1、Designation: D 6586 03 (Reapproved 2008)Standard Practice forthe Prediction of Contaminant Adsorption On GAC InAqueous Systems Using Rapid Small-Scale Column Tests1This standard is issued under the fixed designation D 6586; the number immediately following the designation indicates the year oforigin
2、al adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers a test method for the evaluation ofgranular
3、activated carbon (GAC) for the adsorption of solublepollutants from water. This practice can be used to estimate theoperating capacities of virgin and reactivated granular acti-vated carbons. The results obtained from the small-scalecolumn testing can be used to predict the adsorption of targetcompo
4、unds on GAC in a large column or full scale adsorberapplication.1.2 This practice can be applied to all types of waterincluding synthetically contaminated water (prepared by spik-ing high purity water with selected contaminants), potablewaters, industrial waste waters, sanitary wastes and effluentwa
5、ters.1.3 This practice is useful for the determination of break-through curves for specific contaminants in water, the deter-mination of the lengths of the adsorbates mass transfer zones(MTZ) and the prediction of GAC usage rates for larger scaleadsorbers.1.4 The following safety caveat applies to t
6、he proceduresection, Section 10, of this practice: This standard does notpurport to address all of the safety concerns, if any, associatedwith its use. It is the responsibility of the user of this standardto establish appropriate safety and health practices anddetermine the applicability of regulato
7、ry limitations prior touse.2. Referenced Documents2.1 ASTM Standards:2D 1129 Terminology Relating to WaterD 1193 Specification for Reagent WaterD 2652 Terminology Relating to Activated CarbonD 2854 Test Method for Apparent Density of ActivatedCarbonD 2867 Test Methods for Moisture in Activated Carbo
8、nD 2862 Test Method for Particle Size Distribution ofGranular Activated Carbon3. Terminology3.1 Definitions:3.1.1 For definitions of terms in this practice relating toactivated carbon, refer to Terminology D 2652.3.1.2 For definitions of terms in this practice relating towater, refer to Terminology
9、D 1129.4. Summary of Practice4.1 This practice consists of a method for the rapid deter-mination of breakthrough curves and the prediction of GACusage rates for the removal of soluble contaminants fromwater. This is accomplished by passing the contaminated waterat a constant controlled rate down flo
10、w through a bed of aspecially sized granular activated carbon until predeterminedlevels of breakthrough have occurred.4.2 When the assumption is made that conditions of con-stant diffusivity exist within the GAC column, the break-through data obtained from the column test can be used toestimate the
11、size and operational conditions for a full-scalecarbon adsorber.5. Significance and Use5.1 Granular activated carbon (GAC) is commonly used toremove contaminants from water. However if not used prop-erly, GAC can not only be expensive but can at times beineffective. The development of engineering da
12、ta for the designof full-scale adsorbers often requires time-consuming andexpensive pilot plant studies. This rapid standard practice hasbeen developed to predict adsorption in large-scale adsorbersbased upon results from small column testing. In contrast topilot plant studies, the small-scale colum
13、n test presented in thispractice does not allow for a running evaluation of factors thatmay affect GAC performance over time. Such factors mayinclude, for example, an increased removal of target com-pounds by bacterial colonizing GAC3or long term fouling of1This practice is under the jurisdiction of
14、 ASTM Committee D28 on ActivatedCarbon and is the direct responsibility of Subcommittee D28.02 on Liquid PhaseEvaluation.Current edition approved Aug. 1, 2008. Published September 2008. Originallyapproved in 2000. Last previous edition approved in 2003 as D 658603.2For referenced ASTM standards, vis
15、it the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Owen, D.M., Chowdhury, Z.K., Summers, R.S., Hooper, S.M., and Solarik, G.,“Determination of Tec
16、hnology and Costs for GAC Treatment Using the ICRMethodology,”AWWAGAC andunlike pilot plant studies, small scale studies can be performedin a laboratory using water sampled from a remote location.5.2 This practice known as the rapid small-scale column test(RSSCT) uses empty bed contact time (EBCT) a
17、nd hydraulicloading to describe the adsorption process. Mean carbonparticle diameter is used to scale RSSCT results to predict theperformance of a full-scale adsorber.5.3 This practice can be used to compare the effectivenessof different activated carbons for the removal of contaminantsfrom a common
