Removal of Aquatic Humus by Ozonation and Activated-Carbon

39 Downloaded by UCSF LIB CKM RSCS MGMT on September 4, 2014 | http://pubs.acs.org Publication Date: December 15, 1988 | doi: 10.1021/ba-1988-0219.ch039

Removal of Aquatic Humus by Ozonation and Activated-Carbon Adsorption 1

Ellen Kaastrup and Terje M . Halmo

2

Department of Civil Engineering, Norwegian Institute of Technology, N-7034 Trondheim-NTH, Norway

The separate and combined effects of treatment with ozone and activated carbon were studied for three different humus sources: Norwegian brook water, Norwegian bog water, and commercial humic acid. The effect of ozonation on solution properties was determined by ultrafiltration, color, UV, and dissolved organic carbon (DOC) analysis. Adsorption prior to and after ozonation was studied in laboratory isotherm studies and a pilot-scale column experiment. Ozonation caused significant reductions in the content of high-molecular-weight material, UV extinction, and color; DOC reductions were insignificant for ≤1 mg of ozone per mg of DOC. Both isotherm and pilot-scale studies showed significant increases in adsorption capacities resulting from preozonation.

SURFACE WATERS HIGH IN COLORM I- PARTN IG HUMC I SUBSTANCES are com monly used for drinking water in Norway. Such water used to be considered harmless, and the brownish color was treated as an aesthetic nuisance. The discovery of possible health threats caused by formation of trihalomethanes (THM) and heavy metal complexes (1) has led to more restrictive treatment requirements and extensive research on treatment alternatives. 1Current address: Ebasco Services, Inc., 143 Union Boulevard, Lakewood, CO 80228 Current address: Elf-Aquitaine Norway A/S, P.O. Box 168, Dusavik, N-4001 Stavanger, Norway

2

0065-2393/89/0219-0697$08.50/0 © 1989 American Chemical Society

In Aquatic Humic Substances; Suffet, I., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1988.

698

AQUATIC H U M I C SUBSTANCES

It is difficult to find suitable treatment methods because of the wide variety of compounds in such water. The treatment combination investigated in this study was ozonation and activated-carbon adsorption. Neither of these methods has been successful in efficient removal of humic materials when used alone. The study objectives were to

Downloaded by UCSF LIB CKM RSCS MGMT on September 4, 2014 | http://pubs.acs.org Publication Date: December 15, 1988 | doi: 10.1021/ba-1988-0219.ch039

• study the adsorption of organic matter from different humicwater sources onto activated carbon, • determine how ozonation affects solution properties such as molecular-size distribution, color, U V extinction, and dissolved organic carbon (DOC), • determine i f the adsorbability of organic matter is increased (or changed) as a result of preozonation, and • relate the changes i n adsorptive properties to the changes in solution properties.

Background Humic Substances in Water. Humic substances in water are gen erally divided into humic acids and fulvic acids. The humic acid fraction, containing the larger base-soluble molecules, precipitates on acidification to p H 50,000 10,000-50,000 1,000-10,000 ο

Ο

C/5

η m

Ζ

η Figure 3. UV isotherms for Hellerudmyra water. Key: Ο , so/id line, nonozonated (A = 59.6 m' ); T , dashed CO line, 0.5 mg of 0 per milligram of DOC (A = 39.9 m~ ); V, dotted line, 1.0 mg of 0 per milligram of DOCG ce (Ao = 29.3 m- ).

3



39.

