EPA/540/2-89/037
SUPERFUNDTREATABILITY
CLEARINGHOUSE
Document Reference:
VeriTec Corp. Case Study, Hazardous Waste Management Utilizing Lime. Paper
presented at the Annual Meeting of the National Lime Association, Phoenix, Arizona.
13pp. AprM9,1987.
EPA LIBRARY NUMBER:
Superfund Treatabllity Clearinghouse - FAAP
U.S. Environmental Protection Agency
Region 5, Library (PL-I0'}
77 West Jackson Bci,:!"/:.•;/ '•' ~~oi
Chicago, IL 60604-35,0
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SUPERFUND TREATABILITY CLEARINGHOUSE ABSTRACT
Treatment Process:
Media:
Document Reference:
Document Type:
Contact:
Site Name:
Location of Test:
Immobilization - Flyash Solidification
Sludge/Metal Finishing
VeriTec Corp. Case Study, Hazardous Waste
Management Utilizing Lime. Paper presented at the
Annual Meeting of the National Lime Association,
Phoenix, Arizona. 13 pp. April 9, 1987.
Conference Paper
Andre DuPont
National Lime Association
3601 North Fairfax Drive
Arlington, VA 22201
703-243-LIME
VeriTec Corp. (Non-NPL)
Knoxville, TN
BACKGROUND; This report presents the results of treating a plating sludge
having high levels of Cu, Ni and Cr with a lime fly ash additive. The
pozzolonic reaction solidified the sludge. The results of various leaching
tests are presented and discussed. An economic analysis suggests that the
mixture used was more cost effective than other types of solidifying agents
and processes. Various additive sludge ratios are recommended and a con-
ceptual system design along with costs is presented.
OPERATIONAL INFORMATION; The sludge that was investigated was a Cu-Ni-Cr
hydroxide sludge from alkaline pH precipitation of a plating-rinse waste-
water. The untreated sludge contains 35 g/kg of Cu, 65g/kg Ni and 72 g/kg
of Cr. Sludge density is 1.133 g/cc. Lab tests revealed that solidifica-
tion was feasible and that the solidified samples displayed considerable
unconfined compressive strength. The structural strength was reported to
be between 100-125 psi. Lab tests were followed with field tests to deter-
mine the effect of leaching on the solid samples. At 21 days treated
samples were subject to the EPA-RCRA EP toxicity procedures, deionized
water leaching procedures, and the Multiple Extraction Procedure (MEP)
leaching test. Detailed explanation of the leaching procedures are given
along with methods of analysis used to determine heavy metal concentra-
tions. No QA/QC information is contained in the report.
PERFORMANCE: Laboratory simulation studies revealed that the fixation
process could reduce the EP toxicity. EP toxicity tests for Cr, Ni and Cu
with initial concentrations of 73.0, 65.6 and 22.0 mg/1, respectively, were
reduced by treatment to 2.9, 1.0 and 1.0 mg/1, respectively. Field tests
reveal that levels of Ni, Cr and Cu can all be reduced by the fixation
process. The following tables show results from the various leaching
tests. Cyanide (CN) is not used in the plant, however, CN was found at
0.13 and 0.05 ppm in the raw sludge leachate samples. CN was <0.01 in all
treated sludge samples showing this fixation process also retards low level
3/89-30 Document Number: FAAP
NOTE: Quality assurance of data nay not be appropriate for all uses.
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leaching of cyanides. Total chromium was reduced from 22 to .02 - .05 ppm
in one set of samples and from 3.5 ppm to 0.4 - 0.1 ppm in another set of
samples. Nickel was reduced from 87 to 0.01 ppm with treatment. The
authors state that they believe the wastes no longer violate hazardous
waste criteria and recommend that the treated wastes be delisted.
An economic analysis of the costs associated with fixing one ton of
sludge using a 1:1 mass ratio of fixing agent and sludge was conducted.
