e
e
Dnnkmg-water treatment with ozone Ozone is a powerfid disinfectant and ox&, but its chemical byproducts need to be better understood
WiUiam € Glaze I. Universig of colifontia, Los Angeles Los Angeles, Calif. 90024
Ozone came into use as a drinking-water disinfectant as early as 1906 at the Eon Voyage plant in Nice, France; since then, more than lo00 facilities throughout Europe have adopted the practice (1). Some use m n e as the primary or sole disinfectant, others use it as an oxidant for the control of flora, odor, and color and to reduce the manganese and iron content of drinking water. Lately, engineers at European plants are finding that preomnation enhances the flocculation of suspended lhticles in snrface waters, and its use for this purpose is expanding. The use of ozone in North America, however, has only recently begun to gain acceptance. According to Rice, the number of ozonation plants in the United States has increased fromfive in 1977 to 20 in 1984 (1). During the same period, the number of plants in Canadaincreased from 23 tonearly 50. Large plants are beginning operations this year in Los Angels and in Hackensack, N.J.; one plant is scheduled to open in Myrtle Beach, S.C., in 1988 (lhble 1). The Los Angels plant contains one of the largest m n e prcduction faciities in the world. 224 Envlmn. Sci. Rchnol.,M. 21.
No. 3,1887
Wi~X/87mi.OZ?4$LIi,50/0 @ i987American Chemical Society
One major factor in the increased interest in ozone is the need to decrease the use of free chlorine in water treatment in keeping with legislated maximum contaminant levels (MCLs) for trihalomethanes (THMs). For many years, free chlorine has been the disinfectant of choice in North America. Chlorine is not only a disinfectant, it is a powerful oxidant. Unfortunately, chlorine also produces byproducts, such as THMs, that can be harmful to human health. The need for THM control has forced water utilities to search for appropriate substitutes. Water treatment by chloramination (the c o m b i i o n of free chlorine and
ammonia) has emerged as the most popular alternative disinfection process because chloramines do not form THMs. Chloramines are weak oxidants, however, so stronger oxidants, particularly ozone and chlorine dioxide., are being considered as substitutes for chlorine at the beginning and middle of the treatment process. Ozone is gainiig in popularity for other reasons as well. In tests in which ozone has been compared with chlorine, ozone has been shown to he superior to chlorine as a coagulant (2). It also appears w form much smaller amonnts of mutagens than either chlorine or chlorine dioxide do (3).In addi-
tion, when ozone decomposes it generates radical intermediates that have much greater oxidizing power than ozone itself does. The use of chemical oxidants to disinfect water is shown schematically in Figure 1. Ozow generation Because ozone is an unstable gas, it must be generated where it will be used. The most common technique for generating ozone is the cold plasma discharee method. in which ozone is for& by decdmposition of diatomic oxygen: O2(corona discharge)
.o
-
(1) O.+&-OO, (2) Figure 2 is a doubletube owne.generating unit commonly found in largescale applications. Large-scale generators can contain as many as 400 double tubes, and they can generate 600 kgl day of owne when dry oxygen is the feed gas. With air, the yield of ozone is about 50% of that generated with oxygen. In both cases the feed gas must be oil free and have a low dew point (-52 OC to -58 OC). Recent'advances in o m e generation bv the c ' 'asma
0.-k
Postdisinfectic
Envlmn. Sd. Technol., W. 21, No. 3.1987 225
. I
method, which have been reviewed by with the concentration of ozone in the Coste and Fiessinger (4, include the gas phase, P is the panial pressure of development of generators that operate ozone in the gas phase, H is the Henry's in the medium frequency range (600 law constant for ozone (0.082 atm m3 Hz);modifications in the design of the g.mol-I at 25 OC), and h a is the overtubes, particularl~the use of ceramic all transfer coefficient. The upper rather than glass dielectrics; and im- curve in Figure 4 is a plot of owne proved electronic system for control- concentration in the aqueous phase in a ling current. static reactor as owne-containing gas is Ozone also can &':generated by introduced. The initial slope of the line means of ultraviolet (W) light (less is related to ha, which is assumed to be than 200 nm) generated by arc dis- 0.36 g m o l m-3 m i d in this case. charge lamps, in much the same manUnder actual conditions in a treatner as ozone