United States
                        Environmental Protection
                        Agency
Office of
Research and Development
Cincinnati, OH 45268
EPA/540/R-95/511a
August 1995
SEPA
Abstract

The U.S. Environmental Protection Agency (EPA) has
focused on  policy, technical, and informational  issues
related to exploring and applying new technologies to
Superfund  site  remediation.  One EPA initiative to
accelerate the development, demonstration, and use of
innovative technologies for site remediation  is the
Superfund Innovative Technology Evaluation (SITE)
Program.

EPA SITE technology capsules summarize the latest
information  available on selected innovative treatment
and site remediation technologies. The capsules assist
EPA remedial  project managers, EPA on-scene
coordinators, contractors, and other remedial managers
in the  evaluation of site-specific chemical and physical
characteristics to determine a technology's applicability
for site remediation.

This capsule contains information on the cross-flow
pervaporation technology developed  by ZENON
Environmental, Inc. (ZENON). The technology is designed
to  remove volatile organic compounds (VOC) from
aqueous media. In early 1995, a full-scale ZENON system
was evaluated at a former disposal area on Naval Air
Station North Isjand  (NASNI) in Coronado,  California.
Groundwater  at the site is contaminated with
trichloroethene (TCE) and other organic compounds.
Results of the demonstration are summarized in the
 Performance Data section of this capsule. Results from
 a 1993 pilot-scale SITE demonstration of the technology
 in Burlington, Ontario, Canada, are also summarized in
 the Performance Data section.

 Introduction

 The ZENON pervaporation technology is a membrane-
 based process  that removes VOCs from aqueous
 matrices.  The ZENON cross-flow pervaporation
 technology uses an organophilic membrane made of
 nonporous silicone rubber, which is permeable to organic
 compounds but  highly resistant to degradation.  The
 composition of the membrane causes organics in solution
 to adsorb to it; the organics then diffuse through  the
 membrane by a vacuum and condense into a highly
 concentrated liquid  called permeate.  The permeate
 separates into aqueous and organic phases. The organic
 phase can either be disposed of or sent off site for further
 processing to recover the organics. The aqueous phase
 is sent back to the pervaporation unit for retreatment.

 The ZENON technology effectively removes organic
 contamination from groundwater and other  aqueous
 waste streams.  The  technology is  not practical for
 reducing VOC concentrations to most regulatory limits,
 notably drinking  water standards. It  is best suited for
 reducing high concentrations of VOCs to levels that can
 be  reduced further and more economically by
 conventional treatment technologies,  such as carbon
                          /TV
                         u£&  Printed on Recycled Paper
                                      SUPERFUND  INNOVATIVE
                                      TECHNOLOGY EVALUATION

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 adsorption. According to the developer, once the ZENON
 technology is installed  and equilibrated, it requires
 minimal support from on-site personnel.

 The full-scale  SITE demonstration  of the ZENON
 technology took place at a former disposal area referred
 to as Site 9, on  NASNI  in  Coronado,  California.  The
 demonstration was performed as a cooperative effort by
 EPA,  the  U.S. Navy, ZENON,  and  Canadian
 environmental  agencies.   Site 9 groundwater is
 contaminated with VOCs, primarily TCE. The purpose
 of the demonstration was to (1 ) evaluate the technology's
 removal efficiency for TCE concentrations in groundwater,
 and (2) determine if TCE concentrations could be reduced
 to the federal maximum contaminant level (MCL) for TCE
 of 5 micrograms per liter
The demonstration  results showed that the ZENON
system removed TCE from groundwater by an average
of 97.3 percent.  Sixteen of 18 comparisons of treated
water samples to untreated samples showed average
TCE removal efficiencies of 99.3 percent. However, the
average TCE concentration in the treated water was
approximately 1 ,380 jug/L, which did not meet the federal
MCL.

The ZENON cross-flow pervaporation technology was
also evaluated based on the nine criteria used for decision
making in the Superfund feasibility study (FS) process.
Table 1 presents the results of the evaluation.

