THE EFFECTS OF MUNICIPAL WASTEWATER SLUDGE
ON LEACHATES AND GAS PRODUCTION FROM
SLUDGE-REFUSE LANDFILLS AND SLUDGE MONOFILLS
by
Joseph B. Farrell
Wastewater Research Division
Water Engineering Research Laboratory
Cincinnati, Ohio 45268
January 30, 1987
WATER ENGINEERING RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY.
CINCINNATI, OHIO 45268

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CONTENTS
Page
INTRODUCTION	 1
Background 		1
Literature Review		2
Objectives 		4
MATERIALS AND METHODS 		5
Experimental Design		5
Refuse and Sludge Sources and Composition		 .	7
Test Cell Construction		9
Test Cell Loading	10
Operating and Monitoring 		11
Method of Data Analysis					12
RESULTS	15
Leachate Quantity	15
Final Moisture Content		 .	17
Chemical Oxygen Demand 		20
TOC, VS, TS	24
pH	25
Chloride	28
Phosphate	32
Alaklinity	34
TKN		37
Volatile Acids 		39
Metals (Cd, Cr, Cu, Fe, Pb, Ni, Zn)	40
Priority Pollutants	53
Gas Production and Methane Content 		55
Temperature			58
DISCUSSION	59
General	59
Particular	61
CONCLUSIONS	65
RECOMMENDATIONS 	 68
ACKNOWLEDGMENT	69
LITERATURE CITED	70

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THE EFFECTS OF MUNICIPAL WASTEWATER SLUDGE
ON LEACHATES AND GAS PRODUCTION FROM
SLUDGE-REFUSE LANDFILLS AND SLUDGE MONOFILLS
by
Joseph B. Farrell
ABSTRACT
A four year experiment has been completed on the effect of municipal
wastewater sludge on leachate quality and gas production from simulated
landfill test cells containing municipal solid waste. Results indicate
that the introduction of 10 to 30 percent by volume of a 16 percent solids
sludge cake causes the initiation of rapid anaerobic biological activity
or stabilization (RBS) in about 6 months. Solid waste test cells not
containing sludge requireAabout 30 months before the onset of RBS.
During the 24 month interim, the test cells containing sludge produced
leachates containing about 1500 mg/L COD compared to values averaging
30,000 mg/L for the test cells without sludge. Heavy metal concentrations
in the leachate (Cd, Cr, Cu, Pb, N1, Fe, Zn) are generally lower initially
in the cells containing sludge but after 4 years are about the same as
for the cells containing no sludge.
Test cells containing only sludge show an excess of leachate over
infiltration whereas the opposite is true for sludge-solid waste landfills.
For test cells containing anaerobically digested sludge, leachates were
equivalent to solid waste landfills after onset of RBS except soluble
nitrogen was much higher. Test cells containing lime-treated raw sludge
showed soluble COD levels similar to solid waste landfills before onset
of RBS. Only one out of three test cells containing the lime sludge
achieved RBS after 4 years whereas four cells containing only solid waste
achieved RBS in less than 4 years. The 16 test cells containing sludge and
solid waste achieved RBS in less than 1 year.

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INTRODUCTION
Background
In the late 70's, passage of RCRA (1) made the nation aware that hazard-
ous waste disposal to the land would be regulated. Staff of the Municipal
Environmental Research Laboratory's (MERL) Wastewater Research Division (WRD),
charged with responsibility for EPA's wastewater sludge management program,
felt that eventually disposal of sludge to landfills would be subject to
regulatory scrutiny, even though it is a relatively benign substance com-
pared with hazardous wastes. Since about one-fourth of the wastewater
sludge produced is landfilled (2), findings of adverse effects would stimulate
regulation that might greatly complicate the already difficult task of
sludge disposal. Consequently WRD began an assessment of the information
available on effects of sludge landfilling practice.
WRD's initial assessment was that very little information was available
on the effects of sludge landfilling. Contacts with MERL's Solid and Hazard-
ous Wastes Research Division (SHWRD) reinforced this impression. Although
most of SHWRD's work was by then directed to hazardous wastes, one study
was underway in which the effects of industrial sludges in leachates from
refuse landfill was being studied—three of the test cells in this study
contained municipal sewage sludge. In 1981, it became clear that this study
was not complete enough to supply the desired informational needs on
sewage sludge effects. Consequently, WRD funded an experimental study of
the long-term effects of sludge in refuse landfills on leachate quality
and on the leachate from sludge "monofills" in which only sludge or
sludge-soil mixtures was disposed. At about the same time, SHWRD funded
a critical evaluation of the effects of sludge landfilling, to be drawn
from available information in the literature. The first infiltration
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water was charged to the simulated landfills in the experimental study in
June 1982. The critical evaluation was published in 1982 (3).
Literature Review
SHWRD's critical review of sludge landfill practice (Lu et al.--ref. 3)
found a few publications which reported information on leachate concentrations
from sludge or sludge-refuse landfills. These publications (4-13) were
summarized by Lu et al in Section 5 and Appendix A of their report. The
publications reported results of bench-scale lysimeter studies, results
from experimental cells constructed in the field, as well as results from
working landfills. The authors utilized this information to compare
leachate concentrations from sludge landfills, refuse landfills, and sludge-
refuse landfills, examining such parameters as COO, TOC, P, N, and heavy
metals. They lumped data together into three categories, refuse, co-disposal,
and sludge only landfills, and made comparisons regarding quality of
leachate from these three classes of landfills. They pointed out that
the results should be used with caution because the data were collected
from "young" landfills or experimental cells, all less than two years old.
A review of the specific conditions of each project indicate that
the authors' warning about use of their summary charts was understated.
In most cases the lumping together of the experimental results into
three categories was inappropriate. For example, for the co-disposal
case, the experimenters added liquid sludge to the top of the landfill
or landfill cells (5,6), and in one of these cases, milled rather than
whole refuse was used (6). It is doubtful that these two cases should
have been taken together to represent the effects of co-disposal. The
two cases from which data were drawn to indicate performance of sludge
landfills were a narrow-trench sludge landfill where the source of
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leachate was a well in the narrow-trench field but not directly under and
proximate to a trench (11), and a sludge disposal pond where the sample
well was 20 m below the land surface (12). Neither of these.cases represent
leachate from a landfill but more nearly measure anticipated concentration
at point of entry to groundwater.
The literature available provides results for a few specific cases
generally with very little information on the effect of time on leachate
concentrations. There is clearly a great need for a broad investigation
of the impact of major variables such as proportion of dewatered sludge
in a refuse landfill, infiltration rate, and especially time.
Pohland and Harper (14) have retroactively examined the results of
SHWRD's 19 - test cell study of the effects of co-disposal with refuse of
various industrial sludges and municipal sewage sludge on leachate composi-
tion and gas production. Three test cells containing 0.44%, 1.35%, and
4.26% sewage sludge (dry solids basis) were monitored for slightly over 8
years. Test cells were located below ground and attained annual average
temperatures of 10°C. Unfortunately, the test cells were not well sealed
against air intrusion and rapid biological stabilization (RBS), increased
methane production, simultaneous with a rapid increase in pH and drop in
COD of the leachate, did not occur. The results of the experiment indicate
that introduction of sludge did not greatly change leachate characteristics.
This conclusion is valid only for the pre-RBS conditions.
Pohland and Harper provide valuable insights regarding design of
test cells. They cite the report by Kinman et al (15) which evaluated
the condition of the 19 test cells at the termination of the study. These
investigators found that solid waste in sealed containers, primarily
garbage bags, were unaffected by 8 years residence in the test cells.
The suggestions in these two reports are of great value and will result
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in better studies in the future. Because our staff was in contact with
SHWRD project officers when the WRD experimental plan was being developed,
most of these suggested improvements were incorporated into the final
project plan.
Objectives
The primary objective of this investigation was to determine the
impact of sludge addition on landfills for domestic waste and compare
this impact with the effects of disposing sludge in landfills containing
only sludge. Primary responses evaluated were leachate composition and
quantity and gas release from simulated landfills operated under the
following conditions:
1.	Sludge landfills receiving dewatered anaerobically digested sludge
versus those receiving dewatered lime treated sludge.
2.	Sludge-only landfills versus refuse-only landfills versus codisposal
landfills.
3.	Codisposal landfills receiving various sludge loadings (10 percent,
20 percent, and 30 percent of the total sludge/refuse mass).
4.	Landfills receiving low versus high infiltration rates.
5.	Difference in landfill cell depth.
6.	Landfills spiked with elevated levels of specific organic compounds,
versus control landfills.
The experimental program was designed by WRD staff in consultation with
SHWRD staff and SCS Engineers. The experimental program was carried out by
SCS Engineers and its subcontractors, the University of Cincinnati and P.E.I.,
Inc. A draft report has been received which describes the experiment and
tabulates all results (16), along with a 660 page supplemental volume which
plots all effluent concentrations for all cells against time. The draft
report is a resource document. Much of the descriptive material in this
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report was drawn from it. However, it was not intended that Ref. 16
interpret all results and summarize them in a useful manner. The present
report attempts to bring attention to major findings and summarizes in a
systematic manner the effect of experimental variables, including time,
on each parameter investigated. It is anticipated that constructive
comment will generate other publications from other points of view drawn
from this extensive and successful experiment.
MATERIALS AND METHODS
Experimental Design
In order to maximize the information obtainable from the investigation,
the experiments utilized factorial designs. In the solid waste-sludge
experiment (SW-SL), two types of dewatered sludge were investigated, two
water addition rates, and three levels of sludge addition, comprising a
2x2x3 complete factorial experiment. There were thus a total of 12 test
cells, 4 at each level of sludge addition. The transport of priority
pollutants was also to be investigated, but because of the high cost of
analysis it was not directly included in the factorial experiment.
Instead, 4 test cells which duplicated one of the sludge addition levels
had the sludge spiked with a priority pollutant cocktail. If the priority
pollutants did not influence the biological activity taking place, these
test cells would serve as duplicates, providing an estimate of experimental
error.
Since the primary objective of the experiment was to determine the effect
of sludge addition on the quality of leachate from landfills, control test
cells containing only domestic solid waste were needed. Four solid waste
(SW) cells were included, 2 at the lower water rate and 2 at the higher
water rate.
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For the experiment with sludge (SL), three variables, sludge type,
cell height, and the effect of a spike, were investigated at two levels.
This is a 2^ factorial experiment and results in 8 test cells. If, as
expected, the priority pollutants did not affect the biological action
taking place or the leaching behavior of other constituents, the four test
cells containing the priority pollutant spike would serve as duplicates of the
four cells without the priority pollutant spike.
The experimental design is presented in Table 1. Depth of sludge in
the SL cells is shown in the table. Depth of the refuse or refuse-sludge
mixture in the SW and SW-SL cells was 1.8m. The water rates applied to
the SW and SW-SL cells were equivalent to approximately 25 and 50 cm
per year of rainfall. The water loading (1/kg dry solids) to the sludge
cells was the same, but because the mass of sludge in the cells were
different, the annual application rates were 4.8 and 14 cm/yr. These
rates appear small but are probably realistic for a sludge landfill.
Water release from a sludge cake is extremely slow and decreases with
increasing solids content. The author has calculated a drainage rate of
25 cm/yr for a 15 percent solids sludge under the influence of gravity
(based on a specific resistance of 2 x 10? cm/g). If higher water rates
than the 14 cm/yr had been used, the tall cells might have been flooded.
Because the cells occupied a large floor area, it was not possible
to put them all on the same floor in our laboratory building. Consequently,
some of cells were placed on a second level. Cells at the higher level
would be warmer so it was necessary to balance the experiment so that if
there were an effect of temperature it could be either discovered or
cancelled. The location of the cells is presented in Table 1. The
manner in which temperature effect can be estimated is discussed later.
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Refuse and Sludge Sources and Compositions
Required quantities of municipal refuse were obtained from City of
Cincinnati collection vehicles. The purpose was to obtain a waste which
typified household refuse generated in the U.S. A quantity of over
45 tonnes of municipal refuse was delivered to the project site where it
was manually mixed. This manual mix consisted of breaking open (but not
removing), all plastic bags, spreading and mixing materials, and removing
large or non-representative materials. After mixing, a representative
three percent sample was segregated from the waste mass and a refuse
characterization procedure was performed. The refuse was manually
separated and weighed to determine the physical composition. The fraction
of waste in each of 14 sorting categories is shown in Table 2.
Further physical and chemical analyses were carried out on refuse
grab samples, which were finely ground before analysis. Results are
presented in Table 3. Moisture content for the unshredded, as-delivered
refuse, based on 12 grab samples, averaged 42.2 percent.
Required quantities of municipal sludges were obtained from the Blue
Plains Wastewater Treatment Plant in Washington, D.C. A total of about
12 tonnes of anaerobically digested (AD) and lime treated (LT) sludges
were loaded in steel drums with lids and delivered by truck to the project
site in Cincinnati. Samples of the incoming sludges were obtained and
analyzed (17) for a variety of chemical parameters shown in Table 3. The
sludges differed significantly in composition with notably higher levels
for pH, alkalinity, and iron in the lime treated sludge.
It is clear from Table 3 that sludges and refuse are very different
materials. Hardly any parameter agrees within a factor of 2. The refuse
is much lower in TKN and total P, and higher in organics (COD). Alkalinity
and acidity are low in the refuse. The sludges are much higher in most
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of the heavy metals, although copper and lead in the refuse approach the
concentrations on the sludge. The greatest difference between the sludges
and the refuse is in physical characteristics. The sludges are homogenous
dark-colored masses with the consistency of stiff mud--they resist
penetration by water. The refuse is a heterogenous mixture best described
by a glance at Table 2. Even when compressed, it contains many voids and
channels. It avidly absorbs water. Containers and plastic film form
innumerable receptacles which can accumulate water. When the refuse is
saturated, its voids and channels may allow bypassing of freshly added
water.
The two sludges were also analyzed for organic priority pollutants
by gas chromatography/mass spectrometry (18). Results from these analyses
are shown in Table 4. The following three compounds were found in both
sludges at similar concentrations and at levels greater than 10 mg/kg dry
solids: bis (2-Ethylhexyl) phthalate, di-n-octyl phthalate, and
N-nitrosodiphenylamine. Two compounds, phenol and 4-chloro-3-methyl-phenol,
were reported at low or not-detected levels in the lime treated sludges,
but at elevated levels in the anaerobically digested sludge. These
substances form salts at high pH and might have been present in the
sludge but possibly were not extracted in the sample extraction procedure.
The remaining priority pollutants shown were detected in at least one
sludge sample and most were found at levels less than 4 mg/kg.
In order to track the behavior of priority pollutants in landfills,
sludge to be added to some of the cells was spiked with a priority
pollutant "cocktail", containing priority pollutants which appear in
sludge and can be analyzed by the stable-labelled-isotope technique. The
compounds added to the sludge were:
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Acenapthene
Ethyl benzene
Benzene
Naphthalene
Bis (2-Ethylhexyl) Phthalate Phenol
1,4-Dichlorobenzene
Pyrene
Dimethyl Phthalate
Toluene
Di-n-butyl Phthalate
PCB (Arochlor 1254)
The compounds were dissolved in methylene chloride and then thoroughly mixed
into the sludge shortly before it was added to the test cells. Concentrations
of the priority pollutants in the sludge were 114 mg/kg dry sludge solids
for the PCB and 128 mg/kg for each of the other priority pollutants.
Comparison with Table 4 shows that the concentrations of most of the priority
pollutants in the spiked sludge were much higher.
Test Cell Construction
The pilot-scale test cells were designed to provide durable, gas-tight
containers. In order to provide realistic results, refuse with only
minor preprocessing to remove oversize objects was to be used in the
cells. Consequently, the cells were as large as reasonably possible for
indoor installation to increase the likelihood that the contents of the
different cells would be similar in composition.
The cells are rolled steel tanks, double-welded at the seams, coated
with two interior coatings of high-build epoxy sealer to prevent rust.
Cross-section of the cells is presented schematically in Figure 1. The
dimensions of the cells are included on the figure. The cells are
provided with infiltration lines, leachate drains, and openings for the
temperature and gas probes. The infiltration lines consist of 1-inch
Schedule 40 (2.7 cm I.D.) threaded steel pipe, protruding into the head
space of each cell. The infiltration lines are equipped with full-spray
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brass nozzles for proportioning the monthly water doses over the entire
waste surface area. The leachate drains are 2.0 inch Schedule 40 (5.2 cm
I.D.), threaded steel nipples with PVC piping and valves for leachate
collection. Openings for the temperature and gas probes received 1/4
inch Schedule 40 (1 cm I.D.) brass bulkhead fittings and are sealed with
silicone-based compounds. Special pains were taken to assure that the
cells were gas-tight.
Test Cell Loading
Loading activities began with the placement of gravel layers loaded
in two 0.3 m lifts into each of the 28 cells. The first lift consisted of
large Ohio Silica pebbles averaging 1.9 cm to 3.8 cm diameter, previously
washed and screened repeatedly to remove the fines prior to placement in the
cells. The second lift consisted of small Ohio Silica pebbles. This stone
averaged 0.6 to 1.9 cm in diameter, and was thoroughly washed prior to loading
to remove the fines. Ttie gravel was washed in-place until the wash water
appeared to be free of solids.
The loading operations were performed in accordance with the program
design shown in Table 1. Generally, quantities of refuse and sludges
were weighed, loaded, and compacted in four 0.46 m high lifts in each test
cell. In the codisposal and refuse-only cells (Nos. 1 through 20), refuse
quantities were loaded first, followed by designated sludge types and
quantities added atop each refuse layer. The cells were loaded on a lift-
by-lift basis so that the first lift was completed in all cells before
moving on to the second lift. Temperature probes were installed on top of
the second lift and the probe lines exited through the sides of the test
cells. Loading activities were conducted continuously for four days
until the completion of the fourth lift in codisposal and refuse-only
test cells. At that time gas ports and leachate drains were installed
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and an infiltration spray nozzle was placed on the interior of the test
cell lids.
The sludge-only cells (Nos. 21 through 28) were loaded in a separate
operation and received preweighed quantities of anaerobically digested
or lime treated sludges. Temperature probes, gas ports, and leachate
drains were installed in the same manner.
The last steps of the loading operations included placement of the
test cell lids, final connection of gas ports, temperature probes and
infiltration lines, welding of the steel lids, and pressure testing to
ensure air and water-tight conditions. Table 5 presents the quantitative
results of the loading activities for the individual cells.
Operation and Monitoring
Operation and Monitoring activities were performed on a continuous
basis. Test cell temperatures (one probe per test cell) were recorded on
a daily basis for the first two months. Thereafter, temperatures were
monitored bi-weekly or on an as-appropriate basis. Leachate was drained
from each cell every month and its volume recorded. Two representative
samples of the leachate were collected, one for standard chemical analysis
and the other for GC/MS quantitation of trace organics.
Infiltration water was applied to every cell each month immediately
after the leachate had been drained. The infiltration rates are shown in
Table 1. Inspection and maintenance activities were also employed each
month for general housekeeping purposes and to ensure air and water
tightness of all cells.
Monitoring activities centered on providing physical/chemical
descriptions of the infiltration water, product gases, and generated
leachates. Generally, monitoring parameters were tested on an on-going
monthly schedule. Standard chemical analyses performed on leachate
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samples in the laboratory include pH, alkalinity, volatile acids, total
and volatile solids, total organic carbon (TOC), total phosphate, chlorides,
sulfide, seven metals, and trace priority pollutants. In early 1986, a
review of trace priority pollutant and metals data revealed that leaching
of these materials had reached low or stationary levels. Consequently,
analyses for these parameters was halted in March 1986.
In conjunction with the above analyses, gases generated from the
cells were monitored for composition and volume. On a bimonthly basis,
gas production by volume was measured for 72 hours and recorded for all
28 test cells. Every three months, the test cells were sampled and
analyzed by gas chromatograph for methane, carbon dioxide, nitrogen, and
oxygen contents. Table 6 lists the monitoring methods utilized for this
project. Except for gas analyses and priority pollutant analyses, methods
were drawn from Standard Methods (17). Priority pollutant analyses were
carried out by EPA Method 1625 (18).
Method for Data Analysis
Use of Annual Averages
In the data analysis process, the results for all measurements, such
as COD, TOC, and metal concentrations in the leachate, were plotted
against time and the curves were compared and examined for trends. Over
600 graphs were generated. The task of data analysis is to present this
huge amount of information in a condensed but still useful form.
For every parameter and every cell, annual averages were calculated
for each of the four years. A typical data page showing results of
monthly measurements and annual averages for COD is presented in Table 7.
In many cases, these averages could be utilized to detect the influence
of time and the other experimental variables (sludge type, sludge content,
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infiltration rate, cell height) as well as permit comparisons of average
outputs from the SW, SW-SL, and SL cells.
To calculate the annual average performance for the SW cells, the
annual averages for the four cells were averaged together to give a
grand average. For the SW-SL cells, there are two sets of data for
20 percent sludge addition cells and one set each for 10 and 30 percent
cells. To avoid excessively weighting the average, the results for the
20 percent cells were first averaged before being included in the grand
average of the 10, 20, and 30 percent addition cells.
For the SL cells, a serious problem was encountered. One cell
(No. 28--see Table 1) showed anomalous results for many parameters.
Evidently something had gone wrong within the cell. Results for this cell
were generally not used. However, to balance the averages, the value for
Cell 28 was generally replaced with the value for its duplicate, Cell 24.
Where appropriate, the SW-SL or SL average was further subdivided.
For example, the SL group might be subdivided according to sludge type,
forming an SL-AD group (the average of Cells 21, 23, 25, 27) and an
SL-LT group (the average of Cells 22, 24, 26, and 28).
Interpretation of Factorial Experiments
SW -- The SW cells were not arranged in a factorial experiment so
interpretation is conventional. There were duplicate cells at two
infiltration levels. The variance can be calculated from the two
differences between duplicates. The variance for an effect of infiltra-
tion, the difference between average of duplicates, can be calculated
(s| = s^). A 95 percent confidence interval can be calculated using
the t-statistic for two degrees of freedom (CI = +_ 4.3 se). For most
parameters, it could probably have been assumed that the variance for
the SW and the SW-SL cells was similar. Using this assumption would
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have had a minimal effect on results. Examination of Table 1 and Table 8
(see next section) shows that duplicate cells 17 and 19 are at different
levels as are duplicate cells 18 and 20. Any effect of different elevation
will be included in the estimate of error. Fortunately, results with the
the SW-SL cells showed that elevation rarely had a substantial effect.
SW-SL -- The calculation of the effects of experimental variables
such as sludge type, infiltration rate, etc., follows the procedures
outlined in numerous texts in statistics (for example, Box et al. -
ref. 19). Initial calculations showed that for the SW-SL cells, the
priority pollutant spike had no effect on any other parameters. Thus,
Cells 5-13, 6-14, 7-15, and 8-16 were truly duplicates. The difference
between results for each of these cells gave 4 estimates of error. The
variance of the parameter could be calculated, and the variance of an
effect determined (s| = 1/2 s^ for a 2^ factorial). A 95 percent
confidence interval could then be calculated using the t-statistic
with four degrees of freedom (CI = + 2.78 se).
The calculation of effects is illustrated in the sign table shown
in Table 8. To determine an effect on interaction, the average of
the low levels (the - signs) is subtracted from the average of the high
levels (the + signs). The levels of the factors correspond to Table 1.
The elevation (E) was selected to correspond to - TxIxP (the three
factor interaction) for the 10-20 percent solids experiment and to
TxIxP for the 20-30 percent experiment. When the interaction TxIxP is
calculated, it includes the effect, -E, for the 10-20 percent experiment
and the effect, +E, for the 20-30 percent experiment. The effect of
elevation cancels out for all main effects, but its interactions with
main effects appear with the other two-factor interactions. The three-
factor interaction is generally very small so both experiments allow an
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estimate of E. Throughout the experiment the effect, E (assumed to be
the three-factor interaction) was small. Consequently its two-factor
interaction with the other main factors was ignored. In almost all
experiments, the three factor interactions (which include E) was small.
They are discussed in a separate section on the effect of temperature.
In Table 8, the duplicate cells (the 20 percent sludge cells) are
shown as single cells. Results for each pair were averaged and the same
values were used to calculate effects in the 10-20 percent and the 20-30
percent experiment. The results scattered less when the data were combined
in this fashion.
SL -- For the SL cells, it was soon realized that the priority pollutant
spike did not affect other measured parameters. Consequently Cells 21-25,
22-26, 23-27, and 24-28 were truly duplicates. As noted elsewhere, Cell 28
was found to be faulty and results for Cell 24 substituted for it. The
difference could not be used in estimates of error, so there were only 3
estimates of error. From these three estimates, the variance of an effect
could be determined (see SW-SL above). A 95 percent confidence interval
could be calculated using the t-statistic with three degrees of freedom
(CI = _+ 3.18 se). The calculation of the effects was similar to that
described for the SW-SL cells except there was no elevation effect to
be considered.
RESULTS
Leachate Quantity
The quantity of leachate is necessarily related to the quantity of
infiltration water and infiltration rate was a controlled variable, added
at a constant rate throughout the experiment. Ultimately leachate rate
will approximate infiltration rate. However, in the early years of the
experiment, the water-holding or water-releasing nature of the waste is
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expected to influence the rate of leachate release. The extent of this
effect is shown in Figure 2 for the SW cells and in Figure 3 for the
SW-SL (20% AD) cells (20 percent anaerobically digested sludge), where
cumulative amounts of infiltration water and leachate are plotted against
time. The SW cells did not release any leachate until about 6 months
after infiltration water was added even at the high rate of infiltration.
The SW-SL (20% AD) cells released leachate after about 4 months. The
infiltration and leachate curves became parallel straight lines after
about a year. The horizontal distance between the lines gives the time
lag before leachate quantity equals infiltration quantity. Time lags
obtained from graphs of the data for all of the SW and SW-SL cells
(duplicates are averaged) are presented in Figure 4. The lag is higher
for the low infiltration rate, and addition of sludge reduces the lag.
There is an indication that the lags may be less for LT sludge. Addition
of sludge clearly reduces the time lag before a landfill starts producing
leachate.
For the sludge cells, leachate rate initially exceeded infiltration
rate. This effect persisted for the entire 4 years for LT sludges (lime
treated sludges) but eventually an equilibrium was reached for the AD
sludges. These results are presented in Figure 5 for AD sludge cells and
in Figure 6 for the LT sludge cells. Since infiltration water was applied
to tall and short cells at the same volume per unit mass of dry solids,
cumulative leachate volume is plotted on the same basis to make results
comparable.
Considering first the results for the AD cells, Figure 5 shows that
cumulative leachate leads infiltration by 30 months for the short cells
and by 17 months for the tall cells. Although the infiltration per day
per unit mass of sludge solids was the same for short and tall cells, the
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tall cells necessarily received more water per day per unit of cross-
sectional area than the short cells--approximately three times as much.
Evidently flow of this greater volume of water was hindered so cumulative
leachate volume led infiltration less for the tall cells.
Results for the LT sludges are shown in Figure 6. Smooth curves
have been drawn for the short cell data and for one of the tall cells.
The other tall cell (No. 28) showed anomalous behavior. The effect
of height is similar to the result with AD sludge. However, leachate
rate (the slope of the curve) was in excess of infiltration rate even
after 45 months.
Moisture Content
SW Cells
The residual moisture content after a period of leaching is important
because net leachate can then be obtained from a knowledge of initial
moisture and total infiltration. Solids content for the SW and the SW-SL
cells after 4 years is presented in Figure 7.
As noted earlier (Leachate Quantity—see above), the SW cells reached
equilibrium, with input equalling output during the second year of operation.
The net absorption of leachate can be calculated from initial and final
solids content. This calculation is shown in Table 9. The refuse in the
SW cells absorbed 0.74 kg of water/kg of dry solids and reached an equilibrium
solids content of 40.5 percent.
SW-SL Cells
The results presented in Figure 9 show a decline in equilibrium solids
content of the cell contents as the sludge proportion increases. The net
absorption (see Table 9) decreases substantially as sludge proportion
increases, primarily because the sludge addition decreased the initial
percent solids.
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SL Cells
The sludge cells released water instead of absorbing it (see Table 9).
Amount released exceeded 1.0 kg/kg d.s. The LT cells lost considerably
more water. As noted earlier, the LT cells had not reached equilibrium
and were still releasing slightly more water per month than they received
even after 4 years.
Statistical Analysis
SW -- Only the final solids content (Sf) of the SW cells (wet basis)
was examined statistically. Results are as follows:
Solids Content (%) Ave(%)	I	CI
End of Year 4 40.8	-2.7 + 1 .6
The change from low to high infiltration rate (I) reduced the average solids
content 2.7 percent. Expressed as an equation:
Sf = 40.8 - 1.35 I
where high I = +1, low I = - 1
SW-SL -- Only final solids content (percent solids on a wet basis)
of the test cells was examined statistically. For illustrative purposes,
effects that were more than one-third of the 95 percent confidence
interval are as shown:
Solids Content (%)
Ave T	I	P TxI TxP IxP
10-20% 39.0% 0.5 -0.2 -1.1 -0.6 1.2
20-30% 38.0% 1.6 -1.2 ' -0.8	-1.4
The only statistically significant effect on test cell percent solids
is the 1.6 percent increase caused by sludge type (T) for the 20-30 percent
case. Some other effects are worth noting although they are not significant.
Increased percent sludge (P) causes a decrease in test cell percent solids
for both cases. Increased infiltration 'I) censes a decrease for the
-18-
CI
+ 1.6
+ 1.6

