)"1"1"
(Before)
(After)
(Before)
(After)
(After)
(Before)
(After)
by Maryland Department
values for wells 4, 10
udge plac
ement.
K
1.0-71.0
0.6-2.5
1.0-50.0
1.2-39.8
1.3-5.1
1.0
1.1
1.8
1.5
1.5
1.1
2.3
2.7
4.2
2.5
2.3
3.4
0.8
1.0
2.3
1.6
of Water
, 11, 21,
0.
0.
0.
0.
1.
0.
1.
1.
1.
5.
5.
4.
4.
4.
1.
2.
3.
7.
9.
5.
7.
Na
8-9.8
5-7.0
8-11.0
4-15.7
0-3.6
8
0
0
3
5
0
1
7
7
3
6
8
5
4
0
5
Ca
1.9-3.
1.8-4.
1.3-3.
1.1-2.
1.0-4.
2.8
4.2
3.4
5.7
4.4
7.1
5.3
20.0
1.9
14.7
9.9
17.0
2.7
3.5
5.4
10.6
/ i
mg/ 1 --
6 0.
2 1.
8 1.
6 0.
3 1.
1.
2.
1.
3.
1.
1.
1.
4.
17.
18.
2.
16.
1.
2.
1.
7.
Mg
8-2.6
2-2.7
3-3.8
8-2.8
2-4.2
4
0
7
1
5
9
7
5
2
7
2
5
6
0
4
2
Specific
conductance
pmhos/cm
4-311
49- 194
3-160
-
40- 166
53
70
47
-
88
97
76
.
220
215
_
185
116
124
77
114
PH
4.6-6.
it. 2-7.
4.6-6.
-
4.4-7.
5.6
6.3
5.4
-
5.6
5.4
5.2
.
6.6
6.7
_
4.9
4.4
4.6
4.9
6.3
7
4
5
0
Resources.
23, 26,
61.
++ After sludge placement.
-------
Table 18. ANALYSES OF SURFACE AND UNDERGROUND WELL WATER FOR: Fe, Mn, Zn, Cd, Cr, Ni, Pb, Hg, AND Cu
00
Source
Underground
well**
water
Surface and
subsurface
(left)
tile drain
Surface
(right)
tile drain
Pond
Stream
Date
Apr 72
May 72
Jun 72
Jan 73
Oct 73
Apr 72
May 72
Jun 72
Jan 73
Apr 72
May 72
Jun 72
Jan 73
Jul 73
Oct 73
Jan 73
Oct 73
Apr 72
May 72
Jun 72
Oct 73
(Before)"1"
(After)""-
(Before)
(After)
(Before)
(After)
(After)
(Before)
(After)
Fe
Mn
Zn
Cd
Cr Ni
Pb
Hg
Cu
<0. 05-28. 5
<0.01
<0.05-7.6
. 1
<0.1
<0.05
<0.25
<0.25
<0.1
<0.0001-
0.0004
<0.0001
-
<0.0001
<0.0001
<0.0001
<0.0001
-
<0.0001
<0.0001
<0.0001
.
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
.
<0.0001
<0.025
<0.05
<0.05
<0.025
<0.05
<0.025
<0.05
<0.05
<0.025
<0.025
<0.05
<0.05
<0.025
<0.05
<0.05
<0.025
<0.05
<0.025
<0.05
<0.05
<0.05
+ Before sludge placement.
-H- After sludge placement.
-------
Table 19. ANALYSES*OF SURFACE AND UNDERGROUND WELL WATER FOR INORGANIC AND
ORGANIC CARBON AND DISSOLVED SOLIDS
Source
Underground
well**
water
Surface and
subsurface
(left)
tile drain
Surface
(right)
tile drain
Pond
Stream
Apr 72
May 72
Jun 72
Jan 73
Oct 73
Apr 72
May 72
Jun 72
Jan 73
Apr 72
May 72
Jun 72
Jan 73
Jul 73
Oct 73
Jan 73
Oct 73
Apr 72
May 72
Jun 72
Oct 73
Date
(Before)"1"
(After )++
(Before)
(After)
(Before)
(After)
(After)
(Before)
(After)
Inorganic
carbon
<1-14
1-6
1-14
4-21
2-3
2
1
6
3
1
1
6
15
3
11
4
4
<1
1
1
2
Organic
carbon
mg/ j.
2-87
3-159
1-82
1-26
-------
Table 20. SURFACE WATER CRITERIA FOR PUBLIC WATER SUPPLIES'
Constituent or characteristics
Permissible
criteria
Microbiological:
Coliform Organisms
Fecal coliforms
Inorganic chemicals:
Ammonia
Cadmium
Chloride
Chromium, hexavalent
Copper
Lead
Nitrates
Nitrites
pH (range)
Sulfate
20,000/100 ml
2,000/100 ml*
mg/1
0.5 (as N)
0.10
250
0.05
1.0
0.05
10 (as N)
1.0 (as N)
5.0 - 9.0
250
* Data taken from Water Quality Criteria, Report of the National Technical
Advisory Committee to the Secretary of Interior, 1972.
** Microbiological limits are monthly arithmetic averages based upon an
adequate number of samples.
86
-------
Movement and Persistence of Coliforms and Salmonellae — From freshly
exposed cross-sections of entrenched sludge, samples were selected from
the sludge, from depths below the sludge, and at distances from the side
of the sludge. The soil samples from the sides were selected along a
line midway between the top and bottom of the trench. Samples below the
trench were selected along a line midway between the sides of the trench.
The sampling was initiated 3 months after entrenchment and continued for
the remainder of the study. The data are summarized in Tables 21, 22,
23, and 24.
Fecal coliform and salmonella microorganisms were not detected in the
soil at distances greater than 15 cm (6 inches) below or to the side of
the entrenched sludge. If fecal coliform and salmonella microorganisms
moved distances greater than 15 cm from the entrenched sludge, the
organisms either were inviable or undetectable by the procedures used.
Total coliform microorganisms, however, were detected at distances of
60 cm (24 inches) from the trenches. The total coliform bacteria had
apparently moved out from the entrenched sludge into the surrounding
soil. These results suggested that the total coliform microorganisms
detected in the subsurface drainage water could have moved from the
entrenched sludge through the soil when the plots were close to the
drain lines.
The total and fecal coliform bacteria present in the digested sludge of
the 60 x 60 cm trenches decreased in number with time. The salmonella
bacteria, not measured until 14 months after sampling, were always below
the levels of detection (Table 21). In the 60 x 120 cm digested trenches,
the fecal coliforms and salmonella bacteria counts were low throughout
the sampling periods. Total coliform counts were low the 7th month, but
were found to have increased by the 12th and 17th months (Table 22).
Although total and fecal coliforms initially were not detected in the
raw-limed sludge, they were detected 2.5 and 15 cm (1 and 6 inches)
below the trench. Apparently these organisms, unable to grow in the
sludge, were able to grow in the soil close to the sludge. A possible
reason was that an inoculated substrate, moving from the sludge,
decreased in pH as it contacted the soil. The increase in numbers of
total and fecal coliforms in the raw-limed sludge itself that occurred
in the 10th month after entrenchment and persisted into the 17th month
for the total coliforms (Table 23), may have also been a result of a
decrease in pH of the sludge as the Ca(OH)2 was converted to CaCO^
(Table 25). Total and fecal coliforms and salmonellae were still
present in the 60 x 120 cm raw-limed liquid sludge trenches after 19
months (Table 24).
In summary, there was little threat of movement of bacterial pathogens
from the entrenched sludge. Survival in limed sludge probably depended
upon the ability of bacteria to regrow as the alkalinity of the sludge
was reduced with time. Since most pathogens are incapable of growing
outside their hosts except in special media, liming should provide
effective control. For total and fecal coliforms, survival in both
87
-------
Table 21. BACTERIA IN ENTRENCHED (60 x 60 cm) DIGESTED SLUDGE AND IN SURROUNDING SOIL
00
CO
Plot
Date
Months
v-
Determination"
la
8/3/72
3
TC FC
la
9/27/72
4
TC FC
TC
Ib
7/3/74
14
FC
S
Location
Trenched sludge
Below, cm
2 55,62**
15 55,75
30 55,90
45 55,105
60 55,120
100 55,160
Side, cm
5 25,35
15 15,35
25 5,35
>41,000 >41,000
1,600 220
3,900 8.7
<2 <2
-
<2 <2
2.3 <2
_
-
- -
330
100
<0.3
<0.3
<0.3
-
-
<0.3
<0.3
16
<0.5
<0.3
<0.3
<0.3
<0.3
-
-
<0.3
<0.3
<0.3
(55,35)** 3,500
(55,55) 7,080
(35,35) 64,600
8
18
87
<6
-
-
<6
<6
<6
<14
<14
10,300
<6
<6
<6
<6
-
-
<6
<6
<6
<14
<14
<14
<6
<6
<7
<6
-
-
<6
<6
<6
* TC = total coliform, FC = fecal coliform, and S = salmonellae.
** These locations are given in Figure 19.
Continued
-------
Table 21 (continued). BACTERIA IN ENTRENCHED (60 x 60 cm) DIGESTED SLUDGE AND IN SURROUNDING SOIL
Plot
Date
Months
Determination
la
10/17/73
17
TC FC
S
la
11/27/73
18
TC FC
MPM j
njrlNy
'g dry w
S
TC
'
V Control
11/14/73
18
FC S
Location
Trenched
Below
7
15
30
45
60
Side,
5
15
25
sludge
(A)+ <4
(B) 32,000
(C) 68
<4
<6
<8
<4
<6
<8
(A)+ 120
(B)5,800
(C) 720
<5
<7
<8
<5
<7
<8
(X)++46
(Y) <4
(Z) <3
<3
<3
<3
<3
<3
<3
, cm
55,
55,
55,
55,
55,
cm
25,
15,
5,
62
75
90
105
120
35
35
35
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
+ Regions A, B, and C represent different degrees of sludge decomposition in the trenches shown in
Figure 26 and are: (A) peat-like dry, considerable root penetration; (B) peat-like, moist, some
root penetration; and (C) original moist condition, little root penetration.
++ Region X was the top 5 cm of the trenched control, region Y was the next 20 cm of the control
trench, and region Z was the bottom 35 cm of the control trench.
-------
C
m
WIDTH
i I
EXCAVATED SOIL
30 60
COVER
30- - — r-\-
SOIL
60 r
I3J)
ORIG1NAL
SO/L
SO/L
So/i.
150-
Figure 19.
I I
Schematic representation of entrenched sludge and surrounding
soil showing labeling scheme in inches.
90
-------
Table 22. BACTERIA IN ENTRENCHED (60 x 120 cm) DIGESTED SLUDGE AND IN SURROUNDING SOIL
Plot
Date
Months
Determination*
Location
Trenched
Below
2
15
30
60
Side,
5
15
25
sludge
I I a lib
8/16/72 12/27/72
3 7
TC FC TC FC
20,000 230 0.9
<0.9
<9
lib
5/16/73
12
S TC FC S
— MPN/g dry wt
**
(55,62) 112,000
(55,119) 22,800
(35,35) 32,100
9
13
57
14
<10
<7
lib
11/1/73
17
TC FC S
(A) + 560
(B) 27,000
(C) <7
<4
19
<7
<4
<4
<7
, cm
55,
55,
55,
55,
cm
25,
15,
5,
122**
135
155
180
60
60
60
2.2 0.4 3,400
3.8 0.2 <0.3
<0.2 <0.2 <0.3
3.8 <0.2 10
4,800
<0.3
<0.3
<0. 3
<0.3
<0. 3
<0. 3
<0. 3
<0. 3
<0. 3
<4
<4
<3
<3
<4
<3
<3
<4
<4
238
-
75
372
522
<4
<4
37
-
<4
<4
<4
<7
<6
<6
-
<7
<7
<7
3
<3
<3
<3
81
80
<3
<3
<3
<3
<3
<3
10
<3
<3
<3
<3
<3
<3
<3
<3
* TC = total coliform, FC = fecal coliform, S = salmonellae
** These locations are given in Figure 19.
+ Regions A, B, and C represent different degrees of sludge decomposition in the trenches shown in Figure 26
and are: (A) peat-like dry, considerable root penetration; (B) peat-like, moist, some root penetration;
and (C) original moist condition, little root penetration.
-------
Table 23. BACTERIA IN ENTRENCHED (60 x 60) RAW-LIMED SLUDGE
AND IN SURROUNDING SOIL
Plot
Date
Months
Determination*
Location
Trenched sludge
Below, cm
2 55,62**
15 55,75
30 55,90
45 55,105
60 55,120
Side, cm
5 25,35
15 15,35
25 5,35
Ilia Ilia Ilia
8/2/72 8/10/72 9/6/72
33 4
TC FC TC FC TC
<75 negative
-------
Table 23 (continued).
BACTERIA IN ENTRENCHED (60 x 60) RAW-LIMED
SLUDGE AND IN SURROUNDING SOIL
OJ
Plot
Date
Months
Determination
Location
Trenched sludge
Below, cm
2 55,62**
15 55,75
30 55,90
45 55,105
60 55,120
Side, cm
5 25,35
15 15,35
25 5,35
TC
320
1
0.4
<0.3
27
<0.3
27
<0.3
27
Ilia
12/19/72
7
FC
<0.4
<0.3
<0.3
<0.3
<0.3
<0.3
<0.3
<0.3
<0.3
S
<4
<3
<3
<3
<3
<3
<3
<3
<3
TC
29,000
16,000
8,500
12
49
87
-
-
84
<3
<3
Ilia
3/7/73
10
FC S
5,400 <11
4,100 <11
3,400 <11
<3 100
<4 <4
<4 <4
-
-
<3 <3
<3 <3
<3 <3
TC
(A)* <3
(B) 180,000
(C) 590
10
<3
<3
<3
<3
4
<3
<3
Ilia
10/30/73
17
FC
<3
<4
<9
<3
<3
<3
<3
<3
<3
<3
<3
S
<3
<4
<9
<3
<3
<3
<3
<3
<3
<3
<3
** These locations are given in Figure 19.
+ Re-gions A, B, and C represent different degrees of sludge decomposition in the trenches shown in Figure 26
and are: (A) peat-like dry, considerable root penetration; (B) peat-like, moist, some root penetration;
and (C) original moist condition, little root penetration.
-------
Table 24. BACTERIA IN ENTRENCHED (60 x 120 cm) RAW-LIMED
LIQUID SLUDGE AND IN SURROUNDING SOIL
Plot
Date
Months
Determination'
TC
IVa
12/6/73
19
FC
Location
Trenched sludge (A)
(B)
(C)
(D)
Below, cm
880
9
<3
MPN/g dry wt
29
<7
<3
44
1,300
<3
2
15
30
60
55,122**
55,135
55,150
55,180
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
Side, cm
5
15
25
25,60
15,60
5,60
4
<3
<3
4
<3
<3
<3
<3
<3
* TC = total coliform, FC = fecal coliform, S = salmonellae
** These locations are given in Figure 19.
+ Regions A, B, and C represent different degrees of sludge decomposition
in the trenches shown in Figure 26 and are: (A) peat-like dry, consider-
able root penetration; (B) peat-like, moist, some root penetration; and
(C) original moist condition, little root penetration. Region D is the
area immediately below the sludge where top soil and/or subsoil plus
leachate from liquid sludge apparently penetrated (2 to 15 cm) into the
soil.
94
-------
Ul
Table 25. THE pH OF RAW-LIMED SLUDGE INITIALLY AND WITH TIME AFTER ENTRENCHMENT IN PLOT Ilia
Date
Months after
6/72
0
8/2/72
3
12/19/72
7
3/7/73
10
10/30/73
17
12/7/73
19(IVa)
entrenchment
Mean
9.6
7.9
8.9
* Locations given in Figure 19.
** Zones given in Figure 20B
+ Zones given in Figure 20E
6.7
7.4
By location
55,35* 11.3 55,35 7.9 35,15
55,55 7.9 35,35
35,55
55,35
55,55
7.6
8.5
7.5
11.2
7.8
« w
A
B
C
4.1
6.4
7.4
_
B+ 7.3
C 7.4
-------
Table 26. NITRATE-NITROGEN MOVEMENT INTO SOIL FROM ENTRENCHED SLUDGE
Nitrate -N, yg/g dry weight in sludge
Raw
Location 60 x 60 cm
3 17
Trenched sludge (B)* 280 1900
(C)**100 110
Below, cm
2 93 243
15 28 45
30 17
45 17
60 - 6
Raw liquid
60 x 120 cm
Months after
19 3
58 15
60
60 146
51 20
56 3
67 3
22
Digested
60 x 60 cm
entrenchment
17 19
1200 1000
40 60
25 54
21 47
12 28
15 27
8 19
Digested
60 x 120 cm
3 17
15 600
5 40
3 3
3 3
2 3
2 5
2
* Mostly aerobic sludge.
** Anaerobic sludge.
-------
c
ID
SLUDGE ZONE CONDITION
130, i
r;
Densely rooted
Mostly subsoil
Top and subsoil
ISO-
DETERMINATION
-/*g/g dry weight
[ ] "V"
• Location
( )_»03:N_
Figure 20.
(A) Control (Va).
Ammonium-and nitrate-nitrogen in and around entrenched
sludge 17 months after entrenchment.
97
-------
/
7
3 9 s
5 7
Cf /
r~/i ~ ~i *~ ~
*/• 6 '
i
i
LUDC
(FJ
^
N^N
c
(Figs. 20, B-F)
Aerobic, peat-like,
no roots
Intermediate
sparse roots
Anaerobic, sludge-like
no roots I
DETERMINATION (Figs. 20, B-F)
yug/g dry weight i
Location
/80]-
— I- - ,_ L _ ( )N03-N _ _
Figure 20 (continued)
(B) Raw-limed (Ilia).
Ammonium-and nitrate-nitrogen in and around
entrenched sludge 17 months after
entrenchment.
98
-------
GlD
7
• I
5"1
30 n,, -
41 ~&~I3
23 /J5 /H.
w & w
• • • 1
MJS-lt-H^
\
*~Ai-
|
//
ior -• -
3\^
J2\
3*
i f%
13
3o
/9
-2? —
/A
?
i/;t
'^
F7~
v>- x
cy ^r
^oy !
9o|
-zv.
_[6V-A^-A/
C/-§M03-A/
57|
/£•
2*?
-ji
Figure 20 (continued).
(C) Digested (la).
Ammonium- and nitrate-nitrogen in and around
entrenched sludge 17 months after
entrenchment.
99
-------
150~~ ~~
\
(D) Digested (la).
Figure 20 (continued). Ammonium-and nitrate-nitrogen in and around
entrenched sludge 19 months after entrenchment.
100
-------
G
|
30 ,-j
-
'3V
/SO
I80\- - £ ! i8 — -
(E) Raw-limed liquid (IVa).
Figure 20 (continued). Ammonium- and nitrate-nitrogen in and around
entrenched sludge 19 months after entrenchment
101
-------
c,
0
13.0
160— -^ ^-
37
>V
0.0 __ \_9
3 3
£8
51
_?L
(F) Digested (Ha) .
Figure 20 (continued). Ammonium-and nitrate-nitrogen in and around
entrenched sludge 17 months after entrenchment
102
-------
Table 27. CHEMICAL OXYGEN, TOTAL NITROGEN, AND TOTAL CARBON IN SOIL
SURROUNDING 60 x 60 cm DIGESTED (NO TOTAL C) AND RAW
SLUDGE TRENCHES 17 MONTHS AFTER SLUDGE ENTRENCHMENT
Sludge
Soil Digested Raw
Location 10/17/73 10/30/73
COD*
Above sludge, cm
15 55,15 396
Below, cm
2 55,62** 442
15 55,75 259
30 55,90 564
60 55,120 381
Side, cm
5 25,35 168
25 5,35 488
Total N COD Total N Total C
it/ A ' "U+-
Ug/g dry weignt
to
262 375 286 2.2
286 688 696 1.7
171 1,143 210
110 312 91 0.04
110 250 8 0.04
179 259 379 0.9
112 344 268 1.2
* COD on 1 to 1 water extraction of soil.
** Exact location key in Figure 19.
entrenched digested and raw-limed sludge might occur for periods in
excess of a year. Salmonella survival fortunately was much less tena-
ceous. Positive identification did occur after 12 months in the digested
60 x 120 cm (2 x 4 foot) trench and after 19 months in the raw-limed
liquid 60 x 120 cm trench.
Movement and Fate of Ammonium- and Nitrate-Nitrogen — Data showing
levels of nitrate- and ammonium-nitrogen in and around the trenches are
presented in Table 26 and Figure 20A-F. Considerable movement of both
nitrate- and ammonium-nitrogen occurred. Both of these forms of nitro-
gen were detected 60 cm (2 feet) below the trenches at concentrations
considerably above the background levels in the control (Figure 20A).
103
-------
The greatest concentrations of nitrate and ammonium were detected under
the 60 x 60 cm digested and 60 x 120 cm raw-limed liquid trenches. As
might be expected, vertical movement was greater than lateral movement.
Apparently the least nitrate moved under the 60 x 120 cm entrenched
digested sludge. Also, little nitrate moved 30 to 60 cm (1 to 2 feet)
below the 60 x 60 cm raw-limed entrenched sludge. Considerable con-
centrations occurred below the 60 x 60 cm digested entrenched sludge.
