Removal of Bromate and Perchlorate in Ozone/GAC Systems

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effect of parameters such as bromate and perchlorate concentration, dissolved oxygen (DO) concentration, nitrate concentration, pH, temperature, and the role of ozonation preceding BAG. To investigate advanced oxidation processes to determine whether these reactions can produce efficient removal of perchlorate, and if so, to develop the process at the bench-scale. > Emphasis will be placed on the ozone-hydrogen peroxide-GAC process, virgin GAC, GAC impregnated with metals such as copper and zinc, and GAC mixed with solids such as iron, zinc, and aluminum. To optimize the bromate and perchlorate removal processes that show the most encouraging results and to monitor the product water for potability. To test the most promising of the bromate and perchlorate removal processes at the pilot- scale. APPROACH The project included bench-scale work conducted at the University of Illinois at Urbana- Champaign and the Metropolitan Water District of Southern California (MWDSC). In general, one water quality or operational parameter was changed at a time, in order to observe its effect on bromate and perchlorate removal. Additionally, pilot-scale work for removal of bromate and perchlorate using BAG filtration was completed at the La Verne pilot plant at MWDSC; these experiments were carried out using filter parameters that were tested at the bench-scale. CONCLUSIONS 1. Increasing the influent DO concentration to the BAG filters from 2.1 mg/L to 13.6 mg/L decreased bromate removal from 40 percent to 11 percent at a 20-minute empty-bed-contact time (EBCT). The lack of bromate reduction observed in fullxx
scale ozone-BAC plants is likely due to the high concentrations of DO entering the filters. 1. Filter history is very important to bromate removal in a BAG filter. For instance, the negative effect of high DO concentrations on the bromate-reducing bacteria was not immediately reversible when the DO concentration is subsequently reduced. 2. When the influent nitrate concentration to the BAG filters was increased from 0.3 to 42.3 mg/L, bromate removal decreased from 86 to 49 percent at a 26-minute emptybed contact time. 3. The influent sulfate concentration to the BAG filters did not have a significant effect on bromate reduction. 4. At a 25-minute EBCT, bromate removal increased from 20 percent to 40 percent when the influent pH to the BAG filters decreased from 8.2 to near neutral pHs (6.8- 7.5). This is beneficial since pH control may be used to reduce bromate formation during ozonation and increase biological bromate removal since bromate formation decreases as the pH decreases. 5. Under similar operating conditions, better bromate removal was observed in BAG filters operated with Champaign-Urbana water (CUW, a groundwater source) than using Lake Michigan water (LMW). Thus, composition of the source water can have a dramatic impact on bromate reduction in a BAG filter. 6. Bromate removal results obtained in a one-inch inner-diameter BAG filter were reproduced in a 2-inch inner-diameter BAG filter, suggesting that scale-up of the bench-scale results should not be of concern. 7. Perchlorate and bromate removal were observed in pilot-scale BAG filters. 8. Backwashing the BAG filters using filter effluent with a low DO concentration (2 mg/L) and no chlorine did not adversely affect bromate reduction. 9. For lower bromate concentrations (10-20 [ig/L) and longer EBCTs (25-50 minutes), bromate removal increased as the influent bromate concentration increased. However, constant mass concentration bromate removal was observed at higher influent bromate concentrations (20-50 ug/L) and shorter EBCTs (10-20 minutes), which may indicate that the electron donor concentration was limiting bromate removal under these conditions. xxi
Page 1: AWWA Research Foundation Removal of
Page 4 and 5: 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: EXECUTIVE SUMMARY Bromate (BrO3~) a
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 and 56: Streaked individual colony morpholo
Page 57 and 58: METHODS UTILIZED FOR PERCHLORATE RE
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
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In general, the average percent bro
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measured nitrate concentration and
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Two data points in each of Figures
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90 - ^ 80 - 70 - J 60 - o 11 1 50 -
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ench-scale and full-scale B AC filt
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omate removal was sustained (Figure
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Fraction Perchlorate Remaining, Fra
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Figure 3.18 Rods and cocci from the
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seen that the BAG samples contain a
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Bromate Reduction in DDW with Exoge
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The mass balance on nitrate + nitri
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N2O was not detected and no evidenc
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Table 3.10 Results of dilution-to-e
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0 so o U ).0 - I 5.0 U ffl Addition
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o I Io U D o ou - 50 1 40 - 30 - 20
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Wash Tests Table 3.11 lists the res
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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
Page 163 and 164:
ABBREVIATIONS AWWA AWWARF American
Page 166:
AWWA Research Foundation Advancing
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Removal of Bromate and Perchlorate in Ozone/GAC Systems

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