-------
operated in the Pittsburgh bituminous coal seam using continuous mining
methods. The acid water treated was of the type which had a low pH,
high acidity and high mineral content.
The Shannopin Mine No. 1 Air Shaft Treatment Plant treated 700,000
gallons per day (gpd) of acid water and consumed 5 to 6 tons of quick-
lime per day. A schematic diagram of this treatment plant is presented in
Figure 1.
Acid water was pumped from the mine into a 3,500,000 gallon holding
pond that had a retention time of five days. Part of the acid water
flowed by gravity to a slake tank where it was mixed with quicklime which
was also fed by gravity using a screw feeder. The slaked lime was mixed
with acid water in a small mixing tank creating a lime slurry that had
a pH of between 11 and 12. The lime slurry flowed from the mixing tank
into a sluiceway. Approximately 20 feet along the sluiceway, after
leaving the mixing tank, two pipes added more mine water from the holding
pond to the lime slurry lowering the pH to approximately 8.5. Since
the sluiceway was about 200 yards long the lime slurry and mine water
were extensively mixed and further aerated as they flowed toward the
settling pond.
When the plant was first constructed, a surface aerator was used, but
it was found that sufficient ferrous oxidation occurred in the holding
pond to make further aeration unnecessary. After mixing, the slurry
flowed into one of two large settling lagoons (30,000,000 gallon capac-
ity and 72,000,000 gallon capacity). When one settling lagoon was
being used, the other lagoon was drained of as much water as possible
and the sludge allowed to dry and compact. The two lagoons were alter-
nated in this manner and the sludgy permanently impounded in these
lagoons.
Banning No. 4 Treatment Plant
Banning Treatment Plant treated water from the Banning No. 4 Mine which
worked the Pittsburgh seam using continuous mining methods. The acid
water treated was fairly representative of the type with a pH of around
5.0 and most of the iron in the ferrous state. The pH of this water
was, however, found to be lower than 5.0, averaging around 3.1. This
plant operated on a four day per week, twenty-four hour per day schedule
and treated 2,200 gpm of acid water using hydrated lime at the'rate of
one-half ton per hour. Figure 2 is a diagram of this treatment plant.
Banning started its operation by mixing treated water with hydrated lime
to form a two percent lime slurry. Mine water was pumped directly from
the mine sump to the aerator tank where it was combined with the lime
slurry. A pH probe located in the aerator t?ank regulated the flow of
-------
3,500,000
GALLON
HOLDING
LAGOON
30,000,000 GALLON
SETTLING LAGOON
(UNDERGOING COMPACTION AT PRESENT)
QUICKLIME
STORAGE
BIN
STEEL
SLUICEWAY
SLURRY
TANK
72,000,000 GALLON
SETTLING LAGOON
UNDERGROUND
PUMP
EFFLUENT
TO STREAM
Figure I-SHANNOPIN TREATMENT PLANT SCHEMATIC DIAGRAM.
-------
HYDRATED
LIME
STORAGE
BIN
SLUDGE TO
WASTE DUMP
EFFLUENT TO SLURRY MIXING TANK
EFFLUENT
TO STREAM*
SLURRY
MIXING
TANK
104 FT. DIAMETER
CLARIFIER WITH RAKE
SURFACE
AERATORS
1— — —
1^ ^J
SLOW
MIX
TANK
UNDERG
PUMP
Figure 2- BANNING TREATMENT PLANT SCHEMATIC DIAGRAM.
-------
lime slurry to maintain a treatment pH of approximately 8.5. Two
floating aerators mixed the acid water and lime slurry while aerating
the mixture. After 30 minutes retention time in the aeration tank, the
slurry flowed to a slow mix tank and then into a 104 foot diameter
thickener clarifier. The settled sludge was moved to the center of the
thickener by a rake mechanism. The sludge was then pumped for permanent
storage into a settling basin that was also being used to store coal
refuse. Part of the settled sludge (30-40 percent) was recirculated to
the aeration tank.
Norton Treatment Plant
Acid water treated at Norton was pumped from the Grassy Run stream which
was heavily polluted from abandoned coal mines. The water from this
stream was highly acidic (pH 2.8) with nearly all of the iron in the
water in the ferric state. This treatment plant, operated by the
Environmental Protection Agency, was used for experimental purposes
only. A diagram of the treatment plant is presented as Figure 3.
The acid water was pumped from Grassy Run through a sand filter into a
500 gallon holding tank. From the holding tank the acid water was then
pumped at the rate of 15 gallons per minute into two 150 gallon mixing
tanks where the water was mixed with limestone rock dust. The limestone
addition was regulated by a pH recorder which maintains a pH range within
the mix tank of 4.9 to 5.1. The treated water from each mix tank was
then pumped into its individual 11,700 gallon settling tank. Total re-
tention time for this system was approximately 14 hours. The treated
effluent was then drawn off the settling tank and flowed back into the
Grassy Run stream. Sludge was pumped off the bottom of the settling
tanks into a 11,700 gallon sludge holding basin for further dewatering.
Final sludge disposal was accomplished by dumping the sludge into mined
out workings for perpetual storage.
Edgell Treatment Plant
Mine water at the Edgell Treatment Plant was pumped directly from a
sump located at the western end of the Williams Mine. The Williams
Mine was being operated by continuous mining methods and was mining part
of the Pittsburgh coal seam. The acid water was of the type which was
nearly neutral and contained iron primarily in the ferrous state. Part
of the untreated mine water was used to mix the slurry in the slurry mix
tank (lime consumption 480 pounds/hour) and the remainder of the mine
water was directed into the flash mixer for complete neutralization (see
Figure 4). The treatment pH for this operation was 8.0 to 8.4. The
neutralized water then flowed by gravity into an earthen aerating lagoon
that had a 15 hp surface aerator. The aerating lagoon had two outlets
which allowed the sludge and treated water to flow by gravity into
11
-------
EFFLUENT
*
TO STREAM
11,700 GALLON
SETTLING TANK
11,700 GALLON
SETTLING TANK
LIMESTONE
STORAGE
BINS
ISO GALLON
MIXING TANKS
11,700 GALLON
SLUDGE HOLDING
BASIN
EFFLUENT
TO STREAM
SLUDGE
TRUCKED
AWAY
MINE WATER
FROM STREAM
SAND
FILTER
£3
500 GALLON
HOLDING TANK
Figure 3- NORTON TREATMENT PLANT SCHEMATIC DIAGRAM
-------
HYDRATED
LIME
STORAGE
BIN
SLURRY
MIXING fe
TANK
SURFACE
AERATOR
EARTHEN SLUICEWAYS/
55,000,000
GALLON
SETTLING
LAGOON
• ^^^^^B I
Q
UNDERGROUND
PUMP
EFFLUENT
TO STREAM
Figure 4-EDGELL TREATMENT PLANT SCHEMATIC DIAGRAM.
-------
separate ends of the settling pond. The settling pond had a capacity
of 55,000,000 gallons and was used to perpetually store the sludge.
The Edgell Plant treated mine water at the rate of 1,000 gallons per
minute and ran on a twenty-four hour per day, seven day per week
schedule.
Sampling Program
A sludge and acid water sampling and analysis program was conducted at
each of the four characteristic treatment plants between June 22, 1970
and November 24, 1971. The purpose of this program was to provide
information as to the variability of acid water and sludge at each
treatment site and to collect sludge for the dewatering investigations.
Since the primary purpose of this study was concerned with dewatering,
no attempt was made to collect samples from the treatment sites at
regular intervals, but rather samples were taken when additional sludge
was needed for the dewatering studies.
Mine Water Sampling Procedure
Mine drainage chemical composition, especially the ferrous to ferric
iron ratio, was very unstable and began to change upon formation. The
main difficulty encountered in the sampling of mine drainage was keeping
the iron constituents ratio stable long enough for the sample to be
transported to the laboratory for analysis.
In order to completely determine the concentrations of the ferrous iron
present in mine drainage, the following sampling and analytical procedure
was devised. A mine water sample was taken at the point of treatment
and was placed in a polyethylene bottle. The bottle was filled to its
top to exclude as much air as possible. A second mine water sample was
filtered through Whatman No. 40 filter paper into a polyethylene bottle
that contained 100 milliliters (mis) of 3 normal hydrochloric acid.
A third sample of mine water was placed into a polyethylene bottle
that contained 20 mis of an acid mix of equal parts of sulfuric and
phosphoric acid. All three mine water samples were returned to the
laboratory for immediate analysis.
Mine Water Chemical Analysis Procedure
Mine water was analyzed for total iron, ferric iron, ferrous iron,
silicon, aluminum, magnesium, calcium, acidity, alkalinity and sul-
fates in order to determine the major chemical parameters of the water.
The chemical analysis was initiated in the field by determing the pH
using a portable battery operated pH meter. The remaining analyses
were performed in the laboratory.
The first water sample was immediately analyzed for acidity and alka-
linity. Acidity analyses were performed by the Salotto Method.
14
-------
Alkalinity determinations were made using the method subscribed to by
the American Water Works Association.(2) This latter method of analysis
was used to determine the carbonate, bicarbonate and hydroxide alkalin-
ity properties, and enabled the calculation of total alkalinity based
on these results.
The second mine water sample had been filtered to remove all the precipi-
tated ferric hydroxide in the raw water. The 3N hydrochloric acid added
to the sample minimized further iron oxidation and precipitation. The
sample was analyzed for silicon, aluminum, magnesium, calcium and total
iron using a Perkin-Elmer Model 303 Atomic Absorption Spectrometer
equipped with a DCR-1 digital readout device. Sulfates were analyzed
using the barium chloride gravimetric method.
The third mine water sample which had been acidified with tfye sulfuric-
phosphoric acid mixture was analyzed for ferrous iron by the potassium
dichromate method described by Hall.(3)
The ferric iron was determined by subtracting the ferrous iron result
from total iron as determined by atomic absorption.
Mine Water Chemical Analysis Results
Shannopin acid water was the most highly mineralized of the four waters
studied as shown in Tables 1 through 4. Norton acid water was the
lowest in mineral content. The Shannopin acid water was particularly
high in aluminum and total iron relative to the other three waters.
The Shannopin water, however, was relatively low in ferrous iron content
presumably due to aeration or bacterial oxidation occurring within the
holding pond. The Norton acid water was by far the lowest in ferrous
iron as it was collected from a stream and was well aerated by natural
processes.
No carbonate or hydroxide alkalinity was found in any of the samples;
however, bicarbonate was detected in some Edgell samples.
The four acid waters studied represented a wide range of chemical compo-
sition and should therefore be reasonably representative of the range
of mine drainage normally encountered. Mine water types of such quality
as to not require treatment were not included in this survey
Sludge Chemical and Physical Analyses
The following information was determined in order to define the major
physical and chemical parameters of the sludges.
1. Settling rate of slurries.
2. Percent solids of slurries and settled sludge.
15
-------
Table 1
Shannopin Treatment Plant Chemical Analysis
Analysis of Raw Water
PH
Ca (ppm)
Mg (ppm)
Al (ppm)
Si (ppm)
SOf (ppm)
Fe4"4" (ppm)
Fe44* (ppm)
Total Fe (ppm)
Acidity (ppm CaC03)
HCO* (ppm CaC03)
Analysis
Ca (ppm)
Mg (ppm)
Al (ppm)
Si (ppm)
S0« (ppm)
Total Fe (ppm)
Nonfilterable Solids (ppm)
High
2.9
430
200
150
40
5,000
180
500
670
2,400
0
of Slurry
High
2,100
200
150
60
5,000
640
39,300
Low
2.7
400
150
120
30
4,300
10
430
510
1,800
0
Low
1,400
180
130
0
4,400
470
3,800
Mean
2.8*
410
170
140
35
4,500
100
480
580
2,000
• 0
Mean
1,600
190
140
40
4,600
550
14,300
Median Value
16
-------
Table 2
Banning Treatment Plant Chemical Analysis
Analysis of Raw Water
pH
Ca (ppm)
Mg (ppm)
Al (ppm)
Si (ppm)
SO^ (ppm)
Fe44 (ppm)
Fe444 (ppm)
Total Fe (ppm)
Acidity (ppm Ca(X>3)
HCO- (ppm CaC03)
Ca (ppm)
Mg (ppm)
Al (ppm)
Si (ppm)
SO? (ppm)
Total Fe (ppm)
Nonfilterable Solids
High
3.3
490
140
40
30
2,900
180
90
260
850
0
Analysis of Slurry
High
950
130
50
25
2,800
300
(ppm) 3,400
Low
2.8
420
120
25
20
2,400
140
50
200
530
0
Low
770
120
40
25
2,700
210
1,400
Mean
3.1*
450
130
35
20
2,700
160
60
220
680
0
Mean
860
130
45
25
2,700
260
2,400
Median Value
17
-------
Table 3
Norton Treatment Plant Chemical Analysis
Analysis of Raw Water
PH
Ca (ppm)
Mg (ppm)
Al (ppm)
Si (ppm)
SOg (ppm)
Fe"*"1" (ppm)
Fe*1*"1" (ppm)
Total Fe (ppm)
Acidity (ppm CaC03)
HCO* (ppm CaC03)
Ca (ppm)
Mg (ppm)
Al (ppm)
Si (ppm)
SOjj (ppm)
Total Fe (ppra)
Nonfilterable Solids
High
2.9
160
35
40
20
1,000
3
120
120
670
0
Analysis of Slurry
High
500
35
35
15
1,100
120
(ppm) 250
Low
2.8
100
25
20
10
600
1
55
60
360
0
Low
180
25
20
7
610
50
45
Mean
2.9*
120
30
30
10
800
2
90
90
520
0
Mean
310
30
25
10
790
90
140
Median Value
18
-------
Edgell
pH
Ca (ppm)
Mg (ppm)
Al (ppm)
Si (ppm)
S0« (ppm)
Pe4"*" ppm
Pe44* ppm
Total Fe (ppm)
Acidity (ppm CaC03)
HCO- (ppm CaC03)
Ca (ppm)
Mg (ppm)
Al (ppm)
Si (ppra)
SO^ (ppm)
Total Fe (ppm)
Nonfilterable Solids
Table 4
Treatment Plant Chemical
Analysis of Raw Water
High
6.7
480
150
50
25
5,900
870
80
870
1, 700
440
Analysis of Slurry
High
1,400
80
75
20
4,300
340
(ppm) 3,100
Analysis
Low
4.6
280
75
2
5
4,100
210
0
220
50
0
Low
620
70
8
9
4,200
220
760
Mean
6.0*
370
95
20
15
4,800
460
30
490
660
110
Mean
920
75
35
15
4,200
260
2,200
Median Value
19
-------
3. Chemical composition of slurries.
Sludge Sampling Procedure
Two types of sludge were taken during the sludge sampling and analysis
program. The first sample was the sludge slurry that was formed by the
neutralization process. This sample reflected the characteristics of
the treatment plant at the time of sampling. These samples were taken
prior to discharge in the settling lagoon. Settled sludge was the second
sample taken and it was used in the evaluation of the various dewatering
apparatus examined. In all cases, except for the Banning Treatment Plant,
settled sludge was pumped from the bottom of the settling lagoon near
the slurry discharge point in order to get as fresh a sample as possible.
Settled sludge samples from the Banning Treatment Plant were taken from
a bleeder line off the sludge recirculation system located in the main
treatment plant building. All sludge samples were brought back to the
laboratory in five gallon plastic jugs or 55 gallon drums.
The sludge sampling points for each treatment plant are summarized in
Table 5.
Sludge Settling Tests
Settling tests were conducted in the field using 1,000 ml volumetric
flasks, 1,000 ml graduated cylinders, and a timer. A settling test
was initiated by filling a volumetric flask with slurry and immediately
transferring the slurry to the graduated cylinder. The initial height
of the slurry and starting time were recorded. As the sludge settled
in the graduated cylinder, periodic readings of the sludge interface
were taken and the data plotted.
Settling tests performed in the field were conducted to determine the
sludge settling rate for the first few hours. Additional samples were
brought back to the laboratory in order to determine the final settled
volume. The rate of settling was also recorded for the samples re-
turned to the laboratory in order to determine the effect of previous
settling on the settling rate.
Sludge Solids Content
Percent solids determinations were performed routinely on the slurry
and the settled sludge. The methods of analyses used for determination
of percent solids of slurry and settled sludge (nonfilterable) were
essentially the same as the procedures described in the Federal Water
Pollution Control Administration Manual.(4)
20
-------
Table 5
Sludge Sample Point Locations
Type of Sludge Banning Plant Edgell Plant Norton Plant Shannopin Plant
to
M
Slurry At slow mix tank At discharge At discharge At discharge point
point from points into in lagoon
aerator settling tank
Settled sludge From bleeder line Off shore of From settling Off shore of
located in treat-- settling tank settling lagoon
ment plant lagoon
-------
Sludge Chemical Analyses
Chemical analyses were performed on the slurry sludge. The purpose
of the chemical analyses was to observe the change in sludge chemical
constituents as the raw water changed. Iron, calcium, magnesium,
aluminum, silicon and sulfates were routinely determined for all the
sludge samples. Atomic absorption analysis was used for the determin-
ation of metallic ions after dry precipitates present in the sample
were dissolved with hydrochloric acid. Sulfates were determined by the
barium chloride gravimetric method. Tables 1 through 4 summarize the
chemical data for each slurry*
Sludge Physical Analysis Results
Sludge treated at the Edgell Treatment Plant settled faster than the
other two lime sludges examined; the next fastest being Banning sludge
followed by the Shannopin sludge. Norton sludge did not settle with
a distinguishable interface and so its rate of settling was not eval-
uated. From the settling tests conducted it can be concluded that
most of the settling for each sludge was complete in three hours or
less. The settling rates for the three sludges which settled with
a distinct interface are shown in Figures 5 through 7. These figures
also show a comparison between the settling rate for each sludge
upon collection and its settling rate approximately 24 hours later
when the sample was resettled in the laboratory.
Each sludge occupied a different volume after settling and compaction
were complete.The Norton sludge settled to the lowest settled volume
(1.1 percent). The Edgell sludge settled to the next higher volume,
(4.0 percent) followed by Banning (8.0 percent) and then Shannopin,
(25.0 percent). All sludge volumes are given in terms of percent of the
original slurry volume.
The general settling properties of the sludges studied are similar to
other mine drainage sludges reported in the literature. The limestone
sludge settles to a very small volume which agrees with previous work
conducted by Wilmoth et al.W; however, since the Norton water was
the lowest in mineral content of those studied, its relatively smaller
sludge volume cannot be attributed only to the use of limestone but also
to the small amount of sludge forming minerals in the water. In the
report by Wilmoth et al. a direct comparison was made between lime and
limestone sludge. Norton sludge (the limestone sludge) was found
to occupy only two thirds of the volume of the lime sludge. Similarly
the Shannopin sludge, which is created from a highly mineralized mine
water neutralized with quicklime, had a large final settled volume. As
would be expected, sludge from Shannopin and Banning settled faster in
the laboratory than in the field since any surface change on the labor-
22
-------
100
ro
GO
SETTLED
SOLIDS-
% VOLUME
40
10
20 30 40 50
SETTLING TIME - MINUTES
60
Figure 5-SETTLING RATE OF MIXING TANK SLUDGE FROM SHANNOPIN TREATMENT PLANT
-------
too
80
60
SETTLED
SOLIDS-
% VOLUME
40
20
0 10 20 30 40 50 60
SETTLING TIME-MINUTES
6- SETTLING RATE OF AERATOR SLUDGE FROM BANNING TREATMENT PLANT.
-------
100
N)
in
80
60
SETTLED
SOLIDS-
%VOLUME
40
20
"0 10 20 30 40 50 60
SETTLING TIME-MINUTES
Figure 7- SETTLING RATE OF AERATOR SLUDGE FROM EDGELL TREATMENT PLANT.