Technology Description

The ZENON pervaporation technology involves modules
containing  dense  polymeric membranes.   Each
membrane consists of a nonporous organophilic polymer,
similar to silicone rubber, formed into capillary fibers
measuring less than 1  millimeter in diameter. Silicone
rubber exhibits high selectivity toward organic compounds
and is highly resistant to degradation. The capillary fibers
are aligned in parallel on  a plane and spaced  slightly
apart.  This arrangement of capillary fibers forms one
membrane layer.

Separate membrane layers are aligned in series, as
shown in Figure  1 , with the interior of the capillary fibers
exposed to a vacuum (about 1  pound per square inch
absolute). The number of membranes used in a particular
system depends on  expected flow rates, contaminant
concentrations  in the  untreated water, and target
concentrations for contaminants in the  treated water.
Process temperatures  may be elevated to improve
treatment; however, temperatures are kept at or below
165°F (75 °C).
 The organophilic composition of the membrane causes
 organics to adsorb into the capillary fibers. The organics
 migrate to the interior of the capillary fibers and are then
 extracted from the membrane by the vacuum.

 Figure 2 displays a schematic diagram of the ZENON
 cross-flow pervaporation system in  a typical  field
 application.  Contaminated water is  pumped from an
 equalization tank through a 200-micron prefilter to remove
 debris and silt particles, and then into a heat exchanger
 that raises the water temperature to about 165 °F (75 °C).
 The heated contaminated water then flows into the
 pervaporation module. Organics and small amounts of
 water are  extracted from the contaminated  water, and
 treated  water exits the pervaporation  module and is
 discharged from the system.

 The extracted  organics and small  amount of water is
 called permeate. As the permeate exits the membranes,
 it is drawn into a condenser by the vacuum, where the
 organics and any water vapor are condensed. Because
 emissions are vented from the system  downstream of
 the condenser,  organics are kept in  solution, thus
 minimizing air releases.

 The condensed permeate contains highly concentrated
 organic compounds and has a significantly reduced
 volume  compared to the untreated water.  Because of
 this high concentration, the liquid permeate generally
 separates  into aqueous and organic phases, rendering
 the organic fraction potentially recoverable. The organic
 phase permeate is pumped from the condenser to
 storage, while aqueous phase permeate can either be
 returned to the pervaporation module for further treatment
 or removed for disposal.

 Technology Applicability

 The ZENON  cross-flow pervaporation  technology
 removes VOCs from aqueous matrices,  such as
 groundwater, wastewaters, and leachate. The technology
 can treat a variety of concentrations; however, it is best
 suited for reducing high concentrations of VOCs to levels
 that can be reduced further and more economically by
 conventional treatment technologies, such as carbon
 adsorption.  The technology can also remove a number
 of semivolatile organic compounds (SVOC) and
 petroleum hydrocarbons.  Both the pilot-scale  and
full-scale demonstrations have evaluated the ZENON
technology's treatment of contaminated groundwater.

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Table 1: Evaluation Criteria for the ZENON Technology
             CRITERION


1  Overall Protection of
   Human Health and the
   Environment
           ZENON TECHNOLOGY PERFORMANCE


Provides   short-   and   long-term    protection   by   reducing
contaminants in water.  Can be part of a pump-and-treat system
to  prevent   further  groundwater  contamination  and  off-site
migration.     Worker  protection  is   required  when  handling
concentrated  permeate.
2  Compliance with Federal ARARs
3   Long-Term Effectiveness
    and Performance
Requires   compliance   with   National   Pollutant   Discharge
Elimination  System  (NPDES)  and  Safe  Drinking  Water  Act
(SDWA)   limitations  for  discharge.   Storage  of concentrated
permeate  requires compliance with Resource  Conservation  and
Recovery  Act (RCRA)  hazardous waste  storage  requirements.
Emission  controls are  needed to  ensure compliance  with  air
quality standards.