KAASTRUP & H A L M O

Ozonation and Activated-Carbon Adsorption 711

C

e

(mg DOC/I)

Figure 4. DOC isotherms for Heimdalsmyra water with high initial DOC. Initial concentrations and Freundlich parameters are given in Table V. Key: O, solid line, nonozonated; V , dashed line, 1.0 mg of 0 per milligram of DOC; Ύ, dotted line, 2.0 mg of 0 per milligram of DOC. 3

3

dose of 1.0 mg of ozone per milligram of D O C applied to Hellerudmyra water, resulting in a significantly higher K value and a lower 1/n value. Figure 8 shows D O C isotherms for a lower initial concentration of commercial humic acid, approximately 5 m g / L , ozonated with 0, 0.5, and 1.0 mg of ozone per milligram of D O C . The trend of increased adsorbability is the same as for the higher initial concentration. Results from microcolumn studies for commercial humic acid, 2.5 g of carbon, and ozone doses of 0 and 1.0 mg per milligram of D O C are shown in Figures 9 and 10, represented by D O C and U V extinction breakthrough profiles, respectively. The initial concentrations for the microcolumn ex periments, indicated in the figures, were constant throughout the experi ment. The breakthrough curves for nonozonated water show immediate breakthrough of D O C as well as UV-absorbing compounds. This break through indicates low adsorption capacity and slow adsorption kinetics. A significant increase in removal efficiency was obtained as a result of preo zonation. F



712


Figure 5. UV isotherms corresponding to the data in Figure 4. Key: O , solid line, nonozonated (A = 77.5 m ); V , dashed line, l.Omgof 0 per milligram of DOC (A = 41.4 m- ). -1

0

3

1

0

Breakthrough curves for Hellerudmyra water for columns with 1 g of carbon are plotted in Figures 11-13 for D O C , U V extinction, and color. The curves for ozonated and nonozonated water exhibit steep concentration increases from the beginning of the experiments, whereafter both curves reach plateau concentrations. The removal efficiency was, however, signif icantly higher for ozonated than for nonozonated water. Results from the pilot-scale column study carried out with Heimdals myra water are presented in Figures 14-22. Figures 14-16 show influent concentration profiles and breakthrough curves for the upper sampling point with respect to color, U V extinction, and D O C . Corresponding data for the middle and effluent sampling points are shown in Figures 17-19 and 20-22, respectively. The D O C influent curves in Figure 14 show that the influent value for ozonated water is only slightly lower than that for nonozonated water during the first 3 weeks of the experiment; the difference corresponds to that ob served in the isotherm experiments. After this time the influent concentra tion for ozonated water drops significantly. This drop was assumed to be a


39.




Ο

Ο

5 C

10 e

15

(mg DOC/I)

Figure 6. DOC isotherms for commercial humic acid. Corresponding initial concentrations and Freundlich parameters are given in Table V. Key: O , solid line, nonozonated; dashed line, 0.5 mg of 0 per milligram of DOC; O, dotted line, 1.0 mg of 0 per milligram of DOC. 3

3

result of biological growth that was observed in the tubing system at this time. The influent concentration decrease is not observed for the U V and color parameters. This distinction suggests that only compounds that are not detected by these analyses are degraded biologically. The effluent profile for nonozonated water shows a significant, imme diate concentration increase in all three parameters. This increase demon strates that the UV-absorbing, color-imparting compounds are responsible for the early D O C breakthrough. A significantly better D O C removal is observed for ozonated water with a much lower content of large colorimparting molecules. Ozonation reduced the U V extinction and color by approximately 40 and 60%, respectively. The curves in Figures 17-19 show that higher adsorption capacities are obtained for the 60-cm sampling point as a result of longer contact times, but again a more rapid and sharper breakthrough is observed for nonozonated water.


714



•

25

50

75

100

125

1

UV ext. (m" ) Figure 7. UV isotherms for commercial humic acid. Key: O, solid line, nonozonated (A = 117.9 m' ); • , dashed line, 0.5 mg of DOC; O, dotted line, 1.0 mg of0 per milligram of DOC (A = 87.6/90.1 m~ ). 1