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20-30 percent case. Infiltration and percent sludge have a substantial
interaction (that is, the effect of infiltration is 1.1 percent higher at
20 percent sludge than at 30 percent sludge).
The effects noted can be found by careful scrutiny of Figure 7. For
the 20-30 percent case, the tagged points (LT sludge) are higher than the
untagged sludge) points, indicating sludge type changes solids content
of the test cells. Similarly, the solid points (high infiltration) are
lower than the open points (low infiltration), indicating an effect of
infiltration rate. The reduction in solids content caused by increased
infiltration is greater at 30 percent than at 20 percent sludge, verifying
the interaction noted above. The graph allows us to detect the effects
but gives no basis for estimating their significance. The line drawn on
the figure shows an effect of percent sludge. The effect is verified by
the statistical analysis but the evidence that the observation is true is
not strong.
SL -- The effect of experimental variables on solids content (weight
percent solids on a wet basis) in the sludge test cells after 4 years is
shown below. Only significant effects are shown.
Sol ids Content (%) Ave	T	H	CI
End of Year 4 21.3	4.4 -3.0 +2.1
or, expressed as an equation,
% Solids = 21.3 + 2.2 T - 1.5 H
where T = -1 for'AD or + 1 for LT
H (cell height) = -1 for short, + 1 for tall cells.
The LT sludge evidently drained to a high solids content than the
AD sludges (the LT sludges were still undergoing a net water loss at
the end of Year 4), and the short cells also drained to a higher solids
content than the tall cells.
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Chemical Oxygen Demand (COD)
SW Cells
Annual average concentrations of COD (mg/L) for cell groupings are
shown in Table 10. Solid waste cells are the highest initially but after
four years fall into the same range as the SW-SL and SL-AD cells.
The dramatic influence of time on leachate COD for the SW cells is
presented graphically in Figure 8. The duplicate low and high infiltraton
cells start out with leachates at about equal concentrations and after 40
months are again at about equal concentrations but at a much lower level.
In the intervening months, various cells drop sharply from high to low
COD's, in an apparently random manner. As will become evident later (see
section on pH), the drop is associated with the onset of the anaerobic
processes that convert soluble organic matter to carbon dioxide and methane.
The only variable investigated in the SW cells was the infiltration
rate. As can be seen in Figure 8, COD concentration was 1.5 times higher
for the low infiltration rate in the early months and 2.0 times higher in
the late months.
SW-SL Cells
Examination of Table 10 shows that addition of sludge to the solid
waste greatly lowers COD in the early years. After four years the
difference between SW and SW-SL cells is not great. Results for the
cells containing 20 percent anaerobically digested (AD) sludge are presented
graphically in Figure 9 for the high infiltration rate. For comparison,
SW cell results from Figure 8 for the high infiltration rate are presented
on this diagram. It is evident that the anaerobic processes that reduce
the COD of the leachate commenced much sooner for the cells containing
sludge.
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The SW-SL cells containing 1ime-treated (LT) sludge are compared
with the SW-SL-AD cells at high and low infiltration rates in Figures 10
and 11. The leachate from the AD cells is slightly lower in COD than
from the LT cells. There is insufficient evidence to indicate that the
start of anaerobic processes is different in the two types of cells.
SL Cells
The COD concentration in the leachate from the sludge cells showed
marked differences between AD and LT cells. As shown in Figure 12, COD
concentrations for AD cells were low and gradually diminished with time.
Leachate from LT cells averaged ten times higher in concentration than
from AD cells. ' One LT cell, after 3 years, experienced a drop in pH
initiated by or coincident with commencement of anaerobic digestion,
with the result that COD concentration dropped nearly to the level for
the AD cells.
Statistical Analysis
SW -- Because the four SW test cells commenced anaerobic activity
irregularly during the four years, only the last 6 months of the fourth
year can be examined. Results are as follows:
COD (mg/L)	Ave	I	CI
Months 43-48	965	-733 +236 (COD, mg/1)
Expressed as an equation,
COD, Months 43-48 (mg/L) = 965 - 366 I
where I = -1 for Low I, +1 for High I
SW-SL -- Since the data for the SW-SL cells have been nearly com-
pletely presented in Figures 9-11, only statistical analyses of the average
of the 4th year results is presented. Effects are shown below:
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COD (mg/L) Ave	J_ _I_ Txl	CI
Y4, 10-20% 810	145 -680 - 60 +160
Y4, 20-30% 830	310 -800 -200 +160
Effects that were smaller than the confidence interval in the analysis
for both the 10-20% and 20-30% cases were dropped. The Txl interaction
probably exists since it is substantial in the analysis of both sets of
data.
The information can be converted into equations by dividing the
effects by 2:
COD-Y4, 10-20% = 810 + 72T - 3401 - 30 Txl
COD-Y4, 20-30% = 815 + 1551 - 4001 - 100 Txl
where T = -1 for AD sludge, +1 for LT sludge
I = -1 for high I, +1 for low I
Average values of COD (mg/1) for the average of the two sets of data
for the 20% cells are compared with values calculated from these two
equations are compared below:
Experimental
Values
T
I
Ya, 10-20
(calcd)
Ya, 20-30
(calcd)
Ave
(calcd)
1020
-
-
1048
975
1012
1410
+
-
1252
1485
1368
430
-
+
428
375
402
490
+
+
512
485
498
The agreement of the calculated average with the experimental values is
good. For 20% sludge addition, the average should be used. Since
percent sludge (P) showed no significant effects, all three sludge addi-
tions gave the same result.
The results for the SW-SL cells were examined to determine whether
the experimental variables influenced start-up time (time for the COD drop).
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Although cells with AD sludges averaged a 3 month earlier startup than
for LT cells this effect was not significant. High or low infiltration
had no effect. Average time at the point where COD dropped below 5000 mg/1
was 11.5 months for cells to which sludge was added (standard deviation, s,
= 1.5 mo). For SW cells, this start-up time averaged 33 months (s = 6.3 mo.)
The COD concentrations in the period before startup of methane genera-
tion were compared by comparing the average of the highest three contiguous
monthly concentrations for each cell. Comparison of duplicate runs yielded
a very wide 95% confidence interval (_+ 22,500 mg/L) so an alternative
comparison was used. The averages were listed in the order of increasing
concentration as shown in Table 11. SW-SL-AD cells are concentrated in
the low ranks and SW cells in the high ranks. That this ordering should
occur by chance is highly unlikely. For example, the probability that by
chance the four SW cells should all rank in the five largest COD's is
0.0010. Of the 16 SW-SL cells, the probability that the 5 with the
largest COD's should all be LT cells is 0.016. The probability that 6 of
the 7 cells with the smallest COD's should be AD cells is 0.020. It is
clear from these considerations that the AD cells have smaller COD's in
this first year than the LT cells, and the SW cells are higher than both.
SL -- Statistical analysis was not carried out for the SL results.
The large effect the sludge type is obvious from Figure 12. The irregular
behavior of one of the LT cells (No. 22) and the failure of cell 28 due
to an unknown cause make a formal calculation of effects on COD pointless.
Examination of the last 4 months of Year 4 showed that the COD levels in
the AD cells and the single LT cell (Cell 22) were leveling off. The
average COD's (mg/L) of these last four months are presented below:
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AD