Effectively  removes   groundwater  contaminants.     Involves
disposal of some residuals (wastewater and  permeate).
4   Reduction of Toxicity,
    Mobility, or Volume
    Through Treatment


5   Short-Term Effectiveness
 Reduces  the  toxicity  of  groundwater  by  the  removal  of
 contaminants.
 Contaminants  are   removed  upon  completion   of  treatment.
 Presents  potential short-term risks to workers from moving and
 handling of concentrated permeate.
 6  Implementability
 Easy  to   implement  and  transport.    Requires   minimal  site
 preparation and utilities, and minimal operational support.
 7  Cost
 ZENON estimates treatment costs from $2.00 to $4.00 per 1000
 gallons of contaminated water.
 8   Community Acceptance
 The  small  risk to the  community  and permanent removal  of
 contaminants make public acceptance of this technology likely.
 9   State Acceptance
 If remediation  is conducted as part of  RCRA corrective actions,
 state regulatory agencies may require permits.
    Notes:
      a   Applicable or relevant and appropriate requirements
      b   Actual cost of a remediation technology is highly specific and dependent on the original and target cleanup levels,
         contaminant concentrations, groundwater characteristics, and volume of water.

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                                                                      —VOCs —
                                                                      To Condenser
                              Figure 1: ZENON Cross-Flow Pervaporation Module
A full-scale ZENON pervaporation system is easily
transportable and can fit in a small semi-trailer.  It is a
stand-alone technology but can be used in series with
other conventional technologies such as soil washing,
carbon adsorption, or flocculation  with solids removal.
Contaminated aqueous media can be pumped directly
to the pervaporation module; however, it is recommended
that water be equalized in a bulk tank before entering the
system.  Depending  on local pretreatment standards,
treated water exiting the ZENON system  may be
discharged to a publicly owned treatment works (POTW).
To comply  with NPDES or SDWA limitations, further
treatment with a separate technology is usually required.

Pervaporation provides an alternative approach to treating
organic-contaminated water at sites where conventional
air stripping or carbon adsorption are currently used.
Unlike air stripping, pervaporation releases low amounts
of VOCs to the outside air.  Also, the pervaporation
membranes do not require replacement and disposal,
unlike activated carbon. Because contaminants pass
through the membrane, it can be used for an extensive
period of time (years) before degradation requires
replacement.
Technology Limitations

As noted previously, the prefilter prevents solids from
reaching the  pervaporation module and inhibiting the
movement of organics through the membrane.  Solids
can clog the prefilter, requiring it to be cleaned frequently.
Influent with a high alkalinity or high amounts of calcium
or iron can cause scaling of the system. In these cases,
anti-scalents can be added to the untreated water as a
preventive measure.

The  ZENON  technology does not remove  inorganic
contamination and can only remove a limited number of
SVOCs and petroleum hydrocarbons.  Dissolved heavy
metals in groundwater have not adversely affected the
treatment ability of the technology.

VOCs with water solubilities of less than 2 percent are
generally suited for removal by pervaporation. Highly
soluble organics, such as alcohols, are not effectively
removed by a  single-stage pervaporation process. Also,
low-boiling VOCs, such as vinyl chloride, tend to remain
in the vapor phase after moving through the condenser.

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 Contaminated
    Water   ~
                                                                            -CH>
                                                                         Carbon Filter
                       o->
                    Carbon Filter
                 "Tank Air Vent
                                                                                       D Carbon Filter
           Egualization
              Tank
                                  PERVAPORATION MODULE
                                 Prefilter
                                        Heat
                                      Exchanger
                          Feed Pump
                                                                Treated ^
                                                                 Water  Carbon Filters
                                                            Permeate
   To
Discharge L
           Vacuum Pump and
       K-Q-
Water and
 Organics   For Recycle,
          Disposal, or
        Further Treatment
Figure 2: ZENON Cross-Flow Pervaporation System

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 For elevated concentrations of most low-boiling VOCs, a
 carbon filter placed on the vacuum vent ensures that
 contaminants are not released to the outside air.