The concentrations of nitrate in the entrenched sludge increased with
time as the sludge dewatered and became more aerobic (Table 26). In
general, the concentrations of nitrate in the soil immediately below the
entrenched sludge were greatest when concentrations of nitrate were
greatest in the entrenched sludge above. As just described, however,
concentrations of nitrate 30 to 60 cm below the trenches apparently
depended more upon conditions below the trenches favorable to denitrifi-
cation than upon sludge levels of nitrate.
Possibilities for Denitrification — Conditions probably existed such
that considerable loss of nitrate occurred by denitrification. Measure-
ments of total nitrogen levels below and around the trenches when
compared with the control indicate indirectly that organic materials
were present which had moved out of the sludge (Table 27 and Figure 21A-
F). Organic carbon and COD measurements made on a few samples from
below the trenches also tended to support the contention that an organic
energy source utilizable by denitrifying bacteria moved out of the
entrenched sludge (Table 27). The results of detailed greenhouse trench
simulation studies also show that considerable organic materials move
out of the trenches (described in Section VI).
Gas measurements in, around, and below the trenches furthermore revealed
near depletion of oxygen below the trenches (Figures 22, 23, and 24).
Concentrations of oxygen began to increase below the raw and digested
60 x 60 cm trench treatments sooner than under the digested 60 x 120 cm
trenched sludge.
Possible Significance of Nitrogen Results — The elevated levels of
nitrate and ammonium found at considerable distances below the
entrenched sludges suggested that these materials moved from the sludge
through the soil to cause the increased ammonium and nitrate levels in
the water in the drain line. The concentrations in the drainage water
did not exceed drinking water standards, but increased with time.
Nitrate concentrations may increase further as the entrenched sludge
dewaters and becomes aerobic. Once aerobic, nitrification is supported
and denitrification is depressed. During the study, the nitrogen from
the entrenched sludge was not detected in the well water. The fate of
nitrogen in the entrenched sludge studies should continue to be
followed.
Movement of Chloride — Chloride remaining in sludge and the surrounding
soil from 17 to 19 months after entrenchment is shown in Figure 21F.
104
-------
* • * •
,7 7 &
60}-S -8 -8
1
1
Vy. 28(
7
V ^-
« 7n5-s
.2^ ^/i
7 6 ,
90 r -! ~ --I7- f^1
'7 # W1
1
1
i~ ~7
1
c56 /7 s
7 6
i
7 7r
T"
x^ i
i
i
LUDGE ZONE CONDITION
'W/ Densely rooted
vY\ Mostly subsoil
2 Top and subsoil
DETERMINATION
U. g/g dry weight
Total N
• Location
\
Cl
(A) Control (la).
Figure 21. Total nitrogen and chloride in and around entrenched sludge
17 months after entrenchment.
105
-------
/aor
!
150-
\
I
X5
7/
J4
I
7i|
v
/
/
0 /3-(
_ l
1
1
1
1
SLUDGE CONDITION
(Figs. 21, B-F)
I
Aerobic, peat-like,
densely rooted
Intermediate
I
Anaerobic, sludge-like,
no roots
DETERMINATION (Figs. 21, B-F)
yUg/g dry weight
|~ ~1
Figure 21 (continued).
Total N |
Location I
Cl
(B) Raw-limed (Ilia).
Total nitrogen and chloride in and around entrenched
sludge 17 months after entrenchment.
106
-------
I ' !~ I A/
/S
_ -M -
1*0!-
I J
Figure 21 (continued)
(C) Digested (la).
Total nitrogen and chloride in and around entrenched
sludge 17 months after entrenchment.
107
-------
/ ' /
SLUDGE ,
/ /
iso'-
Figure 21 (continued)
(D) Digested (la).
Total nitrogen and chloride in and around entrenched
sludge 17 months after entrenchment.
108
-------
c
o
__<^ __ _
-------
G
o^
30__ _ _*0. - -90- -
&J!'*
SL)
90-
/5 33
in
1 *
1
_ _/^j
ci
N
Figure 21 (continued)
(F) Digested (Ha).
Total nitrogen and chloride in and around entrenched
sludge 17 months after entrenchment.
110
-------
PERCENT OF TOTAL SOIL GAS
AS-
15
10
O
•So
loo
150
3.oo
DAYS AFTER SLUDGE INCORPORATION
Figure 22. Levels of methane, carbon dioxide, and oxygen (15 cm) below
digested sludge in 60 x 60 cm trench with time after entrenchment.
PERCENT OF TOTAL SOIL GAS
10
5
A
O —
O
loo
/So
200
DAYS AFTER SLUDGE INCORPORATION
Figure 23. Levels of methane, carbon dioxide, and oxygen (15 cm) below
raw-limed sludge in 60 x 60 cm trench with time after entrenchment,
111
-------
PERCENT OF TOTAL SOIL GAS
O
60 loo /SO
DAYS AFTER SLUDGE INCORPORATSON
ASO
Figure 24. Levels of methane,, carbon dioxide,, and oxygen (15 cm) below
digested sludge in 60 x 120 cm trench with time
after entrenchment.
112
-------
Chloride moved greater distances than nitrate and ammonium (Figure 21A
to F vs 20A to F). Chloride movement was greatest where initial chlo-
ride levels in the sludge were greatest, as contrasted to the case for
nitrate movement where denitrification modified the relationship.
Chloride movement seemed sufficient to have caused the somewhat elevated
levels of chloride in the drainage water and in underground well water.
Movement of Heavy Metals — There has been no detectable movement of
heavy metals greater than 2.5 cm (1 inch) below the trenches (Tables 28
and 29 and Figures 25A to D), There was, however, apparently a lateral
movement of metals into the soil between the trenches of digested sludge
17 to 19 months after entrenchment. There was no detectable lateral
movement 10 months after sludge entrenchment.
The reason for this lateral movement is unclear. Perhaps the higher
organic levels in the surface soil to the side compared with the sub-
surface soil below coupled with the lack of lime in the entrenched
digested sludge may have contributed to metal movement. Also, the
digested unlimed sludge on the side of the trench may have dewatered
more than the sludge on the bottom. Additional research (Appendix) has
also shown small amounts of metal movement downward into the soil out of
entrenched sludge,. Movement is related to an aerobic sludge state,
presence of nitrate-N, lowered pH, and absence of lime.
Changes in Sludge Physical Properties — Entrenched sludge dewatered
with time. The dewatering was greatly enhanced by penetration of
growing plant roots. By August 1973 three distinct zones were observed
in the 60 x 60 cm digested entrenched sludge. The first zone was
located around the edge of the trench to a depth of about 30 cm
(12 inches) and 7.5 to 15 cm (3 to 6 inches) down from the top (Zone A,
Figure 26). Sludge Zone A was densely rooted, gray in color and dry
and peat-like. The zone was very porous and aerobic and water could
easily percolate through. A similar change in sludge properties
occurred with root penetration in digested sludge in the greenhouse
trench simulation studies (Section VI).
The third zone consisted of approximately the bottom half of the
entrenched sludge (Zone C, Figure 26). Sludge Zone C was essentially
devoid of roots, very dense, black in color, and moist, and appeared to
be physically unchanged from the time it was placed in the trench. There
was little, if any, water percolation through this anaerobic sludge. A
similar Zone C was observed in the greenhouse trench simulation studies.
The second zone (Zone B, Figure 26) was the zone between Zones A and C
Sludge Zone B contained fewer roots than Zone A and was gray-brown in
color. It was considerably drier than Zone C but not as dry as Zone A.
It was moist and peat-like, was essentially aerobic, and allowed some
water percolation.
The water contents of the different zones in October and November 1973
are given in Table 30. The mean water contents of the digested sludges
113
-------
Table 28. EXTRACTABLE ZINC IN AND AROUND DIGESTED AND RAW-LIMED ENTRENCHED SLUDGE WITH TIME
Determination
Sludge type
Months after entrenchment
Trenched sludge
Below, cm
2 55,62+
15 55,75
30 55,90
45 55,105
60 55,120
Side, cm
5 25,35
15 15,35
25 5,35
Above
DTPA-TEA extractable zinc yg/g dry
Raw_,
7
0.4
0.4
0.3
0.3
0.3
0.4
0.6
0.4
-
60 x 60 cm
17
(A)* -
(B) 313
(C) 215
0.52
0.12
0.16
-
0.10
0.16
-
0.06
0.38
Digested, 60
17
(A) 1060
(B) 1065
(C) 490
0.82
0.16
0.10
-
0.16
6.72
2.20
0.20
0.36
x 60 cm Digested,
19
821 55,55
1156
1102
<0.1 55,122
<0.1 55,135
<0.1 55,150
<0.1
<0.1 55,180
4.1 25,55
9.0 15,55
4.3 5,55
-
weight
60 x
7
582
0.3
0.2
0.2
-
0.2
0.2
0.3
0.2
1.3
120 cm Control
18
(X)* 1.67
(Y) <0.1
(Z) 0.54
<0.1
<0.1
<0. 1
<0.1
<0. 1
_
<0. 1
<0. 1
-
* Regions A, B, and C represent different degrees of sludge decomposition in the trenches shown in
Figure 26 and are: (A) peat-like dry, considerable root penetration; (B) peat-like, moist, some
root penetration; and (C) original moist condition, little root penetration.
** Region X was the top 5 cm of the trenched control, region Y was the next 20 cm of the control
trench, and region Z was the bottom 35 cm of the control trench.
+ These locations are given in Figure 19.
-------
Table 29. EXTRACTABLE COPPER IN AND AROUND DIGESTED AND RAW-LIMED ENTRENCHED SLUDGE WITH TIME
Determination
Sludge type
Months after entrenchment
Trenched sludge
Below,
2
15
30
45
60
Side,
5
15
25
Above
cm
55,62+
55,75
55,90
55,105
55,120
cm
25,35
15,35
5,35
DTPA -TEA extractable copper yg/g dry weight
Raw, 60 x 60 cm Digested, 60 x 60 cm Digested, 60 x 120 cm Control
7 17
(A)* - (A)
(B) 113 (B)
(C) 58 (C)
0.54
0.34
0.32
0.30
0.64
0.36
0.46
17
365
280
22
0.44
0.40
0.34
0.36
0.54
0.36
0.42
0.52
19
352
239
130
0.44
0.23
0.39
0.23
0.22
0.33
0.31
0.28
-
7
55,55 74
55,122 0.5
55,135 0.4
55,150 0.3
55,180 0.6
25,55 0.4
15,55 0.4
5,55 0.3
0.7
18
(X)** 1.02
(Y) 0.38
(Z) 0.90
0.28
0.38
0.38
0.24
0.28
0.40
0.28
* Regions A, B, and C represent different degrees of sludge decomposition in the trenches shown in
Figure 26 and are: (A) peat--like dry, considerable root penetration; (B) peat-like, moist, some
root penetration; and (C) original moist condition, little root penetration.
** Region X was the top 5 cm of the trenched control, region Y was the next 20 cm of the control
trench, and region Z was the bottom 35 cm of the control trench.
+ These locations are given in Figure 19.
-------
'•70 /.3t> O.S'I ^ • •
p.So O.70 0.72.
_\ \ JJ
30pa; ~
-------
120
60(-
90- ^/0~ ,-
/ur 0.38 \
120-
O.3Q
SLUDGE CONDITION
(Figs. 25, B-D)
Aerobic, peat-like,
densely rootedj
Intermediate ,
i
Anaerobic, sludge-like,
no roots
DETERMINATION
Wg/g dry weight
f | Zn (DTPA-TEA)
La «J
® Location
Cu (DTPA-TEA)
Figure 25 (continued).
(B) Raw-limed (Ilia).
Extractable zinc and copper in and around entrenched
sludge 17 months after entrenchment.
117
-------
90:
O.30
to
CLL
ISO— —
Figure 25 (continued).
(C) Digested (la).
Extractable zinc and copper in and around entrenched
sludge 17 months after entrenchment.
118
-------
/ /
/ -T- _ /,
/ ' I'
/ /
/ /
/ /
/
TTop Sp/L AND, /? SLUDGE
' 6o/ ;' '90
/ 7" -?— '
' ' ' xr / /*
9.3
0.5/O.V9 /.'a.
/
301 ^3 ~^d? ^
O.&8 O3I 0.33
120
150-
J. _ _ J
Figure 25 (continued)
(D) Digested (la) .
Extractable zinc and copper in and around entrenched
sludge 19 months after entrenchment.
119
-------
Figure 26. Cross-sectional excavation of entrenched digested sludge
after 17 months (Oct. 17, 1973) showing degree of
weathering. Zone A = weathered, densely rooted, peat-
like, aerobic. Zone B= weathered , sparsely rooted,
moist peat-like, aerobic. Zone C = unweathered,
anaerobic.
120
-------
Table 30. WATER CONTENT ^DF SLUDGES AFTER ENTRENCHMENT
_-. , Water content+in sludge treatment"1"1"
Sludge
zone ** la la Ilia Ha la, Ha V
17*+ 18 17 18 19 18
A 25 36 9 18 28 6
B 53 59 18 21 50 6
C 64 67 66 58 53 7
* The principal water content of sludges was from 73-82% in May and
June 1972 (Table 4).
** Zone A = dry, peat-like; B = moist, peat-like; C = original
appearance.
+ Water percentages determined by England Laboratories, Beltsville,
Maryland.
++ Key to treatment symbols given in Table 2.
*+ Months after entrenchment.
at time of entrenchment was 73% and for the raw-limed sludge 82%. Note
the considerable decrease in water content caused by root penetration
and plant growth in Zone A and somewhat lower decrease in Zone B. The
water content of sludge, Zone C, decreased by only about 9% from 73 to
64 percent without root penetration after 17 months in the trenches.
We do not know exactly how the sludge would have dewatered in the field
without root penetration. However, in the 60 x 120 cm entrenched sludge
area in an observation pit dug in November 1973 (Figure 20F) there was a
large zone below the A zone where the appearance of the sludge changed
from black to brown and the water content decreased. Few, if any, roots
occurred in this zone. Therefore gradual dewatering and change to a
more aerobic state occurred with or without penetration of plant roots.
Insects and microorganisms must have had some effect on the dewatering.
In any event, the speed and perhaps the extent of drying was reduced in
sludge where root penetration did not occur.
121
-------
Table 31. CHEMICAL CHARACTERISTICS OF RAW-LIMED SLUDGE (60 x 60 cm) AS
INFLUENCED BY DECOMPOSING (17 MONTHS AFTER ENTRENCHMENT
TT • * -a** r+
Determination Units & ^
Raw-limed, 17 months, 10/30/73, Ilia
Total Zn4^ _ y§/§ ~ f3
Extractable Zn + Ug/g 313 215
% Extractable Zn % 46
Total Cu yg/g 150 238
Extractable Cu yg/g 113 58
% Extractable Cu % 75 24
pH wet 6.4 7.4
pH dry
Water content
NH -N
4
NO -N
3
Total N
Cl
% 53
yg/g 27.8
yg/g 1,871
yg/g 4,517
yg/g 3,517
64
2,523
105.7
9,036
4,900
* yg/g calculated on a dry weight basis.
** Sludge, moist, peat-like aerobic,
+ Sludge, anaerobic.
++ Dry ashed, taken up in HCl.
*+ 5mM DTPA, lOmM CaCl2, lOOmM TEA, Lindsay and Norvell method
(1 g sludge/50 ml solution).
The different sludge zones were observed to different degrees in all
observation pits dug in all entrenched sludge treatments. Diagrams of
their size and arrangement are shown in Figure 20 A to F.
Changes in Sludge Chemical Properties — Nitrogen - The dewatering of
both raw and digested entrenched sludge, and the resulting increase in
aerobic conditions favored the conversion of ammonium to nitrate (Figure
20A to F and Tables 31 to 34). The concentrations of total nitrogen
were generally high in each sludge zone (Figure 20A to F and Tables 31
to 34). Sufficient samples were not taken to determine if there was any
pattern of overall change in total nitrogen with dewatering.
122
-------
Table 32. CHEMICAL CHARACTERISTICS OF DIGESTED SLUDGE (60 x 60 cm) AS
INFLUENCED BY EXTENT OF DECOMPOSITION (17 MONTHS AFTER
ENTRENCHMENT)
Determination Units* A** B+
Digested, 17 months, 10/17/73, la
Total Zn*+ yg/g 1,850 1,913 1,620
Extractable Zn+* yg/g 1,060 1,065 490
% Extractable Zn % 57 56 30
Total Cu pg/g 775 1,690 668
Extractable Cu Ug/g 365 280 22
% Extractable Cu % 47 17 3
pH wet 6.9 4.8 6.9
pH dry -
Water content % 9 18 66
NH4-N Ug/g 331 439 4,392
N03-N yg/g 1,222 1,130 42
Total N Ug/g 19,567 15,810 20,983
Cl yg/g 123 1,600 5,300
* yg/g calculated on a dry weight basis.
** Sludge, densely rooted, peat-like, aerobic.
+ Sludge, moist peat-like, aerobic
++ Sludge, anaerobic.
*+ Dry ashed, taken up in HC1.
+* 5mM DTPA, lOmM CaCl2, lOOmM TEA, Lindsay and Norvell method
(1 g sludge/50 ml solution).
Chlorides - Chlorides were lowest in the most dewatered sludge (Zone A)
and highest in the least dewatered (Zone C). The chloride distribution
was most likely caused by chloride leaching from the more porous
weathered sludges into the soil (Tables 31 to 34 and Figure 21A to F).
Metals - As the entrenched sludge dewatered, a relative increase in
DTPA-TEA extractable metal concentrations, particularly copper, occurred
(Tables 31 to 34 and Figure 25A to D). Extractable copper in digested
sludge of aerobic Zone A was 3 to 15 times higher than that of anaerobic
Zone C. Extractable zinc in some trenches did not vary with sludge
123
-------
Table 33. CHEMICAL CHARACTERISTICS OF DIGESTED SLUDGE (60 x 60 cm) AS
INFLUENCED BY EXTENT OF DECOMPOSITION (19 MONTHS AFTER
ENTRENCHMENT
A
Determination Units
Digested, 19 months, 11/27/73, la
Total Znx+
Extractable Zn+
% Extractable Zn
Total Cu
Extractable Cu
% Extractable Cu
pH wet
pH dry
Water content
NH4-N
NOs-N
Total N
Cl
yg/g
ng/g
%
ug/g
Pg/g
%
%
yg/g
yg/g
yg/g
yg/g
1,764
821
47
797
352
44
4.3
5.1
36
65
950
14,069
46
2,424
1,156
48
1,036
239
23
5.4
5.4
59
558
1,007
12,984
2,058
2,387
1,102
46
968
130
13
6.8
6.8
67
3,965
57
26,069
6,420
* yg/g calculated on a dry weight basis.
** Sludge, densely rooted, peat-like, aerobic.
+ Sludge, moist peat-like, aerobic
-H- Sludge, anaerobic.
*+ Dry ashed, taken up in HC1.
+* 5mM DTPA, lOmM CaCl2, lOOmM TEA, Lindsay and Norvell method
(1 g sludge/50 ml solution).
dewatering and in others varied twofold. Extractable cadmium and nickel
(Table 34) both varied several fold with the greatest increase in the
most dewatered aerobic sludge. In most instances the total metal levels
were not appreciably different.
The reason for the increase in DTP A- TEA extractable metals is unclear.
Some of the increase was attributed to changes in pH with dewatering.
The 8-fold increase in extractable copper, which is far too great to be
explained by changes in pH, may in part be explained by the presence of
metal sulfide compounds in anaerobic sludge and not in the dewatered
aerobic sludge. Sludge was removed (Table 34) from various zones in the
124
-------
Table 34. CHEMICAL CHARACTERISTICS OF DIGESTED SLUDGE AS INFLUENCED
BY EXTENT OF DECOMPOSITION (19 MONTHS AFTER ENTRENCHMENT)
Determination
Units*
Zones taken from different locations
for metal uptake
Total Zn*+
Extractable Zn+*
% Extractable Zn
Total Cu
Extractable Cu
% Extractable Cu
Total Ni
Extractable Ni
% Extractable Ni
Total Cd
Extractable Cd
% Extractable Cd
pH wet
pH dry
Water content
NH4-N
N03-N
Total N
Cl
experiment .
yg/g
yg/g
%
yg/g
yg/g
%
yg/g
yg/g
%
yg/g
yg/g
%
%
yg/g
yg/g
yg/g
yg/g
A**
in plots la
1,336
532
40
483
217
45
58.2
7.3
13
14.8
6.0
41
5.2
5.8
28
266
2,409
19,185
145
B+
and Ila, digested
1,760
785
45
582
218
37
91.0
8.6
9
21.2
9.6
45
5.5
5.9
50
690
3,905
10,715
1,081
C++
sludge
1,027
305
30
366
26
7
111.3
7.5
7
10.1
1.0
10
8.0
6.8
53
2,742
32
16,476
2,756
* yg/g calculated on a dry weight basis.
** Sludge, densely rooted, peat-like aerobic.
+ Sludge, moist peat-like, aerobic,
++ Sludge, anaerobic.
*+ Dry-ashed, taken up in HC1,
+* 5mM DTPA, lOmM CaCl2, lOOmM TEA, Lindsay and Norvell method
(1 g sludge/50 ml solution).
125
-------
field and brought into the greenhouse to determine if differences in
extractable metals would be reflected in metals absorbed by corn, beans,
or chard. The experiment was not completed at the time of writing this
report.
