Treatment of Water by Granular Activated Carbon - ACS Publications

22 Dynamic Behavior of Organics in Full-Scale Granular Activated-Carbon Columns Downloaded by NORTH CAROLINA STATE UNIV on May 3, 2015 | http://pubs.acs.org Publication Date: March 15, 1983 | doi: 10.1021/ba-1983-0202.ch022

R. SCOTT SUMMERS and PAUL V. ROBERTS Stanford University, Department of Civil Engineering, Stanford, CA 94305

Three full-scale granular activated-carbon columns were used to characterize the removal of organic substances for 1 year. Long-term partial removal of aromatic organic com pounds and organic compounds measured by total organic carbon and total organic halogen occurred. Biological de gradation was thought to be a major contributing mechanism. Elution of halogenated one- and two-carbon compounds was observed. There were only minor differences between fresh and regenerated adsorbent with regard to removal of total organic carbon, total organic halogen, and 20 specific organic compounds.

T

of three full-scale granular activated-carbon (GAC) columns was characterized with regard to the removal of organic substances qver a 1-year period. The parallel arrangement of the GAC system allowed for a direct comparison of fresh, once-regenerated, and exhausted Filtrasorb-300 GAC. Carbon was considered exhausted if it had been in service sufficiently long (1 year, equivalent to 13,000 bed volumes treated) to saturate its adsorption capacity for total organic carbon (TOC). By using a composite sampling system, a more representative characterization of the removal of organic compounds was achieved than was possible with grab samples. The organic compounds were characterized by two collective parameters—TOC and total organic halogen (TOX)—as well as by analysis for 20 specific organic compounds, including 16 on the U.S. EPA's priority pollutant list. H E P A R A L L E L PERFORMANCE

Facilities Reclamation Facility. The GAC system is part of the Santa Clara Valley Water District's Palo Alto Reclamation Facility. Figure 1 shows a 0065-2393/83/0202-0503$6.25/0 © 1983 American Chemical Society

In Treatment of Water by Granular Activated Carbon; McGuire, M., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1983.


CHLORINE CONTACT TANK

CARBON REGENERATION SYSTEM

SPENT I \ REGENERATED CARBON REGENERATION CARBON STORAGE FURNACE

FILTERS

Figure 1. Schematicflewdiagram of the Palo Alto Reclamation Facility.

LIME

Downloaded by NORTH CAROLINA STATE UNIV on May 3, 2015 | http://pubs.acs.org Publication Date: March 15, 1983 | doi: 10.1021/ba-1983-0202.ch022

22.

SUMMERS A N D ROBERTS

Behavior of Organics in GAC Columns

schematic of the basic unit processes in operation during the study. The Palo Alto Reclamation Facility receives 0.067 m /s (1.5 million gallons/ day) of chlorinated activated-sludge effluent from Palo Alto's wastewater treatment plant. The reclamation facility provided treatment before granular activated carbon in the following sequence during the present study: lime clarification at pH 11; recarbonation with C 0 ; mixed-media filtration; and ozonation at a rate of 0.5 mg 0 /mg TOC. This sequence resulted in a contact time of 2 h for chlorine with the waste stream before the G A C columns. The effluent from the upflow G A C columns was filtered and chlorinated before injection into an aquifer as part of a groundwater recharge system. The upflow G A C columns are operated at a superficial linear velocity of 10.8 m/h (4.4 gpm/ft ) providing an empty-bed contact time of 34 min. The flow through each of the three columns is 0.022 m /s (0.5 million gallons/day). On-site thermal regeneration of the adsorbent is accomplished with a multiple-hearth furnace. During the study period, constant conditions were maintained in the treatment steps prior to activated carbon. No attempt was made to investigate the effects of changes in pretreatment, e.g., benefits or disadvantages of preozonation. Composite Sampler. In an earlier study, grab sampling of the G A C influent and effluent resulted in unacceptably high variations in the measured concentration of specific organic compounds. Such variation complicates the evaluation of GAC performance. Composite samplers with floating Teflon covers were fabricated and installed on a common influent and the three effluent lines of the G A C columns (Figure 2). The float sample system was based on the design of Westrick and Cummins (I). The float samplers were designed to minimize the liquid sampleatmospheric interfacial area, thus reducing the loss of volatile compounds during the composite period. A line providing continuous flow from the system sampling point was connected to the refrigerated sampling system. A sample timer activated the two sample valves, A and B, at a frequency of 30 min over a composite period of 7 days, resulting in a composite of 350 grab samples. A 200-mL aliquot of a saturated solution of sodium thiosulfate was initially added to the sample chamber to minimize the formation of chlorinated organics in the sample chamber over the compositing period. At the end of the sample period, the float sampler was thoroughly mixed, and samples for T O X and specific organic compound analysis were taken through valve C. A separate composite sample preserved with hydrochloric acid was taken for T O C analysis. A preliminary study of the stability of samples stored as described above found that storage at 4°C for 1 week did not appreciably affect the concentrations of the volatile compounds reported here. The variations in 3