is formed in the upper ment plant, chemical reactions in the atmosphere (Equations 1 and 2). Al- liquid phase consume ozone. Thus, though photochemical units cannot gen- Equation 3 must be modified to account erate owne at concentrations as high as for the loss of ozone by the following those produced by cold plasma genera- chemical @ways: tors, W generaps may be competidC/& = ka(P/H - C ) tive for small-scale systems because k(C)(Ho)- k(S,)(C) (4) they require little capital investment and are relatively easy to maintain. Here, k, is the rate. constant for the d e composition of m n e and the term on If.ansfer of mne into water the extreme right is the sum of all the h n e produced by the cold plasma rate terms for chemical reactions that discharge method is present in air or involve sub st rat^ (S,) in the water that oxygen at concentrations of 1-3 56 and consume owne. 3-756, respectively. These values corThe.lower curve in Figure 4 is a plot respond to.11-90 g m n e per standard of the mass transfer of ozone into the cubic meter of air or oxygen. A number reactor. It takes into account only the of devices have been used to transfer middle term in Equation 4 (autodecomozone into water; the most popular is position of ozone). A rate constant of the counter-current sparged column 70 M-I sd is assumed (5).Rapid reac(Figure 3). Other system include the tions in the liquid phase will drive stirred-tank reactor with diffiser, meth- owne dissolution; that is, the faster ods that increase mass transfer through owne is umsnmed in the liquid phase, a combination of small bubble size and the faster it will cross the gas-water hydrostatic pressure, and the in-line boundary. This is likely to be sign& static mixer. cant to the design of reactors that are In the absence of chemical reactions, lxwd on the rapid decomposition of mass transfer from the gas phase to the owne into radicals. aqueous phase can be described by -water treatment Equation 3: Ozone a s a disinfectant. h n e sufdC/& = h a ( c 1 - C ) = fers from two major limitations as an hNPm c) (3) alternative to Chlorine-Fiit, it is unstain which C is the concentration of ble in water; it decomposes to oxygen ozone in the liquid phase, C*is the liq- at a rate proportional to the pH of the uid-phase concentration in equilibrium water. For example, at pH 8, which is
-
228 Envimn. Sci. Tnchnol.. MI. 21, No. 3, 1987
typical of many drinking-water sup plies, its half-life is less than one hour, too short to ensure that a residual disinfectant capcity will remain at the far reaches of a large distribution system. Despite its short lifetime, however, m n e is particularly effective against recalcitrant micmorganisms. It is more effective than is chlorine for removal of Ginrdin (an organism that causes a gastrointestinal disease), viruses, and certain forms of algae (6). second, ozone reacts with natural organic substances to produce low-molecular-weight oxygenated byprcducts that generally are more biodegradable than their precursas are. These s u b stances will promote biological growth in a distribution system ("regrowth"), further limiting the disinfection e a cacy of ozone. For these reasons, owne should be used in combination with other disillfechtsthat maintain an active midual for longer periods, and it should be combined with some mezhod of fdtration for removing b i e degradable material. (hone as 811 oxidant. oume can oxidize many nuisance compounds or p tential toxicants in water supplies. These include natural color bodies, compounds that produce Unpleastastes or odors, maIlgame(II) and iron@, and phenolic materials. Ozone also coagulates natural water constituents. For these reasons, Ozone has been adopted as the preoxidant in the new Los Angeles treatment facility, where pilot studies have shown that preaonation substantially improves the fdtration of the raw water, thereby reducing the need for other chemical coagulants and allowing shorter basii and fdter contact times (2, 7). Comparison tests have shown that ozone is substantially superior to chlorine for these purposes. Although the mechanism of coagulation by m e is not clear, several possibilities have been suggested. One possi-
r
bility is the oxidation of metal ions to yield insoluble forms such as F e o . Another is oxidation of humic material to form more polar or chelating grcups, which induce caagulation. Finally, oxidative dissociation of natural organic material from colloidal clay particles, which destabilizes the colloids, has been suggested. Further research is under way, and more information should be forthcoming (8).