-------
atory sample had been dissipated by previous settling. Edgell sludge
showed little change in settling rates after previous settling, indica-
ting that settling had little effect on the physical character of the
sludge particles.
Sludge Chemical Analysis Results
The results of the sludge characterization program are summarized in
Tables 1 through 4. The Shannopin slurry was the highest in elemental
concentrations of the four sludges studied and also was highest in
nonfilterable solids. This was to be expected since Shannopin water
had the highest mineral content of the four waters. The Norton slurry
was the lox^est in elemental concentrations and again this is to be
expected since Norton water x?as the lowest of the four in mineral con-
tent.
The four slurries represented a fairly wide range of chemical composition
and should therefore represent a fair cross section of the various
types of sludges.
26
-------
SECTION V
SLUDGE CONDITIONING
Several sludge conditioning methods were examined in order to re-
duce sludge volume and/or increase filtration rates during sludge
dewatering processes. A unique conditioning process called sludge
freezing was investigated as a method of reducing sludge volume and
numerous flocculants and filter aids were investigated as conditioning
agents to increase filtration rates. Since the purpose'of this report
was primarily to determine the feasibility and efficiency of various
coal mine drainage sludge dewatering systems, flocculants were
evaluated primarily as they related to dewatering. However, it was
reasoned that if a flocculant was to be utilized at a treatment site
for dewatering, it could be applied to the slurry before it entered
the clarifier and simultaneously enhance both settling rates and
dewaterability. Accordingly, clarification studies were also conducted
on various sludges using flocculants which were selected with improved
filtration rates as a criteria.
Sludge Freezing
General
Freezing, as a sludge conditioning process, has been investigated by
a number of researchers with sewage and water works sludges. Early
investigations found that, after freezing, sludge solids settled at
a faster rate and settled to a smaller volume than did unfrozen
sludge solids. The nature of the freezing process is not exactly known;
however, freezing appears to destroy the gelatinous structure of the
sludge allowing the entrapped water and solids to separate.
The early research into sludge freezing has resulted in the construc-
tion of several plants that freeze conditioned waterworks sludge. Due
to the relatively high cost per unit volume of freezing, secondary
sludge thickening was especially attractive and is generally utilized
at these plants. The designers found, for example, in one plant that
by slow stirring, the quantity of sludge to be frozen could be reduced
from 33,000 gpd at .5 percent solids to 6900 gpd at 2.4 percent solids.
Following the thickening process the sludge was pumped to a freezing
tank where it was frozen and then thawed. The sludge solids and liquid
were then allowed to separate by gravity draining.^
From the early research it was found that sludge must be completely
frozen but at a relatively slow rate.(?) Recent studies on sewage
sludge have shown that sludge freezing can be achieved by using the
film-freezing principle. Film freezing of sludge operates on prin-
ciples similar to extended freezing but freezing time is reduced since ,
the sludge is frozen as a thin film.^
27
-------
The cost of freezing waterworks sludge was found to be high. In one
case, the freezing cost was $6.78 per 1000 gallons of sludge as compared
to $5.04 per 1000 gallons of sludge dumped into lagoons. One of the
major justifications of the extra cost was the use of the land for
agricultural purposes that would have otherwise been used for la-
goons
Test Equipment - Description
To observe the effects of freezing on different types of coal mine
drainage sludge, laboratory scale freezing tests were conducted on the
four characteristic sludges.
Equipment used for this series of experiments consisted of a conven-
tional freezing compartment of a household refrigerator, plastic
beakers, graduated cylinders, a thermometer, and a timing device.
Test Procedure
In order to observe the general effects of freezing on sludge proper-
ties, a standard was established for comparison. This was accomplished
by taking 500 ml samples of the 4 sludges described in the sludge and
acid water characterization section, allowing each to settle for
six hours, and determining the final settled volume of the sludge.
Following the establishment of a standard unfrozen settled volume for
each sludge, 500 ml samples of the four sludges were then introduced
into a freezing environment (-14°C) for 4, 5, 6, 7, 8, and 24 hours.
After freezing, each sample was allowed to thaw and then was reintro-
duced into a 500 ml graduated cylinder. The sludge was allowed to
settle for six hours and the final settled volume was determined along
with percent solids of the settled sludge.
Test Results
Artificial freezing was found to reduce the volume of coal mine drain-
age sludge. Table 6 summarizes the results from the sludge freezing
experiments.
Freezing appeared to have the greatest effect on the sludges that were
produced from lime treatment. This was evidenced by the similarity in
the reduction of settled sludge volume (approximately 90 percent)
following freezing from the Shannopin, Banning and Edgell sludges.
These plants used either hydrated lime or slaked quicklime for water
treatment. However, in the case of the Norton sludge which was
28
-------
Table 6
Summary of Results from Sludge Freezing Tests
Treatment Plant
Norton
Edgell
Banning
Shannopin
Sludge Solids Content
After Freezing (percent)*
21.0
17.8
6.3
13.9
Reduction in
Settled Sludge Volume
After Freezing (percent)**
47.0
90.6
90.5
88.5
6 hours of settling and water over sludge removed
**
6 hours of settling
29
-------
treated with limestone, a reduction in settled volume of only 47.0
percent was observed.
The reasons for the substantially greater decrease in settled sludge
volume after freezing for lime sludges compared to the limestone sludge
are not exactly known. However, it is known that the sludges created
from lime treatment are substantially more gelatinous in structure and
hold more water than sludges from limestone treatment. Since the effect
of freezing is thought to be due to a breaking down of the gelatinous
structure of the sludge, a greater degree of volume reduction following
freezing would be expected with lime sludges.
•,
Figures 8, 9, 10 and 11 illustrate the relationship of degree of
freezing to settled sludge volume. It can be seen from the graphs that
as the time the sludge was in the freezing environment increased, the
settled volume of the sludge generally decreased.
The graphs, to a certain degree, suggest a near linear relationship
between the degree of freezing and final settled sludge volume at least
for the first portion of the curves.
The time necessary to completely freeze the quantities of sludge that
were studied is undoubtedly less than 24 hours. It was the intention,
however, to guarantee complete sludge freezing, therefore, an arbitrary
24 hour maximum freezing time period was chosen.
It can be concluded from the graphs that the full effects of freezing
do not take place until the sludge is completely frozen. This fact
agrees with research conducted on other types of sludge.(9)
Accompanying the substantial reduction in sludge settled volume fol-
lowing freezing was the requisite increase in sludge percent solids as
shown in Table 6. The final percent solids of the frozen sludge was
determined following six hours of settling with the clarified water
over the top of the sludge removed.
To summarize, artificial freezing of coal mine drainage sludge can
in most cases substantially reduce the final settled volume and con-
currently increase the sludge solids content. The research conducted
on freezing of coal mine drainage sludge suggests that the success
achieved with a commercial waterworks sludge freezing process could
be emulated with coal mine drainage sludge. The ultimate application
will, of course, relate to the economics of the process.
30
-------
100
80
60
SETTLED
SOL IDS-
% VOLUME
40
20
345
FREEZING TIME - HOURS
8
Figure 8-RELATIONSHIP OF FREEZING TIME AND VOLUME OF SOLIDS FOR SLUDGE FROM SHANNOPIN
TREATMENT PLANT
-------
100
80
60
SETTLED
SOLIDS-
%VOLUME
40
OJ
20
012345
FREEZING TIME-HOURS
Figure 9-RELATIONSHIP OF FREEZING TIME AND VOLUME OF SOLIDS FOR SLUDGE FROM BANNING
TREATMENT PLANT.
-------
80
60
SETTLED
SOLIDS-
%VOLUME
40
U)
20
I
^
24 Hours \ >
8
1/tr
234567
FREEZING TIME - HOURS
Figure 10-RELATIONSHIP OF FREEZING TIME AND VOLUME OF SOLIDS FOR SLUDGE FROM NORTON
TREATMENT PLANT.
-------
100
60
SETTLED
SOLIDS
%VOLUME
40
20
345
FREEZING TIME-HOURS
6
Figured- RELATIONSHIP OF FREEZING TIME AND VOLUME OF SOLIDS FOR SLUDGE FROM
EDGELL lf*EATMENT PLANT.
-------
Conditioning For Dewatering and Clarification
General
Chemical conditioning (the use of chemicals to alter sludge character-
istics) of sewage and industrial sludges has been studied by various
workers and found to be a reasonably successful method of improving
solid-liquid separation. This success prompted the investigation
of chemical conditioning of coal mine drainage sludge.
After a thorough search of the technical literature, it was concluded
that chamical conditioning with flocculants and filter aids might be
promising. Flocculants are generally high molecular weight, water
soluble synthetic polymers that improve solid-liquid separation by a
combination of several mechanisms such as surface charge reduction
and absorption.
Charge reduction or neutralization occurs when electrical charges on
the surface of the solid particles are reduced. The solid particles
are then no longer repellent and can adhere or coagulate when they
come in contact with each other.
Absorption is achieved when the polymer molecules attract and hold
particulate matter. The polymers may also attach to each other in
a bridging action which can result in the formation of clumps of
particles many times larger than the original particles.
The result of charge reduction and absorption is flocculation which
produces heavier, faster settling particles thereby improving
solids-liquid separation.
Filter aids are chemicals which increase the permeability of a
filter cake (a relatively compact sludge layer on a dewatering appar-
atus such as a vacuum filter). Filter aids generally increase perme-
ability by physically disrupting the packing of the sludge as the filter
cake forms, providing more channels or openings through which water
may pass. [
Recognizing the versatility of these types of conditioners, two
different, but related studies were conducted. The major study dealt
with the application of flocculants and filter aids as an aid to
filtration operations. The second study dealt with the application
of the same flocculants as an aid to clarification.
Flocculants were evaluated primarily as they applied to dewatering;
however, these conditioners could be applied to a slurry before it
entered the clarifier and simultaneously enhance both settling rates
and dewaterability. Accordingly, a flocculant was selected for each
35
-------
sludge in terms of improved dewaterability. The same flocculant
was then evaluted for any secondary benefits such as increased set-
tling rates.
Equipment
Sludge conditioning investigations emphasizing filtration applications
were conducted using a Buchner funnel filtrate recovery test. The
Buchner funnel test was used because it is a commonly accepted labor-
atory procedure that simulates vacuum filtration operations. An
illustration of the Buchner funnel apparatus is presented in Figure
12. The equipment used for the tests was an 11 centimeter Buchner
funnel, Whatman Number 5 filter paper, two 1000 milliliter vacuum
flasks, a vacutim gauge and a small vacuum pump. The two vacuum
flasks were connected in series to the vacuum pump, the one closest
to the pump fitted with the vacuum gauge and the other holding the
Buchner funnel. A glass "T" was placed in the hose between the vacuum
gauge and the pump with a short piece of tubing and a pinch clamp
attached to the leg of the "T". The pinch clamp was used as a relief
valve to control the vacuum.
The settling rate (clarification) tests were performed using two 1000
milliliter graduated cylinders and two 1000 milliliter volumetric
flasks.
Filtration Procedure
The initial step in performing a Buchner funnel filtrate recovery test
was preparation of the flocculant sample. Each flocculant examined was
mixed with distilled water to obtain a 0.25 weight percent stock solu-
tion. The proper amount of stock solution to give the desired floccu-
lant concentration was volumetrically added to a graduated cylinder
and diluted with distilled water to a volume of 30 milliliters. In this
manner the percent solids concentration of the sludge was always altered
by a fixed amount for each test and variations in filtrate recovery were
not due to a change in solids content.
The 30 milliliter flocculant solution was placed in one beaker and 100
milliliters of the sludge to be tested was placed in another beaker. The
contents of the beakers were mixed by pouring the flocculant into the
sludge and then pouring the mixture from one beaker to the other five
times. The degree of mixing was thereby held constant.
A piece of filter paper was placed in the Buchner funnel, wetted and
vacuum applied to seal the paper to the funnel. The vacuum was then
released, the flask emptied and the conditioned sludge poured into
the funnel. The vacuum was applied for one minute, released and the
36
-------
Figure 12- BUCHNER FUNNEL APPARATUS
-------
amount of filtrate recovered was measured and recorded.
For control purposes, the untreated sludge was tested using 30 mis
of distilled water and the filtrate recovery was compared to the
filtrate recovery results from the same test using conditioned
sludge.
A total of 62 flocculants were examined in the first series of tests
in conjunction with a lime sludge using the Buchner funnel test. Each
flocculant was tested at various concentrations ranging from approximately
1 ppm to 115 ppm. The increase in filtrate recovery and optimum concen-
trations were recorded for a large number of cationic, anionic and
non-ionic flocculants.
Filter aids (materials like diatomaceous earth which act to improve
the porosity of a filter cake) were studied in !a similar manner
except that the desired amount of dry filter aid was poured into a
graduated cylinder and distilled water was added to create a total
volume of 30 milliliters. The 30 milliliter filter aid-water mix-
ture was then mixed with 100 milliliters of the sludge. The sludge-
filter aid mixture was then examined against an untreated sludge
using the Buchner funnel test.
Six different filter aids were used on Norton sludge (a limestone
treatment sludge) and the results examined.
Following the first series of tests, the best flocculants and/or
filter aids were selected using a 30 percent or greater increase in
filtrate recovery over the control filtrate recovery as a criteria.
Using the Buchner funnel test again these selected flocculants were
then tested against the four characteristic mine drainage sludges.
From these tests the best conditioner and its optimum concentration
was determined for each sludge.
Settling Rate (Clarification)
Sludge conditioning studies using flocculants were carried further into
the area of clarification. Settling rate tests were conducted at the
respective treatment plants using the flocculant at its optimum con-
centration found for that sludge from the previous Buchner funnel
tests.
; • i '
Two 1000 milliliter volumetric flasks were prepared, one having a 100
milliliter flocculant solution in it and the other 100 milliliters of
distilled water. Both flasks were then filled with 900 milliliters of
sludge slurry collected just before it entered the settling lagoon or
clarifier.' The two flasks were emptied into 1000 milliliter graduated
38
-------
cylinders and Che timing clock started. As the sludges settled, in-
terface readings were taken at various times during the test along with
remarks as to the relative clarity of the water above the interface.
In the case of the Norton slurry, this procedure could not be followed
as a definite interface did not form. On those occasions the only data
taken was a relative clarity, with and without flocculants, at
various time intervals.
Filtration Results
Based upon the results of the initial screening test presented in
Table 7, 14 flocculants were found to give an increase in filtrate
recovered of 30 percent or greater. These 14 selected flocculants
were all anionic and had a medium to high atomic weight relative
to the other flocculants tested. The results of the initial
screening test for filter aids is shown in Table 8. None of the
filter aids gave an increase in filtrate recovered of over 30 per-
cent. Filter aids were thereby eliminated from further study.
The results of the detailed evaluation of the 14 selected flocculants
are shown in Tables 9 -through 12. Shannopin sludge responded best
to the use of flocculants; however, it required a relatively large
dosage for maximum effect. Norton sludge on the other hand responded
the least to the use of flocculants although maximum effect was obtained
at a relatively small dosage. From this latter series of tests a floc-
culant for each of the four sludges was selected on the basis of greatest
increase in filtrate recovered for that sludge. Each sludge was con-
ditioned with its best flocculant in later dewatering studies. The
selected flocculants are listed below:
1. Shannopin Sludge - Nalcolyte 673 at 111.0 ppm
2. Banning Sludge - Coagulant 2350 at 37.0 ppm
3. Edgell Sludge - Hercofloc 831 at 111.0 ppm
4. Norton Sludge - Decolyte 940 at 37.0 ppm
Clarification Results
The settling curves for Shannopin, Banning and Edgell sludges, all of
which settle with a distinct interface, are shown on Figures 13 through
15. The settling curves for sludges without flocculant may differ
somewhat from those shown in Figures 5 through 7 due to variances
in the water treated at the same treatment plant on different days.
The variance in the water treated causes a variance in the sludge
produced and therefore alters the settling rates.
All of the sludges settled faster with a flocculant and all showed
some increase in water clarity; however, the improvement is probably
39
-------
not enough to justify their use for clarification alone. In interpre-
ting these settling curves it must be remembered that these flocculants
were selected with increased filtration rates as a criteria rather
than increased settling rates.
Norton sludge was tested with a flocculant and while no interface
could be detected the sludge did not appear to settle faster with a
flocculant and did not produce a clearer water.
40
-------
Table 7
Effect of Flocculants on Filtrate Increase
Lime Sludges
(Unit costs based on purchase quantity of 1,000 pounds, F.O.B.)
Unit
Cost
$1.25/lb.
$1.25/lb.
$1.25/lb.
$1.25/lb.
$1.35/lb.
$1.25/lb.
$0.24/lb.
Flocculant
Flocculant Tested Type
*Allied Colloids, Inc. anionic
Percol 139
Allied Colloids, Inc. cationic
Percol 140
Allied Colloids, Inc. anionic
Percol 155
*Allied Collids, Inc. anionic
Percol 156
Allied Colloids, Inc. cationic
Percol 292
Allied Colloids, Inc. nonionic
Percol 351
American Cyanamid Co. cationic
Optimum
Flocculant
Concentration
(ppm)
11.1
2.9
11.1
18.5
5.8
3.9
111.0
Filtrate
Increase Flocculant
With Cost Per
Flocculant 1000
(percent) Gallons
39.7 $0.12
5.1 $0.03
23.2 $0.12
63.2 $0.19
1.6 $0.06
7.3 $0.04
9.0 $0.22;
Magnifloc 521 C
-------
Table 7 (Continued)
Unit
Cost
$0.28/lb.
**NA
**NA
$1.35/lb.
$1.35/lb.
$1.50/lb.
$1.50/lb.
$1.25/lb.
$1.25/lb.
Flocculant Tested
American Cyanamid Co.
Magnifloc 560 C
American Cyanamid Co.
Magnifloc 570 C
American Cyanamid Co.
Magnifloc 571 C
American Cyanamid Co.
Magnifloc 835 A
American Cyanamid Co.
Magnifloc 836 A
American Cyanamid Co.
Magnifloc 837 A
American Cyanamid Co.
Magnifloc 905 N
American Cyanamid Co.
Superfloc 16
American Cyanamid Co.
Flocculant
Type
cationic
cationic
cationic
anionic
anionic
anionic
nonionic
nonionic
nonionic
Optimum
Flocculant
Concentration
(ppm)
3.7
37.0
18,5
3.7
w
—
2.9
2.9
Filtrate
Increase
With
Flocculant
(percent)
0.0
0.5
3.4
20.1
25.8
23.0
0.0
1.6
4.2
Flocculant
Cost Per
1000
Gallons
NA
NA
$0.21
$0.04
$0.02
$0.03
$0.03
Superfloc 20
-------
Table 7 (Continued)
Unit
Cost
$1.30/lb.
$1.30/lb.
$1.25/ Ib.
$0.40/lb.
$1.65/lb.
$2.25/lb.
$2.25/lb.
$1.92/lb.
$1.92/lb.
Flocculant Tested
American Cyanamid Co.
Superflpc 84
American Cyananid Co.
Superfloc 127
American Cyanamid Co.
Superfloc 202
American Cyanamid Co.
Superfloc 310
*Calgon Corp.
Calgon 240
Calgon Corp.
Coagulant 2256
Calgon Corp.
Coagulant 2260
Calgon Corp.
Coagulant 2300
Calgon Corp.
Flocculant
Type
nonionic
nonionic
anionic
cationic
anionic
cationic
cationic
nonionic
anionic
Optimum
Flocculant
Concentration
(ppm)
3.9
1.9
1.9
1.9
25.9
5.8
5.8
5.8
3.9
Filtrate
Increase
With
Flocculant
(percent)
6.9
5.7
21.7
1.8
68.3
0.5
3.8
1.8
3.7
Flocculant
Cost Per
1000
Gallons
$0.04
$0.02
$0.02
$0.01
$0.04
$0.11
$0.11
$0.09
$0 . 06
Coagulant 2325
-------
Table 7 (Continued)
Unit
Cost
$1.92/lb.