0

l

3

Humus Source Commercial humic acid Hellerudmyra humus water

Table V. Applied Ozone (mg/mg of DOC) 0 0.5 1.0 0 0.5 1.0 2.0

Heimdalsmyra humus water

0 1.0 2.0

0

Freundlich Parameters Nonadsorbent Initial DOC DOC (mg/L) (mg/L) 14.20 0 0.19 0 0.48 13.69-13.09 0 0.57 13.29-13.77 0 5.43 13.80 12.89-13.04 0 14.72 24.66 0.70 12.37 0 15.70 81.33 0.75 9.09-9.60 0 7.29 8.48 0.50 0 9.35 15.81 14.01 0 18.65 15.19 0 13.05

J/n 1.93 1.71 1.97 1.02 0.69 0.42 0.88 0.43 1.20 1.00 0.61 0.52 0.57


2

r 0.85 0.84 0.92 0.94 0.96 0.96 0.85 0.90 0.85 0.81 0.95 0.96 0.96


39.


0


1

2

3

4

C ( m g DOC/I) e

Figure 8. DOC isotherms for commercial humic acid. Key: O, solid line, nonozonated; T , dashed line, 0.5 mg of 0 per milligram of DOC; V , dotted line, 1.0 mg of 0 per milligram of DOC. 3

3

The effluent curves in Figures 20-22 show less pronounced differences between the D O C curves for ozonated and nonozonated water because the carbon is farther from saturation. The U V and color curves do, however, demonstrate why adsorption alone does not give satisfactory treatment re sults. Even though the D O C values are low, a color breakthrough to un acceptable levels is observed in nonozonated water after a few days. No significant difference was observed between D O C removal in the slow sand filter and the rapid sand filter. Such a difference would indicate biological removal in the slow sand filter.



716


4.0

1.0 2.0 3.0 Throughput volume (I)

Figure 9. DOC breakthrough curves for nonozonated and ozonated solutions of commercial humic acid. Key: O, solid line, nonozonated effluent; solid line, nonozonated influent; • , dotted line, ozonated effluent (1.0 mg of 0 per milligram of DOC); dotted line, ozonated influent. Carbon: 2.50 g (48-65 Tyler mesh), column diameter: 1.0 cm, empty-bed contact time: 0.80 min. 3

100 h 80

h

1.0

2.0

3.0

4.0

Throughput volume (I)

Figure 10. UV breakthrough curves for experiments in Figure 9. Key: O, solid line, nonozonated effluent; solid line, nonozonated influent; dotted line, ozonated effluent (1.0 mg of 0 per milligram of DOC); dotted line, ozonated influent. 3


39.



_

14

_

12 \

m 10 Β

Ο


Ο Q

c/c

c

1.0

8

-

6

-

- 0.8 V"""** fl

r

4

g β 0

0.6

ν*—

(m

0.4

—

— I 0.2

I

ι

ι

ι

0.5

1.0

1.5

2.0

Throughput volume (I)

Figure 11. DOC breakthrough curves for Hellerudmyra water. Key: Ο , solid line, nonozonated effluent; · , CIC ; solidline, nonozonated influent; V , dotted line, ozonated effluent (1.0 mg of 0 per milligram of DOC); • , C/C ; dotted line, ozonated influent. Carbon: 1.00 g (48-65 Tyler mesh), column diameter: 10 mLlmin, empty-bed contact time: 0.22 min. 0

3

0

60 50

h

40

b_

" x

30

h

>

20

?

Ε r

Φ

10 0.5

1.0 Throughput

1.5

2.0

volume (I)

Figure 12. UV breakthrough curves corresponding to results in Figure 11. Key: O, solid line, nonozonated effluent; solid line, nonozonated influent; •, dashed line, ozonated effluent (0.5 mg of 0 per milligram of DOC); dashed line, ozonated influent; V , dotted line, ozonated effluent (1.0 mg of 0 per milligram of DOC); dotted line, ozonated influent. 3

3



718


Throughput volume 111

Figure 13. Color breakthrough curves corresponding to results in Figures 11 and 12. Key: O, solid line, nonozonated effluent; solid line, nonozonated influent; • , dashed line, ozonated effluent (0.5 mg of 0 per milligram of DOC); dashed line, ozonated influent; V , dotted line, ozonated effluent (1.0 mg of 0 per milligram of DOC); dotted line, ozonated influent. 3

3

6.0

0.0

10.0

20.0

30.0 Time

40.0

50.0

60.0

70.0

80.0

(days)

Figure 14. DOC concentration profiles for influent and 30-cm sampling point. Key: Dashed line, nonozonated influent; dot-dashed line, ozonated influent; •, nonozonated breakthrough profile; O, ozonated breakthrough profile.


