Drinking Water and Health, Volume 2 (1980) / Chapter Skim
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IV. An Evaluation of Activated Carbon for Drinking Water Treatment
IV. An Evaluation of Activated Carbon for Drinking Water Treatment
Pages 251-380
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From page 251... ...
as the option of choice for the control of "synthetic organic chemicals" in drinking water. During the subcommittee's study, the EPA held hearings and received written comments regarding this treatment.
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From page 252... ...
The removal of organic compounds from drinking water has been based primarily on the measurement of organic matter as measured by carbon chloroform extract (CCE) , total organic carbon (TOC)
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From page 253... ...
This report identifies the compounds that may be removed and/or added to drinking water by the adsorption process with its attendant chemical and microbial processes. It focuses on recently published lists of organic chemicals of concern to health (Interagency Regulatory Liaison Group, 1978; National Academy of Sciences, 1977, 1979; National Cancer Institute, 1978~.
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From page 254... ...
As is true with any production process, the quality of the final product is influenced by the starting material. In the past, activated carbons that were used for industrial applications were commonly produced from wood, peat, and other vegetable derivatives.
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From page 255... ...
After treatment of a water supply with GAC, postdisinfection is generally used to reduce the total number of bacteria, some of which may be present because of the microbial growths in absorbers. Sufficient disinfectant is usually applied to ensure a residual in the distribution system to prevent contamination of the water.-Postdisinfection is used in addition to predisinfection because aqueous oxidants that are used in preliminary disinfection steps will generally be eliminated by reaction with the GAC.
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From page 256... ...
The chemical compounds entering an adsorption water treatment process consist of high-molecular-weight humic materials, lower-molecular-weight organic compounds of natural or industrial origin, and the products of previous treatment such as chlorination or ozonization. A portion of the chemicals can be removed by the clarification process and/or sorbed by the adsorbent or any microbial floe within the adsorbent bed.
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From page 257... ...
While there is ample evidence for the effectiveness of GAC in removing many organics of health concern, more data are needed in the quantification of any harmful health effects related to the use of GAC. This need, however, should not prevent the present use of GAC at locations where analysis of the water supply clearly indicates the existence of a potential health hazard greater than that which would result from the use of GAC.
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From page 258... ...
6. To what extent does competitive adsorption between trace organics with potential health ejects and the large concentrations of background organics, generally characterized as humic substances, influence the electiveness of GAC?
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From page 259... ...
The problem of competitive adsorption is significant when environmental samples are used in experiments in which specific organic compounds are removed by adsorption. A later section of this chapter addresses this problem exclusively.
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From page 260... ...
Instead, Table IV-1 presents a sample of available studies. The compounds in the table represent a wide variety of organic chemicals, including naturally occurring chemicals, industrial solvents, and compounds that have been identified in surface waters and waste streams in the United States.
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From page 261... ...
An Evaluation of Activated Carbon 261 TABLEIV-} Some Orgaruc Compounds for Which Detailed, WideRange Isotherms Have Been Determ~ned acetonef acetophenonea acridine orangea acridine yellowa adeninea adipic acida anetholea manisidinea benzenea h benzidineh benzidine dihydrochloridea benzoic acida benzothiazolea bromochloromethane' bromodichloromethanea g bromoforma,8 ~bromophenol~ S-bromouracila n-butanolb (all) -n -butylphthalatea carbon tetrachloridea g chlorobenzenea bis (2-chloroethyl)
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From page 262... ...
/` ,_, 1` '-a ~ ,_' f gul/~~r/um Coo, mobs// FIGURE IV-1 General and specific adsorption isotherms. From McGuire and Suffet, 1980.
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From page 263... ...
, List of Chemicals Submitted by EPA for Evaluation by the Safe Drinking Water Committee Toxicology Subcommittee (National Academy of Sciences, 1979) , and the Interagency Regulatory Liaison Group (19781.
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From page 267... ...
The third choice was data from column tests, which indicate only that the compound is adsorbed but do not indicate sorption capacity. Table IV-2 indicates that there are adsorption data pertaining to 40 of the 58 specific organics and classes of organic compounds.
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From page 268... ...
