AGRICULTURAL BENEFITS AND ENVIRONMENTAL CHANGES
RESULTING FROM THE USE OF DIGESTED SEWAGE SLUDGE
ON FIELD CROPS
An Interim Report on a Solid Waste Demonstration Project
This report (SW-30d) was prepared by T. D. HINESLY, 0. C. BRAIDS,
J. E. MOLINA, University of Illinois,
under solid waste demonstration grant G06-EC-00080, to the
Metropolitan Sanitary District of Greater Chicago,
and is reproduced as received from the grantee.
U.S. ENVIRONMENTAL PROTECTION AGENCY
1971
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price 65 cents
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An environmental protection publication
in the solid waste management series (SW-30d)
Single copies of this publication are available from solid waste
management publications distribution, Office of Solid Waste Manage-
ment Programs, U.S. Environmental Protection Agency, 5555 Ridge
Avenue, Cincinnati, Ohio 45213.
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FOREWORD
In April 1967 the Federal solid waste management program together
with the Metropolitan Sanitary District of Greater Chicago initiated a
project to demonstrate the possible agricultural benefits and environ-
mental changes that would result from applying digested sewage sludge
to field crops. In addition, criteria are to be developed that can be
used in selecting sites for this method of sludge disposal. This publi-
cation reports on the progress made after three year's work on this
project.
Since agronomic field studies require a minimum of three years to
integrate seasonal effects with measured parameters, the longer the dur-
ation of a field study, the greater the confidence level of the results.
Construction and instrumentation of the lysimeter facility used for the
present project was completed in Spring 1969. Therefore, one year of
data—detailed climatic measurements, runoff and drain water analyses,
and sludge applications—have been collected from the facility.
The statements made herein are thus based on data that have not
yet been analyzed statistically, so that conclusions must be considered
as tentative. We expect, nevertheless, that publication of this report
will be useful in the interim period required until a thorough evaluation
and interpretation of data are completed.
iii
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PREFACE
While the new lysimeter facility at the Northeast Agronomy Research
Center of the University of Illinois was being established, peripheral
experiments were conducted on existing small drum-type lysimeters. These
preliminary experiments included high sludge loading rates, analyses of
percolated water, fecal coliform analyses of soil surfaces, and various
crop tolerances to sludge applications. A continuation of these experi-
ments will permit: (1) continued study of increased sludge accumulations;
(2) an increase in the confidence with which predictions of deleterious
effects on agronomic crops, if any, might be expected under practical field
conditions; (3) study of weathering rate of sludge residues; (4) study of
the chemical regime in percolated water.
The Northeast Agronomy Research Center lysimeter facility, now in oper-
ation only one year, is uniquely suited to evaluate the feasibility of dis-
posing of digested sludge on agricultural land. The following parameters
can be studied:
1. Factors relevant to the bacteriological contamination of water
and soils.
a. The total counts of fecal coliforms in surface runoff water
from field lysimeter plots as a function of number added by a
digested sludge application, time after a sludge application,
rainstorm intensity and duration, total runoff, and environmen-
tal conditions such as radiation, temperature, ground cover, etc.
b. The total fecal coliform counts in drainage water from lysi-
meter plots as a function of all of the factors stated in "a"
except for rainstorm intensity and duration.
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c. Whether or not an equilibrium condition between rate of re-
newal and rate of die away is established at some depth in a soil
profile. If such a zone is found to exist, determine factors
that may influence the depth at which it is established.
d. The total fecal coliform counts in runoff water as a function
of distance from point of sludge application for several ground
cover conditions and rates of travel (or flow rates of runoff
water) during the several seasons of the year.
2. Factors relevant to the chemical contamination of water and soils.
a. The concentrations of the various forms of nitrogen and total
phosphorus in drainage water from the field lysimeter plots as a
function of total concentrations added by sludge applications, time,
effluent volumes, soil cover and other soil environmental conditions.
b. The concentrations of heavy metals (of major significance for one
reason or another) in drainage waters as a function of the factors
discussed under "a" immediately above.
c. The concentrations of nutrient elements, and important heavy
metals in the solution and sediment phases of runoff water from the
lysimeter plots, as a function of sludge loading rates, time, total
runoff, rainstorm intensity and duration, and ground cover and other
environmental conditions.
d. The conductivities, pH, and Eh of both drainage and runoff water
from the lysimeter plots as a function of the variables noted res-
pectively in "a" and "c" immediately above.
e. The total soil organic carbon contents with time as a function
of sludge loading rates and soil type.
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f. The total concentrations of heavy metals, pH, and conductivi-
ties at three depths in lysimeter soil profiles as a function of
time and sludge loading rates.
g. The concentrations of N, P, K and heavy metals in plant
tissue samples twice during a growing season as a function of
sludge loading rates and soil type.
h. Characterize sludge organic matter fractions immediately after
application and at least annually thereafter.
3. Physical changes in soils that may be attributed to sludge appli-
cations . Determine soil infiltration and aeration capacities as
a function of time, sludge, loading rates, and soil types.
4. Responses of agronomic crops to sludge applications. Determine
yields and composition of crops as a function of time, sludge
loading rates, and soil types.
The preliminary studies indicate that weed control is a major problem
when sludge is applied to agricultural land. Application of sludge distates
the use of herbicides and insecticides for effective weed and insect control.
As the organic matter content of soil changes with time, the effectiveness
and fate of pesticides will surely change. Thus, a natural extension of this
project is an investigation of factors such as:
1. The concentration of pesticides in runoff and drainage water from
the lysimeter plots as a function of time, effluent volumes, sludge
loading rates, soil type, etc.
2. The persistence of pesticides in sludge-amended soils.
The data collected during the 1969 cropping season will only become
significant if supported by another two or three year's results. The
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influence of climate on sludge applications to agricultural lands must
be measured for several years before the results can be correlated with
existing long-term weather data. Similarly, the gradual changes in soil
properties resulting from sludge applications are accumulative and may
take several years to become apparent. It is important, therefore, that
the study be continued until such changes, especially if deleterious,
become evident.
viii
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TABLE OF CONTENTS
Chapter Page
I INTRODUCTION 1
II PROPERTIES OF LIQUID DIGESTED SLUDGE WITH
RESPECT TO LAND DISPOSAL 3
Chemistry of Liquid Digested Sludge 3
Seed Germination in Liquid Digested Sludge 3
Volatilization of Ammonia from Liquid
Digested Sludge 6
Effect of Digested Sludge on the Soil
Atmosphere, Nitrification and
Dentrification 7
Digested Sludge Dewataring on Soils 9
III GREENHOUSE STUDIES 13
Greenhouse Studies on Nutrient Uptake and
Growth of Corn on Sludge-Treated Plots 13
IV SOUTH FARM LYSIMETER RESEARCH 15
Yields 15
Plant Chemistry 19
Soils 26
Leachates 26
V INSTRUMENTED PLOTS AT THE NORTHEAST AGRONOMY
RESEARCH CENTER 34
The Field Research Facility 34
Supplemental Field-Plot Studies 43
IX
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VI HYGIENIC ASPECTS OF LIQUID DIGESTED SLUDGE 47
DISPOSAL ON CROPPED LAND
Fecal Conforms in Liquid Digested Sludge 47
Fecal Coliforms in Soils Irrigated with
Liquid Digested Sludge 52
Influence of Soil Moisture on Fecal
Coliform Survival 54
VII CONCLUSIONS 57
Established Facilities 57
Results 57
VIII REFERENCES 60
IX ACKNOWLEDGMENTS 62
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INTRODUCTION
The disposal of liquid digested sludge on land is a practice extensively
used. It has recently received more attention in the U. S. because of the
high cost of alternate means (drying processes) of disposal and their effect
on air quality. Land disposal has the additional advantage of returning
the materials to a natural cycle which could be agriculturally beneficial.
Before initiating such a land disposal operation, laboratory, greenhouse,
and field investigations were initiated to determine, 1) the most practical
amount, frequency, economical method, and time for applying digested sludge
on crop land; 2) the probability of contaminating surface water and ground-
water aquifers with pathogens and molecular organic and inorganic ions;
3) the changes in the soil related such physical and chemical characteristics
that might be expected from frequent heavy applications of digested sludge;
and 4) the crops and cropping systems that will provide maximum absorption
of certain essential and non-essential elements supplied to the soil by
digested sludge applications.
To that end, a field installation was planned which would allow us to
evaluate the long-term effects on the soil-water-crop ecosystem of sludge
disposal on land.
An experimental facility was established on the Northeast Agronomy
Research Center (NEARC) near Elwood, Illinois. A large installation of
44, 50 x 10 foot experimental plots complete with equipment to collect,
record, and sample, on a proportional volume basis, the runoff and drain
water was completed on the site.
When the project was initiated in April 1967, it was known that the
field facility could not be functional for the 1967 cropping season. Thus, an
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existing lysimeter facility on the Agronomy South Farm at the University of
Illinois, U-C, was used to begin the investigation.
The following report contains preliminary data collected from all
facilities and supplemental laboratory and greenhouse investigations.
