ASTM D6586-00
(Practice)Standard Practice for the Prediction of Contaminant Adsorption On GAC In Aqueous Systems Using Rapid Small-Scale Column Tests
Standard Practice for the Prediction of Contaminant Adsorption On GAC In Aqueous Systems Using Rapid Small-Scale Column Tests
SCOPE
1.1 This practice covers a test method for the evaluation of granular activated carbon (GAC) for the adsorption of soluble pollutants from water. This practice can be used to estimate the operating capacities of virgin and reactivated granular activated carbons. The results obtained from the small-scale column testing can be used to predict the adsorption of target compounds on GAC in a large column or full scale adsorber application.
1.2 This practice can be applied to all types of water including synthetically contaminated water (prepared by spiking high purity water with selected contaminants), potable waters, industrial waste waters, sanitary wastes and effluent waters.
1.3 This practice is useful for the determination of breakthrough curves for specific contaminants in water, the determination of the lengths of the adsorbates mass transfer zones (MTZ) and the prediction of GAC usage rates for larger scale adsorbers.
1.4 The following safety caveat applies to the procedure section, Section 10, of this practice: This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D 6586 – 00
Standard Practice for
the Prediction of Contaminant Adsorption On GAC In
Aqueous Systems Using Rapid Small-Scale Column Tests
This standard is issued under the fixed designation D 6586; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 2862 Test Method Particle Size Distribution of Granular
Activated Carbon
1.1 This practice covers a test method for the evaluation of
granular activated carbon (GAC) for the adsorption of soluble
3. Terminology
pollutants from water. This practice can be used to estimate the
3.1 Definitions:
operating capacities of virgin and reactivated granular acti-
3.1.1 For definitions of terms in this practice relating to
vated carbons. The results obtained from the small-scale
activated carbon, refer to Terminology D 2652.
column testing can be used to predict the adsorption of target
3.1.2 For definitions of terms in this practice relating to
compounds on GAC in a large column or full scale adsorber
water, refer to Terminology D 1129.
application.
1.2 This practice can be applied to all types of water
4. Summary of Practice
including synthetically contaminated water (prepared by spik-
4.1 This practice consists of a method for the rapid deter-
ing high purity water with selected contaminants), potable
mination of breakthrough curves and the prediction of GAC
waters, industrial waste waters, sanitary wastes and effluent
usage rates for the removal of soluble contaminants from
waters.
water. This is accomplished by passing the contaminated water
1.3 This practice is useful for the determination of break-
at a constant controlled rate down flow through a bed of a
through curves for specific contaminants in water, the deter-
specially sized granular activated carbon until predetermined
mination of the lengths of the adsorbates mass transfer zones
levels of breakthrough have occurred.
(MTZ) and the prediction of GAC usage rates for larger scale
4.2 When the assumption is made that conditions of con-
adsorbers.
stant diffusivity exist within the GAC column, the break-
1.4 The following safety caveat applies to the procedure
through data obtained from the column test can be used to
section, Section 10, of this practice: This standard does not
estimate the size and operational conditions for a full-scale
purport to address all of the safety concerns, if any, associated
carbon adsorber.
with its use. It is the responsibility of the user of this standard
to establish appropriate safety and health practices and
5. Significance and Use
determine the applicability of regulatory limitations prior to
5.1 Granular activated carbon (GAC) is commonly used to
use.
remove contaminants from water. However if not used prop-
erly, GAC can not only be expensive but can at times be
2. Referenced Documents
ineffective. The development of engineering data for the design
2.1 ASTM Standards:
2 of full-scale adsorbers often requires time-consuming and
D 1129 Terminology Relating to Water
expensive pilot plant studies. This rapid standard practice has
D 1193 Specifications for Reagent Water
3 been developed to predict adsorption in large-scale adsorbers
D 2652 Terminology Relating to Activated Carbon
based upon results from small column testing. In contrast to
D 2854 Test Method Apparent Density of Activated Car-
3 pilot plant studies, the small-scale column test presented in this
bon
practice does not allow for a running evaluation of factors that
D 2867 Test Method Moisture Content of Activated Car-
3 may affect GAC performance over time. Such factors may
bon
include, for example, an increased removal of target com-
pounds by bacterial colonizing GAC or long term fouling of
GAC caused by inorganic compounds or background organic
This practice is under the jurisdiction of ASTM Committee D-28 on Activated
Carbon and is the direct responsibility of Subcommittee D28. 02 on Liquid PHase
Evaluation.
