ASTM F1525-96(2001)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:F1525–96 (Reapproved 2001)
Standard Guide for
Use of Membrane Technology in Mitigating Hazardous
Chemical Spills
This standard is issued under the fixed designation F1525; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope not pass through the membrane is called concentrate, while the
term retentate is more commonly used for ultrafiltration and
1.1 This guide covers considerations for the use of mem-
microfiltration.
brane technology in the mitigation of dilute concentrations of
3.1.2 crossflow filtration—a filtration process in which the
spilled chemicals into ground and surface waters.
feed flows almost parallel to the filter or membrane surface. It
1.2 This guide addresses the application of membrane
is also called tangential flow.
technology alone or in conjunction with other technologies.
3.1.3 flux—a measure of the rate at which the permeate (or
1.3 The values stated in SI units are to be regarded as the
filtrate) passes through the membrane per unit area of mem-
standard. The values given in parentheses are for information
2 3 2
brane. It is reported in units of L/m /day, m /m /day, or
only.
gal/ft /day.
1.4 This standard does not purport to address all of the
3.1.4 fouling—the accumulation of unwanted deposits or
safety concerns, if any, associated with its use. It is the
scales on a membrane that results in a flux reduction.
responsibility of the user of this standard to establish appro-
3.1.5 Langelier Saturation Index (LSI)—a method used to
priate safety and health practices and determine the applica-
determine the calcium scaling potential, that is, calcium
bility of regulatory limitations prior to use. In addition, it is the
carbonate of a membrane at concentrations below 5000 ppm
responsibility of the user to ensure that such activity takes
TDS.
place under the control and direction of a qualified person with
3.1.6 membrane technology—separation of the components
fullknowledgeofanypotentialorappropriatesafetyandhealth
of a fluid by means of a pressure gradient and a semipermeable
protocols.
membrane. The various classes of membrane technology are
2. Referenced Documents differentiated primarily by the size or molecular weight, or
both, of rejected material. The main divisions are (1) micro-
2.1 ASTM Standards:
filtration (MF), (2) ultrafiltration (UF), (3) nanofiltration (NF),
F1127 Guide for Containment of Hazardous Material Spills
and (4) reverse osmosis (RO).
by Emergency Response Personnel
3.1.7 microfiltration (MF)—a pressure-driven process
3. Terminology
whereby a contaminated liquid stream is separated using a
filtration process involving a compatible membrane. Dead-
3.1 Definitions of Terms Specific to This Standard:
endedandcrossflowtechniquesareused.Suspendedsolidsand
3.1.1 concentrate, retentate—in reverse osmosis and nano-
macromolecules are removed on the basis of size. Pore size is
filtration,respectively,theportionofthefeedsolutionthatdoes
normally 0.1 to 5.0 µm, and operating pressures usually range
from 20 to 350 kPa (3 to 50 psig). Membrane materials, such
as polypropylene, polytetrafluoroethylene (PTFE), and metal
This guide is under the jurisdiction of ASTM Committee F20 on Hazardous
oxides, are frequently less susceptible to chemical degradation
Substances and Oil Spill Response and is the direct responsibility of Subcommittee
than those used for other branches of this technology.
F20.22 on Mitigation Actions.
3.1.8 nanofiltration (NF)—a pressure-driven process
Current edition approved April 10, 1996. Published June 1996. DOI: 10.1520/
F1525-96R01.
whereby a contaminated liquid stream is separated and purified
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
by a process involving filtration, diffusion, and chemical
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
potential across a compatible membrane. Divalent and multi-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. valent species with a molecular weight above 80 are removed
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F1525–96 (2001)
as are uncharged and univalent molecules with a molecular hazardousmaterialsthathaveenteredsurfaceandgroundwater
weight above 200. Operating pressures normally run between as the result of a spill. Membrane technology may be applied
1380 and 2760 kPa (200 and 400 psig). alone or in conjunction with other treatment techniques, as
3.1.9 osmotic pressure—as related to membrane technol- follows:
ogy, the pressure that must be applied to the more concentrated 4.1.1 Different types of membrane are used in series with
solution to halt flow of the solvent from the less concentrated filters to treat highly contaminated solutions reaching concen-
solution through a semipermeable membrane into the more tration levels of several parts per million of organic and
concentrated side. inorganic materials.
