Removal of Bromate and Perchlorate in Ozone/GAC Systems

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Serum Bottle Experiments Since the column filtration experiments are labor and time intensive, it is useful to set up batch biological experiments to test the dependence of bromate reduction on various parameters. 160 mL serum bottles, equipped with gas-tight butyl rubber stoppers, were used as the batch reactors. Each bottle contained 140 mL of aqueous medium, which was autoclaved after the bottles were capped. After the bottles were cooled, biomass from the BAG filters was added. The medium consisted of the following: CUW, 5 mg/L nitrate, 5 mg/L sulfate, 19 ug/L bromate, and 1 mM phosphate buffer. Biomass was taken from the BAG filter operated with an influent nitrate concentration of 5.0 mg/L in CUW, and 1 mL of this inoculum was spiked to each serum bottle. The serum bottle experiments were used to evaluate the effect of temperature (4 and 25 °C) on bromate reduction. MATERIALS USED FOR PERCHLORATE REDUCTION EXPERIMENTS Water Two types of water were used in this study - DDW and CUW. Typical properties of CUW are listed in Table 2.1. Reagents and Carbon The chemicals used included reagent grade sodium perchlorate (Sigma Chemical Co., St. Louis, MO) and sodium bromate (Aldrich Chemical Co., Inc., Milwaukee, WI). Other chemicals were of reagent grade quality or better. Where appropriate, the chemicals were dried overnight at 105 °C and stored in a desiccator. Norit RO 0.8 GAG, lot number 72303-5 (Norit Americas Inc., Atlanta, GA), was used in the BAG filters. This carbon is an extruded peat activated by steam. The 30x40 fraction of Calgon F-400 (Calgon Inc., Pittsburgh, PA), lot number 5925-LG, was used for some kinetic studies. The F-400 is made from bituminous coal. 30
METHODS UTILIZED FOR PERCHLORATE REDUCTION EXPERIMENTS Biologically Active Carbon Filters Four filters were constructed to evaluate perchlorate removal. Each filter contained fresh carbon. BAG was formed by extensively preloading the filters with effluent from the previously described bromate reducing filters. The influent was spiked with 50 ng/L perchlorate and 20 ug/L bromate. The columns were operated with a 25-minute EBCT for 600 bed volumes. At the end of the preloading period, approximately 60 percent of the influent DOC and 90 percent of the influent bromate were consistently being removed. Therefore, by the end of the preloading period, the filters were considered biologically active. Two parallel filtration experiments were set up, each with two columns in series, for a total of four filters. The filtration experiments were often run with two filters in series, so that two EBCTs could be evaluated simultaneously. Once the filters were rendered biologically active, the influent base water for one set of filters was switched from bromate filter effluent to DDW. This allowed for better control over influent composition. The other set of filters utilized CUW as the base water for approximately one year. However, since perchlorate removal was not consistent in these filters due to the occurrence of nitrification, the data from these filters are not reported here. The schematic for the biological bromate filters shown in Figure 2.3 also serves as the schematic for the biological perchlorate filters. Syringe pumps (kd Scientific, Boston, Massachusetts) add an electron donor mixture to the influent at a point shortly before the influent enters the first filter. The electron donor solution was either a mixture of acetate, lactate, and pyruvate or a mixture of acetate, benzoate, and pyruvate. Benzoate was sometimes substituted for lactate due to the fact that carboxylic acids are common ozonation by-products (Camel and Bermond 1998). Since the focus of this project is conventional ozone/GAC systems, the use of benzoate was very practical. The electron donor concentration was always 1.5 mg/L of equivalent nitrate demand4 in excess of that required to stoichiometrically remove the influent concentrations of DO and nitrate. Thus, electron donor concentration was never the limiting variable. 4The equivalent nitrate demand was determined by calculating the concentration of electron donor required to stoichiometrically reduce NO3" completely to N2 . 31
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AWWA Research Foundation Removal of
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The mission of the AWWA Research Fo
Page 6 and 7: Disclaimer This study was funded by
Page 8 and 9: Serum Bottle Experiments ..........