Pozzolonic process is the cheapest of those evaluated. Cement costs $70
per ton whereas pozzolonic costs as low as $12.50 per ton depending on the
type of fly ash used (bulk or bagged). Total disposal costs increase as
the mass ratio of fixing agent to dry weight sludge increases. The authors
provide a conceptual design of a process along with estimated costs to
construct a one ton per day system. Total system capital/construction
costs are estimated to be $65,000.
CONTAMINANTS;
Analytical data is provided in the treatability study report. The
breakdown of the contaminants by treatability group is:
Treatability Group CAS Number Contaminants
WlO-Nonvolatile Metals 7440-47-3 Chromium
7440-02-0 Nickel
Wll-Volatile Metals 7440-43-9 Cadmium
W12-0ther Inorganics 57-12-5 Cyanide
TABLE 1
LEACHING STUDIES OF RAW AND LFA FIXATED (2:1) CYLINDERS
Untreated Treated Untreated Treated
EPA - RCRA EPA - RCRA D.I. H20 D.I. H20
Cr 73.0* 2.9 0.63 <0.01
Ni 65.6 1.0 0.61 0.04
Cu 22.0 1.0 0.24 0.07
3/89-30 Document Number: FAAP
NOTE: Quality assurance of data may not be appropriate for all uses.
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TABLE 2
EPA-RCRA LEACH TESTING OF LFA TREATED AND UNTREATED SLUDGES
Metals
Untreated
Treated
Arsenic
Barium
Cadmium
Chromium
Lead
Mercury
Selenium
Nickel
Copper
<0.001*
0.23
<0.001
7.4
<0.01
<0.001
<0.001
3.9
2.4
<0.001
0.09
<0.001
0.81
<0.01
<0.001
0.002
4.8
0.02
TABLE 3
PLATING SLUDGE LEACHATE LEVELS
(mg/liter)
CNJ
Cd
Ni
*A11 value* in Bg/1 of leachate.
CN - Cyanide
Cr
Raw Unreacted
Fixated #1
Fixated #2
Raw Unreacted
Fixated #3
Fixated #4
0.13
<0.01
<0.01
<0.01
<0.01
0.05
<0.01
<0.01
<0.01
<0.01
0.001
0.004
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
87.0
<0.01
<0.01
<0.01
<0.01
76.0
0.15
<0.01
<0.01
<0.01
22.0
0.03
0.02
0.05
0.05
3.5
0.10
0.04
0.07
0.07
Note: This is a partial listing of data.
information.
Refer to the document for more
3/89-30 Document Number: FAAP
NOTE: Quality assurance of data «ay not be appropriate for all uses.
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-lfr- f")
CASE STUDY
HAZARDOUS WASTE MANAGEMENT UTILIZING LIME
National Lime Association
April 9, 1987
Annual Meeting
Phoenix, Arizona
Dennis W. Weeter, Ph.D., P.E.
Larry W. Jones, Ph.D.
VeriTec Corporation
P.O. Box 8791
Knoxville, TN 37996
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EXECUTIVE SUMMARY
A plating sludge with high levels of Cu, Ni, and Cr was
treated with a lime-fly ash. additive. A pozzolonic reaction
between the additive and the plating sludge brought about a 21-day
structural strength of 100-125 psi. The solidified product was
tested with EPA-RCRA, extractant procedure (EP) toxicity test;
deionized water leaching; and the multiple extractant procedure
(MEP). Chromium levels were significantly below RCRA standards;
copper and nickel leachates levels were reduced by solidification.
Based upon these results the waste was delisted by EPA.
Economic analysis indicates that the lime and fly ash
admixture is more cost effective than other .agents studied
(Portland cement, lime, or sodium silicate). The lime-fly ash
admixture is recommended as the treatment reagent of choice at a
3:1 or 4:1 reagent to sludge ratio (W/V). A system process, a
recommended design, and a bid scenario are presented in this
report. Projected capital costs and construction costs are about
$50,000 and total project costs are estimated to be $65,000.
BACKGROUND
This company generates a Cu-Ni-Cr hydroxide sludge from
alkaline pH precipitation of a plating-rinse, wastewater. These
metals are plated on plastic predominantly for automobile parts and
consumer products. Table 1 presents data on the existing sludge
mass and its characteristics.
