Environ. Sci. Technol. 1989, 23, 744-745
COMMUNICATIONS Inactivatlon of Giardia muris and Indlcator Organisms Seeded in Surface Water Supplies by PEROXONE and Ozone Roy
L. Woife,' Mic H. Stewart, Karen N. Scott, and Michael J. McGuire
Metropolitan Water District of Southern California, 700 Moreno Avenue, La Verne, California 91750 Introduction Recent research has shown that PEROXONE, an advanced oxidation process generated by combining ozone and hydrogen peroxide, is superior to ozone for removal of some recalcitrant taste and odor compounds and groundwater contaminants (1). The PEROXONE process promotes the formation of a high-energy, short-lived OH' radical in water by accelerating the decomposition of ozone by hydrogen peroxide (2). One important area of research that needs to be investigated is the disinfection effectiveness of PEROXONE. Previous research at Metropolitan has indicated that the microbicidal effectiveness of PEROXONE against indicator organisms depended on the applied ozone dosage, H202/03ratio, contact time, and source-water quality (3). The results of Metroplitan's earlier work suggested that the optimal ratio for disinfection was 50.3. The present study was undertaken to further optimize the PEROXONE process for disinfection by altering H,02/03 ratios and contact time. The effectiveness of PEROXONE and ozone against Giardia muris cysts was also tested. To date, we are unaware of any pilot plant data on the inactivation of Giardia in raw water by PEROXONE and ozone. Materials and Methods Microorganisms were seeded into the predisinfection contactor influent of a 6 gal/min pilot plant and exposed to three applied ozone dosages (1.0, 2.0, and 4.0 mg/L), five H202/03ratios (0, 0.05, 0.1, 0.2, and 0.31, and three contact times (6,9, and 12 min) in California State project water (SPW). Details of the pilot plant are described elsewhere (3). The mean and range values for SPW water quality characteristics during the study were as follows: turbidity, 1.4 and 0.75-1.8 nephelometric turbidity units (NTU); temperature, 18.4 and 13-22 OC; total organic carbon, 2.48 and 2.18-2.70 mg/L; alkalinity, 82 and 80-83 mg/L; and pH, 7.97 and 7.85-8.07. The protocol for preparation and recovery of the microorganisms has also been described elsewhere (3, 4 ) . Ozone residuals were measured spectrophotometrically with indigo trisulfonate reagent (5). Hydrogen peroxide was analyzed according to the fluorescence derivatization procedure of Kok et al. (6). Samples were collected in sterile bottles containing sodium thiosulfate and catalase for neutralizing ozone and hydrogen peroxide residuals, respectively. The viability of the Giardia cysts was determined by the in vitro excystation method of Schaefer et al. (7). Results and Discussion Results of the experiments showed that the indicator organisms, with the exception of the heterotrophic plate count (HPC) group, were highly sensitive to both PER744
Environ. Sci. Technol., Vol. 23, No. 6, 1989
OXONE and ozone. At a 1.0 mg/L applied ozone dosage, >5 log,, of Escherichia coli and >6 log,, of both coliphages were inactivated after 12 min of contact time at H202/03 ratios ranging from 0 to 0.3 (Table I). Under the same conditions, only approximately 2 log,, of HPC bacteria were inactivated, corresponding to HPC levels ranging from 40 to 80 colony-forming units per milliliter (CFU/ mL) in the contactor effluent. Decreasing the contact time from 12 to 6 min reduced the amount of G. muris inactivation (Figure 1) but had little or no impact on the bacterial and viral indicators (data not shown). A t an applied ozone dose of 1.0 mg/L, PEROXONE (0.2 ratio of Hz02/03)and ozone required 9 and 8 min of contact time, respectively, to achieve 99% inactivation of G. muris cysts (Figure 1). The CT values [i.e., disinfectant concentration (in milligrams per liter) X contact time (in minutes)] for the inactivation of G. muris were generated by several methods of calculation in anticipation of the proposed Surface Water Treatment Rule (SWTR) (8). The contact times used for calculating CT values were based on 10% and 50% breakthrough of tracer compounds in the contactors, and the ozone concentrations used were based on the ozone residual and half of the residual and dose. These calculations are summarized in Table A (supplementary material). Figure A (supplementary material) illustrates the comparative inactivation of G. muris by ozone and PEROXONE (H202/03ratio, 0.2) based on the CTs from Table A. Table I1 summarizes the CT values generated in this study for 90% and 99% inactivation of G. muris by PEROXONE and ozone by using the 50% breakthrough times. CT values based on the 10% breakthrough times were not generated because the breakthrough times were identical for all the contact times tested (Table A). The U.S. EPA's CT values for the inactivation of Giardia lamblia are also presented for comparison. The CTg9 values for ozone were 1.0-1.4 times greater than for PEROXONE, depending on the method of CT calculation used. This suggests that PEROXONE is comparable to-or slightly more potent than-ozone when CTs are based on ozone residuals. However, because ozone decomposes more rapidly in the presence of hydrogen peroxide, higher ozone dosages may be necessary with PEROXONE to achieve residuals comparable to those achieved with ozone alone. Also, the use of ozone residuals to calculate CT values for PEROXONE may not take into account other oxidizing species that may have disinfectant activity. The CT,, values generated in this study for G. muris (3.4-5.4 mg.min/L) were 2.6-4.2 times higher than the U.S. EPAs values for G. Eamblia (1.3 mg.min/L at 15 "C). This difference is probably a result of the greater resistance of G. murk cysts to disinfection. Wickrama-
0013-936X/89/0923-0744$01.50/0
0 1989 American Chemical Society
Table I. Effects of Ozone Dose and Ratio of Hydrogen Peroxide to Ozone on the Inactivation of Indicator Microorganisms in SPW by PEROXONE and Ozonea
dose, mg/L HzOz OS 0 0.05 0.10 0.20 0.30 0 0.10 0.20 0.30 0.60 0 0.20 0.40 0.80 1.20
ratio
1.0 1.0 1.0 1.0 1.0 2.0 2.0 2.0 2.0 2.0 4.0 4.0 4.0 4.0 4.0
loglo inactivation f 1 SDb
O3 residual, mg/L
H202/03
0.24 0.18 0.23 0.10 8.1 >8.0 8.0 7.8 f 0.1 7.9. f 0.1
7.3 f 0.5 7.3 f 0.5 6.7 f 0.3 7.2 f 0.4 >7.9 7.2 f 0.7 7.5 f 0.2 7.3 f 0.3 7.5 f 0.3 6.8 f 0.7 >7.9 >7.9 >7.9 7.8 f 0.3 7.9 f 0.2
"Theoretical contact time, 12 min. *Inactivation = log,, mean influent - log,, mean effluent
kill, %
ozone PEROXONE' ozone PEROXONE
90 90 99 99
calcd CTs, mg/L-min C1T2" CZTz0 US. EPA CTsb 1.6 1.2 3.4 2.6
2.8 2.6 5.4 5.2
0.4 1.3
a C1, ozone residual; Cz, (ozone dose + ozone residual)/2; TI and Tz, time (in minutes) to reach 10% and 50% breakthrough, respectively. Results at 14 "C. *CT value obtained from U S . EPA euidance manual. 15 O C . H,Oo/Oz ratio, 0.2.