$1.92/lb.
$1.92/lb.
*• **NA
**NA
«.«/».
**NA
Flocculant Tested
*Calgon Corp.
Coagulant 2350
*Calgon Corp.
Coagulant 2400
*Calgon Corp.
Coagulant 2425
Diamond Shamrock Corp.
Decolyte 710
Diamond Shamrock Corp.
Decolyte 720
*Diamond Shamrock Corp.
Decolyte 930
*Diaraond Shamrock Corp.
Flocculant
Type
anionic
anionic
anionic
cationic
cationic
anionic
anionic
Optimum
Flocculant
Concentration
(ppm)
55.5
18.5
111.0
3.7
1.9
3.7
Filtrate
Increase
With
Flocculant
(percent)
37.0
41.9
50.0
0.0
3.6
32.9
45.3
Flocculant
Cost Per
1000
Gallons
$0.09
$0.30
$1.78
NA
$0.04
NA
**NA
**NA
Decolyte 940
Diamond Shamrock Corp.
Decolyte 950
*Dow Chemical Co.
Purifloc A-21
anionic
anionic
3.7
111.0
28.0
40.4
NA
NA
-------
Table 7 (Continued)
Ui
Unit
Cost
$1.30/lb.
$1.35/lb.
$0.45/lb.
$0.45/lb.
$1.50/lb.
$1.50/lb.
$1.50/lb.
*NA
$0.30/lb.
Flocculant Tested
Dow Chemical Co.
Separan AF 30
*Dow Chemical Co.
Separan AP 273
Drew Chemical Corp.
Drewfloc 3
Drew Chemical Corp.
Drewfloc 3
Drew Chemical Corp.
Drewfloc 6
Drew Chemical Corp.
Drewfloc 6
Drew Chemical Corp.
Drewfloc 230
Drew Chemical Corp.
Drewfloc 230
Drew Chemical Corp.
Flocculant
Type
anionic
anionic
anionic
cationic
anionic
cationic
anionic
cationic
anionic
Optimum
Flocculant
Concentr a tion
(ppra)
37.0
11.1
1.9
0.4
5.8
2.9
1.9
0.6
Filtrate
Increase
With
Flocculant
(percent)
23.3
31.3
12.0
0.0
9.8
5.7
8.0
5.7
10.2
Flocculant
Cost Per
1000
Gallons
$0.40
$0.13
$0.01
$0.01
$0.07
$0.04
NA
$0.01
Drewfloc 410
-------
Table 7 (Continued)
Unit
Cost
$1.35/lb.
$1.50/lb.
$1.25/lb.
$1.25/lb.
$1.25/lb.
$1.25/ Ib.
$1.25/lb.
$0.49/lb.
$0.31/lb.
Flocculant Tested
Hercules , Inc .
Hercofloc 812
Hercules, Inc.
Hercofloc 815
*Hercules, Inc.
Hercofloc 818
Hercules , Inc .
Hercofloc 821
Hercules, Inc.
Hercofloc 827
*Hercules, Inc.
Hercofloc 831
Hercules, Inc.
Hercofloc 834
Nalco Chemical Co.
Nalcolyte 110 A
Nalco Chemical Co.
Flocculant
Type
cationic
cationic
anionic
anionic
nonionic
anionic
cationic
nonionic
cationic
Optimum
Flocculant
Concentration
(ppm)
2.9
5.8
11.1
5.8
1.0
18.5
1.9
1.0
0.2
Filtrate
Increase
With
Flocculant
(percent)
1.9
12.7
57.4
21.2
4.5
60.3
12.5
3.2
3.3
Flocculant
Cost Per
1000
Gallons
$0.03
$0.07
$0.12
$0.06
$0.01
$0.19
$0.02
$0.01
$0.01
Nalcolyte 603
-------
Table 7 (Continued)
Unit
Cost
$1.37/lb.
$2.06/lb.
$1.76/lb.
$1.73/lb.
$0.11/lb.
Flocculant Tested
Nalco Chemical Co.
Nalcolyte 670
Nalco Chemical Co.
Nalcolyte 672
*Nalco Chemical Co.
Nalcolyte 673
Nalco Chemical Co.
Nalcolyte 675 H
Narvon Mining and
Flocculant
Type
nonionic
anionic
anionic
anionic
cationic
Optimum
Flocculant
Concentration
(ppm)
1.9
18.5
5.8
1.9
Filtrate
Increase
With
Flocculant
(percent)
0.0
11.4
41.7
19.4
6.8
Flocculant
Cost Per
1000
Gallons
$0.03
$0.27
$0.08
$0.01
$0.117Ib.
Chemical Co.
Zeta Floe S
*Narvon Mining and
Chemical Co.
Zeta Floe WA
Narvon Mining and
Chemical Co.
Zeta Floe WA3
Narvon Mining and
Chemical Co.
Zeta Floe WA5
anionic
anionic
anionic
5.8
1.9
1.9
31.4
13.7
19.0
$0.01
$0.01
$0.01
-------
Table 7 (Continued)
Unit
Cost
$17.75/100
$0.18/lb.
Flocculant Tested
National Starch and
Chemical Co.
Natron 86
Rohm and Hass Co.
Primafloc A 10
Flocculant
Type
cationic
anionic
Optimum
Flocculant
Concentration
(ppm)
5.8
Filtrate
Increase
With
Flocculant
(percent)
0.0
26.6
Flocculant
Cost Per
1000
Gallons
$0.01
00
Average increase in recovery for all flocculants - 17.3%
Average increase in recovery with anionics - 30.0%
Average increase in recovery with cationics - 3.9%
Average increase in recovery with nonionics - 3.5%
Selected for further study.
**
This flocculant no longer manufactured, price not available.
-------
Table 8
Effect of Filter Aids on Filtrate Increase
Norton Treatment Plant Sludge
(Average Percent Solids 4.1)
(Unit costs based on purchase quantity of 1,000 pounds, F.O.B.)
Unit
Cost
*- $0.50/ ton
\O
$50.80/ton
$160.00/ton
•
$160.00/ton
$160.00/ton
$0.50/ ton
Optimum
Material Used As Concentration
Filter Aid (ppm)
Municipal Incinerator
Fly ash
-Bituminous Coal 3,850
crushed to -60 mesh
Johns-Manville 3,850
Hyflo Super-Cell
Johns-Manville 3,850
Celite 501
Johns-Manville 3,850
Celite 503
Wet Collected
Filtrate Increase With
Filter Aid
(percent)
0.0
6.2
8.4
10.8
3.2
Flocculant
Cost Per
1000
Gallons
$0.82
$2.57
$2.57
$2.57
limestone modified
flyash
40,000
2.7
$0.08
-------
Table 9
Effect of Selected Flocculants on Filtrate Increase
Shannopin Treatment Plant Sludge
(Average Percent Solids 5.3)
(Unit costs based on purchase quantity of 1,000 pounds, F.O.B.)
Unit
Cost
$1.25/lb.
$1.25/lb.
$1.65/lb.
$1.92/lb.
$1.92/lb.
$1.92/lb.
$1.41/lb.
Flocculant Tested
Allied Colloids, Inc.
Percol 139
Allied Colloids, Inc.
Percol 156
Calgon Corp.
Calgon 240
Calgon Corp.
Coagulant 2350
Calgon Corp.
Coagulant 2400
Calgon Corp.
Coagulant 2425
Diamond Shamrock Corp.
Optimum Flocculant
Concentration (ppm)
55.5
37.0
74.0
44.4
44.4
44.4
111.0
Filtrate Increase
With Flocculant
(percent)
56.5
54.2
58.3
61.7
57.4
56.0
10.1
Flocculant
Cost Per
1000
Gallons
$0.58
$0.39
$1.02
$0.71
$0.71
$0.71
$1.31
Decolyte 930
-------
Table 9 (Continued)
Unit
Cost
**NA
**NA
$1.35/lb.
$1.25/lb.
$1.25/lb.
$1.76/lb.
$0.11/lb.
Flocculant Tested
Diamond Shamrock Corp.
Decolyte 940
Dow Chemical Co.
Purif loc A 21
Dow Chemical Co.
Separan AP 273
Hercules, Inc,
Hercofloc 818
Hercules, Inc.
Hercofloc 831
Nalco Chemical Co.
Nalcolyte 673
Narvon Mining and
Chemical Co.
Zeta Floe WA
Average
Optimum Flocculant
Concentration (ppm)
111.0
111.0
55.5
44.4
74.0
111.0
111.0
73.5
Filtrate Increase
With Flocculant
(percent)
32.1
58.7
60.0
50.0
65.9
13.7
13.7
50.1
Flocculant
Cost Per
1000
Gallons
NA
NA
$0.63
$0.46
$0.77
$1.63
$0.10
**
This flocculant no longer manufactured, price not available.
-------
Table 10
Effect of Selected Flocculants on Filtrate Increase
Banning Treatment Plant Sludge
(Average Percent Solids 1.2)
(Unit costs based on purchase quantity of 1,000 pounds, F.O.B.)
N>
Unit
Cost
$1.25/lb
$1.25/lb.
$1.65/lb.
$1.92/lb.
$1.92/lb.
$1.92/lb.
$1.4l/lb.
Flocculant Tested
Allied Colloids, Inc.
Percol 139
Allied Colloids, Inc.
Percol 156
Calgon Corp.
Calgon 240
Calgon Corp.
Coagulant 2350
Calgon Corp.
Coagulant 2400
Calgon Corp.
Coagulant 2425
Diamond Shamrock Corp.
Optimum Flocculant
Concentration (ppm)
11.1
25.9
25.9
37.0
37.0
18.5
1.9
Filtrate Increase
With Flocculant
(percent)
19.3
25.3
23.7
42.8
32.9
30.3
32.9
Flocculant
Cost Per
1000
Gallons
$0.12
$0.27
$0.36
$0.59
$0.59
$0.30
$0.02
Decolyte 930
-------
Table 10 (Continued)
Unit
Cost
**NA
**NA
$1.35/lb.
$1.25/lb.
$1.25/lb.
$1.76/lb.
$0.11/ln.
Flocculant Tested
Diamond Shamrock Corp.
Decoiyte 940
Dow Chemical Co.
Purifloc A 21
Dow Chemical Co.
Separan AP 273
Hercules, Inc.
Hereof loc 818
Hercules, Inc.
Hercofloc 831
Nalco Chemical Co.
Nalcolyte 673
Narvon Mining and
Chemical Co.
Zeta Floe WA
Average
Optimum Flocculant
Concentration (ppm)
3.7
37.0
11.1
11.1
25.9
111.0
37.0
28.2
Filtrate Increase
With Flocculant
(percent)
41.1
25.6
31.3
19.0
37.1
26.7
33.8
30.1
Flocculant
Cost Per
1000
Gallons
NA
NA
$0.12
$0.12
$0.27
$1.63
$0.03
**
This flocculant no longer manufactured, price not available.
-------
Table 11
Effect of Selected Flocculants on Filtrate Increase
Norton Treatment Plant Sludge
(Average Percent Solids 4.1)
(Unit costs based on purchase quantity of 1,000 pounds, F.O.B.)
Unit
Cost
$1.25/lb.
$1.25/lb.
$1.65/lb.
$1.92/lb.
$1.92/lb.
$1.92/lb.
$1.41/lb.
Flocculant Tested
Allied Colloids, Inc.
Percol 139
Allied Colloids, Inc.
Percol 156
Calgon Corp.
Calgon 240
Calgon Corp.
Coagulant 2350
Calgon Corp.
Coagulant 2400
Calgon Corp.
Coagulant 2425
Diamond Shamrock Corp.
Optimum Flocculant
Concentration (ppm)
3.7
9.3
55.5
11.1
18.5
7.4
25.9
Filtrate Increase
With Flocculant
(percent)
15.7
12.6
12.7
6.5
14.9
18.4
.26.1
Flocculant
Cost Per
1000
Gallons
$0.04
$0.10
$0.76
$0.18
$0.30
$0.12
$0.30
Decolyte 930
-------
Table 11 (Continued)
Unit
Cost
**NA
**NA
$1.35/lb.
$1.25/lb.
$1.25/lb.
$1.76/lb.
$0.11/lb.
Flocculant Tested
Diamond Shamrock Corp.
Decolyte 940
.*•
Dow Chemical Co.
Purifloc A 21
Dow Chemical Co.
Separan AP 273
Hercules , Inc .
Hercofloc 818
Hercules , Inc .
Hercofloc 831
Nalco Chemical Co.
Nalcolyte 673
Narvon Mining and
Chemical Co.
Zeta Floe WA
Avet
Optimum Flocculant
Concentration (ppm)
37.0
55.5
37.0
37.0
37.0
37.0
111.0
:age 34.5
Filtrate Increase
With Flocculant
(percent)
31.7
25.6
13.5
20.8
13.5
17.3
12.2
17.3
Flocculant
Cost Per
1000
Gallons
NA
NA
$0.42
$0.39
$0.39
$0.54
$0.10
**
This flocculant no longer manufactured, price not available,
-------
Table 12
Effect of Selected Flocculants on Filtrate Increase
Edgell Treatment Plant Sludge
(Average Percent Solids 3.6)
(Unit costs based on purchase quantity of 1,000 pounds, F.O.B.)
Unit
Cost
$1.25/lb.
$1.25/lb.
$1.65/lb.
$l,92/lb.
$1.92/lb.
$1.92/lb.
$1.41/lb.
Flocculant Tested
Allied Colloids, Inc.
Percol 139
Allied Colloids, Inc.
Percol 156
Calgon Corp.
Calgon 240
Calgon Corp.
Coagulant 2350
Calgon Corp.
Coagulant 2400
Calgon Corp.
Coagulant 2425
Diamond Shamrock Corp.
Optimum Flocculant
Concentration (ppm)
25.9
92.5
37.0
37.0
92.5
74.0
111.0
Filtrate Increase
With Flocculant
(percent)
16.7
42.2
67.8
50.0
35.4
55.8
19.8
Flocculant
Cost Per
1000
Gallons
$0.27
$0.96
$0.51
$0.59
$1.48
$1.19
$1.30
Decolyte 930
-------
Table 12 (Continued)
Unit
Cost
**NA
**NA
$1.35/lb.
u. $1.25/lb.
•>4
$1.25/lb.
$l,76/lb.
$0.11/lb.
Flocculant Tested
Diamond Shamrock Corp.
Decolyte 940
Dow Chemical Co.
Purif loc A 21
Dow Chemical Co.
Separan AP 273
Hercules, Inc.
Hercofloc 818
Hercules, Inc.
Hercofloc 831
Nalco Chemical Co.
Nalcolyte 673
Narvon Mining and
Chemical Co.
Zeta Floe WA
Averai
Optimum Flocculant
Concentration (ppm)
111.0
92.5
81.4
111.0
111.0
111.0
111.0
ee 85.6
Filtrate Increase
With Flocculant
(percent)
24.0
22.2
55.8
50.0
73.8
53.3
4.5
40.8
Flocculant
Cost Per
1000
Gallons
NA
NA
$0.92
$1.15
$1.15
$1.63
$0.10
**
This flocculant no longer manufactured, price no available.
-------
100
oo
80
60
SETTLED
SO LIDS -
% VOLUME
40
20
10
20 30 40
SETTLING TIME-MINUTES
50
60
Figure 13- SETTLING RATE OF CONDITIONED MIXING TANK SLUDGE
FROM SHANNOPIN TREATMENT PLANT
-------
100
vO
80
60
SETTLED
SOLIDS-
%VOLUME
4O
20
With Floccu I ant ( Cocci
20 30 40
SETTLING TIME-MINUTES
Figure 14-SETTLING RATE OF CONDITIONED AERATOR SLUDGE FROM
BANNING TREATMENT PLANT
-------
100
80
60
SETTLED
SOLIDS-
%VOLUME
40
20
ant (Hereof toe 831 )
10
50
20 30 40
SETTLING TIME-MINUTES
Figure 15-SETTLING RATE OF CONDITIONED AERATOR SLUDGE FROM
EDGELL TREATMENT PLANT
60
-------
SECTION VI
SLUDGE DEWATERING
The primary objective of this research was to evaluate various de-
watering systems as they apply to the sludge produced by the neutrali^
zation of acid mine drainage. The systems evaluated were:
1. Conventional Rotary Vacuum Filtration
2. Rotary Precoat Vacuum Filtration
3. Pressure Filtration
4. Porous Bed Filtration
5. Thermal Spray Drying
6. Centrifugation
The evaluation of each of the above dewatering systems is presented
in four parts. The first part is a brief discussion of the dewatering
system as used in industry. This section includes a brief description
of a commercial size unit of the dewatering system and its general
method of operation. The second part is a description of the test
apparatus used. Generally the test equipment was bench scale; however,
some of the dewatering systems were studied on a semi-pilot plant
scale. The procedure used in making the dewatering tests is described
in the third section. And the fourth section is a discussion of the
results of the bench scale tests. The results section is intended
to show whether it is technically feasible to dewater each of the
four sludges by the method in question and to compare the relative
efficiency of this method on each sludge.
The results obtained with these different systems vary with changes in
the solids content of the sludge to be dewatered. Also, the sludge
collected from the settling lagoons of Shannopin, Norton and Edgell
varied in solids content with each field trip. Since the sludge was
pumped from below several feet of water varying amounts of water would
be pulled into the pump with the sludge. Banning sludge was collected
as underflow from the clarifier and showed no significant change in
solids content, averaging very close to 0.5 percent solids. In order
to maintain a fair basis for comparison of the various dewatering
systems it was necessary to assign a solids content for each sludge
as follows: Shannopin sludge 2.1 percent, Edgell sludge 2.7 percent
and Norton sludge 8.0 percent. In some cases additional work was
done at a higher or lower solids content than that specified in order
to determine the effect of a variance in solids content on a specific
dewatering system. If the solids content of a sludge as collected
was found to be less than the desired solids content, it was allowed
to settle and some water decanted until the correct solids content
was obtained. In cases where the solids content as collected was too
high, treated water from the plant in question was added until the
solids content was correct.
61
-------
Conventional Vacuum Filtration
General
A conventional rotary vacuum filtration unit consists of a horizontal
drum covered with a filter media. Vacuum is applied to segments of the
filter media from within the drum as the drum is rotated. As the
filtrate is pulled through the filter media the solids are deposited
on the media.
Rotary vacuum filtration may be divided into three phases. The first
phase is filtration which occurs on a portion of the drum during the
time when that portion of the drum is submerged in the sludge. As a
segment of the drum rotates into the sludge, vacuum is applied and fil-
trate is drawn through the filter media and discharged. Concurrently,
sludge solids are deposited on the filter media face to form a cake.
As the sludge cake becomes thicker, its resistance to the passage of
filtrate increases. The drum speed and amount of submergence of the
drum are adjusted such that each segment of the drum leaves the slurry
before the increasing cake resistance reduces the filtrate flow rate
below an acceptable level.
The second phase of the operation occurs during the time a segment of
the drum leaves the sludge and before the cake is removed. It is during
this time that the cake is dried. As the drum leaves the sludge the
cake is still under vacuum and additional moisture contained within
the cake is drawn out. This phase may be of varying length de-
pending on the desired dryness of the cake and the time required to
achieve this dryness. The cake has reached its highest practical degree
of dryness when it cracks as air will then be drawn through the cracks
in the cake rather than through the cake itself.
