&EPA
United States Office of Research and
Environmental Protection Development
Agency Washington DC 20460
EPA/540/AR-93/513
September 1995
EPOC Water Inc.
Microfiltration Technology
Applications Analysis Report
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
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CONTACT
S. Jackson Hubbard is the EPA contact for this report. He is presently with the newly organized
National Risk Management Research Laboratory's new Land Remediation and Pollution
Control Division in Cincinnati, OH (formerly the Risk Reduction Engineering Laboratory).
The National Risk Management Research Laboratory is headquartered in Cincinnati, OH, and
is now responsible for research conducted by the Land Remediation and Pollution Control
Division in Cincinnati.
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EPA/540/AR-93/513
September 1995
EPOC Water Inc. Microfilitration Technology
Applications Analysis Report
NATIONAL RISK MANAGEMENT RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OH 45268
Printed on Recycled Paper
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Notice
The information in this document has been funded by the U.S. Environmental Protection Agency under Contract No.
68-CO-0048 and the Superfund Innovative Technology Evaluation (SITE) Program. It has been subjected to the
Agency's peer review and administrative review, and it has been approved for publication as a U.S. EPA document.
Mention of trade names or commercial products does not constitute an endorsement or recommendation for use.
11
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Foreword
The U.S. Environmental Protection Agency is charged by Congress with protecting the Nation's land;
air, and water resources. Under a mandate of national environmental laws, the Agency strives to formulate and
implement actions leading to a compatible balance between human activities and the ability of natural systems
to support and nurture life. To meet this mandate, EPA's research program is providing data and technical
support for solving environmental problems today and building a science knowledge base necessary to manage
our ecological resources wisely, understand how pollutants affect our health, and prevent or reduce environmental
risks in the future.
The National Risk Management Research Laboratoiy is the Agency's center for investigation of
technological and management approaches for reducing risks from threats to human health and the environment.
The focus of the Laboratory's research program is on methods for the prevention and control of pollution to air,
land, water and subsurface resources; protection of water quality in public water systems ; remediation of
contaminated sites and ground water; and prevention and control of indoor air pollution. The goal of this research
effort is to catalyze development and implementation of innovative, cost-effective environmental technologies;
develop scientific and engineering information needed by EPA to support regulatory and policy decisions; and
provide technical support and information transfer to ensure effective implementation of environmental
regulations and strategies.
This publication has been produced as part of the Laboratory's strategic long-term research plan. It is
published and made available by EPA's Office of Research and Development to assist the user community and
to link researchers with their clients.
E. Timothy Oppelt, Director
National Risk Management Research Laboratory
111
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Abstract
This document is an evaluation of the performance of the EPOC Water, Inc. Microfiltration Technology and its
applicability as a treatment technique for water contaminated with metals. Both the technical aspects and the
economics of this technology were examined. Operational data and extensive sampling and analysis information
were carefully compiled to establish a data base against which the vendor's claims for the technology have been
compared and evaluated. Other information provided by the vendor, and summarized in this report, was also taken
into account in this evaluation. Conclusions concerning the technology's suitability for use in removing metals from
acid mine drainage were reached, and extrapolations regarding applicability to other sites with different contaminants
and liquid wastes are also provided.
EPOC's system consisted of a reaction (precipitation) chamber, microfiltration units, dewatering units, and auxiliary
equipment. The microfiltration unit (EXXFLOW) utilizes a unique fabric support operating with a formed-in-place
dynamic membrane. The system also includes a pressurized tubular fabric dewatering unit, the EXXPRESS, which
operates on the same_microfiltration principles. According to the vendor, particulates 0.1 /un in diameter or larger
are removed by the EXXFLOW and the concentrate (reject) slurry can be dewatered in the EXXPRESS. Dissolved
metals present in acid mine drainage water or other contaminated waters first must be precipitated by chemical
treatment to enable removal by filtration.
The EPOC Microfiltration Technology was demonstrated under the U.S. EPA SITE program at the Iron Mountain
Mine Superfund site near Redding, California in May and June of 1992. The water source for most of this
demonstration, acid mine drainage from the Old No. 8 Mine Seep, contained about 3,000 mg/L of total metals,
primarily aluminum and iron, with much smaller concentrations of heavy metals. Chemical precipitation with
various alkalies and recirculation through the EXXFLOW microfiltration unit increased the suspended solids in the
concentrate to about 10,000 to 35,000 mg/L. Further concentration and dewatering with the EXXPRESS achieved
12% to 30% solids in the filter cakes, rather than the claimed 20% to 40%, depending on the alkali used for
precipitation. Considerable operating difficulty was encountered with the EXXPRESS unit as configured for the
demonstration. The filter cakes all passed the TCLP.
The permeate from the ON8 seep using the EXXFLOW was of high quality. The metals were successfully
removed, meeting all claims with the exception of aluminum and, occasionally, manganese and iron. Where
elevated concentrations of heavy metals were present (e.g., copper at 170 mg/L), these were consistently reduced
to less than 0.1 mg/L (e.g., copper in permeate: <0.05 mg/L). The permeate turbidity was consistently less than
1 NTU in all cases. The permeate pH was usually in the 9 to 10 range and would probably require acidification
before it could be discharged.
The estimated cost for a 1-yr remediation using two sizes of the EPOC EXXFLOW system was $125.00/1000 gal
($33.50/m3) for the 7 gpm (26.5 L/min) pilot-scale unit with no dewatering of the concentrate, $103/1000 gal .
(S27.25/m3) with conventional dewatering and $47.40/1000 gal ($12.50/m3) for the 50 gpm (190 L/min) full-scale
system with dewatering. The EXXPRESS unit was not used in the cost analysis.
This demonstration was conducted for the Risk Reduction Engineering Laboratory (now the National Risk
Management Research Laboratory) hi April-July 1992, and work was completed as of September 1993.
IV
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Contents
Page
Foreword :...., iii
Abstract iv
Tables vii
Figures viii
Abbreviations and Symbols ix
Conversion Factors x
Acknowledgments ,....' xi
1. Executive Summary . 1
1.1 Introduction : 1
1.2 Conclusions 1
1.3 Discussion of Conclusions '. .'.' 2
2. Introduction 4
2.1 The SITE Program 4
2.2 SITE Program Reports : 4
2.3 Key Contacts 5
3. Technology Applications Analysis 6
3.1 Introduction 6
3.2 Conclusions 6
3.3 Technology Evaluation 7
3.4 Ranges of Site Characteristics Suitable for the Technology 9
3.5 Applicable Wastes for the Technology 10
3.6 Environmental Regulatory Impacts 11
3.7 Manpower Requirements 13
3.8 Testing Requirements 13
4. Economic Analysis ^ 14
4.1 Introduction 14
4.2 Conclusions 14
4.3 Issues and Assumptions 15
4.4 Basis for Economic Analysis 16
4.5 Results 20
4.6 Development of a 700 GPM Microfiltration System 21
Appendices
A. Process Description 22
A. 1 Introduction . 22
A.2 The Reaction Tank 22
A.3 EXXFLOWUnit 22
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Contents (continued)
Page
A.4EXXPRESSUnit 25
A.5 Sludge Dewatering 25
B. Vendor's Claim26
B.I Introduction 26
B.2 EPOC Microfiltration Technology 26
B.3 Applications of the EPOC EXXFLOW/EXXPRESS Technology 29
B.4 System Advantages 29
C. Demonstration TestResults 31
C.I Introduction 31
C.2 Site Description 31
C.3 Wastewater Contamination Characteristics 31
C.4 Review of Site Demonstration , 31
D. Case Studies 41
D.I Bench Scale Treatability Testing : -.... 42
D.2 Hazardous Waste Reduction 43
D.3 Groundwater Remediation 44
D.4 Zero Discharge of Ceramics Waste 45
D.5 Industrial Wastewater 46
VI
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Tables
Number Page
3-1. Effect of EXXFLOW Microfiltration 8
3-2. Filter Cake Production from EPOC Process 8
4-1. Estimated Costs for 7 gpm Pilot-Scale Unit 17
4-2. Estimated Costs for 50 gpm Full-Scale Unit 17
B-l. Wastes Compatible with the EPOC System 29
C-l. EPOC Demonstration Test Runs Performed at IMM Site 37
C-2. Treated Effluent Quality-Composite Samples 37
C-3. EPOC Microfiltration Summary 39
C-4. Filter Cake Output from EPOC EXXPRESS 40
C-5. Filter Cake Metal Content 40
D-l. Treatability Test Results 42
D-2. Removals of Hazardous Constituents 43
D-3. Concentration Comparison 45
Vll
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Figures
Number Page
3-1. Aluminum-Alkalinity Relationship 8
A-l. EXXFLOW Filtration Technology and Flexible Tube Module 24
A-2. EXXFLOW Crossflow Microfilter 24
A-3. EXXPRESS Automatic Sludge Dewatering System 24
B-l. Typical Vertical Module Configuration 27
B-2. EPOC Microfiltration Process Schematic 27
B-3. EXXPRESS Dewatering Schematic , 28
C-l. Iron Mountain Mine Location Map Showing Richmond Portal, Old No. 8 Mine Seep and Other
Point and Nonpoint Sources 32
D-l. Talley Corporation Process Schematic 44
Vlll
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Abbreviations and Symbols
AMD
CERCLA
gpm
HSWA
kWh
mg/L
NPDES
PEL
MTU
ORD
OSHA
OSWER
NPL
POTW
ppb
ppm
psi
psig
QA/QC
RCRA
RREL
SAIC
SARA
scfm
SITE
TCLP
TSD
VOC
Acid Mine Drainage
Comprehensive Environmental Response, Compensation, and Liability Act of 1980
gallons per day
gallons per minute
Hazardous and Sob'd Waste Amendments to RCRA - 1984
kilowatt-hour
milligrams per liter
National Pollutant Discharge Elimination System
Permissible Exposure Limit
Nephelometric Turbidity Units
Office of Research and Development
Occupational Safety and Health Administration or Act
Office of Solid Waste and Emergency Response
National Priorities List
publicly owned treatment works
parts per billion (jig/1)
parts per million (mg/L)
pounds per square inch pressure
pounds per square inch, gauge pressure
Quality Assurance/Quality Control
Resource Conservation and Recovery Act of 1976
Risk Reduction Engineering Laboratory
Science Applications International Corporation
Superfund Amendments and Reauthorization Act of 1986
standard cubic feet per minute
Superfund Innovative Technology Evaluation
Toxicity Characteristic Leaching Procedure
Treatment, Storage, and Disposal
Volatile Organic Chemical
IX
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Conversion Factors
Area:
Flow Rate:
Length:
Mass:
Volume:
Pressure:
English (US)
1ft2
lin2
1 cfin
1 gal/min
1 gal/min
IMgal/d
IMgal/d
IMgal/d
1ft
lin
lyd
lib
lib.
1ft3
1ft3
Igal
Igal
1 psia
x Factor
: Metric
x 929 x 10"2
x 6.45
x 2.83 x 10"2
x 6.31 x 1(T5
x 6.31 x Iff2
x 43.81
x 3.78 x 103
x 4.38 x 10"2
x 0.30
x 2.54
x 0.91
x 4.54 x 102
x 0.454
= m2
= cm2
SB m3/min
= m3/s
= L/s
= L/s
= m3/d
= m3/s
= m
= cm
= m
= g
- kg
x 28.31
x 2.83 x 10-2
x 3.78
x 3.78 x Iff3
x 51.71
ft s fool, ft3 = square foot, ft3« cubic foot
in = inch, in2 = square inch
yd = yard
Ib s pound
gal = gallon
gal/min (or gpm) = gallons per minute
MgaJ/d (or MOD) = million gallons per day
m = meter, m2 = square meter, m3 = cubic meter
cm s centimeter, cm2 = square centimeter
L s liter
g SB gram
kg SB kilogram
cfm = cubic feet per minute
L/s = liters/sec
m3/d = cubic meters per day
= m3
cm Hg
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Acknowledgments
This report was prepared under the direction and coordination of Mr. Jack Hubbard, EPA Superfund Innovative Technology
Evaluation (SITE) Project Manager in the National Risk Management Research Laboratory (formerly the Risk Reduction
Engineering Laboratory), Cincinnati, Ohio. Contributing authors were: Mr. Robert Dvorin, Mr Dan Patel Mr Rav
Martrano, Ms. Linda Hunter and Ms. Ruth Alfasso of SAIC. ' '
This report was prepared for EPA's SITE Program by the Environmental Technology Division of Science Applications
International Corporation (SAIC) under U.S. EPA Contract No. 68-CO-0048.
XI
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Section 1
Executive Summary
1,1 Introduction
The EPOC microfiltration technology, using a dynamic
(formed-in-place) membrane to remove, concentrate, and
dewater suspended solids (down to 0.1 micrometer, urn,
diameter), was evaluated on acid mine drainage (AMD) at
the Iron Mountain Mine Superfund site near Redding,
California. Operating and cost data collected from this
demonstration provide the basis for this evaluation.
Microfiltration allows for removal of very small particles of
suspended solids (to 0.1 um). A dynamic membrane, which
is constantly renewed, is expected to be more resistant to
plugging and fouling, thereby requiring less downtime for
cleaning. The EPOC system used a patented design of
woven textile tubes as the support for the dynamic
membranes.
The dissolved metals in the acid mine drainage were
precipitated with various alkalies in a mechanically mixed
reaction tank, physically separated and concentrated in the
EPOC EXXFLOW microfiltration unit, and dewatered in the
EPOC EXXPRESS system. The final products of this
process are the decontaminated water and a small volume of
filter cake containing the contaminants.
This report offers information useful in assessing the
suitability of this process to other similar sites, and includes
additional information (supplied by the developer) relative to
performance on other types of contaminated water.
The primary objectives of this demonstration were to:
Assess the ability of the EPOC microfiltration
technology to remove metals present in the acid
mine drainage (AMD) at the Iron Mountain Mine
site, using various precipitating chemicals;
Evaluate the technology's capability to dewater the
metals-bearing sludge formed as result of the
treatment of the AMD wastewater.
.Assess the quality of the treated water and the dewatered
metals-bearing sludge thus produced, and
Develop capital and operating costs for the EPOC
microfiltration technology.
1.2 Conclusions
The results and observations of the SITE demonstration at
Iron Mountain Mine provide the bases for the following
conclusions:
A. When operated at a rate of about 11 L/min (3 gpm) on
acid mine drain water containing about 3000 mg/L of
total metals:
The EXXFLOW microfiltration system met the
developer's claims for removal of heavy metals in the
AMD but did not meet the claim for aluminum (1 mg/L)
with all alkalies used as the precipitating chemical.
The EPOC microfiltration system reduced cadmium,
copper, and zinc in the permeate to <50 ppb each.
Aluminum was reduced to less than 1 mg/L when
magnesium oxide (MgO) was used; hydrated lime
(Ca(OH),) or caustic soda (NaOH) produced residual
concentrations of about 15-50 mg/L of aluminum.
How rate, pressure, and a flux of about 2650 L/m2-day
(65 gal/ft^day) were essentially constant for the duration
of each demonstration run (4 to 6 hr), indicating that the
EXXFLOW unit should operate for extended times with
minimal maintenance and cleaning.
The EXXPRESS dewatering unit experienced serious
operating problems that required operator attention and
prevented effective evaluation.
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Dewatered filter cake volume was less than 5% of the
treated water volume in all runs (i.e., water recovery
as permeate was 95% or better).
None of the filter cakes met the developer's claims
for solids content Caustic treatment produced a
sludge cake with about 12% dry solids (claimed:
>20%). Hydrated lime, magnesium oxide, or a
combination of magnesium oxide and caustic soda
treatment resulted in filter cakes containing about
30% dry solids (claimed: >40% with lime).
The dewatered filter cakes, in all rims, passed the
TCLP (toxicity characteristic leaching procedure) test
but were composed primarily of metals other than
those analyzed in the test (e.g., Al, Fe).
Based on the demonstration tests, other information,
and the use of other dewaiering approaches for the
concentrate, the cost to treat metal contaminated
wastes such as the ON8 acid mine drainage is
estimated at $125/1000 gal ($33/m3) with a 7 gpm
(26.5 L/min) unit with disposal of the reject as a
liquid waste and' $103/1000 gal ($27/m3) with
dewaiering of the reject stream. For a 50 gpm (190
L/min) system, with dewatering of the reject, the
estimated cost is $47.40/1000 gal ($12.50/m3). These
costs are based on a 90% on-line factor, a total
treatment time of twelve months, and 50% sodium
hydroxide as the treatment chemical. The cost of
caustic is a major cost factor.
B. When acid mine drainage containing about 20,000 mg/L
of dissolved metals (primarily iron, aluminum, copper,
and zinc) was treated at a rate of 3.8 L/min (1.0 gpm)
with a combination of magnesium oxide and caustic
soda:
Residual metals in the permeate met the developer's
claims except for iron (which was, nevertheless,
reduced by 99.9%), cadmium, and manganese.
Flux in the EXXFLOW unit was maintained at about
730 L/m2»day (18 gal/fr'-day) with a feed
concentration of about 7% w/w suspended solids.
Dewatered filter cake passed the TCLP test for
metals. Dry solids in the dewatered filter cake, 26%,
did not meet the 40% claim. Water recovery was
76%.
C. The EPOC system may have utility in removing metals
and suspended solids from a wide variety of waste and
process streams. The system requires minimal floor
space and probably can surpass other clarification means
where needed to meet discharge requirements. Metal-
containing streams would be well-suited to the process,
and, based on information provided by the developer, oil
emulsions and other solids that do not settle readily may
be good candidates.
1.3 Discussion of Conclusions
A trailer-mounted EPOC microfiltration system with a
design flow rate of 26.5 L/min (7 gpm) but operated at 11
L/min (3 gpm) and 3.8 L/min (1 gpm) was tested at the Iron
Mountain Mine Superfund site. Extensive data were
collected over nine demonstration runs of 4 to 6 hr duration
to assess (a) dissolved metals reduction, (b) sludge
dewatering capabilities, (c) operational requirements, and (d)
operating costs. Data generated by this testing serve as the
basis for the preceding conclusions.