The sludge is thickened by sedimentation to about 1% solids by
weight and then pumped to a 1500 gallon holding tank where it
further thickens to 2-3% solids by weight. The sludge is then
pumped through a Shriver filter press and thickened to 28% solids
by weight. The 28% solids sludge is the topic of the study. The
filter press filtrate is recycled to the start of the treatment
works.
Table 1. Raw Sludge Composition
Moisture Content
Cr
Cu
Ni
Mass Produced
Mass Produced
72%
72 g/Kg - wet weight basis
35 g/Kg - wet weight basis
65 g/Kg - wet weight basis
10 cu. yd/month
23 cu. yd/month
(at maximum plating capacity)
Sludge Density
1900 Ib/cu. yd or 1.133 g/cc
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RESULTS AND DISCUSSION
These studies were broken into five phases: 1. lab-scale
tests were conducted with several agents to see if stabilization/
solidification was a possible alternative; 2. a field-level test
was run with the most economic stabilization reagent; 3. a series
cf lab simulations were conducted in order to evaluate optimal
nxes of the chosen agent and to evaluate leaching potential and
hazardous characteristics; 4. multiple field level, in plant
tests, were conducted to evaluate process variability; and 5. the
resultant sludges were evaluated by the multiple extraction
procedure (MEP).
Lab-scale Tests: Samples of filtered sludge were collected,
and grated by hand so it would pass through a 40 mesh sieve. Then
predetermined amounts (percent by weight) of several stabilization
reagents were blended with the grated waste. The final mixtures
were then compacted by the Modified Proctor Test in several 3 inch
long by 1 inch diameter molds. When the samples were removed from
the molds, one duplicate was wrapped in cellophane while the others
were left to air dry. Stabilization reagents tested were Portland
cement, sodium silicate, Calcilox (Dravo trademark), lime, and lime
plus fly ash (LFA). Samples were tested for 7 and 14 days
unconfined compressive strength (UCS).
»
The unwrapped, air dried, cylinders retained zero UCS. For
optimum strength, moisture must be available for the slow LFA
pozzolonic reactions. The percent of moisture is a critical factor
in strength development.
The wrapped cylinders demonstrated appreciable UCS gain. In a
comparison of cylinders prepared with different reagents at the
weight-ratio of 1:1 (stabilization reagent to dry weight of the
sludge), cement showed UCS values of greater than 200 psi; Calcilcx
ash UCS values near 100, and LFA was between 50-100 psi. Neither
lime nor sodium silicate by themselves showed strength gain in
these tests. Sodium silicate in combination with other agents
(LFA, cement, calcilox) did not add nor reduce UCS. Calcilox
blended with LFA increased (3-5 times) the strength developed by
LFA alone.
Following these studies, an economic evaluation was conducted
to determine the best stabilization reagent. LFA can either be
prepared by blending CaO and fly ash, or by purchasing a baghouse
waste product produced at most chemical-lime kiln operations. This
material is generally about 40% CaO, 40% fly ash, and 20% CaC03.
Calcilox is also a large volume, prepared waste material. It
was decided to conduct further tests using LFA alone and LFA with
small amounts of Calcilox.
FIELD TESTS
Several barrels of LFA were shipped to the plant for testing,
An air compressor line was placed in the bottom of a 1500 gallon
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sludge storage tank, which was used as a mixing tank.
A 45:55 mixture of LFA to plating sludge (dry weight) was
produced by adding approximately 250 pounds LFA to the tank. The
mixture was pumped through the filter press and dewatered. The
sludge press, which dewatered raw plating sludge to about 20%
solids by weight, produced a mixture of LFA and sludge which was
about 40% solids by weight. Due to improved dewaterability, no
volume gain was seen in the 1:1 LFA-sludge formulations. However,
a higher dewatered density (about 1.23 g/cc) resulted since the LFA
(90 Ib/cu. ft.) displaced some of the water (62.4 Ib/cu. ft.).