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PROPERTIES OF LIQUID DIGESTED SLUDGE WITH
RESPECT TO LAND DISPOSAL
Chemistry of Liquid Digested Sludge
Liquid digested sludge is characterized as a 2-5% suspension of hetero-
genous solid matter in a dilute aqueous salt solution. The material is a
black slurry which may be transported by pumping.
Ammonium-N, sodium, and potassium are found in the liquid phase and heavy
metals and organic residues are usually found in the solid phase of digested
sludge. Table 1 gives an average chemical composition of digested sludge sam-
ples taken from the Calumet Plant of the Metropolitan Sanitary District (MSD).
Seed Germination in Liquid Digested Sludge
Occasional reports of seed germination inhibition, following the applica-
tion of liquid digested sludge on soils, are found in the literature. Although
a salt effect is cited as the origin of this inhibition, there is no good
evidence to support this hypothesis. Experiments were started to investigate
the true nature of this inhibition. The seeds were first immersed in the
digested sludge for 6 hours. They were then incubated in a petri-dish on 2
layers of filter paper (Whatman No. 1) soaked with 5 to 6 ml of digested sludge.
The inhibitory action of the digested sludge from the Calumet Plant, MSD
on seed germination is indicated by the data in Table 2. The toxic properties
were localized in the sludge supernatant; the ashes from the sludge supernatant
were not toxic. The partial inhibition by the total sludge ashes indicates
the possibility of some salts of toxic metal effects.
The incubation of the seeds, particularly of soybeans, with the digested
sludge inside a petri-dish induced a microbial fermentation which may have caused
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Table 1. Composition of digested sludge from the Calumet Treatment
Plant, Metropolitan Sanitary District.
Component
Total N
Ammoniun-N
P
K
Cr
Cd
Cu
Pb
Mn
Ni
Zn
In solids
C
H
N
Concentration, ppm
1000 -
500 -
700 -
150 -
10 -
10 -
30 -
15 -
7 -
1 -
72 -
~
22 -
3 -
3 -
3500
2000
1550
175
50
35
^5
33
15
3
292
—
27$
tyt
3.5%
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Table 2. Inhibitory effect of digested sludge on seed germination.
Percentage Germination
corn soybean
Control *
Sludge
Sludge supernatant
Ashes from total sludge
Ashes from sludge supernatant
100
19
0
50
100
100
0
0
66
100
-k
*Seed germination in 10 M CaCl? aqueous solution.
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the inhibition. However, when the assay was performed aseptically with auto-
claved sludge, or with the sludge supernatant sterilized by filtration, the
microbial fermentation was avoided but the inhibition persisted. Thus,
microbial fermentation apparently did not cause the inhibition.
Confirmation of the fresh sludge toxicity toward seed germination was
obtained in a greenhouse experiment with corn seeds planted 1 inch deep in
sand. It was found that the equivalent addition of 1 inch of fresh digested
sludge totally prevented seed germination, while the application of 2 inches
of old digested sludge (aerated for 1 week) did not interfere with the
germination.
The toxicity was removed by boiling of the sludge for a few minutes.
Aeration of the liquid digested sludge by bubbling air through it for 5 days
was sufficient to remove the toxicity.
Aging of the sludge in equilibrium with the atmosphere also reduced the
toxicity. Although aeration was more efficient in reducing toxicity, it was
not necessary. Indeed, Lunt (1) observed that soils amended with lagooned
digested sludge were better for seed germination than those amended with
fresh digested sludge.
Volatilization of Ammonia from Liquid Digested Sludge
Investigations conducted by Dr. R. I. Dick and assistants, Department of
Civil Engineering.
In view of the probable limitations imposed by water pollutional character-
istics of nitrogen in sludge, studies of possible inoffensive losses of nitrogen
are pertinent. A loss which has been poorly quantitied is the escape of am-
monia from liquid sludge by gas transfer. Such losses could occur in digested
sludge storage facilities, during application, and following application.
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A laboratory investigation of ammonia volatilization from liquid digested
sludge was conducted using 8 in. diameter plexiglas columns. The gas evolved
from each column was collected and bubbled through standard sulfuric acid to
determine the amount of ammonia given off; and liquid samples were taken
from various depths in the columns to construct an ammonium profile through
the sludge. Results indicated that, at a temperature of 25°C and pH of
approximately 7.5, the rate, of deamination of organic nitrogen in the sludge
exceeds the rate of ammonia movement to the surface and transfer to the
atmosphere. Loss of gaseous ammonia at the surface of the sludge was nearly
linear with time. A mathematical model of NH3 volatilization from liquid
digested sludge based on diffusion theory and an approximation of the deamina-
tion process has been developed and programmed for digital computer analysis.
Use of the model permits prediction of the influence of variables such as
depth, pH, and mixing on nitrogen loss.
Effect of Digested Sludge Application on Soil Atmosphere,
Nitrification and Denitrification
Investigations conducted by Dr. R. I. Dick and assistants, Department of
Civil Engineering.
The fate of nitrogen in sludge which is added to soil is highly dependent
on the level of dissolved oxygen in the soil water. With normal soil condi-
tions, ammonia is oxidized to the mobile nitrate form which may be lost by
leaching. If anaerobic conditions are created in soil containing nitrates,
denitrification occurs with the usual evolution of nitrogen gas to atmosphere.
A preliminary laboratory study was conducted to evaluate the effect of
sludge application on oxygen concentrations in soil. Rates of denitrification
of nitrates added to sludge-soil mixtures were also evaluated.
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Experiments were conducted in laboratory lysimeters containing 5.5 ft.
of Plainfield sand. A free water surface was maintained at the bottom of
the lysimeters. Liquid digested sludge was added each week to the top of
the lysimeters without mixing. Four lysimeters were used and rates of appli-
cation were 0.25, 0.5, 0.75, and 1 in./wk. In addition, 0.5 in. of water
was added to each of the columns weekly to simulate rainfall.
Samples collected at a depth of 2 in. below the surface of the soil
following sludge applications indicated that total anaerobic conditions were
not created during the first several hours following sludge applications of
up to 0.75 in. In the column receiving 1 in./wk of sludge, soil pores at the
2 in. level were filled with moisture and hence anaerobic conditions would be
expected near the surface of that column.
In all of the lysimeters, oxygen concentrations in the air within the
soil decreased with depth and the abundance of carbon dioxide increased with
depth. During the first day following sludge application, the carbon dioxide
level was highest in the columns receiving the largest amount of sludge.
However, with time, the carbon dioxide level decreased in the heavily dosed
columns to levels below those in the columns receiving less sludge. After
a week, the depletion of oxygen in the soil was greatest in the lysimeter
receiving the least amount of sludge.
Nitrate profiles in the soil columns receiving varying amounts of sludge
were obtained after varying lengths of time. Nitrates were first detected
in the lysimeter leachate after 3 weeks of operation. Differences in the
nitrate concentration of the soil moisture in the four lysimeters were not
proportional to the differences in the amount of sludge which the columns
received. After 5 weeks, soil moisture nitrate concentrations had reached
maximum levels of from 300 to 800 mg/1 although high levels had not yet been
detected in the leachate.
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It is of interest to know whether nitrate formed in the soil could be
evolved as gas through creation of controlled anaerobic conditions. In
separate laboratory studies, nitrates were added to digested sludge to
assess the probable maximum rate at which denitrification might be expected
to occur. The rate of denitrification of nitrates in sludge was found to be
independent of the nitrate concentration until the nitrate level reached
1 or 2 mg/1. The maximum rate of the zero order reaction observed was about
10 mg/1 of nitrate per hour at room temperature, although the rate depended
on the characteristics of the digested sludge.
The rate of denitrification of nitrate added to a mixture of sludge and
soil was compared to denitrification in sludge alone. In the sludge-soil
mixture, the rate of denitrification continued to be independent of nitrate
concentration, but denitrification proceeded at a slower rate than in sludge
alone.
Digested Sludge Dewatering on Soils
The rate at which digested sludge dewaters after application on crop
land is one parameter which is needed to determine possible application
frequencies and loading rates.
The rate of digested sludge drying as a function of convective and rad-
iative heat transfer has been reported by Quon and Ward (2) and Quon and
Tamblyn (3). By varying temperatures, humidity differences and flow rates of
air over a broad range of values, it was found that when sludge temperatures
were low and the air humidity was high, the rate at which digested sludge dried
by convective heat transfer was only about one-half the rate of evaporation
from a free water surface. However, when sludge temperatures were high and
air humidity was low, the rate of convective drying of digested sludge
approached the rate of evaporation from a free water surface.
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When evaporation was produced as a result of only radiant energy inci-
dent on the surface, the rate of evaporation from a digested-sludge surface
and a free-water surface were found to be essentially equal. At an intensity
of 1.0 cal per sq. cm per min., the evaporation rate was 0.9 x 10"^ gm per
sq. cm per min. One-half of the incident energy on the sludge surface was
expended as latent heat of vaporisation. When drainage or infiltration of
digested sludge water into sand contributed to the sludge dewatering process,
the evaporation rate from the sludge surface as a result of radiative heat
transfer was depressed by 22 percent.