Chemistry of OuMe In referring to ozone as an oxidant, chemists often cite the very high negative value of the t h e d y n a m i c free
energy of reactions, as set forth in Quation 5:
4 + W ++ 2 s
-
H20
Q (AQ = -400 kJ/mol)
+
-
(5)
in which AQ is the free energy. Although this very large negative value defines thepotmrial for m n e to act as an oxidant, the usefulness of ozone in water treatment is limited by the kinetics of its reactions. In some cases the kinetics are favorable enough to make ozone a practical oxidant, but this is not generally the case. When mne reacts with typical water contaminants, rate constants can vary by more than eight orders of magnitude ranging from lo7M-l sd for the phenolate anion to 1WI M-l s-I for tetrachloroethylene (9,10). Ozone reacts best when it can act as an electron transfer acceptor (for the oxidation of metal ions), as an electrophile (for the oxidation of phenol and other activated aromatics), and as a dipole addition reagent (by addition to carbon-carbon multiple bonds). The rates of oxidation of organic compounds by ozone are severely depressed, however, by electron-withdrawing substituents. For example, m n e reacts poorly with most aliphatic organic halides, such as chloroform. Ozone also does not react with aliphatic compounds other than those that have easily oxidized groups, such as aldehydes and ketones. Moreover, m n e is not a good oxidant for most specific organic materials in water trea!ment. Rice has, however, pointed out several exceptions: Ozone has been used to oxidize sulfides, nitrites (to nitrate), cyanides (to cyanate), and some dekrgents and pesticides (11). The radical chemistry of ozone. Recent studies from several laboratories support the application of ozone as a chemical oxidant for water and w a s e water treatment. Basic research has shown that ozone decomposes by a complex mechanism that involves the generation of hydroxyl radicals, which are among the most reactive oxidizing species (Table 2). Other studies have
ha 0.36 min;', A W i u t decomwltion 0 W i decomposition = m M-' s-'
%LE2
action rate constantsof select4 organic material1
involved ozone and some other agent or process, such as W radiation, hydrogen peroxide, or ultrasound, to develop water treatment processes that are substantially more powerful than ozone is alone. These new processes are related chemically to the decomposition mechanisms so elegantly elucidated by H o i e et al. (5, 12-14) and Forni et al. (15) and anticipated much earlier by Taube and Bray (16). The decomposition of ozone in pure water is shown in Figure 5 as a cyclic chain mechanism; the overall stoichiometry is shown by Equation 6: 2 4
-
39
(6)
Decomposition can be initiated by hydroxide ions, formate ions, or a variety of other species, and in pure water the chains are very long (17). A single initiation step can cause the decomposition of hundreds of molecules of ozone before the chain ends. Ozone is unstable at high pH values because the decomposition process is initiated by hydroxide ions. In the presence of the usual water Contarmnants, such as bicarbonate ions and natural organic matter, the cyclic chain shown in Figure 5 can be broken. In the case of bicarbonate, the reaction (Quation 7) is a simple electron transfer process with the hydroxyl radical: Envimn. si.Technol.. MI. 21, No. 3,1907 227
superoxide ion (17, 19). But they are also promoted by other water contaminants, such as metal ions. Under practical conditions, the dose of ozone is never enough to satisfy the ultimate demand, and the reactions discussed above generally will stop when the supply is depleted. vpically, this will be long before the organic substances have become mineralized to carbon dioxide. Catalytic ozonation pwcesses Ozone can be combined with other
HC4-
+ OH
-
OH-
+ HCQ
(7)
The net effect is to retard the decomposition of ozone. Hoigni and ccFworkers have shown that increasing the carbonate ion concentration from 10g/m3 to 1oOg/m3 in phosphatebuffered water will approximately double the half-life of m n e at pH 8 (5). Ozone and natural organic matter. When natural organic materials are present, ozone dewmpsition is accelerated, and the chemistry becomes more complex. There are several reactions that can occur when ozone is added to natural waters: Free or complexed metal ions can be oxidized, possibly by oneelectron transfer processes, to yield the mnide radical anion, which can then initiate the chain decomposition of owne (17). The hydroxyl radical can react with aromatic groups in the humic molecules, yielding hydroxylated forms, which are then more susceptible to further attack by ozone (18). The hydroxyl radical can react with aliphatic side chains or fatty acids, usually by hydrogen atom abstraction reactions. The organic radicals formed will generally add dioxygen to form organic peroxides, which decompose by eliminating the superoxide ion. The superoxide ion can tben reenter the chain to cause more decomposition of ozone and in228 Envimn. Sci. Techmi.. Vol. 21, No. 3. 1887
creased formation of hydroxyl radicals (17, 19).