2

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506

T R E A T M E N T O F W A T E R BY G R A N U L A R A C T I V A T E D C A R B O N

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Figure 2. Schematic diagram of the composite sampling system where T = 4°C concentration during that period did not exceed the standard deviation of the gas chromatographic analysis, approximately ± 15%. The composite samplers were operated continuously with a 7-day composite period for the first 6 months (7100 bed volumes). Thereafter, 10-day composite samples were taken at 6-week intervals except during episodes of plant operational problems. Sampling of the exhausted column for organics other than T O C was discontinued after 4500 bed volumes. Analysis for T O X in all columns was discontinued after 7100 bed volumes. Some G A C fines were found in the regenerated column composite sample during the first month of operation.

Analytical Procedures The organic constituents were characterized by analysis for 20 specific organic compounds and two collective parameters. Table I lists the compounds, detection limits, and analytical precisions. The eight halogenated one- and two-carbon compounds were characterized using gas chromatography of concentrates prepared by the pentane extraction procedure described by Henderson et al. (2). The closed-loop stripping analysis for 11 aromatic compounds as well as for heptaldehyde utilized the Grob procedure for concentrating trace organics (3). The T O X analysis measures the purgeable and nonpurgeable fractions separately as described by Jekel and Roberts (4). Organic carbon was measured using


22.

SUMMERS AND ROBERTS


507

Table I. Detection Limits and Precision of Analysis

(Hg/L)

Standard Deviation, % of Mean

0.05

10-20

0.02

10

0.01

5

Detection Limit Compounds or Collective Parameters Halogenated 1- and 2-carbon compounds: chloroform, bromoform


1,1,1- trichloroethane, dibromochloromethane, bromodichloromethane, trichloroethylene, and tetrachloroethylene carbon tetrachloride Aromatic compounds: aromatic hydrocarbons^ chlorinated benzenes Heptaldehyde Total organic carbon (TOC) Total organic halogen (TOX) (measured as CI) c

)

>

0.015 0.02 0.015 200 35

1

90 30 90 5 5

Valid for concentrations greater than five times the detection limit. Ethylb enzene; naphthalene, m- and p-xylene; and 1- and 2-methylnaphthalene. Chlorobenzene; 1,2-, 1,3-, and 1,4-dichlorobenzene; and 1,2,3- and 1,2,4trichlorobenzene. fl

fo c

an Oceanography International ampule system adapted to a Dohrmann DC-52 organic carbon analyzer. Results and Discussion General Features of Breakthrough Responses. The results of the removal of organics by GAC columns are illustrated by several types of breakthrough curves shown in Figure 3. Evidence of the four phenomena—immediate partial breakthrough, initial breakthrough, steady-state removal, and elution—can be inferred. Immediate breakthrough refers to a condition where the first sample taken shows the presence of the constituent in the effluent at a concentration substantially above the detection limit. This phenomenon occurred with T O C and TOX, indicating that a portion of the influent T O C and T O X is not amenable to removal by GAC treatment. Cannon and Roberts (5) previously reported that approximately 10% of the T O C in the same wastewater was nonadsorbable, even at high activated-carbon dosages, in equilibrium-isotherm studies. Initial breakthrough occurs when measurable amounts of the constituent first appear in the effluent; thus, complete removal of the compound occurs prior to this point. In this study, initial breakthrough of organics occurs over a wide range of time, from the first sample taken (immediate breakthrough) to 4 months (4000 bed volumes) into the study.


