Arsenic Removal With Iron-Tailored Activated Carbon Plus Zero-Valent Iron

76 Pages·2010·0.94 MB·English

Arsenic Water Technology Partnership

Arsenic Removal With
Iron-Tailored Activated
Carbon Plus Zero-Valent Iron

©2010 Water Research Foundation and Arsenic Water Technology Partnership. ALL RIGHTS RESERVED.
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©2010 Water Research Foundation and Arsenic Water Technology Partnership. ALL RIGHTS RESERVED.
Arsenic Removal With Iron-Tailored Activated Carbon Plus Zero-Valent
Iron

Prepared by:
Weifang Chen, Robert Parette, Will Sheehan, Fred S. Cannon, Brian A. Dempsey
The Pennsylvania State University
Department of Civil and Environmental Engineering
212 Sackett Engineering Building
University Park, PA 16802

Jointly Sponsored by:
Water Research Foundation
6666 West Quincy Avenue, Denver, CO 80235

and

U.S. Department of Energy
Washington, D.C. 20585-1290

Published by:

WERC, a Consortium for Water Research Foundation
Environmental Education and
Technology Development at
New Mexico State University
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SANDIALOSALAMOS A CONSOANRTDIU TMEC FHONRO ELNOVGIRYO DNEVMEELNOTPAML EENDTUCATION
©2010 Water Research Foundation and Arsenic Water Technology Partnership. ALL RIGHTS RESERVED.
DISCLAIMER

This study was jointly funded by the Water Research Foundation and the U.S. Department of
Energy (DOE) under Grant No. DE-FG02-03ER63619 through the Arsenic Water Technology
Partnership. The comments and views detailed herein may not necessarily reflect the views of
the Water Research Foundation, its officers, directors, affiliates or agents, or the views of the
U.S. Federal Government and the Arsenic Water Technology Partnership. The mention of trade
names for commercial products does not represent or imply the approval or endorsement of the
Foundation or DOE. This report is presented solely for informational purposes.

Copyright © 2010
by Water Research Foundation and Arsenic Water Technology Partnership

ALL RIGHTS RESERVED.
No part of this publication may be copied, reproduced
or otherwise utilized without permission.

Printed in the U.S.A.

©2010 Water Research Foundation and Arsenic Water Technology Partnership. ALL RIGHTS RESERVED.
CONTENTS

LIST OF TABLES ........................................................................................................................ vii 
LIST OF FIGURES ....................................................................................................................... ix 
FOREWORD ............................................................................................................................... xiii 
ACKNOWLEDGMENTS ............................................................................................................ xv 
EXECUTIVE SUMMARY ........................................................................................................ xvii 
CHAPTER 1: INTRODUCTION ................................................................................................... 1 
Background ......................................................................................................................... 1 
Arsenic Removal Technology............................................................................................. 1 
pH Effect on Arsenic Removal by ZVI and Iron (hydr)oxides .......................................... 2 
Iron Corrosion and Iron Release ......................................................................................... 2 
Iron Corrosion by Electrolytic Cells ................................................................................... 3 
Research Objectives ............................................................................................................ 4 
CHAPTER 2: MATERIALS AND METHODS ............................................................................ 5 
Materials ............................................................................................................................. 5 
Water Sources for Pilot Columns and rapid small-scale column test (RSSCT) ..... 5 
Activated Carbons ................................................................................................... 5 
Methods............................................................................................................................... 6 
Iron Tailoring by Iron-salt Evaporation .................................................................. 6 
Rapid Small-Scale Column Tests (RSSCTs) .......................................................... 6 
Zero-Valent Iron (ZVI) and Iron-Loaded GAC for As Removal in RSSCTs ........ 7 
Iron Pre-Corrosion, Aging, and Idling in RSSCTs ................................................. 7 
Pilot Columns.......................................................................................................... 7 
Sampling Protocol and Chemical Analysis ........................................................... 12 
CHAPTER 3: RESULTS AND DISCUSSIONS ......................................................................... 13 
Effect of Temperature on Iron Tailoring by Evaporation ................................................. 13 
RSSCT vs. Pilot-scale Columns ....................................................................................... 14 
Pilot-scale Studies with Zero-valent Iron Rod and GAC .................................................. 16 
Pilot-Scale Studies With Electrolytic Solubilization And Iron-Tailored GAC ................ 22 
Pilot-Scale Studies with Electrolytic Solubilization Achieved with 0.01 or
0.02A, Plus Iron-Tailored GAC ................................................................ 23 
Pilot-Scale Studies with Electrolytic Solubilization Achieved with 0.1 A, Plus
Iron-Tailored GAC .................................................................................... 28 
Zero-Valent Iron With Iron-Tailored GAC In RSSCTs ................................................... 31 
RSSCTs: Arsenic Removal with Pre-corroded Galvanized Steel Fittings
Coupled with Iron-tailored GAC .............................................................. 32 
Performance of Perforated Steel Chamber Preceding Iron-tailored GAC ............ 34 
v
©2010 Water Research Foundation and Arsenic Water Technology Partnership. ALL RIGHTS RESERVED.
vi | Arsenic Removal With Iron-Tailored Activated Carbon Plus Zero-Valent Iron
CHAPTER 4: CONCLUSIONS ................................................................................................... 47 
CHAPTER 5: SIGNIFICANCE TO UTILITIES ......................................................................... 49 
REFERENCES ............................................................................................................................. 51 
ABBREVIATIONS ...................................................................................................................... 55 