Ozone can react with carbon-carbon double bonds in the humic molecule (by the usual pathway [Zq), first to yield peroxidic intermediates and then to give hydrogen peroxide and carbonyl products. Ozone and synthetic organic substances. If anthropogenic organic materials are present in water, the same reactions can result in the destruction of these species by ozone, hydroxyl radicals, or both. In general, the hydroxyl radical reacts with organic compounds at rates that essentially are controlled by diffusion; rate constants pically are between lo7M-' s-I and 10alM-' s-I (lhble 2). Thus, it is possible in principle to induce m n e to act according to an entirely different kind of chemistry than it usually shows in nonaqueous solvents. Indeed, in actual water treatment applications m n e probably never acts according to the classical chemistry that one f i d s in textbooks that describe nonaquecus systems (20.21). Classical reactions can occur,but there also will be a parallel set of reactions, often interacting with the first, involving the radical intermediates (especiaJly the very reactive hydroxyl radical), as shown in Figure 5 . As Staehelii and Hoigni have noted, these radical processes are promoted by the products of the classical reactions, especially the
processes or agents for more effective water and wastewater treatment than is possible by ozonation alone: radiation (22-25), ultrasound(26), hydrogen peroxide (27,28),or metallic catalysts, such as reduced iron (29). Each of these processes probably involves chemistry similar to that discussed by Hoigni et al. for the basecatalyzed dewmpition of m n e (5, 13. 14). Hoigni has identified the hydrogen peroxide anion H a - as one of the species that can initiate the cyclic chain process shown in Figure 5. This apparently accounts for observations that hydrogen peroxide increases the effectiveness of ozone for removal of organic substances during water treatment (27. 28. 30). k+on and Gl&e (25,31) have verified the earlier work of Taube (32), who showed that the W photolysis of ozone in water yields hydrogen peroxide rather than two hydroxyl radicals, as occurs in wet air. Thus, the ozoneUV process resembles the owne-peroxide process but offers the additional advantage that direct photolysis and photosynthesized processes also occur to decompose organic substrates. These ozonation processes are attracting increasing attention because of their ability to destroy organic substances in water. Figure 6 illustrates the destruction of several chlorinated organic contaminants by ozone with and without UV radiion. (The loss of chloroform [CHC13] and dichlorobm momethane [CHC12Br] is caused by sparging, not by direct reaction with ozone.) In general, UV exposure accelerates the decomposition of these substances, although the decay of hexachlorobiphenyl (HCB) is retarded. W s of theseprocesses now in progress or in planning stages aim at applying them to the renovation of groundwater contaminated with synthetic organic compounds. The advantage is that these processes destroy the contaminants instead of transferring them to another phase, as do air snipping, granular activated carbon (GAC) adsorption, and reverse osmosis. The
commercial feasibility of these p m esses is still uncertain.