A Quality Assurance (QA) program was conducted by S AIC
in conjunction with EPA's QA program, which includes
audits and data review as well as corrective action
procedures. This program is the basis for the high quality
of data obtained from the SITE project
Extensive data were collected on the metals, acidity,
alkalinity, pH, sulfate, and total solids of the water before
and after treatment Suspended solids concentration of the
feed to the microfilter was determined. The dewatered filter
cake was analyzed for moisture, density, pH, metals, and
TCLP (toxicity characteristic leaching procedure) for metals.
The key factors affecting performance of the system were
neutralizing chemical choice and chemical feed rate control.
Caustic soda produced the most hydrated sludge cake, which
is to be expected. Aluminum concentrations in the permeate
remained higher than anticipated when either caustic or lime
was used because it was difficult to control the pH and any
excess alkali redissolved the amphoteric aluminum.
Magnesium oxide, and a combination of magnesium oxide
and caustic, allowed more precise control of pH and this was
reflected in improved aluminum removal.
The EXXFLOW microfiltration unit operated effectively in
producing a permeate with very little residual metals. With
the Old No. 8 Mine Seep water, about 95% of the feed
water could be recovered as permeate meeting all heavy
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metal objectives. With the Richmond Portal AMD
containing significantly higher concentrations of aluminum,
iron and other metals, permeate water accounted for 76% of
the feed water. Although the several runs were shorter than
planned, the absence of any gradual deterioration in flow
rate, pressure, or flux suggests that the microfiltration unit
would operate over a long time with minimal downtime for
cleaning.
In addition to affecting the nature of the solids and the rate
at which they are produced, the chemical agent apparently
also affected the ease with which the sludge generated in the
EXXFLOW microfiltration unit could be further dewatered
in the EXXPRESS unit The result was that sludge generated
by caustic precipitation could only be dewatered to about
12% solids, while lime or magnesium oxide produced
sludges that could be dewatered to 25% to 32% solids.
The EXXPRESS dewatering unit required frequent attention
and manual cleaning, seemingly because the high
concentration of metal hydroxides did not act hydraulically
within the tubes as expected and the unit plugged. Almost
constant operator attention was required on some runs.
Either this device requires design modification to operate on
heavy loads of metal hydroxide sludges, or it may be more
suited for applications where the nature or quantity of solids
is different
Costs were estimated for two system sizes and assumed that
approaches other than the EXXPRESS dewatering unit are
used to process the reject concentrate from the EXXFLOW.
Direct disposal of the reject stream is more costly than
dewatering, accounting for 36% of the pilot-plant costs.
With dewatering, the cost for management of the reject
decreased to 23%. In the full-scale system, dewatering
accounts for 14.2% of the cost Neutralizing chemical cost
for a given volume of wastewater will remain essentially the
same for any size of treatment system, but could change
significantly with different wastewaters.
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Section 2
Introduction
2.1 The SITE Program
In 1986, the EPA's Office of Solid Waste and Emergency
Response (OSWER) and Office of Research and
Development (ORD) established the Superfund Innovative
Technology Evaluation (SHE) program to promote the
development and use of innovative technologies to clean
up Superfund sites across the country. SITE is helping to
provide the treatment technologies necessary to implement
new federal and state cleanup standards aimed at
permanent remedies, rather than quick fixes. The SITE
program is composed of four major elements: the
Demonstration Program, the Emerging Technologies
Program, the Measurement and Monitoring Technologies
Program, and the Technology Transfer Program.
The major focus has been on the Demonstration Program,
which is designed to provide engineering and cost data on
selected technologies. EPA and developers participating
in the program share the cost of the demonstration.
Developers are responsible for demonstrating their
innovative systems at chosen sites, usually Superfund
sites. EPA is responsible for sampling, analyzing, and
evaluating all test results. The result is an assessment of
the technology's performance, reliability, and cost This
information will be used in conjunction with other data to
select the most appropriate technologies for the cleanup of
Superfund sites.
Developers of innovative technologies apply to the
Demonstration Program by responding to EPA's annual
solicitation. EPA will also accept proposals at any time
when a developer has a treatment project scheduled with
Superfund waste. To qualify for the program, a new
technology must be at the pilot- or full-scale stage and
offer some advantage over existing technologies. Mobile
and in situ technologies are of particular interest to EPA.
Once EPA has accepted a proposal, EPA and the
developer work with the EPA Regional Offices and state
agencies to identify a site containing wastes suitable for
testing the capabilities of the technology. EPA prepares
a detailed sampling and analysis plan designed to evaluate
the technology thoroughly and to ensure that the resulting
data are reliable. The duration of a demonstration varies
from a few days to several months, depending on the
length of time and quantity of treated waste needed to
assess the technology. After the completion of a
technology demonstration. EPA prepares two reports.
which are explained in more detail below. Ultimately, the
Demonstration Program leads to an analysis of the
technology's overall applicability to Superfund problems.
The second principal element of the SITE Program is the
Emerging Technologies Program, which fosters the further
investigation and development of treatment technologies
that are still at the laboratory scale. Successful validation
of these technologies could lead to the development of a
system ready for field demonstration. The third
component of the SITE program, the Measurement and
Monitoring Technologies Program, provides assistance in
the development and demonstration of innovative
technologies to better characterize Superfund sites. The
final component, the Technology Transfer Program,
disseminates the information from all the studies to
interested parties in the remediation community in the
form of reports, bulletins, etc.
2.2 SITE Program Reports
The analysis of technologies evaluated in the
Demonstration Program is contained in two documents:
the Technology Evaluation Report and the Applications
Analysis Report The Technology Evaluation Report
contains a comprehensive description of the demonstration
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sponsored by the SITE program and its results. It gives a
detailed description of the technology, the site and waste
used for the demonstration, sampling and analysis during
the test, the data generated, and the quality assurance
program.
The scope of the Applications Analysis Report is broader
and encompasses estimation of other Superfund and
hazardous waste site applications and costs of a
technology based on all available data. This report
summarizes the results of the SITE demonstration, the
vendor's design and test data, and other laboratory and
field applications of the technology. It discusses the
advantages, disadvantages, and limitations of the
technology as they may pertain to other sites with different
characteristics.
Costs of the technology for different applications are
estimated in the Applications Analysis Report, based on
available data on pilot- and full-scale applications. The
report discusses factors such as site and waste
characteristics that have a major impact on costs and
performance.
The amount of available data for the evaluation of an
innovative technology varies widely. Data may be limited
to laboratory tests on synthetic waste, or may include
performance data on actual wastes treated at the pilot- or
full-scale. Nevertheless, there are limits to conclusions
regarding Superfund applications that can be drawn from
a single field demonstration. A successful field
demonstration does not necessarily assure that a
technology will be widely applicable or fully developed to
the commercial scale. The Applications Analysis Report
attempts to synthesize whatever information is available
and draw reasonable conclusions. This document will be
very useful to those considering the technology for
Superfund cleanups and represents a critical step in the
development and commercialization of the treatment
technology.
2.3 Key Contacts
For more information on the demonstration of the EPOC
Microfiltration technology, please contact:
1. EPA Technical Project Manager concerning the
SITE demonstration:
S. Jackson Hubbard
U.S. EPA Risk Reduction Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
(513) 569-7507
2. Vendor concerning the process:
Scott Jackson
EPOC Water, Inc.
3065 Sunnyside, #101
Fresno, CA 93727
(209) 291-8144
3. For further information concerning The Iron
Mountain Test site:
Rick Sugarek
Remedial Project Manager
U.S. Environmental Protection Agency
75 Hawthorne Street
San Francisco, CA 94105
(415)744-2226
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Section 3
Technology Applications Analysis
3.7 Introduction
This section of the report addresses the applicability of the
EPOC Microfiltration process to waste streams that contain
dissolved solids which can be precipitated and removed from
the aqueous phase. This discussion is based upon
information gathered from the SITE demonstration tests
conducted at Iron Mountain Mine in Redding, CA and other
information provided by the vendor. The demonstration tests
provided a data base on which this process can be judged as
to its applicability to this type of waste at other sites.
Additional information for application of the EPOC
microfiltration process at other sites, and with other wastes,
is presented in Appendix D. The Technology Evaluation
Report, a separate EPA document, provides an in-depth
discussion of this SITE demonstration test and the analytical
results.
The EPOC Microfiltration process is based on the ability of
a semi-permeable membrane to retain suspended particulates
while allowing the water and dissolved species to pass
through the membrane. Microfiltration processes typically
remove particles in the O.lum to 1.0pm range. EPOC's
technology consists of a patented crossflow microfiltration
module using dynamic membrane technology to achieve
filtration separations for particles in the range of O.lum to
0.2pm with minimal fouling of the membrane and,
consequently, minimal decrease in flux [throughput] over
time. Suspended solids in the feed water deposit on the
inner surface of porous tubes in the microfiltration module
to form the dynamic membrane, and it is this membrane that
controls the filtration process. Dissolved solids, e.g., metal
ions, are chemically reacted to form particles which can then
be filtered from the host liquid.
3.2 Conclusions
The following are overall conclusions from the evaluation of
the EPOC Microfiltration process. The "Technology
Evaluation" subsection discusses the data generated from the
demonstration test in support of these conclusions.
Dissolved heavy metals can be successfully removed
from the water stream by the microfiltration process
(EXXFLOW) when precipitated with any of several
alkalies.
The system generally met the vendor's claim for
reduction of heavy metals in the permeate to <0.1
mg/L, but did not consistently meet claims for
aluminum and iron reduction to <1 mg/L. High
concentrations of these two metals in the AMD feed
waters and high alkalinity in the treated water may
have been contributing factors. It must be noted,
however, that some heavy metal concentrations in the
feed water were below the claimed final
concentrations.
The performance of the EXXFLOW microfiltration
system and the quality of the product water are
dependent on the choice of base used for
precipitation.
The quantity and quality of the filter cake is a
function of die base used. The filter cakes from the
EXXPRESS dewatering system did not meet the
vendor's claims of >20% solids (from caustic) and
>40% solids (from lime).
The system can produce filter cake from these AMD
waters that will pass the TCLP requirement,
recognizing that aluminum and iron were the major
constituents in the sludge.
The EXXPRESS dewatering unit required
considerable attention and did not operate effectively
as configured by the vendor for the demonstration.
-------
Each waste stream to be treated by the process
requires detailed characterization and selection of
treatment chemicals and additives in order to develop
optimal operating parameters.
The cost for treatment with the EXXFLOW process has
been estimated at about $103/1000 gal with a 26.5
L/min (7 gpm) unit such as the pilot-plant system tested
and decreases to about $47/1000 gal for a 190 L/min
(50 gpm) unit, both coupled with dewatering of the
reject. Chemical cost is a major factor with both units,
but decreases significantly on scale-up. These costs
were developed with a conventional filter press for
dewatering because the EXXPRESS unit could not be
operated effectively during the demonstration.
It was not possible to determine the long term utility or
reliability of the system since run lengths were limited
to about 4 to 6 hours. However, there was little change
in flux over the course of the tests, suggesting that
extended operation of the EXXFLOW unit was feasible.
Adjustment of the product water pH may be required
before discharge, depending upon regulatory
requirements.
The process can be designed as a transportable unit or
a permanent installation. For given sizes of
EXXFLOW/EXXPRESS units, a reasonably wide range
of process flow rates can be accommodated.
The process requires a limited amount of site
preparation before installation, including electric power
and a level area for the unit Units then can be placed
in operation after a 1 to 2 week shakedown period.
3.3 Technology Evaluation
The following provides a more detailed discussion of the
chemical and operational test results that were used to
develop the foregoing conclusions. A summary of the test
and analytical data is presented in Appendix C. Information
on other applications of this technology along with
performance data is presented in "Appendix D Case
Studies". The estimated cost to treat waste streams is
presented in detail in Section 4, "Economic Analysis".
3.3.1 Chemical Test Results
The EPOC Microfiltration technology is designed to remove
suspended solids from liquid wastes. Dissolved
contaminants must first be converted to particulates (of
appropriate size) using conventional technologies. Dissolved
metals, which were the focus of this SITE demonstration
test, can be treated with lime, caustic or magnesium oxide to
precipitate the metals by forming insoluble metal hydroxides
(and/or carbonates). The contaminant metals can then be
removed from the water stream by filtration such as the
EPOC microfiltration system. Other species, such as oils,
can be coagulated or aggregated with or on coagulants and
polyelectrolytes.
The SITE demonstration test was conducted at Iron
Mountain Mine, Redding, CA. This site is contaminated
with several acid mine drainage water sources that contain
heavy metals. Two water sources were tested during the
demonstration, Old No. 8 Mine Seep and Richmond Portal.
Both waste streams are contaminated with high levels of
iron, aluminum, copper and zinc. Several other metals were
present at much lower levels, but were still considered
critical in the evaluation of this technology.
Eight test runs were performed on water collected from the
Old No. 8 Seep using caustic, lime, magnesium oxide, and
a combination of caustic and magnesium oxide as the
precipitating base. A combination of caustic and magnesium
oxide also was evaluated on water from the Richmond Portal
seep. One to three hours were required to reach and maintain
the desired pH (over 9) in the reaction tank before operation
of the EXXFLOW unit was initiated. Completed test runs
aveiaged 4 to 5 hours during which grab and composite
samples were collected of the raw feed, permeate, and filter
cake. These samples were analyzed for metals to determine
removal efficiencies. Other parameters were also measured
to evaluate, for example, solids content of the filter cakes.
Caustic soda or lime treatment resulted in metals
concentration well below the developer's claims, except for
aluminum (and manganese), in the permeate from the
EXJCFLOW microfiltration unit.
The treated water pH and alkalinity were extremely sensitive
to small changes in alkali feed rate, particularly with the
soluble sodium hydroxide. A feed rate of 9 g/L of caustic
(100%) was targeted and maintained while the reaction
vessel was being filled and treated at a nominal 12 L/min (3
gpm) rate; at this rate an excess of 0.1 g/L (about 1%)
would produce 100 mg/L excess alkalinity. In field tests
during the caustic runs, aluminum in grab samples increased
from 2.5 ppm at a pH of 8.3 to 100 ppm at pH 12 while the
alkalinity was 26 ppm and 740 ppm, respectively.
Aluminum in lime-treated water was about 18 ppm at a pH
of about 10.5 and alkalinity of 90 ppm, and less than one
ppm at an 8.8 pH and 44 ppm alkalinity. The amphoteric
character of aluminum at elevated pH is well known.
Figure 3-1 shows the relationship between treated water,
aluminum content and alkalinity. Alkalinity may be a more
-------
Table 3-1. Effect of EXXFLOW Mkroflltratfon
IUUU
100
f '°
5
^
1
0,
»
\ - -,
\ i
\!/
V
X
* >
(i
i
V, A
* '/^
\ / \ .
\ * V -' ^
\ \// -j.--*
\ /
X
~ ^
-*« ^
\
\
u
\
1000
'00
IO
1 2 3 4 5 B 7 8 9 10 11 12 13 14 15 18 17 1» It M
Fig. 3-1 Aluminum-Alkalinity Relationship
important factor than pH based on the grab sample results
for caustic and lime treatment Based on mis limited
information, at other sites it may be necessary to measure
alkalinity and choose the precipitating alkali and the rate of
introduction so that removal of aluminum (and possibly zinc)
is maximized.
Magnesium oxide provided more reliable control due to its
much lower solubility at elevated pH, but required a longer
time for equilibrium to be reached. Total metal reduction
was about two orders of magnitude with magnesium oxide.
Some metals, such as copper, were reduced four orders of
magnitude.
In some of the tests, residual concentrations of some metals
in the permeate were below published solubilities, perhaps
due to added benefits attributable to the dynamic membrane,
as reported in other microfiltration studies.
Table 3-1 compares metal concentrations, pH, and alkalinity
in the feed waters with those in the permeate from the Old
No. 8 Seep. Similar results were observed in the single test
run using the Richmond Portal seep. Tables C-2 and C-3 in
Appendix C provide more detailed information about the test
runs.
Parameter
aluminum
cadmium
copper
iroo
lead
manganese
nickel
zinc
pH
feed cooc.,
mg/L
700
03
170
2000
0.2
15
0.2
60
23
permeate cone..
claim
1.0
0.1
0.1
1.0
1.0
0.1
0.1
0.1
-
NaOH
36
<0.006
0.05
03
<0.02
0.01
<0.03
0.03
9.7
Ca(OH)j
15
<0.01
<0.025
0.15
cO.1
<0.015
<0.05
<0.03
10.4
mg/L
MgO
<0.26
<0.01
<0.025
0.15
0.2
0.27
<0.05
<0.03
9.3
MgO/
NaOH
-------
EPOC evaluated each AMD waste stream and selected
operating parameters and treatment chemicals based upon
bench-scale treatabilitv tests.
Three treatment chemicals were selected for evaluation at
Iron Mountain: hydrated lime, i.e., calcium hydroxide or
Ca(OH)j, sodium hydroxide (50% liquid caustic soda,
NaOH), and magnesium oxide (MgO). Tests were also
conducted using a combination of sodium hydroxide and
magnesium oxide. Each of these chemicals yielded very
different operating and sludge characteristics.
Prcdemonstration shakedown runs were performed by EPOC
using hydrated lime. This established the unbuffered quality
of this water. In both the predemonstration and the
demonstration tests, treated water pH was extremely
sensitive to very small changes in chemical feed rate, and
very tight control was required to prevent pH excursions of
as much as a full unit The volume and characteristics of
the sludge formed presented operating problems, particularly
with the EXXPRESS dewatering system, which required
considerable attention, including frequent short downtime for
manual cleaning.