39.



25.0

20.0 .

H

15.0

Β

Β

/

\

'^-.^ /

\


10.0

5.0

.

0.0 0.0

10.0

20.0

30.0 40.0 50.0 TLme (days)

1 . . . .

60.0

1

..... i .

70.0

80.0

Figure 15. IN profiles for influent and 30-cm sampling point. Key: Dashed line nonozonated influent; dot-dashed line, ozonated influent; •, nonozonated breakthrough profile; O, ozonated breakthrough profile. y

Discussion Of the three humus sources investigated, only the two natural sources can be considered representative of the humic-substance problems confronted in drinking-water treatment. The commercial humic acid did, however, serve as an interesting comparison because of its large fraction of high-molecular-

0.0 0.0

10.0

20.0

30.0 40.0 50.0 TLme (days)

60.0

70.0

80.0

Figure 16. Color profiles for influent and 30-cm sampling point. Key: dashed line, nonozonated influent; dot-dashed line, ozonated influent; •, nonozonated breakthrough profile; O, ozonated breakthrough profile.



720


weight compounds. The different character of the commercial humic acid was reflected in a significantly higher spectral absorption coefficient. Table III shows significantly lower percentage reductions in U V ex tinction for commercial humic acid than for the other humus sources. These results, combined with the molecular-size distributions in Table IV, indicate that significant amounts of easily oxidized high-molecular-weight material are still left after application of 1 mg of ozone per milligram of D O C to commercial humic acid. Most of the high-molecular-weight material in H e l lerudmyra water has been oxidized at this ozone dose. A significant drop in D O C value was observed for Hellerudmyra water after complete decolori zation at an ozone dose of 2 mg per milligram of D O C . This drop indicates that the large color-imparting molecules are most easily oxidized and that further oxidation of the smaller molecules does not take place until all the large molecules are degraded. The isotherm studies leave no doubt that preozonation with ozone doses normally used in drinking-water treatment enhances the adsorbability of organic matter from highly colored humic water. The results indicate that the optimal ozone dose depends on the initial spectral absorption coefficient 6.0

0.0

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

Time (days) Figure 17. DOC concentration profiles for 60-cm sampling point. Key: •, nonozonated breakthrough profile; O , ozonated breakthrough profile. and molecular-weight distribution; higher doses can be applied to solutions with higher coefficients and higher fractions of large molecules. A n ozone dose of 2 mg per milligram of D O C had an adverse effect on the adsorption of organic matter from Hellerudmyra water. This effect, which indicates that an optimal dose of ozone is approximately 1 mg per milligram of D O C , can be explained by complete removal of large molecules and further ozonation of the products to polar, less-adsorbable compounds. For


39.

KAASTRUP & HALMO

Ozonation and Activated-Carbon Adsorption

721

25.0 r-

20.0 -


Ε

Time (days) Figure 18. UV profiles for 60-cm sampling point. Key: •, nonozonated break through profile; O , ozonated breakthrough profile.

60.0

:

50.0 \

a_

:

40.0 -

0.0 ' , , , , ι 0.0 10.0 20.0

ι . • , . t

30.0

40.0

50.0

60.0

ι , ... ι ... • I 70.0 80.0

Time (days) Figure 19. Color profiles for 60-cm sampling point. Key: •, nonozonated break through profile; O , ozonated breakthrough profile.