18、 water stream.6. Summary of Practice6.1 The development of the RSSCT is based on thedispersed-flow pore surface diffusion model (DFPSDM) (Crit-tenden, et al5) which takes into account many of the mecha-nisms that are known to occur in fixed-bed adsorption. Thefollowing mechanisms, which cause the br
19、eakthrough curvesfor an adsorber to spread out and create the mass transfer zoneare included in the DFPSDM: external mass-transfer resistanceor film transfer, axial mixing due to dispersion and the internalmass-transfer resistances of pore and surface diffusion.6.2 To simulate full-scale performance
20、, the amount ofspreading in the breakthrough curve relative to column depthmust be identical for the RSSCT and the full-scale column. Toachieve this, the relative contributions of the mechanisms thatcause most of the spreading are matched by maintainingsimilarity as the GAC process is scaled. Studie
21、s5have shownthat matching of the spreading of the breakthrough curve canbe achieved by equating the dimensionless groups in PFPSDM(Plug Flow Pore Surface Diffusion Model). Under the condi-tions that intraparticle diffusivities are assumed to be indepen-dent of the carbon particle radius, i.e. the co
22、ndition of constantdiffusivity, the following equation describes the relationshipbetween the small and large columns:EBCTscEBCTlc5SRscRlcD25tsctlc(1)where: EBCTscand EBCTlcare the empty-bed contact timesfor the small-column (RSSCT) and the large-column (full-scaleadsorber), respectively; Rscand Rlca
23、re the radii of the carbonparticles used in the small and large columns, respectively; andtscand tlcare the elapsed times required to conduct the small-and large-column tests, respectively. The condition of constantdiffusivity also requires the Reynolds numbers for the RSSCTand the large-column be e
24、qual. This means the followingequation must also be satisfied:VscVlc5RlcRrc(2)where: Vscand Vlcare the hydraulic loadings in the RSSCTand large columns, respectively. Based upon the above equa-tions, the operating conditions for the RSSCT can be selectedto precisely simulate the desired (specified)
25、operating condi-tions for a full-scale adsorber.NOTE 1There is an important issue relating to RSSCT design usingEquation 26. Sometimes using 2 leads to a design with a high head loss,which increases dramatically with operating time, as the GAC is crushedby a large pressure drop across the RSSCT. Thi
26、s may be avoided bylowering the superficial velocity as long as dispersion does not become thedominant transport mechanism and intraparticle mass transfer is limitingthe adsorption rate. The Peclet number based on diameter can be estimatedfrom the following equation7:Ped5 0.334 for 160 # Re Sc # 40,
27、000When the velocity is reduced below what is given in Equation A, axialdispersion, which is caused by molecular diffusion, can be more importantin the RSSCT than in the full scale process. Consequently, Equation A canbe used to check whether dispersion becomes important as the velocity ofthe RSSCT
28、is reduced in an effort to reduce the head loss. Typical Scvalues for SOCs is 2000; consequently, the Re for the RSSCT must bekept greater than 0.1 and the Pe must be kept above 50 for the length ofthe mass transfer zone.NOTE 2Empty-bed contact time (EBCT) is defined as the bed volume(in liters) div
29、ided by the water flow rate in liters/minute. For example if afull scale adsorber holds 20 000 L of activated carbon and the water flowrate is 2500 L/min, the EBCT would be equal to 20 000/2500 or 8.0 min.6.3 The assumption that conditions of constant diffusivityexist within the GAC column does not
30、apply to all waters or alltarget compounds. For example this assumption does not applyfor the decolorization of water and the adsorption of largemolecules, such as humic and fulvic acids. It is recommendedthat at least one RSSCT pilot-column comparison be conductedto aid in selecting the RSSCT desig
31、n variables for a givenwater matrix (Crittenden, et al5). A detailed comparison be-tween the constant diffusivity and proportional diffusivityapproaches and their respective domains of application isbeyond the scope of this practice.6.4 GAC bed volume and preparation methods are impor-tant design pa
32、rameters for the RSSCT. The GAC bed volumeused will determine the required water pumping rate and affectthe amount of water needed to complete the test. The minimumcolumn diameter needed to avoid channeling should be 50particle diameters. For the 10-mm diameter column commonlyused in RSSCT systems,
33、a 60 by 80 mesh carbon should beused. Proper GAC sampling (Practice E 300) and preparation(grinding, classification and washing) are required for repro-ducible results.6.5 Based upon the water feed rate to the column, the timerequired to reach the desired breakpoint and the weight ofcarbon used, GAC
34、 usage rates for treating the water can becalculated. Breakthrough curves for each contaminant beingmonitored during the column test can also be generated.4Knappe, D., Snoeyink, V., Roche, P., Prados, M. and Bourbigot, M., “The Effectof Preloading on RSSCT Predictions of Atrazine Removal By GAC Adso