r
Healtb effecta studies Several studies have attempted to determine the compounds formed by ozonation alone and in combination with other processes in natural waters. Most of these studies have yielded no surprises.Aldehydes, carboxylic acids, and other aliphatic, aromatic, and mixed oxidized forms have been observed. None appear to cause significant toxic effects at the concentrations expected in m n a t e d waters (33). Most bioassay screening studies have shown that mnatedwater induces substantially less mutagenic activity than chlorinated water does. One study showed that omnation decreased mutagenic activity in Rhine River water, whereas the activity increased after the water was treated with chlorine and chlorine dioxide (3). These studies do not necessarily remove all concern about the safety of omnation for drinking-water treatment. There may very well be byproducts formed that harm human health,they simply have not yet been found. It is instructive to recall that chlorine was used for decades before T H M s were discovered in drinking water. The situation with ozone byproducts may be analogous. AU of the health efFects studies carried out so far have used preconcentration techniques that may cause some byproducts to decompose during workup. These byproducts include peroxides, epoxides, and conjugated unsaturated aldehydes. Further research is needed if mnation is to be adopted on alarge scale in the United Stam. k I K and biilogid treatment
The byproducts formed by oxidation with ozone and catalytic ozonation processes are g e n e d y more amenable than are those formed by chlorination processes to removal by biological treatment pnxzsses-that is, they are more biodegmdable than their precursors are. This is a disadvantage if m n e is to be used as a terminal dishfectant. If applied before fdtration, however, oune can promote biological activity in the fdter that will remove organic matter and THM precursors; in the final step, the water can be treated with chlorine or another disinfectant. ozonation in advance of fdtration with GAC has been called the biological activated carbon process. This combination of pnxzsses has been studied in Western Europe ( 3 4 3 9 , where it was pioneered, and in North America (37-38). DiGiano recently reviewed the subject and concluded that the combmtion of p m n a t i o n and GAC fdtration removes organic substances but
that the effect is not as dramatic as some of its proponents claim (39). Nonetheless, there are several treatment plants in Europethatareusing the OZonGGAC process, and active removal well beyond the period of GAC exhaustion is reported (36). It is possible that the use of catalytic oxidation pmcesses will increasebiodegradabdity even more than ozone can alone.
k I K ~ e o s t s Although m n e systems are capital intensive, they offer significant economies of scale. Costs of generating and cnua*ing systems vary from one site to another, but about $24OO/kg of mne/day is a plausible figure for a plant producing mkg/day of ozone. Thiswouldbeemnghtotreat 100million gal/day of water (4.4 mVs) with an m n e dose of 2g/m3 (2 ppm) and would q u i r e a capital investment of approximately $2million. Capital costs for systems generating 0-5kg/h of ozone are about three times those that generate more than 50 kgh.
operating costs of Ozone plants also vary, but a range of $0.001-W.oM/m3 seems io be typical of most plants in the United States. Oune pmduction is energy intensive and g u h s 16 kWh/kg and 24 k W k g of m n e for oxygenand air-fed systems, respectively. Total ueabnent costs for ownation are in the range of $0.04/m3to $0.06/m3of water for plants that process IO million-gal/ day and 100 dion-gal/day (0.44m3/s and 4.4m3/s), respectively, assuming an ozone dose of 1 ppm.
For the future It is likely that the use of m n e in water trearment will increase substantially in North America. In the near tim,its principal application is likely to be similar to the new Los Angelplant, where ozone is used a coagulant aid. Ozonation also will fmd new applications as a substitute for prechlorination for control of biofouling, a t e and odor control, and manganese removal, particularly if the maximum contaminant levels for THMs arc lowered. Envimn Sci. Technd , Vol 21, NO 3,1987 229
Porphyrins Exdted States and Dynamics
N~W!
Martin Goutarman, Editor. University of Washington Peter M. Rentzepia, Ed&, University of California at inrine Karl D. Straub, Editor, John L. McClelland Veterans’ Hospital Examines theoretical and expeflmnla1 studies o n excited slates of wrphyrins as presented by classiwl B ~ t r o B C o p yphotochemistry. , very lransient spectroscopy, and theoretl. caI Calculations of electronic energy levels and dynamics, Offers the newest work in the most active area. ot research in po hyrin excited mtes. An inva&e reference for those Interested in porphyrin chernlstry and excited states dynamics in general.