During the filter run, the composite, liquid filtrate was
sampled and analyzed for heavy metals (Table 2). The filtrate was
returned to the wastewater treatment system where it is diluted to
about 1 to 60 based upon raw wastewater flows. The effect of the
LFA addition on filtrate water quality is negligible.
Table 2. LFA-Sludge Liquid Filtrate Analysis
(all values in mg/1, except pH)
Arsenic
Barium
Cadmium
Chromium
Copper
< 0.003
0.09
< 0.001
0.79
1.12
Lead
Nickel
Selenium
Silver
PH
0.13 *
0.47
0.015
< 0.002
11.0
Samples of raw sludge and LFA-treated sludge were taken to the
laboratory where duplicate samples were wrapped or left to air dry.
The air dried samples again failed to develop appreciable
structural strength. Wrapped LFA-sludge samples were tested for
UCS at day 3 (20 psi), day 5 (25 psi), day 7 (40 psi) and day 12
(50 psi).
At day 21 treated and untreated, wrapped samples were
subjected to leaching tests for 24 hours using the EPA-RCRA
acetic-acid leaching procedures. Table 3 presents the results from
this study. First, the raw sludge would probably violate toxicity
standards since the Cr concentration is greater than 5.0 (100 times
the drinking water standard). Leachates from the treated samples
had a Cr value of 0.81 mg/1. It should be emphasized that no
dilution effects (less total sludge in treated samples) have
occurred since each sample had the same percentage (20%) of plating
sludge. The treated sample had an extra 20% of LFA but less
liquid. It is also important that the treated sample did not
contribute excessive concentrations of fly-ash-related metals.
Metals normally associated with fly ash include selenium, barium
, and selenium Csee Electric Power Research Institute, Coal Ash
Disposal Manual (1979)]. LFA does not reduce the Cr concentration
in exchange for other heavy metal problems.
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Table 3. EPA-RCRA Leach Testing of .LFA Treated and Untreated
Sludges
Metals Untreated Treated
Arsenic
Barium
Cadmium
Chromium
Lead
Mercury
Selenium
Nickel
Copper
< 0.001*
0.23
< 0.001
7.4
< 0.01
< 0.001
< 0.001
3.9
2.4
< 0.001
0.09
< 0.001
0.81
< 0.01
< 0.001
0.002
4.8
0.02
* All values in mg/1 of leachate.
LABORATORY SIMULATION
>
A laboratory procedure was developed to simulate the field
sludge press. Raw waste slurry (1-3%) was placed in a blender with
the dry stabilization reagent (LFA, Calcilox, or both). The
mxture was placed in a high pressure (up to 100 psi) Millipore
filter apparatus and dewatered using 0.45u filters. The resulting
cake was then hand molded into the shape of a modified Proctor
cylinder U"x3").
Studies were then conducted in which the ratio of
stabilization reagent to dry-weight sludge was increased in order
to improve structural strength and further reduce leachate
characteristics. A set of cylinders was produced with ratios of
2.0 to 10 (LFA to dry weight sludge). On day 14, cylinders were
leached for 24 hours using both the EPA-RCRA procedure and
deionized water. Untreated sludge was also leached by both
methods. To make the proper comparisons, care was given to make
sure that equal weights of dry sludge solids were leached in each
case. Table 4 presents the results. Again, the fixation process
reduced the EPA-RCRA toxicity to below the Cr standard of 4.0 mg/1.
Similar reductions occurred using D.I. H2O. Structural DCS was
determined at day 21 for the 2:1 samples: Stabilization, using
only LFA at 2:1 produced specimens with 120 psi, while a 3 to 1
rrixture of LFA and Calcilox gave specimens with 430 psi UCS.
In-Plant Field Tests; To obtain representative samples for
each of the four field tests, the stabilizing reagent was added to
the sludge holding tank prior to pumping the mixture to the filter
press. Mass ratios of stabilizing reagent to dry-weight of plating
sludge is presented in Table 5. After collection and dewatering of
the sludge in the press, sludge cake was collected from each cell
of the press. Then using a pocket knife, approximately twenty 1
inch square, 3 inch high rectangles were cut from the cake. Each
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square was wrapped in plastic, scaled, and transported to the
laboratory.
