1、Designation: D 6586 03Standard 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 oforiginal adoption or, in
2、 the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers a test method for the evaluation ofgranular activated carbon
3、(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 targetcompounds on GAC in a
4、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 effluentwaters.1.3 This pra
5、ctice 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 the proceduresecti
6、on, 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 regulatory limitations pr
7、ior touse.2. Referenced Documents2.1 ASTM Standards:2D 1129 Terminology Relating to WaterD 1193 Specifications for Reagent WaterD 2652 Terminology Relating to Activated CarbonD 2854 Test Method Apparent Density of Activated CarbonD 2867 Test Method Moisture Content of Activated CarbonD 2862 Test Met
8、hod Particle Size Distribution of GranularActivated 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 D 1129.4. Summary of
9、 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 flow through a bed of a
10、specially 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 size and operational
11、 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 data for the designof
12、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 column test presented in
13、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 ofGAC caused by inorganic compounds or background organic1This pr
14、actice is under the jurisdiction of ASTM Committee D28 on ActivatedCarbon and is the direct responsibility of Subcommittee D28. 02 on Liquid PHaseEvaluation.Current edition approved Oct. 1, 2003. Published November 2003. Originallyapproved in 2000. Last previous edition approved in 2000 as D 658600.
15、2For referenced ASTM standards, visit 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., an
16、d Solarik, G.,“Determination of Technology and Costs for GAC Treatment Using the ICRMethodology” AWWA GAC 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)
17、uses empty bed contact time (EBCT) and 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
18、removal of contaminantsfrom a common 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. Thefoll
19、owing mechanisms, which cause the breakthrough 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.
20、2 To simulate full-scale performance, 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
21、as the GAC process is scaled. Studies5have 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
22、 carbon particle radius, i.e. the condition 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-scale
23、adsorber), respectively; Rscand Rlcare 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 fo
24、r the RSSCTand the large-column be equal. 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 precise
25、ly simulate the desired (specified) 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
26、 pressure drop across the RSSCT. This 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 equati
27、on7:Ped5 0.334 for 160 # Re Sc # 40,000When 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 im
28、portant as the velocity ofthe RSSCT 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 defi
29、ned as the bed volume(in liters) divided 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 diffusivitye
30、xist within the GAC column does not 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 conducte
31、dto aid in selecting the RSSCT design 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 preparat
32、ion methods are impor-tant design parameters 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 co
33、lumn commonlyused in RSSCT systems, 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 breakpoi
34、nt and the weight ofcarbon used, GAC 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 Predict
35、ions of Atrazine Removal By GAC Adsorbers”,Water Research, Vol 31, No. 11, 1997, pp. 2899-2909.5Crittenden, J. C., Berrigan, J. K., Jr., and Hand, D. W. (1986). 9Design of rapidsmall-scale adsorption tests for a constant surface diffusivity,9 Journal WaterPollution Control Federation, 58(4), 312-319
36、.6Crittenden, J. C., Berrigan, J. K., Jr., Hand, D. W., and Lykins, B. W., Jr. (1987).9Design of rapid fixed-bed adsorption tests for non-constant diffusivities,9 Journal ofEnvironmental Engineering, 113(2), 243-259.7Fried, J. J. (1975). Groundwater pollution. Elsevier Scientific, Amsterdam, TheNeth
37、erlands.D65860327. 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. Th
38、ese 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 in
39、corporated 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, p
40、ressure 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 ca
41、ps with 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 G
42、AC SupportA 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).
43、 The 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
44、-pressurization 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 rateshoul
45、d be 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 sol
46、ids 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 vo
47、latile 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 simil
48、ar material (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
49、prevent 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 ApparatusD6586033placed 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 collected sampl