These clarification processes, which include coagulation, sedimentation, and filtration, are used at almost all surface-water treatment plants. Some organics collect on natural particles or particles that are formed during coagulation and, thus, are removed when the particles are removed.
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From page 269... ...
TOC removals of 6~7o were reported for pilot scale studies of Ohio River water treatment, 25% to 40~O removals from surface waters were reported in the Federal Republic of Germany, and removals up to 60% have been reported for fulvic acid, a predominant constituent of organic matter in natural waters (Kavanaugh, 1978; Semmens et al., 1978~. The best removals of organic matter by coagulation are generally achieved at pH values of 5 to 6.
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From page 270... ...
and associated with humic substances (Choi and Chen, 1976) , which may also be removed by coagulation.
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From page 271... ...
This process should be examined more closely at water treatment plants. Bank filtration, which is practiced in the Federal Republic of Germany along the Rhine River, may also enhance the adsorption process (see McCreary and Snoeyink, 1977, for a review)
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From page 272... ...
Much more efficient destruction of bacteria and virus then becomes possible, but the likelihood of forming chlorinated organics also increases. When the GAC adsorber removes biodegradable organic matter, not only is the disinfectant demand reduced, but also the possibilities of regrowth of microorganisms in the distribution system are decreased because the microbial food supply is reduced.
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From page 273... ...
The subcommittee recommends that: · Adsorption processes should be evaluated together with the clarification processes that will precede them in a water treatment plant. · Research should be conducted on the conjunctive use of PAC and GAC.
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From page 274... ...
To date, PAC has been used extensively in water treatment plants to remove organic compounds that cause offensive taste and odor (AWWA Committee Report, 19774. Very little has been done to evaluate its applicability to the removal of many other compounds of concern, such as THM precursors, TOC, specific chlorinated organ~cs, etc.
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From page 275... ...
COMPETITION ON GAC Competitive effects are created by adsorption of a wide spectrum of trace organics, which are found in water supplies and generated within the treatment process. These should be considered in order to estimate the overall efficiency of the GAC process.
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From page 276... ...
Such Resorption thus occurs completely independent of any eject of competitive adsorption and needs to be accounted for separately. This point will be discussed further in the section entitled "Pilot Plant Studies of Competitive Adsorption." Studies of Competitive Equilibrium Adsorption Reported laboratory studies of competitive adsorption have been summarized in Table IV-3.
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From page 277... ...
In such cases, the displacement of the humic substances by more strongly adsorbed components could control service time of the GAC bed. Entries 29-35 of Table IV-3 indicate that the concentration of humic substances has been much higher than that of the competing component in order to simulate the most likely condition to be encountered in practice.
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From page 278... ...
278 .~ Cal · ~ ·3 g ._ · o Coo o Cal On ~ of _ _ 8 ~Y~ i E o V 4)
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280 on Cal 4)
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From page 281... ...
281 ~ ~—' E- ~ ~^ ·^ ~ o oi ~ ~ ~ ~ ~ c ~ ~ _ q~ ~ _ q, ~ _ ~ _ ~ _ ~ _ ~ ._ ~ ~ ~ ~ ~ ~ ~ ~ i !
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282 Cry ~ ID _ ~ I_ ~ or ~ _ _ ~ ~ ~ ~ E ~ ~ ~ ~ ~ ~ ~ ~ Y s 3 ~ C E 9— C)
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283 ~ ~ ~ - ~ ~ s ~ ~ it c, co I ' C i ' i 5 , y ~s3~!
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From page 284... ...
Laboratory Studies of Competition in GAC Beds The objective of several recent studies of competitive adsorption has been to verify proposed dynamic mathematical models that can then be generally applied (Balzli et al., 1978; Crittenden, 1976; Crittenden and
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From page 285... ...
The extent to which the effluent concentration of the weaker adsorbate exceeds that of the influent is determined by both the relative adsorption behavior of the two components and their influent concentrations. There are complications in the verification of mathematical models to predict GAC bed performance, even for the simplest case of twocomponent mixtures.
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From page 286... ...
