Removal of Bromate and Perchlorate in Ozone/GAC Systems

More documents

Recommendations

Info

Reagents Reagent grade sodium bromate (Aldrich Chemical Co., Inc., Milwaukee, WI) and sodium perchlorate (Sigma Chemical Co., St. Louis, MO) were used to prepare 1000 mg/L stock solutions. Other chemicals were of reagent grade quality or better. Where appropriate, chemicals were dried overnight at 105 °C and stored in a desiccator. METHODS UTILIZED FOR BROMATE REDUCTION EXPERIMENTS Biologically Active Carbon - Small Columns BAC filters were constructed in 2.5-cm (1-inch) inner-diameter glass pipes (Ace Glass, Vineland, NJ). The pipes were capped with Teflon® and steel endcaps. A small layer of 3-mm (0.1- inch) glass beads was placed below the carbon bed in order to promote uniform flow characteristics and prevent channeling. Influent was pumped upflow through the columns using peristaltic Masterflex pumps (Cole-Parmer, Vernon Hills, EL). Each influent container was fitted with a stainless steel, Teflon®, or Plexiglas® floating cover, to maintain the DO concentration. The influent DO concentration was adjusted to the desired level by sparging with compressed nitrogen or oxygen. Four filters were constructed to evaluate bromate removal from CUW using Norit RO 0.8 GAC (Norit Americas Inc., Atlanta, GA). The average GAC pellet diameter and length were 0.8 and 3.4 mm, respectively. Each filter contained one-quarter preloaded carbon and three-quarters fresh carbon. The preloaded carbon was taken from a bench-scale filter that had been operated with a 2- minute EBCT for 40,000 bed volumes with dechlorinated surface water (Danville filter effluent, Consumer's Illinois, Danville, Illinois). At the end of this preloading period, the carbon was used in experiments not discussed in this report, and approximately 30 percent of the influent DOC and 10 percent of the influent bromate were consistently being removed by the microorganisms during a 45- day experiment. At this time, the preloaded carbon was considered to be biologically active and at steady state. Aforementioned, the preloaded carbon was then mixed with fresh carbon in the construction of four new filters. This was done in order to seed the fresh carbon with microorganisms, thereby reducing the preloading time required to stimulate biological activity in the filters. 20
BAG was formed by extensively preloading the carbon filters with CUW that had been dechlorinated by sulfite addition. The purpose of the preloading period was to establish a biofilm on the carbon, and then the BAG filter could be used for various biological bromate reduction experiments. The preloading conditions were determined in accordance with the experiments that were to immediately follow the preloading time. It was planned to use the BAG filters in experiments with an influent DO concentration of 2 mg/L and a variety of EBCTs between 4 and 50 minutes. Therefore, the carbon filters were preloaded with 2,700 bed volumes of dechlorinated CUW with an EBCT of 10 minutes and an influent DO concentration of approximately 2 mg/L. Two parallel filtration experiments were set up, each with two columns in series, for a total of four filters. All filtration experiments with CUW were run with two filters in series, so that two EBCTs could be evaluated simultaneously. For example, influent water first passed through a 25-minute filter and then through another 25-minute filter for a total EBCT of 50 minutes. The only difference between the preloading conditions of the parallel filters was the influent nitrate concentration; one set-up was operated with an influent nitrate concentration of 0.3 mg/L and the other with an influent nitrate concentration of 5.0 mg/L. No exogenous electron donor was added to CUW experiments. A schematic diagram showing the BAG filters using CUW is shown in Figure 2.1. As the filters were preloaded, the percent bromate removal continued to decrease as the bromate reduction capacity of the carbon was approached. However, near the end of the preloading period, the percent bromate removal began to increase. This indicated that while the abiotic reduction capacity of the carbon was approaching exhaustion, microbiological bromate reduction had commenced. For the filters being preloaded in the presence of 5.0 mg/L nitrate, the bromate removal decreased to reach a minimum of 27 percent as the abiotic bromate reduction capacity of the carbon approached exhaustion but then increased to approximately 53 percent removal by the end of the preloading time due to the onset of biological bromate reduction. For the filters being preloaded in the presence of 0.3 mg/L nitrate, the bromate removal decreased to reach a minimum of 37 percent but then increased to 83 percent removal by the end of the preloading period due to biological bromate reduction. These data show that the BAG filters were biologically active after the preloading period. To attain steady state bromate removal, the BAG filters were operated with an EBCT of 25 minutes (each filter) for 30 days. For the last two weeks of this period, the filter being operated with an influent nitrate concentration of 0.3 mg/L and a 25-minute EBCT removed 83 ± 5 percent bromate. 21
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 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: CHAPTER 2. MATERIALS AND METHODS MA
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
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
Page 107 and 108:
Jar cio4- 42.8 40.4 40.5 41.1 6 C/C
Page 109 and 110:
of nitrate on perchlorate reduction
Page 111 and 112:
Effluent Perchlorate, C/C l.U 0.8 -
Page 113 and 114:
was decreased. It is interesting to
Page 115 and 116:
1 1.6 1.4 - 1.2 - .1.0- 1.5mg/L Inf
Page 117 and 118:
or 1.5 mg/L nitrate showed no perch
Page 119 and 120:
^——s 0 4 0 234 Incubation Time
Page 121 and 122:
Figure 3.43 illustrates the differe
Page 123 and 124:
Figure 3.44 Rods and protozoa from
Page 125 and 126:
CHAPTER 4. ACTIVITIES AT THE METROP
Page 127 and 128:
Perchlorate is only found in CRW, a
Page 129 and 130:
Residual ozone. To reduce sample ov
Page 131 and 132:
^ influent 0 effluent A mid • inf
Page 133 and 134:
Effect of Nitrate The background ni
Page 135 and 136:
Table 4.2 Control study for chemica
Page 137 and 138:
PILOT-SCALE MOBILE PILOT PLANT STUD
Page 139 and 140:
Mobile Pilot Plant Ozone The ozonat
Page 141 and 142:
Table 4.4 Mobile pilot plant operat
Page 143 and 144:
p o O. i Fraction Bromate Remaining
Page 145 and 146:
CHAPTER 5. SUMMARY AND CONCLUSIONS
Page 147 and 148:
Bromate removal increased as the in
Page 149 and 150:
virgin Norit GAC showed an ion exch
Page 151 and 152:
Microscopic examination of the biom
Page 153:
CHAPTER 6. RECOMMENDATIONS TO UTILI
Page 156 and 157:
Brock, T. D., M. T. Madigan, J. M.
Page 158 and 159:
Kirisits, M. J., V. L. Snoeyink, an
Page 160 and 161:
Rogers, K. 1997. Water Contaminated
Page 163 and 164:
ABBREVIATIONS AWWA AWWARF American
Page 166:
AWWA Research Foundation Advancing
show all

Removal of Bromate and Perchlorate in Ozone/GAC Systems

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?