WATER TEMPERATURE
-
2.1 2.0 2.3 2.0 2.2 2.3 3.0 3.0 2.6 2.7 3.7 3.2 3.3 2.9 2.9
f 0.1 f 0.1 f 0.1 f 0.1 f 0.1 f 0.3 f 0.1 f 0.1 f 0.1 f 0.1 f 0.1 f 0.1 f 0.1 f 0.2 f 0.1
deviation.
ozone for the disinfection of indicator organisms and G. muris cysts.
Table 11. Calculated CT Values for the Inactivation of G . muris by PEROXONE and Ozone
disinfectant
f 1standard
R2A-HPC
14'C
-
-. HYOROGEN PEROXIOE/OZONE APPLIEO DOSAGES [Mp/L)
0.2/1.0
Acknowledgments We would like to acknowledge the assistance of numerous Metropolitan staff members, including s. Liang, M. L. Lo, M. Simpson, G. Izaguirre, R. F. La Londe, and M. R. Kimball.
Supplementary Material Available A table of CT values for G. muris inactivation by PEROXONE and ozone and a figure illustrating the comparative inactivation (2 pages) will appear following these pages in the microfilm edition of this volume of the journal. Photocopies of the supplementary material from this paper or microfiche (105 X 148 mm, 24X reduction, negatives) may be obtained from Microforms Office, American Chemical Society, 1155 16th St., N.W., Washington, DC 20036. Full bibliographic citation Cjournal, title of article, authors' names, inclusive pagination, volume number, and issue number) and prepayment, check or money order for $10.00 for photocopy ($12.00 foreign) or $10.00 for microfiche ($11.00 foreign), are required. Registry No. H202,7722-84-1.
Literature Cited
0.1
I 0
3
/ I I I I l g 6 THEORETICAL CONTACT TIME [nlnl
l
I
I 12
Flgure 1. Inactivation of 0 . muds seeded in California State project water by PEROXONE and ozone.
nayake et al. (9) showed that G. muris was 1.5-3.5 times more resistant to ozone than was G. lamblia. Metropolitan's C T g g values for G. muris inactivation were 1.8-22 times higher than those reported by Wickramanayake et al. (9).This difference probably results from water quality differences in the studies; Metroplitan's work was conducted in untreated surface water (pH 8, temperature 14 "C),whereas Wickramanayake's experiments were done in distilled water (pH 7, temperature 5 and 25 OC). Overall, the results of this study for the inactivation of Giardia in SPW by ozone are in reasonable agreement with the proposed values issued by the US.EPA for compliance with the SWTR. In addition, the study data suggest that PEROXONE (at a 0.2 ratio of H202/03)is comparable to
(1) McGuire, M. K.; Davis, M. K. Water Eng. Manage. 1988, 135,42-49. (2) Glaze, W. H.; Kang, J. W.; Chapin, D. H. Ozone: Sei. Eng. 1987,9, 335-352. (3) Wolfe, R. L.; Stewart, M. H.; Liang, S. L.; McGuire, M. J.,
submitted for publication in Appl. Environ. Microbiol. (4) Scott, K. N.; Wolfe, R. L.; Stewart, M. H.; McGuire, M. J.,
in preparation. (5) Bader, H.; Hoign6, J. Ozone: Sei. Eng. 1982, 14, 169-176. (6) Kok, G. L.; Thompson, K.; Lazrus, A. L.; McLaren, S. E. Anal. Chem. 1986,58, 1192-1194. (7) Schaefer, F. W., 111;Rice, E. W.; Hoff, J. C. Trans. R. SOC. Trop. Med. Hyg. 1984, 78, 795-799.
(8) US.Environmental Protection Agency. Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water S y s t e m Using Surface Water Sources; USEPA Washington, DC, October 1987; (draft; final in preparation). (9) Wickramanayake, G. B.; Rubin, A. J.; Sproul, 0. J. J.-Am. Water Works Assoc. 1985, 77, 74-77. Received for review February 16, 1989. Accepted April 4, 1989. This work was supported in part by the American Water Works Association Research Foundation. Environ. Sci. Technol., Vol. 23, No. 6 , 1989 745