It was found that digested sludge dried at a constant rate until its
moisture content approached 75 to 90 and 66 to 84 percent by convective and
radiative heat transfer respectively. Thus, at moisture contents of 70 to 90
percent, the rate of evaporation decreases and is referred to as a critical
moisture content for sludge dewatering.
Factors determining the dewatering rate of digested sludge on soils were
investigated under laboratory and field conditions. Soil columns of Blount
silt loam and Plainfield sand were used in laboratory sludge dewatering
studies. Metal infiltration rings were used for field studies.
Nitrate concentrations, electrical conductivity, pH, and Eh values of
effluent and soil water samples were determined. Effluent from soil columns
and soil solution samples were collected throughout the period in which the
factors influencing the dewatering of sludge on soils was investigated.
It was found that when sludge is first applied on soils, dewatering of the
sludge is fairly constant and the rate depends on infiltration of water into
soils and water losses by evaporation. When the water content of sludge has
been reduced to about 80 percent by weight, further drying of the sludge is
by evaporation alone. Under laboratory conditions, evaporative losses of
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water from digested sludge were not detected when the moisture content of
sludge was reduced to about 8 to 10 percent of the dry weight. On Blount
silt loam soil, after the sludge moisture content was reduced to about 80
percent, the rate of drying of the sludge was less than the rate at which
water was being evaporated from the surface of soil columns under laboratory
conditions. Apparently, water which first infiltrated the soil surface was
later transmitted back to the sludge solids on the soil surface to replace
evaporative losses of water.
Initially, the infiltration rate of sludge liquid into sand is greater
than into silt loam soils. After a few days of successive applications of
sludge in the absence of complete drying, the rate varies between .06 and
.006 cm/hr regardless of soil type. It appears that after a period of time,
the infiltration rate is determined by the sludge cake and not by the soil
surface. The soils are unsaturated with respect to moisture and their capa-
city to transmit moisture is always greater than the infiltration rate
determined or controlled by the sludge cake.
The rate of infiltration of sludge liquid depends on the initial soil
moisture content and solids content of the sludge. The higher the soil
moisture and sludge solids contents, the lower is the rate of infiltration.
However, antecedent moisture conditions affect the rate of sludge infiltra-
tion less on sandy than on fine textured soils.
When successive sludge applications are made at time intervals such that
the sludge cake is not allowed to dry, infiltration rates decrease to very low
levels. But, if the sludge cake is allowed to dry, the initial infiltration
capacity is recovered.
The changes in soil pH and redox potentials were small following various
rates and frequencies of sludge applications.
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Nitrate nitrogen concentrations continued to increase in the soil with
successive sludge applications both in laboratory and field studies. Soil
solution nitrate concentrations ranged between 100 and 300 ppm where a total
of 50 cm of sludge was applied in 70 days during field studies.
From nitrate concentrations and redox potential measurements, it appears
that anaerobic conditions were seldom, if ever, produced in the soil by
exceedingly high sludge loading rates.
Soil conductivity values were increased from an average value of about 1
millimho where only water applications were made to about 2.5 millimhos where
a total of 50 cm of sludge was applied in 70 days. It appears from limited
data that salts will be leached to deeper soil depths in a humid region. The
salt buildup in the surface of a soil like Blount silt loam with continuous
periodic sludge applications will not likely exceed that which was found with
the total 50 cm application.
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GREENHOUSE STUDIES
Greenhouse Studies on Nutrient Uptake and
Growth of Corn on Sludge-Treated Soils
These investigations were carried out by J. B. Cropper* under the direc-
tion of Dr. L. F. Welch** in partial fulfillment of the M.S. degree. The
following is from the summary of Mr. Cropper's thesis (4).
Four studies were conducted to determine what effect the sludge and its
constituents might have on the germination and growth of corn and the soils
upon which the corn was growing. The first experiment sought to determine
what effects heavy metals contained in sludge would have on corn growth if
they were allowed to build up in the soil over a period of several years.
Pb, Cu, Or, Zn, and Ni were added as chemical salts in amounts that would be
equivalent to those concentrations that would theoretically build up in a
soil after 6 acre-inch additions of sludge had been added for 0, 5, 10, 15,
and 20 years. The second experiment was a study on the effects of leaching
two soils, a sandy soil and a silt loam, with sludge. The third experiment
was set up to observe the effects of heavy applications of dried digested
sludge and lime additions had on nutrient uptake and especially on heavy metal
uptake. The fourth experiment was a sludge irrigation experiment which sought
to find out which weekly rate would be best. It was also designed to find out
if extra nitrogen, phosphorus, or potassium was needed. It also included a
germination study. Three types of sludge were compared on their effect on
germination. These three types were: regular digested, fermented digested,
and boiled digested.
* Former Research Assistant, Department of Agronomy, University of Illinois.
** Professor of Soil Fertility, Department of Agronomy, University of Illinois
of Urbana-Champaign.
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The following points are of major interest when utilizing sludge for
irrigation or other agricultural purposes to be cropped with corn and possibly
other crops.
1. Sludge will provide adequate amounts of nitrogen, phosphorus, and
potassium at the rate of 0.5 acre-inch per week during the growing season.
2. Sludge at the rate of 6 inches annually perhaps adds too much nitro-
gen.
3. Application of liquid digested sludge immediately after planting
should probably be avoided unless not more than 0.5 acre-inches is applied.
4. Zinc and copper concentrations in corn are increased substantially
by sludge fertilization. These metals could build up to toxic levels in the
soils if sludge is applied at high rates for many years.
5. Sludge does not seem to have much effect of soil pH on a short-term
basis.
6. Cation exchange capacity and buffering capacity of sandy soils is
increased considerably by sludge applications.
7. Liming of sludge treated acid soils would be desirable for many
reasons. It would tend to keep the heavy metals less soluble. Manganese, in
particular, would be reoxidized by the increased pH of the soil so that it
would not leach from the upper profile of the soil. Lime would promote more
rapid nitrification of the tremendous amounts of ammonium nitrogen present in
the soils after sludge additions.
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SOUTH FARM LYSIMETER RESEARCH
Field study of the efects of disposal of digested sewage sludge
(hereafter referred to as sludge) on land was begun in the spring of 1967.
Existing lysimeters, each three feet in diameter and four feet deep were
utilized. The lysimeter surfaces were at the same elevation as the sur-
rounding soil, and underground pipes allowed collection of drain water.
Eight soil types were represented (Brooklyn, Cisne, Cowden, Elliott, Say-
brook, Herrick, Muscatine, and Tama) and replicated three times. All soils
were silt loams with differences in internal drainage and permeability.
Sludge used on the lysimeters was obtained from the Calumet Treatment
Plant of the Metropolitan Sanitary District of Greater Chicago. The sludge
was applied as received from the digesters, i.e. as a liquid with ca. 3%
solids. Table 1 lists the nutrient and metal concentrations found in sludge.
Sludge treatments were chosen on an estimation of the maximum liquid
volume which could be accommodated. In 1967, rates of one inch and one-half
inch per eight days were chosen, and totals of ten and five inches were
realized. In 1968 and 1969, rates of one inch and one-half inch per week
were adopted, and the maximum totals were ten and seven inches, respectively.
Commercial fertilizer, at the rate of 200 Ib/A nitrogen, 100 Ib/A phosphorus,
and 100 Ib/A potassium, was used on the control plots in 1968 and 1969. Where
necessary, plots were irrigated with water to equal the liquid volume of the
maximum sludge rate.
Yields
Soybeans were planted in 1967. In 1968, grain sorghum and Reed canary
grass were grown, and in 1969 corn and Reed canary grass were grown.
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Whole soybean plants were harvested when the lower leaves began to
yellow with maturity. There appeared to be a toxic condition, especially
in the control lysimeters. The toxicity probably arose from a high Zn
content in the soil (see Table 15) that apparently resulted from the gal-
vanized construction of the lysimeters.
The yield data for soybeans are shown in Table 3. Sludge-treated plots
produced significantly better grain and total plant yields than did the con-
trols. Sludge additions ameliorated the toxic condition that was apparent
in the controls.
Reed canary grass yields are listed in Table 4. Sludge treated plots
yielded significantly more than control plants from the first cutting in each
year. Second cutting yields from sludge-treated and control plots were simi-
lar in both years. Better physical condition of the soil and/or availability
of residual nutrients in sludge-treated plots probably accounted for the
higher first cutting yields on sludge-treated plots.
Means for sorghum grain yields were 430.4, 284.9, and 354.8 g for the
maximum, 1/2 maximum, and control, respectively. Although the maximum sludge
application produced the highest yield, the differences were not statistically
significant at the 5% level (see Table 5). Sludge-treated plants matured a
few days earlier than control plants.
Average com yields (Table 5) were 110.61, 260.93 and 349.18 g per lysi-
meter for maximum, 1/2 maximum, and control rates, respectively. Unfortunately,
leaf blight deleteriously affected the yield. Yields from sludge-treated
plots were more severely reduced because the disease affected those plants
sooner than the controls. Leaf samples for chemical analysis were collected
before the corn disease symptoms appeared.
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Table 3. Soybean yield means in grams dry weight from South Farm lysimeters,
1967.