With sodium hydroxide, the first chemical evaluated during
the actual demonstration testing, reaction rates were quick
and pH control again was difficult to maintain with highly
variable pH results for the permeate during the start-up
period of each of the two runs. The sludge generated from
the process was very thin and there was some difficulty
during the shakedown activities with EXXPRESS unit
operation. EPOC evaluated the problems and made
adjustments to the EXXPRESS operation in an effort to
improve sludge production for the scheduled test
Throughout the demonstration tests, sludge was produced at
moderate rates (about 40-50 Ib/hr) and never dewatered to
the anticipated 20% solids content
With magnesium oxide as the base, reaction rates were much
slower. Approximately 2 hours were required to raise the
pH to 8; the low solubility of magnesium hydroxide limits
the pH to about 9. This facilitated pH control in the reaction
tank and the permeate samples. With good control of pH
during precipitation, enhanced removal of aluminum from
the permeate from the EXXFLOW was observed. However,
sludge recovery for the MgO runs was very low and
difficulty was again encountered with operation of the
EXXPRESS unit for dewatering during the demonstration
test runs. In addition, the physical properties of the sludge
produced with MgO were such that it was not possible to
form a "chip" or filter cake particle with the EXXPRESS.
Instead of adhering to the tube walls, the sludge was easily
washed back into suspension when the tubes were opened
for draining. Consequently, the EXXPRESS reject continued
to concentrate and plug the tubes even as EPOC attempted
to vary the flux in the press.
In all cases, the EXXFLOW flux remained essentially
unchanged at 2650 LAn2»day (65 gal/ft^day) over the course
of each test run. While the runs were not as long as
planned, a fall-off in flux would usually occur during the
early period if plugging were taking place; that was not the
case with these wastewaters and the EXXFLOW unit.
3.4 Ranges of Site Characteristics Suitable for
the Technology
3.4.1 Site Selection
The EPOC microfUtration system is readily transportable by
truck:. The unit size and configuration can be tailored to the
needs of the waste stream and the available area on the site
or in the treatment plant The system can either be designed
as one large unit or as several replicate modules, depending
on site and other needs.
The demonstration test unit (nominal 26 L/min, 7 gpm,
capacity) was transported on a trailer approximately 18 ft
long and 8 ft wide. This pilot-scale unit was transported to
the demonstration test site by a pickup truck over narrow
dirt roads. Any site accessible by an ordinary automobile
should be accessible to this size unit provided that the roads
have sufficient clearance. Larger units would be transported
as several individual modules.
3.4.2 Topographical and Area Requirements
A level and stable surface area larger than the unit size (18
ft x 8 ft) is required as well as room for the reaction tank,
storage tanks for the feed, permeate, and filter cake,
auxiliary equipment, and access. Grade should be no more
than approximately 1% and must be able to support the
equipment without allowing it to sink or tip. The trailer-
mounted unit can clear small obstructions such as rocks or
other surface irregularities.
The trailer-mounted unit stands less than 8 ft high and can
be placed inside of a building with at least that much
clearance.
3.4.3 Climate Characteristics
The ambient temperature can affect the reaction rate of
chemicals in the reaction tank. Under the normally-
encountered range of operating conditions, no major
problems should be experienced. However, perhaps more
-------
important is the potential impact of temperatures on flux
rale. Cold temperatures can also cause freezing of the
sodium hydroxide solution (if that is the alkali selected), the
feedwater. and the permeate. Mechanical and electrical
problems could also be encountered. If the system is to be
operated in a cold or freezing climate, modifications to the
systems to include heating coils and insulation could
overcome such problems. The unit can also be housed in a
healed structure to prevent cold-related problems.
High temperatures do not hinder treatment with the
technology but may be hazardous to personnel due to the
potential for heat stress disorders and contact with heated
metal parts.
Weather conditions such as rain or high winds do not
immediately damage the technology or prevent its operation.
In areas where the weather is frequently severe or highly
variable over the planned treatment time, the unit should be
sheltered to prevent damage from continuous exposure to the
elements and to ensure consistent operating conditions and
consistent product water and solids.
3.4.4 Utility Requirements
The EPOC microfiltration process requires a source of 240
volt, 3 phase electricity. During the demonstration, a
portable generator provided the necessary electricity to the
process at this remote site; the power could also be drawn
from a municipal power grid, if available.
Only a few hundred gallons per day of water for equipment
cleaning is required. Water would also be required for
emergency purposes and use in an on-site laboratory.
During the demonstration test, a portable compressor was
used to supply air for a diaphragm pump and pneumatic
valve operation. This requirement could be eliminated by
replacing these air-operated components with electric
counterparts. When treating some wastewaters, the
equipment may need occasional cleaning with hydrochloric
acid; during the demonstration, untreated feedwater (2.3 pH)
was used for this purpose.
3.5 Applicable Wastes for the Technology
The EPOC microfiltration technology may be applicable to
many different types of liquid wastes. To be treated with
the EXXFLOW and EXXPRESS technologies, the liquid
waste must have the following characteristics:
It must be pumpable.
The contaminants must be in paniculate form; the
particles must be large enough to be removed by the
dynamic membrane, or
It must be feasible to precipitate dissolved
contaminants such as metal ions chemically to allow
treatment and removal of the solids.
Separation must provide an advantage; i.e., the
hazardous characteristics of the wastewater must
become concentrated in either the sludge or the
permeate by the process.
Wastes of varying chemical and physical characteristics can
be treated by this technology. The materials of construction
of the mixing tanks, the tubing support textiles, and piping
can be varied to handle wastes which are corrosive. A non-
leachable (by TCLP) solid filter cake can be produced
depending on the toxic constituents in the liquid and the
chemical additives used.
Acid mine drainage is only one application for the EPOC
technology. Other applicable wastes may include
contaminated groundwater (dissolved/dispersed metals, fine
silf/clay), industrial or municipal wastewaters containing
solids and/or precipitable inorganic ion contamination (e.g.,
metal finishing); industrial process wastewater (e.g., pickle
liquor) for recycle or reuse of the water or solids; and
process sludges for production of a dry filter cake,
particularly where dewatering by other, conventional means
has proven ineffective.
The system is particularly well suited for removal of metals,
which tend to form difficult-to-separate sludges and which
can be precipitated readily with bases. Case studies reported
by the developer (Appendix D) have demonstrated that the
system also can treat organic compounds such as oil, grease,
pesticides, and kerosene where these can be coagulated or
adsorbed on a medium. Other organic pollutants that may
lend themselves to the technology could include textile dyes,
polymer latexes, fermentation broths, etc. The EPOC
technology does not remove volatile organic compounds
from liquids but presumably could be used in conjunction
with another technology to remove or treat the volatile
organic compounds. Evaluation of the system for organic
materials was beyond the scope of the site demonstration test
and at least laboratory testing would be necessary to evaluate
the effectiveness of the technology with any particular waste
stream.
In considering applications for the EPOC technology, the
required quality of the discharge and solids must be
considered, particularly when evaluating the cost-
effectiveness of alternatives. Microfiltration, as with the
EPOC EXXFLOW, can probably produce a more polished
permeate than obtainable by clarification in either a lagoon
or a clarifier. Dewatering, as with the EXXPRESS, could be
10
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very attractive where the sludge is hazardous, particularly
where sludge volume is a significant factor in disposal cost
3.6 Evironmental Regulatory Impacts
Operation of the EPOC dynamic membrane filtration process
for treatment of liquids containing heavy metals and/or other
contaminants will require compliance with certain Federal,
State and local regulatory standards and guidelines. This
technology may be used at Federal Superfund National
Priorities List (NPL) sites and other sites. Superfund site
regulatory requirements applicable to the use of this
technology are discussed below under Comprehensive
Environmental Response, Compensation, and Liability Act
(CERCLA). Other Federal, State and local environmental
regulations are subsequently discussed in more detail as they
apply to the performance, emissions and residuals of the
technology as evaluated during the demonstration test
3.6.1 The Comprehensive Environmental
Response, Compensation and Liability Act
(CERCLA)
The Comprehensive Environmental Response, Compensation
and Liability Act (CERCLA) of 1980 as amended by the
Superfund Amendments and Reauthorization Act (SARA) of
1986 provides for Federal funding to respond to releases of
hazardous substances to air, water, and land. Section 121 of
SARA, entitled cleanup standards, states a strong statutory
preference for remedies that are highly reliable and provide
long-term protection. It strongly recommends that remedial
actions use on-site treatment that "...permanently and
significantly reduces the volume, toxicity, or mobility of
hazardous substances." In addition, general factors which
must be addressed by CERCLA remedial actions are:
long-term effectiveness and permanence;
short-term effectiveness;
feasibility; and
cost
The EPOC dynamic membrane microfiltration technology
has been shown to remove >98% of toxic (cadmium, copper
and zinc) metals from the contaminated acid mine drainage
from the demonstration site. The combined EXXFLOW and
EXXPRESS process produced a filter cake which passed the
Toxicity Characteristic Leaching Procedure (TCLP). The
chemical precipitating reaction occurring before the filtration
process also raised the pH of the liquid so mat the water
exiting the process no longer exhibited the characteristic of
corrosivity.
The removal of the contaminants from the acid mine
drainage to the non-leachable filter cake was performed
rapidly by the process. Because the contaminants are then
separated from the water, this improvement is permanent
The contaminants removed are bound chemically and
physically in the filter cake solids, as evidenced by the
TCLP results.
The EPOC process equipment evaluated during the
demonstration was not designed to remove organic
contamination, and no volatile compounds were expected in
the liquids tested during the demonstration test. The
emissions potential in this situation is very low and is
limitsd to the potential for dust emissions while transporting
powdered treatment chemicals (e.g., lime). If liquids
containing volatile components were to be treated using this
technology, a pollution-control system could be used to
control emissions, or the volatile contaminants could be
removed first using a different technology (e.g., stripping)
before microfiltration.
In addition to the above general requirements, Section 121
of CERCLA requires that Superfund treatment actions must
meet or exceed "applicable or relevant and appropriate
requirements, criteria, or limitation under any Federal law or
State environmental statute." Local statutes may also be
relevant and appropriate. These criteria, as related to the
EPOC microfiltration technology, are discussed below.
3.6.2 Other Federal Regulations
The Resource Conservation and Recovery Act (RCRA) is
the primary Federal legislation governing hazardous waste
activities. Subtitle C of RCRA contains requirements for the
generation, transportation, treatment, storage and disposal of
hazardous waste, most of which are also applicable to
CERCLA activities.
The use to which the EPOC microfiltration technology was
put during the demonstration test would not have been
regulated under RCRA, as the acid mine drainage present at
the Iron Mountain does not fit the legal definition of a solid
waste, of which all RCRA hazardous wastes are a subset
The Biter cake produced from the process is a solid waste,
and has the potential for being a hazardous waste. However,
the TCLP results for the demonstration showed that the filter
cake produced did not exhibit a hazardous waste
characteristic and would not be a RCRA hazardous waste on
that basis. Many of the potential uses of the EPOC
microfiltration technology would be regulated by RCRA,
either because the feed stream would qualify as a RCRA
hazardous waste (making all effluent streams hazardous
wastes by the derived-from rule), or the filter cake or other
11
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effluent could exhibit a characteristic making it a hazardous
waste.
If a hazardous waste is treated or generated during treatment
with the EPOC microfiltration technology, the responsible
party must obtain an EPA generator identification number
and comply with accumulation and storage requirements for
generators under Title 40, Code of Federal Regulations
(CFR) Part 262 or have a RCRA permit or interim status.
A hazardous waste manifest must accompany any off-site
transportation of the hazardous waste, and transport must
comply with Federal Department of Transportation (DOT)
hazardous waste transport regulations. Any TSD facility
receiving the waste must also be permitted and in
compliance with RCRA standards.
The RCRA land disposal restrictions (40 CFR Part 268)
require that certain hazardous wastes receive treatment after
removal from a contaminated site and prior to land disposal,
unless a variance is granted. The microfiltration treatment
may allow for disposal of the liquid effluent from the
process as non-hazardous. This will require evaluation on a
case by case basis. The filter cake solids from the
microfiltration process may be restricted from land disposal
and require further treatment prior to disposal. If necessary,
stabilization/solidification may be used to further reduce the
mobility of contaminants in the filter cake to below the
applicable treatment standard limits. Other treatments may
be appropriate depending on the original waste contaminants
and the treatment chemicals used.
3.63.1 Clean Water Act
The Clean Water Act regulates discharges to surface water
through the National Pollutant Discharge Elimination System
(NPDES) regulations. These regulations require point-source
discharges of wastewater to meet established permit limits or
water quality standards. The EPOC microfiltration process
produces a treated liquid effluent that may be regulated
under the CWA if it is to be discharged either directly or to
a POTW. If the process effluent were discharged to a
surface water body, a NPDES permit indicating maximum
levels of specific parameters would be required. For
example, the Iron Mountain Mine AMD would probably be
required to meet a pH range of at least 6 to 9.
3.6.2.2 Safe Drinking Water Act
The Safe Drinking Water Act (SDWA) establishes primary
and secondary national drinking water standards. These
standards consist of Maximum Contaminant Levels (MCLs),
MCL goals (MCLGs), and aesthetic standards. MCLs may
be applicable and relevant where either surface or
groundwater may be used for drinking water. Depending on
the disposal options for the treated water from the EPOC
microfiltration process, the process effluent (permeate) may
have to meet strict guidelines for the amounts of some metal
species and water quality parameters.
3.62.3 Clean Air Act
The Clean Air Act (CAA) establishes primary and secondary
ambient air quality standards for protection of public health,
and emission limitations for certain hazardous air pollutants.
In most applications no emissions would be expected from
the EPOC process; therefore, the CAA would not be
applicable. In situations where electrical power to the
process equipment may be supplied by fuel-burning
generators, use of these generators may be regulated by the
CAA. However, State and local standards for diesel exhaust,
as well as for nuisance dusts, would be likely to be more
stringent, considering the probable size of such equipment
3.6.2.4 The Occupational Safety and Health Act
The Occupational Safety and Health Act (OSHA) covers the
safety of employees in the workplace. OSHA regulations
cover the selection and use of engineering controls, safe
work practices and use of personal protective equipment at
hazardous waste sites. OSHA regulations would cover the
use of the EPOC microfiltration technology whether the use
occurs at a hazardous waste site or at an ordinary workplace,
such as a manufacturing facility. OSHA regulations cover
the allowable exposures of workers to chemical hazards,
noise, and thermal and electrical conditions regardless of the
place the work is occurring. OSHA rules require that
training in hazardous waste handling practices be given to all
employees who work on hazardous waste sites.
Specifically, work with the EPOC process would certainly
require protective measures for spills and leaks of acid and
alkali such as the acid mine drainage or the precipitating
bases. Protection against dust could also be necessary.
3.63 State And Local Regulations
Meeting Applicable or Relevant and Appropriate
Requirements (ARARs) may require compliance with State
and local law that are more stringent than Federal standards
or that may be the controlling standards in the case of non-
CERCLA treatment activities. For use of the EPOC
microfiltration technology, State and local water quality
standards may be the most significant requirements. Water
discharge standards can be set based on the use of the water,
a site risk assessment, and/or currently available treatment
12
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options. When the Old No. 8 acid mine drainage was
treated with caustic or lime, effluent concentrations achieved
through the EPOC treatment system of all metals of concern
were below or close to 1 mg/L except for aluminum, and
well below 0.1 mg/L for all heavy metals.
3.7 Manpower Requirements
Although the developer believes that the EPOC
microfiltration system can be operated with a minimum of
oversight, such was not the case during the demonstration
tests, at least for operation of the EXXPRESS dewatering
unit. As noted in this report, considerable effort was required
to adjust cycling and pressure for the EXXPRESS unit and
to remove plugs of filter cake to the point where any usable
information could be generated. During these tests, two
professional staff members were involved almost constantly
in these efforts. This would not be practical in a
remediation or process application, but it is not clear whether
the problems were due to equipment inadequacies,
unanticipated and unexplained characteristics of the sludge,
or a result of the means of precipitating the metals as
hydroxides.
Addition of alkali to precipitate the metals as hydroxides in
the reactor vessel also required more than the expected
attention since overdosing with precipitant produced pH
spikes that were accompanied by elevated aluminum
concentrations in the permeate. A more sophisticated pH-
controlled alkali feed system and improved agitation might
reduce the attention required in this area.
3.8 Testing Requirements
It would at first appear that only minimal testing of the feed
wastewater stream would be required to develop appropriate
processing conditions and precipitant addition rates.
However, the difficulties with pH control during the
demonstration, even after laboratory and optimization testing
with the two wastewaters at the site, suggest that additional
information may be needed. For example, it may not be
sufficient to add a calculated amount of alkali to precipitate
the metals. As noted, alkalinity may play a part in the
effectiveness of precipitation. In addition, the physical
character of the precipitate may affect the efficiency of
separation in the EXXFLOW and, particularly, dewatering
in the EXXPRESS. Although the developer indicated that
the particles must be larger than 0.1 pm to be removed in
the EXXFLOW and smaller than 1 pm so that they do not
plug or blind the EXXPRESS membrane, no tests were
identified or run to determine the actual particle size, other
than laboratory and field shakedown tests of the system.
13
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Section 4
Economic Analysis
4.1 Introduction
The primary purpose of this economic analysis is to estimate
costs (excluding profit) for commercial-scak treatment using
the EPOC microfiltration system. With realistic costs and a
knowledge of the basis for their determination, it should be
possible to estimate the economics for operating similar-
sized systems at other sites utilizing scale-up cost formulas.
Among such scale-up cost formulas available in the literature
for chemical process plant equipment is the "six-tenths rule"
II].
This economic analysis is based on assumptions and costs
provided by EPOC, on results and experiences from this
SITE demonstration, and on best engineering judgement. The
results are presented in sufficient detail so that, if the reader
disagrees with any of the assumptions made, the reader can
draw his/her own conclusions using his/her own
assumptions.