Heimdalsmyra water, the difference between isotherms for ozone doses of 1 and 2 mg per milligram of D O C were insignificant. In this case there was no significant decrease in D O C value for the higher dose. The large improvement in adsorbability for commercial humic acid that results from an increase in the ozone dose from 0.5 to 1.0 mg per milligram of D O C indicates that even higher doses would benefit the adsorption. A relatively strong color indicated that a significant amount of color-imparting


722

AQUATIC HUMIC SUBSTANCES 6.0

5.0 4

ζ ·°


CD 3

3.0 h

0.0 0.0

10.0

20.0

30.0 Time

40.0

50.0

60.0

70.0

80.0

(days)

Figure 20. DOC concentration profiles for effluent. Key: •, nonozonated ef fluent; O , ozonated effluent.

25.0

20.0

ε 15.0

Φ

10.0

i

5.0

c:

0.0

10.0

20.0

30.0 40.0 50.0 TLme (days)

60.0

70.0

80.0

Figure 21. UV profiles for effluent. Key: •, nonozonated effluent; O , ozonated effluent.

substances was still left in the solution after application of the ozone dose of 1.0 mg per milligram of D O C . A n adverse effect of increased polarity would not be expected until the color-imparting substances had been oxi dized. The agreement between experimental data and the Freundlich param eters in Table IV for Hellerudmyra water was good, even though the data corresponding to ozone doses of 0.5 and 1.0 indicate the presence of non-


39.

KAASTRUP & HALMO

60.0

50.0 "

\

: 7


723

:

40.0

:

CD —

Adsorption

:

—

CL_

Ozonation and Activated-Carbon

30.0

1

0.0

10.0

20.0

30.0

40.0

Time

50.0

60.0

70.0

80.0

(days)

Figure 22. Color profiles for effluent. Key:U

Y

nonozonated effluent; O , ozonated

effluent.

adsorbable organic matter. The modified model gave a better fit in the case of an ozone dose of 1, with a significantly higher K value and a lower 1/n value. Good agreement between experimental data and the Freundlich model was obtained for Heimdalsmyra water. For commercial humic acid, the model gives a good fit to experimental data at lower concentrations, but the estimated adsorption capacities are too low at higher concentrations. F

Pilot-Scale Study. The results from the pilot-scale study confirm the trend of increased adsorbability of organic substances as a result of preozonation observed in the laboratory studies. The importance of the contact time is clearly illustrated by the differences among color retentions at the different sampling points. The color-imparting substances that cause the immediate breakthrough at the top of the column are adsorbed when the contact time becomes sufficiently long. The effluent color values were, however, too high after a few days to meet drinking-water standards when activated carbon was used as the only treatment. Biological Activity in Pilot Plant. The pilot-scale study leaves no doubt that the major improvement in removal efficiency resulting from ozon ation is caused by enhancement of adsorptive properties. Some biological growth in the system handling ozonated water was observed, whereas none was observed in the other system. The improvement of adsorption capacity and rate is illustrated by the initial concentration profiles. No biological activity was detected until 3 weeks after startup. The drop in D O C concen tration after this time, with no corresponding drop in U V extinction or color, shows that the microorganisms preferentially take care of the oxidation prod-