Treatment
Maximum sludge
1/2 Maximum sludge
Control
Whole Plant
288.8**
253.9**
78.2
Grain
88.3
83.0
21*. 1*
Dry vrb/plant
14.4**
12.0**
4.3
Significantly different from the control at the 1% level
Table 4. Reed canary grass yield means; South Farm lysimeters
Treatment
Maximum sludge
1/2 Maximum sludge
Control
7/19/68
190.3**
132.5**
73.5
Dry weight in grams
9/9/68 5/26/69
165.5 239.1
140.1 231.6
143.2 78.3
9/18/69
106.3
91.4
108.8
Significantly different from the control at 1% level
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Table 5. Sorghum (1968) and corn (1969) grain yield means; South Farm
lysimeters
Treatment
Maximum sludge
1/2 Maximum sludge
Control
Sorghum
dry wt g
1*0.1*
281*. 9
35^.8
Corn
5$ moisture g
180.61
260.93
3^9.18
Table 6. Mean nitrogen content of soybean plants in percent dry weight
Treatment Leaves Grain
Maximum sludge k.k5 k.Qj
1/2 Maximum sludge 3.75 ^.6l
Control 3.1*2 3.91*
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Plant Chemistry
Addition of one inch of sludge to an acre provides about 330 Ibs. of
nitrogen approximately half of which is in the ammonium form. Therefore,
during each of the first two seasons, the equivalent of over 3,000 Ibs. of
nitrogen per acre was added. Plants were analyzed for total nitrogen to
determine what effect this high rate of application had.
Nitrogen content for soybean leaves and grain are presented in Table 6.
Leaf values were 3.42, 3.75, and 4.45% for the three rates in ascending order.
Nitrogen contents of the grain were 3.94, 4.61, and 4.87% with increasing
application rates. The leaf nitrogen increased as expected with increasing
applications of nitrogen from the sludge.
Total nitrogen content means for the two cuttings of Reed canary grass
in 1968 are listed in Table 7. For the first cutting, nitrogen values were
4.10, 4.21, and 4.17% for the three increasing application rates. Concentra-
tions for the second cutting were 2.84, 3.57, and 3.91% with increasing
application rates. The relatively large reduction in nitrogen in the control
sample (second cutting) probably occurred as only one fertilizer application
was made in the spring.
Concentrations of total nitrogen in grain sorghum leaves are listed in
Table 7. They are 1.48, 2.37, and 2.49% with increasing application rates.
The nitrogen contents of the crops even at the abnormally high fertility
levels employed with sludge irrigation were not very different from those
published and accumulated in a state-wide plant nutrient survey (5). Thus,
it appears that these very high nitrogen rates from sludge had no deleterious
effect on plant nitrogen composition.
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20
Table 7. Total nitrogen content means for Reed canary grass and sorghum
leaves from South Farm lysimeters
Treatment
Maximum sludge
1/2 Maximum sludge
Control
R. C. G.
Percent dry weight Sorghum
7/19/68 9/9/68 1968
k.27 3.91 2.^9**
*N21 3.57 2.37**
U.10 2.81+ i.U8
'X* 'X* j
Significantly different from the control at the 1% level
Table 8. Micronutrient concentration means for soybean plants from the South
Farm lysimeters.
Treatment ~
Leaves
Maximum sludge 29
1/2 Maximum sludge 29
Control 32
Grain
Maximum sludge 1*5
1/2 Maximum sludge 1*3
Control 1*7
Concentration
Mn
11*5**
129**
62
38
58
1*2
in ppm
Ni
7.2
7.2
5.2
7.6
7.3
11.0
Zn
1186
1251
827
276
295
271
y y
Significantly different from the control at the 1% level
-------
21
Reference to Table 1 will show that digested sludge has a rather high
complement of heavy metals -- Cu, Zn, and Mn are essential in small quanti-
ties to plants whereas Cd, Pb, and Cr are nonessential. Heavy metals are
usually toxic to plants at relatively low available soil concentrations.
Because they are polyvalent, they are held rather tightly by the soil col-
loids Which reduces their availability to plants. In the case of sludge,
they are present as hydroxide (6) or other precipitated form in the solid
phase. As long as the soil pH remains neutral, or above, heavy metals should
not become very available to plants (1) from a sludge source. Potential
hazard of toxicity from extended application of sludge to cropped land is a
distinct possibility (7).
Soybeans. Cu, Mn, Ni, and Zn concentrations found in soybeans are
listed in Table 8. Pb and Cr were not detected. Values for Cu were slightly
higher, 43-47 ppm in the grain, than in the leaves, 29-32 ppm. Concentra-
tions measured in this study were rather high, but differences due to
sludge treatment were not sifnificant.
Mn concentrations in leaves were significantly different for sludge
treatments while Mn levels in the grain were not. It is easier to influence
the leaf composition than it is the grain. Concentrations ranged from 62-145
ppm for the control and maximum rate respectively.
Zn concentrations in leaves and grain of sludge-treated and control
plants were unusually high. Since the control plants were also high in Zn,
it was obvious that much of the Zn found in the plant samples came from the
soil and not the sludge. Zn levels in all plants, including controls, were
sufficiently high to be considered in the toxic range.
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22
Sludge treated plants contained higher concentrations of Zn than the
controls, yet the treated plants showed less toxicity. These results support
the theory that Zn and phosphorus interact (4) and since the sludge added
the equivalent of several hundred pounds per acre phosphorus, it may have
restored a more normal ratio between the elements, thereby reducing the
toxicity symptoms. Differences in Zn content of the grain were not signifi-
cant relative to treatment.
Ni concentrations in leaves and grain were approximately the same, and
differences due to sludge treatment were not significant.
Reed canary grass. Mn, Mg, Cu, and Zn concentrations in Reed canary
grass leaves for the cuttings are presented in Tables 9 and 10. Cd and Cr
were not detected. Mn concentrations in the first and second cuttings in-
creased with increasing sludge rates and all sludge treatments were higher
than the controls.
Mg concentrations in general do not significantly reflect treatment.
Grain sorghum. Concentrations of micronutrients in sorghum leaves and
grain are shown in Table 11. Ca, Mg, and Cu contents did not vary signifi-
cantly with sludge treatment. Like soybeans, micronutrient content of the
grain was much lower than that of the leaves. This phenomenon could be use-
ful if sludge application induces higher than normal heavy metal uptake,
particularly where the edible plant part is the grain.
Zn and Mn concentrations in leaves and grain and Fe concentrations in
grain showed highly significant increases with sludge application. Ni, Cr,
and Pb were not detected in leaves or grain.
Corn. Table 12 lists the micronutrient concentrations found in corn
leaves. Only Mn concentration showed significant response to sludge treatment.
Pb was detectable in a few samples, but no Cr or Cd was detected in any.
-------
23
Table 9. Micronutrient content means of Reed canary grass from South Farm
lysimeters, 1968.
Mn Mg Cu Zn
Treatment 7/19 9/9 7/19 9/9 7/19 9/9 7/19 9/9
ppm ppm % % ppm ppm ppm ppm
Maximum sludge 10^** 15U .226 .198 33* 32 %5 823**
1/2 Maximum sludge k9** 96 .223 .350 25* to 895 976**
Control 31 30 .292 .300 18 to 1168 635
* -/
.^Significantly different from the control at the 5% level
Significantly different from the control at the 1% level
-------
Table 10. Micronutrient content means for Reed canary grass from South Farm
lysimeters, 1969*
Treatment
Maximum sludge
1/2 Maximum sludge
Control
Maximum sludge
1/2 Maximum sludge
Control
Ca Mg
.259 -191*
.229 .196
.197 .112
.k!2
.386
.17*
Cu Fe Ni
ppm PPm ppm
5/26/69
17
12
9
9/18/69
5.0
5.1
7.8
156** 5.1
11*2** 1*.3
125 k.O
76 k.6
71 3.0
63 1A
Zn
ppm
595
585
550
1225
1070
1030
Mn
ppm
111***
62**
32**
193
9k
36
Significantly different from the control at the 1% level
-------
25
Table 11. Micronutrient content means for sorghum leaves and grain from South
Farm lysimeters, 1968.
Treatment
Maximum sludge
1/2 Maximum sludge
Control
Maximum sludge
1/2 Maximum sludge
Control
Ca
ppm
-
-
62
75
67
**
Significantly different from
Mg Cu
% ppm
Leaves
.klk 32
.422 4l
.220 38
Grain
.162 3.25
.161 3.4-4
.137 2.86
the control at
Fe
ppm
-
-
56**
57**
32
the 1% level.
Table 12. Micronutrient content means for corn leaves from
lysimeters, 19^9 «
Treatment
Maximum sludge
1/2 Masimum sludge
Control
Ca
%
0.761
0.797
0.755
Mg Cu
% ppm
0.593 12
0.869 13
0.674 17
Fe
ppm
215
147
181
Zn
ppm
717**
589**
252
60**
58**
30
South
Ni
ppm
1.0
1.1
1.1
Mn
ppm
173**
76**
16
14**
11**
5.8
Farm
Zn
ppm
1120
1031
881
Mn
ppm
153**
45**
28
Significantly different from the control at the 1% level.