Although the SITE demonstration tested the EXXFLOW
microfiltration system and the EXXPRESS automatic sludge
dewatering system as an integrated unit, the results showed
that the EXXPRESS module was ineffective in dewatering
the concentrate from the EXXFLOW module, and
consequently did not meet the developer's claims. Therefore,
for purposes of this cost analysis, an alternate dewatering
system was considered for both pilot-scale and full-scale
systems. The consequences of not dewatering the concentrate
were also investigated for the pilot-scale unit to determine
how much of an impact this step would have on costs.
Although the EXXFLOW pilot-scale unit was operated at a
permeate flow rate of 3 gpm during the SITE demonstration,
it was assumed that it could achieve its design permeate
flow rate of 7 gpm. It was also assumed that the
performance of full-scale equipment would be similar to that
demonstrated with the pilot-scale unit
Certain actual or potential costs were omitted because site-
specific engineering aspects beyond the scope of this SITE
project would be required Certain furfctions are assumed to
be the obligation of the responsible party or site owner and
also were not included in the estimates.
Cost figures provided here are "order-of-magnitude"
estimates, generally +50%/-30%, and are representative of
charges typically assessed to the client by the vendor
exclusive of profit
4.2 Conclusions
Dewatering the concentrate from the EXXFLOW
microfiltration unit before disposal decreases costs for the
pilot-scale unit - $33/1000 L ($125/1000 gal) without
dewatering, compared to $27/1000 L ($103/1000 gal)
with dewatering.
For the pilot-scale unit, labor, consumables and supplies,
and effluent treatment and disposal costs account for
about 80% of overall cleanup costs. Site preparation, and
startup and fixed costs are the next largest cost
contributors. Since they are one-time charges, their effect
on a percentage basis, could be reduced for longer
duration projects. Annualized equipment costs, utilities,
and residuals disposal from the dewatering system
contribute the least
Treatment costs for the 190 L/min (50 gpm) full-scale
unit with dewatering ($12/1000 L, $47/1000 gal) are
about half of what they are for the pilot-scale unit thus
demonstrating the cost advantages of scale-up.
For the full-scale unit start-up and fixed costs, labor,
consumables and supplies, and effluent treatment and
disposal account for close to 90% of total costs.
Comparing cost percentages to the pilot-scale unit with
14
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dewatering, reductions in labor, and effluent treatment
and disposal costs are more than offset by increases in
consumables and supplies. Labor shows the largest
decrease because manpower requirements are not affected
by unit size but rather by the duration of treatment
Residual disposal costs also double due to scale-up, but
again this is more than offset by reductions in other cost
categories. Site preparation, annualized equipment costs,
and utilities contribute the least
Although they were not included here, accounting for
permitting and regulatory activities, analytical
requirements, facility modification, repair and
replacement, and demobilization could significantly
increase costs.
4.3 Issues and Assumptions
This section summarizes the major issues and assumptions
used to evaluate the cost of EPOC's microfUtration system.
In general, assumptions are based on information provided
by EPOC.
4.3.1 System Design and Performance Factors
As stated earlier, the SITE demonstration used an
EXXFLOW microfiltration module in tandem with an
EXXPRESS automatic sludge dewatering system. Although
this system was designed to produce permeate at a rate of 7
gpm, it was operated at 3 gpm during the SITE
demonstration. Therefore, the estimates for both the 7 gpm
pilot-scale and the 50 gpm full-scale units used proportioned
flow rates based on results of this SITE demonstration, as
shown in the table below:
Stream
Unit Size - Permeate Flow Rate
3 gpm 7 gpm 50 gpm
Influent
Concentrate
Dewater
Recycle
50 gpm
47 gpm
1.4 gpm
46 gpm
50 gpm
43 gpm
32 gpm
40 gpm
833 gpm
783 gpm
23 gpm
760 gpm
Details of the calculations used to derive these numbers can
be found under the "Effluent Treatment and Disposal" costs
section. For this analysis, it was assumed that performance.
in terms of percent reduction, for all three units was similar
to that tested.
Casts for the pilot-scale unit were estimated with and
without dewatering of the concentrate stream. Demonstration
results showed that the filter cake product from the
EXXPRESS unit passed the TCLP test and would be
considered non-hazardous for disposal purposes. Although
the concentrate stream was not specifically tested during the
demonstration, it was assumed that it too would pass the
TCLP test and could be considered non-hazardous as well.
For the scenario without dewatering, two further cases were
considered. First, it was assumed mat the concentrate stream
from the EXXFLOW unit, being non-hazardous, could be
disposed of on-site. For this case, there would either be no
or very little effluent disposal costs. Although this is a very
real possibility at the Iron Mountain Mine Superfund Site, it
would be a rather rare occurrence at other cleanup sites.
Therefore, no costs were included for this case. In a second
case it was assumed that disposal of the concentrate stream
would be required off-site. Since this a more realistic
possibility, this cost was included in this analysis.
Tin; dewatering system selected assumed that solids content
couild be increased from 1.2% to 20%. The residual filter
cake produced was again assumed to be non-hazardous and
coutld be disposed of off-site at a nominal cost
4.3.2 System Operating Requirements
This analysis assumed that the waste being treated was
similar to that tested during the demonstration. The alkali
chemical used was assumed to be 50% caustic. Flow rates,
the amount of recycle, the type and concentration of
contaminants, the type and amount of alkali used, the type
and size of dewatering equipment used, if any, will all affect
system operation and, consequently, costs.
This analysis assumed a cleanup duration of one year. EPOC
projected that one operator could fulfill all operational duties
in two hours during a normal 8-hr shift. The rest of the time
he/she would be available for other non-EPOC process
related tasks. Since the equipment was assumed to operate
24-hr/day, 3 shifts per day, 7 days per week, for 50 weeks
per year, labor costs were based on 3 operators being
required. EPOC indicated that larger flow units could be
built by essentially adding additional microfiltration modules
without increasing the labor requirements.
4.33 Utilization Rates and Maintenance
Schedules
A 90% on-line stream factor was used for costing. Although
this was not demonstrated, EPOC feels that this is realistic
if design and operational modifications were done and
15
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sufficient time for shakedown testing were allowed. They
base their contention on prior experience with equipment that
is installed and that has been operating for several years in
the field. Scheduled maintenance was assumed to be
performed during the regular shift
43.4 Financial Assumptions
Annualized equipment costs are based on a 15-year life. 6%
simple interest rate, and a salvage value of 10% of the
original equipment cost The time value of money was not
accounted for.
The following is a list of additional assumptions used in this
study:
- Access to the site is readily available.
- Utilities (electricity, water, sewer hookup,
telephone, etc.) are easily accessible.
- The permeate stream will not require any
further treatment
- There are no wastewater pretreatment
requirements.
4.4 Basis For Economic Analysis
In order to compare the cost-effectiveness of technologies in
the SITE program, EPA breaks down costs into the 12
categories shown in Tables 4-1 and 4-2 using the
assumptions for each cost factor described in more detail
below.
4.4.1 Site Preparation Costs
The amount of preliminary preparation will depend on the
site and is assumed to be performed by the responsible party
(or site owner). Site preparation responsibilities include site
design and layout, surveys and site logistics, legal searches,
access' rights and roads, and preparations for support
facilities, decontamination facilities, utility connections, and
auxiliary buildings. These preparation activities are assumed
to be completed in 500 staff hours. At a labor rate of $50/hr,
this would equal $25,000.
Although these were not considerations for this SITE
demonstration, other significant costs associated with site
preparation may include well drilling, preparation and
development, as well as buying and installing a groundwater
or surface-water pump and associated plumbing, especially
if the equipment will be located a considerable distance
away from the well. Based on experience from previous
SITE demonstrations, the cost to drill, prepare and develop
a well was assumed to be $5,000. It was assumed that only
one well was necessary to provide the required flow rate.
regardless of the size of the unit used and that no holding
tank was necessary.
The size of the pump also would depend on the size of the
treatment system assumed. The pilot-scale 7 gpm unit would
probably require a 1/4 HP, 10 gpm centrifugal pump, costing
about $1,000, while the full-scale 50 gpm unit would
probably require a 2 HP, 75 gpm centrifugal pump costing
about $3,500, based on the "six-tenths scale-up rule".
Access roads and other site-specific auxiliary structures
which may be necessary, such as concrete pads or a
building, can be very expensive but are not included here.
Therefore, the total site preparation costs for a pilot-scale or
full-scale unit would be between $30,000 and $35.000 as
shown in Tables 4-1 and 4-2.
4.4.2 Permitting and Regulatory Costs
Permitting and regulatory costs are generally the obligation
of the responsible party (or site owner). These costs may
include actual permit costs, system health and safety
monitoring requirements, and the development of monitoring
and analytical protocols. Permitting and regulatory costs can
vary greatly because they are site- and waste-specific. No
permitting costs are included in this analysis; however,
depending on the treatment site, this can be a significant
factor since permitting activities are project dependent.
4.43 Equipment Costs
The EPOC Microfiltration System assumed for this
economic analysis includes a reaction tank, the EXXFLOW
microfiltration unit recirculation pump and associated
plumbing, instrumentation, monitoring and control
equipment The size of the reaction tank would be dependent
on the size of the EXXFLOW unit and on the alkali used
due to different reaction times with different chemicals. It
would also include an alkali feed system with a feedback
control loop to maintain a set pH, a level control, and a
mechanical stirrer, the size of which again would be
dependent on the size of the reaction tank and the alkali
used.
The cost of rental equipment used in this SITE demonstra-
tion such as storage tanks, office trailers, pickup trucks for
transporting supplies, diesel generators, air compressors, and
forklifts are not included.
16
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Tabfe 4-1. EstfaMM Costs tar 7 spa PHot-Scate U«M
COST COMPONENT
widxwt
die watering
with
dewjtering
1. Site Preparation
2. Permitting & Regulatory
3.' Equipment (annualized)
4. Startup & Fixed
i. Labor
6. Consumables & Supplies
7. Utilities
8. Effluent Treatment & Disposal:
* Dewatering System
. Capital (annoaHzed)
-O&M
Total
9. Residuals/Waste Shipping,
Handling and Transport
10. Analytical
11. Facility Modification. Repair &
Replacement
12. Demobilization
31.000
7.80
314)00
8,600
9.45
6300
256SQ
84JXIO
101,750
3.W5
145j635
145.635
1.63
6.45
21.12
25.59
0.79
36.62
6300
25.650
84X100
101.750
3,145
635
3.485
63300
67,420
1.98
7.82
25.60
31.02
0.96
20.55
2.62
TOTALS
VlOOOgal
S/1000L
397480
125
33
100
328,065
103
27
100
TaM* 4-1. Estimated Corti tar 5« gfm FafrScate Uatt
Co* Component
1. Site Preparation
2. Permitting & Regulatory
3. Equipment (iimnaHwd)
4. StartnpAFlxed
5. Labor
6. Consumables & Supplies
7. Utilities
8. Effluent Treatment & Disposal:
* Dewatering System
- Capital (annualized)
- O 4 M
Total
9. Residuals/Waste Shipping, Handling and Transport
10. Analytical
11. Facility Modification. Repair ft Replacement
12. Demobilization
33300
17.400
91350
84,000
690500
6775
4335
12,400
73.450
90385
61.780
3.11
1.62
8.49
7.81
64.20
0.63
8.40
5.74
TOTALS
VlOOOgaJ
V1000L
1,076,090 100
47
12
17
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EPOC estimates the cost of a 7 gpm pilot-scale
microfiltralion unit, similar to that used in this SITE
demonstration, to be about $70,000. A full-scale 50 gpm unit
is estimated to cost $187,500. These costs do not appear to
follow the so-called "six-tenths rule". Hence, the cost for the
full-scale unit appears to be relatively low when compared
to the cost of the pilot-scale unit
The annualized equipment cost is calculated using the
following equation and financial assumptions discussed
earlier:
id + if
Capital Recovery = (V - VJ ------------
Where V = the cost of the original equipment
V, « the salvage value of the equipment,
n s the equipment life (15 years),
i s the annual interest rate (6%).
4.4.4 Startup and Fixed Costs
EPOC's EXXFLOW microfUtration units can be mobile,
such as the 7 gpm pilot-scale unit used in the SITE
demonstration, or fixed, such as the 50 gpm full-scale unit
Transportation costs are only charged to the client for one
direction of travel and are usually included with mobilization
rather than demobilization costs. Transportation costs are
variable and dependent on site location as well as on
applicable oversize/overweight load permits, which vary
from state to state. For purposes of mis cost estimate,
trucking charges will be based on a 40,000 Ib. 48 ft long, 8
ft high legal load and will assume that a driver is included.
One tractor/trailer is required for the 7 gpm pilot-scale unit,
while the 50 gpm full-scale unit requires three such
tractor/trailers. Assuming that it will cost $1.65/mile, a 1,000
mile trip would cost $1,650 for the 7 gpm pilot-scale unit
and $4,950 for the 50 gpm full-scale unit
Assembly consists of unloading the EPOC EXXFLOW
microfiltration system from the trailers, setting up the system
in place, installing instrumentation, hooking up utilities, and
other miscellaneous installation tasks. Assembly costs are
estimated to be $5,000 for the 7 gpm pilot-scale unit and
$15,000 for the SO gpm full-scale unit
EPOC estimates that waste-specific testing of the system
would require 2 weeks prior to the commencement of
treatment This would involve checking out and
troubleshooting each of the systems individually for the
particular waste to be treated. Two workers would be
required for 12 hr/day, 5 day/wk. Start-up costs are assumed
to be limited to labor charges at a rate of 540/nr, excluding
travel and per diem, for a total of $9,600.
Working capital is assumed to be based on the amount of
money currently invested in maintaining a one-month
inventory of supplies and consumables. The predominant
item here is assumed to be treatment chemicals, i.e.. 50%
NaOH, at a cost of $30/1000 gal of waste (see Consumables
and Supplies). For the pilot-scale unit the associated cost
would be $8,100 (7 gal/min x 60 min/hr x 24 hr/day x 30
days x 0.9 x $0.03/gal) and $58,320 for the full-scale unit
Insurance and taxes are usually approximately 1% and 2%
to 4% of the equipment capital costs, respectively. The cost
of insurance for a hazardous waste process can be several
times more than this. For purposes of this estimate,
insurance and taxes together are assumed to be 10% of the
annualized equipment capital costs [3].
The cost for health monitoring programs has not been
included here. Depending on the site and the location of the
system, local authorities may impose specific guidelines for
monitoring programs, the stringency and frequency of which
may have a significant impact on project costs.
A contingency cost of 10% of the annualized equipment
capital costs is allowed for any unforeseen or unpredictable
cost conditions, such as strikes, floods, and price variations
[3,4].
The total for start-up and other fixed costs would then be the
sum of all of the sub-categories discussed above, i.e..
$25,650 for the 7 gpm pilot-scale unit and $91.350 for the
50 gpm full-scale unit
4.4.5 Labor
EPOC assumed that after start-up, system operation would
be automatic, and require only 2 hr/shift of operator attention
to perform routine tasks such as monitoring, routine
maintenance, and documentation activities. They assumed a
labor rate of $40/hr including overhead and administrative
costs, but excluding per diem, travel, and rental car expenses
that might be needed if EPOC personnel were to be used. It
is the developer's intention to hire and train local people so
that they do not incur these additional expenses. The cost
and time to hire and train local personnel, which may be
substantial, is not included.
The annual cost of labor for both size units is calculated as:
2 hr/shift x 3 shifts/day x 7 days/wk x 50 wk/yr x $40/hr =
$84,000.
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4.4.6 Consumables and Supplies
Consumables required for the operation of the EPOC
microfiltration system are limited to treatment, membrane-
forming, and cleaning chemicals. The cost of membrane-
forming and cleaning chemicals are inconsequential in
comparison to treatment chemicals.
For purposes of this economic analysis, caustic soda (NaOH)
is assumed to have been used at a dosage rate of 0.15 Ib (69
gm) of 50% NaOH per gallon of waste. At $0.20/lb of 50%
NaOH. it would cost about $30/1000 gal of waste treated or
$95250 for the pilot-scale unit and $680,400 for the full
scale unit Further cost reductions may be realized if
treatment chemicals are bought in bulk quantities. In that
case, however, provisions for proper storage and handling
must be accounted for.
Based on data from previous operations over a period that
reflects operating conditions similar to those experienced
during the demonstration tests, the costs for spare parts,
including spare microfilters for the EXXFLOW unit,
office/general supplies, pump seals, fuses, valve o-rings, and
diaphragms are estimated at $2,000/yr for the pilot-scale unit
and S6.000/yr for the full-scale unit
Health and safety gear, which includes hard hats, safety
glasses, respirators and cartridges, protective clothing,
gloves, safety boots, etc., are estimated to cost
Sl,500/person.
4.4.7 Utilities
The electricity required for the EXXFLOW microfiltration
system is estimated by EPOC to be 5.2 kW for the pilot-
scale unit and 11.2 kW for the full-scale unit Assuming no
monthly charge and a flat rate of $0.08/kWhr for electricity,
it would cost $3,145 to operate the pilot-scale unit for a year
and $6,775 to run the full-scale unit, both at a 90% on-line
stream factor.