©2010 Water Research Foundation and Arsenic Water Technology Partnership. ALL RIGHTS RESERVED.
TABLES

2.1 Water quality characteristics of the groundwater used in this study ...................................5 
2.2 Pilot-scale columns operational conditions .........................................................................9 
2.3 Composition of zero-valent iron sources (percent %) .......................................................12 
3.1 Iron content and BVs to breakthrough for carbons that were iron-preloaded by the
evaporation method, with curing at 50−100°C ..................................................................14 
3.2 Bed volumes to 10 µg/L As breakthrough in RSSCT versus pilot columns with iron
tailored carbons ..................................................................................................................16 
3.3 Bed volumes to 10 µg/L As breakthrough in pilot columns with zero-valent iron rods
and either iron-tailored GAC or virgin GAC. For Column 5, the rods reached all the
way to the column’s bottom. For all others, the rods remained in the top two-thirds of
the media ............................................................................................................................21 
3.4 Theoretical and measured iron dose for electrolytic cells* ...............................................32 
3.5 Arsenic distribution in GS #1 (iron-tailored GAC coupled with corrosion of
galvanized steel fittings) after 250,000 BVs ......................................................................34 
3.6 Column operating parameters and BVs to 10 µg/L breakthrough* ...................................44 

vii
©2010 Water Research Foundation and Arsenic Water Technology Partnership. ALL RIGHTS RESERVED.
©2010 Water Research Foundation and Arsenic Water Technology Partnership. ALL RIGHTS RESERVED.
FIGURES