Plant Response
Sweet Corn 1972 — Two varieties of sweet corn were planted on the plots
in rows traverse to the direction of sludge entrenchment in 1972 as
shown in Figure 14. The most vigorous growth of sweet corn, both silver
queen and Iowa chief, occurred on the digested 60 x 60 cm plots (Figure
27A) . Little difference was observed on growth of corn on the disked or
disked and ripped plots.
The second best plant response occurred on the raw-limed 60 x 60 cm
plots (Figure 27B). In this case growth of corn on the disked and
ripped plots was better than growth on the disked only plots. The third
poorest growth occurred on the digested 60 x 120 cm plots (Figure 27C)
and the raw-limed liquid 60 x 120 cm plots (Figure 27D). There was
little benefit or detriment from ripping in addition to disking the
digested 60 x 120 cm plots. Ripping was not performed in the raw-limed
liquid plots.
Growth of corn was better on the digested than on the raw-limed
60 x 60 cm entrenched sludge plots because of the greater initial toxic
effects of the raw-limed sludge on plant growth. The toxic effects
probably were caused by low oxygen and the presence of ammonia and toxic
volatiles. The ammonia resulted from the alkaline pH of the raw-limed
sludge and the volatiles from anaerobiosis produced by the readily
decomposable organic materials and the wet conditions. Greenhouse and
laboratory studies have shown that low oxygen, ammonia, and volatiles
can inhibit root growth. The responsible volatiles have not been
identified.
One might expect, therefore, that ripping (mixing and diluting) the raw-
limed sludge into soil would hasten the decomposition and conversion of
the sludge to a more stable form and shorten the period of initial
toxicity. The decomposition should benefit crop growth. As previously
stated, ripping did improve corn growth in the raw-limed entrenched
treatment. Ripping did not show any benefit to crop growth with the
more stable entrenched digested sludge.
A series of greenhouse trench simulation studies, which partly preceded
and partly followed the field studies, showed that corn roots did not
penetrate more than a few inches into raw-limed entrenched sludges
during the 5-month period. On the other hand corn roots rather quickly
penetrated digested sludge. In the greenhouse as in the field, corn
growing in the digested sludge tests was better than in the raw-limed
sludge tests.
126
-------
(A) Growth on 60 x 60 cm digested sludge disked plot la.
(B) Growth on 60 x 60 cm raw-limed sludge plot Ilia;
left of pole — corn on disked and ripped notice-
ably larger than corn on right of pole — disked
only.
Figure 27. Sweet corn growing on sludge plots, August 1972,
127
-------
(C) Growth on 60 x 120 cm digested sludge plot Ila; left of pole --
corn on disked and ripped only slightly better if at all than
corn on right of pole — disked only.
(D) Growth on 60 x 120 cm raw-limed liquid sludge disked plot IVa.
Figure 27. Sweet corn growing on sludge plots, August 1972,
128
-------
All corn growth was rather poor for several probable reasons. First,
the soil was extremely sandy and the initial attempts at irrigating were
inadequate because of the incomplete irrigation system originally avail-
able. Secondly, the surface 30 to 37 cm (12 to 15 inches) of soil
covering the entrenched sludge was predominately a sandy subsoil low in
plant nutrients. This subsoil received chemical phosphorus and potas-
sium fertilization and lime, but little or no chemical nitrogen ferti-
lizer was applied. The corn plants had to grow down about 12 cm before
their roots penetrated the subsoil cover over the sludge to obtain
sludge nitrogen. Growth was not as bad as it might have been because
disking of the plots and spillage during entrenchment resulted in some
sludge in the surface layers of soil. Thirdly, the corn suffered damage
from wildlife which abounded on the entrenchment site.
Growth of corn on the digested and raw-limed 60 x 60 cm entrenched
sludge treatments was better than on the digested and the raw-limed
60 x 120 cm treatments for at least two reasons: (1) there was closer
spacing between the trenched sludgey and (2) a thinner cover of soil
over the sludge.
Rye 1972-73 — Little definitive data were recorded on the rye crop.
Where spacing between trenches averaged 275 cm (9 feet) in the raw-limed
60 x 120 cm plots, the rye growth was very uneven (Figure 28). Where the
trenches were 60 cm apart, little unevenness in growth response was
observed.
Fescue Growth 1972-73 — Not all crops suffer from initial toxicity to
the same degree. Kentucky-31 tall fescue, for example, was more tol-
erant of the initial toxic effects of sludges than corn. Some of the
best growth of fescue occurred in the raw-limed 60 x 60 cm trench plots.
Fescue roots showed little penetration of raw or digested sludge in the
field in 1972 (Figure 18B), but since fescue is a perennial crop with
continued growth in 1973, extensive penetration of the top foot of the
digested entrenched sludge occurred along with changing of sludge prop-
erties (Figures 18A and 26). Root penetration was also observed in the
entrenched raw-limed sludge to a lesser degree.
The benefits of entrenched sludge on fescue growth can be seen even in
December in a photograph of fescue growing on a control trench area
where several trenches had been mistakenly filled with sludge (Figure
29). Note also the better growth on the digested sludge entrenched area
to the right.
The concentration of heavy metals in tops of tall fescue is given in
Table 35. These concentrations must be considered only as trends
because of limited data. In attempting to understand the results
consider first of all that zinc is readily absorbed and translocated to
the tops of fescue, while nickel and copper are less readily absorbed
and particularly less readilv translocated to fescue tops. Secondly,
of the three elements, copper absorption is most readily enhanced when
in association with a chelate. Chelates are most abundant in an anae-
robic sludge and decrease as sludge dewaters and becomes aerobic. This
may explain part of the decrease in copper and nickel uptake with time.
129
-------
' ' ' '.**',
u>
o
If -
Figure 28. Rye growing on raw-limed liquid sludge plot IVa in May 1973. Note the pronounced
greater vigor of rye growth over the areas where the sludge was entrenched.)
-------
|*»K'-;t,' Vj>' ^J?:' . V^ ' " JP _,_•".
Figure 29. Fescue in December 1973 growing over entrenched digested
sludge on plot la in upper right hand corner above line
and over control V on left side of photo. Arrows point
to fescue growing over areas in control where sludge was
entrenched by mistake.
131
-------
As a third fact, the uptake of heavy metals from the soil or the sludge
is greater under acidic than under neutral or basic conditions. The raw
sludge treatments were limed and initially had higher pH levels (Table 5).
With time, however, the pH of both the raw and the digested entrenched
sludges became similar (.Tables 31 to 34). A fourth fact is that the
relatively high levels of phosphate in sludge reduce the availability of
metals to plants.
As a fifth factor, the uptake by a given plant species is dependent upon
the total metal level present. The raw sludge had approximately one-
fourth to one-half as much total zinc and copper as the digested sludge
(Tables 31 to 34). Finally, the roots of plants penetrate raw sludge
less readily than digested sludge and have less root absorptive surface
exposed to metals.
Looking at the uptake-translocation of heavy metals into tall fescue
tops on a given date (Table 35), the zinc uptake was apparently the only
metal uptake significantly affected by sludge properties and trenching
method. The relative rank as to amount of zinc uptake by the fescue
was: digested &0 x 60 cm (I)> digested 60 x 120 cm (II) = raw-limed
liquid 60 x 120 cm (IV) = trenched control (V)> raw-limed 60 x 60 cm
(III)> surface control. At this time roots had not penetrated to a
great degree through the deeper soil cover over entrenched sludge in
plots II and IV.
Zinc uptake-translocation from the trenched control (V) was greater than
from the surface control, probably because crops were growing in the
acid subsoils. These acid subsoils were low in phosphate and organic
matter levels — all conditions that promote uptake-translocation of
zinc to fescue tops.
Uptake-translocations of zinc from the raw-limed sludge trench plot
(III) was even less than uptake from the trenched soil control (V),
apparently because the excess lime in the sludge raised the subsoil pH
and decreased zinc uptake, because the high sludge phosphate concentra-
tion decreased zinc uptake, and because the total metal concentrations
were one-fourth to one-half of that in the digested sludge. In this
case sludge reduced uptake of metals to levels lower than those which
naturally occurred from the acid subsoil of the trenched soil control.
Uptake-translocation of zinc was least in the unsludged surface soil
control where no sludge metals were added and where higher phosphate and
organic matter and lower acidity reduced uptake of native metals.
Uptake of zinc, copper, and nickel was less for all treatments in
November 1973 than in September 1973, and indicated that zinc in the
sludge had become slightly less available and copper and nickel in the
sludge considerably less available with time after the sludge was
entrenched. The decrease in availability was in contrast with increased
DTPA-TEA extractable (available or potentially toxic) sludge zinc,
nickel, and particularly copper as sludge dewatered (Tables 31 to 34).
The reason for the decrease in uptake-translocation of copper and nickel
132
-------
in 1973 is not known. Perhaps it was due to destruction of plant-
absorbable chelates of these metals by the action of dewatering and the
aerobic conditions. On the other hand uptake-translocation of both
copper and nickel were also less in unsludged controls in 1973 than in
1972.
Soybeans-1972 — There was essentially no yield of beans because of wild
animal injury to the crops.
Fruit and Shade Trees - 1972-73 — Fruit trees were planted in 1972 and
1973, according to the plan indicated in Table 36 and Figures 15 and 16,
in completely fertilized controls and without fertilizer in the trenched
areas. Fruit trees, started in 1972, were planted too late in the
season. The fruit trees also were held dormant too long and as a result
some varieties died enmasse. As an exception, however, the peach trees
faired very well. An exaggerated example of the effects of a tree being
planted in a trenched area compared with a control is shown in Figure 30.
The trees were planted in June 1972 and the photographs taken in October
1972. While the control tree received complete fertilizer, 225 mm
(9 inches) of rain which fell during one week shortly after planting
leached out most of the nutrients. The tree planted between two 120-cm
deep trenches, however, received the same rain. In the latter area,
however, the rain did not wash away the sludge-contained nutrients. The
improved growth of the peach tree in the sludged area may also have been
related to better water capture because it was planted in an area where
the ridges were not flattened.
Peach tree growth in 1973 was more vigorous than in 1972 in both the
sludge entrenched areas and in control areas. Control areas, however,
still did not support tree growth as well as sludge entrenched areas.
Most fruit trees planted in the spring of 1973 have survived. Peach
trees are the fastest growing species. Differences between the growth
of the slower growing tree species in the sludged and fertilized control
areas were less readily apparent.
Analyses of peach tree leaves in 1972 to 73 show that some metals were
being absorbed into the leaves (Table 37). Whether these metals would
move in any quantity into the fruit and whether the movement would be a
nutritional benefit or hazard remains to be seen in several years when
the trees begin to produce fruit.
Shade trees planted in 1973 were small and were planted during the
middle of the summer. We were unable to adequately water and care for
the trees, and most died whether in control or trenched areas. The
shade trees were replanted in 1973 according to the plan in Table 38 and
Figures 15 and 16. These trees were again small and arrived late from
the supplier. No significant observations can yet be made on the rather
small amount of growth that has thus far occurred. We gave these trees
better care, however, and 85 percent have survived. We replanted the
trees in the spring of 1974.
133
-------
Table 35. UPTAKE OF HEAVY METALS BY KENTUCKY-31 TALL FESCUE
OJ
Metal, mg/kg dry sludge
Treatment
I
I
II
II
III
III
IV
V
External
Plants directly
Tillage
L
D
DR
mean
L
D
R
mean
L
D
R
mean
B
Control4"1"
Control4*
9/1/72** ll/14/73+
Zn
92
74
98
91
57
50
68
56
29
30
34
31
50
50
21
Cu
12
14
16
14
11
11
22
13
11
14
17
14
14
12
10
Ni
6
4
7
6
6
5
6
6
5
3
2
3
4
6
5
Zn
70
-
105
87
48
-
-
48
20
18
22
20
-
57
14
Cu Ni
5 2
-
7 3
6 2
6 2
-
- -
6 2
4 <1
4 <1
4 <1
4 <1
-
5 2
3 2
9/1/72
Pb
9
9
9
9
8
11
12
10
10
9
9
9
9
12
9
over excavated
trench
la
Ilia
286
37
8 9
6 4
* L = left in ridges; D = leveled and disked; DR = leveled, disked, and ripped;
B = backfilled, leveled, and disked
Continued
-------
Table 35 (continued). UPTAKE OF HEAVY METALS BY KENTUCKY-31 TALL FESCUE
** Values were means of one representative sample each from treatment la and Ib. Background
subtraction for light scattering interference was not applied for any element.
+ Values in only about one-half of the cases were means of one representative sample each
from treatment la and Ib; other values are for representative sample from treatment la
and Ib. Background subtraction for light scattering interference was applied to Ni
determinations only.
+4- Control that was trenched supposedly without sludge, but possibly had some sludge contami-
nation in the soil surface.
+* Control external to the sludge plots which had no possibility for contamination.
-------
Table 36. FRUIT TREE STATUS ON DECEMBER 4, 1973
Tree Row*
(i)
(ii)
(iii)
(iv)
(v)
(vi)
(vi)
Direction ^ ™
E Mop**
A
dd
NE Sc
A
NE Ya
A
N Ra
A
N Ya
A
E Mop
D
E Mop
D
Tree Number
2
Map
D
Vc
A
Ya
A
Sc
D
Ra
A
Mop
A
small
Mop
A
small
3
Mop
A
Vc
A
Ya
A
small
Sc
D
Ga
A
Jp
A
large
Jp
A
slight
dd
4
Map
A
Ba
A
Op
A
Vc
D
Ram
D
6p
A
JP
A
5
Mop
A
dd
Sa
A
Map
D
Ba
A
Op
A
Jp
A
small
6p
A
6
Jp
A
much
dd
62p
A
Map
A
Sa
A
Map
A
7
6p
A
mdd
large
62p
A
U4 ,,
- Dig —
Fp
A
Sa
A
Map
A
8
Jp
A
mdd
62p
A
Sp
A
62p
A
Fp
A
9
Jp
A
some
dd
SP
A
62p
A
Sp
A
PI nt-
10 Plot
Jp Ha
A 120 cm dig
large
la
60 cm dig
la
60 cm dig
62p Ib
A 60 cm dig
Sp Ib
A 60 cm dig
a
control
a
control
Continued
-------
Table 36 (continued h FRUIT TREE STATUS ON DECEMBER 4, 1973
Tree Number
Tree Row
Direction
Plot
10
(vii)
(viii)
E 61p
A
E Flp
A
61p
A
IP
A
Sa
A
Map
A
Ba
A
Map
A
Vc
A
Op
A
Vc
A
Ga
A
Sc
A
Ra
D
b
control
b
control
Row locations on entrenched plots are given in Figure 16 except for control.
** Key: A = alive
D = dead
dd = deer damage
Mop = Moonglow pear
Map = Magness pear
Op = Old Hone pear
Jp = Jefferson peach
6p = 6409 peach
62p = 62290 peach
61p = 6419 peach
Sp = Satsuma plum
Fp = Fruar plum
Flp = F13-60-53 plum
lp = 19941 plum
Sc
Vc
Ba
Sa
Ya
Schmidt cherry
Vista cherry
Blemril apricot
Sungiant apricot
York apple
Ra = Red Delicious apple
Ram i Red Delicious apple/MM106
Ga = Golden Delicious apple
-------
OJ
CO
.
, '•
• '" • -
••''•>.
< ••..••;"**->-:-^*
Figure 30. Jefferson peach trees, similarly sized seedlings transplanted into soil
between entrenched digested sludge and fertilized control soil
in June 1972, photographed October 1972.
-------
Table 37. HEAVY METAL LEVELS IN PEACH TREE LEAVES
Date
Metals yg/g of dry leaves from Jefferson peach
Zn
Cu
Ni
Pb
Control
72 23.0
73 23.3
Digested plot Ila
(60 x 120 cm)
72
73
49.5
48.3
6.0
5.3
9.3
6.9
2.3
<0.5
2.2
<0.3
11.2
8.8
Comparative Crop Response on Plots
and "b" — The bulk of the 1972
and early 1973 crop observations were made in the "a" plots. The "a"
plots received better irrigation and cultivation than the "b" plots
because of the wet conditions in the latter area. During 1972, plots Ib
and Illb were very wet and did not yield good crops. Plot Ib and in
part IHb dried considerably during the summer of 1973. These areas
have now been seeded with crops that can be studied in 1974. Prior to
drying, part of plot Ib was so wet and difficult to work that many
vehicles became mired. Considerably greater mixing of soil and sludge
occurred in that region.
139
-------
Table 38. SHADE TREE STATUS ON DECEMBER 4, 1973
Tree row
(xi)
(xii)
(xiii)
(xiv)
(xv)
(xvi)
(xvii)
(xviii)
(xix)
Di rert: inn
1
N WO**
A
N SXG
G
N WO
G
N RO
A
N AS
A
N SG
X
N WW
A
N SXG
D
N SG
G
tree number
2
RO
A
UP
A
WO
D
RO
G
AS
A
SG
X
X
SXG
D
SG
A
3
RO
A
UP
A
NM
G
NM
D
AS
A
SG
*
TP
A
WO
A
SG
A
4
WO
D
SXG
NM
D
NM
D
PO
A
AS
A
TP
A
UP
A
WB
A
5
WO
G
SXG
G
NM
D
NM
A
PO
A
SG
G
TP
A
WO
D
WG
A
6
NM
A
UP
G
RO
A
NM
D
PO
A
AS
G
X
UP
A
WG
A
7
NM
A
AE
X
RO
A
WO
D
PO
A
WG
A
WO
D
WO
G
NM
A
8
NM
A
AE
X
RO
A
WO
A
SM
A
WG
A
WO
A
NM
A
NM
A
9
AE
X
TP
A
SXG
D
WO
A
UP
D
WG
A
TP
A
Nh
A
AS
X
10
TP
SXG
A
dd
WO
A
UP
A
WG
A
SXG
A
NM
A
AS
X
11
TP
A
SXG
D
TP
D
SM
A
UP
A
RO
A
RO
A
AS
X
12
WO
G
AE
X
TP
A
SM
A
UP
G
RO
A
NM
D
13
AE
X
TP
D
SM
A
UP
A
RO
A
14
AE
X
TP
D
RO
A
UP
D
RO
A
15
AE
X
RO
A
AS
A
Continued
-------
Table 38 (continued). SHADE TREE STATUS ON DECEMBER 4, 1973
Tree number
Trpp rnw" Di rpr r i nn
(xx)
(xxi)
(xxiii)
(xxiv)
(xxv)
control
(xxvi)
* Row
** Key :
N
E
E
N
N
N
locations on
TP = tulip
1
TP
A
AS
A
NM
A
UP
A
WG
A
NM
A
2
UP
A
AS
A
NM
A
UP
A
WG
A
NM
A
entrenched
poplar
3
UP
A
AS
A
NM
D
UP
A
WG
A
NM
A
plots
WW = weeping willow
WG = willow
green
AE = American elm
UP = Ulmus
WO = willow
parif olia
oak
4
UP
G
SM
D
X
SG
D
AE
X
SM
A
5 6 7 8 9 10 11
UP UP PO PO PO SM SM
A A A A A A A
SM SM
D D
dd dd
RO RO
A A
SG SG
D A
AE AE TP TP TP WO WO
X X A A A A A
SM SM RO RO RO PO PO
A A A A A A A
12 13 14 15
SM NM
A A
WO AS AS AS
A A A A
PO SXG SXG SXG
ADD D
are given in Figure 16 except for controls.
PO =
RO =
NM =
Sm =
SXG
SG =
pin oak D = dead
red oak A = alive
Norway maple dd = deer damage
Silver maple
= Sour gum
Sweet gum
G = gone
X = not planted
-------
SECTION V
SLUDGE pH TRIALS
INTRODUCTION
Liming sludges to pH 11.5 reportedly destroys pathogens. Liming can
also influence availability of trace metals to plants and the release of
nitrogen to plants and soil. In the trench studies of Section IV, we
looked at the influence of high lime treatment in raw sludge only. In
the following trials lime was applied to raw and digested sludge, and
the sludges were incorporated into soils in surface and trench plots.
In practice the amount of lime applied elevated the sludge pH to values
ranging from just above the untreated sludge value (6.4 to 7.4) to in
excess of 11.5. These trials were performed to observe the effects of
liming to several different pH values on the survival of coliforms and
salmonellae, on the fate of sludge nitrogen, on the sludge and soil pH,
and on the growth of plants.
PROCEDURES
Digested and raw sludges were limed and treated at the Blue Plains
(Washington, D.C.) and the Little Hunting Creek (Virginia) wastewater
treatment plants respectively as shown in Table 39. These sludges were
then trucked to Beltsville for incorporation into the trench and surface
plots shown in Figure 31. Sludges began arriving on July 18, 1972.
They were sampled and then incorporated into the plots.
For the trench plots, sludges were incorporated into two parallel
3-meter (10 foot) long trenches, 60 cm wide x 60 cm deep x 60 cm apart
and covered with the excavated soil to a depth of approximately 30 cm
(1 foot) (Figure 31). This trenching rate is equal to 735 dry metric
tons/hectare (320 dry tons/acre). For the surface plots, the sludges
were mixed into the surface 15 cm (6 inches) of soil with a rototiller
at rates of application that varied between 55 to 115 dry metric
tons/hectare (25 to 50 dry tons/acre). The surface plots were approxi-
mately 4,5 meters (15 feet) square. The plots were located on Galestown-
Evesboro sandy loam soil just south of the plots described in Section IV.
Samples of the newly arriving sludges were analyzed for pH, nitrogen,
and most probable number (MPN) of coliform and salmonella bacteria. The
unreplicated plots were sampled periodically over a 17-month period.