-------
26
The sludge-treated plants generally exhibited enhanced Zn, Mn, and Fe
uptake. This enhanced uptake may be partly a function of addition of the
elements in sludge, but there is good evidence that some of it may be an
indirect effect of sludge addition. In no case has there been evidence of
toxicities resulting from sludge addition in two years of this lysimeter
study.
Soils
Soil test values for pH, available P and K of the soil from the lysimeter
plots are shown in Table 13. The 1967 values preceded planting and sludge
application. Soil pH, available phosphorus and potassium increased with
sludge treatment.
Concentrations of organic carbon are given in Table 14. Organic C
content increased with sludge application rates while the controls remained
relatively constant.
Heavy metal concentrations, as determined by 0.1 N HCl (8) are given in
Table 15. All of the heavy metals increased relative to the controls in
sludge amended plots.
Leachates
Nitrate-N analyses of leachates (drain water) from the lysimeters are
given in Figures 1 and 2. Concentrations from sludge-treated plots were
significantly higher than those in the controls.
First leachates usually collected in November contained the highest ni-
trate concentrations, while the lowest concentrations occurred at the end of
the collection period. Essentially no leachate was produced during the
summer months. Nitrate-N concentrations in the control plots were uniformly
low for all periods of the year.
-------
27
Table 13. Means for pH, P.. (available phosphorus), and potassium from South
Farm lysimeter soils.
Treatment
Maximum sludge
1/2 Maximum sludge
Control
Maximum sludge
1/2 Maximum sludge
Control
Maximum sludge
1/2 Maximum sludge
Control
PH
1967
5.7
5.8
5.8
1968
5.8
5.6
5.7
1969
6.2*
5.9*
5.6
PX Ib/A.
176
187
182
1*50**
1*06**
183
226**
198**
1M
K Ib/A.
357
1M
390
61***
551**
299
718**
507**
516
•**
^Significantly different from the control at the 1% level.
Significantly different from the control at the 5$ level.
-------
28
Table lk. Organic carbon content means for South Farm lysimeter soils, per-
cent dry weight.
Treatment
Maximum sludge
1/2 Masimum sludge
Control
Pre-treated
1.90
1.98
1.91
8/21/6?
2.51**
2.19**
1.90
10/20/6?
3. hi**
2.95**
1.78
5/12/68
5.98**
3.37**
1.82
y y
Significantly different from the control at the 1% level.
Table 15. Heavy metal content means of South Farm lysimeter soils sampled
5/2/69.
Treatment
Maximum sludge
1/2 Maximum sludge
Control
Cd
36
18
n.d.
Parts
Cr Cu
^5 352
27 138
n.d. 17
per Million
Mn
306
279
122
Ni
18
9-1
0.75
Pb
209
162
12
Zn
2175
1205
^59
-------
29
N- ON Ifldd
-------
449 PPM
ONE INCH/WEEK SLUDGE APPLICATION
1/2 INCH/WEEK SLUDGE APPLI-
CATION
D 1968 J 1969 F
DATE
M
M
FIGURE 2. NITRATE-N CONCENTRATIONS IN SOUTH FARM LEACHATE
11/68 - 5/69
-------
31
Figures 3 and 4 show the accumulated losses of nitrogen as nitrate in
leachate. Total nitrogen losses reflected the sludge treatment.
-------
32
V)
CE
O
O
O
10.0
5.0
.0
0.5
N
INCH/WK. SLUDGE
CHECK
30.98 g
1/2 INCH/WK. SLUDGE
0.74 g
D 1968 J 1969 F M
DATE
FIGURE 3. TOTAL LOSS OF NITRATE-NITROGEN IN LEACHATE 11/68-5/69
-------
10.0
o
o
o
1.0
33
21.41 g
I INCH/8 DAYS SLUDGE —
— 1/2 INCH/8 DAYS SLUDGE
2.IOg
/---CONTROL
N
1967 J 1968 F
M
DATE
FIGURE 4. TOTAL LOSS OF NITRATE-NITROGEN LEACHATE 11/67-7/68
-------
34
INSTRUMENTED PLOTS AT THE NORTHEAST AGRONOMY RESEARCH CENTER
The Field Research Facility
Plans and specifications for the field research facility were prepared
and submitted with the requisition to the University Purchasing Division on
June 6, 1967. Construction of the instrument house was completed on Septem-
ber 15, 1967 and the lysimeters were completed on June 18, 1968.
The field research facility was constructed on a small isolated water-
shed, where the original soil type was Blount silt loam, underlain with
glacial till, of very low permeability, from about 30 inches below the soil
surface to a depth of about 40 feet. An overall view of the field research
facility is presented in Figure 5. The facility consists of 44 plots, each
50 feet long and 10 feet wide. Half of the total 44 plots are in each of 2
blocks: one block on the north and one block on the south side of the
instrument house. Each block contains 12 plots of the original Blount silt
loam, five plots of simulated Elliott silt loam, and five plots of simulated
Plainfield sand. Since the Elliott silt loam soil is a prairie correlate of
the forested Blount silt loam, the simulation of a prairie soil was made by
removing the Blount silt loam surface to a depth of one foot and replacing
it with the surface of Elliott silt loam. Plainfield sand was simulated by
excavating all of the original material within the boundaries of a plot to
a depth of 5 feet and then filling the pit with Plainfield sand.
A trenching machine was used to excavate a trench around the perimeter
of each plot to a depth of 6 feet. After a single line of 4-inch diameter
clay tile had been installed at a bottom depth of 34 inches through the
longitudinal center of each of the Blount and Elliott silt loam plots, a
continuous curtain of nylon reinforced 8 mil black plastic film was
-------
35
oo: 13
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-------
36
suspended from 8 inches below the soil surface to a depth of 6 feet in the
trench surrounding each plot, with the ends overlapped a minimum of 4 feet.
With the moisture barrier secured by spikes to the inside wall, the trench
was backfilled with the soil removed during excavation. Construction of the
sand plots was somewhat different in that the line of clay tile was installed
at a depth of 5 feet and the walls lined with the plastic moisture barrier
before the pit was filled to ground level with Flainfield sand.
To convey drainage water, a 4-inch diameter rigid plastic drain tube
was extended from each plot attached to the end of the 4-inch diameter clay
tile line nearest the instrument house to within 2 feet of the basement and
30 inches above the basement floor of the instrument house. The plastic
tube was attached to the clay tile by an adapter just inside of the plastic
moisture barrier. A mastic material was used to achieve a water proof seal
where the plastic tube passed through the moisture barrier.
A second 4-inch PVC tube to convey runoff water was extended from 2 feet
inside and 66 inches above the basement floor to within 6 inches of the
moisture barrier at each of the plot center end nearest the instrument house.
The end of the PVC tube at the end of a plot was located 18 inches below the
soil surface and connected to a 90 degree elbow positioned in an upward
direction to receive the thimble of the runoff water collection trough.
Each of the 88 plastic tubes for drainage and surface runoff water
conveyance was placed on the maximum uniform grade obtainable from a plot
to the basement of the instrument house. Grade was never less than 0.5 per-
cent for tubes serving any plot.
The runoff water collection troughs were of a design similar to those
used in soil erosion studies, except that they were fabricated from fiber
glass. Fiber glass was chosen as the construction material to avoid the
-------
37
introduction of heavy metals in the runoff water and soils. For the same
reason, fiber glass strips 10 inches high were used to completely enclose
the plots along and above the moisture barrier discussed above. The fiber
glass strips insure the collection at the down slope end of all the runoff
water from a plot while excluding all foreign water.
All lysimeter plots, side borders (10 feet wide), and end borders
(20 feet wide) slope toward the instrument house. Thus, runoff water flows
toward the instrument house from both the north and south blocks of lysimeter
plots.
The instrument house was constructed in a natural depression of the
slightly greater than 2 acre watershed. The 54.75 ft by 12 ft by 8 ft eave-
height frame building was constructed on a concrete first floor over a poured
steel reinforced 8-inch thick walled basement, which was 9.5 ft high above
the footings. Ten 4-inch diameter bell and spigot floor drains were installed
in the basement floor to conduct unwanted water discharged from the plot
drainage tubes to a 8-inch diameter tile installed below the center of the
basement floor.
Heating was provided by 2 wall mounted thermostatically controlled 220
volt electric heaters at each end of the first floor of the instrument house.
One end of the first floor of the building was partitioned, to provide a
totally air-conditioned room to protect instrumentation circuitry from exces-
sive variations of temperature and humidity.
The 8-inch diameter clay tile line used to drain excess water from inside
the basement of the instrument house and basement footing tiles was also con-
nected to a surface inlet located in the natural drainage way of the small
water shed and 150 feet west of the instrument house. Behind the surface
-------
38
inlet a small earthen dam was constructed to insure the capture of all run-
off water from areas outside of the lysimeter plots. Thus, all water from
the research area is disposed of through the 8-inch diameter tile line that
conducts water through a 1500 gallon septic tank and finally to a sand and
gravel filter field. All water from the research area is filtered through
30 inches of sand and gravel before it is discharged to a stream that flows
intermittently.