4.4.8 Effluent Treatment and Disposal
Two process streams are produced by the EXXFLOW
microfiltration system. The permeate is considered to be
essentially free of contaminants and is assumed to meet
standards appropriate for discharge to a POTW or the local
sewer system, at a cost of $0.20/1000 gal. This corresponds
to 3.175 million gallons of treated water discharged per year
for the pilot-scale unit and 22.68 million gallons for the full-
scale unit The associated costs would be $635 for the pilot-
scale unit and $4,535 for the full-scale unit
The concentrate is the reduced volume portion of the initial
wastestream with the enriched contaminants that would
require further treatment Based on SITE demonstration test
results with caustic soda, 252 Ib of filter cake, of which
12.5%, or 31.5 Ib (252 Ib x 0.125) is solids, were produced
from the EXXPRESS unit This corresponded to an inlet
stream of 1.2% solids or 2,625 Ib (31.5 Ib / 0.012) of
concentrate entering the EXXPRESS unit in 240 min. If the
density is assumed to be 8 Ib/gal, this equals 1.37 gpm
(2625 lb/8 Ib/gal/240 min). A flow of 1.37 gpm represents
46% of the permeate flow rate of 3 gpm. Therefore, a pilot-
scale unit operating at a permeate flow rate of 7 gpm would
generate 3.2 gpm of concentrate, while a full-scale unit
operating at a permeate flow rate of 50 gpm would produce
22.7 gpm of concentrate with 1.2% solids.
If the concentrate were not dewatered, it could be disposed
of off-site as non-hazardous waste at a cost of about
$0.10/gal. This would add an additional $145,000 (3.2
gal/min x 60 min/hr x 24 hr/day x 7 day/wk x 50 wk/yr x
0.9 x $0.10/gal) to effluent treatment and disposal costs for
the pilot-scale unit
Alternatively, a dewatering system would concentrate the
contaminants into a reduced volume filter cake product
(estimated at 20% solids). Water from the dewatering step
could be recycled, thereby minimizing costs for subsequent
transportation and/or ultimate disposal of the filter cake. To
highlight how much of a contribution this dewatering step
would reduce the overall technology cost, the pilot-scale unit
cost estimate includes costs with and without this dewatering
step. The full-scale unit costs were developed including
dewatering.
Plate and frame pressure filtration was assumed to be used
for the dewatering step. Components of the system include
filter plates, filter cloth, hydraulic pumps, pneumatic booster
pumps, control panel, connector pipes, and support platform.
Installation, engineering, and contingency costs were added
to the equipment costs. Installation costs were estimated at
35% of the equipment costs, while contingency and
engineering fees were estimated to be 15% of the equipment
and installation costs. Based on vendor quotes, capital costs,
in 1989 dollars, were $33,300 for a 3.2 gpm system (for the
7 gpm pilot-scale unit), and $118,900 for a 22.7 gpm system
(for the 50 gpm full-scale unit). These costs were corrected
to 1993 dollars using the annual average construction cost
index as published in Engineering News-Record (ENR)
magazine. It was 4615 for 1989 and 5210 for 1993, resulting
in an index ratio of 1.13. Therefore, the indexed capital costs
are $37,600 ($33,300 x 1.13) for the 3.2 gpm system, and
$134,000 ($118,900 x 1.13) for the 22.8 gpm system in 1993
dollars.
19
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The annualized capital costs for the dewatering system are
calculated in the same way, using the same assumptions as
for the EXXFLOW system discussed previously. For the 7
gpm pilot-scale unit this is $3,485 and for the 50 gpm full-
scale unit, $12,400.
Operating and maintenance costs were based on estimated
electricity usage, maintenance, labor, taxes and insurance.
The electricity usage and costs were based on a usage rate
of 0.5 kWhr/1000 gal and $0.08/kWhr, and lighting and
control energy costs were estimated at $l,000/yr.
Maintenance was approximated at 4% of the capital cost
Taxes and insurance were approximated at 2% of the capital
cost The labor cost for the plate and frame pressure
filtration system was approximated at $31,200 per man-year
at thirty minutes per cycle per filter press. In 1989 dollars,
the operating and maintenance cost for the 7 gpm pilot-scale
unit is estimated to be $56,000 and $65,000 for the 50 gpm
full-scale unit The corresponding indexed costs in 1993
dollars are $63300 and $73,450, respectively.
An ancillary consideration when using a dewatering system
is the additional land area that would be required. It is
estimated that approximately 2,500 ft2 would be required,
irrespective of the size of the dewatering system used. No
costs for this land were included in this estimate.
4.4.9 Residuals/Waste Shipping, Handling and
Transport Costs
Waste disposal includes storage, transportation and treatment
costs and are assumed to be the obligation of the responsible
party (or site owner). The only residuals or solid wastes
generated from this process are the filter cake and
miscellaneous items (e.g., used modules, protective gear,
etc.).
Since the filter cake generated by the microfUtration system
passed the TCLP test, it is considered to be a non-hazardous
waste that can be landfilled at a cost of $0.10/gal, assuming
there is no free liquid. For the pilot-scale unit, a concentrate
flow rate of 3.2 gpm with 1.2% solids corresponds to 0.038
gal/min of solids being dewatered (3.2 gal/min x 0.012). If
the filter cake is 20% solids, then this equals 0.19 gaVmin of
filter cake being generated (0.038 gal/min/ 0.2). The yearly
disposal cost for the filter cake would then be $8,600 (0.19
gaVmin x 60 min/hr x 24 hr/day x 7 day/wk x 50 wk/yr x
0.9 x SO.lO/gal). Similarly, for the full-scale unit yearly
filter cake disposal costs would be $61,780.
If, however, the filter cake is hazardous, disposal costs could
increase substantially.
4.4.10 Analytical Costs
Standard operating procedures do not require planned
sampling and analytical activities. Periodic spot checks may
be executed at EPOC's discretion to verify that equipment
is performing properly and that cleanup criteria are being
met, but costs incurred for these actions are not assessed to
the client The client may elect or be required by local
authorities to initiate a sampling and analytical program at
their own expense. Therefore, analytical costs associated
with environmental monitoring have not been included in
this estimate. Specific sampling and monitoring requirements
could contribute significantly to the cost of the project.
4.4.11 Facility Modification, Repair and
Replacement
Since site preparation costs were assumed to be borne by the
responsible party (or site owner), any modification, repair.
or replacement to the site was also assumed to be done by
the responsible party (or site owner).
Maintenance costs consist of labor and materials and will
vary with the nature of the waste and the performance of the
equipment Maintenance labor has previously been accounted
for under "Labor Costs". The annual cost of maintenance
materials is assumed to be 3% of equipment capital costs
and includes provisions for design adjustments and
equipment replacement as needed. This has already been
accounted for in the consumables and supplies cost category.
4.4.12 Demobilization Costs
Site demobilization will include shutdown of the operation,
final decontamination and removal of equipment, site
cleanup and restoration, permanent storage costs, and site
security. Any other requirements will vary depending on the
future use of the site and are assumed to be the obligation of
the responsible party. No costs have been included for
demobilization.
4.5 Results
Table 4-1 shows the total annual cleanup cost for a 7 gpm
pilot-scale system to be $327,000 ($27/1000 L) with
dewatering and $397,000 ($33/1000 L) without dewatering.
This is a $70,000 savings and clearly shows the advantages
of dewatering the concentrate from the EXXFLOW
micro-filtration unit before disposal. Not surprisingly, the
largest cost component without dewatering is effluent
treatment and disposal (37%), foUowed by consumables and
20
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supplies (26%), and labor (21%). With dewatering, the
largest cost component becomes consumables and supplies
(31%), followed by labor (27%), and effluent treatment and
disposal (21%). In either case, these three cost categories;
labor, consumables and supplies, and effluent treatment and
disposal, accounted for 75-85% of costs.
The next biggest cost contributors were site preparation (8 to
9.5%), and startup and fixed costs (6.5 to 8%). It should be
remembered that this cost estimate is based on a one year
remediation. Since these are one-time charges, Iheir respective
percentage contribution to costs as well as the overall $/L
cost will go down as the length of the project increases.
Annualized capital equipment costs, and utilities each
contributed less than 2%. Residuals disposal from the
dewatering system accounted for an additional 2.6%.
Considering the fact that effluent treatment and disposal costs
were almost cut in half by dewatering, this is not a significant
contribution.
Table 4-2 shows the total annual cleanup cost for a 50 gpm
full-scale system to be $1,100,000 ($12.50/1000 L),
including concentrate dewatering. On a $/L basis, this is a
two-fold reduction from the corresponding pilot-scale system
and clearly shows the advantage of large scale operation.
As in the 7 gpm pilot-scale unit with dewatering, the largest
cost component is consumables and supplies (64%). Startup
and fixed costs, effluent treatment and disposal, and labor are
the next largest cost categories, each contributing about 8 to
8.5%. On a percentage basis, startup and fixed costs stayed
about the same compared to the 7 gpm pilot-scale unit with
dewatering. However, effluent treatment and disposal, and
labor were cut by more than half. In fact, the cost category
showing the largest reduction is labor, from 26% to 8%. This
is because of the assumption that the same number of people
would be required to operate the system regardless of size.
Only the remediation time seems to affect labor costs. These
four cost components; startup and fixed costs, labor,
consumables and supplies, and effluent treatment and
disposal, accounted for close to 90% of the total.
The cost of residuals disposal increased from about 2.6% for
the pilot-scale unit to 5.74% for the full-scale unit because of
the increase in equipment size; i.e., processing more waste
produces more filter cake that must be dewatered and
eventually disposed of. However, this was more than made up
by the reduction in effluent treatment and disposal costs. Site
preparation, annualized capital equipment costs, and utilities
each contributed 3% or less.
This analysis did not include costs for 4 out of the 12
categories, specifically, costs associated with permitting and
regulatory activities, analytical requirements, facility
modification, repair and replacement, and demobilization.
Accounting for these factors could significantly increase
costs.
4.6 Development of a 700 GPM Microfiltration
System
EPOC has developed a Microfiltration System that is able to
treat .2,700 L/min, (700 gpm) of contaminated groundwater
with a total metal concentration of 5 mg/L at pH 5. This full-
scale unit is designed to be operated as a fixed facility. The
vendor has provided the following costs for this system.
Major equipment costs are estimated to be $1,350,000.
Installation costs include transportation, assembly, and
shakedown testing of the individual systems. Installation
costs are estimated to be $50,000. Waste specific equipment
testing is estimated to require 3 workers for 12 hr/day, 5
day/wk, for 3 weeks. It is assumed that system operations
will be automated, requiring only one system operator to run
the unit. It is assumed that a maintenance operator will also
be required for 12 hr/day. Spare parts are estimated to cost
$15,000 per year. Assuming that the treatment chemical is
50% NaOH, it is estimated that 250 Ib/day of NaOH will be
required. The electricity requirements for this unit is
estimated to be 59.7 kW, 460 V, 3 phase.
The cost of operating this 700 gpm unit to treat contaminated
groundwater with a heavy metal concentration of 5 mg/L at
pH 5 is approximately $2.60/1000 gal (if only the costs
calculated in this report are considered). This is an
approximate estimate based on a total treatment time of 12
months, and using 50% NaOH as the treatment chemical.
The cost is significantly lower than the treatment costs of the
7 and 50 gpm units treating acid mine drainage (total metal
concentration of 3,000 mg/L at pH 2.3) and relates to the size
of the unit and the type of waste being treated.
References
1. Perry, R.H., Chilton, C.H., Chemical Engineer's
Handbook; Fifth Ed., McGraw-Hill, Inc. New York,
1973, pg. 25-16.
2. Douglas, J.M., Conceptual Design of Chemical Process;
McGraw-Hill, Inc. New York, 1988.
3. Peters, M.S., Timmerhaus, K.D., Plant Design and
Economics for Chemical Engineers; Third Ed.,
McGraw-Hill, Inc. New York, 1980.
4. Garrett, D.E., Chemical Engineering Economics; Van
Nostrand Reinhold New York, 1989.
21
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Appendix A
Process Description
A.I Introduction
The EPOC Micro-filtration Process is based upon the ability
of a participate to be retained by a semi-permeable
membrane. The physical structure of a membrane is very
diverse ranging from solid structures, such as inorganic and
polymeric membranes, to transitory or dynamic membranes
that are temporarily formed. The EPOC Process may be
viewed in three steps:
1) Precipitation of metals by adding alkali.
2) Concentration of the precipitates by the EXXFLOW
microfiltration unit and the production of product
water (permeate).
3) Separation and dewatering of the EXXFLOW
concentrate in the EXXPRESS unit to produce a
semi-dry filter cake.
The EPOC microfiltration process is a relativity simple
process design consisting of a few subassemblies which
make up the entire process. These subassemblies are the
reaction tank, the EXXFLOW unit, the EXXPRESS unit, and
the filter cake dewatering system. Each of these
subassemblies is discussed in greater detail in the following
sections.
A2 The Reaction Tank
The chemical reaction to form particles which are large
enough to be filtered from the liquid waste stream is the first
step in the microfiltration process. Raw water enters the
reaction tank and is treated with the alkali of choice resulting
in the precipitation of the dissolved heavy metals. The
reaction tanks are typically constructed of hard plastics
which are inert to the waste stream and the harsh alkaline
conditions. The reaction tank used for the SITE
demonstration test was fitted with a dry chemical feeder
which controlled the dose rate of powdered alkali (such as
Ca(OH)2 or MgO). Tanks can also accommodate liquid
alkali (50% NaOH solution) with the dose rate being
controlled by a metering pump. The dose rate of chemical
is set to match the feed rate of the raw water so that the
desired pH is maintained in the reaction tank. The reaction
tank is set on level control such that the raw feed rate can be
controlled entering the tank. During normal operation, the
reaction tank is under steady state and the level in the
reaction tank is maintained.
The reaction tank is fitted with a mechanical stirrer that
provides agitation to enhance the chemical reaction and
prevent excessive solids from settling in the bottom of the
tank. Different treatment chemicals exhibit different settling
characteristics and, therefore, the stirrer plays an important
role in preventing clumping and caking within the reaction
tank. Stirring also prevents clumping of solid treatment
chemical as it hits the liquid surface in the tank.
Reaction tanks are sized based upon the feed rate of raw
water and the flow rates which the EXXFLOW unit can
accommodate. The size of the reaction tank and the flow
rate of raw water will dictate the residence time for the
chemical reaction. The tank must be sized properly to allow
sufficient residence time for the precipitation of the heavy
metals from solution. For treatment chemicals that have
long reaction time, such as MgO, the tank must be large
enough to provide for a residence time in excess of two
hours. Treatment chemicals such as NaOH react instantly;
consequently, the tank can be much smaller.
A3 EXXFLOW Unit
The EXXFLOW unit is designed to concentrate the solids in
the waste stream (reject) and produce clean permeate. This
is accomplished thorough crossfiow microfiltration. In
crossflow filtration, the flow is directed parallel to the
surface of the membrane. The EXXFLOW crossflow
microfiltration process employs a curtain array of permeable
textile tubes, each about 1 in. in diameter. Resin manifolds
are cast onto each curtain end to form modules which are
connected to a pump for liquid inlet and to a back pressure
valve at the outlet Liquid feed to the EXXFLOW unit
22
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flows from the bottom of the reaction tank. By introducing
a controlled liquid flow into the tubes and regulating the
outlet pressure, suspended and colloidal matter in the liquid
forms a membrane layer on the internal surface of each tube.
The goal of a crossflow filtration application is not to trap
the components within the pore structure of the membrane,
as in unconventional filtration; rather, the large material is
temporarily retarded on the membrane and is then swept
clean by the crossflow action. Should the quantity or quality
of suspended matter in the feed liquid be insufficient or
inappropriate to form a membrane, a filter aid material is
added to the initial feed to form the membrane. Membranes
or filter layers of widely different characteristics can be
produced by using different pretreatment chemicals or
additives.
After membrane formation, the membrane at die liquid
surface is dynamic, being continually formed and swept
down the length of the tubes by the longitudinal flow of the
chemically-treated feed. This cleaning action prevents
particles from being trapped within the membrane's matrix
and thus substantially adds to its life. To become treated
product liquid, or permeate, the feed water filters radially
through the membrane layer and out of the textile tube walls
for collection. The solids removed from the permeate
become concentrated and are swept out of the tubes with the
remaining liquid, or concentrate. Figure A-l illustrates the
EXXFLOW operation.
A uniformly high quality permeate is achieved with the
EXXFLOW crossflow microfiltration process. Removal of
virtually all suspended solids down to about 0.1 um has been
demonstrated in laboratory and field trials. Other
experimental work indicates that the EXXFLOW unit can be
developed to produce a low pressure process that will also
reject high molecular weight dissolved solids.
A3.1 Dynamic Membrane Concept
The dynamic membrane which is formed on the inner wall
of the EXXFLOW tubes is the medium which performs the
separation of the permeate from the reject Suspended solids
contained in the feed water deposit on the inner surface of
the porous tubes at a rate which is a function of the fluid
flow rate and backpressure on the module. The deposit on
the inside of the tube wall is called the dynamic membrane.
During the formation of the dynamic membrane, the flow of
fluid through the tubes exerts a shear force on the deposited
solids that tends to entrain particles back into suspension.
After a short period of time, a steady state equilibrium is
established at which the deposition rate of solids equals the
erosion rate of the dynamic membrane. It is this dynamic
membrane that actually controls the dynamics of the
filtration process. Pores of the dynamic membrane are much
smaller than pores of the tubes. Suspended solids contained
in the feedwater are filtered by the dynamic membrane
ratheir than the tube itself. The function of the tube is to
support the dynamic membrane without allowing particles to
intrude into the tube matrices. At the same time the tube
must be very porous to minimize resistance to fluid flow.
Physical and chemical properties of the dynamic membrane
are also very important to the process. Like the support
tube, the dynamic membrane must have a low resistance to
the flow of the filtrate. It should be relatively non-cohesive
so that particles are easily re-entrained by the flow of fluid
past the membrane, thus minimizing membrane thickness.
By adding small quantities of various chemicals, the
characteristics of the dynamic membrane can be changed to
assist: in the filtration process.
A3.2 EXXFLOW Attributes
EXXFLOW crossflow microfiltration units are of modular
construction employing a number of manifolded curtains, or
modules. Modules are connected together either in parallel
or in series with each other, or any number of tubes within
a module can be similarly connected.