Table 4. Leaching Studies of Raw and LFA Fixated (2:1) Cylinders
Untreated
Cr
Hi
Cu
EPA
73
65
22
- RCRA
.0*
.6
.0
Treated
EPA - RCRA
2.9
1.0
1.0
'Jnt
D.I
0
0
0
reated
. H20
.63
.61
.24
Treated
D.I.
< 0
0
0
H20
.01
.04
.07
* All values in mg/1 of leachate.
All samples were cured for a period of time at room
te.r.perature and subsequently for several days at 105°F - 100 %
humidity. Each sample received an equivalent of 39-46 curing days.
Following curing, two of the twenty samples from each test were
randomly selected for extraction procedure (EP) testing, so .that
eight, 1 inch by 3 inch, rectangles were tested. Samples of
untreated sludge were also collected at 3 week intervals and were
submitted for EP testing.
Treated samples and raw waste samples were subjected to the E?
toxicity test. The treated rectangles did not crack or break
during the structural integrity procedure (SIP) so whole samples
were tested.
Random cured samples from each test were submitted to
ur.confined compressive strength (UCS) testing, giving UCS from 400
to 900 psi.
The extraction procedure was carried out following the Federal
Register, May 19, 1980, pp. 33127-28 using the manual pH adjustment
procedure. Table 5 indicates the amount of 0.5N acetic acid that
was used for each sample. Within 1 hour of extraction start up,
all samples stabilized to pH 5.0 t 0.2. Following 24 hour
extraction, water was added to bring each sample to 20 times the
original sample weight, and filtered by 0.45 micron filter paper at
a maximum pressure of 75 psi. Liquid leachate samples were
collected in new, soap and water washed, twice D.I. rinsed, plastic
bottles. Samples were placed in a cold room (40°F) and delivered
to the analytical laboratory two days later. No preservative was
added. All samples were analyzed for Cr (total), Cd, Ni, and CN as
described in EPA 600/4-79-020, March 1979 (Methods for Analyses of
Water and Wastes).
Table 5 presents the testing results of the raw and fixated
samples. As expected, cadmium values were extremely low on all
samples. Nickel was reduced from 87 and 76 ppm to 0.01 with
treatment. These values are well below proposed nickel standards.
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Tst'.e S. KASS Ratio* of Stabilisation Reagent to Dry-Weight of Plating Sludge
Mass Ratio
*-«T '* Fixating Agent
to Dry Wt.
CaJce1
X M
•lass of 0.5N
Sludge Acetic Acid
Leached Added CN
LeacKate Ar-ai'jsej
(ag/1)
Cd Ni Cr Cr*'
Rav-t'nr«Acted (Samples 1&2) 20
1 5/1 32
3.15/1
2.30/1
27
(Samples 3A4) 20
2.55/1 30
30
36.62 37 0.13 0.001 87.0 22.0
86.27 34 <0.01 0.004 <0.01 0.03
101.71 24 <0.01 <0.001 <0.01 0.02
98.14 16 <0.01 <0.001 <0.01 0.05
86.98 18 <0.01 <0.001 <0.01 0.05
33.92 37 0.05 <0.001 76.0 J.5
82.05 30 <0.01 C0.001 0.15 0.10
97.78 40 <0.01 <0.001 <0.01 0.0^.
94.37 .,2 <0.01 <0.001 CO.01 0.07
92.46 31 <0.01 <0.001 <0.01 0.07
NA'
NA
NA
NA
HA
HA
NA
NA
HA
HA
1. Staples reooved from press before press was cocpletely fill. Therefore, cajce thickness was less than
2. Cr*6 not a/ialyzed on leachate saoples since it <-as found to consistently be <0.01 in p'ant waste
flows.