LT

Cell
Ht
COD
Cell
Ht
COD
21
S
470
22
S
2,280
23
T
617
24
T
17,600
25
S
368
26
S
16,050
27
T
680
27
_
_ _
The COO level of the leachate from the AD cells is substantially lower
than for the SW and SW-SL cells (see above). However, the LT cells are higher.
Even the one cell that commenced anaerobic digestion (cell 22) was producing
a leachate with more than twice the COD concentration of the SW and SW-SL
eel 1s.
TOC, VS, TS
TOC (total organic carbon), VS (volatile solids), and TS (total solids)
concentrations are measures of pollution similar to COD and results are
likely to be redundant. In Figures 13 to 15, COD is plotted versus TOC
for leachates from every SW and SW-SL cell. In these curves, annual average
COD's are plotted against annual average TOC's for each cell. If individual
monthly values were plotted, there would be much more scatter. The COD
vs. TOC correlation for leachate from SW cells is good, and agrees well
with all of the other COD vs. TOC data for leachates from SW-SL and SL
cells. Because of this excellent correspondence between COD and TOC, TOC
results will mirror results with COD, so no further analysis was conducted.
VS and COD concentrations were similarly compared. In Figures 16
to 18, COD is compared to VS for leachates from SW, SW-SL, and SL cells.
Annual average COD's and VS's for each cell were compared, which reduced
scatter. The correlation between COD and VS is excellent for SW and SW-SL
leachates regardless of the sludge type in the SW-SL cells. For the SL
cells, there is no useful correlation; scatter is substantial and the
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point5 for the AD and LT sludges form divergent clusters. There is no
easy explanation for this behavior. Evidently, leachate from cells con-
taining mostly refuse and cells containing only sludge differ in composition
and this difference causes the discrepancy. It is interesting that no
problems were encountered when COD and TOC were compared even though
these tests measure different chemical characteristics.
No further analysis of effect of variables on VS is warranted. For
the SW and SW-SL cells, the reason is the excellent correlation between
COD and VS. For the SL cells, the reason is the opposite. VS behaves
in a very strange way for AD and LT sludges. Any analysis based on VS
would be of dubious value.
Since it was not likely that total solids (or total non-volatile solids)
offered any special insights into landfill behavior, effects of time and
process variables on the parameter were not investigated.
£H
SW Cells
Annual average values of pH for various cell groupings are presented
in Table 10. The grouping of cells has been selected to make evident
differences that appeared in a preliminary analysis of the data. The SW
cells showed a rise in pH in the 3rd year that continued into the fourth
year. Scrutiny of the month by month values revealed the pH rise was
abrupt for each cell, increasing about 1 pH unit in a period of 1 to 4
months. The pH changes coincided with the onset of the anaerobic processes
that convert COD and volatile acids to carbon dioxide and methane.
The month of the change is given below for the SW cells:
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Cel1	I	Elevation	Month
17	low	U	21-22
19	low	L	p 26-27
18	high	L	I 35-36
20	high	U	37-38
Elevation is shown because the upper cells were slightly warmer
(1.6°F) than the lower cells. Low infiltration rate corresponds to the
earlier onset of the pH change (elevation does not), but there is
insufficient information for a conclusion.
The change in pH is related to changes in other parameters. Con-
centrations of other parameters affected by pH or by other changes
occurring simultaneously are shown for one of the SW cells (No. 19) in
Figure 19. COD, Fe, and Zn concentrations as well as pH are plotted
against time. The correspondence between these parameters is unmistake-
able. It is not always possible to be certain as to causes of the
changes. The commencement of anaerobic activity consumes volatile acids,
causes pH to rise, and, because CO2 is formed, increases bicarbonate ion
concentration in the leachate. Oxygen diminishes either by aerobic
processes or because it is flushed out by the digestion gas. The abrupt
reductions in Fe and Zn may be related to the change in pH or in oxidation-
reduction potential, or to the increase in bicarbonate concentration.
SW-SL Cells
The pH increase noted for SW cells also occurred for the SW-SL cells
but earlier. The month of the increase is shown in Table 12 for all SW
and SW-SL cells. The month of the drop in concentrations of other
leachate parameters including phosphate, Fe, Zn, COD, volatile acids, as
well as oxygen in the gas phase are also shown. All parameters except Zn
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show a good correspondence. Zn shows a correspondence only for three of
the SW cells and one SW-Sl cell. The Zn concentrations for all cells
containing both SW and sludge (except Cell 9) were much lower than the
concentrations in the leachate leaving the SW cells and showed no clear
change.
SL Cells
The pH of the sludge cells did not show any sharp changes with time.
The pH of the AO cells drifted upward towards a neutral pH (pH = 7).
The LT cells showed a curious behavior, actually drifting upward to high
pH's and peaking in Year 3.
One LT cell (No. 22) dropped in pH about halfway through Year 3,
and started to produce gas. The time-pH relationship is shown below:
Mo. 24 26 28 30 32 33 34 35 36
pH 9.2 9.0 8.8 8.6 7.8 6.9 7.1 7.1 7.6
It is likely that the other LT cells would eventually experience similar
behavior.
Statistical Analysis
SW -- Analysis of the pH change of the annual averages is pointless
because of the random nature of the pH increases which occurred in these
years. The averages of first six months of Year 2 and the last six months
of Year 4 were examined because there were no sharp changes during these
periods and they preceded (Year 1) or followed (Year 4) the pH changes.
Results are shown below:
pH	Ave	I	CI
Year (1 to 1.5) 5.50	-0.19	+0.22
Year (3.5 to 4) 6.74	- 0.35	+ 0.05
The results indicate that pH is lowered by the higher infiltration
rate both before and after the pH increase. The effect for pH
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(1-1.5 yr) is small and is smaller than the 95 percent confidence interval.
The pH for the 3.5-4 year period is only slightly below a neutral pH
(i.e., pH of 7).
SW-SL -- Since the abrupt increases in pH occurred in the first
two years, the averages for third and fourth years can be examined
for relationships. Results are shown below:

pH
Ave
T
I
Txl
TxP
CI
Y3,
10-20
7.11
.11
- .25
.00
.09
+_ .07
Y3,
20-30
7.09
CO
CM
•
- .22
00
o
•
1
.08
+ .07
Y4,
10-10
6.87
.09
- .28
- .02
.12
+ .12
Y4,
20-30
6.83
.23
- .24
- .05
.02
+ .12
The effects for Year 3 and Year 4 are surprisingly consistent. The IT
sludge increases the pH and the high leachate rate lowers it.
SL -- It is only possible to examine the AD cells for pH. Of the
4 LT cells, one cell (No. 22) showed the abnormal drop in pH noted
earlier and another (Cell No. 28) showed anomalous results in almost all
parameters. Average AD results for the last two years are presented
below:
pH	Year 3	Year 4
Averages Low H 6.36	6.44
High H 6.27	6.27
Std. dev. 0.06	0.05
There seems to be a consistent effect of height but the effect is not
significant.
Chloride
SW Cells
Average annual chloride concentration (mg/L) for cell groups are
shown in Table 13. SW and SW-SL cells decline in concentration in
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approximately the same fashion.
The chloride ion tan serve as a tracer to estimate the manner in
which infiltration water moves through a test cell. The highly soluble
chloride ion is likely to be present at or near its maximum solution
concentration as soon as the solid waste is wet with infiltrtion water.
The chloride and its carrier water will mix with or be pushed out of the
cell by incoming infiltration. This scenario would be invalidated if
large deposits of chloride salts (e.g., boxes of sodium chloride) are
present to slowly release chloride into the leachate stream or if
chloride is precipitated. A check of calculated solubility products
of lead and copper chlorides (the two most common insoluble chlorides),
using actual leachate concentrations, against solubility product
constants showed that precipitation would not occur. The consistency
of chloride decline in all the cells indicated that deposits of chloride
in some cells were not upsetting results.
To test the manner of flow of leachate through the cells, the chloride
concentrations in leachates from a low and a high infiltration rate SW
cell were plotted versus time (see Figure 20). The ordinate (concentration)
is logarithmic and the abscissa (time) is arithmetic. If the infiltration
water mixed with the leachate water already in the cell in the manner
water nixes into a well-stirred vessel, the concentration vs. time curve
would be a straight line. If the flow regime were displacement (i.e.,
plug) flow, concentration would be uniform at first, followed by a sharp
drop to low concentrations.
The data for the SW cells in Figure 20 show substantial scatter
but the general shape of the relationship is clear. The curve resembles
the fully mixed vessel behavior rather than plug flow. There are
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innumerable scenarios that could produce this kind of a concentration
vs. time curve. One would be the presence of dozens of "pockets" capable
of holding water (e.g., open cans and plastic bags) that fill with
relatively strong chloride salt solution. The first leachate should be
fairly strong in leachate because chloride salts are readily soluble.
As leaching progresses, infiltration water trickles into these pockets
and well-mixed leachate, at equilibrium with the contents of the pocket,
overflows to become part of the total leachate. The concentration of
chloride leaving the test cell would decline slowly with time, resembling
the behavior of a well-mixed vessel.
SW-SL
The individual SW-SL cells show leachate concentration curves
generally similar to curves for the SW cells but there are some differ-
ences. The average concentrations are higher because of the high
concentrations of chloride in the sludges. The SW-SL cells do not lose
chloride as rapidly as the SW cells. This is illustrated below by
comparing the rates of average concentration in the successive years to
Year 2 concentration. Year 2 was used rather than Year 1 because
Year 1 results show substantial scatter.
Ratios	Year Y2	Y3	Y4
SW	l	0.59	0.33
SW-SL, 10%	1	0.67	0.45
, 20%	1	0.69	0.50
, 30%	1	0.69	0.49
The declines are slower for the SW-SL cells. Evidence is not strong that
there are differences among the SW-SL cells grouped by percent sludge.
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SI Cells
Average chloride concentrations are much higher for the sludge cells
than for the SW cells. As noted earlier, ferric chloride is used to
precipitate phosphate in the wastewater treatment process at Blue Plains
and it was used to condition the AD sludge for dewatering.
The decline in chloride concentration for a tall and short cell
containing AD sludge is shown in Figure 20. The decline is much less
rapid than for the SW cells shown in Figure 20 because the annual
infiltration rate relative to the initial mass of water in the sludge
is much lower for the SL cells. The long period during which the chloride
concentration does not fall may be related to the difficulty encountered
by infiltration water in penetrating the sludge. There is no sharp drop
in concentration indicating displacement flow, although this could
eventually happen. The total volume of infiltration after 4 years was
less than the volume of the water associated with the sludge in the cells.
Statistical Analysis
SW -- In order to make a valid quantitative comparison of fall in
leachate concentration of chloride with time and with infiltration rate,
the leachate compositions of the 13 and 14 months and of the 47 and 48
months were averaged, and the ratio of the concentrations were compared.
Results are given below:
Ave	I	CI
Ratio: Ca7-AR	0.195 -0.140 +0.09
^13—14
The average reduction is substantial, indicating that 80 percent of the
chloride present in the 13-14 month period was washed out by the 47-48
month period. • The increase in infiltration caused a large reduction
in the ratio.
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SW-SL -- The ratio of concentrations in Months 13-14 to Months 47-48
was also calculated for the SW-SL cells with the following results.
Ave	T	I	CI
Ratio Ca7.aa: 0.286 -0.11 -0.20 +0.10
C13-14
0.295 -0.08 -0.18 +0.10
Only sludge type and infiltration showed significant effects. Surprisingly
percent sludge in the landfill did not affect the ratio even though an
increase in percent sludge increases initial water content. The ratio
was higher for LT sludge than for AD sludge (T = ca. -0.10). For some
reason, the cells with LT sludge retain the chloride more than the cells
with AD sludge.
SL -- Analysis of the ratio of concentrations of Months 47-48 to
Months 13-14 showed excessive error in duplicates (CI of an effect = _+0.20)
No effects were significant. Average of all cells except Cell 28 and
standard deviation of the ratio were:
Ratio C47_4r: Ave = 0.67 (s = 0.097).
c13-14
Phosphate
SW Cells
Annual average phosphate concentrations (mg/L as P) for groupings of
cells are shown in Table 13. Superficially, the phosphates appear to
drop in a regular fashion. However, as was pointed out in the section on
pH, a large abrupt drop in phosphate occurs when pH increases with the
onset of anaerobic processes. This drop occurred for all of the SW
cells. The drop is from concentrations considerably greater than 15 mg/L
into the range of 10-15 mg/L. After this initial drop, concentrations
declined uniformly with time.