Because these are pilot plant studies, the influent to the GAC bed has not been constant either in composition or in concentration of trace organics. Consequently, the net result of competitive adsorption and simple reequilibration ejects is being measured in such studies.
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From page 287... ...
to evaluate performance of the GAC columns. Influent and effluent samples were taken over a total of 33 weeks of pilot plant operation at the Torresdale Water Treatment Plant in Philadelphia.
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From page 288... ...
288 o ~7 o ._ .~ o ~o E~ X x o 6 o r~ :e oo ° X ~ ° ~ ~ Ll)
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From page 289... ...
In other studies, the order of appearance of various THM species in the effluent of the GAC bed has been measured. At Stuttgart, Federal Republic of Germany, the effluent concentration of chloroform exceeded the influent concentration after 55 days of operation and remained significantly higher for 14 days (Sander et al., 1977~.
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From page 290... ...
However, the adsorbed amounts of each component were considerably different and all of the sorbed phase profiles were very flat, which indicates that the adsorption of these components was relatively weak. GAC treatment has been evaluated in full-scale testing for a total of 1 yr at the Jefferson Parish Water Treatment Plant on the lower Mississippi River (Brodtmann et al., 19801.
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From page 291... ...
Because the source of humic substances may be different for each water supply and may vary seasonally, pilot plant studies at specific locations over the seasons of the year will yield the most useful information on the ejects of competition. The wide spectrum of organics that have been identified in water supplies represent an equally wide spectrum of adsorption behavior.
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From page 292... ...
4. Pilot plant studies have shown that effluent concentrations of chloroform and, possibly, 1,1-dichloroethane and trichloroethylene exceeded influent concentrations to the GAC bed; however, from existing data, it is not possible to distinguish a displacement effect due to competitive adsorption from that due to reequilibration with a changing influent concentration.
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From page 293... ...
Although continued research is recommended, the more immediate and pressing need is to determine whether significant displacement of any organics of health concern occurs in the operation of GAC beds that are intended for treatment of drinking water. Although trace organics of concern in the raw water supply are identified and their concentrations and the variability in their concentrations are measured, pilot plant studies will still be necessary to confirm the relative order of breakthrough of each contaminant and to assess the importance of any displacement effect.
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From page 294... ...
3. What is the impact of microbial colonization of GAC beds on microbiological contamination of the product water?
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From page 295... ...
Included among these organics were dinitrobenzenes and phenols, phenyldiamines, trichlorophenol, nitroanilines, and naphthylamines. In all of the studies that were found in the literature, the experimental conditions were not those to be expected in treatment of drinking water.
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From page 296... ...
There has been no evidence to suggest that any of the suspect carcinogens are acted upon by microbial action in the GAC bed. EVIDENCE OF MICROBIAL ACTION ON GAC BEDS IN WATER TREATMENT Much of the recent interest on the effect of microbial activity on GAC performance stems from European research and experience.
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From page 297... ...
Accordingly, this carbon dioxide production is equivalent to 1.4 mg/liter of organic carbon being removed at steady state in a contact time of 30 min. During actual operation of the GAC beds during the last 9 months of the 3-yr pilot plant study at Bremen, the carbon dioxide production was equivalent to removal of approximately 1.4 mg/liter organic carbon.
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From page 298... ...
of full-scale GAC beds at the Jefferson Parish Water Treatment Plant, which is located on the lower Mississippi River, Brodtmann et al.
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From page 299... ...
There has been no evidence to suggest that microbial action removes specific organics that would otherwise escape GAC treatment. On the other hand, it appears that service life of a GAC bed can be extended by microbial action if performance is measured by removal of total organics, e.g., total organic carbon, UV absorbance, or potassium permanganate demand.
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From page 300... ...
A nearly steady-state removal of approximately 80% of the UY-absorbing substances was obtained in pilot plant GAC beds after preozonization. However, in parallel operation of the full-scale plant, in which breakpoint chlorination was followed by preozonization and GAC beds, the removal of the absorbing
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From page 301... ...
Approximately 1.5 mg/liter DOC was removed during the last 7 months of the pilot plant study after a contact time of 30 min (Jekel, 1977~. The extent to which microbial action reduced organics agrees with the findings of Eberhardt et al.