Two basic configurations of EXXFLOW units are available:
linear, where a number of curtain modules are suspended
with the tubes running parallel to the ground, and spiral,
where the modules are wound in a spiral with the tubes
parallel or perpendicular to the ground. Curtain modules
may also be suspended vertically or supported horizontally.
Other variants permit the curtain to be formed into
cartridges. Selection of the type of configuration depends on
the space requirement and the duty envisaged for the
EXXFLOW unit Figure A-2 shows a typical EXXFLOW
spiral filter module.
Ease of cleaning is an important feature of the EXXFLOW
crossflow microfiltration unit that distinguishes it from other
crossflow microfiltration systems. In most cases, cleaning
is simply a matter of momentarily stopping the feed,
resulting in tube collapse which causes the dynamic
membrane material to be dislodged from the tube wall and
flushed out with the reject flow. Depending on the
configuration of the tubular array, other cleaning systems can
be fitted, such as internal ball cleaning, reverse flow
flushing, water or air spray jet, or squeeze roller cleaning.
The EXXFLOW technology is based upon the highly
specialized woven textile tubular array as well as on the
formation and maintenance of dynamic membranes and
cleaning techniques. Currently, the cloth is available in two
basic designs, each of which can be woven in any length and
23
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run
uam
noau THRU TMC
fWMTI
FILTRATION TECHNOLOGY
7>
->.y
illllll
l. EXXFLOW Filtntioa Techaotojy and Flexible Tube
Module.
CBOSI SCCTMM
FILTRATE
CAKE KJILOUP
Figure A-2. EXXFLOW Crotsflow Microfilter.
FLCXIKX TEXTILE TUX
riLTHATE
Fifun A-3. EXXPRESS Aiaonaoe Sludft Dewiienng System.
24
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in any tube diameter desired for specific applications. The
porosity or permeability can be varied and post weaving
treatments applied to impart specific cloth characteristics.
While polyester yam is the standard material employed,
other materials can be used to influence results of the
EXXFLOW process depending on the permeate qualities
desired for specific feed liquids.
A.4 EXXPRESS Unit
Suspended solids in the water are concentrated by
recirculation through the EXXFLOW unit and then the slurry
is fed to the EXXPRESS unit Typical feed to the
EXXPRESS units are dilute slurries that contain between 2
and 5% solids. The EXXPRESS units dewater these streams
by operating a module in a "dead end" mode by closing a
valve at the reject end of the module. Typically, the
EXXPRESS microfiltration unit is hung parallel to the
ground and is traversed by a set of mechanical rollers. As
the concentrated waste stream enters the EXXPRESS
module, solids form a thin membrane layer on the internal
walls of the tubes similar to that of the EXXFLOW unit
The associated water in the waste stream permeates through
the membrane layer and escapes to the outside of the tubes
as filtrate. When the membrane layer reaches a controlled
thickness, the discharge valve is opened and the exterior of
the module is traversed by mechanical rollers. As the rollers
traverse the module, the cake that has formed on die wall of
the tubes is broken from the surface and flushed from the
module.
Water that permeates through (he tube wall during the
dewatering cycle is recycled to the EXXPRESS feed tank or
to the reaction tank. Generally, the water that permeates the
EXXPRESS unit needs to be recycled because the filtration
is not as effective as the EXXFLOW module.
A.4.1 EXXPRESS Operation
The primary objective of the EXXPRESS is to dewater the
concentrated feed entering the unit in normal dead end
filtration, the fluid is pushed through the membrane material
to remove entrained solids. In this mode, the flow is
perpendicular to the surface of the membrane and particles
are retained by becoming entrapped within the matrix of the
membrane. In the EXXPRESS unit, the dewatering occurs
at the tube walls with water flowing radially from the
direction of flow down the tube. The EXXPRESS operates
automatically in two cycles: load, and cake discharge. In the
load cycle, the discharge valve at the end of die module is
closed and fluid enters the EXXPRESS tubes and filtrate
begins permeating though the tube walls. As the fluid is
discharged though the tube wall, die solids begin to
accumulate on the inside of die tubes. As die solids deposit
increased pressure is required to force liquid through die
increasing membrane thickness. When die membrane
reaches a controlled diickness, die discharge cycle begins.
The discharge valve is opened and flush water is sent
through die tubes while die mechanical pinch rollers begin
traversing die EXXPRESS module. Since die inner walls
have been coated with solids, die internal tube diameter is
decreased, resulting in higher fluid velocities within the tube.
As die tube rollers traverse die module, die pinching causes
die cake to break from die tube walls and decrease die tube
diameter further, resulting in still higher fluid velocities at
die rollers. This creates a venturi effect which causes die
cake chips to be drawn into the liquid stream and swept
from title EXXPRESS module (Figure A-3). The resulting
fluid diat exits die module contains die solid cake chips and
die flush liquid This two phase stream is then pumped to
die dewatering screen to separate die solids from die liquid.
The load and discharge cycles are controlled automatically
by a process controller. It also allows for manual control
of die pinch rollers mat traverse die module. The automatic
controller also controls opening and closing of die discharge
valve.
A3 Sludge Dewatering
Filter cake dewatering occurs through die use of a gravity
dewatering (wedgewire) screen. The dewatering screen has
a grating that is small enough to pass die flush liquid but
retain die solid filter cake chips. Fluid carrying die cake
chips that exit die EXXPRESS unit is pumped directly to the
dewatering screen. Fluid that passes tiiough die grating is
collected in die EXXPRESS feed tank where it can be
recycl«5d to die EXXPRESS for further dewatering. Solids
that are trapped on die screen eventually accumulate and fall
into a drum or storage container for proper disposal.
There are many designs which can accommodate die
dewatering of die sludge. The system described above was
used during die SITE demonstration tests. Modification of
this de-sign may have been able to produce filter cake with
higher solids content The dewatering mechanism should be
designed based upon specific process attributes.
25
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Appendix B
Vendor's Claims
This appendix summarizes the claims made by the
developer, EPOC Water, Inc., regarding the microfiltration
technology under consideration. This appendix was generated
ind written solely by EPOC, and the statements presented
herein represent the vendor's point of view. Publication here
does not represent EPA's approval or endorsement of the
statements made in this section; EPA's point of view is
discussed in the body of this report
B.I Introduction
The EPOC microfiltration technology treats wastewater or
dilute sludge containing heavy metals to meet stringent
discharge limits. Wastewaters of this type range from
contaminated groundwater containing 1 to 2 mg/L of heavy
metals, through industrial wastewaters containing up to 50
mg/L of heavy metals, to acid mining wastes containing up
to 1,000 mg/L. Typically, the industrial wastewaters will
also contain participates, oil & grease and organic materials
including solvents and detergents.
The ideal treatment technology has to achieve two functions;
fust, produce a treated water suitable for discharge and
second, produce a small volume of concentrate for disposal
or reclamation. The concentrate should be compact so that
it passes the RCRA paint filter test and the toxicity
characteristic leaching procedure (TCLP).
Other important considerations are:
operator handling of the waste should be
minimized,
the treatment should be cost effective,
the system should be robust and versatile providing
treatment of a wide range of different contaminants
and different concentrations.
B2 EPOC Microfiltration Technology
The microfiltration technology is a pressure driven
separation process for removing suspended solids,
particulates and heavy metal precipitates. The microfilter
modules utilize a patented flexible woven tube bundle that
has excellent chemical and temperature resistance. The
modules can be operated in EXXFLOW mode, with a cross-
flow tube velocity, or in dead-end EXXPRESS mode, such
that the system operates as an automatic tubular filter press.
The EXXFLOW mode is used to separate suspended solids
and precipitated heavy metals. The EXXPRESS mode is
used to dewater weak sludges or the concentrate from the
EXXFLOW process.
Wastewaters containing dissolved metals are dosed with
chemicals to precipitate the metals. Typical chemicals are
alkalies such as lime, sodium hydroxide (caustic),
magnesium oxide, or sulfides such as sodium sulfide and
carbamates. Generally, heavy metals precipitate as their
hydroxides within the pH range 9-10 and which alkali to use
depends on the waste characteristics and process economics.
Sulfide and carbamate chemistry is applicable in the pH
range 7-10 and often provides for a higher quality treated
water.
B.2.1 EXXFLOW Microfiltration
The EXXFLOW microfilter is a robust and compact unit
available in size ranges of 5 gpm to 2,000 gpm. The system
consists of a feed tank, recirculation pump, EXXFLOW
modules and control system as shown in Figures B-l and B-
2. The tubular filter modules are available in various sizes
with 10 sq ft to 150 sq ft of filter area to accommodate
different plant flow rates. The modules are configured in
banks with up to 16 modules per bank.
26
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Figure B-l. Typical Vertical Module Configuration.
ALKALI
PH A
PLANT
WASTE
WATER
J JUST
1-EX SOLIDS
CONCENTRATE I
"'
In M mil
FILTRATE
PRODUCT
WATER
M M M i IH 0-6 OX
FILTRATE 'DRY SDLIDS
RETURN
TD EXXFLDW
Figure B-2. EPOC Microflltration Process Schematic.
27
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The feedwater containing the precipitated heavy metals is
pumped into the filter module bank(s). The treated or
filtered water is collected in the module housing and
discharged. In some applications, pH adjustment is needed
prior to discharge. The EXXFLOW modules operate with
the wastewater on the inside of the tubes such that the
suspended and colloidal matter forms a thin dynamic
membrane layer on the internal surface of the tubes. The
liquid flow is maintained by the recirculation pump to
control the thickness of the layer. Tube velocities of 3 fps
to 6 fps are typically used. Part of the feed becomes treated
water and the remainder (reject) is recirculated to the feed
tank.
A concentrate bleed stream removes the solids and
precipitated heavy metals from the system to maintain the
recirculation loop at 1 to 5% w/w solids. The concentrate is
automatically discharged from the unit and transferred to the
solids dewatering unit
Typically the system operation is controlled by a
programmable logic controller (PLQ. The microfilter is
fabricated from corrosion resistant materials: polyester cloth.
epoxy end castings and FRP module shells. Operating
parameters are PC to 65°C (32 to 150°F) temperature range,
pH 2 to 12 and pressures of 20 to SO psl
Periodically the modules are cleaned due to the build-up of
impurities at the tube surfaces. The EXXFLOW modules
are backwashed by the backwash pump which draws filtrate
back through the microfilter tubes. Because the tubes are
flexible, they collapse during the backwash operation and
break up the impurity layer. Difficult-to-remove foulants are
chemically cleaned with acid, hypochlorite, or alkaline
detergents.
B.2.2 EXXPRESS Automatic Tubular Filter
Press (ATFP)
The ATFP process uses two cyclic operations of solids
loading and cake discharge. In the load cycle, the waste is
pumped into the EXXPRESS tube module with the reject
valve closed. The solids form a thin cake of up to 5 mm
(3/16 in) on the inside of the tubes. The filtrate is collected
in the lower compartment and drained out The
load/dewatering cycle is complete when the pressure inside
the ATFP reaches 50 to 75 psi or the load cycle timer is
finished. The cake discharge cycle then commences by
opening the reject valve and traversing the modules with
rollers which disrupt the shape of the tube. This disruption
causes a venturi action which simultaneously and
aggressively causes the filter cake to chip off into the flush
stream and also cleans the filter cloth on each cycle. The
flush water (same as the feed water) is directed to a
wedgewire separating screen. After the cake discharge
cycle, the ATFP starts a new load cycle. The flush water is
recycled to the front of the system. An EXXPRESS process
diagram is shown in Figure B-3.
EXXPRESS MODULE
FEED
1-5% SDLIDS
M M M M
FILTRATE f
RECYCLE
TD EXXFLDW
DISCHARGE
VALVE
SCREEN
20-6OX
SDLIDS
RECYCLE
TD EXXPRESS
Figure B-3. EXXPRESS Dewatering Schematic.
28
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B.3 Applications of the EPOC
EXXFLOW/EXXPRESS Technology
The technology has been successfully applied for
removal of hexavalent chromium from
contaminated groundwaler
removal of kerosene from aluminum metal parts
washer
removal of nickel solids from electronic industry
operations grinding
removal of dissolved nickel and zinc from plating
wastes
removal of dissolved ethylene glycol, copper, and
nickel from manufacturing
removal of hexavalent chromium, copper, iron, and
nickel from electroplating
removal of iron and manganese from groundwaters
removal of emulsified oil and iron from oil field
waters
removal of pesticides, arsenic, zinc, and oils from
pesticide manufacturing
removal of lead and other heavy metals from
ceramics wastes
removal of copper particulates from ink wastes
removal of oil & grease and heavy metals from
industrial laundries
removal of lead from battery manufacture
removal of heavy metals from hazardous waste
treatment facility.
Table B-l provides details of the capability of the
technology by industry and by contaminant material.
The EXXFLOW/EXXPRESS system is available as truck
and trailer mounted units as well as for permanent
installations.
EPOC usually tests all wastewaters before operation to
determine the optimal chemical dosages and process
parameters.
To date, the process has been applied full-scale mainly to
wastewaters containing heavy metals and oil and grease and
to contaminated groundwaters. Hie technology is ideally
suited as a pretreatment process prior to other technologies
such as activated carbon, air stripping, ion exchange, and
reverse osmosis.
Table B-l. Wastes Compatible with the EPOC System
INDUSTRY TYPE
Acid Mine Drainage
Battery Manufacture
Ceramics
Chemical Manufacture
Contaminated Groundwaler
Groondwater Containing Hexavalent
Chromium and VOC
Industrial Laundries
Inks
Oil Held Wastewater
Metal Plating
Paint Pigments
Pesticides
Weak Sludges from Manufacturing
COMPOUNDS
Aluminum
Antimony
Arsenic
Cadmium
Chromium
Cobalt
Copper
Cyanide
Dyes
Inks
Iron
Kerosene
Lead
Manganese
Mercury
Nickel
Oil &. Grease
Paints
Pigments
Selenium
Silver
Vanadium
Waste Oil
B.4 System Advantages
The EXXFLOW/EXXPRESS technology has the following
advantages over existing systems:
They provide a combined heavy metal separation
and sludge dewatering system.
The microfilter barrier ensures high quality treated
water.
- The microfilter can take high solids and oily
feedwater without pretreatment
The system is very tolerant to changes in feedwater
concentrations.
Minimal operator attention and handling of sludges.
Proven cost-effective technology on size ranges
from 5 gpm to 3 mgd.
Transportable in the smaller size ranges.
29
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r
Modular construction, allowing phased expansion.
Adaptable to wastes containing 1 to 10,000 mg/L of
heavy metals.
Filter cakes are compact and in most cases pass the
TCLP. Wastes can also be further stabilized at the
EXXPRESS treatment stage by the addition of fixative
agents such as silicates, fly ash, and kiln dust
30
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Appendix C
Site Demonstration Results
C.I Introduction
In January of 1989, Epoc Water, Inc. (EPOC) of Fresno, CA
submitted a proposal for their microfiltration technology to
the U.S. Environmental Protection Agency's (EPA)
Superfund Innovative Technology Evaluation (SITE)
Program administered jointly by the Office of Research and
Development (ORD) and the Office of Solid Waste and
Emergency Response (OSWER). EPA selected the EPOC
microfiltration technology for demonstration in the SITE
program. Iron Mountain Mine (IMM) in Redding, California
was selected by EPA and EPOC as an appropriate site for
the technology demonstration. The technology was
demonstrated at the IMM site in May and June of 1992.
This appendix briefly describes the IMM site and
summarizes the SITE demonstration activities and the
demonstration test results.
C2 Site Description
The IMM site is located approximately 9 miles northwest of
Redding. California in Shasta County. Figure C-l is a map
of the site. For more than 100 years, the IMM site was
mined for copper, zinc, iron, silver, gold, and pyrite. Mining
activities were discontinued in 1962.
As rainfall and groundwater flow on the exposed surfaces of
the mining areas, sulfuric acid is produced and high
concentrations of aluminum, copper, zinc, cadmium, and iron
are released from the mining deposits. The result is acid
mine drainage (AMD) which has a low pH due to the
sulfuric acid and a high heavy metals content
Large volumes of AMD flow from the IMM site in several
different streams. The IMM site is the worst AMD problem
in the country at this time, in terms of total volume of AMD
produced and total quantity of heavy metals released. The
flow of AMD from Iron Mountain is controlled through use
of a reservoir, which prevents too much AMD from entering
the Sacramento River. In the past, fish kills and other
problems have occurred due to heavy winter rains and
overflow of the reservoir.
Several acid mine drainage streams exist on the site. Five
major sources account for the majority of the copper, zinc,
cadmium and iron that migrate from the site. These five
sources of AMD are: the Richmond Portal and the Lawson
Portal, which discharge into Boulder Creek; and the Big
Seep, Old No. 8 Mine Seep and the Brick Flat Pit Bypass
discharging into Slickrock Creek. The two streams chosen
for tltie demonstration were the Richmond Portal and the Old
No. 8 Mine Seep.
C3 Wastewater Contamination Characteristics
Both the Richmond Portal and the Old No. 8 Mine Seep had
high levels of aluminum and iron, with some arsenic.
cadmium, copper, lead, magnesium, manganese and zinc.
The concentration of iron in the Richmond Portal was
approximately 20,000 mg/L with a pH of 0.6 and a
conductivity of 195,000 umhos/cm. The Old No. 8 Seep had
an iron concentration of approximately 2,000 mg/L with a
pH of 2.3 and a conductivity of 8.000 umhos/cm. The
Richmond Portal liquid had a pale green color and both
streams had a characteristic metallic odor.
C.4 Review of SITE Demonstration
The Site Demonstration was divided into three phases: 1)
site preparation, 2) technology demonstration, and 3)
demobilization. These activities and a review of the
technology and equipment performance during these phases
are described below.
31
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WCXftAT
.\\ V.
wweu
MIME
MOUNTAIN
MINE,
MIUUBWA
FLAT9
Figure C-1.