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SW-SL Cells
The SW-SL cells had higher average annual concentrations of phosphate
than the SW cells, evidently an effect of sludge addition.- For a few cells
(Cells 2, 11, and 13--see Table 12), the phosphate concentrations were below
15 mg/L at the time of the pH break. In this circumstance, no phosphate
break was seen.
SL Cells
The sludge cells show much lower average annual concentration than the
SW or SW-SL cells. The averages for the AD and LT cells are about the same
for the first three years. In Year 4, each of the unspiked cells (Nos. 21,
22, 23) showed an increase in phosphate concentration in the leachate,
increasing the average value, whereas the individual values and the average
for the spiked cells (Nos. 25, 26, 27) remained about the same. It is
possible that this is an effect of spiking. A speculative suggestion is
that the increase in soluble phosphate is the result of some kind of
bacterial action that releases phosphate that is suppressed by toxic
effects of the chemicals in the "spike."
Statistical Analysis
SW -- The SW cells were only examined in Year 4, because preceding
years were affected by the sudden drops in phosphate concentration asso-
ciated with pH change. Results for Year 4 are as follows:
Phosphate (mg/L	Ave	I	CI
Year 4	5.0 -5.0 +276
SW-SL -- The SW-SL cells were examined in Years 3 and 4. Results
are shown below:
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Ave
T
I
Txl
TxP
IxP
CI
Year 3, 10-20
6.8
3.0
-2.2
0.2
1.3
-0.2
+0.5
20-30
6.9
4.3
-3.5
-1.8
0.02
-1.0
+0.5
Year 4, 10-20
5.4
2.3
-1.9
-0.4
1.0
-1.0
+1.5
20-30
5.5
3.4
-3.0
-1.9
0.2
-0.1
+1.5
These results are unusual in that interactions are numerous. It is
surprising to find TxP and IxP interactions when P (percent solids) itself
does not show an effect. It is speculated that the confidence interval of
Year 4 is more realistic than the one for Year 3. Then only T (sludge type),
I (infiltration) and their interaction Txl have consistent and large effects.
LT sludge added to the landfill increases PO4 concentration, and increased
infiltration reduces it.
SL -- The sludge cell data showed substantial variability between
duplicates. Consequently no evaluation of effects was possible. As noted
earlier, it is conceivable that the increased variability between duplicates
is actually an effect of the spike which might have lowered bacterial
activity in the entire set of duplicates (Cells 25-28).
A1 kalinity
SW Cells
Annual average alkalinity concentrations are presented in Table 13
for various cell groupings. Alkalinity declines in a relatively regular
fashion. There were no sudden drops associated with pH change or start
of anaerobic activity.
The decline in alkalinity relative to decline in chloride is dis-
cussed in the following section.
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SU-SL Cells
Annual average concentrations are lower for SW-SL cells than for SW
cells, evidently the effect of added sludge. The decline with time is
similar to the decline for SW cells. The decline in alkalinity relative
to decline in chloride for SW and SW-SL cells can be compared below by
observing the ratio of their average concentrations for the 4 years of
the experiment:
Ratio (Alk/Cl)
Year
1
2
3
4

SW
8.6
8.5
8.3
8.2

SW-SL
4.3
2.9
ro
•
00
3.2
A constant ratio means that alkalinity and CI decline in a similar fashion.
For SW, the ratio is constant; for SW-SL, discounting Year 1 where conditions
typically were unsettled, ratios are nearly constant. This is a surprising
result, and could be interpreted to mean that alkalinity was originally
present and is just being washed out by dilution, just like chloride. It
appears that the biological reactions that occur do not produce soluble
cations, such as ammonium, that would capture carbon dioxide as bicarbonate,
to produce new soluble alkalinity.
SL Cells
Annual average concentrations for sludge cells are presented in Table 13.
The leachate from the LT sludge is much higher in alkalinity than from the
AD sludge. Concentrations do not decline in the same fashion as do chloride
concentrations.
Statistical Analyses
SW — Averages and effect of infiltration were evaluated for Years 2
and 4. Results are presented below:
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Alkalinity (mg/L)	Ave	I	CI
Year 2	11,460 -4,560 +1,380
Year 4	3,600 -2,070 +2,070
Increase in infiltration reduces alkalinity for both years, but proportionately
by a greater extent in Year 4 and in Year 2. The effects are statistically
significant.
SW-SL -- Averages and effects for Years 2 and 4 are presented below:
Alkalinity (mg/L)
Year 2, 10-20%
, 20-30%
Year 4, 10-20%
, 20-40%
Type of sludge added to the SW has a large effect in both years. Increase in
infiltration (I) reduces concentration in both years, but proportionately
by a higher amount in Year 4. Type of sludge and infiltration show a consistent
but small interaction.
SL -- The alkalinity for the AD and SL sludges differ by over a factor
of 10. In this case, it is best to separate the experiment into an AD
sludge experiment and an LT sludge experiment. Results are shown below for
Years 2 and 4:
Alkalinity (mg/L)
AD Sludge,	Ave
Year 2	795
Year 4	914
The confidence interval was based on the average standard deviation
for Years 2 and 4 and the combined degrees of freedom (4), Evidently
alkalinity is higher for the high cells. This effect would not have been
Ave	_T_	_I_	_P_ Txl_	TxP CI
6,220	2,020	-2,780	-560 - 68 +470
5,800	2,220	-2,400	-280 -680 +470
3,330	570	-2,200	-260	650 +460
3,190	1,320	-2,100	-624 100 +460
H	CI
250	+220
237	+220
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SL Cells
The sludge cells produce higher TKN concentrations than either SW or
SW-SL cells, although the difference is not great (see Table 13). Con-
centrations decline much more slowly with time than either SW or SVJ-SL
eel 1s.
Statistical Analysis
SW -- Averages and effects calculated for Years 2 and 4 are shown
below:
TKN (mg/L)	Ave	I	CI
Year 2	1,770	-830	+550
Year 4	330	-295	+100
Increasing infiltration substantially reduces leachate concentrations. For
Year 4, the concentration at low I (330 + 295/2) is more than twice as
great as at high I (330 - 295/2).
SVI-SL -- Averages and effects for Years 2 and 4 are shown below:
TKN (mg/L)	Ave T IP Txl TxP IxP CI
Year 2, 10-20 1,240 260 -680 120 50	-20 +190
, 20-30 1,550 380 -940 510 -250	-240 +190
Year 4, 10-20 584 -8 -470 162	110	+50
, 20-30 702 54 -560 74	-46	+50
Of the main effects, the largest and most consistent is infiltration-
concentration is consistently decreased by increased infiltration.
TKN concentration is higher for cells containing LT sludge (The T-effect),
and increased percent sludge (P) increases TKN concentration. Interactions
are not consistently observed.
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SL -- Averages and effects for Years 2 and 4 are shown below:
TKN (mg/L)
Ave
T
H
CI
Year 2
2,920
468
272
+135
Year 4
2,410
180
495
+334
For Year 2, sludge type (T) and cell height (H) show significant effects.
For Year 4, only sludge height shows a significant effect. The large
confidence interval for Year 4 indicates substantial disagreement
between duplicates.
Volatile Acids
SW
The average annual volatile acid concentrations for various cell
groupings are presented in Table 13. The SW cells show high concentra-
tions for the first two years which drop to a low value by Year 4.
As noted earlier (see section on pH), the volatile acid concentration
drops precipitously in the same month that pH abruptly increases,
anaerobic processes commence, and methane is produced.
SW-SL Cells
Volatile acid concentrations drop sooner for SW-SL cells than for
SW cells, and reach lower levels. Average concentrations during Years
2 and 3 average 7,500 mg/L lower in volatile acid concentrations for
the SW-SL cells. In Year 4. the volatile acids for both SW and SW-SL
cells average less than 500 mg/L.
SL Cells
Volatile acid concentrations for the AO cells are substantially lower
than for all other cells. Volatile acid concentrations from the LT cells
start out at the same level as for the SW-SL cells but drop much more
slowly. Anaerobic action apparently started in one LT cell (No. 22--
see section on pH) at about Month 36. Volatile acid concentrations dropped
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from the 6,000 to 18,000 mg/L range to the 100 to 300 mg/L range. The
other LT cells (No. 24 and 26) continued a steady drop with time from
values around 10,000 mg/L in Year 3 to around 2,000 to 6,000 mg/L in Year
4 but did not experience either a rapid pH or volatile acid concentration
change.
Statistical Analysis
Volatile acid concentrations were characterized by wide swings in
successive monthly measurements. Annual averages for Year 4 where conditions
should have stabilized nevertheless showed large discrepancies between
duplicates. Standard deviation for cell groupings are shown below:
Cell

Ave
Std. dev.
Number of
SW
17,18,19
113
12
3
SW
20
1,490
—
1
SW-SL
All
170
98
16
SW-AO
All
282
120
4
SL-LT
22
116
--
1
SL-LT
24,26
5,910
5,400
2
The inconsistencies in concentrations of some cells within cell groupings
made it inappropriate to carry out any other statistical calculations.
Cadmi um
SW Cells
Annual average leachate concentrations for various cell groupings are
shown in Table 14. All cells showed erratic concentrations during the
first year. For the SW cells, concentrations diminish greatly with time--
average concentration in Year 4 is one-tenth the concentration in Year 1.
There appeared to be no short period of rapid decline in concentration
that coincided with the abrupt pH rise or COD drop that occurred in the
cells.
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The rate of decline in concentration with time was much greater than
was experienced by chloride. It appears that as the test cells age, the
changing conditions (e.g., oxygen, volatile acids, and COD concentrations
fall, and pH increases) cause a reduction in solubility of cadmium.
SW-SL Cells
The fall in leachate concentrations from the SW-SL cells parallels
the behavior in the SW cells. Average concentrations are nearly the
same.
SL Cells
In Year 1, sludge cells show leachate concentrations about 50 percent
higher than from the SW and SW-SL cells. The concentration for the AD
cells fall almost as fast as for these cells, whereas the concentration
from the LT cells falls much more slowly, dropping to half their initial
value after 4 years.
Statistical Analysis
SW -- Averages and effects for Years 2 and 4 are shown below:
Cd (mg/L)	Ave	I	CI
Year 2	0.029 -0.012 +0.024
Year 4	0.0045 -0.002 +0.003
There is a small consistent reduction in concentration caused by infiltra-
tion, but it is much smaller than the confidence intervals and thus is
not significant.
SW-SL -- Average and effects for Years 2 and 4 are shown below:
Cd (mg/L)	Ave T	I	Txl CI
Year 2, 10-20 0.017	+0.005
, 20-30 0.019	-.007 -.007 +0.005
Year 4, 10-20 0.0032	+0.0035
, 20-30 0.0032	±0.0035
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In Year 2, infiltration and an interaction of sludge type shows up as
a significant effect. No effects are significant in Year 4.
SL -- Averages and effects for Years 2 and 4 are shown below:
Cd (mg/L)	Ave T	I	Txl CI
Year 2	0.042 0.034 0.008 0.008 +0.009
Year 4	0.017 0.020 0.014 0.012 +0.022
In Year 2 there is a large and significant effect of sludge type. There
is nearly significant interaction of sludge type and cell height. The effects
are similar in direction in Year 4 but they are not statistically significant.
Chromium
SW Cells
Average annual concentrations for various cell groupings are presented
in Table 14. Concentrations decline with time. Concentrations compared
to chloride are shown below:
Year	12	3	4
Cr/Cl x 104 0.92	0.72	0.53	0.43
Chromium declines more rapidly than chloride. One likely explanation for
this behavior is that chromium originally soluble is being precipitated
within the cell as conditions within the landfill change with time.
SW-SL Cells
Average concentrations of the leachate from the SW-SL cells start
out lower than for the SW cells, but decline at a slower rate. The
Year 4 average is slightly higher than for the SW cells.
SL Cells
Average concentrations from the sludge cells are lower than from
either SW or SW-SL cells. However, they decline only about 20 percent
over the four years and end up about twice as high as for the other cells.
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Statistical Analysis
SW -- Averages and effects of Year 2 and 3 are presented below:
Cr (mg/L)	Ave	1	CI
Year 2	0.096 -0.020 +0.032
Year 3	0.042 (s = 0.014)
Results indicate no significant effect of infiltration. Effects and
confidence interval were not calculated for Year 3 because the average
chromium value for one of the cells (cell 19) did not drop significantly
during the third year. Interestingly, in Year 4, its behavior returned
to normal.
SW-SL -- Averages and effects for Years 2 and 3 are presented below:
Cr (mg/L)	Ave T	I Txl TxP U
Year 2, 10-20 0.051	-0.017	0.015 +0.010
, 20-30 0.047 0.016 -0.017 -0.018	+0.010
Year 3, 10-20 0.030	+0.007
, 20-30 0.028	+0.007
Increased infiltration caused a significant reduction in Year 2. Other effects
and interactions may be significant. In Year 3, no effects were significant.
SL -- Averages and effects for Years 2 and 3 are presented below:
Cr (mg/L)	Ave T	H TxH	CI
Year 2	0.062 0.025 0.009 0.017 +0.010
Year 3	0.048 0.032 0.017 0.011 +0.010
Sludge type and cell height and their interaction have consistent and
significant effects in both years.
Copper
SW Cells
Annual average leachate concentrations for various cell groupings are
presented in Table 14. Copper concentrations showed a gradual decline
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with no sudden perturbations related to pH or COD. Concentrations are
compared to CI below:
Year	1	2	3	4
Cu/Cl x 104	0.29	0.32	0.38	0.27
Since the ratios are about the same, copper concentrations decline at about
the same rate as chloride.
SW-SL Cells
Concentrations are slightly lower from the SW-SL cells in the first
year and practically identical to results from the SW cells after 4 years.
5L Cells
Overall annual average leachate concentrations from the sludge cells
start at the same level as for the SW and SW-SL cells but fall more slowly.
The AD and LT cells show different behavior. The concentrations from the
SL cells decline regularly, although not much in Years 2-4. The leachate
from the LT cells appears to go through a maximum between the second and
third year.
Statistical Analysis
SW -- Averages and effects for Years 3 and 4 are presented below:
Cu (tng/L)	Ave	I	CI
Year 3	0.030 -0.007 +0.017
Year 4	0.012 - .005 +0.009
A reduction in concentration caused by increase in infiltration rate
is evident in both years. However, the effect is not statistically
significant.
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SW-SL -- Averages and effects for Years 3 and 4 are presented below:
Cu (mg/L) Ave	I	CI
Year 3, 10-20	0.026	+0.003
, 20-30	0.026	+0.004
Year 4, 10-20	0.0126	-0.008 +0.004
, 20-30	0.0125	-0.006 +0.004
Year 3 showed no significant effects. Cell 10 in Year 3 produced an
unusually high leachate concentration (approximately double the average)
and was replaced with an estimated value that minimized interactions.
This same cell produced high lead readings (see section on lead). This
anomalous behavior disappeared at Year 4. In Year 4 a significant but
small effect of infiltration was evident.
SL -- Averages and effects for Year 3 are presented below:
Cu (mg/L)	Ave	T	H	TxH	CI
Year 3 0.051 0.039 0.014 0.015 +0.011
Year 4 0.036 (s = 0.025)
Year 3 shows a significant effect of sludge type, infiltration, and their
interaction. Year 4 data cannot be used to calculate effects because
one cell (cell 22) produced an effluent average concentration one-third
of the annual average. Since one sludge cell (No. 28) had already
failed, only the annual average and standard deviation of the cells
could be determined. Results with and without Cell 6 are shown below:
7 (6 cells) = 0.042 (s = 0.024)
7 (7 cells) = 0.036 (s = 0.025)
The result indicates considerable scatter even without Cell 6.
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Iron
SW Cells
Annual average leachate composition for various cell groupings are
presented in Table 14. The SW cells show high leachate concentrations for
the first two years that are reduced by a factor of 20 by Year 4. As,
noted earlier (see pH), the fall in concentration is associated with the
coincident increase in pH and commencement of anaerobic processes that
generate methane. The fall in iron concentration with the onset of
anaerobic conditions and pH change is shown in Figure 19.
SW-SL Cells
The SW-SL cells start out lower in leachate iron concentration and
reach lower concentrations than the SW cells. LT sludge seems to produce
a higher iron concentration in Year 1 and lower concentrations in subsequent
years.
The AD cells have leachate concentrations similar to the SW cells
until Year 4 when the AD cells appear to be leveling off at a higher concen-
tration than the SW cells. The LT cells show very low iron concentration
relative to all other cells. All of these LT cells were at a much higher
pH than the other cells which is doubtlessly the reason for the low iron
concentrations. Comparison of average pH and average iron concentration
for the LT cells for Year 4 supports this conclusion.
SL Cells
Cell
Ave pH
Ave Fe (mg/L)
8.2
1.9
2.1
22
7.5
24
10.6
26
9.3
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Iron concentration is highest and pH lowest for Cell 22. As noted earlier
(see section on COD), this was the only LT cell to commence rapid biological
action.
Statistical Analysis
SW -- Averages and effects for Year 4 are given below.
Fe (mg/L)	Ave	I	CI
Year 4	77.5	89	_+19
Year 3 is not considered because anaerobic conditions with accompanying pH
and COD changes had not occurred in all cells. Increased infiltration
increased the concentration of iron and the effect was statistically signi-
ficant. This unusual effect of infiltration may be the effect of a pH
change. Checking average pH of the low and high infiltration cells for
Year 4 shows the following:
Infiltration	Ave pH
Lo (Cell 17, 19)	6.96, 7.06
Hi (Cell 18, 20)	6.73, 6.49
As expected, the high infiltration rate cells, which have the highest iron
concentration in leachate, show the lowest pH's.
SW-SL -- Averages and effects for Years 3 and 4 are shown below:
(mg/L)