35、rbers”,Water Research, Vol. 31, No. 11, 1997, pp. 2899-2909.5Crittenden, J. C., Berrigan, J. K., Jr., and Hand, D. W., 9Design of rapidsmall-scale adsorption tests for a constant surface diffusivity,9 Journal WaterPollution Control Federation, Vol. 58, No. 4, pp. 312-319, 1986.6Crittenden, J. C., Be
36、rrigan, J. K., Jr., Hand, D. W., and Lykins, B. W., Jr.9Design of rapid fixed-bed adsorption tests for non-constant diffusivities,9 Journal ofEnvironmental Engineering, Vol. 113, No. 2, pp. 243-259, 1987.7Fried, J. J., Groundwater Pollution. Elsevier Scientific, Amsterdam, TheNetherlands, 1975.D 658
37、6 03 (2008)27. Interferences7.1 Insoluble materials such as oils and greases, suspendedsolids, and emulsions will interfere with the adsorption ofsoluble materials by the GAC. Suspended solids in the columnfeed can lead to increased pressure drop and interfere with theoperation of the column. These
38、materials must be removed bysuitable means before the water being treated is introduced tothe column.7.2 Air bubbles can interfere with water flow through thecolumn and lead to misleading results. A means for removingair bubbles that are introduced into the system with the feedwater should be incorp
39、orated to prevent these problems fromoccurring.8. RSSCT Test Apparatus8.1 The RSSCT test apparatus should be constructed ofglass, PTFE and/or stainless steel, to minimize the adsorptionof organic compounds. The apparatus shown in diagram formin Fig. 1 consists of a metering pump, inlet filter, press
40、ure andflow indicators, up to three columns operating in series andmeans for water sample collection and analysis.8.1.1 Glass columns, vertically supported, 10.5 6 0.5 mminside diameter and approximately 35 cm in length withthreaded joints at both ends are most commonly used.Threaded PTFE end caps w
41、ith seats for neoprene o-ring sealsand tubing connectors should be provided at the top and bottomof the column for the admission and discharge of water. Foroperation at other than room temperature, a means for heatingor cooling the columns and the water being treated should beestablished.8.1.2 GAC S
42、upportA column of fine glass wool installedto give a flat surface across the diameter of the column can beused for support of the GAC column. Alternatively the carbonbed can be supported on a 100-mesh stainless steel screenplaced between two short sleeves made from12 in. PTFEtubing (see Fig. 2). The
43、 sleeves should be sized to fit tightly inthe column to prevent any fluid from flowing between thesleeves and the column wall.8.1.3 Feed PumpsA liquid metering pump capable ofmaintaining a steady flow rate of 6 0.05 mL/min at a columnback pressure of up to 100 psig should be used. To preventover-pre
44、ssurization of the column system in the event ofcolumn plugging during operation, the pump should be set upwith a bypass loop that allows the discharge from the pump tobe vented back to the pump inlet through an adjustable pressurerelief device. The column inlet pressure and water flow rateshould be
45、 monitored and recorded throughout the run.8.1.4 Water FiltrationA filter to remove suspended solidsthat may be present in the water should be installed after themetering pump. A 47-mm inline filter housing with a 1.5 mglass micro-fiber filter has been found to be adequate to removesuspended solids
46、that may prematurely plug the carbon bed.Care must be exercised to ensure organic contaminants in thewater being treated are not removed by the filter paper.8.1.5 Feed Water ContainmentThe feed water should bemaintained at the same temperatures as the carbon columns. Ifthe feed water contains volati
47、le organic compounds (VOCs),special care must be taken to prevent their loss during the test.For short duration column tests where a relatively smallamount of water is to be treated, the feed water can be storedunder zero head space conditions in pillow shaped bagsmanufactured from PTFE or similar m
48、aterial (typically usedfor the collection of gas samples). Gas sampling bags up to 100L in volume can be conveniently used if properly supported. Iflarger volumes of water containing VOCs are to be treated, a55-gal open top drum outfitted with a collapsible PTFE liner orother material that will prev
49、ent VOC loss, can be used. Theliner is attached to the feed pump inlet tube and collapses aswater is removed from the drum, thus always maintaining zeroheadspace conditions. Jacketed columns with temperatureregulated circulation water can be used or the drum can beFIG. 1 Flow Diagram for Three Column RSSCT ApparatusD 6586 03 (2008)3placed in a temperature-controlled cabinet if control of the feedwater temperature is required.8.1.6 Sample Collection SystemWater effluent samples foranalysis should be collected on a regular basis under zeroheadspace conditions. The collect