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From page 302... ...
Similar findings were obtained in pilot plant studies of GAC beds in which ozonization of the effluent failed to reduce the THMFP. However, as noted earlier, measurements after GAC contact indicated that the addition of ozone prior to GAC reduced the THMFP (U.S.
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From page 303... ...
EFFECTS OF PRECHLORINATION ON MICROBIAL ACTIVITY IN GAC BEDS For chlorination to have a detrimental effect on microbial growth within a GAC bed, residual chlorine must be present. The catalytic dechlorination reaction on GAC counteracts this problem (Suidan et al., 1977~.
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From page 304... ...
There are general rules to predict this effect. Microbial Activity on GAC in Wastewater Treatment From pilot plant studies at Pomona, California, Parkhurst et al.
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From page 305... ...
Because the concentration of biodegradable organics is far greater in wastewater than in water supplies, the extent of microbial activity on GAC beds used in wastewater after either conventional primary or secondary treatment should also be greater. Ying and Weber (1978)
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From page 306... ...
has shown that adhesion of bacteria can be dependent upon their ability to produce suitable bridging polymers. BACTERIAL GROWTH ON GAC BEDS Standard plate count methods for bacteria from crushed and homogenized GAC have been used for quantitation.
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From page 307... ...
showed that the bacterial counts in GAC beds reached maximal numbers in 20 to 30 days, i.e., approximately 108 colony-forming units per gram of GAC at 25°C. While fewer colonies formed on sand than on unactivated carbon, the differences were not as great as reported earlier (Van der Kooij, 1976~.
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From page 308... ...
reported plate counts of less than 50/ml (3-day, 20°C test) in the effluent of GAC beds; however, in pilot plant tests, he found higher counts (from 1,000 to 10,000/ml)
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From page 309... ...
at the Lawrence, Massachusetts, waterworks, where a transient increase in numbers of bacteria in the effluent was observed following backwash. In other studies, 15 months of pilot testing at the Amsterdam waterworks showed that GAC beds without preozonization produced bacterial counts of less than 1,000/ml.
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From page 310... ...
A few are only now emerging as significant environmental problems. Microbially produced toxicants have not been identified in the treatment of drinking water by GAC.
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From page 311... ...
Although there are no studies of cometabolism on the GAC surface, it seems plausible that refractory organic molecules entering water from agricultural, industrial, or domestic operations or generated as a result of chlorination could be acted upon. This would give rise to products that are themselves not suitable substrates and are not attacked readily by microorganisms on
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From page 312... ...
The addition of endotoxin to the drinking water reverses this protective effect. In addition, animals on a choline-deficient diet become very susceptible to the lethal and hepatotoxic effects of endotoxin (Nolan and All, 1968~.
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From page 313... ...
Measurements of Endotoxin in Drinking Water The amount of endotoxin in drinking water has been measured with the limulus lysate test. DiLuzio and Friedmann (1973)
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From page 314... ...
The measured levels are very low and should pose no risk. Thus far, evidence of microbial activity in GAC beds has largely been indirect.
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From page 315... ...
PRODUCTION OF NONBIOLOGICAL SUBSTANCES BY OR WITHIN THE GAC BED One potential source of chemical breakthrough from a GAC column can be the chemical changes on GAC surfaces. This section evaluates the significance of this potential source of toxic organic chemicals in drinking water.
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From page 316... ...
The chemical changes that are mediated by carbon are not only the result of oxidation and reduction reactions, but can stem from catalysis on the carbon surface. The use of carbon as a surface catalyst and catalyst support in industrial processes is well documented.
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From page 317... ...
The oxidation reactions catalyzed by GAC yield products that are found in water supplies and would be expected in drinking water processed without the application of GAC. ORGANIC REACTIONS MEDIATED BY CARBON Carbon catalyzes the oxidation of sulfide in solution, glucose in the presence of phosphoric acid, oxalic acid, malonic acid, amino acids, phenylthiocarbamide, ascorbic acid, uric acid and its derivatives, and mercaptans (Garter and Weiss, 1959; Ishizaki and Cookson, 1974; Larsen and Walton, 1940; Rideal and Wright, 1925, 1926; Weiss, 1962~.