Ave
T
I
P TxP
CI
Year 3,
10-20
35
-14
8
- 8
+ 7
»
20-30
41
-34
8
11 -11
+ 7
Year 4,
10-20
39
- 8
18
-11
+12

20-30
40
-24
11

+ 12
The effect of sludge type (LT decreases iron concentration) is large and
significant. Increase in infiltration rate significantly increases con-
centration, probably because it reduces pH. A similar effect was noted
for the SW cells (see above). Interactions are large (TxIxP interaction
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was large as well) but not consistent. The effects are probably "noise"
in the data, which reduces confidence in the conclusions.
SL -- The magnitude of the differences between concentrations in AD
and LT cells (see Table 12) make it best to divide the experiment into
an AD and LT part. For the LT cells, Cell 22 behaved anomalously in
Years 3 and 4 so no calculation of value can be made. For AD cells,
agreement between replicates was poor and gave confidence intervals too
large to show any effects. Only averages of the AD cells and standard
deviations are shown below:
Fe (mg/L)	Ave
Year 3	311 (s = 18)
Year 4	287 (s = 75)
Lead
SW Cells
Average annual concentrations of various cell groupings are presented
in Table 14. Average concentrations fall with time. The ratio of Pb/Cl
average concentration for Years 1-4 is shown below:
Year	12	3	4
Pb/Cl x 104	1.94	1.75	0.8	0.98
Pb concentrations fall at a slightly higher rate than CI.
SW-SL Cells
Average concentrations are consistently about 20-40 percent lower
than for SW cells, although the proportionate drop with successive
years is very similar.
SL Cells
The average concentrations in the sludge cells start out at about
the same level as for the SVI and SW-SL cells, but they fall at a much
lower rate in successive years.
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Statistical Analysis
SW -- Average and effects for Years 2 and 4 are shown below:
Pb (mg/L)	Ave	I	CI
Year 2	0.23	-0.06	+0.02
Year 4	0.52	-0.015	+0.022
There is a consistent effect (reduction) caused by infiltration. The effect
is statistically significant in Year 2 but not in Year 4.
SM-SL -- Averages and effects for Years 2 and 4 are shown below:
Pb (mg/L)	Ave	B	CI
Year 2, 10-20 0.115 -0.028	+0.017
, 20-30 0.120 -0.038	+0.017
Year 4, 10-20 0.042 -0.014	+0.018
, 20-30 0.046 -0.026	+0.018
There is a consistent reduction of leachate concentration caused by infiltra-
tion. The effect is statistically significant in all but one case. The
preponderant evidence is that the effect is significant.
One cell (cell 10) showed an anomalous concentration for Year 2, about
twice its expected value. It was replaced in the calculation with a value
that minimized second and third order interactions. The measurement for
Cell 10 was anomalous but not an error (the 12 measurements making up the
average showed an unmistakable high trend). It should be recognized that
trace element concentrations in leachate cells can be completely upset by
location of a concentrated source of that trace element (e.g., a discarded
lead storage battery).
SL -- Average and effects for Years 2 and 4 are shown below:
Pb (mg/L)	Ave	T	H	TxH	CI
Year 2	0.34 0.25 0.12 0.06	+0.05
Year 4	0.22 0.24 0.12 0.08	+0.09
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Effects are almost identical for the two years. The main effects are
statistically significant and the interaction is probably significant.
Ni ckel
SW Cells
Annual average leachate concentrations for various cell groupings are
presented in Table 14. Concentrations show the usual decline with time.
Results are compared to chloride below:
Year	1	2	3	4
Ni/Cl x 103 0.42	0.45	0.44	0.48
Since the concentration ratio is nearly constant, nickel evidently declines
like chloride.
SW-SL Cells
The concentrations from the SW-SL cells are initially half as much as
the SW concentrations but by Year 4 they are nearly equal.
SL Cells
Concentrations from the SL cells are about the same as from the SW
cells initially but decline at a lower rate.
Statistical Analysis
SW -- Averages and effects for Years 2 and 4 are shown below:
Ni (mg/L)	Ave	I	CI
Year 2	0.60	-0.16	+0.59
Year 4	0.22	-0.12	+0.09
Poor agreement between duplicates caused the confidence interval to be
high for Year 2. The effect of infiltration rate cannot be considered
significant. For Year 4, the effect of infiltration is seen to be
significant.
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SU-SL -- Average and effects for Years 2 and 4 are shown below:
Ni (mg/L)	Ave I	CI
Year 2, 10-20	0.21	-0.06	+0.07
, 20-30	0.24	-0.11	+0.07
Year 4, 10-20	0.18	-0.05	+0.04
, 20-30	0.18	-0.07	+0.04
The effect of infiltration shown for Year 2 is significant. For Year 4
the effect appears significant. However, all other effects and interactions
for Year 4 ranged from 0.02 to 0.05 (several exceeded 0.04 but are not
shown). This kind of behavior indicates too much "noise" in the data
despite the relatively small confidence interval. Evidence thus is not
conclusive that the infiltration effect is significant for Year 4.
Zinc
SVJ Cells
Average annual leachate concentrations for various cell groupings are
presented in Table 14. Concentrations are initially low, rise to a peak
in the second year and drop to a low value by Year 4. The drop after the
second year is due to the onset of anaerobic processes producing methane
and/or the accompanying pH elevation that occurs at this time. The rise
in concentration with time is illustrated in Table 14 for Cells 19 and 20,
which did not produce methane until about the 35 and 38 months, respectively.
A possible explanation for the unusual rise in concentration is a gradual
dissolution of metallic zinc in the refuse by the acidic leachate. Zinc
concentration increases in the innumerable small reservoirs in the refuse
mass and does not drop until the rise in pH (at about 30 to 36 months for
Cell 20) or the change in oxidation-reduction potential reduces its
solubi1ity.
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SU-SL Cells
The concentration of zinc in the leachate from the SW-SL cells is far
lower than from the SW cells for Years 1 to 3, but it is approximately the
same in Year 4. The reason for the low values in the early years is the
early onset of anaerobic activity with its accompanying change in pH and
oxidation-reduction potential in the SW-SL cells.
SL Cells
Zinc concentration is lower in the sludge cells than in the SW and
SW-SL cells initially and remains low through Year 4. In Year 4, all
cells have approximately the same zinc concentration in the leachate.
Statistical Analysis
SW -- The effects of pH changes in the four SW cells were not complete
until the start of the fourth year of the experiment. Consequently effects
and averages are only determined on averages of the last 9 months of the
experiment.
Zn (mg/L)	Ave	I	CI
Months 40-48 0.064 -0.050	+0.066
Increase in infiltration rate lowers concentration in the leachate but the
effect is not statistically significant.
SW-SL -- Averages and significant effects are shown below for Years 3
and 4.
(mg/L)
Ave
T
I
P
Txl
TxP
CI
Year 3, 10-20
0.10
0.04
-0.04



+0.023
, 20-30
0.13
0.03
-0.014
0.07
-0.06

+0.023
Year 4, 10-20
0.13

-0.12
-0.09

0.09
+0.033
20-30
0.09

-0.05



+0.033
Sludge type has a significant effect in Year 3 but not Year 4. This is not
surprising because the effect is not great and effects of sludge type would
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be expected to disappear with increasing age of the test cells. The effect
of infiltration is significant and consistent through all sludge addition
ranges and years. Increased infiltration rate reduces zinc concentration in
the leachate.
SL -- Averages and effects are shown for Year 4. Only average and
standard deviation are shown for Year 3 (without Cell 28} because agreement
between duplicates is poor.
Zn (mg/L)	Ave	I H TxH	CI
Year 3 0.15 (s = 0.10)
Year 4 0.13	0.08 0.04 0.08 +0.05
In Year 4, LT sludge increases zinc concentration in the leachate. Height
has an effect which is not significant. The interaction of sludge type and
height is significant.
Priority Pollutants
The analyses for priority pollutants showed extremely erratic behavior.
Concentrations in leachate from spiked cells were no greater than from
unspiked cells. Although the data have not been exhaustively evaluated,
it appears that the effects of differences between cells or unreliability
in the analytical method mask the effects of the experimental variables
(sludge type, infiltration rate, and percent sludge in the co-disposal test
cells, height in the sludge cells).
Part of the problem may be due to analytical method development that
occurred during the experiment and to the nature of the changes that
occurred in the leachate with time. The method of extraction used on the
leachates was one utilized for sludges (18). However, the liquid phase of
sludges is not normally as heavily contaminated with interfering substances
such as volatile acids as is a high strength leachate. Much difficulty was
encountered in getting adequate separation of the contaminants from
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leachates. Minor changes in techniques improved this extraction as the
experiment progressed. The substantial drop in volatile acids that occurred
in all cells containing refuse probably influenced recoveri.es by eliminating
interfering substances, introducing a time-dependent factor on the accuracy
of the measurements. Midway through the experiment, the analytical task
was transferred from one contractor group to the other, introducing an
irregularity between Years 1 and 2 and 3 and 4.
Some useful information can be salvaged from the extensive data col-
lected. Table 15 shows the average annual readings for selected cell
groupings. Clearly, several compounds continue to appear in about the
same concentrations in Year 4 as in Year 1 (acenaphthene, naphthalene)
whereas others drop to low values (Arochlor 1254, di-n-butylphthalate).
The reason for the drop is not necessarily that the compound has decom-
posed. For example, Arochlor 1254, which is a highly chlorinated PCB,
very likely has not been broken down. The organic content of the
leachate has dropped by a factor of 30 to 100. The presence of such
substances in water greatly enhances its ability to dissolve otherwise
insoluble organic compounds. Consequently, their absence could explain
why the concentrations of some priority pollutants decline with time.
In examining the data in Table 15 to see whether there is a trend
towards lower leachate concentrations, it is best to focus on Years 3 and
4 where possible because interference from soluble COD is minimized, the
analytical laboratory is the same, and the method better developed. The
priority pollutants were ranked to estimate likelihood that the pollutant
would soon be undetected in the leachate by calculating the ratio of
average composition of Year 4 to Year 3 (see Table 16). A ranking of 1
indicates that the compound shortly will not be found in the leachate,
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a rank of 3 indicates the chemical will not diminish, and a rank of 2
is intermediate. The SW cells have the lowest overall ranking. The
SW-SL and SL cells are about the same. SL cells have more l's but also
more 31s.
The "percent detected" was determined for the analyses carried out in
Year 4 and are also shown in Table 16. Agreement between the two ranking
schemes is good. Low "% Dectected's" correspond to low rank. The
cumulative average ranks show SW cells with lower reading by both schemes.
Gas Production and Methane Content
SW Cells
Annual average gas production and methane content over the four year
period of the experiment are presented in Table 17 for various cell groupings.
The SW cells generate little gas in the first year and it is of low methane
content. Average gas production and methane content are highest in the
fourth year.
SW-SL Cells
Examination of Table 17 shows that for SW-SL cells, gas production was
high the first year, peaked in Year 2 and fell gradually in Years 3 and 4.
Average production over the four years is higher for the SW-SL cells than
for the SW cells, but the SW cells had not yet reached a declining gas
production stage at the end of the experiment.
Cumulative gas production can be determined by multiplying average
hourly rate by 31,360 hours (gas was measured for 3.58 years). Gas
production for all cell groupings per unit mass of dry solids in the cells
is shown below for all cell groupings:
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sw
liters/kg	Est. Dry Mass Loss (%)
135	17
SW-SL
180
22
SL-AD
87
11
SL-IT
39
5
According to EPA's Sludge Process Design Manual (20), gas production
per pound of volatile solids destroyed when crude fiber is anaerobically
digested is 13 ft3 (50 percent methane) or 810 liters/kilogram. Mass
loss is estimated in the above table by comparing actual gas production
to this figure. The percentage loss is substantial for SW and SW-SL.
SW cells show less mass loss but, as noted earlier, they were still pro-
ducing gas at a relatively high rate at the termination of the experiment.
Gas production in the AD cells is a maximum in the first year and
declines steadily thereafter. For the LT cells, gas production is low
in Years 1, 2, and 3 but increases in Year 4. Methane content of the gas
produced in the LT cells is low until Year 4.
The table in the preceding section shows that the AD cells have produced
relatively little gas in proportion to their mass. This is an expected
result because the sludge was already digested. The LT sludge producd even
less gas, although results previously discussed indicate that eventually
all LT cells will produce gas. Such a sludge if digested would be
expected to lose almost half of its volatile solids and would lose an
estimated 30 percent of its total mass.
Statistical Analysis
SW — The SW duplicates showed substantial disagreement so no estimate
of the effect of infiltration could be determined. Since the cells were
SL Cells
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still producing gas at a substantial rate, no estimate beyond that shown
in Table 17 is appropriate.
SW-SL -- The average gas production over the four year experiment
(measurements every other month for 3.58 years) is proportional to total
gas production. Average (L/hr) and effects of experimental variables
for the SW-SL are shown below:
Effects
10-20%
20-30%
T
-0.1
0.6
I
0.2
0.2
P
-0.5
-0.6
Txl
0.1
0.4
TxP
0.7
0.0
IxP
0.1
-0.1
TxIxP
1
o
•
00
1.0
CI
+1.0
+ 1.0
Ave
7.4
6.8
The confidence interval is relatively large so all but one effect are
not significant. The significant effect is the TxIxP interaction which is
nearly significant for the 10-20 percent experiment and significant for the
20-30 percent experiment. This effect is confounded with elevation, -E
for the 10 to 20 percent experiment and +E for the 20-30 percent experiment.
The change in signs is consistent with an increase in gas production at the
higher elevation where temperature is slightly higher (1.8°C). The higher
temperature would cause only a slight volume increase due to gas expansion
(about 1 percent). However, it is reasonable to think that biological
activity could be increased by about 14 percent (E-effect * average) by
the higher temperature.
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Art increase in Percent Solid (P) shows a consistent effect—gas volume
is reduced—although the effect is substantially less than the 95 percent
significance level. For AD sludge at least, this kind of an effect is
anticipated because the AD sludge has already been digested.
SL — The LT data are not considered because of the erratic conditions
one cell bad (No. 28), and only one of the 3 remaining cells (No. 22)
producing gas. Before considering the AD cells, the gas production was
normalized by dividing gas production by dry mass—gas production would be
expected to be related to dry mass. Averages (1iters/hr-kg) and the effect
of height are shown below.
Average (1iter/hr-kg)	H	CI
2.51 x 10"3	0.34 x lO-3 +0.28 x 10"3
The tall cells evidently produce slightly more gas. The effect is signi-
ficant .
Temperature
Average annual temperatures in the interior of the cells and of the
cell leachates are shown in Table 17 for the SW and SW-SL cells at the
upper and ground levels and for the SL cells, which were all at the
ground level. Average temperatures of cells and leachate and differences
between the two levels agree well except for Year 4. The cell tempera-
tures are about 2°C lower than leachate temperatures for an unknown
reason.
Statistical Analysis
Statistical analysis of temperature or elevation effects was only
carried out for the SW-SL cells. The effect of experimental variables
on temperature was investigated for Year 1. Averages and effects are
shown below:

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Temperature (°C)	Ave	TxIxP	CI
Year 1, 10-20 23.8	-1.6	+0.44
, 20-30 22.6	+1.7	+0.44
The TxIxP is confounded with the -E (elevation) effect for the 10-20
percent case and with +E for the 20-30 percent case. It is assumed that
the three-factor interaction is insignificant. Consequently TxIxP
measures the effect of elevation. The effect is clearly significant
and an increase causes a temperature increase of about 1.6°C.
The effect of elevation (actually, temperature effects) was found to
be significant for some parameters. Results are summarized in Table 18.
The effect for cadmium is probably not real--it is not consistent in Year 2
and disappears in Year 4. The higher temperature at the higher elevation
appears to significantly increase alkalinity, phosphate, pH, and gas
production. Iron concentration in leachate is reduced by the temperature
increase.
DISCUSSION
General
The most notable finding of the study is the generally advantageous
effect of including sewage sludge in the landfill. The mechanism is
clear. Anaerobic decomposition occurs much earlier when sludge is present
in the landfill. Carbonaceous materials in the leachate are converted
to methane and carbon dioxide, reducing their concentrations by large
factors. The increase in pH that occurs when anaerobic processes commence
causes some metals ordinarily dissolved by acid leachates to prscipitate.
Results contrast but do not conflict with the EPA study summarized
by Pohland and Harper (14). At temperatures averaging 10°C and under
conditions that allowed air to enter the simulated landfills, addition
of sludge did not reduce leachate strength. Rapid anaerobic biological
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activity did not commence in over ten years. The importance of operating
a landfill in a manner that excludes air becomes evident.
Another notable aspect of the study is the stability of the results.
Only one test cell (fortunately duplicated) consistently produced aberrant
results. Typically it is extremely difficult to make comparisons within a
given set of lysimeters filled with the same waste because of uncertainty
that they are similar in all features except for the variable being
evaluated. In this experiment, ten conditions were duplicated. For nine
of these sets, agreement was generally within reasonable bounds. For
virtually all parameters measured, the calculated effects of experimental
variables have been consistent from year to year. The results from the
set of SW-SL cells for 10-20 percent sludge addition gave results
consistent with those obtained for the 20-30 percent addition cells.
There have been a few instances, particularly with lead and chromium,
where a single cell shows abnormal concentrations for a period of time.
Such effects are inevitable, particularly for metals. It is impossible
for test cells of any reasonable size to be "representative" for all
substances that are disposed to landfills. For metals, for example,
small amounts are discarded in highly concentrated soluble forms
(for example, zinc chloride soldering paste, ferric chloride for
fertilizer use). There might have been a dozen of such "surprises"
in the batch of garbage used to charge our test cells. There is no
way they can be distributed evenly among 20 test cells. In the pre-SBR
stage of the landfills, they could have an enormous effect on concen-
traions normally measured in milligrams per liter. It is surprising
that in our sludge, such aberrant conditions were so rarely met.
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Particular
Leachate Quantity
The leachate quantity results show one of the advantages of disposal
of sludge in a codisposal landfill rather than a sludge "monofill."
Leachate lags behind infiltration for about a year (depending on infil-
tration rate) whereas for the sludge landfill the situation is reversed.
It should be remembered, however, that for the sludge landfill, even
though leachate leads infiltration, the amount per year is low because
infiltration water penetrates through the sludge slowly. If, for
example, total COD rather than COD concentration is of concern, impact
may be less for the sludge landfill because leachate volume will be
less.
The slow penetration of infiltration water through a sludge landfill
reduces leachate volume but creates other potential problems. The cover
of the landfill must be well sealed to reduce infiltration, otherwise,
the site may not lose water fast enough and will become a swamp.
Final Solids Content
Equilibrium solid contents show that up to 20 percent sludge in
a landfill does not seriously affect the ability to retain water. In
excess of 30% sludge reduces the absorptive capacity substantially.
Adding more than 30 percent sludge becomes unwise for other reasons
as well, most notably because the presence of a large amount of semi-
solid sludge creates unpleasant and hazardous conditions for workers.
The 15 percent solids sludge applied in the landfill dewatered
to 19.1 percent solids for AD sludge and 23.5 percent solids for LT
sludge (averages for the short and tall cells). If the sludge had been
dewatered in-itially to these levels by using a more efficient dewatering
device, the cells would have lost no net water. These devices are
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available today. For example, belt filters generally achieve solids
content in the range of 20-25 percent.
The results of the investigation do not provide information on the
effect of pressure created by a soil cap or deep landfills. This
effect could be particularly significant for the sludge landfills because
there is so much water present which might become available. The
results for sludge should not be extrapolated to substantially deeper
landfills than the tall cell sludge depth (1.5 m).
Parameters Affected by RBS
The leachate contaminants can be separated into parameters sharply
affected or not sharply affected by the onset of rapid anaerobic bio-
logical stabilization (RBS). Parameters which declined sharply were
leachate concentrations of COD, volatile acids (VA), TOC, volatile
and total solids (VS and TS), iron, phosphate, and zinc. The pH rose
sharply by about 1.0 unit. For COO, VA, TOC, VS, and TS, the overriding
influence was whether RBS had occurred. Concentrations were drastically
reduced by this transition. This is in accord with our knowledge of
what occurs in anaerobic biological stabilization. These substances
are consumed. Soluble organic substrates are reduced to simpler forms
and eventually converted to methane and carbon dioxide.
For phosphate, iron, and zinc, the mechanism of removal is pre-
cipitation which is related probably primarily to pH but also to con-
centration of organic substances that can complex with these substances
and hold them in solution, and to the oxidation-reduction potential.
Iron concentration appears to be strongly influenced by pH. Concen-
tration falls dramatically in the SW and SW-SL cells when the pH change
associated with RBS occurs. It is in high concentration in the leachate
from the SL-AD cells even though the sludge is in a post-RBS stage.
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It declines in this leachate with the rise in pH that occurs with time.
In the SL-LT cells, it is present in low concentrations even in the
pre-RBS stage because pH is high. Phosphate drops in the SW and SW-SL
cells but not to as low a level as might be expected considering the
amount of iron in solution. Phosphate is at low levels in the SL cells,
probably because of high pH in IT cells and high iron levels in AD cell
leachates. Zinc only fell dramatically in 3 SW cells and one SW-SL cell
where its initial concentration was unusually high. The drop appears to
be related to pH.
Parameters Not Affected by RBS
Factors not noticeably affected by RBS were chloride, alkalinity,
TKN (total Kjeldahl nitrogen), cadmium, chromium, copper, lead, and nickel.
Chloride is a highly soluble ion that is not consumed or precipitated
in the landfill reactions. The leaching behavior of other substances
has been compared against it to assess their fate in the landfill. The
heterogenous nature of the landfill may partially invalidate this pro-
cedure (chloride may not be concentrated in the landfill in the same
locations as the substances it is supposed to trace), so the concept
should be used with caution.
Alkalinity and TKN are soluble substances that will not precipitate
in landfills. However, they can increase or decrease depending on the
biological activity in the landfill. Comparisons for the SW and SW-SL
test cells show that except for TKN for the SW landfills, their leachate
concentrations relative to chloride are constant with time, showing that
they are behaving like chloride. This unusual behavior requires more
consideration, because one would expect both TKN and alkalinity to be
produced by the anaerobic activity in the landfill. They should not
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leach out in the same manner as a soluble contaminant with a fixed
initial concentration.
The behavior of most of the metals is similar. Cadmium, chromium,
copper, and lead decline at a rate substantially faster than chloride.
This indicates conditions in the landfill are changing with time and are
precipitating these metals. The ever-continuing reduction in COD and
volatile acids with time reduces the amount of organic complexing agents,
chloride (another complexing agent) is declining with time, and pH is
generally rising towards neutrality. The exact cause of the decline
cannot be identified from our results. Nickel is the only metal that
declines like chloride. It appears that the changing conditions that
occur with time do not reduce nickel solubility.
Production of Gas
The production of gas is significant for all landfill types except
for the lime-treated sludge. Although the calculated amount of organic
material consumed by conversion to gas is considerable, much potentially
biodegradable material remained undecomposed. There may be some utility
to injecting sludge into a landfill to start gas production or revive
it after it has declined.
Organic Priority Pollutants
The measurements of organic priority pollutants indicated that, after
four years, pollutant concentrations in leachates were slightly lower from
the SW cells than from the SW-SL or SL cells. Data are not reliable enough
to develop firm conclusions. The inability to detect the influence of the
spike of priority pollutants even in the leachate from cells containing
only sludge is puzzling. Eventually we plan to open the sludge cells and
analyze them to determine how much of the priority pollutants remain.
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Comparison of Landfill Types
Questions of importance are: "Does addition of sludge degrade the
leachate from a solid waste landfill?" and "To minimize net potential
groundwater degradation, is it better to put sludge in a solid waste
landfill or in a sludge landfill?". Results of this investigation show
that sludge addition reduces total organic discharge substantially in
the early years of operation. Examination of the concentrations of
metals shows that, generally, sludge addition lowers initial leachate
concentrations and that after several years concentrations are essentially
the same. The evidence is conclusive that, if the landfill is well
designed and would ordinarily become anaerobically active after two or
three years, sludge addition not only will not degrade the leachate but
will greatly reduce contaminant levels.
Sludge appears to reduce pollutional impact from solid waste landfills
so if possible it should go in these landfills. However, sludge landfills
for anaerobically digested sludge produce a relatively small impact. The
only serious problem is somewhat elevated nitrogen levels in the leachate.
The landfilling of lime-treated raw sludge creates a source of organic
pollution for many years and leaches nitrogen at somewhat elevated levels
as well. It produces lower concentrtions of some metals and higher con-
centrtions of others. Considering its higher adverse effects than AD
sludge, there is more motivation to put LT sludge in a solid waste landfill,
where it has a net beneficial effect.
CONCLUSIONS .
1) The presence of sludge in simulated solid waste landfills protected
from incursions of air reduced by about two years the time before rapid
anaerobic biological stabilization (RBS) commenced. The onset of RBS
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reduced chemical oxidation demand (COD) of the leachate by a factor of
20. Consequently, for two years, landfills containing sludge produced
leachates containing far less in COD than did landfills without sludge.
Anaerobically digested sludge and lime treated raw sludge produced the
same result.
2)	Simulated landfills containing only anaerobically digested sludge
(SL-AD) had leachate strengths comparable to solid waste-sludge landfills
after the commencement of RBS, except nitrogen concentrations were sub-
stantially higher. Leachates from test cells containing lime-treated
raw sludge (SL-LT) were similar to leachate from solid waste (SW) or
solid waste-sludge (SW-SL) cells before the onset of RBS. All SW and
SW-SL test cells achieved RBS within about three years. After 4 years,
one out of three SL-LT test cells achieved RBS.
3)	Solid waste landfills absorbed infiltration water so leachate
flow lagged behind infiltration by about a year. Adding sludge cake up
to 30 percent by volume reduced the lag but not seriously. For sludge
landfills originally at 16 percent solids, leachate exceeded infiltra-
tion. Equilibrium occurred at 19 percent solids for AD sludge and
24 percent solids for LT sludge.
4)	Many parameters underwent abrupt changes in a period of 1-2 months
with the onset of RBS. The pH increased about 1 unit. Chemical oxygen
demand (COO) and volatile acids (VA) dropped by a factor of 20 or more.
Phosphate, iron, and zinc concentrations dropped sharply. Final con-
centrations were similar and leachates from SW and SW-SL simulated
landfills.
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5)	In SW and SW-Sl simulated landfills, other parameters declined at
rates similar to the decline of chloride, a highly soluble and inert
substance in a landfill. These are alkalinity, TKN (total Kjeldahl
nitrogen), and nickel. All parameters were initially lower in leachate
from SW-SL cells but were at about the same level after 4 years.
6)	In SW and SW-SL simulated landfills, cadmium and chromium
declined substantially faster than the decline in chloride. Lead and
copper dropped more sharply than chloride but not as fast as these
metals. All four metals initially were lower in concentration in SW-SL
leachates but were at about the same concentrations after 4 years.
7)	In SL simulated landfills, concentrations for metals generally
were slightly higher than for SW and SW-SL landfills, and moderately
higher after 4 years, because concentrations did not decline rapidly.
8)	All test cells produced substantial amounts of methane-rich gas
relative to their dry mass except for the LT cells.
9)	Some priority pollutants continued to be found in the leachates
from the test cells after 4 years whereas others had fallen off to low
value. There were serious unexplained difficulties with the results,
such as the inability to find differences between the leachate of spiked
and unspiked cells. Resolution of inconsistencies awaits results of
analytical work on the sludge cells after they are opened.
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RECOMMENDATIONS
1)	It is a popular misconception that introducing sludge into landfills
degrades leachate quality. This study shows the reverse is true.
Results of this investigation should be made widely available to EPA
and state authorities concerned with landfill regulations to improve
the scientific basis of their decisions.
2)	More research on the effects of sludge in landfills is appropriate. The
test cells of the present invesigation should be opened and analyzed to
determine the fate of organic priority pollutants which had been added
to them.
3)	An experiment should be carried out to determine the effect of initial
moisture content, sludge type, height, and externally applied pressure
on leachate quantity from sludge landfills.
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Acknowledgment
This extensive and successful experiment is the end result of the
efforts of many people. The encouragement of Dr. C. A. Brunner to continue
this research long enough to obtain definitive results is greatly appre-
ciated. Planning of the work, scope was carried out by EPA staff members
G. K. Dotson, J. B. Farrell, Dirk Brunner, Norbert Schomaker, and James
Walsh of SCS Engineers. D. F. Bishop's recoiranendations on priority
pollutants and their analysis is also appreciated. EPA project officers
were G. K. Dotson, J. English, and J. B. Farrell. Dr. Barry Austern
provided priority pollutant analyses during the first two years of the
experiment.
The erection and construction of the test cells was carried out by
staff of the EPA Test and Evaluation Facility under direction of
Dr. A. Petrosek, following the test cell design of SCS Engineers, SCS
engineering staff supervising the project and preparing annual reports
were G. Vogt for the first two years and J. Stamm for the second two
years. J. Walsh of SCS was in overall charge of the project and is a
coauthor of the annual project reports. SCS Engineers' subcontractors
filled the test cells with solid waste (refuse) and sludge and carried
out the leachate analyses. Loading of the cells was planned and super-
vised by Dr. R. Kinman of the University of Cincinnati and analytical
activities were supervised by J. Rickabaugh. During the last two years
of the investigation, priority pollutant analyses were provided by PEI, Inc.
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Literature Cited
1.	Resource Conservation and Recovery Act of 1976, PL 94-580 (Oct. 21, 1976).
2.	Intra-Agency Sludge Task Force, U.S. EPA, "Environmental Regulations and
Technology: Use and Disposal of Municipal Wastewater Sludge,"
EPA 625/10-84-003 (1984).
3.	Lu, J. C. S., Stearns, R. J., Morrison, R. D., and Eichenberger, B. A.,
"A Critical Review of Wastewater Treatment Plant Sludge Disposal by
Landfilling," EPA 600/2-82-092, pub. Municipal Environmental Research
Laboratory, Cincinnati, OH (1982).
4.	Parkhurst, J. D., Landfill Disposal Demonstration Report Draft Report,
Los Angeles County Sanitation Districts, Los Angeles, California, 1978.
5.	Stone, Ralph, "Disposal of Sewage Sludge into a Sanitary Landfill,"
U.S. EPA, Cincinnati, OH (1974).
6.	Pickart, B. J., "Landfilling Milled Refuse Mixed with Digested Sewage
Sludge," M.S. Thesis, University of Wisconsin at Madison, 1974.
7.	Emcon Associates, "Sonoma County Solid Waste Stabilization Study,"
EPA SW 530 65D, pub. U.S. EPA, 1976.
8.	Johansen, 0. J., and Carlson, D. A., "Characterization of Sanitary
Landfill Leachates," Water Research _10 (10):1129-1134 (1976).
9.	SCS Engineers, "Investigation of Groundwater Contamination from Sub-
surface Sewage Sludge Disposal, Vol. 2, Case Study Reports,"
EPA 530/SW-167C, pub. U.S. EPA, 1978.
10.	Sweeney C. D., "Leaching Characteristics of Various Heavy Metals and
Anions from Municipal Sludge Ash," M.S. Thesis, University of Connecticut,
1978.
11.	Sikora, L. J., Murray, C. M., Frankos, N. H., and Welker, J. M.,
"Water Quality at a Sludge Entrenchment Site," Ground Water ^,6 (2):
125-132 (1978).
12.	Lund, L. J., Page, A. L., and Nelson, C. 0., "Nitrogen and Phosphorus
Levels in Soils Beneath Sewage Disposal Ponds," J. Environ. Qual.
_5 (1) :26-30 (1976)
13.	Ware, S.A., "A Study of Pathogen Survival During Municipal Solid Waste
and Manual Treatment Processes," EPA-600/8-80-034, pub. U.S. EPA
(Aug. 1980).
14.	Pohland, F.G., and Harper, S. R., "Retrospective Evaluation of the
Effects of Selected Industrial Wastes on Refuse Stabilization in
Simulated Landfills," Draft Report under review, Project Officer:
J. C. Herrmann, Hazardous Waste Engineering Research Laboratory,
Cincinnati, OH.
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15.	Kinman, R. N., Rickabaugh, J., Donnelly, J., Nutini, D., and Lambert, M.,
"Evaluation and Disposal of Waste Materials within 19 Test Lysimeters at
Center Hill," EPA 600/2-86-035, pub. Hazardous Waste Engineering Research
Laboratory, Cincinnati, OH.
16.	Stamm, J., and Walsh, J., "Fourth Annual Report: Pilot Plant Evaluation
of Sludge Landfilling," Draft Report for U.S. EPA Contract 68-03-3220
(Oct. 1986).
17.	"Standard Methods for the Examination of Water and Wastewater," 15th ed.,
Pub. Am. Public Health Assoc. (1985).
18.	U.S. EPA Method 1625 for Measurement of Priority Pollutants in Wastwater,
Code of Federal Regulations, Part 136.
19.	Box, G. E. P., Hunter, W. G., and Hunter, J. S., "Statistics for
Experimenters," pub. J, Wiley and Sons, Inc. (1978).
20.	U.S. EPA, "Process Design Manual: Sludge Treatment and Disposal,"
EPA 625/1-74-011, pub. U.S. EPA, Sept. 1979, p. 6-29.
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Table 1. Program Design
Cell
Contents
Test
Cell
Sludge
Type
Infiltration
Rate
(Low, High)
Sludge
Loading
(percent)
Elevation
(Upper, Ground)
or SI udge Ht. (m)
Priori
Pol 1utant
SW-SL
1
AD1
L3
10
U
NO
SW-SL
2
LT2
L
10
G
NO
SW-SL
3
AD
H3
10
G
NO
SW-SL
4
LT
H
10
U
NO
SW-SL
5
AD
L
20
G
NO
SW-SL
6
LT
L
20
U
NO
SW-SL
7
AD
H
20
U
NO
SW-SL
8
LT
H
20
G
NO
SW-SL
9
AD
L
30
U
NO
SW-SL
10
LT
L
30
G
NO
SW-SL
11
AD
H
30
G
NO
SW-SL
12
LT
H
30
U
NO
SW-SL
13
AD
L
20
G
YES
SW-SL
14
LT
L
20
U
YES
SW-SL
15
AD
H
20
U
YES
SW-SL
16
LT
H
20
G
YES
SW
17
NONE
L
0
U
NO
SW
19
NONE
L
0
G
NO
SW
18
NONE
H
0
G
NO
SW
20
NONE
H
0
U
NO
SL
21
AD
L
100
0.6 m
NO
SL
22
LT
L
100
0.6 m
NO
SL
23
AD
L
100
0.6 m
NO
SL
24
LT
L
100
0.6 m
NO
SL
25
AD
L
100
1.8 m
YES
SL
26
LT
L
100
1.8 m
YES
SL
27
AD
L
100
1.8 m
YES
SL
28
LT
L
100
1.8 m
YES
1.	AD: Anaerobically digested sludge, 16% solids
2.	LT: Lime treated sludge, 16% solids
3.	L,H: Annual water infiltration rate (L/kg of cell waste on a dry weight
basis), L = 0.5, H = 1.0