Five core samples of each entrenched sludge treatment were made into
treatment composite samples on each sampling date. These core samples
were taken from the interior of the trenches. Similarly five core
samples from each soil-sludge surface treatment were made into surface
treatment composites on each sample date. The core samples from the
surface treatments were taken to a depth of 15 cm. Rye and alfalfa, and
subsequently fescue, after the rye, were planted as shown in Figure 31.
Plant response was rated.
142
-------
Table 39. INITIAL CHARACTERISTICS OF DIGESTED AND RAW SLUDGES
-P-
OJ
% Total Added before dewatering
solids in % of dry sludge basis
Source
Blue Plains **
(Washington,
D.C.)
Digested
Little
Hunting +
Creek, Va.
Soil control
Date
7/18/72
7/19/72
7/21/72
7/20/72
7/21/72
7/20/72
7/19/72
pH filter cake Lime FeCl_ Polymer
•J
5.8
8.5
10.5/11.0
12.3
6.4
11.2
12.1
5.3
23
27
34
29
13
16
17
0 2.20 0.075
3.6 2.90 0.086
4.6 0.28 0.086
13.6 6.95 0.086
o - -
3.0 1.1
4.5
% organic
of dry sludge
entrenchment
18.3
19.8
20.6
18.0
25.9
29.2
25.6
carbon *
of surface
treated soils
12/25/74
2.98
3.04
4.39
3.24
5.18
1.73
2.01
1.00
* Calculated in Biological Waste Management Lab., ARS.
** Data supplied by Owen W. Taylor, Sludge Processing, Blue Plains, Washington, D.C.
+ Data supplied by Buddy Morrison, Little Hunting Creek, Va.
-------
^CS rc^d
£ v
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Rye. * S 3
a/A/A'V" o 5.
Lrf- // / ^ ^ if / 1 'j
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Sludoe I |
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7~r-enc.h &0 x 60cm
0B 0B 00 00
Surface 15 -3.0 cm
*+ 1 4 3
H- 1 V 3
R C D F>
Q ° 1 Q
N G
U T £ LJ
? T-
i- e-
n
< A/
-^. /y
\/ V
01 00
3 3
/ ^
R D
bJ GE
S
T
E
D
©
•' / (very poor) - S (very
Figure 31. Trench and surface plot layout for sludge pH investigations with April 1973 crop ratings.
-------
RESULTS AND DISCUSSION
DH
The initial sludge pH values in Table 39 were determined at the treat-
ment plant and the initial and subsequent pH values in Table 40 were
determined in our laboratory. The differences in initial values were
probably a result of an actual change in pH from time of preparation to
time of delivery. There was also, of course, the problem of variability
encountered in sampling a large mass that may not have been homogeneous.
The initial pH ranges from 6.8 to 10.6 for the entrenched digested
sludges and from 6.5 to 11.2 for the entrenched raw sludges (Table 40)
were respectively narrowed to values of 7.0 to 7.6 and 6.4 to 7.6
within 3 months after entrenchment. By the end of 17 months, the pH of
the unlimed digested and raw sludges had dropped to 5.1 and 6.1, respec-
tively. Limed digested and raw sludges, as expected, were buffered more
than the unlimed sludges, and pH values remained above 6.1 and 6.8,
respectively. The pH of the surface plots were rapidly elevated to the
levels shown in Table 40 by addition of the different sludges, and after
3 months reached more or less a new equilibrium.
Organic Matter
As one would expect, the organic content of the digested sludge was
lower than that of the raw sludge (Table 39)- The soil organic matter
contents of the surface application plots were substantially increased
by the addition of the sludge. The range in organic matter values
reflected, within the rather large limits of sampling and analytical
error, the range in rates of sludge addition to the plots.
Total and Fecal Coliform
As shown in Figure 32, the MPN's of total coliforms in the trench plots
were initially much lower in the high pH sludge than in the low and
intermediate pH sludge treatments. One to three months after entrench-
ment in the soil, the coliform numbers in the high lime treatments had
increased while those in the other treatments with the exception of the
pH 10.0 treatments in the digested and raw trenches had decreased.
There was little, if any, real difference in coliform survival between
the treatments with and those without lime. Apparently, the high lime
treatment greatly decreased coliform numbers initially, but later
actually stimulated growth, perhaps through solubilization of substrate
for use by the bacteria or by production of a more favorable pH for
their growth after conversion of Ca(OH)2 to CaC03 .
During the period from the third month to the 17th month after entrench-
ment, the MPN of total coliforms in the raw and digested sludges
fluctuated around a mean of 10 MPN per gram. The variability in total
coliform numbers was considerably greater in the digested than in the
145
-------
Table 40. ENTRENCHED AND SOIL-MIXED SLUDGE pH WITH TIME
pH
Months after sludge entrenchment
Sludge
Type
Digested
Raw
Control
Digested
Raw-
Control
0
7/18-22/72
6.4
8.5
10.0
11.7
6.5
11.2
11.8
5.3
6.4
8.5
10.0
11.7
6.5
11.2
11.8
5.3
0.25
7/26
-
-
-
_
-
-
-
6.2
6.7
7.8
8.1
6.4
7.9
8.0
5.6
0.5
8/1
6.8
7.2
7.9
10.6
6.5
9.6
11.2
5.4
6.3
7.0
7.8
7.8
6.8
7.8
7.4
S.2
3
10/10
7,0
7.5
7.3
7.6
6.4
7.6
7.4
5.1
Months
5.2
5.9
7.1
7.4
4.9
7.1
7.4
4.8
4
11/20
6.9
7.0
7.3
7.1
6.7
7.2
7.0
4.6
6
1/31/73
6.1
-
-
6.6
_
-
-
5.5
8
3/30
4.6
6.4
6.1
6.7
6.7
7.8
6.8
4.4
9
4/26
7.1
7.4
7.5
7.4
7.2
7.4
7.3
6.0
10
5/30
6.7
7.3
7.2
7.1
7.5
7.3
7.0
5.0
17
12/13
5.1
6.4
6.8
7.0
6.1
7.3
7.2
5.2
after surface mixing
5.1
5.6
6.8
7.4
5.1
6.9
7.5
4.9
6.4
6.2
6.3
7.3
5.7
7.1
7.4
6.1
5.2
6.1
6.2
6.6
5.6
6.5
6.8
5.2
6.1
6.4
6.6
7.2
6.0
7.1
7.2
6.2
5.6
6.8
6.0
7.2
4.8
5.0
7.2
5.0
5.4
6.2
6.7
7.6
5.2
7.3
7.5
5.4
-------
c! o
Rau)
, Trench
I // I
X2 /7
Digested Sludjt, Trench
'. \ '
initial pH '•..
6.3 o h
/ao D
//. 7 A
I //1
K
g
o
o -,
Raw Sludge, Surface
O/ jested Sludqc, Surface
an o
MONTHS AFTER INCORPORATION
o -,
Figure 32. Survival of total coliform in entrenched and surface incorporated limed and unlimed raw
and digested sludges.
-------
Rak> Sludge., Trench
Sludge, Trench
inrfial pH
(,.3 o-
«s Q
10.0 Q
//•7 A
*O.A /M
f\-
a. '' n
Sludge, Surface
a. 17
MONTHS AFTER INCORPORATION
Figure 33. Survival of fecal coliform in entrenched and surface incorporated limed and unlimed raw
and digested sludges.
-------
raw sludge. Total coliform counts in the sludges did not really change
much after the third month of entrenchment.
In the surface plots, as in the trench plots, the initial numbers of
total coliforms were lower in the high lime treatments, but by the end
of the sampling period, there was little difference in the treatments.
Again there was a much greater variability in coliform numbers in
digested than in raw sludge. The coliform numbers in the digested
sludge treatments seemed to decrease in the winter months and increase
again in warmer weather.
The MPN's of fecal coliforms in the entrenched raw and digested sludges
are shown in Figure 33. As with total coliforms, the numbers of fecal
coliforms were initially much lower in the high pH sludge than in the
low and intermediate pH sludges. As with total coliform survival at
1 to 3 months after entrenchment, there was little, if any, real dif-
ference in fecal coliform survival in the sludge treatments with and
without lime. The MPN of fecal coliforms in both raw and digested
sludges averaged about 10 MPN per gram with counts only slightly
higher, if at all, in the raw sludge treatments.
As shown in Figure 33, the fecal coliform data for the trench and
surface plots were similar to those of the total coliform data with the
initial difference in MPN counts for the lime treatments disappearing
with time. The proportion of fecal coliforms surviving by the end of the
study, however, was smaller than in the case of the total coliforms.
This was essentially true for all treatments in both trench and surface
plots.
The rapid decrease in distinguishable differences of lime effects on
coliform numbers in sludge probably coincided with the conversion of
excess Ca(OH)2 to CaC03 and the resultant near equalization of pH among
the treatments. As the pH decreased in the high lime treatments, the
few coliform microorganisms present began to multiply and grow. Numbers
therefore of both total and fecal coliform microorganisms are not a good
index of pathogenic organisms that are incapable of growth outside of
their human host.
Salmonellae
Salmonellae survived at least 8 months in the trenches and up to 17
months in the surface treated plots (Table 41 and 42). As with coli-
forms, the lime treatments (including the highest lime treatment), while
reducing the levels of Salmonellae to very low numbers initially, were
not effective in their elimination. The salmonellae apparently regrew,
as did the coliforms, when pH conditions became more favorable. Unlike
the coliform bacteria, however, these organisms persisted only at low
levels. They were usually below the detectable limits within 3 months
after incorporation into the surface and trench plots. Persistence was
somewhat greater in raw than in the digested sludges. There was no
149
-------
Table 41. SURVIVAL OF SALMONELLA BACTERIA IN ENTRENCHED LIMED AND UNLIMED RAW AND DIGESTED SLUDGE
Un
O
Salmonellae
Sludge
Type
Digested
Raw
Initial
PH
6.4
8.5
10.0
11.7
6.5
11.2
11.8
Months after
0
7/8-22/72
34
14
21
<61
227
44
13
1.5
9/1
8
<8
42
17
<3
<7
<10
3
10/10
<5
<6
<6
<4
<4
<6
<8
4
11/21
<4
<4
<5
<5
<4
<5
5
, MPN/g dry weight
sludge entrenchment
6
1/31/73
6
17
<6
<5
<5
22
34
8
3/30
<6
<5
7
<7
410
<5
<6
10 12 17
5/30 7/18 12/13
<10 <10 <7
<10 <12 <6
<15 <10 <7
<10 <1 <5
<12 <13 <8
<11 <10 <7
<11 <14 <6
Control
5.3
<3
<3
<4
<3
<3
<7
<6
<3
-------
Table 42. SURVIVAL OF SALMONELLA BACTERIA IN SOIL SURFACE INCORPORATED
LIMED AND UNLIMED RAW AND DIGESTED SLUDGE
Salmonellae, MPN/g dry weight
Months after sludge entrenchment
Sludge
Type
Digested
Raw
Initial
pH
6.4
8.5
10.0
11.7
6.5
11.2
11.8
0
7/18-22/72
33
4
99
7
23
7
3
1.5
9/1
<3
9
12
18
<3
11
6
3
10/10
<4
< 4
110
<10
< 3
<4
<4
4
11/21
<4
<4
<4
<4
<4
<4
18
6
1/31/73
4
<4
< 4
<4
4
4
<4
8
3/30
<4
< 4
<4
9
4
< 4
< 4
10
5/30
< 7
< 7
< 6
< 9
< 7
50
<7
12
7/18
< 6
< 6
< 6
< 6
<6
< 6
< 6
17
12/13
< 3
< 3
< 3
<4
3
7
<3
Control
5.3
< 3
<4
<4
< 4
< 6
< 6
-------
noticeable effect of liming on long-term persistence. During the 17
months a few samples positive to salmonellae were found at random among
the treatments in both the raw and digested sludges. Fewer positive
samples were found in the entrenched sludges than in the surface applied
sludges.
Nitrogen
While large quantities of ammonium-nitrogen (NH^-N) were found shortly
after sludge entrenchment (Table 43), little NIfy-N was present at zero
time in the higher pH raw sludges and the highest pH digested sludge.
Volatilization of the NH^-N during liming, dewatering, and transpor-
tation to the site caused low initial ammonium concentration. Low
oxygen levels found initially to entrenched sludges of Sections IV and
VI indicated that these entrenched sludges were also initially anae-
robic. After the initial increase in Nlty-N, the concentrations of NH^-N
decreased with time. The fate of the ammonium is not known. Possibly
it was immobilized or denitrified as the sludge became more aerobic. If
nitrified, it must have been rapidly denitrified because the quantities
of nitrate are not large enough to account for ammonium which disap-
peared the first 10 months. In almost every instance there was less
ammonium present in the high than in the low pH sludge.
From 1.5 to 8 months after entrenchment more ammonium was found in the
raw than in the digested entrenched sludge, and this reflected the
expected larger amounts of more readily mineralizable nitrogen in the
raw sludges. Variability in later samplings make extended comparison
difficult.
In the study all samples were analyzed for nitrite and none was detec-
ted. Nitrate began to appear between the 10th and 12th month in both the
digested and raw entrenched sludges. By the 12th month more nitrate was
present in the entrenched digested sludge plots than in the entrenched
raw sludge despite higher ammonification rates in the earlier months for
the raw sludge plots.
The considerable increases in the nitrate-nitrogen (NO^-N) concentra-
tions, particularly in the digested sludges 12 to 17 months after
entrenchment, probably also occurred in the large entrenchment plots
(Section IV). The observed nitrate increases in these small plot
studies probably correspond with the significantly greater movement of
nitrate under the large digested sludge plots (I) than under the large
raw-limed plots (III) (Section IV).
The drastic increases in NC^-N concentrations with time, particularly in
the digested sludge, probably also corresponded with sludge dewatering.
Sludge dewatering is accelerated by root penetration, which in turn was
much faster in digested than raw sludge. This dewatering caused the
sludge to become peat-like, aerobic, and porous (See Section IV).
152
-------
Table 43. NITRATE AND AMMONIUM NITROGEN WITH TIME AFTER ENTRENCHMENT OF LIMED
AND UNLIMED RAW AND DIGESTED SLUDGES IN SOIL
Sludge
type
Digested
Raw
Control
Digested
Raw
Control
Initial
pH
6.4
8.5
10.0
11.7
6.5
11.2
11.8
5.3
6.4
8.5
10.0
11.7
6.5
11.2
11.8
5.3
NO
-------
Concentrations of Nlfy-N in surface-incorporated digested and raw sludges
initially averaged about 350 ppm (Table 44). During the first 3 months,
except immediately at the time of entrenchment, the high pH limed
digested sludge contained lower concentrations of NH^-N than the low pH
limed digested sludges. The concentrations of NH^ —H dropped to low
equilibrium levels of 3 to 5 ppm about 3 months after sludge incorpor-
ation except in the digested low pH limed sludge.
The levels of nitrate in soil-sludge surface plots generally increased
for 3 months after incorporation. As in the trench plots, no nitrite
was detected. There was a slight but persistent reduction in NOo-N in
the soils treated with high pH limed sludge. As winter approached
NO^-N levels became very low. They increased in the summer and then
decreased again in the winter. There was little difference in
NO -N concentrations in soils treated with raw or digested high or low
pH limed sludge.
Plant Response
The growth responses of alfalfa and rye in soil amended with raw and
digested high and low pH limed sludges were rated in April 1973. These
ratings are given in Figure 31. Rye generally showed a favorable
response to all sludge types and lime levels. Alfalfa, which requires
a neutral pH, grew much better in the soils treated with the highest pH
limed sludges. Alfalfa and rye responded favorably to entrenched
sludge, as shown in Figure 34.
154
-------
Table 44. NITRATE AND AMMONIUM NITROGEN WITH TIME AFTER SURFACE INCORPORATION OF LIMED AND UNLIMED
RAW AND DIGESTED SLUDGES IN SOIL
t_n
Ui
Sludge
type
Digested
Raw
Control
Digested
Raw
Initial
pH
6.4
8.5
10.0
11.7
6.5
11.2
11.8
5.3
6.4
8.5
10.0
11.7
6.5
11.2
11.8
NO -N, yg/g dry weight basis
Months after surface incorporation
0
7/18-22/72
37
-
24
62
_
44
3
-
353
300
364
483
635
340
176
1.5
9/1
50
138
28
80
62
155
144
41
314
43
22
15
300
19
17
3
10/10
168
246
53
57
116
95
77
38
110
5
3
3
19
3
3
4
11/20
17
13
9
10
10
7
7
9
NH4-N, v
11
3
3
3
3
3
3
6
1/31/73
3
3
7
4
3
3
2
3
8
3/30
11
7
3
4
2
3
5
4
9
4/26
3
3
2
3
2
3
3
3
10
5/30
4
6
4
15
5
4
4
110
12
7/18
29
17
29
23
16
1100
23
4
17
12/13
14
9
4
5
2
4
2
3
tg/g dry weight basis
8
3
4
6
3
3
4
8
3
3
2
2
2
2
12
3
2
3
2
6
3
5
3
2
3
3
3
3
52
4
4
5
4
152
4
10
1
1
2
1
2
1
Control
5.3
34
11
48
-------
v-j/f^y,. „
i;^!MB*2'te;v
Figure 34. Response of rye and alfalfa to entrenched sludge in May 1973.
156
-------
SECTION VI
GREENHOUSE STUDIES - TRENCH SIMULATION
INTRODUCTION
Greenhouse experiments were run before and concurrent with the field
studies on sludge utilization. The first of these experiments was run
to test the trenching technique for raw and digested sludge prior to the
field trenching studies. Simulated trenches of sludge were placed into
soil from the field site in large boxes in the greenhouse. Physical and
chemical changes of the entrenched sludge and surrounding soil were
studied during the growth of a corn crop. The factors studied included
gases, soil-sludge moisture, nitrogen, heavy metals, and biological
changes. A more detailed second greenhouse experiment was run in which
sludge pH was varied in addition to sludge type.
Knowledge of the gaseous state of the soil and sludge (aerobic - anae-
robic conditions) is helpful in describing nitrogen mineralization,
nitrification and denitrification. This in turn is useful in predicting
the potential of nitrogen movement through soils as a factor in ground-
water contamination. The gaseous phase of the soil and sludge exerts a
pronounced effect upon plant growth. Gases such as methane and ethylene
may be toxic to plants at relatively low levels. Extended periods of
low oxygen and high carbon dioxide restrict root growth, reduce yields,
and injure plants.
PROCEDURE
Profile Boxes
Sludge profile boxes were constructed. These boxes were 120 cm high,
60 cm wide, and 15 cm deep. The back, sides and bottom were of sheet
aluminum and the front was a removable panel of 1.25 cm thick plexi-
glass.
The boxes were placed upright on a greenhouse bench and filled with soil
and sludge. A schematic diagram illustrating the technique is shown in
Figure 35. The idea was to simulate a vertical section from midpoint of
a 60 cm (24 inch) wide trench to the midpoint of a 60 cm (24 inch)
interval between trenches. The box was high enough to provide 30 cm
(12 inches) of soil above and below the sludge.
The boxes were planted with corn. The growth of corn plants and the
behavior of corn roots in relation to the buried sludge were observed
throughout the experiment. Gas and moisture analyses of the soil atmos-
phere were conducted throughout the experiment. At the conclusion of
the study, the front faces of the boxes were removed and soil was sampled
157
-------
.^---—"—•-— Crop
30 cm
60 cm
30 cm
:—ir^L-^^^^-'^——•- Sludge
- New Soil
Surface
"Trench" Soil
— — — Surface Soil
—^- — — Subsoil
Screen
Gravel
I l< — — — Drain
60 cm
Figure 35. Diagram of trench simulation box.
158
-------
in a grid pattern. The soil was analyzed for pH, total nitrogen, nitrate-
nitrogen, ammonium-nitrogen, heavy metals, and salmonella, fecal coliform,
and total coliform bacteria.
Soil Moisture
Moisture samples were taken periodically with an auger and determined
gravimetrically.
Gas Analyses
Gas analyses were performed with an F&-M 5750 research gas chromatograph
equipped with a 0.25 cc sampling loop. Separation of carbon dioxide,
methane, oxygen, and nitrogen was obtained by two 6.4 mm OD aluminum
tubes packed with porapak Q and Linde molecular sieve 5°A respectively.
The two 6.4 mm OD tubes were separated by a 3.2 mm OD aluminum delaying
coil to gain separation of individual gaseous peaks. Known standard
gases were used for calibration to obtain quantitative results. Gas
samples from the trench simulation boxes were obtained by use of needle
equipped gas syringes through rubber septum ports spaced at intervals
over the backs of the boxes. The rubber septums were fitted into nylon
male connectors threaded into the backs of the aluminum boxes. Gas
samples were protected in the syringes from atmospheric contamination
during transport and storage by using serum caps or lock valves on the
syringe ends.
Nitrogen Analyses
Total nitrogen was determined by the Kjeldahl method. Nitrate- and
ammonium-nitrogen were extracted with a 4 to 1 solution of IN K.2S04 and
0. OSNA^^SO^) 3 to soil or sludge and determined by specific ion elec-
trodes and microdiffusion as described in Section IV.
Heavy Metals
Heavy metals were extracted from soils with 0.005M DTPA-TEA, 0.01M
CaCl2> and 0.1M TEA at pH 7.3 and total metals in plants were solubilized
by dry combustion and absorbed into HC1 (Section IV). Analysis was by
atomic absorption.