Current edition approved Sept. 10, 2000. Published November 2000. Owen, D.M., Chowdhury, Z.K., Summers, R.S., Hooper, S.M., and Solarik, G.,
Annual Book of ASTM Standards, Vol 11.01. “Determination of Technology and Costs for GAC Treatment Using the ICR
Annual Book of ASTM Standards, Vol 15.01. Methodology” AWWA GAC & Membrane Workshop, March 1996, Cincinnati, OH.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D6586–00
matter . Nevertheless, this practice offers more relevant opera- to precisely simulate the desired (specified) operating condi-
tional data than isotherm testing without the principal draw- tions for a full-scale adsorber.
backs of pilot plant studies, namely time and expense; and
NOTE 1—Empty-bed contact time (EBCT) is defined as the volume (in
unlike pilot plant studies, small scale studies can be performed
liters) of carbon in the adsorber bed divided by the water flow rate in
in a laboratory using water sampled from a remote location.
litres/minute. For example if a full scale adsorber holds 20 000 L of
5.2 This practice known as the rapid small-scale column test
activated carbon and the water flow rate is 2500 L/min, the EBCT would
be equal to 20 000/2500 or 8.0 min.
(RSSCT) uses empty bed contact time (EBCT) and hydraulic
loading to describe the adsorption process. Mean carbon
6.3 The assumption that conditions of constant diffusivity
particle diameter is used to scale RSSCT results to predict the
exist within the GAC column does not apply to all waters or all
performance of a full-scale adsorber.
target compounds. For example this assumption does not apply
5.3 This practice can be used to compare the effectiveness
for the decolorization of water and the adsorption of large
of different activated carbons for the removal of contaminants
molecules, such as humic acids. It is recommended that at least
from a common water stream.
one RSSCT pilot-column comparison be conducted to aid in
selecting the RSSCT design variables for a given water matrix
6. Summary of Practice
(Crittenden, et al ). A detailed comparison between the con-
6.1 The development of the RSSCT is based on the
stant diffusivity and proportional diffusivity approaches and
dispersed-flow pore surface diffusion model (DFPSDM) (Crit-
their respective domains of application is beyond the scope of
tenden, et al ) which takes into account many of the mecha-
this practice.
nisms that are known to occur in fixed-bed adsorption. The
6.4 GAC bed volume and preparation methods are impor-
following mechanisms, which cause the breakthrough curves tant design parameters for the RSSCT. The GAC bed volume
for an adsorber to spread out and create the mass transfer zone
used will determine the required water pumping rate and affect
are included in the DFPSDM: external mass-transfer resistance the amount of water needed to complete the test. The minimum
or film transfer, axial mixing due to dispersion and the internal
column diameter needed to avoid channeling and to minimize
mass-transfer resistances of pore and surface diffusion. column head loss should be 50 particle diameters. For the
6.2 To simulate full-scale performance, the amount of
10-mm diameter column commonly used in RSSCT systems, a
spreading in the breakthrough curve relative to column depth 60 by 80 mesh carbon should be used. Proper GAC sampling
must be identical for the RSSCT and the full-scale column. To
(Practice E 300) and preparation (grinding, classification and
achieve this, the relative contributions of the mechanisms that washing) are required for reproducible results.
cause most of the spreading are matched by maintaining
6.5 Based upon the water feed rate to the column, the time
similarity as the GAC process is scaled. Crittenden et. al. have required to reach the desired breakpoint and the weight of
shown that matching of the spreading of the breakthrough
carbon used, GAC usage rates for treating the water can be
curve can be achieved by assuming intraparticle diffusivities calculated. Breakthrough curves for each contaminant being
are independent of the carbon particle radius, i.e. the condition
monitored during the column test can also be generated.
of constant diffusivity. Under these conditions of constant
7. Interferences
diffusivity, the following equation describes the relationship
7.1 Insoluble materials such as oils and greases, suspended
between the small and large columns:
solids, and emulsions will interfere with the adsorption of
EBCT | R | t
sc sc sc
5 5 (1)
soluble materials by the GAC. Suspended solids in the column
EBCT | R | t
lc lc lc
feed can lead to increased pressure drop and interfere with the
where: EBCT and EBCT are the empty-bed contact times
sc lc
operation of the column. These materials must be removed by
for the small-column (RSSCT) and the large-column (full-scale
suitable means before the water being treated is introduced to
adsorber), respectively; R and R are the radii of the carbon
sc lc
the column.