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Table 2. Refuse Physical Composition
Component
Percent (%)
Wet Weight
Paper
45.4
Texti1es
11.9
Garden Waste
10.5
Plastic
8.1
Ferrous Metal
6.3
Telephone Books
4.6
Wood
3.2
Glass
2.8
Food Waste
1.6
Diapers
1.5
Non-Ferrous Metal
1.5
Ash-Rock-Di rt
1.4
Rubber-Leather
1.1
Fines*
0.1
* Material passing through a 25 mm sieve.
Total sample weight = 1,176.5 kg

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Table 3. Composition of Sludge and Refuse (Dry solids basis)
No. of Samples
pH
acidity,to pH S.3 (mg/g)
alkalinity, to pH 3.2 (mg/g)
alkalinity, to pH 4.5 (mg/g)
TKN (mg/g)
Total P (mg/g)
COD (mg/g)
Inorganic Carbon (%)
TOC, soluble (mg/g)
Chlorides (mg/g)
Sulfide (mg/g)
Volatile Solids (%)
Metals (mg/lg)
Cd
Cr
Cu
Fe
Pb
Ni
Zn
Refuse*
Mean Std. Dev.
5
7.62	0.03
0.20	0.02
25.5	0.86
10.9	0.14
10.5	0.60
4.8	4.2
1128	58
10.1	1.7
13.0	1.4
1.96	0.19
71.8	4.1
1.3	0.9
81	41
259	80
3,740	1,320
181	51
16	7
99	75
Limed Sludge*
Mean Std. Dev.
6
10.86 0.07
300	8.1
263	7.7
38.3	3.6
14.1	0.91
345	34
9.08	0.63
44.1	4.7
12.3	1.4
2.36	0.70
36.6	0.76
17.2	12
922	36
322	9
76,800 1,400
234	39
109	10
433	20
A.D. Sludge*
Mean Std. Dev.
6
5.51	0.24
63.6	3.6
112	22
40	17
35.4	2.4
24.7	5.2
374	70
6.6	0.37
24.3	5.2
44.2	6.3
I.23	0.48
32.3	0.88
II.1	4.4
303	49
556	12
32,000 2,300
894	579
63	25
733	92
* Refuse moisture content was 42.2% before the grinding that preceded analytical
determinations, (n = 12, s = 11.6%). Limed sludge and digested sludge averaged
15.7% and 15.5% moisture respectively.

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Table 4. Sludge Priority Pollutant Analysis
Lime Treated Sludge* Anaerobically Digested^
Study
Priority Pollutant
1
2
1
2
% Recove
Phenol
2.2
ND
38
43
81
4-Chloro-3-Methylphenol
NO2
ND
13
11
49
Dibutyl Phthalate
2.7
5.6
3.0
ND
98
Butyl benzyl Phthalate
2.4
4.1
4.1
3.1
162
Bis(2-Ethylhexyl) Phthalate
131
434
250
160
120
Di-n-octyl Phthalate
9.1
15
18
10
188
Naphthalene
0.27
ND
0.77
0.71
58
F1uorene
ND
ND
0.58
0.20
63
Phenanthprene
0.97
1.2
2.8
3.4
68
Anthracene
ND
0.96
0.26
ND
75
Fluoranthene
ND
ND
1.2
ND
75
Pyrene
ND
1.4
ND
ND
76
Benzofluoranthene
ND
ND
1.2
ND
79
Benzo(A) Pyrene
0.17
0.09
1.2
ND
72
Benzo(G,H,I) Perylene
ND
ND
2.3
ND
71
Isoprorone
ND
ND
1.3
1.0
70
N-Nitrosodiphenyl amine
(as Diphenyl amine)
190
209
32
19'
104
4-Chlorophenyl Phenyl Ether
ND
ND
ND
0.26
64
1 Concentrations are
in mg/kg



2 ND indicates below
minimum <
detections limits

3 Determined from aliquots spiked with approximately
100 rug of each pollutant/kg dry sludge solids

-------
Table 5.
Cells	1-4	5-8
Ratio: SIudge/Total (%) 10.0	20.5
SIudge
Percent Solids (%)	15.6	15.6
Wet Weight (kg)	240	510
Dry Weight (kg)	37.5	79.5
Refuse
Wet Weight (kg)	2165	1976
Dry Weight (kg)	1251	1142
Mixture
Solids Content (%)	53.6	49.1
Wet Weight (kg)	2405	2486
Dry Weight (kg)	1289	1221
Volume (m3)	4.80	4.80
Density (kg/m^)	501	518
Sludge and Refuse Quantities in Test Cells
9-12 13-16	17-20 21-22, 25-26 23-24, 27-
30.6 20.5	0	100	100
15.6
811
126
15.6
510
79.5
15.6
178.8
27.9
15.6
535
83.5
1837
1062
1971
1142
2139
1237
0
0
0
0
44.8
2648
1188
4.80
552
49.1
2486
1221
4.80
518
57.8
2139
1236
4.80
446
0.61
1004
1.83
1003

-------
Table 6. Monitoring Methods and Equipment
Measurement
Analytical Technique
Moisture Content
Temperature
Gas Analyses (CH4, CO2, N2> O2)
PH
Alkalinity/Acidity
Volatile Acids
Total Solids
Volatile Solids
Total Organic Carbon (TOC)
Chemical Oxygen Demand (COD)
Total Kjeldahl Nitrogen (TKN)
Total Phosphorus
Metals (Cd, Cr, Cu, Fe, Pb, Ni,
Priority Pollutants
Constant weight at 160°C
Thermometer/thermister, direct reading
Perkin-Elmer 900 Gas Chromatograph
Sargent LS pH meter, direct reading
Water soluble; titratioon to electro-
metric endpoint
Perkin-Elmer 900 Gas Chromatograph
Gravimetric; constant weight at 103
to 105°c
Gravimetric; constant weight at 600°C
Beckman 915 TOC analyzer for soluble
TOC; test to 950°C for TOC
Dichromate Reflux
Digestion; Kjeldahl distillation, and
titration
Persulfate digestion, colorimetric
Zn) Perkin-Elmer Atomic Absorption
Finnegan GC/Mass Spectrometer

-------
Table 7. Typical Data Page Showing Results of Monthly
Analyses for COD for All Cells and Annual Averages
Lmctat* O^nical Otygan Otaand («y/l)	Soocrd Year
Test	July Aug. Sept. Oct. (tov. Oac. Jan. Feb. fferch April ftiy Oirw	Coeff.of
Cell Description 83 83 83 83 83 83 84 8484B48484Maan Var.(Z)
1
LI AO 10
3,110
3,320
3,470
3,090
3,060
2,890
2,790
2.080
2,590
2.540
2,490
2,540
2,831
14
2
LI LT 10
18,600
4.060
3.510
3.950
3,800
3,630
3.430
3,380
2.840
2.710
2,630
2,630
4,508
*
3
HI AO 10
2.670
2,540
2,090
1.750
1,650
1,420
1,330
1,850
1.560
1.820
1,080
452
1.684
34
4
HI LT 10
15,200
4,460
3,420
3.520
3,090
2,460
2.240
2.210
1.750
1.590
1,500
1,340
3.565
ioe
5
LI AO 20
3,010
3,470
3,360
3,390
3.220
2,730
2.740
2.410
2.400
2.360
2,080
2,120
2.774
17
6
LI LT 20
7.540
5,150
6,540
4.190
3.970
3,400
3,550
3.450
3.050
2.970
3,000
2,870
4.143
35
7
HI AO 20
2,220
2,020
1,730
1,710
1,490
1,270
1,260
1.240
1.000
953
896
906
1,394
30
8
HI LT 20
7,300
2,730
2,880
2.740
2.510
2,000
1,910
1.880
1.440
1.370
1,480
1.350
2.466
63
9
LI AO 30
4,860
3,89)
3,430
3,710
3,250.
2,730
2,720
2.620
2.300
2.200
2,070
2,150
2.990
27
10
LI LT 30
54,700
60,600
53,700
57,500
55.000
50,500
56,000
52.100
37.500
36.700
8,670
1,080
43.671
43
11
HI AO 30
2,340
2,220
1,900
1,860
1.790
1,510
1.460
1.560
1.230
1.190
952
999
1.583
27
12
HI LT 30
2,900
2,550
2,650
1,520
1.700
1,320
944
1.200
997
1.060
1,060
¦ 950
1.573
44
13
LI AO 20 SP
3,230
3.400
3.520
3.690
3.240
2.990
934
2.430
2.190
2,150
2,010
1.790
2,630
31
14
LI LT 20 SP
4,060
5,150
4.560
4.630
4.470
3,730
3.910
3,500
3.250
3,230
3.160
3.290
3.912
16
15
HI AO 20 SP
1.790
1.720
1.570
1.600
1.440
1,270
1,260
1.200
1,030
1.030
1.000
907
1.318
22
16
HI LT 20 SP
2,930
2,660
2.440
2.260
2.170
1,660
1.600
1.600
1,330
1.230
1,230
1.200
1.860
31
17
LI 0
49,700
38,600
48.700
49.900
46.500
41,900
52.700
48.400
38,800
4a 600
19,900
12.200
40.65B
29
18
HI 0
39,300
37,400
34,600
38.200
36.500
28,800
34,100
33.700
26,500
27.000
28,500
28.600
32.767
14
19
LI 0
50.600
42,000
48,000
51.500
51.000
43,300
52,200
51.400
42,100
47.900
48,100
49.600
48.142
7
20
HI 0
41,900
36.900
36,400
4a 100
36,500
31.100
3B.400
36.900
29,200
27,700
29.400
3a 900
34.533
13
21
LI AO 91
2,710
2.240
2,190
2.670
1,890
3.320
2.190
1.980
1.850
1.860
1.810
1.820
2.211
20
22
LI LT 91
20.900
19,500
18,600
21.900
10,000
20,300
24.300
25.700
19.900
22,300
26.900
24,500
21.233
20
23
LI AO TL
2.670
2,590
2,620
2.660
2,820
2.510
2,770
2.570
2,480
2.520
2,490
2.490
2.599
4
24
LI LT TL
23.600
22,100
22,900
26.800
2S.600
19,900
28,300
27,000
22.900
25.300
27.200
27.600
24.933
10
25
LI AO 91 SP

2,320
2,330
2.260
2.190
1,830
1,790 .
1,840
1.660 .
1.710
1,660
1.700
1.774
14
26
LI LT 91 SP
14,900
18,500
19,900
22,700
23.100
19,300
16,600
24.000
16.600
21,500
24,900
19.500
20.12S
15
27
LI AO TL SP
3,130
2,970
3,040
3,090
2.880
2.400
2,710
2.710
2.520 ,
2.530
2.640
2.790
2.784
8
2B
LI LT TL SP
3.070
3,170
3,480
3,360
3,290
3,130
3,470
3,850
3,980
4,530
5,430
6,180
3.912
24
Maen

13,891
12,078
12,269
13,080
12,040
10,832
12,415
12,313
9.821
ia377
9,082
a 372
11,381

Coeff.
of Var. (Z)
122
130
132
133
138
136
142
138
133
134
137
148

124
LI » Low Infiltration
HI ¦ Ht^i Infiltration
AO " Anearoblcally 01 gas tad Sludge
LT * Lima Treated Sludge
TL - Tall Test Cells
91 - Short Test Calls
SP - Priority, follutant Spike
10, ate. ¦ Pei1 uaiit (Z) Slufee Addition

-------
Table 8. "Sign" Table Showing Manner for
Calculating Effects and Interactions
Cells for	Factors*	Interactions*
Experiment
10-20 20-30	J_ _L JL	1*1 !*£. !*£. TxIxP
1	5-13	...	+ +
2	6-14	+	+ - + +
3	7-15	+	+ + - +
4	8-16	+ +	-
5-13	9	+	+ - - +
6-14	10	+-+	+ -
7-15	11	+ +	+
8-16	12	+ + +	+ + + +¦
* Main effects and interactions are calculated by summing according
to signs shown and dividing by 4.

-------
Table 9. Solids Content and Net Absorption
or Release of Water by Test Cells
Test Cells
Initial
Percent
Sol ids
Initial
Water
Content
(kg/kg d.s.)
Final
Percent
Soli ds 1
Final
Water
Content *
(kg/kg d.s.)
Net Mass
of Water
Absorbed
(kg/kg d.s.)
SW
57.8
0.73
40.5
1.47
0.74
SW-SL (10%)
53.6
0.87
39.6
1.53
0.66
SW-SL (20%)
49.1
1.04
38.8
1.58
0.54
SW-SL (30%)
44.8
1.23
38.0
1.63
0.40
SL (AD)
15.5
5.45
19.1
4.24
- 1.21
SL (LT)
15.7
5.37
23.5
3.26
- 2.11
1 Averaged over all cells in each grouping. For SL (LT) cells,
Cell 24 result was used for itself and in place of Cell 28.

-------

{or -
"/> / / r* / fa S?