Bacteriological Analysis
Salmonella, fecal coliform, and total coliform bacteria were analyzed by
procedures described in Section IV utilizing the most probable number
(MPN) technique. The analyses were performed by the United States
Department of Agriculture or the England Laboratories, Inc., Beltsville,
Maryland.
Crop Growth
The growth of the corn plants and the behavior of corn roots in relation
to the buried sludge were observed during the experiment. After the
159
-------
corn plants matured, the boxes were taken down and the soil, roots and
sludge sampled on a grid pattern for chemical analyses.
Experiment 1
Digested sludge from the Blue Plains sewage plant was placed in one box
and raw alum-sludge stabilized with lime was placed in the other. Corn
was planted in each box and the plexiglass front covered with insulating
board to keep the soil dark. Drainage water was collected from each box
during a 5 month growth period and analyzed at intervals for nitrogen.
Tensiometers were installed through the aluminum back of the boxes to
measure water tension. The soil was a Galestown-Evesboro loamy sand
from our proposed field trenching site. Experiment 1 was initiated in
December 1971.
Six locations in the boxes were examined for gas composition. Two
locations were in the soil 6 cm from the sludge-soil interface at 48 and
75 cm in depth. Two other locations were 8 and 20 cm deep in the sludge
or 38 and 50 cm below the soil surface. The remaining locations were
2 cm below the sludge trench, 92 cm deep. One was 6 cm from the verti-
cal edge of the soil-sludge interface and the other was centered
directly below the sludge. Gas measurements were not made until 41 days
after placement of the sludge in boxes. From then on they were made at
weekly intervals up to the 138th day of the study.
Experiment 2
Experiment 2 was initiated in September 1972 approximately 4 months
after the large field trenching study was initiated and 3 months after
the field sludge pH studies were begun. Five trench simulation boxes
were used. Each of the five simulated trench treatments were in
Galestown-Evesboro loamy sand- They were: (a) control, (b) digested
sludge medium pH (9.8) from Blue Plains, D.C., (c) digested sludge low
pH (5.3) from Blue Plains, D.C., (d) raw sludge high pH (11.2) from
Fairfax, Virginia (Little Hunting Creek), (e) raw sludge low pH (6.9)
from Fairfax, Virginia (Little Hunting Creek).
RESULTS AND DISCUSSION - EXPERIMENT 1
Digested Sludge
Soil and Sludge Moisture — The digested sludge subsided 7 to 10 cm
during the 5 month period of the experiment. This subsidence was prob-
ably due mostly to packing of the sludge and squeezing out of air
pockets and only slightly to direct water loss to the soil. The tensio-
meters showed that there was a very pronounced hydrostatic head (posi-
tive pressure) of water within the sludge. This was as high as 135 cm
of water 2 days after sludge was placed in the trench and covered.
Thereafter, the positive head varied during wetting and drying cycles as
the corn crop, was irrigated. Even after the corn rsao-tg had penetrated
aad extra
-------
unexplored by roots maintained a slight positive hydrostatic pressure.
This behavior of the sludge was in sharp contrast to the surrounding
soil that was under moisture tension most of the time. This positive
head indicated that water would likely not enter nor percolate through
nonrooted entrenched digested sludge in the field for a considerable
period of time.
Plant Growth — The corn roots rapidly penetrated to the sludge layer
and then were inhibited for about 2 or 3 weeks. After that time, they
began to grow into the sludge, producing a very heavy mass of roats.
These roots spread through the sludge, dewatering it and causing it to
shrink and crack into small aggregates. By the time the corn matured,
the roots had spread and dewatered all but about the bottom third of the
trenched sludge (Figure 36>- When the box was laid horizontally and the
plexiglass removed at the end of the experiment, it was possible to lift
out the sludge-root mass as a dry spongy, peat-like block (Figure 3?X«
After the sludge had been broken up and dewatered by the corn roots, it
reabsorbed water readily but did not reswell. It now had become very
permeable to water and air. The non-rooted sludge remained a barrier to
water flow.
During the irrigation of the corn, sufficient water was added to produce
drainage from the bottom of the box. The drain water from this digested
sludge box was clear and almost odorless. This was in sharp contrast to
the drain water from the alum-lime sludge which was reddish-brown in
color and malodorous. This is described in more detail below.
Corn growth was excellent. The plants reached 180 cm in height and
produced normal ears. There was no evident difference in growth between
plants on top of the trench and those to the side. Chemical analyses of
the plant material are being made.
Gas Analyses — Gas composition data gathered at the representative
sampling locations (in and just below the trenched sludge) are given in
Figures 38 and 39. Figure 38 shows that the methane (CH4) concentration
in the digested sludge was very high from 41 to 75 days after sludge
incroporation. During that same early period oxygen (C^) concentrations
were below 5% and carbon dioxide (CC>2) concentrations were above 17%.
Obviously, therefore, anaerobic conditions prevailed during that period.
As roots penetrated the sludge in the region of the gas sampling port,
CH^ concentrations dropped precipitously, C02 concentrations also
decreased, and oxygen concentrations increased. Roots were able to
penetrate the sludge slowly in spite of high CH4 and C02 and low 02
Apparently penetration was initiated by the roots growing close to the
sludge, dewatering a small area and causing it to become aerobic. Roots
then grew into the newly aerobic area in the sludge, dewatering a new
adjacent area, and so on.
161
-------
•&
' ** 1**3liir
Jfl?
Figure 36. Penetration of corn roots into a simulated trench of digested
sludge - 5 months after planting. The original
cross-section of sludge addition is marked.
162
-------
Figure 37. Appearance of digested sludge in simulated trench after
penetration and dewatering by corn roots during a
5-month growth period.
163
-------
PERCENT OF TOTAL SOIL GAS
K>0-
80
60
40
20
COC
~ A-A A-A
40 80 120
DAYS AFTER SLUDGE INCORPORATION
160
Figure 38. Methane, carbon dioxide, and oxygen levels within
the simulated trench of digested sludge.
164
-------
The data on soil gases below the sludge are shown in Figure 39. From 1%
to 4% CH^ was found in the soil during the period of 41 to 75 days after
sludge incorporation. Oxygen levels were essentially below 6 percent
throughout the experiment, while C02 levels were above 12 percent. This
suggests that there were severe anaerobic conditions. After that period
the soil atmosphere became slightly more aerobic but probably not enough
to enhance root growth.
Nitrogen in Drainage Water
Data on the leachate are shown in Table 45. During the first 100 days,
anaerobic conditions prevailed as indicated by the presence of CH4
(Figure 39). During this period, nitrification was low as shown by low
levels of nitrate-nitrogen. As aeration improved, nitrification
increased and nitrate appeared in the leachate.
Although this suggests that nitrate pollution could become a problem
with time, at least part of the nitrate content in the leachate may have
been an artifact of the experimental technique. The sludge was observed
to pull away from the plexiglass cover of the box and some water move-
ment may have occurred at the soil-box cover interface, bypassing the
more anaerobic zone directly below the sludge filled trench.
Zinc in Plants — As plant roots explored the trench sludge area, the
plants accumulated zinc. Table 46 shows concentrations of zinc in
plants growing on profile box 1 where plant No. 1 is the plant furthest
from the sludge and plant No. 11 is completely above the sludge area. An
increased level of zinc occurred in the plants that were more nearly
over the sludge than those which were further away.
Alum-Lime Sludge
The alum-lime (raw) sludge in the trench simulation trials behaved quite
differently than did the digested sludge. The raw sludge was drier and
more difficult to pack in the trench. It subsided more during the first
week or so than did the digested sludge. Within a few days after assem-
bling a very heavy growth of fungus mold appeared around the upper edge
of entrenched sludge. Over the succeeding weeks it gradually spread
downward as the sludge dewatered and shrank away from the observation
window.
Plant Growth — During the first 2 months the corn roots were unable to
penetrate the alum-lime sludge. The roots grew down to the top of the
sludge layer and stopped ( Figure 40). A heavy massing of roots occur-
red at this location, all pointing down but not elongating. More and
more roots accumulated here until they were tightly massed. In the
meantime, the sludge had settled leaving a 1 to 3 cm air gap between
roots and sludge. The roots did not pass this air gap, suggesting that
a volatile inhibitor was involved. In spite of the root inhibition,
almost normal top growth of corn occurred. After 3 mo-mths th>®
to jp'eBetrate 3 few cm into this Siurf^ee of the s.l
165
-------
PERCENT OF TOTAL SOIL GAS
20
16
12
8
0
CO,
0
40 80 120
DAYS AFTER SLUDGE INCORPORATION
160
Figure 39. Methane, carbon dioxide, and oxygen levels in
soil 2 cm below the simulated trench
of digested sludge.
166
-------
Table 45. NITROGEN COMPOUNDS IN DRAINAGE WATER FROM A TRENCH
SIMULATION BOX CONTAINING DIGESTED SLUDGE*
Time after
addition,
days
93
101
117
124
137
Nitrogen analyses, mg/1
NH -N
4
26
68
97
93
88
NO -N
0
2
25
30
45
Org. N
10
4
6
116
3
Total N
36
74
128
239
137
* Leachate from the trench drained through 30 cm of loamy sand
under the trench.
Table 46. ZINC CONTENT OF WHOLE CORN PLANTS
GROWING IN A TRENCH SIMULATION BOX
CONTAINING DIGESTED SLUDGE
ft Zinc content
Plant n0" yg/g dry weight
1
2
3
4
5
6
7
8
9
10
11
152
158
129
194
129
158
230
212
271
249
242
* Plant number 1 was furthest from sludge;
plants number 7-11 were over sludge.
167
-------
00
Figure 40. Corn root behavior in contact with "trench" of alum-lime sludge - 42 days after planting.
Root growth has been arrested at the soil-sludge boundary.
Note fungus mold growth on the sludge surface.
-------
Figure 41. Corn root behavior in contact with "trench" of alum-lime
sludge - 3 months after planting. Corn roots are just
beginning to penetrate sludge, well back of the advancing
front of heavy mold growth. This crop of corn matured
without any further penetration of the roots.
169
-------
By this time the plants were nearing maturity and root penetration
ceased. The previously described fungus mold continued to grow as a
zone of mycelium progressing downward slowly between the sludge and the
observation glass. Behind the advancing edge of the mold the sludge was
shrunken and dewatered. It appeared as though decomposition was aiding
the dewatering process.
The raw alum-sludge seemed to allow water to pass through it and leach
it, in contrast to the digested sludge which appeared relatively imper-
vious in the wet state. The movement of water through the sludge
occurred because of the shrinking and cracking of the sludges. The
drainage water was reddish-brown, turbid, and foul smelling.
Corn growth was not as good on the alum-lime sludge as on the digested
sludge. The plants were somewhat chlorotic and showed marginal burning
of the lower leaves. The analysis of the plant tissue may offer some
explanation of these symptoms.
Gas Analyses — Gas composition data was gathered in the raw sludge
trench simulation box at approximately the same two representative
locations as in the digested sludge trench simulation box (Figures 42
and 43). Methane was present in the raw sludge (Figure 42) through all
but the initial two weeks of the study. Carbon dioxide concentrations
were also high (above 16%) throughout the study period. Oxygen con-
centrations were low, averaging about 4%, all emphasizing that anaerobic
conditions prevailed throughout the experiment. In contrast with the
high levels of CH^ occurring early in the digested sludge, CH^ levels in
the raw sludge were low initially and high concentrations were not found
until after about 70 days.
The effect of sludge on gaseous production in the soil atmosphere is
shown in Figure 43. Methane was detected after 11 days and had
increased to over 11% at the 126th sampling date. Carbon dioxide con-
centrations progressed to a maximum of 23% and at the 126 day sampling
date were below 11%. Concurrently, the 62 concentrations were low
throughout the study ranging from 2% to 6%. This anaerobic condition
can restrict root growth and affect plant development. These reduced
conditions also restrict nitrogen mineralization and encourage denitri-
fication. Consequently, one would expect little nitrate leaching until
the soil atmosphere became aerobic.
Nitrogen in Drainage Water — The nitrogen content of the drainage water
was very high, especially in ammonium (Table 47). Evidently the very
small exchange capacity of the loamy soil was quickly saturated, allow-
ing ammonium to move through the profile. The highly anaerobic and
richly organic conditions present were apparently unfavorable for the
conversion of ammonium to nitrate, and/or considerable denitrification
was occurring. These high concentrations of ammonium both within the
sludge and in the soil are very toxic to root growth. The high con-
centrations of ammonium and other materials fouling the drainage water
suggested that the capturing, impounding, and recycling of infiltrating
rain water are particularly important in areas entrenched with raw sludge
170
-------
PERCENT OF TOTAL SOIL GAS
40
32
24
16
8
0 -
40 80 120
DAYS AFTER SLUDGE INCORPORATION
160
Figure 42. Methane, carbon dioxide, and oxygen levels
within the simulated trench of raw
alum-limed sludge.
171
-------
PERCENT OF TOTAL SOU GAS
20
16
12
8
40 80 120
DAYS AFTER SLUDGE INCORPORATION
160
Figure 43. Methane, carbon dioxide, and oxygen levels in
soil 6 cm below the simulated trench of raw
alum-limed sludge.
172
-------
Table 47. NITROGEN COMPOUNDS IN DRAINAGE WATER FROM
A TRENCH SIMULATION BOX CONTAINING ALUM-
LIME SLUDGE*
Time after sludge Nitrogen analyses, mg/1
addition,
days NH4-N N03~N Org. N Total N
19
21
28
34
41
24
81
825
1404
1461
1
6
33
8
6
14
24
8
132
87
38
90
866
1544
1554
* Leachate from the trench drained through 30 cm of loamy sand
under the trench.
CONCLUSIONS - EXPERIMENT 1
Results obtained from the digested sludge trench simulation box in
Experiment 1 showed (1) that considerable penetration of the sludge
occurs by corn roots of healthy corn plants growing over the entrenched
sludge, (2) that little percolation of water through the sludge occurs
until after root penetration, and (3) that, while low oxygen concentra-
tions and movement of organic materials along with nitrate-nitrogen
would be favorable for denitrification, some movement of nitrate down
through the soil profile is likely to occur.
Results from the raw alum sludge trench simulation box showed (1) that
considerable delay of corn root penetration into the sludge and even
into the soil immediately adjacent to the sludge and reduced vigor of
corn occur. (The reason for poor root growth may have been due in part
to high ammonium and low oxygen); (2) that water percolation occurs and
is caused by considerable shrinkage and cracking not evident in the
digested sludge; (3) that, as a result of appreciable movement of organics
and low oxygen, considerable denitrification of nitrate-nitrogen is
likely to occur under the trenches; and (4) that appreciable movement of
ammonium-nitrogen is also likely to occur.
173
-------
The results of the trench simulation box studies enabled us to predict
in a rather short period of time what might happen in our field studies
and thereby helped us plan the tests needed when we excavated trench
cross sections in the field.
RESULTS AND DISCUSSION - EXPERIMENT 2
Introduction
A second series of trench simulation boxes was planned to investigate,
under more controlled conditions than were possible in the field pH
studies, the effect of sludge type and initial pH on soil-moisture,
nitrogen transformation and movement, the gaseous atmosphere of the soil
and sludge, soil and sludge pH, plant growth, pathogen persistence and
movement, and heavy metal movement.
Soil Moisture
Soil moisture data are shown in Table 48. An attempt was made to keep
the soil moisture in the five boxes at approximately the same level.
During most of the experiments the moisture contents were similar for
the five treatments. The Evesboro sandy loam is a droughty soil. The
0.1 bar value, which probably is close to field capacity, is only 6.3%
and the 15 bar value (wilting point) is 1.2%. Until November 11 the
soil was kept moist to facilitate corn growth. After that date corn
development was rapid and transpiration was sufficiently great so that
soil moisture was considerably lower. In the root zone (40 cm down from
the top of the box) soil moisture remained between 0.1 bar and 15 bars
except for February 15. Below a depth of 40 cm soil moisture was
undoubtedly higher.
Soil and Sludge Nitrogen
The data for nitrogen in soil 161 days after sludge placement are
presented in Figures 44, 45, and 46. Total nitrogen in the control box
averaged 350 ppm (Figure 44). In both the digested sludge treatments,
total nitrogen levels were higher in the soil adjacent to and below the
sludge than elsewhere in the soil. In the raw treatment, total nitrogen
was more than twice the control in the zone below and to the right of
the sludge. This increase in total nitrogen indicated the movement of
organic material from the sludge.
The ammonium data are given in Figure 45. In all treatments ammonium
was considerably higher than the control. The greatest concentration of
ammonium was found in the raw sludge treatments below and to the right
of the sludge. It appears that in the digested treatments the organic
nitrogen in the sludge ammonified and oxidized. Dewatering of the
sludge by the corn roots produced favorable aerobic conditions for
nitrification. In contrast in the raw sludge, which did not dewater,
conditions were anaerobic and favored accumulation of ammonium and
denitrification whenever nitrate was produced.
174
-------
Table 48. SOIL MOISTURE PERCENT IN TRENCH SIMULATION BOXES
AT 10 AND 40 cm
10 cm
Box
Date
Control
9/27/72
10/5
10/13
10/25
10/31
11/10
11/21
11/28
12/8
12/23
1/5/73
1/11
1/19
1/26
2/2
2/15
2/23
10
9
6
9
10
17
1
10
1
1
6
2
1
1
1
1
4
High
10
8
5
10
10
13
2
11
2
6
3
6
4
2
1
1
2
Digested
pH Low pH
10
9
14
7
12
14
<1
11
2
4
4
1
7
1
1
1
2
Raw
High pH
10
9
16
9
11
14
<1
9
1
2
6
1
1
1
1
1
1
Low pH
11
6
5
8
12
14
3
9 -
1
2
6
1
1
1
1
1
2
40 cm
Date
10/25/72
10/31
11/10
11/21
11/28
12/8
12/23
1/5/73
1/11
1/19
1/26
2/2
2/15
2/23
Control
10
15
15
5
14
5
2
6
4
7
3
2
1
9
High
9
13
16
2
15
6
6
7
5
5
3
3
1
2
Digested
pH Low pH
11
15
17
2
16
6
5
8
4
5
4
2
2
4
Box
High pH
9
12
15
5
9
5
5
7
4
4
6
2
1
3
Raw
Low pH
9
13
10
2
9
3
4
8
4
4
7
4
1
3
175
-------
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3** 357 338
355 354 3<-l
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CONTROL DIGESTED DIGESTED RAW RAW
HIGH pH LOW pH HIGH pH LOW pH
Figure 44. Total nitrogen (ppm) in trench simulation boxes after 161 days.
-------
2 2. 2
2 2 I
^ ^ 2
2. 2 2
223
CONTROL
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HIGH pH
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RAW
HIGH pH
5
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LOWpH
Figure 45. Ammonium-nitrogen (ppm) in trench simulation boxes after 161 days.
-------
333
3 3 a
432
f 3 3
845
CONTROL
£ 5 1
3/2-
95
47 24
67 /?
7 .5* //
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DIGESTED
HIGH pH
8
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DIGESTED
LOW pH
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Figure 46. Nitrate-nitrogen (ppm) in trench simulation boxes after 161 days.
-------
Nitrate-nitrogen (Figure 46) was higher in the digested treatments both
in a horizontal and vertical direction from the sludge. The digested
high pH treatment had the greatest movement of nitrates. At 20 cm below
the sludge, nitrate values ranged from 17 to 33 ppm. The aerobic con-
ditions prevailing in the digested treatment encourage mineralization of
organic nitrogen to nitrates. Unless the nitrates are removed by roots
or denitrified, they will be leached to the groundwater. In contrast,
the digested low pH sludge nitrate values for the same position were 4
to 10 ppm. Very little nitrate was found in the raw sludge treatments.
This was probably the result of anaerobic conditions inhibiting nitrifi-
cation or possibly encouraging denitrification.
The pH data are given in Figure 47. The pH of the soil above the sludge
in all treatments including the control is higher because the soil was
limed at the time of planting. All sludge pH's were 8.1 or less, even
though one was over 11 initially. The Ca(OH)2 had converted to CaCC>3.
The pH of the limed sludges on the average was higher than the pH of the
unlimed sludges. The soil pH to the side and below both digested sludge
treatments was low because of the presence of acidic nitrate. In con-
trast, the soil pH to the side and below the raw sludge treatments was
high as a result of ammonification.
Gas Analyses
To illustrate the changes in the soil atmosphere as a result of sludge
addition, a single location in the profile box was selected. The gas
analyses data in the accompanying figures are from a location in the
soil 98 cm from the surface and 8 cm under the trenched sludge.
Control — Normal percentages of soil gases were found throughout the
experiment. Oxygen was 20%, C02 was 1 percent, and there was no CH^.
Digested High pH — The data for CH4, 02, and C02 are shown in Figure
48A. At the locations sampled little CH^ was found throughout the
experiment. Oxygen concentrations remained generally high and there
were no extensive periods of low oxygen levels. Carbon dioxide con-
centrations were, conversely, low. Carbon dioxide increased with depth
asi,oxygen decreased. In general, the soil environment for the treatment
appeared to be favorable for root growth.
Digested Low pH — No CIfy was found after 35 days (Figure 48B). Oxygen
concentrations were lower than in the previous treatment and remained
below 15% throughout the experiment. The low 02 and high C02 could
partially restrict root growth in this area. Carbon dioxide increased
with depth in the soil and at one location reached a maximum of 21%
(data not given).