 The system  has proven effective in  reducing VOC
 concentrations in groundwater to near MCLs. However,
 lowering concentrations to below MCLs may require
 multiple passes through the pervaporation module, which
 can prove  impractical  when compared  to  other
 technologies, such as carbon  adsorption.  Water
 containing high concentrations of contaminants, including
 light nonaqueous phase  liquids  (LNAPL) and dense
 nonaqueous phase liquids (DNAPL), also require multiple
 passes through the module. To decrease the number of
 passes, LNAPLs and DNAPLs should be removed from
 water before it enters the system.

 Water quality standards normally will riot allow water
 exiting the ZENON system to be discharged directly into
 surface water bodies. Depending on local standards,
 treated water may be acceptable for discharge to a local
 POTW. During the demonstration at NASNI, treated water
 required additional treatment through a series of two 1,000-
 pound carbon filters for polishing.  VOC concentrations
 were then monitored with an on-site gas chromatograph
 (GC), and the water was discharged to the sanitary sewer.

 The ZENON system tested at NASNI could achieve  a
 maximum flow rate of 11 gallons per minute (gpm), which
 is the largest  capacity of the technology to date.  Sites
 requiring treatment at higher flow rates will require multiple
 systems or additional pervaporation modules.

 Process Residuals

 The ZENON  system generates two waste  streams:
 treated water and concentrated permeate.  As noted
 above, treated water may require further treatment to
 meet local or site-specific discharge requirements.

 Permeate usually separates into an organic and an
 aqueous phase. The organic phase permeate is pumped
 from the  condenser to storage, while aqueous phase
 permeate can either be returned  to the  pervaporation
 module for further treatment or removed for  disposal.
 During the NASNI demonstration, the system treated
 about 65,000 gallons of  contaminated groundwater
 producing about four 55-gallon drums of permeate. The
 aqueous permeate was pumped from the drums through
the 1,000-pound carbon filters  and discharged to the
 sanitary sewer.  The organic permeate was transferred
to one 55-gallon drum which  was sent  to a treatment
facility for incineration.
 Depending on the application and local regulations,
 personal protective equipment, along with field laboratory
 waste, may require disposal at a licensed disposal facility.

 Site Requirements

 Because a full-scale ZENON cross-flow pervaporation
 system is shipped to sites in a semi-trailer, access roads
 at treatment sites are necessary. The ZENON system is
 mounted in a steel enclosure measuring about 12 by
 7 by 7 feet. The enclosure is slightly elevated from the
 ground, allowing  it to be moved with a large forklift or a
 small crane. The enclosure must be placed on a hard
 surface, preferably an asphalt or concrete pad, although
 packed soil will support it.

 The ZENON system requires utility hook-ups for electricity
 and water.  A full-scale ZENON  system capable of
 11 gpm requires 460-volt, 3-phase, 15-ampere service.
 During shakedown, clean water is necessary to verify
 that all components are operating correctly before
 contaminated water enters  the system.  Clean water is
 also needed for decontaminating process equipment and
 for health and safety. Permeate must be stored in drums
 or bulk tanks, which under  RCRA regulations, requires
 secondary containment and possibly  permits.  A
 receptacle for treated water, such as bulk tanks or sewer
 lines, is also necessary.  A small office trailer and a
 telephone are recommended for moderate- to long-term
 operations.

 Performance Data

 The ZENON cross-flow pervaporation technology has
 been demonstrated under the SITE Program at the pilot-
 scale and full-scale levels.  The objectives of  both
 demonstrations were to determine the technology's ability
 to remove VOCs from contaminated groundwater and to
 determine the percent removal for each contaminant of
 concern. Results for each demonstration are summarized
 in the following sections.