The third phase, cake removal, begins after the cake has reached
acceptable dryness. At this point the vacuum is removed and the
cake is discharged. The most common types of conventional cake dis-
charge devices are a scraper discharge, a wire discharge or a string
discharge. The scraper, the most commonly used type, is a sharp
blade which is mounted on the side of the filter tank and scrapes
the filter cake from the drum. However, when thin sticky cakes are
encountered, a taut longitudinal wire may be used. The longitudinal
wire is under great tension and is fixed in the same position as the
scraper tip; this allows the cake to be peeled off the drum. When
cakes which adhere strongly to the filter cloth are encountered a
string type discharge may be used. With the string type discharge,
annular strings are spaced about 3/8 inch apart and are around the
drum and on top of the filter cloth. The strings are led from the
discharge point on the drum to a small roller away from the drum and
then back to the drum again. The cake is supported by these strings.
As the strings leave the drum the cake is led off the drum and is
62
-------
discharged at the sharp bend made by the roller in returning the
string to the drum.t10' All of the operations described are of a
continuous nature so all three phases are occurring simultaneously
on different portions of the drums surface.
Test Apparatus - Description
Bench scale experiments were performed with a 0,1 square foot surface
area, Dorr-Oliver filter leaf apparatus shown in Figure 16. This
leaf was designed to simulate the function of an equal area on the sur-
face of a full size conventional rotary vacuum filtration drum.
The filter leaf was connected to two graduated receivers by hoses and
a two way valve. The vacuum source was connected to the receivers in
a like manner so that one receiver could be collecting filtrate while
the other was being vented and drained. The vacuum source consisted
of a small vacuum pump which was connected by a hose to a 1000 milli-
liter volumetric flask. The flask was equipped with a vacuum gage
which registered inches of mercury and an air bleed to reduce vacuum
to the leaf. The purpose of the flask was to keep water from being
pulled into the vacuum pump. The test apparatus also included a four
liter container which held the sludge to be tested. The sludge was
stirred manually with a glass rod in order to keep the sludge parti-
cles in suspension.
Various filter cloths from Eimco Filter Media Corporation and National
Filter Media Corporation were used in these tests.
Procedure
The three phases of a rotary vacuum filtration cycle were duplicated
with the filter leaf. First the filter leaf was submerged in the
sludge container under vacuum to duplicate the filtration phase of
the filter drum's cycle. Second the filter leaf was lifted from the
sludge and placed face up on a ring stand to duplicate the drying
phase. The third phase involved removing the built up sludge cake
by scraping it away after air had been applied behind the filter media
to loosen the cake. As with rotary vacuum filtration, the filter media
was under vacuum for the entire cycle except for cake discharge.
The amount of vacuum used was 24 to 25 inches of Hg.
Since a minimum cake thickness of 1/8 inch was necessary to permit
proper discharge of the cake from the filter cloth,C11' the conditions
necessary to produce a 1/8 inch thick cake were determined. Length
of the first phase of a conventional rotary vacuum filtration cycle
(the submergence time of the leaf into the sludge) determines the
thickness of the cake formed. By experimentation the length of time
63
-------
Second
Timer
Two-Way
Valve
Two-Way
Valve
Ring Stand With
Platform to Hold Test
Leaf While Drying
Vacuum
Gage
Air Bleed to
Reduce
Vacuum to Leaf
To Vacuum
Source
Rubber
Hose ""
Stirring
Rod\
Filter
Leaf
Slurry
Container
To Drain
Figure 16-FILTER LEAF APPARATUS
-------
required for a 1/8 inch cake build up for each sludge was found. This
time was the minimum submergence time for the cycle. For the second
phase the leaf was placed on a ring stand and vacuum dried. The dry-
ing time was found experimentally by allowing the cake to dry until
it cracked, at which time the cake had reached its highest practical
degree of dryness. The third phase of the cycle (the time required
to remove the cake from the filter cloth) is constant depending upon
the type of machinery used. The amount of filtrate recovered each
cycle and the time required for the cake to crack during drying along with
any observations as to condition of the sludge cake were recorded.
After the optimum cycle time was established for a sludge, the sludge
cake formed was analyzed for solids content on an Ohaus moisture
determination balance.
All four sludges, with and without flocculants, were studied in the
same manner. The sludge was conditioned with the flocculant that
was found in the earlier Buchner funnel tests to give the highest
increase in filtration rates.
Results
Results obtained with conventional rotary vacuum filtration were
good for Norton sludge but poor for Banning, Edgell and Shannopin
sludges.
In the tests 38 filter cloths from Eimco Corporation and 5 filter
cloths from National Corporation were investigated with a lime neu-
tralized sludge. Of these 43 different cloths four were chosen
according to best filtrate clarity and best filtration rates obtained.
These four cloths were all from Eimco Corporation and were NY-301,
CO-3, NY-518F, and Popr-913F. These cloths were tested with each
of the four sludges both with and without the optimum concentration
of flocculant added as determined by Buchner funnel tests. It was
found that filter cloth CO-3 gave the best results for Banning, Edgell
and Norton sludges and cloth NY-301 gave the best results for Shannopin
sludge. Results on the four sludges and their respective filter cloths
are shown in Tables 13 through 16.
A minimum sludge cake build up of 1/8 inch is necessary to allow
proper discharge of the cake from the filter cloth. Vacuum filters
are normally designed with a variable speed drive to operate at
between 1 to 10 minutes per revolution (mpr). This would mean
that cake formation time for a 1/3 submergence drum cannot exceed
3 1/3 minutes. A drum with 1/2 or greater submergence was not
considered due to high capital and operating costs. If a cake
thickness of 1/8 inch or greater can be formed in this time, a
conventional vacuum filter should be considered. If the cake thick-
65
-------
Table 13
Conventional Vacuum Filtration
Shannopin Treatment Plant Sludge
Filter Cloth - Eimco NY 301
Filtrate
Feed
Solids
(percent)
2.4
2.4*
4.2
4.0*
Dip
Time
(min)
•^"••••••MMB*
10
10
10
5
Time
to
Crack
(sec)
120
17
30
420
Sludge
Dewatered
(gal/sq ft/min)
0.0576
0.0731
0 .0280
0.0474
Quality
Nonfilterable
Solids
(ppm)
997
23
343
25
Cake
Thickness
(in)
0.1250
0.1250
0.3750
0.1875
Solids
(percent)
17.0
12.6
15.1
15.5
With Nalcolyte 673 added (flocculant)
-------
Table 14
Conventional Vacuum Filtration
Banning Treatment Plant Sludge
Filter Cloth - Eimco CO-3
Filtrate
Feed
Solids
(percent)
0.4
0.4*
2.2
2.1*
Dip
Time
(min)
5
10
5
5
Time
to
Crack
(sec)
25
20
120
120
Sludge
Dewatered
(gal/sq ft /min)
0.1237
0.0845
0.0694
0.0712
Quality
Nonfilterable
Solids
(ppm)
618
23
42
3
Cake
Thickness
(in)
0.125
0.125
0.250
0.250
Solids
(percent)
11.2
9.2
8.8
10.1
With Coagulant 2350 added (flocculant)
-------
Table 15
Conventional Vacuum Filtration
Norton Treatment Plant Sludge
Filter Cloth - Emico - CO-3
Filtrate
00
Feed
Solids
(percent)
8.1
8.1*
12.3
12.3*
Dip
Tine
(min)
20
20
20
20
Time
to
Crack
(sec)
15
10
20
20
Sludge
Dewatered
(gal/sq f t/min)
0.1140
0.1910
0.1660
0.1660
Quality
Nonfilterable
Solids
(pptn)
33
13
-
Cake
Thickness
(in)
0.1250
0.1875
0.3750
0.3750
Solids
(percent)
19.8
19.2
21.3
20.3
With Decolyte 940 (flocculant)
-------
Table 16
Conventional Vacuum Filtration
Edgell Treatment Plant Sludge
Filter Cloth - Emico - CO-3
Filtrate
AO
Feed
Solids
(percent)
3.0
3.0*
6.8
7.2*
Dip
Time
(min)
10
10
10
10
Time
to
Crack
(sec)
70
60
300
260
Sludge
Dewatered
(gal/sq ft/min)
0.0323
0.0396
0.0321
0*0272
Quality
Nonfilterable
Solids
(ppm)
100
58
30
"
Cake
Thickness
(in)
0.0625
0.125
0.25
0.1875
Solids
(percent)
30.9
24.2
28.0
29.0
With Hercofloc 831 added (flocculant)
-------
ness is less than this, then a precoat filter should be considered.
Of the four representative sludges only Norton produced a discharge-
able cake within the time limitation (3-1/3 minutes) imposed by a
conventional rotary vacuum filter unit. It might be possible to use
special equipment to handle the other three sludges by conventional
vacuum filtration; however, the cost of such equipment would be high.
Norton sludge was tested at 8.1 and 12.3 percent solids both with
and without flocculant conditioning. At 8.1 percent solids without
flocculant the best dip or submergence time was found to be 20 seconds.
This gave a cycle time of one minute at 1/3 submergence which is the
minimum cycle time required for conventional rotary vacuum filtration
and the minimum cake thickness of 1/8 inch was obtained.
When the flocculant was added to the 8.1 percent solids Norton sludge
there was an increase in filtration rate, filtrate clarity and cake
thickness. These increases were not observed when the flocculant
was applied to the 12.3 percent solids Norton sludge. However, the
final percent solids of the cake was not changed significantly with
the addition of the flocculant to the sludge for either the 8.1 or
the 12.3 percent solids Norton sludge.
The filtrate obtained from each of the four sludges using the best
available filter cloth generally was not of sufficiently high clarity
to warrant its discharge into a stream.
Rotary Precoat Vacuum Filtration
General
Rotary precoat vacuum filtration is similar to conventional rotary
vacuum filtration with one major exception; the application of a
precoat (generally diatomite) to the filter prior to actual filtra-
tion. Diatomite is the siliceous skeletal remains of single - celled
aquatic plant life called diatoms. The diatoms form a permeable
coating on the filter that allows the filtrate to pass through easily
while sludge solids are trapped, thereby producing a filtrate of very
high clarity.
The rotary precoat vacuum filtration unit, like the conventional rotary
vacuum filtration unit, consists of a horizontal drum that is covered
with a filter media. Vacuum is applied to segments of the filter media
from within the drum and the drum is rotated. Initially the drum is
immersed in a slurry of the precoat and an increasingly thick cake of
diatomite is formed on the drum as the fluid is pulled through the filter
media and the solids deposited on the media. After the precoat has
70
-------
reached sufficient thickness (several inches depending on the length
of time the filter is to be continuously operated), it is shaved
smooth and dewatering can now begin,
Rotary precoat vacuum filtration may be divided into three phases. The
first and second phases are essentially the same as in conventional
rotary vacuum filtration. The third phase, cake removal, begins when
the cake has reached acceptable dryness. In practice the cake must
be removed before it cracks as cracking in the cake tends to cause
cracking and gouging of the precoat. Before cracking occurs the cake
and a few thousandths of an inch of precoat are cut away by means of
a continuously advancing knife. The sludge cake and the precoat are
then discharged. The fresh surface of precoat now exposed by the cut
is rotated into the sludge once more to again start the filtration phase.
Test Apparatus - Description
Bench scale experiments were performed with a 0.1 square foot surface
area precoat filter leaf apparatus rented from Johns-Manville Research
Center. This leaf, shown in Figure 17, was designed to simulate the
function of an equal area on the surface of a full size rotary precoat
vacuum filtration drum.
The filter leaf was composed of two parts: a collar and within the
collar, a moveable septum that together act as a system to hold and
advance the precoat.
The septum (or filter media) was circular and mounted on top of
a screw shaft that moves the septum up or down within the cylindrical
collar. An indicator fixed to the screw regulates, in thousands of an
inch, movement of the septum within the collar. The filter leaf was
connected to two graduated receivers by hoses and a two way valve.
The vacuum source was connected to the receiver in such a manner that
one receiver was collecting filtrate while the other was vented and
being drained. This dual setup allowed tests of indefinite duration
since one receiver could easily be drained as the other was filled and
the flow of filtrate diverted to the freshly drained receiver with
minimal effect on filtrate recovery.
To assure the stability of the apparatus the filter leaf was attached to
a mounting that provided support. In addition to providing support the
mounting also allowed the leaf to rotate in both the horizontal and
vertical directions.
The test apparatus also included a small slurry tank that had a 1.5
liter capacity. The slurry tank was equipped with a variable speed
agitator used to keep the sludge particles in suspension.
71
-------
1 •
. ...?..
Figure 17- PRECOAT FILTER LEAF APPARATUS
-------
Procedure
Preparing the precoat filter leaf for experimentation was done
in such a manner as to simulate the formation of a precoat on a
full sized filter drum. Precoating was initiated by pouring
approximately 400 mis of a 2 percent by weight precoat slurry on
the filter leaf, allowing the precoat layer to filter dry and repeating
the process until the desired precoat thickness was reached. Alter-
nately adding slurry and filtering it dry produces a cake with a
laminar structure similar to that which forms on a filter drum.
Great care had to be taken to avoid erosion when adding slurry onto an
already formed precoat. After the precoat cake was formed, shrinkage
cracks were repaired by spooning the slurry onto the surface and the
surface was shaved smooth.
Following the precoating operation, the three phases of a rotary pre-
coat vacuum filtration cycle were duplicated with the filter leaf.
The filter leaf was submerged in the slurry tank under vacuum to
duplicate the filtration phase of a filter drum's cycle. The filter
leaf was then lifted from the sludge and rotated to a vertical posi-
tion to duplicate the drying phase. The third phase involved rotating
the leaf to a horizontal position, advancing the cake and cutting away
the sludge cake and a few mils of precoat with a sharp knife. When
the cake was advanced, a portion of the precoat extended beyond the collar
of the filter leaf could easily be cut away. The filter leaf was under
vacuum for the entire cycle. The vacuum used was about 25 inches of Hg.
Four variables were examined during the precoat filter leaf dip tests:
cycle time, depth of cut, type of precoat and flocculant effects.
A test was initiated by first determining the optimum cycle time for a
sludge. The following cycle times examined, which represent submer-
gence, drying and cutting times respectively, are considered typical
for difficult to dewater sludges in industrial operations: 20-15-10
seconds, 30-20-10 seconds and 45-35-10 seconds. The cycle chosen
as being best was that which produced the highest filtrate recovery
and an acceptably smooth cut.
After the best cycle time was chosen, the second variable, depth of
cut, was evaluated. Depth of cut refers to the thickness of precoat
cut away with the sludge cake. As a sludge cake forms on the precoat
there was some penetration of the precoat by the sludge particles. The
depth of penetration depended on the sludge being dewatered and the
type of precoat used. If the sludge particles were not removed from the
precoat they would cause a decrease in permeability which is sometimes
called blinding. To alleviate this blinding during each cycle the cut
had to be deep enough to remove all of the particles. Starting with the
15 mil cut used during the previous cycle time the cut was made progres-
73
-------
sively shallower until filtration rates began to drop. The point at
which filtration rates dropped represents the minimum usage of precoat
concurrent with the maximum filtration rates.
Following the study of the best cut for the initial type of precoat,
a different precoat was then evaluated. The cycle time did not change
when investigating different precoats on the same sludge. Therefore,
the optimum cut to allow maximum filtration was the only data taken
following a change from one precoat to another.
The last variable studied was the use of a flocculant to increase fil-
tration rates. The sludge was conditioned with the flocculant that was
found by the Buchner funnel tests to give the highest increase in
filtration rates. The same battery of tests (cycle time, depth of cut)
were employed on the flocculant conditioned sludge and the results
compared. All four sludges were studied both preconditioned and non-
conditioned in the same manner using the tests described above.
The amount of filtrate recovered in each cycle was recorded along
with any observations as to sludge cake or precoat condition. Since
in some cases much difficulty was encountered in obtaining a smooth
cut, each cut was rated on an arbitrary scale of smooth, slight gouging
and gouging. When the optimum combination of the four variables for
a sludge was found, the sludge cake formed by those variables and the
precoat cut away with it were analyzed for solids content on the Ohaus
determination moisture balance.
Results
The results obtained with precoat vacuum filtration were generally good
for Edgell, Shannopin and Banning sludges and rather poor for Norton
sludge.
Precoat vacuum filtration was not found to be feasible for Norton sludge
as it was not possible to obtain a smooth cut. The Norton sludge would
often crack the precoat and would always gouge it with the result that
on successive cuts the gouged portion of the precoat face would not be
cleaned of sludge. Various precoats were tried, the drying time was
reduced to as little as one second, and both flocculants and body feed
were added in an attempt to eliminate the gouging, but with little
success. It appeared as though the Norton sludge attached itself
unusually well to the precoat during filtration and as the sludge cake
shrunk during drying, pieces of precoat were pulled away from the
precoat cake.
Precoat vacuum filtration was found to be feasible for Edgell, Shannopin,
and Banning sludges. Smooth cuts were obtained and in general it was
74
-------
found that these three sludges would be suitable for dewatering by
precoat vacuum filtration.
The results of the precoat filter leaf tests are summarized in Table 17.
The best cycle time for all three sludges was 20 seconds filtration,
15 seconds drying and 10 seconds cutting. This means a total drum
speed of 45 seconds per revolution which is generally considered to be
the fastest practical drum speed. A fast drum speed was necessary for
efficient operation due to the rapid increase in cake resistance during
filtration shown by a sharp decrease in filtrate flow rate with
time. In addition a quick formation of cracks in the filter cake
during drying was observed which means that only a short drying may be
used since the cake must be removed before it cracks. When a short fil-
tration time is indicated it could be achieved by a low submergence;
however, since this would increase the drying time another solution had
to be found. The only other mechanism available to reduce filtration
time was drum speed and therefore a fast drum speed was used to provide
a short filtration time and a short drying time.
The best precoat was generally Celite 501 although Hyflo Super-Gel
proved best in two cases. These are both "fairly tight" precoats
(capable of retaining fine particles) as would be expected since the
sludge particles were small in size.
In the absence of detailed cost figures, as would be generated by a
pilot plant operation, it was felt that the most realistic approach to
the problem of precoat usage versus filtrate recovery rates was to max-
imize filtrate recovery rates. Using this criteria the optimum cut
was determined to be either 4 or 5 mils per minute for all sludges
tested with or without flocculants.
The highest filtrate recovery rates without a flocculant were obtained
with Banning sludge which has the lowest solids content of the three
sludges which were found to be suitable for dewatering by precoat
vacuum filtration. The lowest recovery rates were obtained with
Edgell sludge which has the highest solids content. The only un-
expected development in recovery rates was the high recovery rate of
Shannopin sludge with flocculants. The average recovery rate of floc-
culated Shannopin sludge was slightly higher than that for flocculated
Edgell sludge.
The highest cake solids was obtained with Edgell sludge both with and
without flocculant. In all cases the solids content of the filter
cakes dropped with the use of flocculants, apparently due to the for-
mation of a thicker (and therefore more difficult to dry) cake produced
by the higher filtration rates. A strong inverse relationship may be
noticed between filtration rates and cake solids content.
75
-------
Table 17
Optimum Conditions for Rotary Precoat Vacuum Filtration
Sludge
Shannopin
Shannopin
Banning
Banning
Edgell
Edgell
Flocculant
None
Nalcolyte 673
None
Coagulant 2350
None
Hercofloc 831
Cycle Knife
Time Advance
Filter/Dry/Cut Rate
(seconds) Precoat (mils/min)
20/15/10
20/15/10
20/15/10
20/15/10
20/15/10
20/15/10
Hyflo Super-Gel
Celite 501
Celite 501
Hyflo Super-Cel
Celite 501
Celite 501
5
4
5
4
4
5
Cake
Sludge Solids
Dewatered Content
(gal/f t^/min) (percent)
0.294
0.550
0.472
0.527
0.223
0.353
22.9
11.4
17.2
15.5
35.1
30.0
-------
The filtrate produced, as is typical with a precoat, was of excellent
clarity. The filtrate from rotary precoat vacuum filtration could be
discharged into a stream without any further treatment.