2.1 Photograph of pilot-scale columns .......................................................................................8 
2.2 Electrolytic solubilization cells ..........................................................................................10 
2.3 Branched rod configuration used in Columns #11 to 15. ..................................................11 
3.1 RSSCT using arsenic-containing groundwater, for iron-loaded GAC, with preloaded
iron curing at temperatures of 50−100°C. Y-axis µg/L As. ..............................................13 
3.2 Arsenic breakthrough for iron-tailored (60oC) carbon in RSSCTs and Pilot Column
#3........................................................................................................................................15 
3.3 Arsenic breakthrough for iron-tailored (100oC) carbon in RSSCTs and Pilot Column
#4........................................................................................................................................15 
3.4 As breakthrough for pilot columns with virgin AquaCarb and plain steel mesh +
virgin AquaCarb.................................................................................................................17 
3.5 Back pressure buildup for Columns #1 and 2 ....................................................................18 
3.6 Iron concentration in effluent from Column #2 .................................................................18 
3.7 As breakthrough for pilot columns with straight and branched rods (rod diameters ¼
inch) ...................................................................................................................................19 
3.8 As for pilot columns, while comparing the effect of pH, EBCT, iron-tailored carbon
and smaller branched rod (rod diameters ¼ inch, unless otherwise listed) .......................20 
3.9 Iron concentration in effluent for Column #5, with straight rods that extended through
the full media depth ...........................................................................................................22 
3.10 Electrolytic solubilization chamber ...................................................................................23 
3.11 Effluent arsenic concentration in Column #17: 0.02 A electrolytic solubilization,
virgin GAC.........................................................................................................................24 
3.12 Back pressure and voltage vs. BVs in Column #17: 0.02 A electrolytic solubilization,
virgin GAC.........................................................................................................................25 
3.13 Effluent arsenic concentration vs. BVs for Column #18, 19 and 20 .................................26 
3.14 Backpressure vs. BVs for Column #18, 19 and 20 ............................................................27 
3.15 Electrolytic cell voltages vs. BVs for Column #18, 19 and 20 ..........................................27 
ix
©2010 Water Research Foundation and Arsenic Water Technology Partnership. ALL RIGHTS RESERVED.
x | Arsenic Removal With Iron-Tailored Activated Carbon Plus Zero-Valent Iron
3.16 Uneven iron loading in Column #6 when 0.1 A was applied across the ZVI
electrolytic cell ...................................................................................................................29 
3.17 Effluent Arsenic Concentration from Pilot Columns #7−10. Influent Concentration
50−60 ppb, targeted EBCTs as listed, and these EBCTs were maintained for the first
1,000−1,500 BVs ...............................................................................................................29 
3.18 Release of Iron from Electrolytic Pilot Columns Operated at 0.1A, targeted EBCTs as
listed, and these EBCTs were maintained for the first 1,000−1,500 BVs .........................30 
3.19 Pressure Build-up during Operation of Electrolytic Pilot Columns Operated at 0.1 A,
targeted EBCTs as listed, and these EBCTs were maintained for the first 1,000−1,500
BVs ....................................................................................................................................30 
3.20 Operational Voltage of Electrolytic Pilot Columns Operated at 0.1 A, targeted EBCTs
as listed, and these EBCTs were maintained for the first 1,000−1,500 BVs .....................31 
3.21 RSSCT of iron tailored GAC coupled with galvanized steel (GS#1) and without (#1);
both systems operated at pH 6±0.3 using the arsenic-containing groundwater as
influent (As 47−55 µg/L). Dashed line indicated where the GS#1 system was idled
for 6 days............................................................................................................................33 
3.22 pH effect on Mini column performance (A) Arsenic effluent from GAC column. (B)
Arsenic removed by steel chamber. (C) Filterable arsenic after steel chamber. Lines
indicate where the columns were idled for 7 days (Dotted line: pH 7.5; dashed: pH 6;
Solid line: pH 6−6.5) .........................................................................................................35 
3.23 Arsenic removal with no idle (PS #3), one idle (PS #1) and 3 idles (PS #2). (A) As
effluent from GAC column. (B) As removal in steel chamber. (C) Filterable arsenic
leaving steel chamber. Solid line indicates where PS #2 idled for 7 days, dashed line
indicates where PS #1 idled for 7 days. All columns were operated at pH 6±0.3 .............38 
3.24 Idling effect on Fe release. (A) Total Fe released from steel chamber. (B) Filterable
Fe released from steel chamber. (C) Fe effluent from GAC column. Solid line is
where PS#2 idled for 7 days on 3 occasions. D) Ferrous iron in filtered water released
from steel chamber. Dashed line is where PS#1 idled once for 7 days. ............................40 
3.25 Scanning electron microscopy of: (A) Fresh precorroded steel sheets, (B) Aged
precorroded steel sheets, and (C) Steel sheets employed in PS#2, after use. (D) Steel
sheets employed in PS#4, after use. ...................................................................................41 
3.26 Effect of pH, pre-corrosion, aging, and idling on: (A) Total Fe released from steel
chamber, (B) Filterable Fe released from steel chamber, (C) Fe accumulated in GAC
column (including preloaded iron). ....................................................................................43 

©2010 Water Research Foundation and Arsenic Water Technology Partnership. ALL RIGHTS RESERVED.