 Pilot-Scale Demonstration

The pilot-scale demonstration of the ZENON technology
was performed in October 1993, at a small site just south
of Burlington, Ontario,  containing  groundwater
contaminated with petroleum hydrocarbons.  Benzene,
ethylbenzene, toluene, and total xylenes (BTEX) were
the critical contaminants. Demonstration objectives were
achieved by collecting untreated and treated water eight
times  over an 8-hour period, while the system operated

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at a flow rate of 0.2 gpm. The system was equipped with
a small carbon filter to minimize releases of VOCs from
the vacuum vent of the system to the surrounding air. A
photoionization detector was used to monitor the air
released from the vacuum vent.

Analytical  results  indicated that BTEX concentrations
were significantly reduced  in treated groundwater
samples compared to untreated samples (see Table 2).
Removal efficiencies averaged 98 percent.  No  VOC
releases from the vacuum vent after carbon filtration were
detected during the pilot-scale demonstration.

Full-Scale  Demonstration

The full-scale demonstration of the ZENON technology
was performed during February 1995, at a former waste
disposal area at NASNI, referred to as Site 9. Site 9 was
used for over 40 years as a disposal area for a wide range
of wastes; however, organics are the primary groundwater
contaminants.  TCE was selected as the contaminant of
concern for  the  demonstration  because of its
identification, through groundwater  sampling, as the
primary contaminant at Site 9, at varying concentrations
among monitoring wells.

During the initial  stages  of  the demonstration,
groundwater was pumped from a series of  existing
monitoring wells at the site to two 21,000-gallon  steel
bulk tanks for equalization. Rust particles from the interior
of the tanks caused the prefilter to easily clog, requiring
frequent cleanings.  The particles also caused fouling
and scaling  problems with the  pervaporation  module,
reducing its treatment efficiency. Eventually, groundwater
was  pumped directly from the monitoring wells to the
system; however, because of high calcium bicarbonate
concentrations in the  groundwater, scaling of the
pervaporation module continued.  After attempts with a
variety of chemicals,  ZENON settled with an anti-scalent
similar to zinc phosphate, which proved fairly effective.

TCE influent concentrations were varied by altering the
flow rates into the  system from the selected wells.
Demonstration objectives were achieved by collecting
samples of untreated and treated groundwater over five
8-hour sampling runs; air samples were collected directly
from the vacuum vent of the system before and after a
carbon filter.  Flow rates of the system ranged from 2 to
11 gpm; influent TCE concentrations ranged from 33 to
240  milligrams per  liter (mg/L).  After the third run,
sampling  was delayed to allow  cleaning  of the
pervaporation module.  Sampling ended after 4 hours
into the fifth run because of a corroded stainless steel
tube on the pervaporation module.

Table 3 presents analytical  results for groundwater.
Removal efficiencies  for  TCE  averaged  about
97.3 percent. The highest levels of contaminant removal
were achieved when the system operated at a flow rate
of about 5.5 gpm with an influent concentration of about
230 mg/L of TCE. Removal efficiencies were lowest when
the system operated at about  2 gpm with an  influent
concentration of about 40 mg/L of TCE. Although the
system significantly reduced TCE concentrations in the
groundwater to an average of 1.37  mg/L (1,370 (JQ/L),
the federal MCL of 5 /L/g/L was not achieved.

VOC releases from the vacuum vent of the system ranged
from 2,500 milligrams per cubic meter (mg/m3) to 21,000
mg/m3. The data indicate that VOC releases from the
vent increased with higher VOC influent concentrations;
varying flow rates appeared to have little affect on air
releases.  Analytical results  for air  released from the
vacuum vent of the system are shown  in Table 4. Samples
were also taken from the vent after  air was allowed to
pass through a 55-gallon carbon filter. Analytical results
indicate that the carbon was 99.9 percent effective in
removing the VOCs.

Technology Status

The  SITE demonstration at NASNI represents the first
full-scale use of the ZENON cross-flow pervaporation
technology.  As noted, the full-scale  system is portable
and  requires minimal site preparation.  Multiple
pervaporation modules can be added to the system to
accommodate a variety of sites. The technology is best
suited for reducing high concentrations of VOCs to levels
that can be reduced further and more economically by
conventional treatment technologies.  The technology
provides an  alternative  approach to  treating
organic-contaminated water at sites where conventional
treatment technologies are used, such as air stripping or
carbon adsorption.