To provide water for the instrument house and for irrigation of lysimeter
check or control plots, a well was drilled to a depth of 200 feet. However,
since a sustained flow of only 6 gallons of water per minute was obtainable
from the well, two used 10,000 gallon capacity railroad tank car containers
were buried near the well to store water for irrigation. Two other used,
plastic-lined 8,000 gallon capacity railroad tank car containers were buried
end to end with the water tanks to provide storage for digested sludge. The
two water tanks were connected with 3-inch diameter metal pipe and a 60 gal-
long per minute capacity pump was mounted on the end of one water tank. One
2 stage vertical turbine pump with a capacity of 400 gallons per minute was
mounted on the ends of each of the separate sludge tanks. Both the water and
sludge pumps develop heads of about 180 feet. All pumps, motors, and
exposed plumbing were enclosed in an insulated, propane heated pump house.
Three-inch diameter metal pipe was used for all plumbing inside the pump
house. By the use of check and gate valves, the plumbing from the pumps was
installed in such a manner that the main irrigation line could be supplied
with either water or sludge. Also, sludge could be circulated in the same
storage tank pumped from one sludge storage tank to the other for mixing.
Three-inch diameter PVC pipe was used for the main irrigation line
-------
39
which was installed at a minimum depth of 18 inches below the soil surface.
As may be seen from figure 5, the main irrigation line was extended from the
pump house through the east-west center border of the north block of plots,
to the west side of the instrument house and then returned to the pump house
through the center east-west border of the south block of plots. The irri-
gation system was so designed that a large return flow of sludge could be
maintainted to keep solids in suspension in the storage tank and prevent
settling of solids in the irrigation pipe. It may also be noted from figure
1 that a "T" joint was installed in the main irrigation line west of the
instrument house by which means the line was extended to the surface inlet
discussed above. The main irrigation pipeline was laid on a uniform grade
of approximately 0.5 percent from 20 feet west of the pump house to the sur-
face inlet so that the line could drain when the gate valve at the surface
inlet was opened. The plumbing inside the pump house is so arranged that
after irrigation of plots receiving sludge treatments, the gate valve at
the surface inlet may be opened and the north and south portions of the irri-
gation line may be alternately flushed with water. The irrigation line must
be flushed with water'each time before irrigation of check plots with water.
Risers were installed in the main irrigation line through the north and
south block of plots so that one riser, by means of a valve and key, could
supply either water or sludge to irrigate any one of four plots.
Although irrigation equipment is commercially available for field appli-
cations of digested sludge, equipment for making uniform applications on small
research plots could not be obtained. Thus, a self-propelled irrigation
machine for uniformly applying digested sludge on the 10 x 50 foot plots was
designed and constructed specifically for the research project. Two-inch
-------
40
diameter flexible tubing is used to convey sludge or water from the risers
to the irrigation machine.
To collect discrete samples on a preset volume proportional basis of
runoff and drainage water from the field-plot size lysimeters, an electrical-
ly controlled sampling system was designed, constructed, and put into
operation. The system is used to measure rate and total flow of both runoff
and drainage water from each of the 44 lysimeters and to collect 400 ml
samples after selected volumes of flow have occurred. Sampling may be varied
for collecting a sample from 5.0 to as little as 2.4 percent of the total flow.
It may be seen from the block diagram, figure 6, that the system con-
sists of the following five major components: 1) tipping bucket, 2) sample
collector meachanism, 3) electrical circuits for counting and control,
4) event recorders and, 5) automatic turn-on and turn-off system. Except for
some common circuit elements, each major component was duplicated eighty-
eight times to provide complete instrumentation for the forty-four lysimeters.
All of the instrumentation is located on the ground floor of the instrument
house except the tipping bucket and sample collectors which are positioned
below the end of the four inch plastic pipes used to convey runoff and
drainage water from the lysimeters to the basement of the instrument house.
To insure against the loss of water samples and data during a storm
period in which an electric line power outage might occur, a 120 volt, 2500
watt auxiliary power plant with automatic transfer panel was installed to
provide power for the above described sampling and data collection equipment.
Since the irrigation system, data, and water sampling equipment could
not be installed until all other construction was completed, sludge was not
applied on the lysimeter plots in 1968, although the north block of plots
-------
41
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42
was planted in June with soybeans and the south block with corn. Installa-
tion of equipment was completed in December 1968 and snow melt in January
1969 produced considerable runoff and provided an opportunity to check the
equipment. A few minor modifications were made on the equipment in February
1969, after which the plots were ready for sludge applications. However,
from April 1, 1969 through June 15, 1969, slightly more than 26 inches of
rainfall were received at the research site. Although the plots were
planted with soybeans and corn, the first application of sludge was not
made until the latter part of June 1969. The exceptionally heavy rainfall
period did provide several hundred water samples from which base data
regarding fecal coliform organisms and the chemical status of drainage and
runoff water could be obtained. But sludge applications were delayed too
long by wet conditions to expect a treatment response by the crops. With
the last irrigation of the lysimeter plots in December 1969, a total of 4
inches of sludge had been applied to the maximum sludge treated plots. For
the most part, individual irrigation application rates have been less than
0.2 inches to prevent runoff of the sludge. When conditions are such that
evaporation is high, a 0.2 inch application of sludge can be applied every
two days and this does not seem to vary significantly with soil type.
-------
43
Supplemental Field Experiments
At the N. E. Agronomy Research Center, digested sludge was applied by
furrow irrigation at weekly intervals on Blount silt loam planted to corn
and kenaf in 1968 and 1969. Corn was planted on replicated plots where
alfalfa had grown for the two years previous to plowing. No inorganic
fertilizer was applied in 1968, but 6 digested sludge applications were
made between July 18 and August 28. Another sludge application was made
on the plots in the spring of 1969 and a basic fertilizer application to
supply 200 Ibs per acre of K£0 on all plots before they were again planted
to corn. In 1969, all check plots were treated with inorganic fertilizer
supplying 240 Ibs of nitrogen and 240 Ibs of ?2®5 Per acre. Eight digested
sludge applications were made in 1969 between the latter part of June and
the first week of September. Average corn yields by year and application
rate of digested sludge are presented in Table 16.
In the absence of nitrogen and phosphorus fertilizer applications on the
check plots in 1968, a considerable increase in yield was realized for even
the minimum sludge application. However, in 1969 when an exceedingly high
application of nitrogen, phosphorus and potassium was applied on the check
plots, the yield response to digested sludge application was not very great
and indicates that it compares favorably with high rates of inorganic fertil-
izers. The corn yields in 1969 are probably the highest ever obtained on
Blount silt loam.
The schedule for application of digested sludge on Blount silt loam plots
where kenaf was grown in 1968 and 1969 was almost the same as discussed for
corn. Also, inorganic fertilizer applications on kenaf plots were the same
as those discussed for corn.
-------
44
Average yields of three varieties of kenaf in 1968 and 1969 are pre-
sented in Table 17.
It appears that the application of two inches per year of digested sludge
would supply adequate fertility for the kenaf varieties tested in 1968 and
1969.
To evaluate the availability of phosphorus and the response to the
additional moisture supplied by sludge applications, plots of soybeans were
replicated on Blount silt loam in 1969. A basic application of 200 Ibs/acre
of ICjO was made over all plots before planting.
The yield response of soybeans to phosphorus, sludge and water are pre-
sented in Table 18.
From treatments 1 and 5 it appears that in the absence of sludge the
additional phosphorus increased yields from 3.7 to 8.4 bushels per acre
depending on the moisture supply in August. Where soybeans were irrigated
with sludge the additional phosphorus did not appear to increase yields. The
water applications alone increased average yields by slightly more than 9.4
bushels/acre without phosphorus fertilization and 14.' bushels/acre where
240 Ibs/acre of $2^5 was applied. Comparing the treatment of 8 inches of
sludge to 8 inches of water applied during the growing season in the absence
of additional phosphorus fertilizer an increase of 6.6 bushels per acre was
obtained with digested sludge irrigation. However, for the same comparison
between sludge and water where an additional 240 Ibs of ?2®5 was supplied,
there was little difference in yields. From this one-year study it may be
concluded that the phosphorus supplied in sludge was readily available to soy-
beans, but the greater part of the increase in yield with sludge application
was the result of the additional water supplied in August. The additional
water and phosphorus fertility applied by 8 one-inch applications of sludge
resulted in an increase of 16 bushels per acre or a 47 percent yield increase.
-------
Table 16. Corn yields and didgested sludge applications on Blount silt loam
on N. E. Illinois Agronomy Research Center, 1968 and
Inches of sludge per
application
0
lA
1/2
1
Average corn yields
1968
66.3
96.2
11^.2
111.9
in bushels per acre
1969
ite.8
11+9.0
150.2
150.6
Table 17. Kenaf yields in tons per acre (adjusted to 20$ moisture).
Sludge Treatment*
0
2
U
8
1968
Everglad 71
2.1
3.6
3.7
3.7
Varieties
Cuba 2032
^.99
H.55
if. 81
5.26
1969
Guatemala k
^.55
5.12
5.21
5.38
*0 - Received only basic application of 200 Ibs/A of KJD in 1960 but
fertilized with 2^0-2^0-200 Ibs/acre in 1969.