724

AQUATO HUMIC SUBSTANCES

ucts that are not detected by U V or color measurements. The color-imparting substances must therefore be eliminated by adsorptive removal. Filter systems where biological activity occur are often characterized as biological filters. In this study, the biological activity did not seem to take place in the carbon filter, but rather in the system ahead of the filter. Because sand filters have been shown to be comparable to carbon filters in biological removal efficiency (25), a slow sand filter was used in this study to simulate biological removal in the carbon filter. Comparison with the rapid sand filter indicated that the sand filter did not give significant additional removal of organic matter and that the slight removal observed was caused by filtration rather than biodégradation. Flowing water is a good medium for biological activity if the nutrient requirements are satisfied, and it is likely that the biological activity often occurs in the tubing system between different process units. Biological re moval in the carbon beds may, however, be more important in systems treating water with a higher fraction of easily biodegradable matter. The reason why biological activity seemed to be limited to the tubing system in this study is probably that only a minor fraction of the organic matter was biodegradable. By assuming that the nutrient requirements were satisfied, the biodegradable fraction was estimated to be approximately 10%, on the basis of the D O C data for the last part of the study and the results discussed. The pilot study showed that ozonation of humic substances prior to activated-carbon adsorption is advantageous not only because of improved adsorption capacity and adsorption rate, but also because of formation of biodegradable organic matter. Comparison of Results. The results for all humic substances stud ied agree with the hypothesis of increased adsorbability resulting from preozonation. The ozone dose that can be applied without adverse effects on adsorption seems to be strongly dependent on the c o l o r / D O C ratio and spectral absorption coefficients; the higher these values, the more ozone can be applied. These observations confirm the composition-dependence of ozonation that formed the basis for this study. High color values correspond to large fractions of molecules with very high molecular weights. High doses of ozone have to be applied before these molecules are broken up into smaller units for which more of the activatedcarbon surface is accessible. The results indicate that the water has to be completely decolorized before the lower fractions are degraded to small, polar, poorly adsorbable molecules. This finding is in agreement with a very high reactivity toward ozone for the color-imparting conjugated chains in the very large molecules. The high reactivity makes this the dominating reaction as long as such material is present. In most of the ozonation adsorption studies reported earlier, the ad sorption of organic substances onto activated carbon was adversely affected by preozonation. The positive effect of preozonation observed in this study In Aquatic Humic Substances; Suffet, I., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1988.


39.

KAASTRUP & HALMO


does not contradict the results from previous studies. The explanation for this difference lies in the character of the solution. Several of the previous studies have been performed with water containing relatively small and easily adsorbable organic molecules. Ozonation of such water is likely to reduce the adsorbability because of increased hydrophilicity and polarity of the organic substances. The compounds studied here were large, poorly ad sorbable humic compounds that utilized only a small fraction of the adsorp tion area prior to ozonation. F o r such compounds the size and structural limitations hindering adsorption are reduced by ozonation; consequently, their adsorbability is increased. The results illustrate the importance of de termining the character of the organic substances present in the water before deciding on treatment schemes.

Conclusions Ozonation of water with a high content of color-imparting humic substances resulted in significant reductions in the content of high-molecular-weight material, color, and U V absorption. However, the organic-matter content (DOC) was almost unaffected by ozone doses normally used in drinkingwater treatment. Preozonation increased the adsorption of organic matter from the three humic solutions studied here. A n ozone dose of 1 mg per milligram of D O C seemed optimal for adsorption of organic matter from the two natural so lutions. In both cases, the adsorption capacities were reduced by application of 2 mg of ozone per milligram of D O C . The adsorption results for the commercial humic acid combined with a higher fraction of the very large molecules and higher spectral absorption coefficients indicate that the op timal ozone dose for commercial humic acid is higher than 1 mg per milligram of D O C . Pilot-scale studies of Heimdalsmyra water confirmed the increased ad sorbability that was observed in the laboratory studies. In addition, biological growth was observed in the system treating ozonated water. The biode gradable fraction of organic matter was estimated to be approximately 10% at the applied ozone dose of 1 mg per milligram of D O C . The major biological activity seemed to take place in the tubing system ahead of the carbon filters.

Acknowledgments Several people contributed help and stimulation during the course of this study. The authors thank Paul V. Roberts, whose advice has been of great importance for this work. Special thanks also go to Egil T. Gjessing for many helpful discussions on humic substances and to R. Scott Summers and Helge Brattebo for inspiring discussions on adsorption matters. The funds for this study were provided in part by N T N F (The Royal Norwegian Council for Scientific and Industrial Research), S I N T E F (the In Aquatic Humic Substances; Suffet, I., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1988.

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AQUATIC HUMIC SUBSTANCES

Foundation for Scientific and Industrial Research), and N T H (the Norwegian Institute of Technology).