Raw High pH — This treatment showed severe reducing conditions (Figure
48C). Methane concentration increased after 60 days to a maximum of 14%
on the 132nd day. Oxygen concentrations dropped to less than 4% in
30 days and remained below this concentration throughout the experiment.
There was a continual increase in COo concentrations. These conditions
179
-------
OO
o
77 7.k 7.1
5.0 5.1 5.1
5.1 S.I *
-------
PERCENT OF TOTAL SOIL GAS
20
8
V
°2
CH,
'~"-^I-\'T—'•"7'.\ "^"i— ~t T"T_ r* ""••"" TLI\
0 120 I6C
40 80
DAYS AFTER SLUDGE INCORPORATION
Figure 48.
(A) Digested high pH sludge.
Methane, carbon dioxide, and oxygen levels in soil
centered 8 cm below the simulated trench.
181
-------
PERCENT OF TOTAL SOIL GAS
20
12
8
_A/\ A A A I A
.A.
./v
GO-
'TGC
40 O 120
DAYS AFTER SLUDGE INCORPORATION
(B) Digested low pH sludge.
Figure 48 (continued). Methane, carbon dioxide, and oxygen levels in
soil centered 8 cm below the simulated trench
182
-------
PERCENT OF TOTAL SOIL GAS
8 -
4 -
40 80 120
DAYS AFTER SLUDGE INCORPORATION
160
(C) Raw high pH sludge.
Figure 48 (continued). Methane, carbon dioxide, and oxygen levels in
soil centered 8 cm below the simulated trench
183
-------
PERCENT OF TOTAL SOIL GAS
CH4
.--A
40 80 120
DAYS AFTER SLUDGE INCORPORATION
160
Figure 48 (continued).
(D) Raw low pH sludge.
Methane, carbon dioxide, and oxygen levels in
soil centered 8 cm below the simulated trench.
184
-------
Table 49. HEIGHT AND STEM DIAMETER OF CORN PLANTS GROWING
IN TRENCH SIMULATION BOXES AFTER 87 DAYS
Treatment
Control
Digested high pH
Digested low pH
Raw high pH
Raw low pH
Plant
height , cm
85
74
73
66
69
Stem
diameter, mm
87
81
96
88
91
restrict root growth and plant development. The anaerobic conditions,
indicated by the data, also inhibited nitrification and enhanced denitri-
fication if nitrate were formed. This was supported by the nitrate data
as shown in Figure 46.
Raw Low pH — This treatment behaved in a similar fashion to that
depicted in the previous raw treatment (Figure 48D). After 67 days CH,
increased and remained high (over 20%) for the remainder of the study.
Oxygen levels decreased at that time dropping to a minimum of 2% on the
104th day. Conversely, carbon dioxide increased during the same period.
These conditions indicated anaerobiosis which reduces root penetration
and plant growth. As in the previous treatment, these conditions inhi-
bit nitrification and enhance denitrification.
Plant Growth
There was some difficulty in obtaining good growth of corn in the trench
simulation boxes. Apparently fertility levels were not high enough in
the top 30 cm of soil of each box. Nonetheless, plant responses to the
control and different sludge treatments should be comparable. The data
on plant height and stem diameter (87 days growth) are shown in Table 49.
Plants growing in the control were tallest. Plants growing in the
digested sludge treatments were next in height, and plants growing in
the raw sludge treatments were shortest. The lime additions did not
influence the height attained by the plants. There also were no signifi-
cant effects of sludge or lime treatment on stem diameter.
Roots of corn plants growing in the control were fine textured and they
extended throughout the soil (Figure 49). Roots in the digested treatments
185
-------
>• . ,'. .
00
CONTROL
DIGESTED
HIGH pH
DIGESTED
LOW pH
RAW HIGH pH
RAW LOW pH
Figure 49. Photographs of root distribution in trench simulation boxes after 98 days.
-------
ultimately penetrated about 45 cm into the digested sludge and extended
throughout the soil beside the sludge (Figure 49). Roots seemed to be a
little larger in the soil beside the sludge than in the soil further
away and also larger than in the control because of responses to nutri-
ents from the sludge. Corn root distribution was apparently more uniform
in the high than in the low lime-treated digested sludge. The sludge
was dewatered and lighter in color where roots had penetrated.
There was little root penetration into raw sludge even after over
3 months (Figure 49), and most of the raw sludge changed very little in
appearance. Characteristically, however, a white fungal growth started
at the interface between the soil and both raw sludges and moved with
time into the sludges. After passage of this white fungal front, roots
were able to penetrate short distances into the sludge where dewatering
and change in appearance of the sludge occurred.
Roots did not grow into the soil beside the trenched raw sludge, prob-
ably because of rather high concentrations of toxic materials like
ammonium (Figure 46) and methane and because of low concentrations of
oxygen (Figures 48C and D). Root growth seemed more advanced in the
high than low lime treated raw sludge and in the soil beside the sludge.
The lime apparently altered somewhat the toxic effects of materials like
ammonium and methane (Figures 46, 48C, and 48D).
Thirty-three different fungi were isolated from the sludge boxes. Four
fungi are believed to be responsible for the formation of the fungal
mantel between the sludge and corn roots. These are Trichoderma
kining: Oud., T. lignorum (Tode) Harz., Gymnoascus sp., and Cunninglamella
elegans Lindner.
Salmonella, Total Coliform,,and Fecal Coliform Bacteria
Before incorporation in the trench boxes, the sludges were analyzed for
salmonella, total coliform and fecal coliform bacteria. The low pH
digested and raw sludges contained many fold higher numbers of fecal and
total coliform bacteria than did the high pH digested and raw sludges.
No salmonellae were found in the high pH sludges, but they were present
in both the low pH sludges (Table 50).
Results of the bacterial analyses of the trench box profiles at the end
of the study are shown in Figures 50 and 51. All samples were analyzed
for total and fecal coliforms. Only samples taken from the sludge
trenches and soil directly above and below the sludge trenches were
analyzed for salmonellae. No salmonellae were found. The total and
fecal coliform numbers relative to their initial numbers were drasti-
cally reduced in the low pH digested and raw sludges. At the beginning,
the high pH raw and digested sludge contained only a few total coli-
forms. The numbers at the end were not significantly changed. Although
the fecal coliforms were below the detectable limit at the beginning for
both the high pH raw and digested sludges, they continued to multiply
187
-------
Table 50. MOST PROBABLE NUMBER (MPN) OF SALMONELLA, TOTAL COLIFORM
AND FECAL COLIFORM BACTERIA IN SLUDGES USED FOR GREENHOUSE
TRENCH SIMULATION BOX STUDIES
Sludge type
Replicate determinations, MPN/g dry weight
Salmonellae Total coliforms
Fecal coliforms
Digested high pH
Digested low pH
46
5
160
1.8x10*
3.1x10
3.1x10;
<1.2xl(f
Raw high pH
Raw low pH
<15
<16
2600
6100
56
3
8
8.9xlOp
Q
3.5x10
<1
<1
7
6.1xlO?
7.3x10
and were detected in the high pH raw sludge after 161 days at harvest.
These results indicate their survival ability despite the high rate of
lime application.
More total and fecal coliform bacteria were found in the soil external
to the raw high and low pH sludge trenches than in the soil external to
the two digested sludge trenches. The greatest numbers were found in
the soil external to the high pH raw sludge trench despite the fact that
this sludge contained the lowest numbers at the initiation of the study.
Coliforms were present in samples taken above the trenches of all the
sludge treatments (Figure 50 and 51). They may have moved upward by
capillary action and then grown on organic material present in the
surface soil.
Downward and lateral movement and subsequent survival of total and fecal
coliforms were apparent only in the raw-sludge trench simulation boxes.
This occurred possibly because more substrate, as indicated by the total
nitrogen concentrations in these areas (Figure 44), moved out from the
raw sludges than was available for movement from the digested sludge.
Using coliforms as indicators, it seems apparent that survival of
pathogens can occur in the sludge and in the soil adjacent to the sludge
trenches for a period of at least 5 months (the duration of this study).
Coliform organisms have the ability to reproduce outside their hosts as
do apparently the shigellae and the salmonellae. Coliforms are reason-
able indicators for organisms of this type. Many pathogens, however,
188
-------
00
^
.? . .
"? . .
CONTROL
". *
•»
&
'3
<3 8
3 <3
- « «
DIGESTED
HIGH pH
22
«r
»
x5 <
• *
f5 i3
3 £.3
- ^ <*
DIGESTED
LOW pH
220 4
IS
«.
MX> 4
iS m°
4 41 170
^3 4 ^7
RAW
HIGH pH
38 '
•?
9S
*1
;i 25-
-3 85"
I3 ^ "*
RAW
LOWpH
Figure 50. The MPN/g dry weight of total coliform bacteria in trench simulation boxes
after 161 days.
-------
^
? . .
- . .
CONTROL
- -
-•
-?
« -.'
? -
• • *
<5
( #
• *
I3 4 f5
RAW
HIGH pH
-
-
*
e -3
f3 t5
8 -^3
<5 -=3 "3
* » »
<3 <5 <3
RAW
LOWpH
Figure 51. The MPN/g dry weight of fecal coliform bacteria in trench simulation boxes
after 161 days.
-------
cannot reproduce outside their human hosts, and determining survival of
coliforms as an indicator of their survival is an extremely conservative
procedure.
Heavy Metals
Zinc and copper distribution in the trench simulation boxes after
161 days at harvest is shown in Figures 52 and 53. It is clear from the
data that neither zinc nor copper moved to any appreciable extent from
the sludge section of the boxes into the soils. The large differences
of over 500 ppm zinc vs. less than 1 ppm zinc in contiguous samples is
very positive demonstration that DTPA-TEA chelate extractable metals did
not move. The question then remains, "Why did the metals fail to move
from the trench area of the profile?" At least two possibilities
exist: (1) lack of water movement through the sludge zones which might
have caused a movement of soluble metal or a mass flow of organics that
held chelated metals and (2) retention of metals in the sludge area,
even if leaching occurred, because of strong chemical binding by the
unsaturated cation exchange/chelation capacity of the sludge organic
matter under the neutral to alkaline conditions (Figure 47).
We believe that there was some movement of organic materials from the
sludge out into the surrounding soil. If gross movement of organic
matter occurred, these metals bound to the organic matter should also
have moved. If movement occurred, a gradient in metal concentration
should then be present. This was not observed. Apparently the near
neutral to alkaline conditions prevented the movement of metals with the
organic materials.
In other published experiments involving additions of heavy metal salts
to soils, usually little or no leaching of metals is reported. Where
leaching is reported, a gradient in metal concentration had always been
observed in the short-term. When both sludge and heavy metals are
present as in our studies, the tests suggest that metal leaching does
not occur unless there is a gross movement of organic metal-binding
chelates because of (1) the high capacity of the sludge to hold metals
against leaching many times in excess of the metals contained in the
sludge, and (2) the soil and sludge were not sufficiently acid to cause
metal release from the chelation sites and negatively charged surfaces
in the sludge. In the trench simulation studies the sludges did not
become acidic even after 161 days (Figure 47).
As organic sludges decompose, metals should be released from chelatio~t
sites, and some exchange sites will be destroyed. Movement and u, '- •
of these metals by plants might be enhanced, particularly if the soil is
acidic. While the soil was acidic the sludges were not and r le metals
apparently remain bound in the sludge. The metals also may Lave become
bound to inorganic exchange sites in the soil or chemically precipitated
as carbonates and phosphates, reducing their ability to move and be
absorbed by plant roots.
191
-------
I.O 0.1 i.fc
l.i i.l l.t
i.l i.o i.i
1.1 1.1 /.I
I.O 0.9 O.8
CONTROL
0.1 /.I 2.I
41?
SiS
0.7 /.o
0.4 0.1 l.l
0-7 O.t /-O
DIGESTED
HIGH pH
'.'
720
r
O.fc
/./ 2.4
0-8 I.S
f.i >*>
/.o 0.8 /•£
DIGESTED
LOW pH
a /.z 2.0
385
570
/.o
1.5 21
i.o o.i.
/•o 0.9 o.e
RAW
HIGH pH
1
'•0 I.O 0.1
686
740
,o c
, ,,
/./ i.i
& 0.6
Q.1 0.7 0.7
RAW
LOWpH
Figure 52. Zinc distribution (DTPA-TEA extractable,ytXg Zn/g dry soil or sludge) in trench simulation
boxes after 161 days.
-------
OJ
A-f 11 21
/•+ /•+ 1.7
14- /•? I-4-
/# A* A*
CONTROL
0.8 o
220
210
.6 /./
0.8 3.f
/.o /.o
0.8 no A*
/.O I.Q t-O
DIGESTED
HIGH pH
0.7
300
305-
/* i.i
LI /••*
/.o 0.8
AO 0.7 /-O
/•o /.o 0-8
DIGESTED
LOW pH
O.8 AT O.i
• * «
250
*p
7;7 ^
Of, O.&
f 1-4
// ,, /,
RAW
HIGH pH
O.8 1.4 1,0
205
265
':' '
I.i 0.8
/.z 1-4
/•* /.f /.+
RAW
LOWpH
Figure 53. Copper distribution (DTPA-TEA extractable, ug Cu/g dry soil or sludge) in trench simulation
boxes after 161 days.
-------
CONCLUSIONS - EXPERIMENT 2
As in Experiment 1, the presence of nitrate under digested sludge and
ammonium under raw sludge indicated that measures would probably be
needed in the field to provide for capture, retention, and recycling of
infiltrating rain water. There was less nitrification and/or greater
denitrification associated with the more anaerobic conditions under and
within raw than digested entrenched sludge. Hence, there will probably
be less initial danger of movement of nitrate from raw than from
digested sludge.
Liming sludges to a high initial pH may ultimately insure that the
sludge and perhaps the soil pH is buffered against a pH decrease caused
by acidity produced by nitrification and possibly other microbial activ-
ity. Liming the sludges did not increase nitrate production as might
have been expected.
Liming sludges to a high initial pH reduces pathogens to low levels, but
does not prevent multiplication of the few surviving microorganisms like
fecal coliform and salmonella which have the ability to reproduce out-
side their human host. There was little movement of total coliform
bacteria and even less movement of fecal coliform bacteria. Movement
that did occur was not related to sludge lime level.
Since movement of heavy metals did not occur from either limed or unlimed
sludge, additional long-term research is needed with more soil types
under more widely ranging conditions to determine if liming is helpful
in preventing metal movement. Additional research is also needed to
determine if liming entrenched sludge will reduce uptake of metals by
plants. Adequate determination could not be made in the rather poor
crop growth in Experiment 2,
More research will be needed to determine if liming entrenched sludge is
really necessary. It does no harm, and reason and theory suggests that
it should be beneficial in reducing metal movement in soil and uptake by
plants. Therefore, liming sludges prior to entrenchment will probably
be important and beneficial in maintaining an equilibrium pH in sludge
of 6.5 or greater.
194
-------
SECTION VII
VIRUS TRANSPORT THROUGH SOIL
INTRODUCTION
The nature of the interaction of viruses and soil is poorly understood.
Viruses are amphoteric and are negatively charged within the pH range of
most soils. Since the ion exchange complex is predominately negatively
charged, viruses like anions of salts might be expected to readily move
with a water front through most soils. Studies, however, have shown
that viruses are sorbed by soils. The mechanism of sorption has not
been determined, however, and the present state of knowledge does not
allow the prediction of how far viruses may move with water in any
particular soil. The objective of this study was to determine the
potential for movement of viruses through a sandy soil leached with
water. This study provided a model for evaluating the possible movement
of sludge applied viruses into groundwater at trenching sites.
PROCEDURES
Three soil column studies were run to determine the potential for virus
movement in the Galestown-Evesboro soil obtained from the trenching
site. The bacteriophage of the plant pathogen Xanthomonas pruni and
attenuated poliovirus type 1, Brunite strain were tagged with radio-
active phosphorus to facilitate their monitoring through these soil
columns leached with water. The viruses were tagged by introduction of
P-32 labeled phosphate into their hosts as substrate during culture
previous to infection with the viruses.
Compared to the spherical polio virus' diameter of approximately
230 A, the bacteriophage is relatively large having a hexagonal shaped
head 600°A from side to side and overall length of 1,580° A including
the head, neck, and 6 tail spikes. During radioactivity assay, plaque
forming tests were always carried out to ensure accurate virus:radio-
activity ratios. A_ssay by radioactivity is less sensitive than by
bioassay (plaque counting) but P-32 use seemed to be justifiable because
of the ease of measurement made possible.
The soil used in this study was sterilized by 3 to 4 megarads of gamma
radiation from a Co-60 source to minimize destruction of the viruses by
microbial decomposition. The pore volume of water in the columns was
determined by measuring the gain in weight of the columns under the flow
conditions in the experiments. In all column studies distilled water
was applied at the rate of moderate rainfall, 1 cm/hour.
For the first study, 4.0 x 10 plaque forming units (pfu) of X. pruni
bacteriophage were applied to the top of an air-dry soil column 8.5 cm
195
-------
in length before leaching. In the second study, poliovirus was intro-
duced in solution to the top of an air-dry column of soil 150 cm long
before leaching. In the final study, soil columns each 8.5 cm long were
leached with water, then each column was leached with a different con-
centration of poliovirus as suspended in 0.08 ionic strength Dulbecco's
buffer. The virus concentrations were 4.0 x 105 and 4.0 x 10° pfu/ml.
RESULTS
When the bacteriophage was applied to the top of an 8.6 cm long column
of soil and leached at a rate of 1 cm/hour, about 76% of the virus was
removed from the column in the first 30 ml (1.43 pore volumes) of
leachate (Figure 54). Of the 24% sorbed, the highest concentration
occurred in the first 5 mm of column depth (Figure 55). The amount of
rainfall (R) needed to move this virus peak any depth can be estimated
by use of the two following equations (Swoboda and Thomas 1968, J.
Agri., Food & Chem., 16 pp, 923-927):
/ Vp _ \ Vv
1) k =( — -LJ TT~
\Vv / W
Where: k = distribution coefficient
Vp = effluent volume to leach one-half of the virus from
the column
Vv = water filled pore volume of column
W = weight of the soil in column
2) R = L (kp + ^
Where: L = depth virus will be moved
p = bulk density of the soil
V = total volume of the soil filled portion of column
The Vp in the first equation is determined by use of a wet column rather
than an air-dry one as was the case in this experiment. Assuming peak
symmetry, which admittedly can be erroneous, and accounting for the
displaced pore volume, Vp was estimated at 30 cm. The amount of rain-
fall calculated to move the virus 150 cm (5 feet) was 83 cm (33 inches).
To check the validity of the use of short columns as a model for longer
columns, a 150 cm long air-dry column was packed. At this time, radio-
actively tagged poliovirus became available. The virus (4 x 10' pfu)
was placed on top of the column. Upon leaching with distilled water
(1 cm/hr), a band of virus representing 1.3% of the amount applied was
eluted from the column after passage of 1.58 pore volumes of water
(1,010 ml). The pore volume divided by the inside cross-sectional area
of the column indicated that 60 cm (24 inches) of rain would be required
to elute the band peak of virus from the column as compared to the 83 cm
calculated by use of the small column data. Both the rainfall required
for elution and the fraction of virus eluted were smaller than pre-
dicted, indicating that a portion of the moving virus band was con-
tinually being sorbed and retained by the soil.
196
-------
H
U
U
4
3
LU 2
<
5 1
0
'o
x
CL
CJ
0 5O 100 3OO
VOLUME LEACHED (ML)
Figure 54. Elution of Xanthomonas pruni bacteriophage from Galestown-
Evesboro sandy loam soil. Rate of leaching was 1 cm/hour
and the column was 8.5 cm long.
197
-------
30
CD 24
O
X
18 •
LL 12
Q_
6
0
0 20 45 70
COLUMN DEPTH (MM)
90
Figure 55. Distribution of Xanthomonas pruni bacteriophage adsorbed on a
column of Galestown-Evesboro sandy loam soil after 300 ml
leaching at 1 ml per hour.
198
-------
In the third column study, the objectives were to compare the movement
of poliovirus with the electronegative chloride ion and the electro-
positive sodium ion, to get an estimate of the distribution coefficient
(k) in a wet column, and to determine the virus holding capacity of the
soil under short column conditions.
Chloride, the least sorbed of the monitored substances, was the quickest
to reach an effluent concentration equal to the influent; sodium was
next, followed by the virus, which never exceeded 60% of the initial
concentration even after 20 pore volumes had leached through (Figure
56). The effluent solution was buffered by the soil at a pH of 4.6 for
about 10 pore volumes, then increased to a pH of 6.7, which is approx-
imately that of the buffered influent.
The poliovirus elution curves (Figure 56 and 57) show a sharp decrease
in the rate of virus sorption between 175 and 225 ml of effluent. The
cause of this decrease is not clearly understood, but it is possible
that the soil was dispersed upon sorption of sodium. The dispersion of
the soil reduced the flow rate through the column and allowed longer
equilibration time for virus sorption. The distribution coefficient
could not be calculated from the data because of the lack of uniformity
in the curve for the virus front (Figures 56 and 57).
Despite application of more than 13 pore volumes of the virus solution
to the soil in the columns, the sorption capacity of the columns were
far from being reached. As shown in Figure 58, for the column perfused
with the highest poliovirus concentration (4 x 10 pfu/ml), about 55% of
the total virus retained was sorbed in the first 5 mm section. For the
column perfused with 4 x 10 pfu/ml, 33% was sorbed in the first 5 mm or
in 5.9% of the column length.