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From page 318... ...
Rideal and Wright (1926) reported that in aqueous solutions substances containing but one polar group, such as alcohol, formic acid, and the higher fatty acids, do not undergo oxidation at the surface of charcoal.
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From page 319... ...
These studies, along with those of temperature influences, clearly illustrate the effect that activation and regeneration procedures have on carbon's catalytic behavior. Thus, the history of activated carbon prior to regeneration is important.
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From page 320... ...
) indicates the carbon surface.
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From page 321... ...
, the oxidation of the carbon has become so extensive that a resulting end product produces a visible dark color in the aqueous solution. This extent of reaction is not expected to occur within 2 to 3 yr under typical operating conditions at a water treatment plant (i.e., chlorine enters the carbon adsorber at a concentration of 1 to 2 mg/liter or less)
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From page 322... ...
Only approximately 5% of the amount taken up could be eluted as oxygen. The reaction between oxygen and carbon is important, because it indicates that not all oxygen that is removed during adsorption can be attributed to biological activity and that the nature of the carbon surface may be altered during the adsorption process.
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From page 323... ...
Unfortunately, the undefined nature of the trace metals in water supplies makes it extremely difficult to predict the efficiency of carbon to adsorb metals (Huang and Wu, 1975; Kunin, 1976~. For example, many of these metals are bound or complexed with the various organic substances in water, thereby forming complexes that are completely unrelated to the simple ionic states that have been reported for these metals in classical texts on inorganic chemistry.
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From page 324... ...
Many of the methods for preparing activated carbon catalysts are similar to processes occurring in water treatment and carbon regeneration. Thus, the importance of the above carbon-metal catalyses in water purification is unknown.
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From page 325... ...
(1979) have reported continual bleed-o~of carbon fines, primarily of those ranging from 2.5 to 25 ,um diameter, from a GAC column utilized in an up-flow, countercurrent, packed bed contractor at Water Factory 21 Advanced Wastewater Treatment facility in Orange County, California.
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From page 326... ...
It would follow that carbons used in the treatment of wastewater may adsorb significant quantities of various metals that become incorporated in the carbon structure during regeneration procedures. Thus, the recycling and regeneration of activated carbon could result in a material that is radically different from the virgin material.
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From page 327... ...
5. Studies should be conducted to determine levels of carbon fines that pass into drinking water and their biological significance.
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From page 328... ...
Since then, GAC has been installed in approximately 60 potable water supply systems to control taste and odor. However, use for this purpose has generally not required GAC regeneration.
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From page 329... ...
Commercial Regeneration Procedures During the purification of waters and wastes, impurities in the solutions collect in the pores of the carbon. After a while, contaminants begin to break through the GAC bed, and the spent carbon must be reactivated.
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From page 330... ...
The compounds adsorbed during water treatment should be removed by thermal regeneration, thereby making GAC a most attractive alternative. While carbons can be regenerated, documentation is needed for changes due to regeneration in hardness, pore size distribution, ash and metal ion buildup, and adsorbability for compounds present in water supplies.
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From page 331... ...
CHEMICAL CAGES DURING STOOGE During storage, activated carbon undergoes chemical changes as a result of reactions with atmospheric oxygen. The reactions that occur at room temperature bring about an aging process in which the atmospheric oxygen reacts chemically with the carbon surface.
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From page 332... ...
It is not anticipated that PAH would be released to drinking water in concentrations that are potentially harmful to health, because the total amount is so small and they are strongly adsorbed to activated carbon. Clearly, additional research is needed on virgin activated carbons, as well as regenerated carbons, so that the leaching potential of toxic chemicals can be evaluated completely.
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From page 333... ...
These studies were also performed with carbons used in wastewater treatment. In brief, two general categories of exhaust emissions must concern the operators of regeneration facilities.
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From page 335... ...
335 1 1 1 1 ~ ~ ~ o no Cal on on ~ 1 1 1 1 1 1 1 1 1 1 1 1 10 1 no no so .
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From page 336... ...