508


Ο


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T H R O U G H P U T (θ)-BED

VOLUMES

Figure 3. Generalized concept of tupes of breakthrough responses, illustrating the phenomena of immediate breakthrough, initial breakthrough, steady-state removal, and elution. Steady-state removal is a condition in which the effluent concen tration rises with time and eventually assumes a steady-state value which is less than that of the influent. Evidence of steady-state removal was found for T O C , TOX, and the aromatic compounds. Possible mechanisms for these long-term partial removals are slow adsorption phenomena (6) and biological degradation of organic material by bacteria attached to the G A C in the columns (7). Roberts and Summers (8) in a review of G A C performance found evidence of both immediate breakthrough and steadystate removal of T O C in nearly all cases reviewed. Elution refers to the situation in which the effluent concentration rises to values greater than that of the influent concentration. Evidence of this phenomenon was found for six halogenated one- and two-carbon compounds. Of the proposed mechanisms for elution, competitive adsorp tion and re-equilibration to a change in influent concentration are thought to be responsible. Collective Parameters. The performance of the three G A C columns for the removal of organic compounds measured by T O C and TOX is summarized in Table II. An immediate breakthrough of 1.0-1.5 mg/L T O C upon startup of both the fresh and regenerated columns,



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THROUGHPUT ( θ ) - BED VOLUMES Figure 4. TOC breakthrough response for fresh GAC The shaded bands represent perturbations of pH and dissolved oxygen consumption. Key: •, influent; •, effluent; M, high pH and low ADO; and —, Q/Co. indicates that 15-20% of the influent T O C is not amenable to adsorption by G A C . This immediate breakthrough is illustrated in the T O C break through response for fresh GAC (Figure 4). With increasing service time, the column became saturated with organics and the effluent concen tration rose steadily as the volume treated increased to an amount equivalent to 4500 bed volumes (4 months), where, with the exceptions of peaks at 5200 and 6900 bed volumes, it assumed a steady-state value of 6570% of the influent. This steady-state partial removal of approximately one-third of the influent was maintained for the remaining 9000 bed volumes (8 months) of the study. Figure 5 shows the relationship between the influent p H and the dissolved oxygen consumption (ADO) through the G A C columns. Initially only 1 mg/L of D O was consumed. After 2 weeks of acclimation and growth, the bacteria attached to the G A C began to utilize more oxygen and after 3 weeks, 5 mg/L D O was consumed. The influent pH remained relatively stable during the initial stages, fluctuating between 8 and 6.5 with two exceptions: problems with the C 0 compressor used in the recarbonation process occurred at 4800 and 6600 bed volumes, resulting in each instance in short-term rises to pH 11. Coincidental with therisein pH, decreases in the D O consumption and T O C removal in the G A C columns were observed for the duration of the p H perturbation and for the succeeding several hundred bed volumes. This extended reaction to the high influent pH is an indication that biological degradation of organic 2


22.