Pressure Filtration
General
Pressure filtration is a process in which the slurry to be dewatered
is forced into the filter press under high pressure and a porous media
in the press retains the solids while allowing the liquid to pass.
A filter press generally consists of a series of chambers with plates
on either side. The plates are covered with a suitable filtering media
and have a drainage surface pattern of grooves, cones, diamonds, or
other forms through which the filtrate may pass to the discharge line.
The chambers are formed by either recessing the plates or placing
distance spacer frames between them. The plates and frames are closed
together with sufficient pressure, normally applied either hydraulically
or by powered screws, to seal the faces and prevent leakage.
After the slurry enters the chamber under pressure and the filtrate
passes through the filter media and is discharged, the press is opened
and the cake removed.
Test Apparatus - Description
The bench scale experiments were performed with a D. R. Sperry and
Company stainless steel 3-5/8 inch laboratory filter press, as shown
in Figure 18. The press was designed to duplicate the operation of
one-half of a filter press cell, The filter media was placed over the
plate at the bottom of the unit, the sludge poured into the chamber
above the filter media, the upper plate with gasket added and the screw
tightened to prevent leakage. The pressure for filtration was supplied
by air from a tank of compressed air.
Procedure
Initial tests performed by D. R. Sperry and Company and later confirmed
by this work showed that a precoat would be necessary for the efficient
operation of the filter press when dewatering acid mine drainage sludge.
The use of a precoat eliminates the need to recycle part of the filtrate,
improves filtrate clarity and eases cake discharge.
Pressure filtration tests were initiated by precoating the pressure
filter. This operation was done by adding enough of a 2 percent precoat
77
-------
Figure 18-PRESSURE FILTRATION APPARATUS
78
-------
slurry (by weight) to the filter to form a cake approximately 1/8 inch
thick as this size precoat was found to be the thinnest precoat which
would not be eroded when the sludge was added to the pressure filter
chamber. Pressure was applied to the precoat slurry and the slurry
filtered to dryness. Next a measured amount of sludge was carefully
added to the pressure filter so as not to disturb the precoat,
pressure was applied, the time recorded and all the filtrate produced
was collected in graduated cylinders. The amount of filtrate collected
in the graduated cylinders was recorded at intervals.
As the tests conducted were of a fairly long duration, it was necessary
to periodically release the pressure, open the unit and add a measured
amount of additional sludge. The fresh sludge was always added before
the level of the sludge in the filter dropped below the top of the sludge
cake so as not to disrupt the continuity of the test.
A test was near completion when either one of two conditions were met:
(1) the pressure filter chamber filled with sludge, (2) a drop or
leveling off of filtrate recovery rate occurred.
When either of the conditions were met the pressure was continued until
the filter cake cracked. After the cake cracked, air was allowed to
flow through the cake in order to increase cake dryness. At the end
of each test the cake was carefully removed from the chamber and the
precoat scraped off. The cake was then measured for thickness and
weighed.
Pressure variation, the use of flocculants and the length of the
filter run were the variables studied in these pressure filtration
tests. It was learned from talks with Calvin Mohr, a representative
of D. R. Sperry and Company and an expert in the area of pressure
filtration, that filtration rates could drop off at high pressures.
This was due either to blinding of the precoat and/or to greater cake
compression which caused a decrease in cake permeability and porosity.
In order to select the optimum operating conditions, various pressures
were examined and three pressures were chosen. The lower pressure,
60 psig, was the lowest pressure that could produce sufficiently high
filtration rates to dewater the large volumes of sludge created by acid
mine drainage treatment. The highest pressure, 100 psig, was the
highest pressure at which the laboratory filter press could be safely
operated. The third pressure, 80 psig, represented an intermediate
pressure between the high and low pressures.
The second important variable investigated was the use of a flocculant
to increase filtration rates. The most efficient flocculant at its
optimum concentration for each sludge, as determined by Buchner funnel
tests, was examined. Each sludge was investigated with and without
79
-------
flocculants and the results compared.
During each test, the amounts of sludge added to the filter and the
amounts of filtrate recovered with increasing time were recorded.
As the cake increased in thickness, the resistance of the cake to
the passage of filtrate increased, eventually reaching a point at which
the time required to remove the cake would be more than offset by the
increased filtration rates obtained after its removal. Establishment
of this point gave the optimum length (time) of a filter run. Having
established the time of a filter run and the volume of sludge dewatered,
it was possible to use this data to determine the size of a filter
press necessary to dewater a given volume of sludge in a given length
of time. At the end of each test, the cake was weighed and measured.
From this data, the volume of cake produced by a given volume of
sludge, under the conditions of the test in question, and the density
(weight per unit volume) of that cake were calculated. The volume
of cake produced must be known for the proper selection of a pressure
unit in order to allow sufficiently large chambers to contain the
cake. The density of the cake was used to calculate the weight which
the unit and its supporting foundation must bear. The percent solids
of the cake was determined in order to evaluate the dewatering effici-
ency of the variables under study and to allow for a better comparison
of the various dewatering methods.
Results
Pressure filtration was found to be a feasible dewatering system foi
all four sludges. The results of tests performed with and without
flocculants added to the four representative sludges at a low pressure
(5 psig) are shown in Table 18. This table shows that the addition of
flocculants gave a large increase in filtrate recovered in one
minute with the final percent solids of the cake being slightly lowered.
However, after talks with and testing by D. R. Sperry and Company it
was decided that sufficiently high rates could be obtained without the
use of flocculants. Also pressures lower than 60 psig should not be
considered since the main advantage of pressure filtration is high fil-
tration rates per unit of filter surface area which requires high
pressures. Low pressures were inefficient from a cost standpoint.
Preliminary tests by D. R. Sperry and Company indicated that a pre-
coat was necessary due to the fine particle content of the sludge.
Recommendations were made that Johns-Manville Hyflo Super-Gel precoat
be used along with Sperry No. 3 Cotton Twill Filter Cloth with Sperry
No. 11 Filter Paper placed over it. Therefore these filter media
were used in all pressure filtration tests.
Results of long duration tests are shown in Figures 19 through 22
80
-------
00
Table 18
Pressure Filtration Tests at 5.0 psig
Sludge
Norton
Norton
Edgell
Edgell
Banning
Banning
Shannopin
Shannopin
Flocculant
None
Decolyte 940
None
Hercofloc 831
None
Coagulant 2350
None
Nalcolyte 673
Filtrate
In One
Min.
(mis)
72
104
29
32
71
145
20
27
Increase
In Filtrate
Recovered
With Floe.
(percent)
44.4
10.3
104.2
35.0
Final
Solids
(percent)
26.3
25.8
17.2
16.0
10.8
8.8
17.7
16.4
-------
ZOOOr
1500
TOTAL
FILTRATE
QO
VOLUME-
MLS.
1000
500
JOO PSI
O PSI
-60 PS/
2 3
TIME-HOURS
Figure 19 - PRESSURE FILTRATION TESTS OF SLUDGE
FROM SHANNOPIN TREATMENT PLANT
-------
3000
oo
OJ
2500
2000
TOTAL
FILTRATE
1500
VOLUME
2 3 4
TIME-HOURS
Figure20-PRESSURE FILTRATION TESTS OF SLUDGE FROM BANNING
TREATMENT PLANT
-------
2000
00
1500
TOTAL
FILTRATE
1000
VOLUME-
MLS.
500
100 PSI
PSI
-60 PSI
0123456
TIME-HOURS
Figure 21 - PRESSURE FILTRATION TEST OF SLUDGE FROM NORTON
TREATMENT PLANT
-------
oo
Ul
2000
1500
TOTAL
FILTRATE
VOLUME-
MLS.
1000
500
0
>80 PSI
-60 PSI
100 PSI
3 4
TIME-HOURS
Figure 22- PRESSURE FILTRATION TESTS OF SLUDGE FROM EDGELL
TREATMENT PLANT
-------
and in Table 19. All four sludges were tested at 60, 80 and 100 psig.
Since Shannopin sludge showed nearly the same filtration rates at
all three pressures, 60 psig was selected as the best operating
pressure.
i
For Banning sludge 100 psig was selected as the best operating pres-
sure due to the large increase in filtration rates at this pressure
as compared to filtration rates at 60 and 80 psig. 100 psig was
the only pressure at which cake data was taken for Banning sludge.
The cake data is presented in Table 19.
Norton sludge produced a very thick cake and had nearly the same
filtration rates at all three pressures. Therefore 60 psig was
selected as the most economical operating pressure. This is the
only pressure reported for Norton in Table 19.
With Edgell sludge the filtration rate dropped off at 100 psig due to
either blinding of the precoat and/or to greater cake compaction
which caused a decrease in cake permeability and porosity. The best
operating pressure for Edgell sludge appeared to be 60 psig, as only
a relatively small increase in filtrate recovery was realized by
increasing the pressure to 80 psig.
In all tests performed a clear filtrate was recovered.
v ^
Porous Bed Filtration
*?
General
Drying beds utilizing sand, coal, or other filtering media have been
used to successfully dewater sewage and industrial sludges. Drying
beds are generally constructed to hold a graded (a gradual change in
particle size in a vertical direction) filtering material. A bed
of coarse gravel is frequently laid over an under drain and then
followed with a finer material. The finest material (placed on top
of the bed) must be of sufficiently small particle size that the voids
between particles are smaller than the particles of the sludge being
filtered. When sludge is introduced onto the surface of the sludge
drying bed, drainage immediately takes place as the filtrate percolates
through the filter media and the solid particles are trapped on the
surface. Following the initial drainage stage, evaporation then
takes place. As the sludge becomes dryer, a point of dryness is
reached when the sludge can be lifted from the surface of the drying bed.
Depending upon the type of sludge being dewatered, conditioning agents
can be added that accelerate the drainage cycle. To prevent rain from
entering the drying bed, a covering can be placed over it.
86
-------
Table 19
Pressure Filtration Cake Data
00
Sludge
Used
Norton
Edgell
Edgell
Edgell
Banning
Shannopin
Shannopin
Shannopin
Pressure
(Ibs/sq. in.)
60
60
80
100
100
60
80
100
Thickness
of
Final Cake
(inches)
7.5000
0.5000
0.3750
0.5625
0.8750
2.3750
2.7500
2.8750
Filtration Time
To Produce
Cake
(minutes)
179
198
138
175
219
170
180
200
Final
Solids Of
Cake
(percent)
20.8
26.2
26.0
26.0
11.8
8.7
12.0
10.9
All sludges were air blown for 5 minutes after break.
-------
Test Apparatus - Description
The test apparatus used for the drying bed experiments was construc-
ted of clear plastic and is shown in Figure 23. Essentially this
apparatus was a tapered tank with a valve fitted at one end.
Preliminary tests were performed to find the smallest filter particle
size that would completely stop the mine drainage sludge from penetrating
the surface. It was found that 40 x 60 mesh wet screened sand or coal
could serve as the top layer of the filter bed.
Coal was the first filter media examined. A wet screened 1.5 inch
thick bed of 1 x 1/4 inch bone coal was laid down followed by 1.5
inches of 1/4 inch thick bone coal. The lower layer of coal, placed
atop the bone coal, was 10 x 20 mesh, the second 20 x 40 mesh and
the top 40 x 60 mesh. This layering of progressively smaller size
fractions formed an approximately 6 inch thick filter bed grading from
coarse at the bottom to fine at the top.
Following the filtration tests using coal as the filter media, high
quartz silica sand was examined. The base of the vessel was covered
by 1.5 inches of screened 1 x 1/4 inch gravel followed by a 1.5 inch
layer of 1/4 inch x 10 mesh gravel. Three one inch layers of sand
were then deposited on the gravel base. The lower layer was 10 x 20
mesh, the middle layer was 20 x 40 mesh and the top layer was 40 x
60 mesh. All mesh sizes given are U. 8. Standard sieve series. The
total filter thickness was 6 inches which duplicated the thickness
and grading of the coal filter. A glass tube was inserted into the
filter media at one end of the vessel to vent the filter system and
allow the filtrate collected at the bottom of the filter to drain
freely. The effective filter area in the test vessel was approxi-
mately 4 square feet.
Procedure
A test was initiated by first filling the vessel with tap water so as
to moisten and protect the bed from erosion. The sludge was then
allowed to flow from a large container by gravity onto a splash pan
located in the center of the filter bed. The splash pan was introduced
as part of the apparatus to minimize bed surface disturbances as the
sludge was introduced. As soon as sufficient sludge was on the bed to
prevent erosion the splash pan was removed.
Two tests were conducted on the coal bed filter. In each test, a
40,000 ml sample of Edgell sludge containing 6 percent solids was
introduced into the vessel. One test was conducted with sludge that
had been conditioned with 111 ppm Hercofloc (shown to be the best
flocculant for this sludge from the conditioning studies) while the
88
-------
(a)
(b)
Figure 23- POROUS BED FILTRATION APPARATUS
(a) TOP 8 FRONT VIEW (b)SIDE VIEW
89
-------
second test was conducted with unconditioned sludge.
A series of three tests was conducted using sand as a filter media.
The first test was performed with a 40,000 ml sample of 6 percent
solids Edgell sludge. A second test was conducted using a 2.3 per-
cent solids Edgell sludge and a third test was performed using 2.7
percent solids Edgell sludge conditioned with 111 ppro Hercofloc.
During each test the clarity of the filtrate was observed and a per-
cent solids determination of the sludge cake was made at various
times following the introduction of the sludge into the drying vessel,
Results
From the preliminary tests conducted, porous bed filtration appeared to
be a technically feasible method of dewatering coal mine drainage sludge.
Data collected from the sand bed and coal bed drying tests is presented
in Table 20. Using an arbitrary figure of 20 percent solids of the dried
cake as a criteria for liftable conditions, it appears from Figure 24
that there is a linear relationship between solids loading (weight of
solids per unit of surface area) and drying time.
The drying tests conducted using flocculant conditioned sludges
indicated that conditioning did not significantly improve sludge de-
waterability in this case. The flocculants used were selected on the
basis of increased filtration rates and would be expected to speed
up the filtration rate (or draining) of the sludge. However, the
filtration phase of porous bed drying is short compared to the
evaporation phase and even a relatively large decrease in the time
required for the filtration phase has only a slight effect on total
drying time.
It was noted that shortly after the drainage or filtration phase
was completed, cracking was observed in the cake. This was due
primarily to shrinkage of the sludge cake during drying and is
similar to "mud cracks".
From the point of view of increasing the rate of drying, cake cracking
appears to hold two advantages. First, as the number of cracks in-
crease, the total surface area of the sludge cake exposed to atmospheric
conditions increases. Secondly, if drying beds were used out of doors,
rain water would be able, at least in part, to move through the cake
surface cracks and filter bed rather than sit on the surface of the
cake., There does not appear to be any advantage between either coal
or sand as a filter media. No significant difference in drying time
90
-------
vo
I-1
Table 20
Data From Drying Bed Tests
Coal Bed
Coal Bed
Sand Bed
Sand Bed
Sand Bed
Test
No.
1
2
3
4
5
Solids
Loading
(lb/sq. ft.)
1.190*
1.026
1.010
0.403
0.0379*
Temperature
(°F) + 5
75
75
75
75
75
Drying
Time**
(Days)
26
25
24
13
12
Volume of Sludge
Dewatered (ml)
40,000
35,000
40,000
40,000
40,000
Treated with 111 ppm Hereofloc 831 flocculant,
**
Time to achieve 20 percent solids content in cake.
-------
SOLIDS
LOADING I
LBS/FT
vO
NJ
10
12
14
16 18 20
DRYING TIME - DAYS
22
24
26
Figure 24 - RELATIONSHIP OF DRYING TIME AND SOLIDS LOADING FOR SLUDGE FROM
EDGELL TREATMENT PLANT
-------
or filtrate quality was observed.
The quality of the filtrate from both the coal filter and sand
filter was quite high as indicated by an absence of non-filterable
solids in the filtrate.
Thermal Spray Drying
General
Thermal spray drying is a technique that uses contact with hot gases
to remove moisture from solids. It involves the following operations:
(1) atomizing the sludge; (2) combining hot gases with atomized sludge
droplets; (3) collecting and separating the dried product and the
air.
Since spray drying operates essentially by evaporating the water
from the sludge directly, the single most important cost variable is
the amount of water to be removed from the sludge or the evaporative
load. The costs of this system, for a given material, tend to vary
inversely with the water content of the feed sludge. In order to
minimize costs, a spray drying apparatus, especially for a low solids
sludge, would most likely be preceded by a mechanical sludge thickening
operation.
Test Apparatus - Description
Spray drying tests were conducted using a Bowen Conical Laboratory
Spray Dryer, which is shown diagramatically in Figure 25.
Air for drying was heated by natural gas burners placed under a hood
after which the air passed into the drying chamber.
The conical drying chamber was approximately 6 feet high, 30 inches in
diameter at its widest point and constructed of type 316 stainless
steel. The drying chamber had an open, uncluttered interior and an
included angle of 40° to prevent an accumulation of the dried product
which would be detrimental to efficiency by interfering with smooth
passage of air and dried product from the chamber.
The cyclone collector was conical in shape and had roughly one-fourth
the volume of the drying chamber. The dried product was discharged
from the bottom of the collector and the air from the top.
Procedure
Each sludge was atomized through a spray nozzle at the top of the
93
-------
SLUDGE FED TO ATOMIZER
BY MOYNO PUMP
THERMOMETER
L
AIR
HEATER
A A A
HEATED BY
GAS BURNERS
i
-ATOMIZER
INSPECTION
PORT
CT
THERMOMETER
/
CYCLONE
COLLECTOR
GLASS
PRODUCT JAR
Figure 25- SPRAY DRYING APPARATUS AFTER BOWEN ENGINEERING
(13)
-------
conical chamber. Sludge was delivered to the atomizer by a Moyno pump.
Several types of atomizers are available; however, the standard model
with six air holes surrounding a central hole through which the sludge
was pumped, proved adequate for mine drainage sludge. The seven hole
nozzle was covered with a rounded cap with a single hole in the center
through which the atomized sludge was sprayed into the drying chamber.
Hot air was drawn into the conical drying chamber near the atomizing
nozzle by a blower located on the hot air exhaust portion of the
apparatus. This same blower pulls the air (unheated) used to atomize
the sludge through the spray nozzle. The hot air inlet is so positioned
as to cause the air to travel through the drying chamber in a spiral
configuration. This spiraling effect increases retention time of
the hot air and sludge in the chamber and promotes good mixing.
Hot air which is now thoroughly mixed with the finely divided dry sludge
particles passes out of the bottom of the chamber, through duct work,
and into a cyclone collector where the sludge particles are removed.
The hot air then passes through the blower and is exhausted. If it
should prove necessary, a wet scrubber could be installed at this point
to remove any remaining sludge particles or perhaps a second cyclone
collector could be utilized.
In the laboratory tests performed at Bowen Engineering, Inc., the
temperature of the heated air entering the conical chamber was held
at 1000°F (the maximum possible with the equipment used). The
temperature of the air leaving the chamber was modified by varying
the flow rate of the sludges. Laboratory tests established the
lowest exit temperature (or highest flow rate) which would allow the
sludge to dry sufficiently so that it would not stick to the chamber
walls or the duct work and clog the equipment. This lowest exit
temperature represented the most efficient use of heat possible in
thermal spray drying and therefore the most economical operating condi-
tions. Data collected on the spray drying tests is summarized in
Table 21.
The four sludges were tested at a solids content different from that
employed in the other dewatering systems (Table 21). The solids contents
used in the spray drying tests were chosen by Bowen Engineering, Inc.
to allow them to better evaluate the spray drying characteristics of
the sludges.
