vvEPA
                                  United States
                                  Environmental Protection
                                  Agency
                EPA/540/MR-95/511
                June 1995
                                  SUPERFUND INNOVATIVE
                                  TECHNOLOGY EVALUATION
                                   Demonstration  Bulletin
                        Zenon  Cross-Flow Pervaporation Technology

                                       ZENON Environmental, Inc.
Technology Description: Pervaporation is a process that employs
a membrane to remove volatile organic compounds (VOC) from
aqueous matrices. Figure 1 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 pref ilter 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 a
pervaporation module containing dense polymeric membranes.

The membrane material  is a nonporous organophilic polymer,
such as silicone rubber, formed into capillary fibers measuring less
than  1 mm in diameter. Silicone  rubber is highly permeable to
organic compounds and resistant to degradation.  The capillary
fibers are aligned parallel on a plane and spaced slightly apart. This
arrangement of capillary fibers forms one membrane layer.

Separate membrane layers are aligned in series, with the interior
of the capillary fibers exposed to a vacuum (about 11b/in2, 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.

The organophilic composition of the membrane causes organics to
adsorb to the membrane (capillary fibers). The organics migrate to
the interior of the capillary fibers and are then extracted from the
membrane by the vacuum. This organic migration into the fibers
creates a concentration gradient that tends to facilitate transport.
Contaminated water passing through the pervaporation module is
depleted of organics and exits the ZENON system for reuse or
discharge.

Organic vapor and small amounts of water extracted from  the
contaminated water through the membranes 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 permeate condenser,  organics are kept in
solution, thus minimizing air releases.

The  liquid 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 containment vessel to storage
while aqueous phase permeate can either  be returned to  the
pervaporation module for further treatment or removed for disposal.

Waste Applicability: Cross-flow pervaporation can be applied to
aqueous matrices contaminated with  liquids containing VOCs
such as solvents, degreasers, and gasoline. 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
                                                               Carbon Filter
                                                                                    Carbon Filter
                                                                                   '—D-*
                    - Tank Air Vent
                                                                           iCarbon Filter
       Contaminated
         Water
j
-»
Eq


jaliza
Tank
Polymeric
Prefilter Membranes
I Moat \
Pv^tnnor A,
u n^rT , ll I
> M U >W '
Feed Pump J ^'^ Tp
tion / T
"wate? Carbon Filters ^
i—9 — n-a-Q»To
1 Discharge
•^ — > — Condenser l_


V» Vacuum Pump and
Outlet to Vent
Carbon Water
and Organics For Recycle,
> 	 • Disposal, or
Further Treatment
f Permeate
                                 PERVAPORATION MODULE
 Figure 1. Zenon Cross-Flow Pervaporation System
                                                                                          Printed on Recycled Paper

-------
                                  United States
                                  Environmental Protection
                                  Agency
                EPA/540/MR-95/511
                June 1995
 oEPA
                                  SUPERFUND INNOVATIVE
                                  TECHNOLOGY EVALUATION
                                   Demonstration  Bulletin

                        Zenon  Cross-Flow Pervaporation Technology
                                       ZENON Environmental, Inc.
Technology Description: Pervaporation is a process that employs
a membrane to remove volatile organic compounds (VOC) from
aqueous matrices. Figure 1 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 pref ilter 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 a
pervaporation module containing dense polymeric membranes.

The membrane material  is a  nonporous organophilic polymer,
such as silicone rubber, formed into capillary fibers measuring less
than  1 mm in diameter. Silicone  rubber is highly permeable to
organic compounds and resistant to degradation. The capillary
fibers are aligned parallel on a plane and spaced slightly apart. This
arrangement of capillary fibers forms one membrane layer.

Separate membrane layers are aligned in series, with the interior
of the capillary fibers exposed to a vacuum (about 11b/in2, 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.

The organophilic composition of the membrane causes organics to
adsorb to the membrane (capillary fibers). The organics migrate to
the interior of the capillary fibers and are then extracted from the
membrane by the vacuum. This organic migration into  the fibers
creates a concentration gradient that tends to facilitate transport.
Contaminated water passing through the pervaporation module is
depleted of organics and exits the ZENON system for reuse or
discharge.

Organic vapor and small amounts  of water  extracted from the
contaminated water through the membranes  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 permeate condenser,  organics are kept  in
solution, thus minimizing air releases.

The  liquid 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 containment vessel to storage
while aqueous phase permeate can either  be returned to the
pervaporation module for further treatment or removed for disposal.

Waste Applicability: Cross-flow pervaporation can be applied to
aqueous matrices contaminated with  liquids containing VOCs
such as solvents, degreasers, and gasoline. 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
                                                               Carbon Filter
                                                                                    Carbon Filter
                                                                                       O-*
                                                                                          For Recycle,
                                                                                          Disposal, or
                                                                                        Further Treatment
               Equalization
                 Tank
                                                     Permeate
                                 PERVAPORATION MODULE
 Figure 1. Zenon Cross-Flow Pervaporation System
                                                                                          Printed on Recycled Paper

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