3.1.10 permeate, filtrate—the stream that has passed 4.1.2 Different types of membranes are applied in series to
through the membrane and is therefore free of, or has a much treat very dilute concentrations (parts per billion level) of
reduced concentration of, contaminants. Permeate is com- organic and inorganic compounds. Each membrane type has
monly used for the treated water obtained from nanofiltration the ability to remove specific compounds, thus producing a
and reverse osmosis processes, while filtrate is more com- concentrated fraction. This fraction may require final off-site
monly used for the treated fluid obtained by ultrafiltration and treatment but provides a significant reduction in transportation
microfiltration operation. costs due to the large volume reduction achieved.
3.1.11 pervaporation (PV)—a vacuum-driven membrane 4.1.3 Membranes may be used in conjunction with destruc-
process applicable to the separation of liquid mixtures. During tion technologies such as advanced oxidation processes
the separation, the dissolved, more volatile constituents are (AOPs).This method is recommended for dilute solutions.The
removed from a less volatile carrier stream, as a vapor, through membrane technology portion concentrates the compounds to
a semipermeable membrane and then condensed on the down- an optimum level for AOP destruction.
stream side. This energy-intensive process is still in the
5. Constraints on Usage
development stage, but it has the potential of being a very
5.1 General—Application of membrane technology to the
promising spill mitigation technology.
cleanup of spills results in the generation of two streams. The
3.1.12 reverse osmosis (RO)—a pressure-driven process in
first stream is treated and has a reduced concentration of
which a liquid stream is separated and hence purified by
contaminants, while the second is concentrated and has an
passingitoverthesurfaceofasemipermeablemembrane.Both
increased concentration of contaminants. This concentrated
dissolved and suspended materials in a molecular weight range
stream must be destroyed, reprocessed, or disposed of in an
from 40 to 200 are removed, with charged species being
appropriate manner. There may also be constraints that are
removed more easily. In the case of nonpolar molecules,
created by the physical and chemical sensitivity of membranes
molecular structure “bulkiness” becomes important. Some are
and, as a result, characteristics of a membrane system must be
rejected well with a molecular weight of 60, while others with
taken into consideration whenever membrane units are used.
a molecular weight of 100 are not. Differences among mem-
These considerations are described as follows.
brane material can be very important in this aspect. This
5.1.1 Membrane Material:
process discriminates between solutes on the basis of their
5.1.1.1 The material used to construct the membrane is
ability to either (1) preferentially adsorb onto the membrane
crucial to its success. In general, for spill remediation, the UF,
pore surfaces and move through the membrane pores by
NF, and RO membranes require materials that have a good
capillary action, or (2) dissolve in and diffuse through the
temperature and pH resistance, as well as chemical stability, to
membrane. Reverse osmosis uses applied pressures between
ensure that the membrane is unaffected by the solution being
1380and10 350kPa(200and1500psig).Astheconcentration
treated. The increasing demands on the performance of mem-
difference between the solutions on the two sides of the
brane materials are exceeding the capability of organic poly-
membrane increases, the osmotic pressure of the solution
mers currently available. Consequently, inorganic membranes
increases and, in turn, the applied pressure requirement. In
have been developed in order to satisfy the need for better
general,solutionscontainingorganicandinorganiccompounds
performance. Today, high-quality organic and inorganic mem-
ranging from low ppm up to 55 000 ppm are commonly treated
branes are commercially available.
with this technique.