SUMMERS AND ROBERTS


-


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THROUGHPUT (Θ) — BED VOLUMES Figure 5. Rehtion between dissolved oxygen consumption and pH upsets; data from NASA Water Monitonng System. material occurred in the GAC columns under normal pH conditions. After a period of acclimation and regrowth, the bacteria again consumed D O and T O C . Under normal pH conditions, the measured effluent D O concentration range was 0.5-3 mg/L; however, it is possible that some oxygen may have been introduced into the sample stream during flow through the NASA sampling system (9). Thus, it is possible that the D O concentration may have been overestimated, and the availability of D O may have been a limiting factor in the biological utilization of organic material. The response of all three G A C columns to the p H / A D O upsets can be seen in the fractional concentration breakthrough curves for T O C (Figure 6). The periods of lowest T O C removal for all columns coincided with the p H / A D O upset periods, with one exception at 2100 bed volumes for the exhausted column. Figure 6 also shows the similarity of the fresh and regenerated carbon with respect to immediate breakthrough of T O C and the general features of the rate of approach to steady state. A statistically similar steady-state condition existed in all three columns after 7100 bed volumes. The cumulative removal of T O C by adsorption was 34 mg TOC/g GAC and 37 mg TOC/g G A C for the fresh and regenerated adsorbents, respectively. The amount of T O C removed by adsorption is calculated as the difference in the total amount removed in a column and that removed


512


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2500

5000

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THROUGHPUT (fi)-BED VOLUMES (

Figure 6. TOC fractional breakthrough curves for fresh (—), regenerated λ and exhausted GAC (—·—). Conditions: 03, high pH and low ADO.

400

Figure 7. TOX breakthrough re sponsefor fresh GAC. Key: •, in fluent; 0, effluent, —, Q / C Q , - and ESI, higjn pH and low ADO.

2000

4000

6000

THROUGHPUT(0 ) - BED VOLUMES



22.

SUMMERS AND ROBERTS


513

by the exhausted column, presumably by biodégradation. In view of experimental error, the difference between the adsorption capacities of the fresh and regenerated GAC is not significant. As with T O C , little difference can be seen between the fresh and regenerated G A C columns for the removal of TOX. The breakthrough response for T O X removal in the fresh GAC is shown in Figure 7. Steadystate removals of T O X amounting to 24% and 18% for fresh and regenerated GAC, respectively, were achieved after 4000 bed volumes, while the exhausted column maintained a removal of 21%. The breakthrough curves for T O X also exhibited a response to the p H / A D O upsets. The immediate breakthrough of 35-60 μg/L· T O X (15%-30% of the influent concentration) in both fresh and regenerated G A C columns indicates that a portion of TOX, similar to that of TOC, is not amenable to GAC treatment The cumulative removals of TOX by adsorption were 1.1 mg TOX/g GAC and 1.8 mg TOX/g G A C for fresh and regenerated adsorbent, respectively; the difference is not significant. This rate corresponds to a mass ratio of0.030 g TOX (as chlorine) adsorbed per g T O C adsorbed, or a mole ratio of approximately 0.010 mole organic halogen adsorbed per mole organic carbon adsorbed. Halogenated One- and Two-Carbon Compounds. The perforance of the G A C columns for the removal of the halogenated one- and two-carbon compounds is summarized in Table II. The three brominated compounds and trichloroethylene were removed completely (detection limit of 0.02 /xg/L) by both fresh and regnerated G A C for a substantial period, i.e., 1600-4000 bed volumes. Trichloroethane and tetrachloro ethylene exhibited an immediate breakthrough of less than 1% for 2000 and 4000 bed volumes, respectively. Chloroform displayed a slight im mediate breakthrough of 2-3%. Carbon tetrachloride exhibited erratic initial breakthrough: 30% after the first 600 bed volumes, then dropping to 10% in both columns. The behavior of carbon tetrachloride was obscured by the low influent concentration of 0.1 μg/L. Trichloroethylene and tetrachloroethylene were both substantially removed by the exhausted GAC column during this study: 13,000-17,500 bed volumes. Six of the eight halogenated one- and two-carbon compounds in both fresh and regenerated G A C exhibited behavior suggesting elution. Al though it is difficult to distinguish competitive adsorption from reequilibration in a full-scale study where there is uncontrolled variation in the influent concentrations, some tendencies can be discerned. The breakthrough pattern for chloroform (Figure 8) is an example of elution during the period of relatively steady influent concentration, indicating that competitive adsorption may be the underlying cause. Exhibiting immediate breakthrough to only a slight extent, 2%, the