Iron Mountain Mine Location Map Showing Richmond
Portal, Old No. 8 Mine Seep and Other Point and
Nonpoint Sources.
32
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C.4.1 Site Preparation
A level area of approximately 1,000 sq ft was selected near
the flume that contained water from the Old No. 8 Seep.
The test site was located within 50 yd of the location where
the Old No. 8 Seep percolated from the ground. An office
trailer was brought on site along with a portable toilet. Five
polyethylene storage tanks (capacity of 6000 L or 1,600 gal
each) were brought to the site and leveled in the area.
Plywood was used to create a "floor" on which equipment
could be leveled and set up. The plywood also created a
building platform to which equipment such as pumps, tubing
and flow meters could be anchored. To obtain test water, a
gravity syphon was created by connecting a line from the
Old No. 8 flume and the storage tanks. This produced a
continuous source of raw feed during the demonstration test
C.4.2 Support Equipment
Support equipment for the microfiltration system included
storage tanks for the treated and untreated acid mine
drainage and for clean water, a generator and compressor for
power and compressed air, and a forklift for material
handling. Specific items include:
Five 6000 L (1,600 gal) polyethylene tanks for storage
and volumetric measurement of the feed and treated
water.
Two platform scales for weighing filter cake and
treatment chemicals.
An office trailer approximately 20 ft by 8 ft with two
rooms for shelter, storage and the field laboratory,
A 1600 L (425 gal) polyethylene water wagon/truck
tank for water transport,
A 3/4 ton pickup truck for transporting supplies, fresh
water, and for transportation of the Richmond Portal
water to the test site,
A cellular phone for emergency communications,
laboratory communications, ordering supplies and
scheduling deliveries,
A 20 kW diesel generator with 3-phase 240 volt 60 hz
capacity to power the process equipment, and single-
phase 110 volt service for the support equipment and
the field trailer,
An air compressor with a capacity of 100 scfm for
pump and pneumatic valve operation,
A heavy duty construction forklift for filter cake
handling and treatment chemical handling.
Several 55 gal drums to contain the filter cake from the
process,
Tiransfer pumps for the liquids,
A sump pump for collecting water.
Analytical equipment for measuring field parameters,
Piping and flow meters for measuring liquid flow rates
and volumes,
Several gas cans for transporting gas and diesel to fill
the compressor and generator,
Extra lumber for constructing pipe and flow meter
supports, and
Miscellaneous hand tools, including a hammer,
wrenches and screwdrivers.
C.4.2,1 On-Site Support Services
Field sample analyses were performed in a two-room field
trailer. Half of the trailer was used as the laboratory, while
the oilier half provided air-conditioned shelter for the Held
crew as well as storage for supplies and equipment. A
portable computer and printer were used for data processing.
There were no other support buildings or services available
on-site.
A forklift was brought to the site to facilitate the handling of
the sludge filled drums. The forklift was also used to move
pallets of treatment chemicals and the liquid sodium
hydroxide drums.
C.4.22 Utilities
Utilities required for the demonstration included water,
electricity, phone service and compressed air. Since no
utility lines were available at the demonstration site, all
utilities were provided through portable means. A 20 kw
diesel generator was used to provide electricity to both the
microfiltration process equipment and the Held trailer. Three
phase, 240 volt power was supplied to the process
equipment, and single phase, 120 volt power was used for
the trailer and miscellaneous support equipment
Compi-essed air was provided by a gasoline-powered
compressor with a capacity of 100 scfm.
33
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Fuel for both the generator and the compressor, purchased
at a service station in Redding, was brought to the site each
day in gasoline cans using a rented pickup truck. This same
truck, outfitted with a 425 gal tank, was used to transport
non-potable water for equipment decontamination and
process needs to the site from a clean water source located
elsewhere on Iron Mountain. Water was stored in 1,600 gal
tanks at the test site. Potable water for drinking was
purchased in bottles and brought to the site. Reagent-grade
water for cleaning sampling equipment and performing field
blanks was purchased from a laboratory supply house.
Telephone service was provided by a cellular phone rented
for the demonstration. This telephone was required for
ordering supplies, scheduling deliveries, maintaining contact
with the analytical laboratory and home offices and for
emergency communications. The remote location of the site
made the acquisition of a portable telephone vital to the
safety of the field crew.
C.43 Technology Demonstration
This section describes the operational and equipment
problems and health and safety issues associated with the
SITE demonstration.
C.4.3.1 Operational Problems
The SITE team experienced operational problems during the
demonstration. Some of these problems resulted in changes
to the demonstration schedule, duration, and number of test
runs performed. Other problems required decisions to be
made in the field to solve them. These operational problems
and their resolutions are described below:
The Iron Mountain Mine Site is fairly remote and
reachable only by narrow dirt road. Transportation of
equipment to the site required extra care and planning.
All utilities required on the site had to be supplied
through portable items. Access to the Iron Mountain
Mine site is controlled through several locked gates
along the road; supplies could only be delivered when
a member of the field team carrying a key was present
at the outermost gate to provide access. At least an
hour was required to drive between the nearest sources
of equipment and the site. These access problems
required additional planning and personnel to ensure
needed supplies were on site and to avoid delays.
» The developer required a much longer initial
shakedown period than initially anticipated. Both
mechanical and chemical problems occurred for several
weeks, delaying the commencement of the
demonstration test. Even after testing had begun, some
days of testing had to be aborted due to equipment
problems. The demonstration test unit was
continuously modified and changed in the field
throughout testing. The number of test runs to be
performed was reduced significantly after several weeks
in die field had passed and several repeated failures of
the EXXPRESS unit had occurred. All but one of the
runs using Richmond Portal water as the feed were
eliminated.
Samples could not be shipped the same day due to
the long days at the test site. Samples were shipped
the morning following their collection by overnight
courier service.
It was considered unsafe to travel the road from the
Iron Mountain Mine site after dark. This, as well as
the 1 hr travel time to the site or back, cut down the
available time for testing each day.
The startup time for the unit was much longer than
anticipated by the developer; hence, the 8 hr runs
originally planned were decreased to 6 hr in order to be
able to complete the sampling activities. In fact, most
of the demonstration runs lasted about 4 hr. These
changes resulted in modifications to the original
sampling plan.
During one day of the demonstration test, access to the
site was blocked completely due to a truck accident
(not related to this project) and the resulting cleanup on
the road to the site. No testing could be performed on
that day.
Since the demonstration testing period was much longer
than originally planned and the developer's personnel
had another commitment to fulfill, a three-week-long
hiatus occurred before the testing could be completed.
The process unit had to be drained and cleaned each
day to prevent settling, scaling and fouling of the
process equipment The nightly cleaning may not have
been required if the unit were operated continuously.
C.4.33 Equipment Problems
The SITE team experienced many equipment problems
during the demonstration test These problems resulted in:
(1) repeating the affected demonstration test runs, (2)
eliminating several planned runs. (3) on-site equipment
maintenance and modification, and (4) changes in the
demonstration schedule and duration.
34
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The equipment that was brought on site was different
from that originally described in the testing documents.
A source of compressed air to operate a diaphragm
pump was required that had not been planned or
acquired. During testing in cold temperatures, the
pneumatic pump began to stall as ice accumulated on
the discharge manifold. An air drying mechanism was
installed to prevent freezing of the pump parts.
Several electrical and mechanical problems with the
equipment occurred during shakedown requiring
maintenance, modification of the equipment, and
acquisition of additional and replacement parts.
Electrical problems were most likely due to inclement
weather conditions experienced during shakedown and
testing. The developer had to bring an additional person
to the field to assist with operation and maintenance of
the equipment
The feed water (Old No. 8) did not react with the
treatment chemicals instantaneously and the mixture did
not behave as anticipated by the developer. Control of
the pH of the treated feed and the permeate required
time for trial and error, on some days samples could
not be collected. Poor control led to inconsistent
permeate output
Repeated problems with clogging of the EXXPRESS
filter tubes occurred requiring many changes to
operating procedures and equipment configuration.
These problems also resulted in equipment downtime
and aborted runs.
The dewatering screen for the filter cake did not
perform as well as anticipated. More water was
retained in the filter cake man was felt to be
representative of the process operation. Minor
modification of the screen helped but did not eliminate
this problem.
A basket strainer was installed to remove large clumps
of solids before fluid was fed to the EXXFLOW unit
C.4.3.3 Health and Safety Considerations
In general, health and safety hazards associated with this
demonstration test were physical in nature. The pH of the
Old No. 8 stream was about 2.3 and mat of the Richmond
Portal stream was 0.6. These highly acidic liquids presented
a hazard to personnel through splashing on the skin or in the
eyes. Lifting of heavy items and working with and around
the operating equipment were additional physical hazards as
were the hazards associated with tripping or slipping on the
uneven and rocky ground surface.
Heat stress was a major concern during much of the
demonstration activities as temperatures in the area were in
the 80s and 90s during most of the demonstration testing.
The hazard was increased by the need to use protective
clothing that reduced evaporation from the skin and added
additional weight to the personnel. The air conditioned
trailer and die availability of cool potable liquids were very
important in the prevention of heat stress disorders.
Other hiizards of the site included: fire and explosion hazard
from the liquid fuel on site for the generators; potential
exposure to sodium hydroxide which is corrosive and
powdered lime which can be a respiratory irritant; insects
and animals prevalent at the site; and exposure to inclement
weather (hail, thunderstorms). The remote location of the
site provided the additional hazards associated with driving
along the narrow dirt roads and the unavailability of nearby
assistance in case of emergency.
Personnel were required to wear protective clothing
appropriate to the tasks being performed. Steel-toed boots
were used in all areas on site. Chemical resistant boots were
used during any tasks with potential contact with the low pH
feed liquids. Modified level D protection was used during
sample collection, including hard hat, faceshield, latex inner
gloves and nitrite outer gloves. Sampling and handling of
the Richmond Portal liquid was performed by personnel
wearing splash repellant full-body coveralls and goggles with
a faceshield in addition to the hard hat and gloves. For field
laboratory analyses, goggles, latex or nitrite gloves, and a
splash apron were worn as a minimum. Dust masks were
worn when transferring the 50 Ib bags of lime to the feed
hopper. No other respiratory protection was required on this
site because no volatile compounds were present in the
waste liquids.
C.4.3.4 Site Demobilization
The process equipment was drained, decontaminated and
removed from the demonstration site after testing was
completed. All of the piping and pumps were disassembled.
Some of this equipment was decontaminated for reuse on
other sites, while materials that were contaminated or
damaged were disposed of. Equipment and tools to be
retained were sent off-site for storage. All of the rental
equipment was returned, including the trailer, generators,
forklift and platform scales. The site was later cleared of
any remaining debris.
The drums of filter cake were to stay on site; they were
transported to another area on Iron Mountain for permanent
storage. Other contaminated materials, including used
personal protective equipment, were placed in drums for off-
site disposal. The storage tanks, which had become
35
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contaminated and weathered, were cut into pieces and
drummed for off-site disposal. A total of 12 drums was sent
to ft hazardous waste landfill.
C.4.35 Experimental Design
The objectives of the technology demonstration were to 1)
assess the technology's ability to remove toxic metals
present in the acid mine drainage (AMD) waters, viz. Old
No. 8 Mine Seep and Richmond Portal, at the EMM site,
with a 90% confidence level, to residual levels claimed by
the developer (see Table C-2), and 2) evaluate the system's
ability to dewater the metals-bearing sludge resulting from
the separation of precipitated metals and the treated water to
solids concentrations >20% for NaOH treatment and >40%
for lime treatment.
These objectives were achieved through a carefully planned
and executed sampling, analysis and monitoring plan, but
with changes which were implemented in the field as a
result of process and operational modifications made by the
developer either just prior to the start of the demonstration.
during the testing, or as a result of some operational
problems encountered.
The EPOC microfUtration technology was tested on two
AMD streams, the Old No. 8 and Richmond Portal. It is
known from conventional metals precipitating processes that
for a given wastewater stream consisting of an array of
metals at different but more or less steady concentrations,
there exists an optimum pH for a given precipitating agent
at which an optimum residual metals concentration in water
is realized. These optimum pHs and required reaction times
for the treatment of Old No. 8 and Richmond Portal with
lime, caustic and magnesium oxide were established through
beaker tests by EPOC at its Fresno, CA facility prior to the
start of the demonstration. Therefore, the only parameter
that was to be varied to evaluate the technology was the
selection of precipitating agent(s). The demonstration runs
conducted on the two AMD streams are described in terms
of the precipitating chemical(s) and the actual flow rates, run
time and volume treated, and are presented in Table C-l.
In order to achieve the demonstration objectives, solid and
water samples were collected from the EPOC microfUtration
system and were analyzed for a number of critical and non-
critical parameters. These parameters had been further
categorized as process or analytical and as off-site laboratory
or field determined. Metals (i.e., Al, As, Cd, Cr, Cu, Fe, Pb,
Mn, Mo, Ni, and Zn), pH and total solids of the water
samples and the metals, pH and moisture content of the filter
cake solids were considered critical analytical parameters,
and the flow rates and total volumes of the water streams
and the mass rate and total mass of the solids streams were
considered critical process parameters. Non-critical
measurements that were also performed included total
dissolved solids, acidity or alkalinity, sulfate, temperature
and conductivity, turbidity and dissolved oxygen of the water
samples and density and toxicity characteristic leaching
procedure (TCLP) for metals in the filter cake solids. In
addition, electrical consumption and system pressure were
also monitored. EPA-approved sampling, analytical, quality
assurance, and quality control (QA/QQ procedures were
followed to obtain reliable data. The Technology Evaluation
Report provides and/or summarizes all results.
C.4.3.6 Review of Treatment Results
This section summarizes the results of both critical and non-
critical measurements for the demonstration of the EPOC
microfUtration technology and evaluates the technology's
effectiveness in treating the acid mine drainage streams
contaminated with heavy metals.
Summary of Results for Critical Parameters
The SITE Demonstration test was conducted at the Iron
Mountain Mine Superfund Site, in Redding, CA. This site
is contaminated with several water sources that are laden
with heavy metals. Two water sources were tested during
the demonstration, which are known as Old No. 8 Mine
Seep (ON8) and Richmond Portal Seep (RP). Both acid
mine drainage streams are contaminated with high ppm
levels of iron, aluminum, copper, and zinc. Several other
metals were present at much lower levels but were still
considered critical in the evaluation of this technology.
Test runs were made using three treatment chemicals on
water collected from the Old No. 8 seep and a combination
of two chemicals was evaluated on water from the
Richmond Portal Seep. Test runs averaged about 4 hr in
length during which samples were collected of the raw feed,
permeate, and filter cake. Samples were composited for
each of the parameters based upon a weighted average of the
flow rate and production rate of filter cake. Several grab
samples were also obtained during each run. Samples were
analyzed primarily for metals to determine removal
efficiencies and the fate of the heavy metals. Results for the
treated effluent (permeate) are summarized in Table C-2.
The first series of tests were performed in duplicate on water
obtained from the Old No. 8 seep with 50% sodium
hydroxide as the precipitating agent Average feed
concentrations of aluminum, copper, iron and zinc were
approximately 700, 170, 2000 and 60 mg/L (ppm).
respectively. Results for the permeate composite samples
36
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Table C-t. EPOC DtmoofUtkm Tot Rom Performed at IMM Site
Stream
Old No. 8
Richmond Portal
Precipitating
Chemicals
Caustic. 50%
Caustic. 50%
Lime
Lime
Magnesium Oxide
Magnesium Oxide
MgO/Causac
MgO/Causac
MgO/Causdc
Test Run
#
1 A
1 B
2A
2B
3B
3C
4 A
4C
5 A
Raw Feed
Rate, gpm
3.0
3.0
3.7
3.4
3.5
3.1
3.5
2.9
1.0
Chemical Feed
Rate, gm/min
208
206
103
95
too
88
47/87
40/111*
38/272*
Run Time.
min
238
241
303
307
312
242
253
238
238
Treated
Volume, gal
774
756
949
901
917
714
626
746
210
40 gm/min MgO/111 gm/min 50% NaOH
TaWtC-2, Treated Effluent Quality
Aoalyte
Aiunuaum
Arsenic
Cadmium
Chromium
Copper
Iron
Lead
Manganese
Molybdenum
Nickel
Zinc
PH
Old No. 8 Mine Seep, Permeate Composite Cone., mg/1
Feed Cone.,
mg/L
700
0.1
OS
0.07
170
2000
<0.2
13.3
0.11
0.18
60
2.32
Developer's
Claim Permeate
Cone., mg/L
1.0
0.2
0.1
0.1
0.1
1.0
1.0
0.1
0.5
0.1
0.1
N/A
TEST1
Caustic
TEST2
Lime
TESTS
Mg Oxide
TEST 4
MgO+
Caustic
Permeate Composite
Cooc.4og/L
36
<0.03
<0.01
<0.01
<0.03
0.27
<0.02«
0.01
<0.03
<0.03
0.03
10.2,-
Conc.ang/L
15
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for both tests indicated that all metals were reduced to levels
less than the claimed 1.0 mg/L or 0.1 mg/L objectives with
the exception of aluminum. Results for aluminum in the
composite samples for the first and second test were 61 and
12 mg/L respectively; iron concentrations in the composite
samples of the permeate were 0.27 mg/L and 0.15 mg/L;
below the developer's claim of 1 mg/L. Although aluminum
was not reduced below the vendor claim of 1 mg/L,
reductions of 91% and 98% were observed in the two test
runs. The high residual aluminum was probably caused by
the difficulty encountered in controlling the pH in the
reaction tank. The improved reduction in the second run can
be attributed to the process operators becoming more
familiar with pH control and operational characteristics
required to treat this water.