DISCUSSION
In the short air-dry soil column the bacteriophage swept through with a
band peak at 30 ml as corrected for water that would have to be dis-
placed had the column been wet (Figure 54). The minimum amount of
eluent to produce a peak of poliovirus from the prewet short column
would have been between 140 to 225 ml (Figure 56). A peak in this
experiment would be indicated by the curve reaching a plateau. This
data seemed to indicate, if virus difference can be ignored, that a
large part of the sorption occurred in the soil on some component that
was not readily wetted, possibly organic matter. The high concentra-
tions of viruses sorbed in the upper portions of the column indicated
that the sorption process involved time. The time requirement also
pointed toward the involvement of organic matter, since sorption in an
organic matter matrix is controlled by the rate of diffusion and
requires time as opposed to the instantaneous processes expected to
occur on soil mineral surfaces. Intermicellular dimensions of clays are
too small for virus diffusion. Sesquioxide gels in the soil must be
considered as sorptive sites because they also contain positive charges
for sorption of the negative virus and have been shown to be involved in
199
-------
u
100
O 80
U
^ 60
± 40
O
_o 20
o"~
0
4 x 1O pfu poliovirus/ml
~ . • • .
pH
0 100 200 300 400
EFFLUENT VOLUME (ML)
9
8
7
6
5
4
x
Q.
Figure 56. Elution of poliovirus from Galestown-Evesboro sandy loam soil.
Chloride and sodium ion concentrations of effluent are also
presented. Rate of leaching was 1 cm per hour. The
column was 150 cm long.
-------
O
80
60
~ 40
LL
O 20
0
0
6
4x10 pfu/ml
5
4x10 pfu/ml
1OO 2OO 300 400
EFFLUENT VOLUME (ML)
Figure 57- Comparison of elution curves of poliovirus supplied
continuously (1 cm per hour) at two concentrations to
columns of Galestown-Evesboro sandy loam soil. Columns
were 3.5 cm long.
201
-------
2 2.4
x
Q
UJ
192
14.4
9.6
LL 4,8
CL
0
4x106 pfu/ml
5
4x10 pfu/ml
0
2O 40 60
COLUMN DEPTH (MM)
80
Figure 58. Distribution of poliovirus adsorbed with depth of
columns of Galestown-Evesboro sandy loam soil after
applying continusouly in the influent of two concen-
trations of poliovirus for 400 hours at 1 cm per hour.
202
-------
diffusion controlled sorption. More studies of instantaneous and dif-
fusion controlled sorption processes in soil are needed.
The long column study indicates that even in the air-dry coarse textured
soil, 60 cm (24 inches) of rain would be required to move the virus to a
water table 150 cm (5 feet) of depth. A rainstorm of this size (60 cm)
is a rare event. Disregarding the upward movement of water by capil-
larity and evaporation at the soil surface, this volume of water coming
in increments in 1 to 6 cm storms would not be expected to move the
virus to a 150-cm deep water table. Between storms the virus solution
would have time to equilibrate with the soil with more of the virus
becoming sorbed at each stepwise movement. Therefore, it seems that in
any normal rainfall sequence it would be very unlikely that a virus,
even in as coarse a textured soil as this one, would be capable of
reaching the groundwater. The continued persistence of the virus in an
infective state so that it would be subjected to an entire year's rain-
fall seems unlikely. Further, if the virus did reach the water table,
lateral movement of the water table through strata should provide further
change for capture of the virus by sorptive surfaces.
Finally, the study was performed in a relatively coarse textured soil.
Location of trenching or surface incorporation sites on finer textured
soil should lower considerably any potential for the virus to move into
the groundwater through the soil profile. It must be recognized, however,
that only a few soils have been examined for their ability to sorb
viruses and as yet the process is not well understood. A much better
understanding of the sorption process as influenced by various soil
factors is needed.
203
-------
SECTION VIII
HEAVY METALS
ANALYSES OF BLUE PLAINS SEWAGE SLUDGES
A cooperative program of sampling and heavy metal analyses was under-
taken with the Blue Plains Wastewater Treatment Plant and the EPA-DC
Pilot Plant. The objective was to determine the sludge metal and
nutrient content for a period of one month. Raw primary and digested
combined primary plus secondary sludge came from Blue Plains and raw
alum-secondary sludge came from the Pilot Plant. Subsequently, sludges
of different types from Blue Plains have been analyzed on a periodic
basis to ascertain variation in metal content over a longer period of
time and to learn more about the effect of wastewater and sludge treat-
ment on sludge metal content.
Procedures
The first set of sludge samples were daily 24-hour composites from the
period February 8 to March 9, 1972. The second set of samples were
composites of digested sludges limed to different pH's in July 1972 for
the pH study described in Section V. The third set of samples were of
sludges produced at Blue Plains in April 1974.
The sludge samples were dried at 60°C, ground, and dry ashed at 500°C.
The ash was treated with concentrated HNOg, again heated to dryness, and
then dissolved in 6 N HC1 on a steam plate. The ash solutions were
filtered (Whatman #42), diluted to volume, and analyzed by atomic absorp-
tion spectophotometry (for Ca, Cd, Cu, Mg, Ni, Pb, and Zn), flame photo-
metry (for Na and K), or colorimetry (for P). Samples were analyzed in
duplicate unless otherwise stated. The drying oven overheated and
ruined most sludge samples in the first series taken after February 14.
Background subtraction was not used in analyses of Cd, Ni, and Pb on the
samples taken during early 1972.
Results
February-March 1972 — The results are shown in Table 51. Note the
small day to day variation in content of most elements. Most elements
were more concentrated in digested than raw sludges because of biolo-
gical degradation of the organic fraction and resulting concentration of
the inorganic fraction. Potassium is water soluble and did not increase
during the digestion process.
The digested sludge was a combination of approximately three parts
primary to two parts secondary waste activated sludge. Hence, the
resultant metal concentrations are a mean of the metal contents of the
two components, which in turn are concentrated by digestion.
204
-------
Table 51. ANALYSES*OF BLUE PLAINS SLUDGES, FEBRUARY 8-14, 1972
% dry sludge
Date
Raw primary - Blue
Feb
Mean
8
9
10
11
12
13
14
Raw alum-secondary
Feb
8
9
10
11
12
13
14
Dry wt
0
0
Plains
0.78
0.82
0.86
1.08
0.78
0.80
1.20
- pilot
1.35
1.54
1.54
1.55
1.27
0.76
1.75
P
0.70
0.73
0.71
0.63
0.68
0.69
0.75
0.70
plant
4.20
3.74
3.94
4.25
4.10
3.94
4.06
K
0. 19
0.24
0.23
0.19
0.21
0.19
0.22
0.21
0.17
0.17
0.18
0.18
0.17
0.19
0.20
Ca
1.38
1.36
1.41
1.32
1.39
1.26
1.36
1.35
1.70
1.46
1.44
1.41
1.49
1.38
1.31
Mg
0.19
0.20
0.22
0.21
0.24
0.22
0.24
0.22
0.21
0.19
0.19
0.20
0.21
0.21
0.22
Zn
740
710
800
750
720
710
760
740
910
880
920
940
990
870
820
Metals ,
Cu
550
460
380
320
450
220
300
380
320
300
310
330
320
280
290
in^/kt; drv sludge
**
Ni
92
102
114
87
81
101
100
97
34
30
30
26
26
26
27
* *
Pb
140
120
170
220
110
240
290
180
170
160
150
ISO
180
210
250
**
Cd
29
30
33
29
26
26
35
30
10
10
10
10
10
10
11
Mean
4.03
0.18
1.46
0.21
900
310
28
190
10
Continued
-------
Table 51 (continued). ANALYSES OF BLUE PLAINS SLUDGES, FEBRUARY 8-14, 1972
ho
o
Digested - Blue Plains
Feb 8
9
10
11
12
13
14
Mean
21.
22.
20.
23.
22.
22.
23.
8
4
7
1
8
5
0
1.
1.
1.
1.
1.
1.
1.
1.
64
58
70
65
73
75
78
69
0.17
0.16
0.16
0.15
0.15
0.15
0.16
0.16
2.46
2.40
2.40
2.40
2.37
2.46
2.45
2.42
0.
0.
0.
0.
0.
0.
0.
0.
39
38
39
36
36
37
37
38
1800
1760
1810
1800
1860
1820
1890
1820
730
670
680
680
700
690
720
700
72
62
66
68
66
71
70
68
640
640
600
620
590
560
570
600
21
20
20
20
20
20
20
20
* All values are mean of replicate analyses.
** No background subtraction.
-------
The secondary sludge component of the digested sludge analyzed in
Table 51, however, was not alum-treated. Hence, the digested sludge
metal contents shown in Table 51 are not a mean of the raw primary and
secondary-alum treated sludges (with allowance for digestion).
The high phosphate concentration of raw alum-secondary sludge resulted
because the alum chemically precipitated the phosphate from the waste-
water. Nickel and cadmium levels were not comparable between sludges
because background subtraction was not used. The Ni and Cd values are
not absolute and are only meaningful to determine day to day variation
in metal within a sludge type.
July 1972 — The results are given in Table 52. Metal concentrations
were slightly lower as the lime content increased. The lime which was
added just prior to dewatering increased the mass of sludge; however
since the lime did not contact treatment plant wastewater, additional
metals were not removed. The final lime content in the sludge was lower
than the initial amount of lime added at the plant because some lime was
lost in dewatering.
April 1974 — Metal concentrations in all different types of sludges
produced at Blue Plains on one day are given in Table 53. There is no
significant difference in metal content in the raw primary, raw secon-
dary, or combined raw primary and raw secondary sludges. The metal
concentrations are about twice as high in the digested as in the raw
sludge because of mass reduction by biological decomposition of organic
matter.
The variability in metal content of digested sludges sampled from 12
different truckloads of sludges produced over 4 days are also given in
Table 53. In some cases the range in metal content is larger than half
of the mean values.
Long Term Variability — There is also considerable variability in
elemental contents of sludge over the long run (Table 54). Systematic
sampling of each type of sludge at a treatment plant over a several year
period is important for determining extent of variability in sludge
metal content, source of metal pollutant, extent of sludge digestion,
effect of chemical treatment, etc.
ANALYSES OF OTHER SLUDGES
A survey of Washington area wastewater treatment plant sludges was
conducted during late 1972 and early 1973 to compare these to Blue
Plains sludge. These results are presented in Table 55. Analyses were
also made of sludges from other towns and cities in the United States
(Table 56). These analyses show that the variation among sludges is
quite great and that extreme concentrations of heavy metals occur in
some sludges (largely industrial cities), while sludges from clearly
domestic sources are usually quite low in metals.
207
-------
Table 52. ANALYSES OF BLUE PLAINS SLUDGE AS INFLUENCED BY LIME
NJ
O
CO
Date
Prepared
7/18/72
7/21/72
7/20/72
Jul 1972
5.8
10.5
12.3
PH**
Oct 1973
6.5
7.2
9.6
Rate
"/ nf
Lime
0
4.6
13.6
added as **
FeCl3
2.2
0.3
7.0
Metals, mg/kg dry
Zn Cu Ni+
1690 710 91
1650 660 73
1500 590 119
Sludge
Cd+
13.8
12.8
10.8
* Samples July 1972, stored, and analyzed October 1973.
** See also Table 39.
+ Corrected by background subtraction.
-------
Table 53. ANALYSES OF BLUE PLAINS SLUDGES, APRIL 1974
Composite
Sludge type of
Liquid, not elutriated
Raw primary 24**
Raw secondary waste-
activated (FcCl3) 24
Raw thickend primary
plus secondary (Fed,) 24
Mean
**
Digested 24
Elutriated, dewatered, digested
Mean
Date
4/1-4/2/74
4/1-4/2/74
4/1-4/2/74
4/1-4/2/74
4/2/74
4/2/74
A/2/74
4/3/74
4/3/74
4/3/74
4/3/74
4/4/74
4/4/74
4/4/74
4/4/74
4/5/74
o,
'9
Solids
2.3
4.2
10.7
3.3
25
22
25
25
24
22
25
26
25
26
25
28
25
Metals , rag/kg oven
Zn
916
1004
1210
1040
2480
2570
2520
2290
2330
2330
2940
2320
2220
2350
2370
2320
1560
2340
Cu
340
290
290
310
670
710
710
660
670
670
820
650
620
680
670
630
440
660
Ni*
33
33
39
35
SO
47
48
44
44
45
58
44
42
45
46
44
43
46
dry solids
Cd*
8
9
9
9
26
25
26
24
24
24
30
22
21
23
23
23
22
24
Pb
380
370
490
410
780
810
810
790
770
770
980
760
720
760
770
740
520
770
* Corrected by background subtraction.
** Twenty-four hourly grab samples composited into one sample.
+ Samples taken from separate truck loads of sludge hauled to the Beltsville composting site.
-------
Table 54. MEAN ELEMENTAL CONTENTS OF BLUE PLAINS SLUDGE
n % dry solids Metals, mg/kg dry solids
N P K
Digested combined primary and secondary
Feb 1972 - 1.7 0.2
M May 1972 2.5 1.1 0.5
H1
0
Jul 1972 -
Apr 1974 -
Raw combined primary and secondary
Feb 1972 - 2.4 0.2
Apr 1974 -
Ca Mg Zn
2.4 0.4 1820
1.6 0.1 2010
1610
2340
1.4 0.2 820
1040
Cu Ni Cd
* *
700 68 20
720
650 94 13
660 46 24
340 62* 20*
310 35 9
Pb
600
—
770
180
410
Background subtraction correction not made on cited numbers only.
-------
Table 55. HEAVY METAL CONTENTS OF WASHINGTON AREA WASTEWATER TRF.ATMENT
PLANT SLUDGES
Type
Zn Cu Ni
mg/kg dry sludge
Cd
Pb
Fairfax County
Lower Potomac
Westgate
Hunting Creek
Hunting Creek
Dogue Creek
R
R
R
D
R
370
660
230
580
290
210
380
250
370
170
60
30
15
25
30
'**
120
Arlington County D 1700 1640 65 18 360
Alexandria R 1030 730 25 17 280
Prince William County
Belmont D(A) 550 150 15 4 160
Neabsco D(A) 740 520 20 5 120
Featherstone D(A) 430 250 15 3 160
Occoquan D(A) 440 190 10 2 60
WSSC
Piscataway D 600 350 35 5 300
Parkway D 1320 500 50 16 700
Western Branch D 960 260 40 10 140
Washington, D.C.
Blue Plains
MES Compost
D
D,C
1610
1140
650
350
80
330
12
9
540
310
R = raw; D= anaerobically digested; D(A) = aerobically digested;
D,C = composted digested; WA = waste activated.
**
Background subtraction not used on cited numbers only.
PLANT GROWTH STUDIES
A series of plant growth studies were undertaken. Effects of metals on
plant growth were compared when added in equivalent amounts as sludge or
as metal salts. A number of different crops were grown because of their
suspected different tolerances to given levels of heavy metals in soils.
Two lime (CaCO«) levels were included because of the dominating effect
of soil pH on metal availability to plants.
211
-------
Table 56. HEAVY METAL CONTENT OF VARIOUS SEWAGE SLUDGES
Type Zn Cu Ni
mg/kg dry sludge
Cd
Pb
Maryland
Baltimore
Hagerstown
Frederick
Cumberland
Westernport
D
D
R
D
D
4970
1500
880
1330
360
2100
980
680
640
130
340
40
100
20
60
20
10
615
15
2
400
490
Others
Corning, New York
Ervin, New York
L.A. County "Nitrohumus"
Grand Rapids, MI
Philadelphia, PA SW (3)
Fostoria, OH
Detroit, MI
Chicago, WSW
"Milorganite"
West Chester, PA
Tiffin, OH
Denver, Colorado
Miami, Florida
"Tex-Organic"
D
D
D
D
R
WA
WA
D
D
D
D
1250
1210
2200
20500
2800
970
4610
2720
1980
730
4520
1670
1780
1880
420
450
730
3140
800
16030
1050
1040
500
120
831
560
500
370
40
40
140
3870
110
120
1210
350
120
50
80
220
240
20
7
10
20
165
30
4
100
235
150
2
<10**
<20**
<6of
<15**
48'
14i
-
_
_
-
_
_
_
_
_
_
—
* D - digested, R = raw, WA = waste activated.
** Background subtraction not used on cited numbers only.
Procedure
Twelve crops listed in Table 57 were grown on each of four treatments:
(1) Evesboro loamy sand + NPK (100 ppm N, 100 ppm P, and 126 ppm K);
(2) Evesboro loamy sand + 5% Crystal Lake peat + NPK; (3) Evesboro loamy
sand + 5% Baltimore digested sludge (adding 186 ppm Zn + 66 ppm Cu) +
NPK; and (4) Evesboro loamy sand + metal sulfates adding 186 ppm
Zn and 66 pprc Cu + NPK. The mixtures were adjusted to approximately pH
5.5 and 6.5 with CaC03 and incubated 2 weeks before seeding. There were
two replications per treatment. The Baltimore digested sludge was used
because it was expected to contain more heavy metals than Blue Plains
sludge. The Baltimore sludge was dried at 50°C and ground in a Wiley
mill before use.
212
-------
Table 57. YIELD OF VARIOUS CROPS GROWN IN EVESBORO LOAMY SAND AMENDED WITH BALTIMORE DIGESTED SLUDGE,
EQUIVALENT RATES OF ZINC AND COPPER, PEAT, AND FERTILIZER ONLY
Crop
Corn
Bean
Swiss chard
Soybean
Tomato
Mustard
Mustard
Turnip
Sugarbeet
Wheat
Rye
Fescue
Seeding pH
Harvest pH
Variety
WF9x38-ll
UI-111 Pinto
Fordhook Giant
Kent
Marglobe
S. Giant Curled
Florida Broadleaf
Seven Top
US H20
Nugaines
Balbo
Kentucky-31
May 1
June 1
Dry matter g/pot
Control
pH 5.5
1.40
1.25
1.50
0.78
0.65
0.48
1.45
1.82
1.50
2.26
1.96
1.11
6.50
6.01
PH 6.5
1.43
1.34
1.11
0.82
0.54
0.28
0.58
1.02
1.09
2.04
1.98
1,00
7.16
6.58
Peat
pH 5.5
2.70
1.39
2.32
1.60
2.46
1.53
2.40
2.76
1.88
2.14
2.51
1.20
6.43
5.95
only
pH 6.5
2.49
1.40
2.06
1.42
2.00
1.50
2.50
2.70
1.87
2.00
2.07
0,85
7.18
6.49
Sludge
pH 5.5
1.10
0.07
0.09
0.16
0.30
0.40
0.09
0.14
0.10
1.20
0.76
0.42
5.83
5.86
pH 6.5
1.69
0.72
0.46
0.73
0.32
0.31
0.59
0.75
0.38
1.33
1.28
0.33
7.23
6.34
Zn, Cu
pH 5.5
0.79
0.14
0
0.13
0.01
0
0
0
0.02
0.48
0.49
0.35
5.90
5.65
salts
pH 6.5
1.44
0.13
0.67
0.64
0.47
0.38
0.28
0.74
0.67
1.19
1.41
0.35
7.11
6.97
-------
Results
The crops, and mean yields of replicate pots are shown in Table 57.
Primary leaves of the bean and soybean were harvested separately and
yields not included. The symptoms of injury and yield on both the
sludge and Zn + Cu treatments were quite pH dependent. The mustard,
turnip, chard, sugarbeet, and tomato were chlorotic at pH 5.5; at pH 6.5
each was stunted, but green. The soybean was extremely stunted at low
pH on the Zn and Cu treatments (but remained green), while at the high
pH, the plants grew enough to become chlorotic. Growth was not as
vigorous as it might have been in all treatments because the soil was
found to be somewhat low in magnesium. In addition, growth of crops in
the sludge amended soil was reduced because of initial toxic effects of
the sludge (salt, low oxygen, and relatively high ammonia). Growth was
significantly enhanced in the peat treatment probably as a result of
improved soil-water relationships.
Low soil pH.had a dominating effect in reducing plant growth when
metals were present either as sludge or as salts. Low pH did not
reduce growth when metals were present only in trace amounts in the
control and in the peat amended soil. A logical conclusion would be,
therefore, that the reduction in growth was probably caused by the lower
pH which caused increased metal toxicity to the different crops. The
soil pH at seeding and harvest are also given in Table 57. While
seeding and harvest pH levels were different, differentials between high
and low pH treatments were maintained.
The Zn and Cu content of leaves of these crops are shown in Tables 58
and 59, respectively. The soil pH strongly effected Zn contents of
leaves for most crops. For a few (chard, rye, wheat, and fescue) this
expected result was not observed. The lack of effect may have been
caused by the interaction of toxic levels of several metals at the low
pH which prevents transport of Zn to the top of the plant. Crops dif-
fered widely in both Zn and Cu accumulation (compare chard vs. fescue).
The considerably increased metal levels in the crops grown in soils
where metals were present and where pH was low would tend to confirm the
view that plant growth was being reduced by metal toxicity. It was
clear that the Zn and Cu present in sludge-soil mixtures were consider-
ably less available and hence less toxic to plants than the same amount
of these metals added as inorganic salts.