514


chloroform breakthrough curve rose rapidly after 1600 bed volumes to fractional concentration peaks of 3-4. While the initial rapid rise may have been exaggerated by the 30% decrease in the influent concentration, elution continued over a 4000-bed-volume period during which the influent concentration remained stable. Three halogenated one- and two-carbon compounds ( 1,1,1-trichloroethane, trichloroethylene, and tetrachloroethylene) eluted at times corresponding to a decrease of 1-2 orders of magnitude in the influent concentration, indicating that re-equilibration of the system to the lower influent concentration may have been responsible. Figure 9 shows the breakthrough pattern for 1,1,1-trichloroethane on regenerated G A C . After showing no immediate breakthrough, the fractional concentration rose rapidly after 2500 bed volumes. Shortly after complete breakthrough, the compound eluted in response to an order-of-magnitude decrease in the influent concentration beginning at approximately 4000 bed volumes. Any reaction to the p H / A D O upsets at 4800 and 6600 bed volumes would be masked by the elution phenomenon. Figure 10 depicts the chloroform mass removal for the fresh and regenerated GAC for the first 7100 bed volumes and for the exhausted GAC for the first 4500 bed volumes of the study. Cumulative mass removed is plotted versus cumulative mass applied, both expressed in units of micrograms of chloroform per gram of GAC. The dashed line represents 100% removal. Two important observations can be made: first, the difference between fresh and regenerated GAC for the removal of chloroform; and second, the apparent net production of chloroform in the exhausted and regenerated GAC.



22.

SUMMERS A N D ROBERTS


THROUGHPUT ( θ )-BED

515

VOLUMES

Figure 9. Breakthrough response of 1,1,1-trichlorethane with regenerated GAC, illustrating re-equilibration following decrease in influent concentra tion Key: M, influent; •, effluent; and —, C / C Q .

200

CUMULATIVE APPLIED(/*g/g) Figure 10. Cumulative mass removal of chloroform, demonstrating elution ana net production. Key: •, fresh; O, regenerated; A, exhausted; ana , 100% removal.



516


The fresh carbon exhibited a maximum cumulative removal of chloro form at 106 tig/g applied, while the regenerated G A C showed less removal efficiency after 60 μ-g/g had been applied and had a maximum removal after 83 /Ag/g had been applied. The adsorptive capacity for chloroform at the maximum cumulative mass removed was 72 μg/g and 58 /xg/g for the fresh and regenerated GAC, respectively. These values agree approximately with those reported for drinking water and with singlesolute isotherm data at a similar concentration (10 itg/L) of chloroform (10). Both GAC columns exhibited elution of the adsorbed chloroform. In the period between 2500 and 5000 bed volumes, the regenerated G A C eluted the total amount removed (58 ttg/g) during the first 2500 bed volumes. After 5000 bed volumes, there was an apparent net production of chloroform in the regenerated GAC. The exhausted column showed some net production of chloroform during the period between 13,000 and 17,500 bed volumes. The apparent net production of chloroform may be accounted for by reaction between organic precursor material and the residual chlorine in the G A C influent; the chlorine residual in the influent ranged from 2 to 5 mg/L, as combined chlorine. The phenomenon of net production of chloroform needs to be studied more systematically. One method of comparison of the fresh, regenerated, and exhausted GAC is based on the cumulative mass removed. Figure 11 is a comparison of the mass removed by activated carbon in several different states (fresh, regenerated, and exhausted), expressed relative to the mass removed by the fresh carbon. The period of comparison is the first 4500 bed volumes for the fresh and regenerated GAC and 13,000-17,500 bed volumes for the exhausted GAC. During this period, the exhausted column continued to remove a significant portion of trichloroethylene and tetrachloro ethylene relative to the fresh GAC. Similar results for these two com pounds are reported in Table II on a percent removal basis. There were some differences between fresh and regenerated G A C after 4500 bed volumes in the removal of chloroform, 1,1,1-trichloroethane, and carbon tetrachloride but not for the other compounds. In all cases, the fresh GAC removed an equal or greater amount of organics compared to the regenerated GAC. The relationship between fresh and regenerated G A C on the same mass removal basis after 7100 bed volumes (data not shown) led to conclusions similar to those at 4500 bed volumes for all halogenated one- and two-carbon compounds. Two other criteria for comparison of fresh and regenerated G A C are the time to initial breakthrough and the time to adsorption exhaustion (Table II). Only two significant differences between the fresh and regenerated adsorbent can be found using these criteria. The extents of initial breakthrough of dibromochloromethane and bromoform both occur much earlier for the regenerated GAC. Smaller


22.