The control of THM precursors, groundwater chlorcorganics, and other iynthetic organic materials by OMlion is not likely to be successful. Advanced catalytic aonation processes, however, are showing promise for such ipplications and will be studied more thoroughly. As the use of m n e for drinking-water treatment increases, particular attention will have to be paid to the use of appropriate analytical methods and separation procedures that will give an ac:urate representation of the substances present after oxidation-not just those that survive the work-up procedures. Df the byproducts of particular interest, Unsaturated aldehydes, epoxides, and peroxides are the most likely to cause harm. As advanced oxidation prowise$ are evaluated M e r , it is possible that new Dzone contacting systems will emerge to take advantage of the inherent rapid mass nansfer and chemical reaction rates of radical processes. New designs that combine ozone generation with ozone, UV, and peroxide injection may emerge as the best commercial prospects for advanced oxidation processes in water and wastewater treatment. Referem ( I ) Rice, R. 0 . In Safe Drinking Hhrer: ?be Impact of Chem’cak on 4 limited Resource; Rice, R. G., Ed.; Lewis Publishers: 1985; pp. 123-59. (2) Prendivillc, I!W. Ozone Sci. Eng. 1986.8, 77-93. (3) Zoeteman, B.C. et id. Envimn. Health Pcrspect. 1982,46, 191-205.
-
CONTENTS
Photodi-iation oi NLmsoheme Complexes Charg%Transter states in Porphyrin Hmem dimers * Electron Transfer in Chlorophylls. Chlorins, and Pomhyrins * SpinQrbit and Spin-Polarization EWe~tsin Metalloporphyrins * NH-Tautomerism in the Formation of Excited States * Optical h t m i o n 01 the LBnthanOid Ion Contractin The S2 Emib sion of Metalloporphyrins * Triplet-Triplet Annihilation The Triplet-State Decay Rate Constants 01 Porphyrin Dimerization EWecIs on Porphyrins Distance Dependent Rates Picosemnd Excited State Relaxation Picosemnd Phmdi550Ciation 01 the CO and 0. Forms * Elmron Transter in Banerial Photosynthetic Reanion Centers * TWP Photon Absorption and RadiationleSS Trans!lions * Nickel Porphyrins and Nickel-Reconstiluted Heme Proteins Porphyrin Radical Cations. Excited States. and Ligation Photdynamics * Transient Photoinduced Ligation Changes Mechanistic Studies 01 Thermal and Photoinduced Atropisomeriration Quenching 01 Low-Lying Excited States in Porphyrins Photmxidation of Phthab cyanines Cation Radical Formation -The Principal Tumor-LocalizingPorphyrin PhotO sensitizer
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asvslopedhDmamnfersnceheMin Urns R a k , Arkansas. NovemhK 1 5 1 9 . 1985
ACS Symposium Series NO 321 384pages(t988)Clothbound
LC 8614647 ISBN 0841209974
US 6 Canada SU.95 Expon $77.05
(4)
Caste.
C.; Fiessinger, E In AWWA Proceedmgs, Ozonation: Reccnr Advances and Research Needs: American Wale1 Works Association: Denver, in press.
(5) Staehclin, 1.; Hoignl, 1. Envimn. Sci. Technoi. 1982.16, 6 7 6 8 1 . (6) Sproul, 0.1. In A W A Proceedings. Ozonotion: Recent Advonccs ond Research Needs: American Water Works Association:
Denver. in press. (1) Monk, R.D.G.et al. 1. Am. Hhrer W a h Assoc. 1985, 77.49-54. (8) Reckow. D.A. In AWWA Proceedings. Ozonanon: Recent Advance3 ond Research Needs: American Water Works Associalion: Denver. in press. (9) Hoignl.1.; Bader, H. HhrerRes. 1981,17, I71-W .
.
sui
(17) 196
‘lib( (19)
250 Envimn. %I.Tahnd.. W. 21. No.3 . m
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(10) Hoignb, 1.; B&x, H. Hhter Res. 1981, 17. IRS-94. . ., . .. . .. (11) Rice, R. 0. InAWAPmceedings, Oronation: Recent Advances ond Research Needs; American Wale1 Works Association: Denver. 1” press. (12) Staehelin. 1.; Hoignl, 1. Envimn. Sci. Technoi. 19&?,16, 11-22. (13) Buhler, R.E.; Suchclin, 1.; Hoign.4, 1. 1. Phys. Chen 1984,88,2560-64. (14) Staehclin, 1.; Buhler, R. E.; Hoignl. 1. 1. Phys. Chcm 1984,88,5999-6004. (15) Forni, L.; Bahnemann, D.; Hart, E. 1. 1. Phys. Chcm. 1982.86.255-59. (16) Taube.