Similar results were observed in the succeeding tests with
the Old No. 8 Mine Seep and lime, magnesium oxide, and
the mixture of magnesium oxide and caustic, with some
notable exceptions. These results are also presented in Table
C-2. Specifically, reduction of aluminum to <1 mg/L was
achieved with the magnesium oxide and the mixture of
magnesium oxide and caustic, but not with lime. Iron was
reduced further below the 1.0 mg/L objective, to about 0.1
mg/L, with lime, magnesium oxide, or magnesium
oxide/caustic. And, while lead remained below the
objective, 1.0 mg/L, in all tests, the removal appears to be
less complete with magnesium oxide than with caustic or
lime. Similarly, manganese removal was less complete with
the magnesium oxide. Because of the low concentrations of
several of the metals in the feed water, it is not possible to
discern differences in removals of these metals with the
different bases.
All tests with the Old No. 8 Mine Seep were carried out at
a flow rate of about 3.0 gpm, (see Table C-l) and
discharged permeate at essentially the same rate throughout
the approximate 4 hr of treatment, within the limits
encountered due to forced interruptions and other factors.
The original plan was to use a flow rate of approximately 7
gpm, but operational problems made this rate unachievable
with this wastewater.
Table C-2 also indicates the elevated pH values observed in
the permeates from all the tests. It is unknown whether more
precise pH control would have affected permeate quality,
sludge production, or sludge quality. Another question that
remains unanswered is whether the permeate would have
precipitated additional solid if it were re-neutralized to a pH
of <9,0 for discharge.
When a mixture of magnesium oxide and caustic was used
to precipitate the metals from the Richmond Portal AMD,
high removals of all heavy metals and aluminum were
observed while iron and manganese failed to meet the
developer's claims of 1.0 mg/L and 0.1 mg/L, respectively.
Nevertheless, with an initial concentration of 20,600 mg/L
iron, 2140 mg/L aluminum, and 399 mg/L copper, the
precipitation and microfiltration were very effective in
removing metals. The raw feed flow rate for this single test
was approximately 1 gpm and permeate flow rates were
slightly higher, about 125 gpm. Permeate pH was <9.0.
In addition to affecting the residual metal content in the
permeate, the choice of base also affected the solids content
in the sludge and, consequently, in the filter cake. This also
affected the efficiency and operational effectiveness of the
EXXPRESS microfiltration unit The sludge from the caustic
treatment was clearly more fluid than that from either lime
or magnesium oxide, presented greater operating difficulties
in the EXXPRESS, and resulted in significantly lower solids
content in the resulting filter cakes. None of the filter cakes,
regardless of base used, achieved the claimed minimum
solids content, 20% with caustic and 40% with lime (or
magnesium oxide). In addition, the calcium sulfate
coprecipitated with other metals when using lime appears to
add further operational difficulties to sludge dewatering in
the EXXPRESS. It remains the developer's opinion that the
EXXPRESS system could be optimized to overcome these
difficulties and achieve the objectives.
In addition to lower-than-expected solids content in all filter
cakes from the EXXPRESS, the total mass of solids
recovered from all. tests were significantly lower than
anticipated by calculating the theoretical solids available and
comparing to the weights and solids content of the filter
cakes as recovered. Visual examination of the system
indicated that significant volumes of solids were retained in
the system, both settled in the reaction vessel and dispersed
in the liquid retained in the system.
A compilation of the data for the several tests is presented
in Table C-3 and more detailed information on the filter
cake yields is summarized in Table C-4.
38
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Table C-3. EPOC Microfiltration Results Summary
Feed Wastewater pH
Treated water pH
Tocal metals Removed, %
Permeate Alkalinity as CaCO,, mg/1
Total Dissolved Solids Removed, %
Water (volume) Recovered, %
Filter Cake (residual waste solids)
CakepH
Dry Solids in the Filter Cake, %
Cake Density, gm/cc
Waste solids Generated, %*
= 100 x solids vol-AVastewater vol.
Order of Magnitude Reduction
Total Metab
Aluminum
Arsenic
Cadmium
Chromium
Copper
Iron
Lead
Manganese
Molybdenum
Nickel
Zinc
Old No. 8 Mine Seep
Caustic
Treatment
2.17
9.74
98.8
240
14
95.4
9.2
12
1.13
4.6
2
2
1
2
NC
3
4
NC
3
2
3
3
Lime
Treatment
2.33
10.4
99.56
80
76
95.7
9.8
32
1.37
4.3
2
2
1
2
NC
4
4
NC
3
1
1
3
Magnesium
Oxide
Treatment
2.5
9.31
99.97
30
26
94.7
9.3
30
1.23
5.3
4
3
1
2
NC
4
4
NC
2
1
NC
3
MgO +
Caustic
Treatment
2.4
9.8
99.95
23
24
94.9
8.7
25
1.21
5.1
3
3
i
1
NC
4
4
NC
2
NC
1
3
Richmond
Portal
MgO +
Caustic
Treatment
0.6
8.5
99.92
38
32
73
8.2
26
1.25
27
3
4
2
2
NC
4
4
NC
1
1
NC
4
* - By calculation
NC - Not calculated
39
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Table C-4. Filter Cake Output from EPOC EXXPRESS.
Run
no.
1A
IB
2A
2B
3B
3C
4A
4C
Solids Mass
alkali calculated
NaOH 279
NaOH 340
Ca(OH)j 343
Ca(OH)2 440
MgO 490
MgO 230
NaOH/MgO 300
NaOH/MgO 471
Recovered
measured
239
264
93
87
17
7.5
13
81
solids%
11.6
13.4
30.3
32.9
27.6
31.4
28.4
20.8
* calculated from the volume of water treated and % solids
found in filter cake.
Analyses of the filter cakes indicated that, as expected,
aluminum and iron were the predominant constituents.
Heavy metals were present at much lower concentrations
(Table C-5). When TCLP tests were carried out on the filter
cakes, the specified TCLP metals were all below regulatory
limits and/or were "non-detectable".
TftbleC-S. FUter Cake Metal Coateit
Metal
Aluminum
<*"*ftfj*mii*m
Copper
Iroa
Lead
Mangaoete
Nickel
Zinc
Old No. 8 Seep
Cttutic
1A
80.200
69
21,000
251,000
<90
1.910
<39
7280
IB
87,900
67
21,600
274.000
<39
1,960
35
7.740
Lime
2A
39.600
32
9,650
116,000
35
899
9
3390
26
37,200
0.6
9.040
109,000
0.7
843
14
3,210
MgO
3B
37,600
27
8,850
106,000
<19
996
11
3.130
3C
51.000
33
11,800
146,000
<17
1300
13
3.950
MgO/NaOH
4A
47400
53
11,200
158,000
<31
1,000
17
6.180
4C
42,150
32
9,480
120,000
<41
924
23
3.400
Richmond
Portal
MgO/NaOH
5A
24.100
157
4.230
239,000
<66
241
<14
20550
40
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Appendix D
Case Studies
The information contained in the following case studies was provided by EPOC Water, Inc. and has not been subjected to
EPA's QA/QC program nor reviewed by EPA for accuracy.
41
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D.I Bench Scale Treatability Testing
EPOC Testing Facility, Fresno, CA
This case study presents the treatability testing performed by
EPOC and SAIC in May of 1990 using water from the Iron
Mountain Mine site. The purpose of this treatability testing
was to confirm the treatability of the Iron Mountain
wastewaters using the EPOC system and to determine the
operating conditions, treatment chemicals, and target
reductions for use of the technology.
D.I.I Beaker Tests
The first phase of the treatability testing involved beaker
tests to determine which precipitating agents would be
appropriate to precipitate the metallic constituents of the
waste. This test was performed using beakers and filtration
of the resulting slurry through a vacuum filtration apparatus
using a 0.45 urn membrane filter. Based on the historical
water characterization data of the waste streams, lime
(calcium hydroxide) and caustic (sodium hydroxide) were
chosen and tested as precipitating agents.
D.1.2 Single-Tube Treatability Tests
After the beaker tests, treatability tests were conducted using
single-tube EXXFLOW and EXXPRESS units. Each unit
used was 2.5 cm (1 in.) in diameter and 1 meter long.
EPOC chose to use only lime as a precipitating agent during
these tests.
The tests were conducted by treating the wastewater from
both the Old No. 8 seep and the Richmond Portal by
precipitating with lime and treating the slurry using the two
bench-scale process units. Sampling and analysis of the
feed, permeate and filter cake from these units was
performed for the units on bom of the streams. The
analytical results are summarized in Table D-1. Overall, the
results show the applicability of the technology to the acid
mine drainage; a reduction of four orders of magnitude of
some of the toxic metals was produced by the bench-scale
technology.
Table D-1. Treatability Test Results
Parameter
Aluminum
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium,
Total
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Molybdenum
Nickel
Potassium
Selenium
Silicon
Sodium
Thallium
Vanadium
Zinc
Conductivity
PH
Sulfate
Total Dissolved
Solids
Richmond Portal
Treated with Lime
Influent
(mg/L)
1.800
38
<2.0
0.60
1.8
13
250
<1.2
<1.0
160
14.000
<3.9
580
16
17
<1.4
230
<24
88
150
<22
1.6
1,800
270.000
1.1
55.000
94.000
Effluent
(mg/L)
<0.45
0.11
0.105
<.002
0.729
<0.004
480
<0.015
<0.015
0.059
0.057
<0.06
3.3
<0.002
0.252
<0.015
190
<0.025
1.89
130
<0.30
<0.012
<0.008
3,700
9.4
1,800
2.900
Old Number 8
Mine Seep Treated
with Lime
Influent
(mg/L)
680
0.18
<2.0
<0.16
<1.8
<0.34
110
<1.2
<1.0
140
1,800
<3.9
380
14
<3.2
<1.4
<3.3
<24
59
<6.0
<22
<0.87
61
18,000
2.6
8,900
15,000
Effluent
(mg/L)
<0.45
<.19
0.022
<0.002
0.229
<0.004
640
<0.015
<0.015
0.027
<0.007
<0.06
1.1
<0.002
0.237
<0.015
<0.050
<0.025
<1.38
6.5
<0.30
<0.012
0.014
3300
9.9
1,200
2,700
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D.2 Hazardous Waste Reduction
FMC Corporation, Fresno, California
This case study presents the use of a combination
EXXFLOW/EXXPRESS system to remove pesticides, heavy
metals and oils from a rinse liquid produced by the FMC
Corporation. The system is in use for recycling of the water
and for hazardous waste volume reduction.
D.2.1 Facility Operations
An EXXFLOW/EXXPRESS combination system is used.
The waste stream, at 10 to IS gpm, is adjusted to pH 11
prior to entering the EXXFLOW microfilter. Because of the
higher pH, the hazardous materials become less soluble and
are precipitated. The EXXFLOW microfilter concentrates
the hazardous constituents to twenty times the original
concentration and removes the oil emulsions present in the
waste. The concentrate stream is directed to the
EXXPRESS unit where it is dewatered to 45% solids by the
automatic tubular press. The liquid removed from the cake
by the press is recycled to the EXXFLOW feed. The
EXXFLOW recovers 99% of the water. The filtrate is
polished with a small activated carbon adsorption unit prior
to reuse by the plant
D.2.2 System Performance
Twenty to 50 gal/day of filter cake is produced from this
unit, as compared to the 10 to 15 gal/min of influent
Ninety-nine percent or better of all of the hazardous
constituents are removed by the system, as shown in Table
D-2. The system has been in use since 1989.
Table D-2. Removals of Hazardous Constituents
Constituent
Organochlorine
Petticide*
Organs
phosphorus
Pesticides
Carbarn ate
Pesticides
Total Piisticides
Total Metals (As,
Cr, Cu. Pb. Zn)
Oil and Grease
Raw Feed
Concentration
(Mg/L)
34330
191360
8.500
234,190
23.143
>S.OOO.OOO
Filtrate
Concentration
fog/L)
30.0
587.3
21.0
638.3
230
<25,000
Concentration
After Carbon
(pg/L)
0.07
030
None detected
037
-
-
D 2.3 Costs
The capital cost for mis technology application was
approximately $175,000; installation costs were $12.000.
The volume reduction as well as the production of a semi-
dry product significantly reduces the disposal costs for the
operation. The ability to reuse the water in the plant
providers an additional cost savings. Epoc estimates that a
cost sailings of $1.5 million per year is being achieved
versus disposal of the liquids as hazardous waste. As
hazardous liquids become more difficult to dispose of due to
new regulations, and the cost of water increases, the use of
this technology could provide substantial savings over the
long term.
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D.3 Groundwater Remediation
Talley Corporation, Newbury Park, CA
This case study describes the use of a combined EXXFLOW
and EXXPRESS unit to treat contaminated groundwater at
an abandoned manufacturing plant The groundwater was
detennined to contain hexavaknt chromium at 500 to 600
ppb and elevated levels of trichloroethylene. Fifty gpm of
pound water was formerly being pumped and treated with an
ion exchange system for removal of the chromium, while air
stripping was used to remove the trichloroethylene. EPOC
estimates that substituting the EXXFLOW/EXXPRESS unit
for the ion exchange significantly reduced the operating
costs. The EPOC system was installed in January of 1991.
See Figure D-l for a process schematic.
DJ.l Facility Operations
A single stage chemical reactor is used to precipitate the
hexavalent chromium. The precipitates are then removed
from the water using the EXXFLOW microfilter. The
EXXPRESS tubular Miter press is then used to dewater the
EXXFLOW reject so that less than 1 Ib/day is produced
while returning the liquids to the EXXFLOW feed. The
permeate from the EXXFLOW is then treated by the existing
air stripper for removal of the trichloroethylene. The
treatment system is interlocked with the groundwater pumps,
the air stripper and a chromium analyzer for the treated
water.
D.3.2 System Performance and Costs
The EXXFLOW treated water contains less than 10 ppb of
total chromium, well within the regulatory limit of 50 ppb.
No information on reliability is available for this system.
The cost for the equipment was approximately $150,000 and
installation costs were $12,000. The operating costs for this
treatment system are estimated at $0.25 per 1000 gal for
electrical power (12 HP at 460 VAC) and $0.02 per gal for
chemical consumption. Labor and maintenance costs were
not reported. EPOC estimates that the projected payback
time for their unit over the km exchange is less than twelve
months.
CHEMICAL DOSING
Aitsnwrat
pot TCI
EMQVAl
DISCHARGE
ROTATE
D07RE5J
nun
NESS
RDEl CAKE
Figure D-l. Talley Corporation Process Schematic
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D.4 Zero Discharge of Ceramics Waste
Duncan Enterprises, Fresno, CA
This ceramics factory produces a waste stream containing up
to 2 gm/1 of lead and other heavy metals and 2-5% w/w
suspended solids including ceramics fines, clays, paint
pigments, and binders. Since the cost of disposing of this
material was becoming prohibitive, recycling was
investigated. The solids and metals were being removed
through a rotary vacuum filter using diatomaceous earth
(DE) as a filter aid. The DE added nearly 50% to the waste
volume and precluded recycling of the solids.
D.4.1 Facility Operation
An EXXPRESS Automatic Tubular Press was used first in
the treatment train to dewater the high solids waste. The
filtrate from the EXXPRESS unit is treated to lower the pH
and precipitate the remaining heavy metal constituents. The
metal precipitates are removed from the liquid in an
EXXFLOW microfilter having a 20 gpm capacity. The
EXXFLOW produces a filtrate of high enough quality to be
recycled in the plant
The concentrate from the microfilter is added to the feed for
the EXXPRESS unit The filter cake from the EXXPRESS,
containing 50% solids, is dried and vitrified for reuse as
ceramic frit All waste in the unit is recycled so that no
disposal is required.
B.4.2 System Performance
The final filtrate water quality is compared with the raw feed
in Table D-3.
Table D-3. Concentration Comparison
Constituent
Sugpemfed Solids (gA)
Lead(rngA)
Cadmium (mg/1)
Cobalt (mg/1)
Zinc (nig/1)
Raw Feed
20-50
2000-6000
18
21
295
Filtrate
<0.01
<0.20
<0.05
<0.03
<0.05
Cake
50%
w/w
D.43 Costs
Epoc estimates that the unit saves over $500,000/year
compared to disposal costs. The EXXFLOW/EXXPRESS
unit hail been in operation since May of 1990.
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D.5 Industrial Waste Water
Commercial Aluminum Cookware, Toledo, OH
This case study presents the use of a combined EXXFLOW
and EXXPRESS microfiltration system to remove machine
oil. kerosene and particulars from process washwater. The
waste stream comes from a water wash and rinse removing
oil and dirt from aluminum cookware prior to a deionized
rinse and hard anodizing. The water contains up to 150
mg/L of oil and grease.
oil and grease content of the water is reduced from 150
mg/L to less than 5 mg/L. Since 5 mg/L is the discharge
limit for oil and grease for the stream, treatment with the
EXXPRESS unit would allow discharge of the effluent to
the sewer system. However, the water quality of the effluent
is also acceptable for reuse in the process washer and 99%
of the water is now recycled in this manner.
D.5.1 System Operation
EXXFLOW microfiltration was chosen to treat the
wastewater to recycle quality. An inert powdered absorbent
is added to the water, binding to the oil and grease and
allowing them to be removed by the microfUter. The
microfilter also removes metal fines and other particulates
present in the waste stream. Up to 40 gpm of washwater are
treated by the system. The solids from the EXXFLOW filter
are concentrated further in an EXXPRESS tubular filter
press. The resultant filter cake has 30 to 40% w/w of solids.
D.5.2 System Performance
Use of the EXXFLOW process removes the metal fines,
measured at 10 to 50 mg/L, to below detectable levels. The
D.5.3 Costs
While no detail cost data are available for this case study,
EPOC estimates that the 40 gpm system as installed returned
its total cost within the first three months of operation, as
compared to off-site disposal of the contaminated water.
D.5.4 Reliability
This system was installed in July of 1990 and continues to
be in operation. No other reliability information is available.
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6U.S. GOVERNMENT PRINTING OFFICE: 1995-653-484
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