2 - Sludge, 1.75 inches 1968 and 2 inches 1969.
k - Sludge, 3.5 inches 1968 and U inches 1969.
8 - Sludge, 7 inches 1968 and 8 inches 1969.
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Table 18. Yield response of soybeans to phosphorus, sludge and water
treatments.
Average yield bu/acre
Treatments *
1
2
3
k
5
* treatment 1 -
treatment 2 =
treatment 3 =
treatment k «
Phosphorus **
37.7
]i)i_ £}
1^7 Q
52!l
51.8
0 sludge or water application
i inch of sludge, 8 times from April
\ inch of sludge, 8 times from April
1 inch of sludge, 8 times from April
No. Phosphorus
3^.0
^5.0
U8.2
50.0
through Sept. 17, 1969
through Sept. 17, 1969
through Sept. 17, 1969
y y
treatment 5=1 inch of water, 8 times from April through Sept. 17,
Ibs/acre POj. applied to one-half of each plot in October 1968
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47
HYGIENIC ASPECTS OF LIQUID DIGESTED SLUDGE DISPOSAL ON CROPPED LAND
Fecal Coliforms in Liquid Digested Sludge
In this section, data obtained with fecal coliform organisms and with
Escherichia coli are presented. The reader who would like to find general
considerations on the hygienic aspects of sludge disposal on land is referred
to other publications (9, 10).
Microbiological purification of polluted waters by percolation through
artificial filters or soils is known to be an effective method of water
treatment. Insofar as inferences can be made from traditions and experiences,
one may expect the percolated waters from a biofilter four to five feet thick
to be free of pathogens. In the present case, the challenge is at the soil-
atmosphere interface, where digested sludge will cover acres, accessible to
runoff waters, insects, birds and animals. The danger of infection from
these fields will, to a great extent, be controlled by the persistence of
pathogens on this surface layer.
For routine analyses of water, soil and digested sludge samples, the
coliform group of bacteria has been taken as indicator of the degree of
microbial pollution. Since non-fecal coliforms are known to the part of the
normal soil flora, only the fecal coliforms have been considered.
The determination of fecal coliforms is rapidly and easily performed by
the membrane filter technique with incubation at 44.5°C in the M-FC medium (11).
This method (referred to as MFC) reveals the presence in the liquid digested
sludge of a large population of fecal coliforms which gradually decreases upon
removal of the digested sludge from the digester (Table 19). In contrast to
this gradual decrease, laboratory grown populations of Escherichia coli
(neotype, ATCC 11775) disappear very rapidly when added to the non-treated or
autoclaved digested sludge (Table 20). In view of this difference of behavior
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Table 19. Number of fecal coliforms per ml of impounded liquid digested
sludge.
Sludge sample Q
Total sludge k x 10 7 x 103 2 x 102
•a 1
Sludge supernatant 3 x 10-* 2 x 10 0
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Table 20. Number of fecal coliforms found per ml of digested sludge
incubated on a rotary shaker under aerobiosis.
Additions or treatment done
to the digested sludge
Sampling time (hours)
24
None
Escherichia coll added
Autoc laved and E. coli added
25
25
26
x 102
x 106
x 106
20 x 102
41 x 102
0
Table 21. Toxicity of the digested sludge toward Escherichia coli as
determined by the MFC technique.
Toxic sludge
Non-toxic sludge
Autoclaved
Liquid phase (autoclaved or
non-autoclaved)
Boiled
Dried at room temperature and re-
suspended with water
Solid phase resuspended with a 1
percent NaCl solution and auto-
claved or non-autoclaved
Aerated for a few days and autoclaved
Some fresh batches of sludge, auto-
claved
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the question is raised as to whether the organisms found in the digested
sludge by the MFC technique are truly of the fecal coliform groups. Short
of serological tagging, the IMViC test and the elevated temperature (EC)
method, as a confirmatory test from positive presumptive tubes, are the only
other two ways to identify fecal coliforras. Both techniques have indicated
the presence of fecal coliforms in the liquid digested sludge. On the basis
of the IMViC test, Fuller and Litsky have shown that the digested sludge
harbours a population of fecal coliforms, in the order of 1CP cells per
milliliter (12).
The fate of E. coli in autoclaved digested sludge was further investi-
gated. The enumeration of E. coli was performed both by the MFC technique
and on eosin methylene-blue agar pour plates (EMB method). Results obtained
from the two methods differed. Only rarely did the EMB plates indicate a
die-off of E_. coli; with the majority of the cases, the decrease in the
number of typical colonies was offset by the appearance of atypical colonies,
indicating an overall development of E. coli in the autoclaved digested
sludge.
Various treatments were performed on the digested sludge in order to
determine for the nature of its apparent toxicity toward E. coli as deter-
mined by the MFC technique (Table 21). Although the digested sludges were
always collected at the same sanitary plant (Calumet, Chicago), a few batches
turned out to be devoid of toxicity. This fact rules out many factors which
otherwise would have been considered as possible causative agents for the
toxicity: the low redox potential, the lack of oxygen, the saturation of the
sludge liquid phase with carbon dioxide, methane, and possibly the presence
of sulfides.
Reversal of the bactericidal action was achieved by the addition to the
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51
digested sludge of 5 gm/1 bacto-tryptone (Difco). At 2.5 g/1, the bacto-
tryptone had no effect. The energy and usual growth factors brought with
tryptone could not be accounted for the reversal since the addition of
lactose and/or yeast-extract (Difco) had no effect on the toxicity. Addi-
tion of DL-tryptophane and L-tyrosine, however, reduced somewhat the rate
of E_. coli disappearance although not as potently as tryptone (Difco) did.
The addition of tryptone, tryptophane, or tyrosine did not affect the pH
of the sludge, which during the incubation in contact with the air, ranged
from 7.0 to 8.9 as commanded most likely by the carbonate-bicarbonate buffer.
In relation to these facts, the disappearance of Salmonella typhosa in the
sludge has been attributed to nutritional deficiency in tryptophane (13).
Reversal of the toxicity by biochemical compounds gives much credit to
the assumption that this toxicity is biochemical in nature rather than
physical. In view of the low organic carbon content of the sludge super-
natant, these compounds ought to act at very low concentrations. Volatile
fatty acids have been held responsible for the exclusion of E. coli and
salmonellas in the rumen of bovines. However, their range of bacteriostatic
and bacteriolytic action is limited to pH values below 7.0 and to concentra-
tions above 60 u moles per ml, both conditions which are not prevalent in the
sludge. Moreover, there are evidences that the elimination of salmonellas
and IS. coli from bovine rumen cannot be accounted for by volatile fatty acids
only (14). The presence of antibiotics in the digested sludge could not be
detected by the diffusion techniques on a glucose-yeast extract agar performed
under aerobiosis and anaerobiosis with E. coli as an indicator.
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52
Fecal Coliforms in Soils Irrigated With Liquid Digested Sludge
The behavior of the sludge fecal coliforms as determined by the MFC
technique has been examined under various environmental conditions. A
gradual decrease of the fecal coliform population was observed: 1. in
the sludge cake which develops on a soil surface amended with digested
sludge (Table 22); 2. in the runoff water samples obtained from sludge-
amended fields and stored at room temperature. These results are in agree-
ment with those already obtained from various works done on the behavior
of fecal coliforms and E_. coli in digested sludge, water and soil samples
(12, 15, 16).
Routine analyses for fecal coliform densities have been performed on
the drain and runoff water samples which originated from the digested sludge
amended plots at the Northeast Agronomy Research Center. The data, so far
accumulated, indicate that the sandy soils (Plainfield) are performing as
expected, i.e. no fecal coliforms detected in drain waters. However, the
drain water from many of the Blount and Elliot plots was high in fecal
coliform counts. This was totally unexpected and may have resulted from con-
tamination through cracks in the soil of some plots. Following proper settling
and compaction of the soil, the plots should produce fecal coliform free drain
water. Monitoring of the drain waters is being continued.
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53
Table 22. Disappearance of fecal coliforms in the sludge cake covering
a soil surface.
Days after sludge No. of fecal coliforms per
application sludge cake (dry weight)
1 3,680,000
2 655,000
3 590,000
5 45,000
7 30,000
12 700
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54
Influence of Soil Moisture on Fecal Coliform Survival
Investigations conducted by Dr. R. I. Dick and assistants, Department
of Civil Engineering.
Although appreciable reduction in pathogenic organism density occurs
in anaerobic digesters, complete removal cannot be anticipated and land
disposal systems must be operated with consideration to the effect of the
organisms in the environment. Some of the factors which influence the rate
of die-off of enteric pathogens in soil include temperature, the level of
organic material in the soil, pH, and the moisture content of the soil. The
purpose of this study was to evaluate the effect of the moisture content of
Plainfield sand on survival of fecal coliforms.
The soil used in these experiments was conditioned by adding digested
sludge over a period of 9 days. Varying amounts of rain water were added
to sludge-conditioned soil samples to give moisture levels of 5, 10, 15
and 20 percent by weight. These samples, along with a sample of sludge not
mixed into soil, were then monitored for a period of about a month to observe
the rate of disappearance of the fecal coliforms originating from the sludge.