SUMMERS AND ROBERTS

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insignificant differences can be found for other compounds using both criteria As with the mass removal comparison, the fresh G A C exhibits an equal or superior performance for organic removal in all cases. Aromatic Compounds. The 11 aromatic compounds exhibited a more erratic breakthrough behavior than did the halogenated one- and two-carbon compounds, which hinders a systematic analysis of their break through responses. An example of an aromatic compound breakthrough response is 1,4-dichlorobenzene (1,4-DCB) shown in Figure 12 for the fresh G A C column. As with eight of the 11 aromatic compounds, 1,4-DCB displayed a response to the p H / A D O upset. Excluding the periods of p H / A D O upsets, over 96% of 1,4-DCB is removed on a long-term average. Table III lists the mean influent concentration, the average per-



518


THROUGHPUT ( θ ) - BED VOLUMES Figure 12. Breakthrough response for 1.4-dichlorobenzene on fresh GAC Key: •, influent; •, effluent; —; Q/Co; and M, high pH and low ADO. cent removal including p H / A D O upset periods for all three columns, and an indicator of the compounds' response to the p H / A D O upset. The chlorinated benzenes and the naphthalene compounds were significantly removed on a long-term basis, whereas ethylbenzene, the xylenes, and heptaldehyde were removed to a lesser extent Little difference is seen between the removal capacities of fresh and regenerated GAC. In some cases, the exhausted G A C removal capacity showed a significant differ ence compared to the fresh and regenerated adsorbents, but the ex hausted G A C removal capacity is based on a different time period (the first 4 months of the study) than the others, so a direct comparison cannot be made. Figure 13 shows the comparison of G A C condition on a mass removal basis relative to fresh G A C after the first 4500 bed volumes for eight of the compounds listed in Table III. For the chlorinated benzenes, little difference is seen between any of the three G A C conditions even though the exhausted column had a previous service of 13,000 bed volumes (1 year). Ethylbenzene and heptaldehyde both exhibited different removals for each G A C . A similar comparison after 7100 bed volumes (data not shown) revealed little difference between fresh and regenerated G A C for the removal of any of the compounds including ethylbenzene and heptaldehyde. The long-term removal trends and the response to the p H / A D O upsets indicate that biological degradation may be an underlying removal


22.

SUMMERS AND ROBERTS


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mechanism. Studies conducted by Bouwer and McCarty (11) support this tentative conclusion. A biological degradation study of five of the six chlorinated benzenes reported here (excluding 1,2,3-trichlorobenzene) was conducted in continuous-flow inert-media columns with fixed-film bacteria. At influent concentrations of 10 Mg/L, long-term (1 year, or 26,000 bed volumes) removals of 90% or better were achieved with the exception of 1,3-dichlorobenzene. They also report acclimation periods of 10-40 days, which, if applied to the Palo Alto Reclamation Facility GAC system, would imply that adsorption was the controlling chlorinated benzene removal mechanism during the first 300-1200 bed volumes after which biodégradation and adsorption are both important.


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SUMMERS AND ROBERTS


521

Collective and Specific Indicators. Figure 14 shows a comparison of the breakthrough patterns for TOC, TOX, and chloroform for the fresh GAC column. Similar characteristics are observed for T O C and TOX removal. Both exhibited 15-20% immediate breakthrough, adsorption saturation at 4500-5000 bed volumes, steady-state partial removal of 2035%, and decreased removal in response to the p H / A D O upsets. In contrast, chloroform exhibited insignificant immediate breakthrough, a more rapid rise to adsorption saturation followed by substantial elution, and no detectable reaction to p H / A D O upsets. Chloroform is used here as a conservative indicator of the behavior of organic contaminants. The initial breakthrough and adsorption saturation of chloroform occur earlier than the other specific organic compounds and collective parameters. If G A C treatment installations are designed and operated in such a way as to remove chloroform effectively, there is reasonable assurance that most other hazardous specific organic com pounds will be removed as well. In other words, chloroform may serve as a conservative indicator in the sense of providing an early warning of impending breakthrough of other specific organics of concern, even though its behavior is by no means representative of organic pollutants in general.