Table 10.
Annual Average of COD Concentrations of Monthly

Leachate Collection
for Groups of Test Cells
(mg/L)
Year
1
2
3
4
Test Cell




Grouping





COD
(mg/L

SW
39,000
39,000
16,000
1,480
SW-SL-AD
10,600
2,190
1,090
700
SW-SL-LT
26,500
9,930
1,670
930
SL-AD
4,290
2,340
1,770
840
SL-LT
15,300
22,800
21,900
13,500


TOC
(mg/L)

SW-SL
6,770
1,850
419
323
SW
13,020
12,200
4,770
626
SL
3,920
4,630
4,390
2,740


Volatile
Solids (mg/L)

SW-SL
7,280
3,120
1,270
930
SW
12,780
11,850
5,470
1,350
SL
7,850
9,600
8,550
6,800


Total Solids (mg/L)

SW-SL
16,220
9,360
5,080
3,560
SW
24,880
22,510
11,390
4,340
SL
16,160
18,730
17,690
13,350



PH

SW
5.64
5.64
6.30
6.81
SW-SL, low
I 6.69
7.48*
7.22
6.98
SW-SL, high
I 6.34
7.32
6.98
6.71
SL-AD
5.98
6.20
6.32
6.36
SL-LT
8.84
9.33
9.72
9.48
* One cell (Cell 10) excluded because its pH did not rise until
late in this year.

-------
Table 11. Average COD Concentrations (mg/L) in Leachate for Each
of the SW and SW-SL Cells for the Three Contiguous
Months with Highest Concentrations in Year 1, Ranked
in Order of Increasing Concentrations
Rank Average* (mg/L)	Run No.	SL	%SL Infiltr.
1	4,400	5	AD	20	Lo
2	10,600	15	AD	20	Hi
3	13,200	1	AD	10	Lo
4	13,400	6	LT	20	Lo
5	16,800	11	AD	30	Hi
6	16,900	3	AD	10	Hi
7	18,100	7	AD	20	Hi
8	22,200	16	LT	20	Hi
9	23,300	9	AD	30	Lo
10	26,000	14	LT	20	Lo
11	26,300	13	AD	20	Lo
12	30,000	2	LT	10	Lo
13	31,200	8	LT	20	Hi
14	34,000	12	LT	30	Hi
15	40,000	4	LT	10	Hi
16	40,300	18	SW	0	Hi
17	40,600	20	SW	0	Hi
18	45,200	17	SW	0	Lo
19	48,400	19	SW	0	Lo
20	54,900	20	LT	30	Lo
~Average of the highest 3 contiguous months in Year 1

-------
Table 12. Correspondence Among Times of Substantial Sharp
Changes in Leachate Parameters: Month of Change



for the SW and SW>
-SL Cells



ell
No. pH
Loss of
0j> Phosphate*
COO
Vol.acids
Fe
Znj
1
n.c.3
n.c.
8
8-9
not clear
n.c.
—
2
12
7
<15 mg/L
14
14
11-12
--
3
7
10
7
8-10
12,144
6-8
--
4
12
7
13
14
24,174
12
--
5
n.c.
8
9
<7
not clear
10
--
6
6
10
8
6-8
9,144
8
--
7
6
6
6
7-8
9,144
4-8
--
8
11
8
13
13-14
14
11-14
—
9
8
10
9
9-11
11,204
9-11
10.
10
20-22
16
20
23-24
23
20-23
—
11
8
10
<15 mg/L
9-11
11,22
10-11
—
12
7
8
8
8-9
9
7-10
--
13
11
8
<15 mg/1
11-12
13,204
10-12
--
14
9
11
10
11-12
13,18 4
10-12
--
15
5
11
6
6
7
5-8
—
16
8
10
9
9-10
10
6-10
—
17
22
13
24
24-25
24
21-25
--
18
26
25
30
27-30
32
24-31
27
19
35
18
36
35-37
37
25-37
36
20
38
27
30,39
33-39
40
25-38
37
1.	A rapid drop in phosphate concentration was only discernible when the
concentration before the onset of active anaerobiosis wss greater than
15 mg/L (as P).
2.	For zinc, a dash indicates no drop in concentration was evident. For
all these cells zinc concentrtion was initially very low—less than
1 mg/L--so no drop could be discerned.
3.	n.c. -- not clear. It was not possible to select a month of change.
4. The first drop in concentration was followed by a small rise and a
second drop.

-------
Table 13. Average Annual Concentrations of Leachate Parameters


1
2
3
4



Chloride (mg/L)


sw

1,530
1,330
790
440
SW-SL

2,140
2,060
1,420
1,000
SW-SL,
10%
1,580
1,500
1,000
670
9
20%
2,030
1,970
1,370
980
>
30%
3,040
2,720
1,870
1,340
SL-AD

9,770
9,710
8,570
7,370
SL-LT

2,200
2,080
Phosphate (mg/L as
2,050
P)
1,640
SW

14.6
10.6
6.7
5.3
SW-SL

30.8
41.3
19.5
6.2
SL-AD*

0.14
0.54
0.71
2.12
SL-LT?

0.09
0.66
0.84
0.74



Alkalinity (mg/L)

SW

12,900
11,460
6,580
3,600
SW-SL

9,180
6,030
3,990
3,220
SL-AD

1,040
795
864
914
SL-LT

8,810
10,680
TKN (mg/L)
12,350
10,320
SW

1,750
1,770
926
329
SW-SL

1,590
1,430
830
635
SL

2,210
2,920
2,650
2,410



Volatile Acids (mg/L)

SW

13,100
12,700
5,770
460
SW-SL

9,400
2,180
211
182
SL-AD

1,820
1,470
980
280
SL-LT

9,620
6,380
9,710
3,500
1	Cell 24 not included in these averages.
2	Cell 28 not included in these averages.

-------
Table 14. Average Annual Concentrations of Metals in Leachate
1
SW	0.039
SW-SL	0.034
SL	0.059
SL-AD	0.057
SL-LT	0.060
SW	0.142
SW-SL	0.087
SL	0.050
SW	0.044
SW-SL'	0.039
SL	0.048
SL-AD	0.057
SL-LT	0.039
SW	1400
SW-SL(AD) 450
SW-SL(LT)	870
SL(AD)	1910
SL(LT) 26
SW	0.298
SW-SL	0.229
SL	0.265
SW	0.64
SW-SL	0.33
SL	0.59
SW	2.19
SW, Cell 19	4.4
SW, Cell 20	2.5
SW-SL	0.60
SL	0.21
1 Averaged without Cell 10
Year
_2_	_3_	4_
Cadmium (mg/L)
0.029	0.007	0.004
0.018	0.006	0.003
0.042	0.024	0.017
0.025	0.012	0.007
0.060	0.037	0.028
Chromium (mg/L)
O."09S	0.042	0.019
0.053	0.028	0.022
0.062	0.048	0.040
Copper (mg/L)
0.03T	0.030	0.012
0.034	0.027	0.013
0.049	0.051	0.042
0.034	0.032	0.027
0.064	0.070	0.057
Iron (mg/L)
1330	270	78
75	51	47
32	27	32
1320	310	290
18	8	3
Lead (mg/L)
0.233	0.102	0.050
0.129	0.063	0.043
0.336	0.225	0.146
Nickel (mg/L)
0.60	0.35	0.21
0.22	0.21	0.18
1.02	0.82	0.70
Zinc (mg/L)
12.0	3.62	0.14
39.1	5.7	0.11
5.6	8.2	0.30
0.30	0.12	0.12
0.27	0.18	0.13

-------

Table 15. Average Annual Concentration of Organic
Compounds for Selected Cell Groupings


1
YEAR
2 3
4
sw
SW-SL
SL
253
136
96
Acenaphthene (yg/L)
271 150
163 91
186 104
98
57
102
SW
SW-SL
SL
8
11
8
Arochlor 1254 (PCB-yq/L)
23 5
88 0
410 0
Bis(2-ethyl hexyl)phthalate (ug/L)
0
0
0
SW
SW-SL
SL
96
16
5
58 138
22 139
5 347
8
34
20
SW
SW-SL
SL
10
10
6.0
Di-n-butyl phthalate (ug/L)
12 49
12 42
6.9 99
0.3
1.4
1.6
SW
SW-SL
SL
143
15
260
Dimethyl phthalate (yg/L)
163 0
46 0
118 0
52
14
1
SW
SW-SL
SL
1.6
3.3
4.0
1,4-dichlorobenzene (yg/L)
5.9 2.6
6.2 2.8
5.9 5.6
0
1.4
6.9
SW
SW-SL
SL
474
313
584
Naphthalene ^/L)
307 187
721 477
331
266
933
SW
SW-SL
SL
1000
7910
1920
Phenol (yg/L)
680 57
3070 4100
8880 27260
7
220
14350
SW
SW-SL
SL
49
48
10
Pyrene (ug/L)
42 23
32 8
20 13
1.9
10
15

-------
Table 16. Ranking of Priority Pollutants for Likelihood
of Detection in Landfill Leachates
SW	SW-SL	SL

Rank
—
Rank
%D.

Rank %D.
Acenaphthene
2
100
2
100

3 100
Arochlor 1254^
1
0
2
6

1 0
Bis-(2-ethyl(hexyl)phthalate
1
40
2
51

1 35
Di-n-butylphthalate
1
20
1
37

1 41
Dimethyl phthalate^
2
20
2
20

1 6
1,4-dichlorobenzene
1
10
2
33

3 37
Naphthalene
3
100
3
100

3 100
Phenol
1
60
1
48

2 81
Pyrene
1
30
3
31

3 63
Average
1.4
42
2.0
47

2.0 51
* Rank: Ranked by ratio of
Year
4/Year 3
in Table
15, 1
2
3
if
if
if
Y4/Y3 < 0.2,
0.2+ to 0.7,
> 0.7+.
2 %D.: Percent of Measurements in
Year 4
that were
detectable.
3 Ranking used ratio of Year 4/Year 2.

-------
FIGURE 1: TEST CELL DESIGN
H
a 	*
2
3<
P O4
%

pea gravel
coarse gravel
U
1.	Leachate drain
2.	Infiltration line
3.	Temperature probe
4.	Gas port
Dimensions (m)
SW.SW-SL
Cells
Tall SL
Short SL
a
1.8
0.61
0.61
b
2.7
2.7
1.5
c
0.3
0.3
0.3
d
0.3
0.3
0.3
e
1.8
1.8
0.61
f
0.3
0.3
0.3
Cross section of Test Cells

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CUMULATIVE WATER
ADDITION
(Cells 13, 20)
CUMULATIVE WATER
ADDITION
(Cells 17, 19)
SYMBOL
0
X
A
+
20	30	40	50
MONTHS AFTER STARTUP
FIGURE 2. VOLUME OF LEACHATE FROM SW CELLS
CELL
17
18
19
20
WATER
RATE
Low
High
Low
High

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3000 -
CUMULATIVE WATER
ADDITION(CELLS 7, 15)
CUMULATIVE WATER
ADDITION (CELLS 5, 13)
SYMBOL CELL
0
X
A
+
5
7
13
15
WATER
RATE
Low
High
Low
High
SPIKE
No
No
Yes
Yes
MONTHS AFTER STARTUP
FIGURE 3. VOLUME OF LEACHATE FROM SW-SL CELLS WITH 20% DIGESTED SLUDGE

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20
SYMBOL
INFILT.
RATE
SLUDGE
A
Low
None
0
Low
AD
X
Low
LT
V
High
None
~
High
AD
+
High
LT
LOW INFILTRATION RATE
HIGH INFILTRATION RATE
20	30
PERCENT SLUDGE
FIGURE 4. TIME LAG BEFORE LEACHATE EQUAL
INFILTRATION FOR SW AND SW-SL CELLS

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CD
a
oo
tr>
•<
z in
=> a
»	4
Q£ —I
LU O
Q- CO
LU >-
S CX-
zd a
	i
o o
> ^
«<
<_>
<£
SYMBOL SLUDGE CELL HT
0
t)
A
AD
AD
AD
AD
21
25
23
27
20	30	40
MONTHS AFTER STARTUP
FIGURE 5. VOLUME OF LEACHATE FROM AD CELLS

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CO
o
C/)
in
-
UJ oc
ZZ Q
=)
—I CD
O ^
C
in
o
c
c
_J
r>
SYMBOL SLUDGE CELL HT
0
LT
22
S
to
LT
26
S
A
LT
24
T
"A
LT
28
T
20	30	40
MONTHS AFTER STARTUP
FIGURE 6. VOLUME OF LEACHATE FROM SL-LT CELLS

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SYMBOL
SLUDGE
INFILTR.
0
AD
Low
Ef
LT
Low
r
AD
High
*
LT
High
A
None
Low
A
None
High
0	10	20	30
PERCENT SLUDGE ORIGINALLY ADDED TO TEST CELLS
FIGURE 7. FINAL SOLIDS CONTENT OF SW-SL MIXTURES
IN TEST CELLS AFTER 4 YEARS

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100,000
10,000 I-
1,000 r
100
+ x
*
-X A r	o^rA^J
tl	*'
INFILTR.
SYMBOL CELL RATE
0
X
A
+
17	Low
18	High
19	Low
20	High
±
_L
l
+
J	±_
10	15	20	25	30
MONTHS AFTER STARTUP
35
40
45
50
FIGURE 8. INFLUENCE OF TIME ON COD OF LEACHATE: SW CELLS.

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100,000
10,000
CJ»
E
Q
o
(_)
CJ
1,000
100
SW CELL RESULTS (FROM FIG. Q)
SYMBOL CELL SPIKE
7
15
No
Yes
XX
4" + + "t-

10	15	20	25	30
MONTHS AFTER STARTUP
35
40
45
50
FIGURE 9. INFLUENCE OF TIME ON COD OF LEACHATE FROM SW-SL-AD (20%) CELLS AT HIGH
WATER RATE: COMPARED TO SW CELLS, BOTH AT HIGH INFILTRATION RATE.

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100,000
io.ooo r
cr>
E
O
o
o
UJ
f—
•a:
=n
o
-------
100,000
10,000
o>
E
o
o
o
<
IC
CJ
<
1,000
SYMBOL
X
SW-SL-AD (20%) CELLS AT
HIGH INFILTRATION RATE
SPIKE
No
Yes
100
10
15
20
25
30
35
40
45
50
MONTHS AFTER STARTUP
FIGURE 11. INFLUENCE OF TIME ON COD OF LEACHATE FROM SW-SL (20%) CELLS
AT HIGH INFILTRATION RATE: LT CELLS COMPARED WITH AD CELLS
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\
SYMBOL SL
HI
CELL
0 AD
Sll
21 ,25*
A LT
SU
22,26*
~ AO
TL
23,27*
7 LT
TL
25
* SPIKED
CELLS.
SYMBOLS
ARE TAGGED.
YEAR
FIGURE
12.
YEARLY AVERAGE LEACHATE COD FOR THE A YEAR
OPERATION PERIOD OF SLUDGE CELLS
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10"
10"
CURVE DRAWN FOR
SW LEACHATES
*
SW
SW-SL (AD)
10
Z?
J	l I i

J	1	I	L
' »
J	I 1 t J
10-
10"
COD (mg/L)
10v
FIGURE 13.
COO VERSUS TOC FOR ALL LEACHATES FROM
SW CELLS AND SU-SL CELLS WITH AD SLUDGE
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10
4 _
10"
CORRELATION FOR
SW CELL LEACHATES
V 7
10'
J	* > i » i I
J	I I r i i I
J	I I 1
10"
10"
10"
COD (mg/L)
FIGURE 14.
COD VERSUS TOC FOR ALL SW-SL LEACHATES FROM LT CELLS,
COMPARED TO CORRELATION FOR SW CELL LEACHATES
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, _ 	I	r f i « i t 	' ' i	I 1 t i i I	1	1	1 f M
10	103104105
COD (mg/L)
FIGURE 15. COD VERSUS TOC FOR ALL SLUDGE CELL LEACHATES, COMPARED
COMPARED TO CORRELATION FOR SW CELL LEACHATES
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COD (mg/L)
FIGURE 16. COD VERSUS VS FOR ALL SW-SL LEACHATES
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FIGURE 17.
COD VERSUS VS FOR SW LEACHATES, COMPARED
TO CORRELATION FOR SW-Sl LEACHATES
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J	1	I	» 1 1 .1 1..	1	1	l—I	' ' ' ' L	1 '	l	1	LJ
to	i
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MONTHS AFTER START OF EXPERIMENT
FIGURE 19. CORRESPONDENCE OF pH AND OTHER PARAMETERS
THAT EXPERIENCE SUDDEN CHANGE AT ONSET OF
ANAEROBIC PROCESSES (SW CELL 19)
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10,000
SLUDGE CELLS
TALL
SHORT
 E
S 1,000
100
10
SW CELLS
SYMBOL
~
7
0
A
LOW I
HIGH I
I
20	30
TIME (MONTHS)
40
50
CELL
21
23
19
20
60
FIGDRE 20. REDUCTION IN CHLORIDE CONCENTRATION: SW CELLS AT HIGH
AND LOW INFILTRATION, SL CELLS AT SHORT AND TALL HEIGHT
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