References 1. Christman, R. F.; Gjessing, Ε. T. In Aquatic and Terrestrial Humic Materials; Christman, R. F.; Gjessing, E. T., Eds.; Ann Arbor Science: Ann Arbor, 1983; pp 517-528. 2. Gjessing, Ε. T. In Proc. Conjunc. 10th IAWPR Conf.; Edmonton, Alberta, June 1980; Smith, D.W.;Hrudey, E. W., Eds.; Pergamon: Oxford, England, 1981. 3. Thurman, E. M.; Wershaw, R. L.; Malcolm, R. L. Org. Geochem. 1982, 4, 27-35. 4. Malcolm, R. L.; MacCarthy, P. Environ. Sci. Technol. 1986, 20, 904-911. 5. McCreary, J. J.; Snoeyink, V. L. Water Res. 1980, 14, 151-160. 6. Lee, M. C.; Snoeyink, V. L. Humic Substances Removal by Activated Carbon; Water Resources Center, University of Illinois at Urbana-Champaign: Urbana, 1980. 7. Weber, W. J., Jr.; Pirbazari, M.; Herbert, M. D. Proc. Am. Water Works Assoc. Annu. Conf. 1978, 98, paper 15-1. 8. Weber, W. J.; Voice, T. C.; Jodellah, A. J. Am. Water Works Assoc. 1983, 75, 612. 9. Frick, B. R.; Bartz, R.; Sontheimer, H.; DiGiano, F. A Carbon Adsorption of Organics from the Aqueous Phase; Suffet, I. H.; McGuire, M. V., Eds.; Ann Arbor Science: Ann Arbor, 1982; Vol. 1Α, p 229. 10. Frick, B.R.;Sontheimer, H. Treatment of Water by Granular Activated Carbon; McGuire, M. V.; Suffet, I. H., Eds.; Advances in Chemistry 202; American Chemical Society: Washington, DC, 1983;p247. 11. Samdal, J. E. Vattenhygien 1966, 4, 161-165. 12. Meijers, A. P. Water Res. 1976, 11, 647-652. 13. Nebel, C. Public Works 1981, 112(6), 86-90. 14. Flogstad, H. Behandling av humus med ozon; SINTEF report STF21 A84037; Foundation for Scientific and Industrial Research: Trondheim, Norway, 1984. 15. Benedek, A. International Ozone Institute Symposium on Advanced Ozone Technology, Toronto, Ontario; International Ozone Institute: Ontario, 1977. 16. Kuhn, W.; Sontheimer, H.; Steiglitz, L.; Maier, D.; Kurz, R. J. Am. Water Works Assoc. 1978, 70, 326-331. 17. Lienhard, H.; Sontheimer, H. Ozone: Sci. Eng. 1979,1,61-72. 18. Hubele, C.; Sontheimer, H. Environmental Engineering, Proceedings of the 1984 Specialty Conference; Pirbazari, M.; Devinney, S., Eds.; American Society of Civil Engineers: New York, 1984; University of Southern California, Los Angeles, June 1984. 19. Summers, R. S. Ph.D. Dissertation, Stanford University, 1985. 20. Suzuki, M.; Kawazoe, K. Seisan Kenkyu 1974, 26, 383. 21. Altmann, R. S. Ph.D. Dissertation, Stanford University, 1984. 22. Standard Methods for the Examination of Water and Wastewater, 14th ed.; American Public Health Association: Washington, DC, 1975;p455. 23. Zepp, R. G.; Schlotzhauer, P. F. Chemosphere 1981, 10, 479-481. 24. Reinhard, M. Environ. Sci. Technol. 1984, 18, 410-415. 25. Maloney, S. W.; Bancroft, K.; Pipes, W. O.; Suffet, I. H. J. Environ. Eng. Div. (Am. Soc. Civ. Eng.) 1984, 110, 519-533. RECEIVED for review July 24, 1987. ACCEPTED for publication April 20, 1988.


Removal of Aquatic Humus by Ozonation and Activated-Carbon

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