Results
All four sludges could be reduced to a very fine powder of light
brown to reddish brown color with a solids content of about 90 per-
cent. The dewatered solids content was higher than that produced by
any other method under consideration. Whether or not spray drying
would be an acceptable method of dewatering sludge is largely a
matter of economics.
95
-------
Table 21
Test Data From Spray Drying
Run No. 1
FEED CONDITIONS;
Mine Drainage Sludge Norton
Wt. % Solids - Typical 8.0
Wt. % Solids Used in Test 8.5
Spec. Gravity 1.05
£
Temperature °F 70
Feed Rate Mls/Min 560-600
Total Feed, Mis 1,800
OPERATING CONDITIONS;
Inlet Temp. °F
Outlet Temp. °F
Type Heat
Atomizer Type
Atomizing Force,
Air Press, PSIG
Shannopin
2.1
11.0
1.08
70
590-630
4,100
970-985
325
Banning
0.5
9.5
1.08
70
900-961
4,050
990
265-280
Edgell
2.7
1.0
1.00
70
650-700
7,400
990-1,000
305-315
995
340
Direct Gas Used For All
Two Fluid Nozzle Used For All
95
100
95
95
-------
Table 21 (Continued)
•-o
•vj
Run No.
OPERATING CONDITIONS:
(Continued)
Chamber Conditions
MATERIAL BALANCE:
Cyclone Collector, Cms.
Chamber Wall, Gms.
Total Collected, Gms.
Total Solids Fed, Gms.
% Recovery, Wet Basis
Light
Static
Accumula-
tion
105
25
130
160.5
81.0
Damp Spot
Upper cone
260
100
360
486
74.1
Wet Spot
on Cone
and Wall
145
280
425
415
100+
Wet
and
30
nil
30
74
40.6
Wall
Cone
-------
jtentrifugation
General
Centrifugation is a method of separating materials of different densi-
ties by the use of centrifugal force. There are many types of commer-
cial centrifuges but all consist of a feed system which delivers the
material to be dewatered, a revolving basket or bowl to collect the
solid particles, a discharge line and a system for removing the built
up solids.
Material to be dewatered is fed into the bowl or basket and during
the operation solids are forced away from the axis of rotation of
the bowl and deposited on the wall, while the centrate fills the bowl.
When the bowl is filled to capacity, the effluent is discharged,
generally over the sides of the bowl, and exits through a discharge
line.
The solid material is then removed by an automatic scraper blade or
some other device designed to remove the material.
A solid bowl centrifuge of the type studied in this work has two
methods of solids removal. The first method, skimming, is performed
whenever the clarity of the effluent drops below an acceptable level.
Skimming removes the softer, less compact sludge solids. The second
method of solids removal involves scraping the harder, more compact
sludge solids collected along the circumference of the bowl. These
solids are removed when they have accumulated to the point that they
have reduced the capacity of the bowl and made the time between
skimming operations prohibitively short.
Test Apparatus - Description
The bench scale experiments were performed with a 14" diameter basket
Fletcher Mark III centrifuge of the solid bowl type which operates
at variable speeds and is electrically powered. The machine was rented
from Sharpies-Stokes Division of Pennwalt Corporation and is shown in
Figure 26. This centrifuge was designed to duplicate a large indus-
trial type centrifuge.
A gravitational feed system was used to supply sludge to the centri-
fuge. The sludge was siphoned from an elevated 55 gallon drum through
a 1/2 inch pipe equipped with a globe type valve into a secondary
20 gallon cylindrical plastic container. The sludge was discharged
from the secondary container into the centrifuge. Various flow rates
to the centrifuge were maintained by the use of a predetermined piezo-
metric head within the secondary container for each flow rate. The
98
-------
Figure 26- CENTRIFUGATION APPARATUS
99
-------
sludge was kept thoroughly mixed by the use of a 1/2 horsepower
electrically powered Lightnin mixer.
The solid bowl, which was cylindrical shaped, was 14 inches in diameter
by 6 inches in height and had a 1 7/8 inch lip ring around the top.
A truncated cone approximately 6 inches in diameter at the base and
2 inches in diameter at the top by 4 inches in height was bolted to
three mounts at the bottom of the bowl. These mounts were approximate-
ly 1/4 inch in height and one inch square; therefore three slots 1/4 ,
inch in height were situated under the conical section. Sludge entered
the centrifuge through a 1 inch diameter pipe into the top of the
conical section and was dispersed uniformly under the bottom of the
cone; this assures flow throughout the bowl from bottom to top. Cen-
trate flowed over the lip ring on the top of the bowl when the bowl's
capacity of 1.5 gallons was reached.
The discharge line was a 2 inch hose running from the bottom of the
centrifuge to the drain.
The sludge skimmer pipe was 3/8 inch diameter and passed through the
lid of the centrifuge with one end of the pipe (entrance) inside the
bowl and pointing in the opposite direction to the bowls rotation.
The exit end of the skimmer protruded vertically from the top
of the centrifuge and was bent 90° to the front of the machine. A
rachet arrangement was used to advance the skimmer manually from the
center of the bowl towards the side while the bowl was in rotational
operation. Centrifugal force in the bowl forced the thick sludge
out of the pipe when the skimmer was activated.
Procedure
Sludge to be used for each test was put into a 55 gallon drum equipped
with a Lightnin mixer and a siphon pipe. The mixer was started
and it continued to run for the duration of the test to keep the sludge
thoroughly mixed. The siphon was started and sludge was added to the
secondary plastic container and the desired predetermined piezometric
head for each particular run was obtained. The flow rate was checked
by measuring the amount of slurry which flowed in one minute.
The variable speed centrifuge was activated and stabilized at a
rotational speed of 2750 revolutions per minute. This speed vras re-
commended by the manufacturers of the Sharpies-Fletcher centrifuge,
and was based on acid mine drainage sludge tests performed earlier
using a limestone sludge.
At the beginning of each test the time was recorded and samples of
the effluent discharged were taken at one minute intervals, starting
100
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with the initial discharge and ending with the termination of a test.
As the test progressed the howl accumulated more and more sludge which
reduced its effective volume. The reduction of the bowl's effective
volJime reduced the retention time of the slurry which reduced the
effectiveness of solids removal. The centrifuge operation was con-
timied until the effluent discharged had approximately the same per-
cent solids concentration as the feed going into the howl; this is
done hy comparing the clarity of a bottle of sludge feed to a bottle
of effluent.
Sludge feed was then stopped, but the operation of the centrifuge
continued. The effluent which remained in the bowl was skimmed by
advancing the skimmer pipe into the bowl until the liquid-solid inter-
face was reached. At this point the distance from the skimmer to the
outer circumference of the bowl was recorded and was a direct measure of
the amount of sludge in the bowl. Most of the sludge which remained was
skimmed off; however, a very compact sludge on the side of the bowl
cannot be removed by the skimmer for if contact should occur between
the skimmer pipe and the bowl damage would occur. The centrifuge was
then stopped. The compact cake, called the bowl cake or bowl solids,
which remained was measured for thickness at the top, middle and bottom
of the bowl and recorded and the sludge scraped from the side of the
bowl.
The most important parameters of the test were centrifugal force,
(speed-diameter) feed rate and characteristics of the sludge. Tests
were run at flow rates of 1/2, 1, 1-1/2, 2, 2-1/2 and 3 gallons per
minute for non-flocculated sludges. If the tests which were per-
formed at lower feed rates lasted 5 minutes or less, further tests
were not made at increased feed rates as, according to the manufac-
turers, shorter runs would be impractical. Each sludge was also
tested at 1/2 gallon per minute with the correct concentration of
flocculant added as determined earlier in vacuum filtration tests.
Samples of feed, effluent discharged from beginning to end of run
at selected intervals, skimmer sludge and sludge deposited on the
wall of the bowl were submitted for percent solids analysis. Due
to the length of each run many effluent discharge samples were col-
lected and several were discarded as they were similar in clarity.
Results
Centrifugation was found to be a feasible dewatering system for
Norton, Shannopin and Banning sludges. Edgell sludge was not tested
due to difficulties encountered in obtaining this sludge in suffi-
ciently large quantities. The Edgell settling lagoon is located far
from the nearest road and samples must be carried out by hand, making
the collection of several hundred gallons of sludge difficult.
101
-------
As would be expected all sludges show a decrease in the time the
centrifuge can be operated as the feed rate of sludge increases or
as the solids content of the feed sludge increases. This is due
to the increase in sludge volume deposited in the bowl with tine.
The more rapidly the sludge accumulates, the less the effective
volume of the bowl and the less effective its removal of solids.
Figure 27 shows the results of the tests on Shannopin sludge. The
length of time the centrifuge can be operated before skimming de-
creases with increasing feed rates as shown by Curves 1 through 3.
For Curves 4 and 5 the feed rate has reached the point that centrate
clarity drops to an unacceptable level (below 90 percent recovery)
in less than a minute. Curve 3 appears to be a good combination
of feed rate and length of run and would represent the feed rate at
which the greatest volume of sludge could be dewatered per unit of
time.
Curve 6 shows the effect of a flocculant on Shannopin sludge. Since
Curve 6 differs very little from Curve 1 (the same feed rate) it
would appear that little advantage would be gained in applying this
flocculant.
Figure 28 shows the results of centrifugation tests on Banning sludge.
Banning sludge behaved similarly to the Shannopin sludge with Curve
3 again* representing the maximum practical feed rate. The use of a
flocculant in this case increased the length of time the machine
could be operated (Curve 1) before skimming and would increase the
amount of sludge which could be dewatered by the machine.
Figures 29 and 30 are for Norton sludge. Figure 29 shows the
rate at which the length of a run decreases as the solids content
of the feed sludge increases. Curve 4 represents the test made
using a flocculant. Curve 4 drops before Curve 2, a test of the
same flow rate and an even higher solids content, thvis the flocculant
decreased the capacity of the machine. Figure 30 shows the results
of increasing the feed rate of Norton sludge. Curve 2 represents
the maximum feed rate under these conditions. Curves 1 and 4 may
be compared to determine the effect of increasing the feed solids
content of Norton sludge at a flow rate of 1 gpm.
Tables 22 through 24 present the solids content of the dewatered
sludge. Norton sludge dewatered by centrifugation showed the highest
solids content and Banning sludge the lowest.
Summary of Results on Dewatering Attempts
It was found that it was technically feasible to dewater all four
sludges by any of the six dewatering systems studied with the ex-
102
-------
IOO
80
60
EFFICIENCY
OF SOLIDS
40
REMOVAL-
PERCENT
20
CURVE
I
2
3
4
5
—fc^T*
FEED RATE
GPM
FEED SOLIDS
0.5
I.O
1.5
2.0
2.5
0.5
Wco/yte 673 Added
2.27
2.08
2.09
2.04
2.24
1.85
i
i
8 12
TIME-MINUTES
16
20
24
Figure 27 - CENTRIFUGATION TESTS OF SLUDGE FROM SHANNOPIN TREATMENT
PLANT.
-------
100 r
80
60 -
EFFICIENCY
OF SOLIDS
40
REMOVAL-
PERCENT
20
8
CURVE
I*
2
3
4
5
6
FEED RATE FEED SOLIDS
GPM %
I
I
12 16
TIME-MINUTES
0.99
0.64
0.68
0.69
0.72
0.73
20V 25 30 35 40
Coagulant 235O Added.
Figure 28-CENTRIFUGATION TESTS OF SLUDGE FROM BANNING TREATMENT PLANT.
-------
100
80
EFFICIENCY
OF SOLIDS
60
REMOVAL-
PERCENT
o
Ui
40
20
CURVE
I
2
3
4
FEED RATE
GPM
0.5
0.5
0.5
0.5
FEED SOLIDS
%
1.54
5.52
10.05
3.77
*Decolyte940 Added
_L
J_
_L
_L
J_
8 10 12 14 16 18 20 22 24 26 28 30
TIME-MINUTES
Figure 29 - CENTRIFUGATION TESTS OF SLUDGE FROM NORTON TREATMENT PLANT.
-------
100
80
EFFICIENCY
OF SOLIDS
REMOVAL-
PERCENT
60
40
20
8
CURVE
I
2
3
4
FEED RATE FEED SOLIDS
GPM %
1.0
1.5
2.0
1.0
2.09
2.48
2.73
6.12
12 16
TIME-MINUTES
20
24
Figure 30- CENTRIFUGATION TESTS OF SLUDGE FROM NORTON TREATMENT
PLANT.
-------
Table 22
Centrifugation Tests
Shannopin Treatment Plant Sludge
Figure
Number
27
27
27
27
27
27
Curve
Number
1
2
3
4
5
6*
Feed Solids
(percent)
2.27
2.08
2.09
2.04
2.24
1.85
Flow Rate
(gpro)
0.5
1.0
1.5
2.0
2.5
0.5
Bowl Solids
(percent)
33.4
33.6
32.5
36.9
35.4
26.6
Skimmer Solids
(percent)
11.0
8.8
9.0
8.0
7.7
13.8
Nalcolyte 673 added
-------
Table 23
Centrifugation Tests
Banning Treatment Plant Sludge
o
00
Figure
Number
28
28
28
28
28
28
Curve
Number
2
3
4
5
6
1*
Feed Solids
(percent)
.64
.68
.69
.72
.73
.99
Flow Rate
(gpm)
0.5
1.5
2.0
2.5
3.0
0.5
Bowl Solids
(percent)
8.8
8.4
8.7
8.6
8.1
11.4
Skimmer Solids
(percent)
5.1
3.8
4.6
5.0
5.6
9.2
y-
Coagulant 2350 added
-------
Table 24
Centrifugation Tests
Norton Treatment Plant Sludge
Figure
Number
29
29
| 29
29
30
30
30
30
Curve
Number
1
2
3
4*
1
2
3
9
Feed Solids
(percent)
1.54
5.52
10.05
3.77
2.09
2.48
2.73
6.12
Flow Rate
(gpm)
0.5
0.5
0.5
0.5
1.0
1.5
2.0
1.0
Bowl Solids
(percent)
41.3
53.7
64.1
63.0
44.9
50.5
55.8
51.8
Skimmer Solids
(percent)
12.9
19.3
17.5
22.1
11.6
13.5
12.8
19.2
Decolyte 940 added
-------
ception that precoat rotary vacuum filtration was found not to he
applicahle to Norton sludge. Conventional rotary vacuum filtration
was technically feasible for all sludges, hut to be practical for use
on Shannopin, Edgell and Banning sludges additional thickening or
special equipment would be necessary.
Porous bed filtration and all systems utilizing a precoat produced
a filtrate of sufficient clarity to be discharged directly into a
stream. Thermal spray drying produced only water vapor which could
be discharged directly into the atmosphere. Both conventional rotary
vacuum filtration and centrifugation produced water of a relatively low
clarity and would require recycling to the clarifier.
No system showed a significant advantage in solids content of de-
watered sludge produced except for thermal spray drying. The other
dewatering systems generally produced sludge cakes of from 10 to 30
percent solids while the thermal spray drying method produced dried
sludge containing over 90 percent solids.
Two systems, pressure filtration and porous bed filtation were
noticeably free of operational problems during bench scale testing.
However, the bench scale testing of porous bed filtration did not
include an evaluation of cake removal systems, a possible source of
difficulty.
110
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SECTION VII
ECONOMIC EVALUATION OF SLUDGE DEWATERING ATTEMPTS
The purpose of an economic evaluation of sludge dewatering systems
is to provide a relative cost comparison of the six dewatering
systems studied. To estimate highly accurate cost figures for any
particular dewatering system, actual pilot plant scale tests, rather
than bench scale tests, should be performed. The cost figures pre-
sented here are primarily intended to be used as guides for comparison
of systems in respect to each other.
In order to make a realistic economic evaluation of the various pro-
cesses, costs must be based on certain assumptions. To facilitate the
best possible understanding of this analysis a complete list of the
assumptions is presented:
1. Straight line depreciation over complete life of equipment.
2. Location - Morgantown, West Virginia.
3. Time - Spring of 1972
4. Operation of equipment 24 hours per day, 365 days per year with
excess size to facilitate periodic shut downs.
5. Maintenance assumed to be 6 percent of total capital cost.
6. Fuel: $0.13 per gallon, #2 fuel oil, 130,800 BTU's per gallon.
7. Electricity: $0.0175 per kilowatt hour.
8. Labor Cost: $6.00 per hour, includes shift differentials, over-
time premium, payroll overhead, supervision and fringe benefits.
9. Dewatering system to be constructed simultaneously x
-------
watered was characterized as:
Shannopin, 180,000 gallons/day at 2.1 percent non-filterable solids
Banning, 360,000 gallons/day at 0.5 percent non-filterable solids
Norton, 50,000 gallons/day at 8.0 percent non-filterable solids
Edgell, 100,000 gallons/day at 2.7 percent non-filterable solids.
13. Retention time required for all clarifiers assumed to be one hour.
A list of factors not considered in the evaluation would include:
1. Miscellaneous supplies
2. Laboratory costs
3. Real estate taxes
4. Insurance !
5. Working capital
6. Land costs
7. Differentials in costs of transportation and disposal due
to dryness of dewatered sludge
8. Plumbing and heating of building
Equipment specifications were determined after consultation with the
respective manufacturers using extrapolated data collected during ex-
perimentation. Capital costs are totally on price quotations from the
manufacturers except for porous sand bed filtration costs which are
based upon a recent study by Barnard and Eckenfelder.(15)
Operational costs were based on correspondence with equipment manufac-
turers, material suppliers or local utilities.
As noted in the sludge dewatering section of this report, some of the
dewatering systems were evaluated with a flocculant added to the sludge.
The primary economic advantage obtained by the addition of a flocculant
would be to increase filtration rates which would increase the efficiency
of the dewatering unit. If the efficiency of a unit could be suffi-
ciently increased, it would be possible to utilize a smaller unit
thereby reducing capital costs.
Results obtained by using a flocculant were generally favorable for
reducing equipment sizes. However at the concentrations determined in
laboratory testing the savings in equipment would in all cases be off-
set in a very short time by the cost of the flocculant. Flocculant
112
-------
treatment of the sludges may have produced better economic results if
concentrations would have been based on economic optimization rather
than maximization of filtration rates.
The effluents from centrifuging and conventional vacuum filtration
were felt to lack sufficient clarity for direct stream discharge and
therefore xrould require additional treatment. The simplest and most
efficient method of accomplishing this would be to recycle all of
the effluent through a thickener clarifier. However, in all cases,
the cost of the increased size clarifier required to handle the
additional liquids did not significantly alter the final relative
costs.
Conventional Vacuum Filtration
Evaluation of bench scale experiments proved that only the Norton
Treatment Plant sludge (limestone sludge) possessed physical proper-
ties acceptable for dewatering by conventional; vacuum filtration. This
held true for sludges treated with flocculants as well as those un-
treated. In all cases tested, conventional vacuum filtration produced
a filtrate unacceptable for discharge directly into a stream. There-
fore all filtrate must be recycled through the clarifier, from which
the overflow could be discharged into any nearby stream.
After correspondence with Mr. Lewis ArabiadD of Eimco Processing
Machinery Division, Envirotech Corporation, it was determined that
one 6 foot diameter by 6 foot face drum filter with a belt discharge
would suffice for the assumed Norton dewatering system. The cost
was estimated to be $3.40 per 1,000 gallons of sludge dewatered.
Adding this dewatering system to an existing neutralization system would
increase total cost by $0.01 per 1,000 gallons of acid water.
Complete cost data is presented in appendices, Table 1.