particles used in the small and large columns, respectively; and
7.2 Air bubbles can interfere with water flow through the
t and t are the elapsed times required to conduct the small-
sc lc
column and lead to misleading results. A means for removing
and large-column tests, respectively. The condition of constant
air bubbles that are introduced into the system with the feed
diffusivity also requires the Reynolds numbers for the RSSCT
water should be incorporated to prevent these problems from
and the large-column be equal. This means the following
occurring.
equation must also be satisfied:
8. RSSCT Test Apparatus
V R
sc lc
5 (2)
V R 8.1 The RSSCT test apparatus should be constructed of
lc rc
glass, PTFE and/or stainless steel, to minimize the adsorption
where: V and V are the hydraulic loadings in the RSSCT
sc lc
of organic compounds. The apparatus shown in diagram form
and large columns, respectively. Based upon the above equa-
in Fig. 1 consists of a metering pump, inlet filter, pressure and
tions, the operating conditions for the RSSCT can be selected
flow indicators, up to three columns operating in series and
means for water sample collection and analysis.
8.1.1 Glass columns, vertically supported, 10.5 6 0.5 mm
Knappe, D., Snoeyink, V., Roche, P., Prados, M. and Bourbigot, M., “The Effect
inside diameter and approximately 35 cm in length with
of Preloading on RSSCT Predictions of Atrazine Removal By GAC Adsorbers”,
threaded joints at both ends are most commonly used.
Water Research, Vol 31, No. 11, 1997, pp. 2899-2909.
Crittenden, et al, Threaded PTFE end caps with seats for neoprene o-ring seals
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D6586–00
FIG. 1 Flow Diagram for Three Column RSSCT Apparatus
and tubing connectors should be provided at the top and bottom 8.1.3 Feed Pumps—A liquid metering pump capable of
of the column for the admission and discharge of water. For maintaining a steady flow rate of 6 0.05 mL/min at a column
operation at other than room temperature, a means for heating back pressure of up to 100 psig should be used. To prevent
or cooling the columns and the water being treated should be over-pressurization of the column system in the event of
established. column plugging during operation, the pump should be set up
8.1.2 GAC Support—A column of fine glass wool installed with a bypass loop that allows the discharge from the pump to
to give a flat surface across the diameter of the column can be be vented back to the pump inlet through an adjustable pressure
used for support of the GAC column. Alternatively the carbon relief device. The column inlet pressure and water flow rate
bed can be supported on a 100-mesh stainless steel screen should be monitored and recorded throughout the run.
placed between two short sleeves made from ⁄2in. PTFE tubing 8.1.4 Water Filtration—A filter to remove suspended solids
(see Fig. 2). The sleeves should be sized to fit tightly in the that may be present in the water should be installed after the
column to prevent any fluid from flowing between the sleeves metering pump. A 47-mm inline filter housing with a 1.5 μm
and the column wall. glass micro-fiber filter has been found to be adequate to remove
FIG. 2 Alternate Flow Diagram for Three Column RSSCT
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D6586–00
suspended solids that may prematurely plug the carbon bed.
Care must be exercised to ensure organic contaminants in the
water being treated are not removed by the filter paper.
8.1.5 Feed Water Containment—The feed water should be
maintained at the same temperatures as the carbon columns. If
the feed water contains volatile organic compounds (VOCs),
special care must be taken to prevent their loss during the test.
For short duration column tests where a relatively small
amount of water is to be treated, the feed water can be stored
under zero head space conditions in pillow shaped bags
manufactured from PTFE or similar material (typically used
for the collection of gas samples). Gas sampling bags up to 100
L in volume can be conveniently used if properly supported. If
larger volumes of water containing VOCs are to be treated, a
55-gal open top drum outfitted with a collapsible PTFE liner or
other material that will prevent VOC loss, can be used. The
liner is attached to the feed pump inlet tube and collapses as
water is removed from the drum, thus always maintaining zero
headspace conditions. Jacketed columns with temperature
regulated circulation water can be used or the drum can be
placed in a temperature-controlled cabinet if control of the feed
water temperature is required.
8.1.6 Sample Collection System—Water effluent samples for
analysis should be collected on a regular basis under zero
headspace conditions. The collected samples should be refrig-
erated during collection or as soon as possible after collection
FIG. 3 Diagram of RSSCT Carbon Column
to prevent degradation prior to analysis. The use of an
automated sampler that is capable of collecting zero head space
discarded. If breakthrough has
...
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