Page 11 and 12: TABLES 1.1 Bromate removal in DFE a
Page 13 and 14: FIGURES 1.1 Effect of influent diss
Page 15: 3.32 Perchlorate removal vs. nitrat
Page 18 and 19: Perchlorate and chlorate salts are
Page 21 and 22: EXECUTIVE SUMMARY Bromate (BrO3~) a
Page 23 and 24: scale ozone-BAC plants is likely du
Page 25 and 26: RECOMMENDATIONS 1. To utilize BAG f
Page 27 and 28: CHAPTER 1. INTRODUCTION BACKGROUND
Page 29 and 30: PREVIOUS STUDIES - BROMATE 1 Siddiq
Page 31 and 32: ethanol was required to stimulate e
Page 33 and 34: were not measured, they can be pres
Page 35 and 36: one year prior to this experiment,
Page 37 and 38: 2.0 - e • • 8 i 8 a
Page 39 and 40: i S I i.o - 1.4 - 1.2 - 1.0 - 0.8 -
Page 41 and 42: ut the concentrations of oxygen and
Page 43 and 44: species that is able to reduce perc
Page 45 and 46: CHAPTER 2. MATERIALS AND METHODS MA
Page 47 and 48: BAG was formed by extensively prelo
Page 49 and 50: Floating Cover 1 Influent: LMW 20 (
Page 51 and 52: Backwash ing the BAG filters Two of
Page 53 and 54: Table 2.2 Agar recipe for plating e
Page 55: Streaked individual colony morpholo
Page 59 and 60: Metal-Catalyzed GAG Filter Experime
Page 61 and 62: perchlorate, nitrite, nitrate, and
Page 63 and 64: Table 2.5 Serum bottle experiment 2
Page 65 and 66: CHAPTER 3. RESULTS AND DISCUSSION B
Page 67 and 68: a two-week period. Over the two-wee
Page 69 and 70: To establish the effect of backwash
Page 71 and 72: o S 25 20 - 15 - 10 - O 50-min EBCT
Page 73 and 74: In general, the average percent bro
Page 75 and 76: measured nitrate concentration and
Page 77 and 78: Two data points in each of Figures
Page 79 and 80: 90 - ^ 80 - 70 - J 60 - o 11 1 50 -
Page 81 and 82: ench-scale and full-scale B AC filt
Page 83 and 84: omate removal was sustained (Figure
Page 85 and 86: Fraction Perchlorate Remaining, Fra
Page 87 and 88: Figure 3.18 Rods and cocci from the
Page 89 and 90: seen that the BAG samples contain a
Page 91 and 92: Bromate Reduction in DDW with Exoge
Page 93 and 94: The mass balance on nitrate + nitri
Page 95 and 96: N2O was not detected and no evidenc
Page 97 and 98: Table 3.10 Results of dilution-to-e
Page 99 and 100: 0 so o U ).0 - I 5.0 U ffl Addition
Page 101 and 102: o I Io U D o ou - 50 1 40 - 30 - 20
Page 103 and 104: Wash Tests Table 3.11 lists the res
Page 105 and 106: The next step was to determine if p
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Jar cio4- 42.8 40.4 40.5 41.1 6 C/C
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of nitrate on perchlorate reduction
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Effluent Perchlorate, C/C l.U 0.8 -
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was decreased. It is interesting to
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1 1.6 1.4 - 1.2 - .1.0- 1.5mg/L Inf
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or 1.5 mg/L nitrate showed no perch
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^——s 0 4 0 234 Incubation Time
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Figure 3.43 illustrates the differe
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Figure 3.44 Rods and protozoa from
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CHAPTER 4. ACTIVITIES AT THE METROP
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Perchlorate is only found in CRW, a
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Residual ozone. To reduce sample ov
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^ influent 0 effluent A mid • inf
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Effect of Nitrate The background ni
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Table 4.2 Control study for chemica
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PILOT-SCALE MOBILE PILOT PLANT STUD
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Mobile Pilot Plant Ozone The ozonat
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Table 4.4 Mobile pilot plant operat
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p o O. i Fraction Bromate Remaining
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CHAPTER 5. SUMMARY AND CONCLUSIONS
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Bromate removal increased as the in
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virgin Norit GAC showed an ion exch
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Microscopic examination of the biom
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CHAPTER 6. RECOMMENDATIONS TO UTILI
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Brock, T. D., M. T. Madigan, J. M.
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Kirisits, M. J., V. L. Snoeyink, an
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Rogers, K. 1997. Water Contaminated
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ABBREVIATIONS AWWA AWWARF American
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AWWA Research Foundation Advancing
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Removal of Bromate and Perchlorate in Ozone/GAC Systems

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