Rotary Precoat Vacuum Filtration
Results of rotary precoat vacuum filtration as described in the de-
watering section indicate that a cycle time of 20 seconds filtration,
15 seconds drying and 10 seconds for cutting was optimal for filtration
of the three lime sludges. Norton sludge was not amenable to this
dewatering system. Costs were estimated to range from $1.40 to $3.50
per 1,000 gallons of sludge dewatered. With this dewatering system
added to an existing neutralization system additional costs would amount
to $0.35 to $1.80 per 1,000 gallons of acid water depending on the
treatment plant. Complete cost data is presented in the appendices,
Tables 2 through 4.
113
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Pressure Filtration
Laboratory experiments showed that all four sludges could he de-
watered by pressure filtration. The filter media consisted of Johns-
Manville Celite 501 supported horizontally by a cloth. The filter
media is washed away with the dried sludge at the end of each filter
cycle. The filtrate from this process was of sufficient clarity for
direct discharge into a stream.
After consultation with Calvin Mohr,^12' of D. R. Sperry and Company,
required press sizes weJre determined for the respective treatment
plants. All presses were of the 48 inch EHCL type, with the number of
plates and frame sizes dependent upon the particular sludge. Due to
the filter sizes a plate shifter for each filter press would be re-
quired to handle the plates and frames during the cleaning process.
Two men would be required to disassemble, clean, and reassemble each
system. In the systems with more than one press the operator would
rotate press units cleaning each press at the end of its cycle.
Electric pumps are used to provide pressure for the filtering pro-
cess.
Precoat use was based on minimum requirements without erosion, this
was determined to be 0.125 of an inch in laboratory tests.
The costs were estimated to range from $1.70 to $7.30 per 1,000 gallons
of sludge dewatered. On the basis of total acid water to be treated,
the additional cost of dewatering would range from $0.02 to $2.40
per 1,000 gallons of acid water. Complete cost data is presented in
Tables 5 through 8.
Porous Bed Filtration
Sewage sludge is generally applied to drying beds at a depth of 8 to
12 inches.(16) As no information on optimum depth for acid mine drainage
sludge is available, a depth of one foot is assumed. A cubic foot of
Edgell sludge at 2.7 percent solids would contain 1.685 pounds of
sludge. Assuming a linear relationship between solids loading and
drying time and projecting the data from Figure 24, drying time
for a solids loading of 1.685 lbs/ft.2 is 34 days.
In a study by Barnard and Eckenfelder the capital costs of sludge
drying beds were estimated at $1.15 per square foot.(15) With the
assumed 100,000 gallons of sludge per day from the Edgell Treatment
Plant and 34 days for a drying cycle, 454,580 square feet would be
required for one complete cycle. This would require a capital cost
114
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of $522,800.00. Assuming a 10 year life for the filter bed the vearlv
capital cost would be $52,280.00 or $143.00 per day. At the afore- '
stated clarifier underflow rate of 100,000 gallons" per day capital
costs would be reduced to $14.30 per 1,000 gallons of sludge dewatered.
Operational costs from the same study were calculated reflecting
solids content. Their relationship was,
Operating cost (c per 1000 gallons) =
S x 1.2 (0.206 + 0.94 (1000/S0'5)
Q x 3650
0 = flow ratio in millions of gallons per day
S » total solids in pounds per day.
With the assumed clarifier underflow at 2.7 percent solids, 22,520
pounds of solids would be produced each day. Using these rates, an
operational cost of $4.80 per 1,000 gallons of sludge would be esti-
mated.
Total capital and operational costs for porous bed filtration of the
Edgell Treatment Plant sludge would be estimated at $19.10 per 1,000
gallons of clarifier underflow sludge. However, this dewatering system
would increase total cost by $1.90 per 1,000 gallons of acid water.
Since the method of computation of dewatering costs used by Barnard
and Eckenfelder(15) differ in some respects from that used in the
other sections of this evaluation, these figures may not be directly
comparable to the rest of this evaluation.
Thermal Spray Drying
Laboratory analysis of thermal spray drying was conducted by Bowen
Engineering, Inc. U7) Their recommendations as to plant requirements
were based on the dryer operating temperature, the quantity of moisture
to be evaporated and ease of sludge moisture release.
Bowen Engineering determined the optimum operating temperatures as
an inlet temperature of 1200°F and an outlet temperature of approxi-
mately 300°F. The quantity of moisture to be evaporated was extra-
polated from the assumed plant volumes and percent solids. The specific
gravities of the four representative sludges were not significantly
larger than 1.00 (except for Norton at 1.05) so that the volume to
weight ratio approximates that of water.
Cost quotations for equipment include a direct fired air heater,
flame protection equipment, hot air inlet ducts, chamber outlet ducts,
115
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a cyclone collector, a scrubber, a main exhaust fan, all recording
and controlling instrumentation, atomization equipment, structural
support steel, all motors and start up service. Optional equipment
which would be required for sludge dewatering are a feed pump, penthouse
and access steel.
Most spray dryers use gas or oil direct fired air heaters; however,
an indirect system can be utilized using steam. Because of the un-
availability of large amounts of natural gas for commercial use in
the Morgantown, W.Va. area; #2 fuel oil was chosen as the best
alternative for air heating. Oil prices are based on conversation with
a local marketing representative of Atlantic Richfield Company.
Power consumption is basically for the operation of the blowers and
the feed pump. Additional electricity is used for control instrumen-
tation; however, it is a small percentage of total energy requirements.
Continuous attendance during operation is not required by the systems.
A full time operator is not required; however, upon advice from the
manufacturer, costs were determined on the basis of one full time
worker. This allows for infrequent periods when more than one worker
is required. Costs were estimated to range from $15.00 to $19.00
per 1,000 gallons of sludge dewatered. Adding this dewatering system
to an existing neutralization system would increase total cost by
$0.05 to $11.10 per 1,000 gallons of acid water depending on the treat-
ment plant. Complete cost data is presented in the appendices, Tables 9
through 12.
The relatively high cost of spray drying could perhaps be justified
if transporting and disposing of the final dewatered sludge became a
major cost factor. The spray dried sludge (approximately 90 percent
solids) is much drier than sludge produced by the other dewatering
methods. Since more water is removed, this sludge becomes relatively
cheaper to transport and requires less area for disposal.
Centrifugation
Laboratory experiments showed that three sludges examined were accept-
able for dewatering by centrifugation. Edgell Treatment Plant sludge
was not tested. In all cases, the centrate produced was unacceptable
for direct discharge into a stream. Therefore all centrates would
have to be recycled through a thickener clarifier to obtain sufficient
clarity.
After correspondence with Mr. R. A. Armstrong of Sharpies-Stokes
Division, Pennwalt Corporation, the required number of Sharpies Sludge
Pak SP-6500 centrifuges was determined for each treatment plant. The
116
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40 horsepower drive motor is the primary consumer of electric power;
however, small additional amounts are required for instrumentation and
control.
Costs were estimated to range from $1.80 to $4.50 per 1,000 gallons
of sludge dewatered. The increase in total cost of this dewatering
system over an existing neutralization system would be from $0.01 to
$1.73 per 1,000 gallons of acid water. Complete cost data is presented
in the appendices, Tables 13 through 15.
Summary
From the presented cost data it can easily be observed that no one
method of dewatering was absolutely advantageous to all acid treatment
plant sludges. Dewatering method selection must be related to the
particular treatment plant, taking into consideration variables such
as acid water compositions, method of neutralization, quantity of sludge
produced and final disposal of the dewatered sludge. With respect to
each plant, significant cost differences occurred in both costs based on
gallons of sludge and gallons of acid water. Summation of cost data for
each treatment plant is presented in Tables 25 through 28.
Based on both the assumed amount of sludge and the amount of acid water,
centrifugation was deemed most economical for Shannopin sludge. This
sludge could be dewatered at a cost of $1.80 per 1,000 gallons of sludge
or $1.30 per 1,000 gallons of acid water.
Banning Treatment Plant sludge could be dewatered at $1.40 per 1,000
gallons of sludge by both rotary precoat vacuum filtration and centri-
fugation. However, on the basis of acid water the cost would be $0.70
per 1,000 gallons of acid water.
Norton sludge dewatering would cost $3.30 per 1,000 gallons of sludge
by conventional vacuum filtration. However, either conventional vacuum
filtration or centrifugation systems could dewater the sludge at a cost
of $0.01 per 1,000 gallons of acid water.
It should be noted again here that only the Norton Treatment Plant
sludge possessed physical characteristics required for the conventional
vacuum filtration system of dewatering. Therefore no economic evaluation
was made with respect to the other three sludges using the conventional
vacuum filtration system of dewatering.
Edgell Treatment Plant sludge was most economically dewatered using
the rotary precoat vacuum filtration method. Based on sludge volume
dewatering cost was $3.50 per 1,000 gallons of sludge. Using acid
water as a criteria the cost was $0.35 per 1,000 gallons of acid water.
117
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Variations in cost occur between analyses based on sludge and acid
water because of assumptions made as to their respective solids content.
Thickening results in a denser sludge that requires less dewatering to
reach relative dryness.
The cost figures presented in Tables 25 through 28 are both for 1,000
gallons of sludge dewatered and as an add on cost per 1,000 gallons of
acid water treated. Care must be taken in comparing the different de-
watering systems on the basis of an add on cost per 1,000 gallons of
acid water treated. As a result of increasing the clarifier size, or the
retention time of the clarifier, the volume of sludge can be reduced
with respect to the original acid water volume. In effect, the same
volume of acid water produces a thicker sludge with relatively less
volume. Naturally, a thicker sludge is relatively less expensive
to dewater; however, the larger clarifier was not included in the cost
calculations. The clarifier is normally a part of the neutralization
rather than the dewatering system. Therefore in this analysis the
cost of dewatering per 1,000 gallons of acid water is biased in favor
of treatment systems producing relatively thicker sludges.
118
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Table 25
COST SUMMATION FOR SHANNOPIN TREATMENT PLANT
COSTS BASED ON ASSUMPTIONS MADE IN ECONOMIC EVALUATION SECTION OF THIS REPORT
Capital
Cost
Operational
Cost
Cost per 1,000
Gallons Sludge
Conventional
Vacuum Filtration**
|l! Rotary Precoat
Cost per 1,000
Gallons Acid Water*
Vacuum Filtration
Pressure Filtration
Porous Bed Filtration**
Thermal Spray Drying
Centrifugation
$85,800.00
$181,200.00
$714,800.00
$381,300.00
$428.00/day
$562.50/day
$2,591.50/day
$219, 30/ day
$2.50
$3.40
$15.50
$1.80
$1.80
$2.40
$11.10
$1.30
Cost of dewatering the sludge produced by the neutralization of 1,000 gallons of acid water.
**
System not tested with this sludge.
-------
Table 26
COST SUMMATION FOR BANNING TREATMENT PLANT
COSTS BASED ON ASSUMPTIONS MADE IN ECONOMIC EVALUATION SECTION OF THIS REPORT
Capital
Cost
Conventional
Vacuum Filtration**
Rotary Precoat
Vacuum Filtration
Pressure Filtration
5.
Porous Bed Filtration**
Thermal Spray Drying $1,434,500.00
Centrifugation $762,500.00
Operational
Cost
$5,005.80/day
$282.10/day
Cost per 1,000
Gallons Sludge
$85,800.00
$144,900.00
$499.00/day
$563.50/day
$1.40
$1.70
$15.00
$1.40
Cost per 1,000
Gallons Acid Water*
$0.75
$0.80
$7.50
$0.70
Cost of dewatering the sludge produced by the neutralization of 1,000 gallons of acid water.
**
System not tested with this sludge.
-------
Table 27
COST SUMMATION FOR NORTON TREATMENT PLANT
COSTS BASED ON ASSUMPTIONS MADE IN ECONOMIC EVALUATION SECTION OF THIS REPORT
Conventional
Vacuum Filtration
Rotary Precoat
Vacuum Filtration**
Pressure Filtration
Porous Bed Filtration**
Thermal Spray Drying
Centrifugation
Capital
Cost
$52,000.00
$436,600.00
$152,500.00
Operational
Cost
$43,500.00 $160.90/day
$351.20/day
$836.80/day
$181.60/day
Cost per 1,000
Gallons Sludge
$3.30
$7.30
$19.00
$4.50
Cost per 1,000
Gallons Acid Water*
$0.01
$0.02
$0.05
$0.01
Cost of dewatering the sludge produced by the neutralization of 1,000 gallons of acid water.
**
System not tested with this sludge.
-------
Table 28
COST SUMMATION FOR EDGELL TREATMENT PLANT
COSTS BASED ON ASSUMPTIONS MADE IN ECONOMIC EVALUATION SECTION OF THIS REPORT
Conventional
Vacuum Filtration**
Rotary Precoat
Vacuum Filtration
Pressure Filtration
Porous Bed Filtration
Thermal Spray Drying
Centrifugation**
Capital
Cost
$76,600.00
$139,500.00
$522,800.00
$576,800.00
Operational
Cost
$331.30/day
$568.60/day
$143.00/day
$l,573.80/day
Cost per 1,000
Gallons Sludge
Cost per 1,000
Gallons Acid Water*
$3.50
$6.00
$19.10
$17.30
$0.35
$0.60
$1.90
$1.73
Cost of dewatering the sludge produced by the neutralization of 1,000 gallons of acid water.
**
System not tested with this sludge.
-------
SECTION VIII
ACKNOWLEDGMENTS
Mr. Kdwin B. Wilson, now associated with Bethlehem Steel Corporation,
submitted the proposal for this project and his efforts are gratefully
acknowledged.
Thanks are due to Russell W. Frum who was the author of the Economic
Evaluation Section of this report and Larry G. Shaffer who authored
portions of the Sludge Dewatering Section of this report. Messrs.
Russell W. Frum and Larry G. Shaffer also performed much of the bench
scale tests during the data collection phase of this report.
The financial support of this project by the Environmental Protection
Agency, Roger C. Wilnoth, Project Officer, and the State of West
Virginia, Coal Research Bureau, Joseph W. Leonard, Director, is
acknowledged v/ith sincere thanks.
Mr. Richard B. Muter, Mr. Kenneth K. Humphreys and Mr. William F.
Lawrence are acknowledged for their aid in the preparation of the
final report of this project. Mr. Richard Muter also developed the
acid water collection and analysis procedure detailed later in this
report and assisted in the interpretation of the results of the
chemical analyses. Mr. Charles R. McFadden prepared the illustrations
for this report and Mr. Lionel L. Craddock prepared the photographs.
The cooperation of Miss Martha E. Fekete in typing this report is
gratefully acknowledged.
123
-------
SECTION IX
REFERENCES
1. Salotto, B. V.; Earth, E. F.; Ettinger, M. B.; and Tulliver,
W. E., "Procedure for Determination of Mine Waste Acidity,"
Federal Water Pollution Control Administration, Cincinnati, Ohio
(October 1966).
2. Standard Methods for the Examination of Water and Wastewater,
American Public Health Association, Inc., Twelfth Edition (1965).
3. Hall, E. A., Chemical Analysis of Coal Mine Drainage, Consolidation
Coal Company, pp 10 (August 1960).
4. FWPCA Method for Chemical Analysis of Water and Wastes, U. S.
Department of Interior (November 1969).
5. Wilmoth, R. C. and Scott, R. B., "Neutralizing of High Ferric Iron
Acid Mine Drainage," Third Symposium on Coal Mine Drainage Research,
Mellon Institute, Pittsburgh, Pennsylvania (1970).
6. Doe, P. W.; Benn, D.; and Bays, L. R., "The Disposal of Washwater
Sludge by Freezing," Journal Institute of Water Engineers, 19,
pp 251-275 (1965).
7. Clements, G. S.; Step hens on, R. J.; and Regan, C. J., "Sludge
Dewatering by Freezing With Added, Chemicals," Journal Institute
of Sewage Purification, Part 4, pp 318-337 (1950).
8. Cheng, C. Y.; Updegraff, D. M.; and Ross, L. W., "Sludge De-
watering by High-Rate Freezing at Small Temperature Differences,"
Environmental Science and Technology, 4^ No. 12, pp 1145-1147
(December 1970).
9. Doe, P. W.; Benn, D.; and Bays, L. R., "Sludge Concentration
by Freezing," Water and Sewage Works, 112, No. 11, pp 401-406
(November 1965).
10. "Filtration Leaf Test Procedures," Dorr-Oliver, Incorporated,
Stamford, Connecticut, Bulletin No. 25ILT, pp 5-6.
11. Arabia, L., Personal Communication, Eimco Processing Machinery
Division, Envirotech Corporation, Pittsburgh, Pennsylvania
(March 1972).
12. Mohr, C., Personal Communication, D. R. Sperry and Company,
North Aurora Illinois (October 1971).
125
-------
13. "Laboratory Spray Dryers," Bowen Engineering, Inc., North
Branch, New Jersey.
14. Kraufe, R., Personal Communication, Sharpies-Stokes Division,
Pennwalt Corporation, Warminster, Pennsylvania (January 1972).
15. Barnard, J. L. and Eckenfelder, W. W., Jr., "Treatment-Cost
Relationships For Industrial Waste Treatment," Technical
Report Number 23, Environmental and Water Resources Engineering,
Vanderbilt University, Nashville, Tennessee (1971).
16. Eckenfelder, W. W. and Ford, D. L., Water Pollution Control,
Jenkins Book Publishing Company (1970).
17. Hall, J. R., Personal Communication, Bowen Engineering, Inc.,
North Branch, New Jersey (July 1971).
18. Armstrong, R. A., Personal Communication, Sharpies-Stokes
Division, Pennwalt Corporation, Warminster, Pennsylvania (April
1972).
126
-------
SECTION X
APPENDICES
Table 29
Conventional Vacuum Filtration - Norton Treatment Plant Sludge
(Preliminary Prices - Spring 1972)
Capital Costs
6 foot diameter x 6 foot
drum filter with accessories $30,000.00
Construction and Installation:
35 percent of equipment 10^500.00
Total Equipment Cost $40,500.00
Equipment Depreciation:
10 years expected life
no salvage value
Building: 300 sq. ft. at
$10.00/sq. ft. 3,000.00
Building Depreciation:
30 years expected life
no salvage value
Total Capital Cost $43,500.00
Operational Costs
Maintenance: 6 percent of
total capital cost
Electricity: 530 KWH/day
at $0.0175 KWH
Labor: 24 hours at $6.00/hour
Total Capital and Operational Cost
Assuming 50,000 gallons
clarifier underflow per day
$4,050.00/year
$100.00/year
$11.10/day
0.30/day
Assuming 20,000,000 gallons acid
water per day
127
$2,790.00/year 7.60/day
9.30/day
$144.00/day
$172.30/day
$3.30/1,000
gallons
sludge de-
watered
$0.01/1,000
gallons acid
water
-------
Table 30
Rotary Precoat Vacuum Filtration - Shannopin Treatment Plant Sludge
(Preliminary Prices - Spring 1972)
Capital Costs
Equipment: Includes one 10
foot diameter x 17 foot face
vacuum filter with all motors,
vacuum pump with motor, vacuum
receivers, filtrate pump with
motor, precoat mix tank with
motor and precoat slurry pump $59,100.00
Construction and Installation:
35 percent of equipment 20.700.00
Total Equipment Cost $79,800.00
Equipment Depreciation:
10 years expected life
no salvage value
Building: 600 sq. ft. at
$10.00/sq. ft. 6,000.00
Building Depreciation:
30 years expected life
no salvage value
Total Capital Cost $85,800.00
Operational Costs
Maintenance: 6 percent of
total capital cost
Electricity: 2,250 KWH/day
at $0.0175/KWH
Labor: 24 hours at $6.00/hour
Precoat: Johns-Manville Hyflo
Super-Cel, $68.00/ton F.O.B.
California warehouse, $100.40/ton
delivered Morgantown, W.Va.