Regeneration procedures must be evaluated to determine their influence on adsorption capacity, catalytic potential, leaching of metals
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From page 337... ...
ADSORPTION EFFICIENCY OF OTHER ADSORBENTS This section contains an evaluation of the ability of other absorbents to adsorb trace organic compounds during the treatment of drinking water. Two distinctly different processes are considered.
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From page 338... ...
338 'A Z ~ ~ ·~ I: Cal a _ it Cal · c I_ o .~ o a: ~ A; ~ ._ U)
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From page 339... ...
Until recently, much of the experience with synthetic resins for potable water concerned the use of cation exchange resins to soften potable water. These water-softening resins remove few of the organics.
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From page 340... ...
For example, some anion exchange resins, particularly the strongly basic resins with small pores, can be poisoned after exposure to high levels of humic materials (Abrams, 1975; Kunin, 1976~. Apparently, the large molecules enter the pores of the anion exchange resin and are retained because they have a high affinity for the ion exchange sites and low rate of diffusion within the resin.
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From page 341... ...
In view of the success that has been achieved with ion exchange resins to remove humic substances from water for various industrial purposes (Davis, 1977; Hinrichs and Snoeyink, 1976) , it is logical that the technology be given consideration for the processing of drinking water prior to the chlorination process.
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From page 342... ...
(1980) compared the adsorption of commerical humic substances on Diamond Shamrock A-7 and ES-561 weak base anion exchangers with that on Rohm and Haas IR-904 and IR458 strong base anion exchange resins.
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From page 343... ...
PILOT PLANT STUDIES Kolle (1976) described how the strong base anion exchanger Lewatit, MP-500 A (Bayer, Leverkusen)
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From page 344... ...
Wood and DeMarco (1980) studied the removal on XE-340, GAC, and IRA-904 anion exchange resins of purgeable organics and THM precursors from raw groundwater, after lime-softening and in finished water.
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From page 345... ...
Regeneration of Anion Exchange Resins Regeneration and disposal of spent regenerant solution are major concerns involving resin use. A strong brine and/or alkali regenerant is used for strong base anion exchange resins.
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From page 346... ...
The specific situation for drinking water application has yet to be studied. Nitrosamines and Ion Exchange Resins .
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From page 347... ...
Fiddler and Kimoto (1979) concluded that the source of nitrosamine in municipal drinking water that had been exposed to deionizing resins appeared to be associated with low levels of nitrate and an unknown soluble substances that promoted nitrosamine formation during the deionization process.
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From page 349... ...
describes a model for the removal of chlorofo~ from water by XE-340 where the resin macropores allow low-molecularweight organics to diffuse to the micropores, while large molecules or humic substances cannot enter the micropores. Neely presents evidence to suggest that the high adsorptive capacity of XE-340 for chloroform is due at least partially to absorption.
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From page 350... ...
used a 10.2-cm-long, 15-ml bed volume of XE-340 and XAD4 in columns to follow the breakthrough of 1 ppm of chloroform ~~ in drinking water with 2 ppm TOC. The flow rate was 4 gpm/ft3.
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From page 351... ...
(1978a,b) studied Filtrasorb-400, XAD-2, and XE-340 in pilot columns as a posttreatment of chlorinated Philadelphia drinking water from the Delaware River.
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From page 352... ...
the column removed all THM compounds for 10 weeks from an influent that had a THM concentration of approximately 125 ,ug/liter. The effluent concentration rose to 25 ,ug/liter in the next 20 weeks as the influent concentration dropped steadily to 50 ,ug/liter.
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From page 353... ...
However, XE-340 did remove 24% of the THMFP from raw water. Competition between organics with potential health effects is not known at present.
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From page 354... ...
Laboratory and pilot plant studies have shown that strong base anion exchange resins can remove humic materials as well as or better than GAC. The adsorption capacity is a function of the composition of the aqueous solution.
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From page 355... ...
POLYMERIC ADSORBENTS Experience with synthetic resins and polymeric absorbents to remove organic compounds from drinking water is limited in comparison with the use of GAC or PAC. Laboratory studies and the few recent pilot plant studies indicate that the synthetic carbonaceous absorbents of the XE-340 type do not have the broad-spectrum adsorption properties of GAC and that they selectively adsorb lower-molecular-weight organics but apparently do not readily adsorb humic material.