15000

THROUGHPUT ( θ ) - BED VOLUMES Figure 14. Breakthrough behavior of chloroform ( ), TOX ( TOC (—) onfreshGAC. Key: S, high pH and low ADO.


), and

522



Conclusions Several phenomena were significant in the removal of organic compounds by granular activated-carbon columns, overlaying the dominant breakthrough pattern of adsorption and saturation. Long-term partial removal of aromatic organic compounds and organic compounds as measured by the collective parameters T O C and T O X occurred. Biological degradation is thought to be a major contributing mechanism in this long-term removal. Elution of halogenated one- and two-carbon compounds was observed. Competitive adsorption and re-equilibration due to a decrease in the influent concentration are thought to be responsible for the elution phenomenon. In some cases, fresh G A C outperformed regenerated GAC, but the differences are small. Acknowledgments The authors thank Gary Hopkins for the T O C and TOX analyses and fabrication of sampling system, Martin Reinhard for guidance on organic analytical procedures ,and Richard Harnish for the analysis of the specific organic compounds. The cooperation of the Santa Clara Valley Water District particularly James Sanchez, and the staff of the National Aeronautics and Space Administration Water Monitoring Station, especially Rick Brooks, is appreciated. This work was carried out as part of a research program on groundwater recharge with reclaimed water, and was supported by the Robert S. Kerr Environmental Research Laboratory of the U.S. Environmental Protection Agency, Grant R-804431, and the State Water Resources Control Board, Agreement No. 8-178-400-0. Literature Cited 1. Westrick, J. J.; Cummins, M. D. J. Water Pollution Control Fed. 1979, 51, 12. 2. Henderson, J. E.; Peyton, G. R.; Glaze, W. H. In "Indentification and Analysis of Organic Pollutants in Water"; Keith, L. H., Ed.; Ann Arbor Science: Ann Arbor, Mich. 1976. 3. Grob, K.; Zurcher, F. J. Chromatog. 1976, 117, 285. 4. Jekel, M. R.; Roberts, P. V. Environ. Sci. Technol. 1980, 14, 970. 5. Cannon, F. S.; Roberts, P. V.J.Environ.Eng.Dir., ASCE 1982, 108(EE4), 766. 6. Peel, R.; Benedek, A. J. Environ.Eng.Div., ASCE, 1980, 106 (EE4) 797. 7. "Activated Carbon Adsorption of Organics from the Aqueous Phase"; McGuire, M. J.; Suffet, I. H., Eds.; Ann Arbor, Science: Ann Arbor, Mich. 1980; Vol. 2 pp 273-416. 8. Roberts, P. V.; Summers, R. S. J. Am. Water Works Assoc. 1982, 74, 113. 9. Brooks, R.; Jeffors, E.; Nishioka, K.; Kriege, D. F.; Sanchez, W. I. Proc. Water Reuse Symposium II, Washington, D.C., AWWA Research Foundation, August 1981. 10. Symons, J. M. et al., Treatment Techniques for Controlling Trihalomethanes in Drinking Water, EPA-600/2-81-156, USEPA, Cincinnati, Oh. 1981.


22.

SUMMERS AND ROBERTS


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11. Bouwer, E. J.; McCarty, P. L. Proc. Environ. Eng. Nat. Conf., Amer. Soc. of Civil Engr., Atlanta, Ga, July 1981.


RECEIVED for review August 3, 1981. ACCEPTED for publication April 9,


1982.

Treatment of Water by Granular Activated Carbon - ACS Publications

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