$7,980.00/year
$21.90/day
$200.00/year
0.50/day
$5,150.00/year $14.10/day
39.40/day
$144.00/day
$230.50/day
128
-------
Table 30 (Continued)
Total Capital and Operational Cost $450.40/day
Assuming 180,000 gallons $2.50/1,000
clarifier underflow per day gallons
sludge de-
watered
Assuming 250,000 gallons acid $1.80/1,000
water per day gallons acid
water
129
-------
Table 31
Rotary Precoat Vacuum Filtration - Banning Treatment Plant Sludge
(Preliminary Prices - Spring 1972)
Capital Costs
Equipment: Includes one 10
foot diameter x 17 foot face
vacuum filter with all motors,
vacuum pump with motor, vacuum
receivers, filtrate pump with
motor, precoat mix tank with
motor and precoat slurry pump $59,140.00
Construction and Installation:
35 percent of equipment 20,700.00
Total'Equipment Cost $79,800.00
Equipment Depreciation:
10 years expected life
no salvage value
Building: 600 sq. ft. at
$10.00/sq* ft. 6,000.00
Building Depreciation:
30 years expected life
no salvage value
Total Capital Cost $85,800.00
Operational Costs
Maintenance: 6 percent of
total capital cost
Electricity: 2,250 KWH/day
at $0.0175/KWH
Lahor: 24 hours at $6.00/hour
Precoat: Johns-Manville Celite
501, $73.00/ton F.O.B.
California warehouse, $105.40/ton
delivered Morgantown, W.Va.
$7,980.00/year
$21.90/day
$200.00/year
0.50/day
$5,150.00/year $14.10/day
39.40/day
$144.00/day
$301.50/day
130
-------
Table 31 (Continued)
Total Capital and Operational Cost $521.40/day
Assuming 360,000 gallons $1.40/1,000
clarifier underflow per day gallons
sludge de-
watered
Assuming 720,000 gallons acid $0.75/1,000
water per day acid water
131
-------
Table 32
Rotary Precoat Filtration - Edgell Treatment Plant Sludge
(Preliminary Prices - Spring 1972)
Capital Costs
Equipment: Includes one 10
foot diameter x 14 foot face
vacuum filter with all motors,
vacuum pump with motor, vacuum
receivers, filtrate pump with
motor, precoat mix tank with
motor and precoat slurry pump $53,000.00
Construction and Installation:
35 percent of equipment __ 18,600.00
Total Equipment Cost $71,600.00
Equipment Depreciation:
10 years expected life
no salvage value
Building: 500 sq. ft. at
$10.00/sq. ft. 5,000.00
Building Depreciation:
30 years expected life
no salvage value
Total Capital Cost $76,600.00
Opera tional Cos ts
Maintenance: 6 percent of
total capital cost
Electricity: 1,880 KWH/day
at $0.0175/KWH
Labor: 24 hours at $6.00/hour
Precoat: Johns-Manville Celite
501, $73.00/ton F.O.B.
California warehouse, $105.40/ton
delivered Morgantown, W.Va.
$7,160.00/year
$19.60/day
$166.00/year
0.50/day
$4,600.00/year $12.60/day
32.90/day
$144.00/day
$141.80/day
132
-------
Table 32 (Continued)
Total Capital and Operational Cost $351.40/day
Assuming 100,000 gallons $3.50/1,000
clarifier underflow per day gallons
sludge de-
watered
Assuming 1,000,000 gallons acid $0.35/1,000
water per day gallons acid
water
133
-------
Table 33
Pressure Filtration - Shannopin Treatment Plant Sludge
(Preliminary Prices - Spring 1972)
Capital Costs
4-48 inch filter presses
at $20,000.00 $80,000.00
4-plate shifters at
$2,400.00 each 9,600.00
Feed pump with accessories 900.00
Precoat equipment at
$5,000.00 each 20,000.00
Construction and Installation:
35 percent of equipment
Total Equipment Cost
Equipment Depreciation:
10 years expected life
no salvage value
Building: 3,200 sq. ft. at
$10.00/sq. ft. 32,000.00
Building Depreciation:
30 years expected life
no salvage value
38.700.00
$149,200.00
Total Capital Cost
Operational Costs
Maintenance: 6 percent of
total capital cost
Electricity: 270 KWH/day
at $0.0175/KWH
Labor: 24 hours, 2 men at
$6.00/hour each
Precoat: Johns-Manville Celite
501, $73.00/ton F.O.B.
California warehouse, $105.40/ton
delivered Morgantown, W.Va.
$181,200.00
$14,920.00/year
$40.90/day
1,066.00/year
2.90/day
$10,874.00/year
$29.80/day
4.70/day
$288.00/day
$240.00/day
134
-------
Table 33 (Continued)
Total Capital and Operational Cost $606.30/day
Assuming 180,000 gallons $3.40/1,000
clarifier underflow per day gallons
sludge de-
watered
Assuming 250,000 gallons acid $2.40/1,000
water per day gallons acid
water
135
-------
Table 34
Pressure Filtration - Banning Treatment Plant Sludge
(Preliminary Prices - Spring 1972)
Capital Costs
3-48 inch filter presses
at $23,000.00 each
3-plate shifters at
$2,300.00 each
Feed pump with accessories
Precoat equipment at
$5,000.00 each
Construction and Installation:
35 percent of equipment
Total Equipment Cost
Equipment Depreciation:
10 years expected life
no salvage value
Building: 2,100 sq. ft. at
$10.00/sq. ft.
Building Depreciation:
30 years expected life
no salvage value
Total Capital Cost
Operational Costs
Maintenance: 6 percent of
total capital cost
Electricity: 270 KWH/day
$0.0175/KWH
Labor: 24 hours, 2 men at
$6.00/hour each
Precoat: Johns-Manvilie Celite
501, $73.00/ton F.O.B.
California warehouse, $105.50/ton
delivered Morgantown, W.Va.
$69,000.00
6,900.00
900.00
15,000.00
32,100.00
$123,900.00
21,000.00
$144,900.00
$12,390.00/year
$33.90/day
$700.00/year
1.90/day
$8,694.00/year
$23,
4,
80/day
70/day
$288.00/day
$247.00/day
136
-------
Table 34 (Continued)
Total Capital and Operational Cost $599.30/day
Assuming 360,000 gallons $1.70/1,000
clarifier underflow per day gallons
sludge de-
watered
Assuming 720,000 gallons acid $0.80/1,000
water per day gallons acid
water
137
-------
Table 35
Pressure Filtration - Norton Treatment Plant Sludge
(Preliminary Prices - Spring 1972)
Capital Costs
1-48 inch filter press $21,000.00
1-plate shifter 2,700.00
Feed pump with accessories 900.00
Precoat equipment 5,000.00
Construction and Installation:
35 percent of equipment 10,400.00
Total Equipment Cost $40,000.00
Equipment Depreciation:
10 years expected life
no salvage value
Building: 1,200 sq. ft. at
$10.00/sq. ft. 12,000.00
Building Depreciation:
30 years expected life
no salvage value
Total Capital Cost $52,000.00
Operational Costs
Maintenance: 6 percent of
total capital cost
Electricity: 270 KWH/day
at $0.0175 KWH
Labor: 24 hours, 2 men at
$6.00/hour each
Precoat: Johns-Manville Celite
501, $73.00/ton F.O.B.
California warehouse, $105.40/ton
delivered Morgantown, W.Va.
$4,000.00/year
$11.00/day
$400.00/year
1.00/day
$3,120.00/year
8.50/day
4.70/day
$288.00/day
50.00/day
138
-------
Table 35 (Continued)
Total Capital and Operational Cost $363.20/day
Assuming 50,000 gallons $7.30/1,000
clarifier underflow per day gallons
sludge de-
watered
Assuming 20,000,000 gallons acid $0.02/1,000
water per day gallons acid
water
139
-------
Table 36
Pressure Filtration - Edgell Treatment Plant Sludge
(Preliminary Prices - Spring 1972)
Capital Costs
3-48 inch filter presses
at $22,500.00 each
3-plate shifters at
$2,200.00 each
Feed pump with accessories
Precoat equipment at
$5,000.00 each
Construction and Installation:
35 percent of equipment
Total Equipment Cost
Equipment Depreciation:
10 years expected life
no salvage value
Building: 1,800 sq. ft. at
$10.00/sq. ft.
Building Depreciation:
30 years expected life
no salvage value
Total Capital Cost
Operational Costs
Maintenance: 6 percent of
total capital cost
Electricity: 270 KWH/day
at $0.0175/KWH
Labor: 24 hours, 2 men at
$6.00/hour each
Precoat: Johns-Manville Celite
501, $73.00/ton F.O.B.
California warehouse, $105.40/ton
delivered Morgantown, W.Va.
$67,500.00
6,600.00
900.00
15,000.00
31,500.00
$121,500.00
18,000.00
$139,500.00
$12,150.00/year
$33.30/day
$600.00/year
1.60/day
$8,370.00/year
$22
4
$288
,90/day
,70/day
,00/day
$253.00/day
140
-------
Table 36 (Continued)
Total Capital and Operational Cost $603.50/day
Assuming 100,000 gallons $6.00/1,000
clarifier underflow per day gallons
sludge de-
watered
Assuming 1,000,000 gallons acid $0.60/1,000
water per day gallons acid
water
141
-------
Table 37
Thermal Spray Drying - Shannopin Treatment Plant Sludge
(Preliminary Prices - Spring 1972)
Capital Costs
1-36 foot spray drying
system
$500,000.00
$181,300.00
$706,300.00
$714,800.00
Equipment Options:
Feed Pump 7,000.00
Access Steel 18,000.00
Construction and Installation:
35 percent of equipment
Total Equipment Cost
Equipment Depreciation:
10 years expected life
no salvage value
Penthouse (Building) $8,500.00
Building Depreciation:
30 years expected life
no salvage value
Total Capital Cost
Operational Costs
Maintenance: 6 percent of
total capital cost
Fuel: #2 fuel oil, 16,900
gallons/day at $0.13/gallon
Electricity: 7,600 KWH/day
at $0.0175/KWH
Labor: 24 hours at $6.00/hour
Total Capital and Operational Cost
Assuming 180,000 gallons
clarifier underflow per day
142
$70,630.00/year
$193.50/day
$23.00/year
$0.10/day
$42,888.00/year
$117.50/day
$2,197.00/day
$133.00/day
$144.00/day
$2,785.10/day
$15.50/1,000
gallons
sludge de-
watered
-------
Table 37 (Continued)
Assuming 250,000 gallons acid $11,10/1,000
water per day gallons acid
water
143
-------
Table 38
Thermal Spray Drying - Banning Treatment Plant Sludge
(Preliminary Prices - Spring 1972)
Capital Costs
2-36 foot spray drying
systems at $500,000.00 each $1,000,000.00
Equipment Options:
Feed Pump
Access Steel
Construction and Installation:
35 percent of equipment
Total Equipment Cost
Equipment Depreciation:
10 years expected life
no salvage value
Penthouse (Building)
Building Depreciation:
30 years expected life
no salvage value
Total Capital Cost
Operational Costs
Maintenance: 6 percent of
total capital cost
Fuel: #2 fuel oil, 34,300
gallons/day at $0.13/gallon
Electricity: 15,200 KWH/day
at $0.0175/KWH
Labor: 24 hours at $6.00/hour
Total Capital and Operational Cost
Assuming 360,000 gallons
clarifier underflow per day
14,000.00
36,000.00
$367,500.00
$1,417,500.00
$141,750.00/year
$17,000.00
$388.40/day
$567.00/year
$1.60/day
$1,434,500.00
$86,070.00/year
144
$250.80/day
$4,459.00/day
$152.00/day
$144.00/day
$5,395.80/day
$15.00/1,000
gallons
sludge de-
watered
-------
Table 38 (Continued)
Assuming 720,000 gallons acid <7 cn/1 nnn
water per day ?7.50/1,000
gallons acid
water
145
-------
Table 39
Thermal Spray Drying - Norton Treatment Plant Sludge
(Preliminary Prices - Spring 1972)
Capital Costs
1-30 foot spray drying
system
$300,000.00
$111,100.00
$428,600.00
$436,600.00
Equipment Options:
Feed Pump 3,500.00
Access Steel 14,000.00
Construction and Installation:
35 percent of equipment
Total Equipment Cost
Equipment Depreciation:
10 years expected life
no salvage value
Penthouse (Building) $8,000.00
Building Depreciation:
30 years expected life
no salvage value
Total Capital Cost
Operational Costs
Maintenance: 6 percent of
total capital cost
Fuel: #2 fuel oil, 4,300
gallons/day at $0.13/gallon
Electricity: 6,200 KWH/day
at $0.0175/KWH
Labor: 24 hours at $6.00/hour
Total Capital and Operational Cost
Assuming 50,000 gallons
clarifier underflow per day
146
$42,860.00/year
$117.40/day
$267.00/year
$0.70/day
$26,196.00/year
$71.80/day
$559.00/day
62.00/day
$144.00/day
$954.90
$19.00/1,000
gallons
sludge de-
watered
-------
Table 39 (Continued)
Assuming 20,000,000 gallons acid , $0.05/1,000
water per day gallons acid
water
147
-------
Table 40
Thermal Spray Drying - Edgell Treatment Plant Sludge
(Preliminary Prices - Spring 1972)
Capital Costs
1-34 foot spray drying
system
$400,000.00
$147.300.00
$568,300.00
$576,800.00
Equipment Options:
Feed Pump 5,000.00
Access Steel 16,000.00
Construction and Installation:
35 percent of equipment
Total Equipment Cost
Equipment Depreciation:
10 years expected life
no salvage value
Penthouse (Building) $8,500.00
Building Depreciation:
30 years expected life
no salvage value
Total Capital Cost
Operational Costs
Maintenance: 6 percent of
total capital cost
Fuel: #2 fuel oil, 9,300
gallons/day at $0.13/gallon
Electricity: 7,200 KWH/day
at $0.0175/KWH
Labor: 24 hours at $6.00/hour
Total Capital and Operational Cost
Assuming 100,000 gallons
clarifier underflow per day
148
$56,830.00/year
$155.70/day
$283.00/year
$0.80/day
$34,608.00/year
$94.80/day
$l,209.00/day
126.00/day
144.00/day
$l,730.30/day
$17.30/1,000
gallons
sludge de-
watered
-------
Table 40 (Continued)
Assuming 1,000,000 gallons acid $1.73/1,000
water per day gallons acid
water
149
-------
Table 41
Centrifugation - Shannopin Treatment Plant Sludge
(Preliminary Prices - Spring 1972)
Capital Costs
5-Sharples Sludge Pak
SP-6500 centrifuge,
$55,000.00 each $275,000.00
Construction and Installation:
35 percent of equipment 96.300.00
Total Equipment Cost $371,300.00
Equipment Depreciation: $37,200.00/year
10 years expected life $101.91/day
no salvage value
Building: 1,000 sq. ft. at
$10.00/sq. ft. $10,000.00
Building Depreciation: $33.00/year
30 years expected life $0.90/day
no salvage value
Total Capital Cost $381,300.00
Operational Costs
Maintenance: 6 percent of $22,878.00/year
total capital cost $62.70/day
Electricity: 720 KWH/day
at $0.0175/KWH 12.60/day
Labor: 24 hours at $6.00/hour $144.00/day
Total Capital and Operational Cost $322.10/day
Assuming 180,000 gallons $1.80/1,000
clarifier underflow per day gallons
sludge de-
watered
Assuming 250,000 gallons acid $1.30/1,000
water per day gallons acid
150 water
-------
Table 42
Centrifugation - Banning Treatment Plant Sludge
(Preliminary Prices - Spring 1972)
Capital Costs
10-Sharples Sludge Pak
SP-6500 centrifuge,
$55,000.00 each $550,000.00
Construction and Installation:
35 percent of equipment 192,500.00
Total Equipment Cost $742,500.00
Equipment Depreciation: $74,250.00/year
10 years expected life $203.40/day
no salvage value
Building: 2,000 sq. ft. at
$10.00/sq. ft. $20,000.00
Building Depreciation: $667.00/year
30 years expected life $1.80/day
no salvage value \
Total Capital Cost $762,500.00
Operational Costs
Maintenance: 6 percent of $45,750.00/year
total capital cost $125.50/day
Electricity: 720 KWH/day
at $0.0175 KWH 12.60/day
Labor: 24 hours at $6.00/hour $l44.00/day
Total Capital and Operational Cost $487.10/day
Assuming 360,000 gallons $1.40/1,000
clarifier underflow per day gallons
sludge de-
watered
Assuming 720,000 gallons acid $0.70/1,000
water per day gallons acid
water
151
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Table 43
Centrifugation - Norton Treatment Plant Sludge
(Preliminary Prices - Spring 1972)
$110,000.00
38,500.00
$148,500.00
Capital Costs
2-Sharpies Sludge Pak
SP-6500 centrifuge,
$55,000.00 each
Construction and Installation:
35 percent of equipment
Total Equipment Cost
Equipment Depreciation:
10 years expected life
no salvage value
Building: 400 sq. ft. at
$10.00/sq. ft $4,000.00
Building Depreciation:
30 years expected life
no salvage value
Total Capital CCost
Operational Costs
Maintenance: 6 percent of
total capital cost
Electricity: 720 KWH/day
at $0.0175/KWH
Labor: 24 hours at $6.00/hr
Total Capital and Operational Cost
Assuming 50,000 gallons
clarifier underflow per day
Assuming 20,000,000 gallons acid
water per day
$14,850.00/year
$40.70/day
$133.00/year
$0.40/day
$152,500.00
$9,150.00/year
$25.00/day
12.60/day
$144.00/day
$222.70/day
$4.50/1,000
gallons
sludge de-
watered
$0.01/1,000
gallons acid
water
152
«U,S. GOVERNMENT PRINTING OFFICE: 1973 514-513/208 1-3
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SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
1. Report No.
2.
4. Title
Devatering of Mine Drainage Sludge - Phase II
7. Aathor(s)
David J. Akers, Jr., "• Edward A. Moss
9. Organization
Wost Virginia University
Morgantown, W. Va.
3. Accession No.
W
5. Report Date
6.
8. Performing Organization
Report No.
10. Project No.
•RPA -
12. Sponsoring Organization
15. Supplementary Notes
11. Contract/Grant No.
Grant 14010 FJX
13. Type of Report and
'' Period Covered
Environmental Protection Agency report
number, EPA-R2-73-169, February 1973.
u. Abstract A study of various acid mine drainage sludge conditioning methods and de-
watering systems was made. Acid mine drainage & sludge from neutralization plants were
iharacterized. Four sludges were selected as being representative of the various types
of sludges produced by the lime/limestone neutralization of acid mine drainage.
The conditioning methods studied were: freezing, use of flocculants, and use of
filter aids. The six dewatering systems evaluated were: 1, conventional, rotary
vacuum filtration, 2. rotary precoat vacuum filtration, 3. pressure filtration, U.
porous bed filtration, 5. thermal spray drying, and 6. centrifugation.
Ho single dewatering system was found best for all acid mine drainage sludges. On
the basis of cost, the most promising acid mine drainage sludge dewatering techniques
appear to be centrifugation, rotary vacuum filtration and rotary precoat vacuum filtra-
tion.
17a. Descriptors . , , . . , . „ , .
Acid Mine Drainage* neutralization* sludge* freezxng, flocculation, cenorifugation
17b. Identifiers
filter aid* vacuum filtration* pressure filtration*
17c. COWRR Field & Group 05D
18. Availability
19. Security Class.
(Report)
20. Security Class.
(Page)
21. No. of
Pages
22. Price
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
US DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C. 20240
Abstractor Ronald D. Hill
WRSIC 102 (REV. JUNE 1971)
| institution Environmental Protection Agency
SPO 913.261
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