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From page 356... ...
estimated that 90% by weight of the total organic matter in drinking water is composed of highmolecular-weight organics. This would correspond to natural organic compounds of little-known toxicological importance (Class V; U.S.
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From page 357... ...
This discussion indicates that effluent concentrations are dependent on influent concentrations, in addition to the adsorption dynamics on the column, and would therefore tend to vary. In addition to monitoring influent and effluent, it may be desirable to monitor the contents of the GAC bed itself to determine when breakthrough will occur.
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From page 358... ...
Monitoring Specific Pollutants of Potential Harm to Health Since 1975, a massive effort to identify organic compounds in drinking water by gas chromatography/mass spectrometry (GC/MS) has resulted in an inventory of volatile, relatively nonpolar, soluble organics that are isolated from water by volatilization, solvent extraction, or solid phase adsorption (Keith, 1976~.
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From page 359... ...
(in press) obtained comparable results regarding the overall precision of the purge and trap analysis and the three liquid-liquid extraction methods for routine monitoring of drinking water.
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From page 360... ...
These methods must be supplemented by specific analyses for compounds that are not isolated by the specific extraction method. The complex group of trace organics in the extracted sample is chromatographed, and a sample profile or fingerprint is obtained.
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From page 361... ...
These workers describe NVTOC as a "reasonable indicator" of THM precursors in drinking water in an 80city survey. They reported that some correlation existed between NVTOC and CCE data but these data were rather scattered.
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From page 362... ...
In the Federal Republic of Germany, TOX has been used to monitor breakthrough behavior of activated carbon filters and to determine the necessity of reactivation in drinking water treatment plants (Kuhn et al., 1978a,b)
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From page 363... ...
In drinking water the purgeable organic halogen can be 25% of the approximate CAOX as C1 organic halogen. A differentiation should be made between the TOX measurement of raw water and finished drinking water after chlorination.
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From page 364... ...
These samples would be be compared by chromatographic profiles augmented by GC/MS analyses. This approach would monitor specific organics with health implications at each water treatment plant.
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From page 365... ...
On a weight basis, only approximately 10% of all the organic compounds in drinking water have been identified (National Academy of Sciences, 1977~. The low-molecular-weight polar organ~cs and the nonvolatile high-molecular-weight organics cannot be analyzed by the above-mentioned methods.
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From page 366... ...
1973. World Health Organization, European standards for organic matter in drinking water.
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From page 367... ...
1980. Critical study of large-scale granular activated carbon filter units for the removal of organic substances from drinking water.
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From page 368... ...
1977. Electro-regenerated ion-exchange deionization of drinking water.
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From page 369... ...
use in municipal water treatment in nitrosamine formation in drinking water. EPA-570/9-78-008, April 18, 1979, IAG # EPA-D7-01130.
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From page 370... ...
1968. Adsorption of organic ions by anion exchange resins.
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From page 371... ...
1977. Microbiological aspects of drinking water supplies.
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From page 372... ...
1976. Use of macroporous ion exchangers for drinking water purification.
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From page 373... ...
1978. Assessment of unit processes for the removal of trace organic compounds from drinking water.
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From page 374... ...
Safe Drinking Water Committee, National Research Council. Washington, D.C.
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From page 375... ...
1978. Evaluation of direct aqueous injection method for analysis of chloroform in drinking water.
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From page 376... ...
1974. Removal of some pesticides from drinking water by adsorption methods.
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From page 377... ...
1978a. Evaluation of the capability of granular activated carbon and XAD-2 resin to remove trace organics from treated drinking water.
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From page 378... ...
1980. Applications of activated carbon to drinking water treatment: pilot plant.
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From page 379... ...
Presented at the Conference on Oxidation Techniques in Drinking Water Treatment, Karlsrahe, 11-15 Sept.
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From page 380... ...
Development of a teflon helix continuous liquid-liquid extraction apparatus and its application for the analysis of organic pollutants in drinking water. ASTM Special Technical Publications.
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