(20) Bailey. P: S. In Ozomtion in Organic Chemistry, Vol. 1. OlefinicCompounds; Academic Press: New York. 1918; pp. 15-31. (21) Bailey. I! S. In Ozonation in 0rgm.c Chemistry, Val. If, Nonolcfinic Compounds; Academic Press: New York. 1982; pp. 1842; 311422. (22) Garrison. R. L.; Mauk. C. E Prengle, H. W.. Ir. In Fin1 lnternationnl syntposim on Ozone for Water and Wutewater %otment: Rice, G . G.;Browning. M. E., Fds.; International Ozone Association: Vienna, Va.. 1975; pp. 551-71. (23) Peyton, 0 .R. et al. Environ. Sci. Pchnot. 1982, 16.448-53. (24) Glaze. W. H. etal. Envimn. Sei. Tcehno. 19Q16.454 58. (25) Peyton, 0 . R.; G l w , W. H. In Photochemistry of Environmental Aquatic Syst e m : Zika. R. G . ; Coopcr, W. I., Eds.; ACS Symposium Series 327; American Chemical SocieIy: Washington. D.C.. 1986; pp. 7 6 QQ
I”.
(26)-Sierka, R. A.; Amy, 0. L. Ozone Sci. Eng. 1985, 7.41-62. (27) Nakayama. S. et al. Ozone Sci’. Eng. lm, I , 119-31. (28) Duguct. 1. I!et nl. Ozone Sei. Eng. 1995, 7. 241.58. (29) Chen. 1. W. et al. AlChE Snw. Ser ’ l h7,73; 206. (30) Brunet. R.; Earbigot. M. M.; Dorc, M. Ozone Sei. Eng. 1984.6, 163-83. (31) Glaze. W. H. et al. “Pilot Scale Evduat h of kotalvtic Ozonntion for Trihalomethane Prccukor Removal.“ Repon of Coopralive Agreement CR-808825. EPA-6001 52-R4-136. NTlS PBR4-234517. Munieioal
.~
~
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Cincinnati, 1984. (32) Taube, H. Tram. Faraday Soc. 1957.53, 656. (33) Glaze, W. H. Environ. Heolth Perspect. 1986.69, 151-57. (34)Sonlheimer. H. 7Pmkzrionr of Rcporrs on Special Problem
of Hhrcr 7Peamnr-
Vol. 9, Adsorption, EPAMX)19-16430; Municioal Environmental Research Lahratorv. EPA: Cincinnati, 1975. (35) Eberhardl. M. N.; Madscn, S.; Sontheimcr, H. “Untersuchungen zur Vtwcndung Biologisch Arbeitender Aktivkohlcfilter bei der ~inkwaswraufbereilender,”Report 7. Engler-Buntc-lnstitut. Karlrruhe Unirerwl) Karlsruhc, West Germany. 1914 (361 Rice. R ti et al ‘‘RtnInetcal Proccswo ’ in the iteatmen1 of Municifal Water Sup plies,” EPA-600/2-8@1980 Municipal Environmental Research Laboratory. EPA: Cincinnati. 1980. (37) Glaze. W. H.: Wallace. 1. L. J. Am. Hhrer Work Assoc. 1984, 76.68-75. (38) Maloney. S. W. et al. J. Am. Water W a h Arsor 1985. 77.. 66-13. (39)DiGiano. E In A h A Proceedings. Ozonotion: Recent Adwnces and Research Needs; American Water Works Association: Denver. in press. ~~
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Wimbnr H. Glcru is professor of public health and director of the Environmental Science and Engineering Program at UCIA. H e is a principal investigator for projects concerning catalytic ozomion w r e r trearment processes, among other areas.