Cyanide (CN) is not used at the plant. However, CN was found
at 0.13 and 0.05 ppm in the raw sludge leachate samples. Recent
priority pollutant scans on the waste effluent have shown CN to be
< 0.04 ppm. CN was < 0.01 on all treated sludge samples which
demonstrates that the process also retards leaching of low level
cyanides.
Total Cr was reduced by fixation from 22 ppm to between 0.02 •
0.05 ppm on one sludge sample, and from 3.5 ppm to 0.02 - 0.10 ppm
on the second. Cr+b was pot analyzed because from the period
January'- March 1981, Cr+& in the plant waste water has
consistently been less than 0.01 ppm. In that same period, the
final liquid effluent has ranged from 0.038 - 0.065 for total Cr.
Cr b was analyzed by the DPC spectrophotometric method (Standard
Methods #14). The treated sludge leachate levels of total Cr are
all less than 0.10 ppm. Even is all Cr was Cr 5 (which is highly
unlikely), the RCRA standard according to the October 30, 1980,
-------
Federal Register, would not be violated. Note that total Cr
leaching is minimized as the stabilization reagent mass ratio is
increased. Earlier studied raw sludges which leached total' Cr
ranging from 7.4 - 73 ppm leached less than 0.05 ppm after
treatment. For Ni, the earlier studies shewed raw sludge leaching
from 4-66 ppm, whereas treated samples were below 0.07 ppm.
These results confirm those found in this phase of the study.
Further, the leached, treated rectangles were still physically
intact and sound following the leaching. We believe that this
waste no longer violates hazardous waste criteria.
The Multiple Extraction Procedure (MEP): The MEP utilized in
this testing is described below. All samples were ground to less
than 150u. Results of the MEP and EP are shown in Table 6.
1. Grind sample to particle size capable of passing through 100
mesh screen (150u).
2. Run the EP Toxicity test on this sample (minimum sample size
100 grams) as described in Test Methods for Evaluating Solid
Waste (SW-846). '
3. Analyze the extract for the constituents of concern listed in
Appendix VII (40 CFR 261.32/.33) using the analytical methods
indicated in Test Methods for Evaluating Solid Waste (SW-846).
4. Prepare a synthetic acid rain extraction fluid by adding a
60/40 weight percent mixture of sulfuric acid and nitric acid
to distilled deionized water until the pH is 3.0 ± 0.2.
5. Next weight the solid phase of the waste sample remaining after
the Separation Procedure of the EP and place it in the
extractor with 20 times its weight of the synthetic acid rain
extraction fluid. Do not allow the material to dry before
weighing. Use the same extractor as used in the EP.
6. The pH should be recorded between 5 and 10 minutes after the
solid material and the synthetic acid rain are placed in the
extractor and agitation has been started.
7. Agitate the mixture for 24 hours. Maintain the temperature at
20-40«C (68-104°F) during this time. The pH should again be
recorded at the end of the 24 hour extraction period.
8. Separate the material in the extractor into its component
liquid and solid phases as described in the Separation
Procedure of the EP.
9. Analyze the extract for the constituents of concern listed in
Appendix VII, using the same analytical methods as used for
analyzing the EP extract.
10. Re-extract the solid material remaining after extraction with
the synthetic acid rain 8 additional times. Use the same
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procedure for these additional extractions and analyses as used
in the initial synthetic rain .extraction.
11. If after completing the 9th synthetic rain extraction the
concentration of any of the listed constituents of concern is
increasing over that found in the 7th and 8th extractions, the.-.
continue extracting with synthetic acid rain until the
concentration in the extract ceases to increase.
12. Report the initial and final pH of each extraction and the
concentrations of each listed constituent of concern in each
extract.