The absorption and translocation to plant tops of Cu (and Ni, Pb, and
Hg) differs markedly from Zn (and Cd and Mn). Cu is held in the plant
roots and may kill a plant from Cu toxicity, even though the plant tops
contain less than 100 ppm Cu. Zn is translocated to a much greater
extent and a plant dying from Zn toxicity can contain 2000 to 3000 ppm
Zn in the tops. Along with these differences in absorption-translocation
of Cu and Zn, the content of Zn in plant tops is strongly affected by
liming, while Cu content in tops is usually only slightly affected by
liming.
214
-------
Table 58. ZINC CONTENT OF LEAVES OF VARIOUS CROPS GROWN IN EVESBORO LOAMY SAND AMENDED WITH DIGESTED
SLUDGE, EQUIVALENT RATES OF ZINC AND COPPER, PEAT, AND FERTILIZER ONLY
Crop
Corn
Swiss chard
Soybean
Tomato
Mustard
Turnip
Sugarbeet
Wheat
Rye
Fescue
Variety
WF9x38-ll
Fordhook Giant
Kent
Marglobe
S. Giant Curled
Seven Top
US H20
Nugaines
Balbo
Kentucky-31
Zn , yg/g dry weight
Control
pH 5.5
44
137
48
40
51
51
57
38
38
50
pH 6.5
40
31
43
38
22
32
30
28
32
26
Peat
pH 5.5
32
58
36
37
44
34
58
32
33
37
only
pH 6.5
27
42
28
28
28
32
41
34
34
29
Sludge
pH 5.5
655
1270
444
628
1300
883
1369
194
228
260
pH 6.5
295
1330
222
335
660
650
1193
272
296
301
Zn, Cu
pH 5.5
1410
242
-
-
358
469
899
1037
salts
pH 6.5
726
826
471
158
736
645
642
518
372
365
-------
Table 59. COPPER CONTENT OF LEAVES OF VARIOUS CROPS GROWN IN EVESBORO LOAMY SAND AMENDED WITH DIGESTED
SLUDGE, EQUIVALENT RATES OF ZINC AND COPPER, PEAT, AND FERTILIZER ONLY
Cu, yg/g dry weight
Crop
Corn
Swiss chard
Soybean
Tomato
Mustard
Turnip
Sugarbeet
Wheat
Rye
Fescue
Variety
WF9x38-ll
Fordhook Giant
Kent
Marglobe
S. Giant Curled
Seven Top
US H20
Nugaines
Balbo
Kentucky- 31
pH 5
8
14
6
13
6
8
18
8
7
8
Control
.5 pH 6.5
9
12
4
12
6
7
16
10
8
10
Peat
pH 5.5
7
8
3
8
5
6
10
9
5
10
only
pH 6.5
8
10
4
6
6
8
11
8
8
10
Sludge
pH 5.5 pH
25
42
10
22
67
88
63
12
10
26
6.5
24
44
11
24
44
74
44
12
10
32
Zn, Cu
pH 5.5
42
8
-
-
14
10
24
salts
pH 6.5
36
58
22
29
57
100
55
16
13
28
-------
The phytotoxicity of Baltimore digested sludge applied at disposal rates
on a soil of low cation exchange capacity (1.8 meq/lOOg by sum of cations)
was observed to be substantial and due mostly to Zn, Cu, and B; but for
some crops phytotoxicity was apparently due mostly to soluble salts.
The pH dependence of toxicity surpassed crop or varietal difference in
susceptibility to toxicity as the factor controlling phytotoxicity. The
observation of continued pH lowering, after an initial short-lived pH
rise, and the observed pH dependence of toxic metal injury, suggested
that control of the final equilibrium pH of deep incorporated sludge (as
in trenches) is very important.
217
-------
APPENDIX
Report on Cooperative Research on Trenching
for Period May 1, 1974 through
November 1, 1974
by John M. Walker
Biological Waste Management Laboratory
USDA-ARS-NER-AEQI
Beltsville, Maryland
Research Conducted Under Interagency
Agreement EPA-IAG-D4-0510
Project Officer
G. Kenneth Dotson
Research Soil Scientist
Environmental Protection Agency
Cincinnati, Ohio
Persons who conducted parts of this research include:
J. M. Walker, L. Ely, T. Lathan, M. C. White, E. Levesque,
A. Burgoon, J. Marmelstein, T. Palmer, W. D. Burge, and
R. L. Chaney, from USDA, EPA, and MES, and A. M. Decker,
D. Hafner, and D. Hill from the University of Maryland.
218
-------
The studies on sludge entrenched in 1972 were continued. Nitrogen,
chlorides, metals, pH, and coliform and salmonella bacteria were meas-
ured in entrenched sludge and in soils surrounding the trenches (Tables
1A-7A). Samples for these analyses were obtained from cross-sections
dug in June 1974 across the digested sludge treatments (trenches 60 cm
wide x 60 cm deep x 60 cm apart [60-60-60] and 60-120-120) and across
the raw-limed sludge treatment (60-60-60).
Since the width of trench was not a variable, the two factors affecting
the distribution of materials from sludge in soil around individual
trenches were depth of trench (60 vs 120 cm) and kind of sludge (diges-
ted vs raw-limed).
Two years after entrenchment, digested sludge in the shallow trenches
had been penetrated the deepest by plant roots. This caused dewatering,
favored further decomposition, and apparently induced generally aerobic
conditions. As a result most of the inorganic N was in the nitrate
rather than the ammonium form (Tables 1A and 2A). This nitrate concen-
tration around these trenches was generally higher at 2 years than it
had been at 17 months. The deeper digested sludge trenches, even after
2 years, were only partially penetrated by roots and therefore, still
anaerobic in the lower portion. Consequently, nitrification was
inhibited and NH^-N predominated over NC^-N. The same was true for the
shallow trenches of raw sludge. In this case root penetration appeared
to be inhibited by toxicity factors associated with the raw-limed sludge.
These toxicity factors have not been defined. Slower sludge decompo-
sition is probably desirable from the standpoint of slow release of
N03-N.
The pH of the entrenched sludge and the soil below (Table 3A) is related
to the predominant form of N present (Table 1A and 2A), which in turn is
partly related to the degree of sludge decomposition and aeration. The
pH is higher when the NH^-N form of N is present. It will be interest-
ing to see how high the pH will remain when NO^-N becomes the predomi-
nant form of N in and around high lime sludge.
Chloride movement out of the different entrenched sludges (Table 4A) was
apparently not closely related to the degree of sludge decomposition.
Chloride movement was somewhat greater under the raw-limed than digested
entrenched sludges at both sampling dates. Chloride movement into soil
below the trenches was less in all cases at 25 than at 17 months while
NO-}- and NH^-N movement had increased in most cases over the same period.
period.
A small amount of Zn had moved down at least 45 cm from the most decom-
posed aerobic sludge (60-60-60 digested, Table 5A) 25 months after
entrenchment. Zn had not yet moved, however, out of the less decomposed
aerobic digested sludge in the 60-120-120 trenches. Zn also had not
moved out of the 60-60-60 entrenched raw-limed sludge. This movement of
Zn out of the 60-60-60 entrenched digested sludge is probably related to
the low soil and sludge pH (Table 3A), which in turn is related to the
219
-------
degree of decomposition, the form of N, and the presence of lime.
Additional experiments will have to be run to determine whether this
increased movement of Zn is related solely to chemical changes associ-
ated with changes in pH or to other changes in chemical status due to
decomposition. Cu had not moved out of any entrenched sludge (Table
6A). Cu is more strongly bound than Zn.
No fecal coliform or salmonella bacteria were detected in any of the
sludges or in the soil below at either 17 or 25 months after entrench-
ment. Only total coliform bacteria were still surviving. In one
instance these bacteria apparently moved 45 cm below the entrenched
sludge (Table 7A).
In a cross-section previously dug across a 60-120-120 digested sludge
trench (November 1973), sludge had mostly been converted into a moist
peat-like structure without roots. This pit was dug on the upper side
of the plot with the water table at approximately 4 to 5 m below the
sewage sludge. In June 1974, a cross-section was dug across the same
treatment area in a region where the water table was approximately 2 m
below the soil surface. Much of this sludge was unchanged from its
original sludge-like consistency, suggesting that closeness to water
table may have a bearing on the speed of sludge decomposition. This
possibility will have to be studied in the future for verification.
The 60-60-60 raw-limed sludge was still slowly being converted from a
sludge-like to peat-like consistency. The peat-like zone extended from
the top approximately 1/4 of the way down into the entrenched sludge.
The part of the sludge converted to peat-like consistency contained
roots. The water table was approximately 1.5 m below the soil surface
in this treatment. Perhaps this high water table was partly responsible
for the slow dewatering. We have had no raw-limed sludge treatment in
areas where the water table was deeper.
Subsurface and drainage water has been monitored since the beginning of
this study (Table 8A). These water samples are taken from: (a) sample
wells throughout the site, (b) drain lines around the site, and (c) a
catchment pond receiving drain line flow and surface runoff.
Analyses of well waters have not as yet shown increased levels of N0o~
or NH^-N; but increased levels of chloride compared with before sludge
application were still observed 25 months after entrenchment. In tile
drainage water, NO.,-N in particular has steadily increased while
chloride has increased and then decreased. Levels of NOo- and NH^-N
in the pond water are considerably below the levels in drainage water
and have not as yet reached hazardous levels. Chloride levels in the
pond have remained low and have not undergone appreciable change. There
is some possibility that surface and perhaps even subsurface water with
low levels of NO^- and NH^-N and chloride have entered the pond and
caused some dilution. Whether there has been loss or dilution of these
materials by some other mechanism is not known. Analyses of sludge,
soil, and water samples continues to indicate that movement of N03~N may
be an important problem at soil entrenchment sites.
220
-------
Samples of fescue and alfalfa plants were taken that were growing over
the sample trenches (Table 9A), and between and directly over other
trenches (Table 10A). Uptake of Zn by fescue was approximately 4 times
greater in plants grown over digested than raw sludge. Uptake of Cu and
B was approximately 2 times greater over the digested than the raw
shallow trench treatments. This lower uptake over raw sludge reflects
both its lower initial trace element concentration and its higher lime
and pH level. Highest metal uptake by fescue occurred in plants growing
directly over trenches (Table 10A), while alfalfa plants absorbed metals
independently of their location with respect to the entrenched sludge.
These results indicate the greater spread of alfalfa roots in the soil.
221
-------
Table 1A. NITRATE-NITROGEN MOVEMENT INTO SOIL FROM ENTRENCHED SLUDGE
ro
r-o
Location
Above sludge
Entrenched
sludge
Cm below
sludge
. *
1 **
11
2.5
15
30
45
60
N03-N (yg/g dry
Raw
17
13
1,900
110
243
45
7
7
6
wt) in
limed
25
10
496
586
4
4
3
3
4
and around sludge in
60-60-60
Digested
17
5
1,200 1,
40 1,
25
21
12
15
8
trenches
25
1
076
654
39
13
12
7
4
with time (months)
60-120-120
Digested
17
-
600
40
3
3
3
5
2
25
2
9
35
2
2
8
8
4
* More weathered, aerobic sludge.
** Less weathered, less aerobic sludge.
-------
Table 2A. AMMONIUM-NITROGEN MOVEMENT INTO SOIL FROM ENTRENCHED SLUDGE
to
LO
Location
Above sludge
Entrenched
sludge
Cm below
sludge
A
1 **
11
2.5
15
30
45
60
NH4-N (yg/g
Raw
17
1
28
2,523
232
91
31
9
1
dry wt)
limed
25
4
78
7,411
420
373
96
95
38
in and around slud£
60-60-60
Digested
17
7
439
4,392
104
90
64
57
28
*e in
25
1
14
206
10
6
4
2
2
trenches with time (months)
17
-
362
2,990
152
134
51
28
7
60-120-120
Digested
25
1
14
3,992
134
124
60
44
42
* More weathered, aerobic sludge,
** Less weathered, less aerobic sludge
-------
Table 3A. THE pH OF ENTRENCHED SLUDGE AND SURROUNDING SOIL
The pH in and around sludge in trenches with time (months)
Location
-P-
60-60-60
Raw limed
17
25
* More weathered, aerobic sludge.
** Less weathered, less aerobic sludge.
Digested
17
25
60-120-120
Digested
17
25
Above sludge
Entrenched
sludge
Cm below
sludge
A
1 **
ii
25
15
30
45
60
4.3
4.1
7.4
6.5
5.4
4.5
4.8
4.7
5.7
6.7
7.3
8.3
8.3
8.0
7.8
7.4
4.9
6.9
6.9
4.7
7.3
7.2
7.3
7.2
5.2
5.1
5.5
4.5
4.7
4.6
4.7
4.7
—
5.1
7.8
7.4
4.8
4.6
4.4
4.5
4.5
5.0
8.0
8.0
7.9
7.5
6.9
6.5
-------
Table 4A. CHLORIDE MOVEMENT INTO SOIL FROM ENTRENCHED SLUDGE
ro
Ln
Location
Chloride
(yg/g dry wt) in
60-60-60
and
Raw 1 imed
Above sludge
Entrenched
sludge
Cm below
sludge
i***
11
2.5
15
30
45
60
17
18
23
4,900
102
51
29
36
10
25
29
1,196
5,360
55
59
40
32
36
17
-
123
5,300
97
48
30
46
30
around sludge in
Digested
25
22
50
1,332
40
27
24
23
22
trenches with time (months)
17
-
33
4,150
69
68
33
52
41
60-120-120
Digested
25
8
31
4,025
49
49
42
34
31
* More weathered, aerobic sludge.
** Less weathered, less aerobic sludge.
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Table 5A. TOTAL AND DTPA EXTRACTABLE ZINC MOVEMENT INTO SOIL FROM ENTRENCHED SLUDGE
t-o
to
Zinc (yg/g dry
Location
wt) in and around
sludge
in trenches with
60-60-60
Raw limed
Above sludge
Entrenched i
sludge ii
Cm below 2.5
sludge 15
30
45
60
17
DTPA
0.4
313
215
0.5
0.1
0.2
-
0.1
DTPA
1.1
328
367
0.1
0.2
0.2
0.4
0.1
25
Total
15
769
660
6
-
-
-
3
Digested
17
DTPA
0.4
1,060
490
0.8
0.2
0.1
0.0
0.2
DTPA
0.3
647
548
8.8
2.6
0.9
0.7
0.3
25
Total
13
1,249
1,228
32
12
7
4
3
17
DTPA
1.3
_
582
0.3
0.2
0.2
-
0.2
time (months)
60-120-120
Digested
DTPA
0.5
1,197
665
0.1
0.1
<0.1
0.1
<0.1
25
Total
13
1,300
1,044
3
2
2
1
~
* More weathered, aerobic sludge.
** Less weathered, less aerobic sludge.
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Table 6A. DTPA EXTRACTABLE AND TOTAL COPPER MOVEMENT INTO SOD FROM ENTRENCHED SLUDGE
Copper (yg/g dry wt) in and around sludge in trenches with time (months)
Location
60-60-60
Raw limed
Above sludge
Entrenched
sludge
Cm below
sludge
. *
11
2.5
15
30
45
60
17
DTPA
0.4
113
58
0.5
0.3
0.3
-
0.3
25
DTPA Total
0.6
208 425
129 378
0.3 3
0.4
0.3
0.2
0.2 2
60-120-120
Digested
17
DTPA
0.5
365
22
0.4
0.4
0.3
-
0.1
DTPA
0.2
289
160
0.2
0.1
0.1
0.1
0.1
25
Total
4
544
466
5
3
3
2
2
17
DTPA
0.7
-
74
0.5
0.4
0.3
-
0.6
Digested
DTPA
0.4
322
80
0.2
0.1
0.1
0.2
0.2
25
Total
4
928
359
3
2
2
1
—
* More weathered, aerobic sludge.
** Less weathered, less aerobic sludge.
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Table 7A. TOTAL COLIFORM MOVEMENT INTO SOIL FROM ENTRENCHED SLUDGE
ro
ro
oo
Total coliform (MPN/g
dry wt) in and
around
sludge in trenches with time (months)
60-60-60
Location
*
Entrenched i
sludge ii
Cm below 2 . 5
sludge 15
30
45
60
Raw
17
180,000
590
10
<3
<3
<3
<3
limed
25
150,000
3,000
970
380
1,100
1,100
<3
Digested
17
32,000
68 23,
<3
<3
<3
<3
<3
25
<5
000
<3
<3
<3
<3
<3
17
27,000
<7
3
<3
<3
<3
<3
60-120-120
Digested
25
62,000
<9
<3
<3
<3
<3
<3
* More weathered, aerobic sludge.
** Less weathered, less aerobic sludge.
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Table 8A. CONTENTS OF NH -N, NO -N, AND Cl IN UNDERGROUND, DRAINAGE, AND STORED WATER FROM
TRENCH AREA
mg/1 in water
Date
Well 16 *
NH4-N N03-N
Before sludge
(Apr. 72) <1 <1
Oct.
Nov.
Jan.
Mar .
Apr.
July
Aug.
Nov,
73 <1 1
73 <1 1
74 <1 1
74 <1 1
74 <1 1
74 <1 1
74 <1 <1
74 <1 <1
Cl
2
90
64
49
64
46
48
39
42
Drain 71 **
NH4-N N03-N
<1 <1
7 5
15 7
4 12
4 21
12 21
9 14
-
6 30
Cl
10
32
80
106
117
90
36
-
33
Pond
NH4-N N03-N
-
<1 5
<1 5
<1 3
<1 6
1 7
1 8
-
1 7
Cl
-
33
44
20
43
35
39
-
31
* A representative well located in area B in 60-60-60 digested sludge trench plot,
** Drains plot area A in sandy soil.
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Table 9A. ELEMENTAL CONTENT OF FESCUE HARVESTED OVER THE 60-60-60
ENTRENCHED SLUDGE* AFTER 25 MONTHS
Sludge
type
Digested
Raw
Digested
Raw
Element
Major, %
N P K Ca
2.5 0.23 1.41 0.75
2.5 0.30 2.18 0.53
Minor, yg/g dry wt
Zn Cu Mn Fe
120 12 264 86
28 6 195 79
Mg
0.29
0.29
B
9
5
* There was approximately a 25 cm layer of soil without sludge covering
the entrenched sludge.
230
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Table 10A. ELEMENTAL CONTENT OF FESCUE AND ALFALFA^GROWING OVER AND
BETWEEN 60-60-60 DIGESTED SLUDGE TRENCHES
AFTER 25 MONTHS
Element
Plant and
location
Major, %
N
K
Ca
Minor, yg/g dry wt
Mg
Fescue
between trenches
over trenches
Alfalfa
between
over
2.3
3.7
4.4
4.6
0.34
0.40
0.40
0.39
2.80
2.55
2.21
2.13
0.49
0.66
1.16
1.30
0.29
0.66
0.34
0.33
Zn
Cu
Mn
Fe
Fescue
between
over
Alfalfa
between
over
71
173
162
173
5
7
9
9
219
279
113
139
53
58
87
69
3
4
22
23
* There was approximately a 25 cm layer of soil without sludge covering
the entrenched sludge.
231
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-75-034
3. RECIPIENT'S ACCESSI ON-NO.
4. TITLE AND SUBTITLE
TRENCH INCORPORATION OF SEWAGE SLUDGE IN MARGINAL
AGRI-CULTURAL LAND
5. REPORT DATE
September 1975 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
J. M. Walker,^} W. D. Surge, R. L. Chaney, E. Epstein,
and J. D. Menzies
'8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Dept. of Agriculture, Biological Waste Management
Laboratory,ARS, Beltsville,MD; for Maryland Environmental
Services, Annapolis,MD; and Government of the District
of Columbia, Dept. of Env. Services, Washington, D.C.
10. PROGRAM ELEMENT NO.
TRttfUT (KOAP 71-ASK. Task 0?71
11. CONTRACT/SaSSailJ NO.
68-01-0162
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD-COVERED
Final, 10/71 to 1/74
14. SPONSORING AGENCY CODE
EPA-ORD
15. SUPPLEMENTARY NOTES
Address of Authors:
U.S. Department of Agriculture
Biological Waste Management Laboratory
Agrinilt-nrp Research Service, Beltsville. Maryland
16. ABSTRACT
A trench method was tested for transporting and placing digested and limed raw
(undigested) sewage sludges (8% and 20% solids) in trenches in study soil at loadings
up to 1150 dry tons/hectare (500 dry tons/acre) without odor problems or hazard of
surface runoff. Field scale trenching was best achieved by digging the trenches on
contour not more than 75 cm deep, 60 cm wide, and from 60 to 75 cm apart. The study
indicated that the best sludge transport method would employ concrete mixer trucks.
Trenches could then be filled directly from discharge chutes or indirectly with a
peristaltic pump. A tracked trenching machine with a maneuverable rear-mounted
digging wheel dug a new trench and simultaneously backfilled a parallel sludged
trench. In 2 years, neither heavy metals nor pollution indicator organisms
(coliform and salmonella) have moved more than about 30 cm from entrenched sludge
into surrounding soil. Moderate amounts of nitrate nitrogen have moved into
underdrainage water but not into the underground aquifier. The lime in the sludge
reduced metal movement into soil and availability to crops and metal uptake was
modest. Tested agricultural practices included cross ripping, tilling, and cropping,
with grasses recommended for the first year. Entrenchment appeared feasible for sludge
disposal and improving marginal land.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDEDTERMS fa COSATI Field/Group
Sludge disposal*
Land reclamation*
Trenching*
Salmonella
Coliform bacteria
Limed raw sludge*
Digested sludge*
Lime
Metals
U.S. Agricultural
Research Service,
Beltsville, Maryland
13B
3. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
250
t
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
232
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