Disclaimer

The  data presented  in this technology  capsule have
passed internal laboratory quality assurance checks but
have not been  reviewed by EPA Risk Reduction
Engineering Laboratory Quality Assurance personnel.

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 Table 2: BTEX Concentrations in water

Sample
Number Untreated
Concentration
(pg/L)
1 700
1D 720
2 340
3 360
4 360
5 700
6 370
7 370
8 650
Average 509
Benzene
Treated
Concentration
(M9fl-)
11
6
11
11
7
9
8
10
8
9

Percent
Removal
98%
99%
97%
g"?o/
98%
99%
98%
97%
99%
98%

Untreated
Concentration
(M9/L)
150
150
110
110
110
130
120
130
120
113
Ethylbenzene
Treated
Concentration
(M9/L)
2
1
3
2
2
2
2
2
2
2

Percent
Removal
99%
99%
97%
98%
98%
99%
98%
99%
98%
98%

Untreated
Concentration
(M9/L)
490
500
260
280
27Q
450
290
290
400
358
Toluene
Treated
Concentration
(M9/L)
6
4
7
6
4
5
5
6
5
5

Percent
Removal
99%
99%
97%
98%
99%
99%
98%
98%
99%
98%

Untreated
Concentration
(H9/L)
820
840
570
630
650
800
670
700
700
709
Total Xylenes
Treated
Concentration
(pg/L)
13
8
14
12
9
11
11
12
11
11

Percent
Removal
98%
99%
98%
98%
99%
99%
98%
98%
98%
98%
Note:
  D   Duplicate sample

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             Table 3: TCE Concentrations in water
4 verage
Total Average Percent Removal
Untreated Concentration
(mg/L)
40
43
33
42
40
41
44
48
48
42
33
35
38
37
36
220
220
240
240
230
130
120
125

Treated Concentration
(mg/L)
0.17
1.0
3.8
11
3.9
ND"
0.09
0.16
0.19
0.11
0.32
0.27
0.22
0.24
0.26
0.45
0.40
0.51
0.46
0.46
2.7
2.7
2.7

Percent Removal
99.5%
97.7%
88.5%
733%
89.9%
>993%
993%
99.7%
99.6%
99.8%
99.0%
992%
99.4%
99.4%
993%
993%
993%
993%
993%
993%
973%
973%
97.9%
97.3%
            Notes:
              a    A sampling run is defined as one 8-hour period at a given flow rate.
              b    Not detected.
              c    Sampling run was abbreviated due to system failure.

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    Table 4: TCE Concentrations in Air
                   Average
Groundwater TCE Untreated Treated
Run Concentration Flow Rate Grab Concentration Concentration *> Percent
Number (mg/L) (gpm) Number (mg/m>) (mg/m>) Removal
1a 40 2.10-2.15 1 6,100 0.02
2 5,500 0.05
2 42 5.16-5.21 1 3,700 0.02
2 2,500 ND<=
3 36 1 7,300 ND
2 7,200 ND
4 230 546 1 18,000 0.17
2 20,000 0.01
5d 125 11.18-11.23 1 21,000 0.71
Average 95 10,100 0.11
99.9%
99.9%
99.9%
>99.9%
>99.9%
>99.9%
99.9%
99.9%
99.9%
99.9%
   Notes:
      a   A sampling run is defined as one 8-hour period for a given flow rate.
      b   Concentration after vented air passed through a carbon filter.
      c   Not detected
      d   Sampling run was abbreviated due to system failure.


Sources of Further Information
Ron Turner
EPA Project Manager
U.S. EPA National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
(513) 569-7775 FAX: (513) 569-7620

Philip Canning
Manager, Process Engineering
ZENON Environmental, Inc.
845 Harrington Court
Burlington, Ontario, Canada L7N 3P3
(905) 639-6320 FAX: (905) 639-1812
                                                10

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