Table 6 summarizes the EP and MEP data. All nickel values
were less than 0,001 mg/1. Total Cr showed a maximum of 0.82 mg/1
Table 6. EP and Multiple (Acid Rain) Extraction (MEP) Data
Sludge Extraction
Sample Namber
1 KEP)
2
3
4
5
6
7
8
9
2 KEP)
2
3
4
5
6
7
8
9
3 KEP)
2
3
4
5
6
7
8
9
Nickel
(mg/1)
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
Total Cr
(mg/1)
0.12
0.58
0.82
0.77
0.59
0.52
0.35
0.29
0.26
2.3
2.5
2.1
1.85
1.55
1.22
0.94
0.67
0.50
0.57
0.74
0.76
1.29
1.32
1.28
1.12
0.86
0.77
Cr46
(mg/1)
•»
*
0.82
*
*
•
*
*
*
1.6
*
*
1.6
*
*
•
*
*
*
*
*
*
1.25
*
*
*
»
* not analyzed
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for sludge sample 1, 1.32 mg/1 for sample 2, and 2.5 mg/1 for
sample 3. Cr4° was analyzed for four samples and ranged from 7C%
to 100% of the total Cr. Total Cr and Cr b in the extracts arc all
•-ell below 5.0 mg/1.
For the MEP (acid rain) leaching, sample 1 peaked on total Cr
~r. extraction «3, sample 2 peaked at extraction «5, and sample 3
peaked at extraction II (i.e., the EP).
There appears to be higher total Cr values leached from sludge
samples 2 and 3 than for 1. Sample 1 was prepared at a 5:1 mass of
fixating agent to dry weight sludge ratio, while Sample 2 was at a
ratio of 3 to 1 and Sample 3 was at 2 to 1. Since a pozzolonic
reaction is believed to be occurring, a stronger product appears to
i>e produced at a higher reagent to sludge ratio. Also, Cr and Ni
probably participate in the silicate reactants so that more
stabilization reagent presents more reaction sites.
In summary, as in the earlier cases (regular EP testing and
crushing tests), these wastes do not appear to be hazardous when
compared to EPA regulations. It is recommended that the treated
waste be delisted.
ECONOMIC EVALUATION OF FIXATING AGENTS
An economics analysis using the various stabilization agents
was also conducted. For the analysis, a 1:1 ratio of fixating
agent to dry weight plating sludge is assumed. If a higher ratio
is used, the comparative analysis is still valid. The costs are
based on creating about one ton of treated waste per day (the
typical generation rate of wet sludge, about 400 pounds per day,
dry weight). Table 7 presents the results:
Table 7. Cost Comparison of Fixating Agents with a 1:1 Mass
Ratio
Additive Per Ton Cost Cost per wet ton
$400/wet ton
Cement
Sodium Silicate
Lime
Calcilox
Lime & Fly Ash (Bulk)
Lime & Fly Ash (Bagged)
$70.00
$250.00
S60.00
$50.00
$12.50
$25.00
$14.00
$50.00
$12.00
$10.00
$2.50
$5.00
Figure 1 presents the cost versus the ratio of the mixture of
LFA to dry weight sludge. The cost is the sum of the disposal
costs plus the chemical costs. It does not include amortization of
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Figure 1. Treatment & Dispose Costs Versus Mass, Ratio
- ~| = Total Disposal Cost
O O = Reagent Cost © $12.50/ton
O = Savings if Waste is Delisted
CO
CO
o
O
"o ^
o o
£ t^
CD CD
0 ^
c^ Q)
^ CL
f"\ -f-..£\-
CO v_^
O
CL
CO
O
100
80
60
40
20
n
i
Cost of Hazardous Waste Disposal ^ ™
' °o. ,•''
xo^
• ^
n
-^ °\ Q^^^
M' ^><^
- •* ^'-^^"u ^\
^P ^C )^ "'\
^t^-> Q ^ Cost of Non-Hazardous Waste Disposal ^--^
O-J ' 1 » -^ —i - - i. i » i "'.^
02 4 6 8 10 12 14 16 18 20 22
Mass Ratio - Reagent to Dry Weight Sludge
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new capital equipment or O&M costs. Also, these costs are in $ per
wet ton from the plant. The increase in density due to addition of
LFA has been factored into the disposal costs. Clearly, Figure 1
illustrates that up to about 20:1 mass ratio the sludge is
economical to fixate and handle as a ncnhazardous waste.