5.1.1.2 Inorganic membranes are classified in four groups:
3.1.13 semipermeable membrane—membranes that are se-
ceramic, carbon, metal, and polymer analog. Many develop-
lective in the components that they allow to pass through them.
ments in inorganic membranes have been achieved, but many
3.1.14 ultrafiltration (UF)—a pressure-driven process
inconveniences have yet to be overcome, such as their high
whereby a contaminated liquid stream is separated and purified
cost and low surface area/volume, which retards the expansion
by a crossflow filtration process involving a compatible mem-
of their application. In the case of organic materials, several
brane. Suspended solids and dissolved molecules in the 500 to
kinds of polymers are used that allow for the development of
300 000 molecular weight range are removed mainly on the
membranes with various properties. The following improve-
basis of size. This represents a membrane that has a pore size
ments might be noticed: lower cost, longer life time, lower
ranging between 0.0015 and 0.2 µm. Ultrafiltration uses
replacement rates, reduced chemical consumption, reduced
pressures of 105 to 1380 kPa (15 to 200 psig).
operating pressure for given flux level, use in a broader range
4. Significance and Use
of pH, higher ion rejection, easier cleaning due to effective
4.1 General—Thisguidecontainsinformationregardingthe foulant removal and reduced biological attack, lower energy
use of membrane technology to recover and concentrate consumption, as well as reduction of capital cost. Polymeric
F1525–96 (2001)
membranes with very high performance have been designed, cleaning during periodic maintenance or before long shutdown
but their great complexity makes commercialization difficult. periods. It is useful to determine the type of foulants on the
Polymeric membranes currently on the market are available in membrane surface before cleaning. Chemical analysis is the
symmetric and asymmetric configurations. best method; however, in situations in which this may not be
5.1.1.3 Asymmetric membranes are more commonly avail- possible, foulants may be determined by other means such as
able than the symmetric type, especially for UF, NF, and RO. visual inspection. Chemical cleaning clears the membrane
These asymmetric membranes are made of two layers of the surface by dissolving the fouling substances with reagents.
same polymer. They have a thin and dense surface skin and a Table 2 provides a description of common inorganic foulants.
porous substructure that adds strength and support to the thin
5.1.3.2 Each major foulant type will require a specific
skin without reducing the permeate flow. The symmetric
cleaning procedure. If the performance does not improve
configuration has a homogenous structure that provides a very
sufficiently after the first cleaning procedure, the application of
high hydraulic resistance. Another type of membrane, very
another procedure may lead to a better result. Fouling on the
similar to the asymmetric, is the thin film composite. The most
membrane surface is usually complex and often requires
obvious difference is that the two layers are made individually,
several cleaning procedures successively. For example, succes-
from two different kinds of polymers for better performance.
sive cleaning with detergent and citric acid results in generally
The characteristics of several polymeric materials currently
more effective cleaning than either alone. Table 3 lists several
available are listed in Table 1.
of the common cleaning agents used for membranes.
5.1.2 Pretreatment:
5.1.4 Flushing and Cleaning Procedures:
5.1.2.1 Pretreatment of the feed is of primary concern when
5.1.4.1 Flushing—One of the most convenient foulant re-
membranesareused in spill cleanup.Although eachmembrane
moval procedures is flushing. Flushing cleans the membrane
configuration is affected differently by inorganic foulants, most
surface using a large quantity of feedwater at low pressure. It
membranes are affected adversely by oil, grease, and parts per
is effective for cleaning membranes that have been slightly
millionconcentrationsofinorganiccompounds,includingiron,
fouled. The general operating conditions are as follows:
manganese, magnesium, calcium, carbonate ion, and sulphate
(1) Flushing Water—Permeate (treated water),
species. Some organic species, especially at high ppm levels,
(2) Pressure—190 to 590 kPa (28 to 86 psi),
may also have detrimental effects and cause irreversible
(3) Water Flow Rate—High flow rate but pressure drop
damage to the membranes.
limited to less than 10 psi/element,
5.1.2.2 The pH of the feed solution is often adjusted to
(4) Temperature—Ambient but less than 30°C (86°F), and
dissolveorprecipitateinorganics,topreventmembranefouling
(5) Period—0.5 h.
on the membrane surface that leads to a performance decline
5.1.4.2 Cleaning (Polymer Membranes Only)—Chemical
(that is, lower permeate flow rate and increased pressure drop
cleaning is ordinarily used after the flushing procedure.Aflush
between the feed and concentrate sides). The degree of
is also recommended after chemical cleaning to wash off
pretreatment required will depend on the concentration of
dissolved solids and suspended solids in the modules. The
foulants in the feed stream, membranes used, and membrane
general operating conditions for UF membranes are as follows:
cleaning schedule.
It is important to realize that the
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