With sludge-soil mixtures of 5, 10 and 15 percent moisture, initial
sharp increases (up to 100 fold) in the fecal coliform population occurred.
No initial growth is exhibited in the sample maintained at 20 percent
moisture. This was due to the fact that at this high moisture concentration
the saturation capacity of the soil was exceeded. Essentially, anaerobic con-
ditions were maintained as evidenced by the appearance of black sulfide pre-
cipitates. Similarly, no initial growth of fecal coliforms occurred in sludge.
Following the initial period of growth, die-off of fecal coliforms in
sludge and in soil containing sludge followed first order kinetics. That is,
a constant fraction of remaining organisms died during each time interval.
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55
The only exception to this was for the 5 percent moisture condition where
the die-off rate decreased with time.
Table 23 shows the average percentage die-off of fecal coliforms after
30 days. The data show that at 5 pencent moisture the fecal coliforms were
best able to survive. This is surprising as it might be expected that a
higher rate of die-off would occur at lower moisture concentrations due to
the unavailability of moisture. Perhaps the "aeration porosity limit" (17)
at which the most favorable balance between moisture concentration and
aeration exists is near 5 percent moisture for the conditions of this study.
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56
Table 23. Survival of Fecal Coliforms in Soil and Sludge.
Die-off of Average
Moisture Content Fecal Coliforms in 30 Days
(Percent) (Percent)
5 72.5
10 99.9
15 99.6
20 96.6
Sludge 99.9
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57
CONCLUSIONS
Established Facilities
The main field research facility - the instrumented plots at the North-
east Agronomy Research Center (NEARC) which was specified in the original
proposal - has been completed. Since spring 1969, the sampling equipment has
been operational. The soils have been settling since Spring 1968. After
this period of equilibration, runoff and drain water should be more represent-
ative of undisturbed field conditions.
Crop yield responses to sludge addition have been obtained from undis-
turbed field plots with corn, soybeans and kenaf.
The lysimeter facility on the Agronomy South Farm has now had a maximum
sludge loading of 27 inches over a three year period. Soybeans, grain sorghum,
corn and Reed canary grass have been grown on them. Chemical constituents in
the crops, soils and drain water have been monitored.
Methodology and instrumentation for routine analysis of samples from the
field facilities have been established. Meteorological equipment has been
installed at the NEARC instrumented plots.
Results
1. It is easy to advance arguments either to minimize or maximize the dangers
of sludge irrigation of soils in respect to public health considerations.
Known cases of digested sludge application over agricultural fields have been
recorded for many years in several countries. Thousands of individuals in
these fields and in waste treatment plants have handled the material without
succumbing to disease of sludge origin. On the other hand, the very fact that
digested sludge harbors a large population of fecal coliforms renders it
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58
suspect as a potential vector of pathogens. Our studies have shown that the
sludge fecal coliform population decreases following application to the soil
or upon aging after removal from the digester. Lagooning of digested sludge
prior to application would serve the purpose of reducing the fecal coliform
population.
2. Nitrogen contained in digested sludge is the most immediate limiting fac-
tor to rates of application. Our data indicates that about 2 inches of sludge
would satisfy the nitrogen needs of non-leguminous crop without producing
excessive nitrate in percolated water. In the interest of higher loading
rates, reduction of the nitrogen content of sludge would be desirable.
3. Heavy metals are an ubiquitous constituent of digested sludge and they
occur usually in the solid phase. After application to soil, they remain in
the plow layer with the sludge residue. Solubilization is negligible in soil
of neutral or higher pH. Plant uptake Zn, Mn,and Fe has generally been
enhanced by sludge application. There is evidence that the uptake is not a
result of direct metal addition with the sludge, but an induced mobility of
the metals native to the soil. Plants from the South Farm lysimeters have
shown no uptake of Cd or Cr and only occasional uptake of Pb.
4. Digested sludge has been shown to be an effective source of nitrogen,
phosphorus, and micronutrients. Crop response to the water content has also
been observed.
5. Sludge residue decreases the bulk density of the soil. Grease contained
in sludge has not proven to be a problem in clogging soils. Organic carbon
has accumulated in amended soils, but has presented no observable problem.
6. The rate of infiltration of digested sludge is low regardless of soil
type. Thus, on sloping land special precautions should be taken to control
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59
the distribution of sludge applied to the soil surface. After drying,
digested sludge does not affect the Infiltration of water into the soil
surface. Shallow ponding of sludge in the furrow for even a few days does
no apparent harm to plants. Where adequate drainage exists or is induced,
salt accumulation in humid region soils is not expected to be a problem.
7. Seed germination is inhibited by fresh digested sludge.
8. Our observations indicate that properly digested sludge will produce
no offensive odors after application to soil.
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60
REFERENCES
1. Lunt, H. A. The case for sludge as a soil improver. Water
& Sewage Works, 100(8) :295-301, Aug. 1953.
2. Quon, J. E., and G. B. Ward. Convective drying of sewage
sludge. International Journal of Air and Water Pollution,
9:311-322, 1965.
3. Quon, J. E., and T. A. Tamblyn. Intensity of radiation and
rate of sludge drying. Journal of the Sanitary Engineering
Division, Proceedings of the American Society of Civil
Engineers, 91(SA2):17-31, Apr. 1965.
4. Cropper, J. B. Greenhouse studies on nutrient uptake and
growth of corn on sludge-treated soil. M.S. Thesis,
University of Illinois, Urbana, 1969. 71 p.
5. Walker, W. M., T. R. Peck, S. R. Alrich, and W. R. Oschwald.
Nutrient levels in Illinois soils. Illinois Research,
10(3):12-13, Summer 1968.
6. Jenkins, S. H., and J. S. Cooper. The solubility of heavy
metal hydroxides in water, sewage and sewage sludge--III. The
solubility of heavy metals present in digested sewage sludge.
International Journal of Air and Water Pollution, 8:695-703,
1964.
7. Rohde, G. The effects of trace elements on the exhaustion of
sewage-irrigated land. Institute of Sewage Purification
Journal. 1962:581-585.
8. Viets, F. G., Jr., and L. C. Boawn. Zinc. In Black, C. A.,
D. D. Evans, J. L. White, L. E. Ensminger, F. E. Clark, and
R. C. Dinauer, eds. Methods of soil analysis. Part 2.
Chemical and microbiological properties. Madison, Wisconsin,
American Society of Agronomy, Inc., 1965. p.1090-1101.
(Number 9 in the series Agronomy.)
9. Gordon, J. E., ed. Control of communicable diseases in man.
10th ed. New York, American Public Health Association, 1965.
282 p.
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61
10. Hanks, T. G. Solid waste/disease relationships, a literature
survey. Public Health Service Publication No. 999-UIH-6.
Washington, U.S. Government Printing Office, 1967. 179 p.
11. Geldreich, E. E., H. F. Clark, C. B. Huff, and L. C. Best.
Fecal-coliform-organism medium for the membrane filter
technique. Journal of the American Water Works Association,
57(2):208-214, Feb. 1965.
12. Fuller, J. E., and W. Litsky. Escherichia coli in digested
sludge. Sewage and Industrial Wastes, 22:853-859, 1950.
13. Langley, H. E., R. E. McKinney, and H. Campbell. Survival of
salmonella typhosa during anaerobic digestion. II. The
mechanism of survival. Sewage and Industrial Wastes,
31:23-32, 1959.
14. Brownlie, L E., and F. H. Grau. Effect of food intake on
growth and survival of salmonellas and escherichia coli in the
bovine rumen. Journal of General Microbiology, 46:125-134,
1967.
15. Deaner, D. G., and K. D. Kerri. Regrowth of fecal coliforms.
Journal of the American Water Works Association, 61:465-468,
1969.
16. Van Donsel, D. J., E. E. Geldreich, and N. A. Clarke. Seasonal
variations in survival of indicator bacteria in soil and
their contribution to storm-water pollution. Applied Micro-
biology. 15(6):1362-1370, Nov. 1967.
17. Bhaumik, H. D., and F. E. Clark. Soil moisture tension and
microbiological activity. Proceedings of the Soil Science
Society of America. 12:234-238, 1947.
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62
ACKNOWLEDGMENTS
Special acknowledgments are due to the following staff for their contri-
bution to this research.
Northeastern Illinois Research Center, Elwood
Mr. R. Louis Judson, Associate Agronomist
Mr. Raymond J. Keigher, Technician
Department of Agronomy
Mrs. Glee Blossey, Laboratory Technician
Mrs. Barbara Kraybill, Laboratory Technician
Mr. Sobhan-Ardakani, Research Assistant
Mr. Waldemar Miodeszewski, Research Assistant
Mr. Zenon Lis, Research Assistant
Department of Civil Engineering
Mr. Dick Cosset, Research Assistant
Mr. Sze-Ern Kuo, Research Assistant
Mr. James Schwing, Research Assistant
oU.S.Government Printing Office: 1971 — 759-287/2112 y O373
Region 5-11
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