CONCLUSIONS
A low cost, high volume, pozzolonic lime-fly ash material was
blended with an hydroxide plating sludge. Structural strength of
over 100 psi was obtained and the hazardous characteristics of the
sludge were reduced to a nonhazardous nature. The material must be
cured under humid condition to retain moisture for the pozzolonic
reaction. The stabilization reagent was added to sludge dewatered
with a sludge filter press.
PROPOSED PROCESS
A modification of the present sludge handling system, as
indicated in Figure 2, is proposed. The LFA slurry tank receives
stored chemicals from the dry hopper on a batch basis and is
blended with the liquid sludge from the 1500 gallon tank. Then,
the sludge plus the LFA slurry is pumped through a dual suction
diaphragm pump (at 100 psi) to the sludge filter press. Dewatered
sludge is emptied from the press into a thick plastic bag and then
placed in a plastic lined container. This provides a double lining
to keep the sludge moist for the pozzolonic reaction. Each
container is coded, dated, and placed in storage. No waste will be
shipped to the landfill until it has cured a minimum of 14 days.
Permanent records of the date a container was filled and when it
was shipped will be maintained. SHould the slurry tank not be
emptied on the batch run it should be drained to the raw waste
input line and diluted. Records should also be kept on LFA
purchases and utilization rates.
EQUIPMENT NEEDS AND COSTS
Referring to Figure 2, the following capital items will need
to be purchased to complete the project. Approximate costs are
given:
ESTIMATED CAPITAL COSTS
Dry Hopper & Feed $5,000
Slurry Tank & Mixer 5,000
Dual Chamber Pump 3,000
Valves, Piping 3,000
Controls 4,000
Total $20,000
10
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1500
Gallon
ss=l-3%
Filtrate
Press
Sludge
Figure 2. Proposed Stabilization Process Schematic
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TOTAL ESTIMATED PROJECT COSTS
Capital • $20,000
Construction 20,000
Engineering i
Contingencies 10,000
Legal &
Administrative
Financing
Total $65,000
A need for additional manpower to handle this process is not
anticipated. Operation costs will include the chemical costs plus
energy to mix the slurry tank.
RECOMMENDED PROCESS DESIGN
Although the mass ratio of 1:1 provided a nonhazardous waste,
it is recommended that a minimum ratio of 5:1 be used to design the
process. This may be desired sometime in the future due to changes
in waste quality or the need for a better end product and will give
an adequate safety factor.
The following presents recommended sizes of equipment:
Dry Hopper - 5 ton capacity = 111 Cu. Ft.
Slurry Tank - (assume 2000«/day of LFA $ 15% solids in slurry and
that it takes 2 runs to empty 1500 gallon tank due
to heavier loading on the filter) = 750 gal = 90 cu.
ft.
Control Package -
1. Screwtype dry chemical feeder - power controlled
by (2) As level is reached at (2) in slurry tank
power in (1) is activated and measured amount of
dry chemical is added;
2. High level controller for slurry tank - Controls
valve from 1500 gallon holding tank. As level is
reached, valve is closed and dry chemical is added
as described in (1);
3. Low level controller for slurry tank - Controls
valve from 1500 gallons holding tank. As level is
reached, valve is opened to refill slurry tank;
4. Emergency Level Backup - If this control is reached,
purap is shut off until slurry tank is refilled.
Prohibits filtration of pure waste;
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3. Valve - Allows filling of slurry tank from 1500
gallon holding tank;
6. High level indicator. (exist ing);
7. Low level indicator (existing);
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5. Valve - Allows filling of slurry tank from 1500
gallon holding tank;
6. High level indicator, (exist ing);
7. Low level indicator (existing);
8. Pump - Two way dual flow diaphragm pump - Allows
controlled flow of slurry and plating sludge.
9. Mixer - Controlled by high level indicator (2) is
slurry tank and screw type chemical feeder (1).
U.S. Environmental Protection
Region 5, Library (Pi.-1.2J)
77 West Jackson Bc'.'!v.v. J, 1':i;.i floor
Chicago, IL 60604-3590
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