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Effect of DOM Size on Organic Micropollutant Adsorption by GAC Anthony Kennedy, and R. Scott Summers Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.5b00411 • Publication Date (Web): 08 May 2015 Downloaded from http://pubs.acs.org on May 11, 2015
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Environmental Science & Technology
Effect of DOM Size on Organic Micropollutant Adsorption by GAC Anthony M. Kennedy*, R. Scott Summers Department of Civil, Environmental, and Architectural Engineering, University of Colorado, Campus Box 428, Boulder, CO, 80309, USA *
Corresponding author phone: +1 303 735 4147; fax: +1 303 492 7317; e-mail:
[email protected] ABSTRACT: Granular activated carbon (GAC) adsorption of the micropollutants 2-
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methylisoborneol (MIB) and warfarin (WFN) at ng/L levels was investigated in five waters with
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isolated natural dissolved organic matter (DOM) held at a constant dissolved organic carbon
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concentration. Each water was evaluated for competitive adsorption effects based on the
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pretreatment of ultrafiltration, coagulation, and additional background micropollutants. Using the
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breakthrough with unfractionated DOM as a baseline, on average, the water with lower
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molecular weight (MW) DOM decreased MIB and WFN adsorption capacity by 59% while the
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water with higher MW DOM increased MIB and WFN adsorption capacity by 64%. All waters
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showed similar decreasing MIB and WFN adsorption capacity with increasing empty bed contact
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time (EBCT), with more dramatic effects seen for the more strongly adsorbing WFN. On average,
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MIB and WFN adsorption kinetics were two times slower in the water with higher MW DOM
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compared to the water with lower MW DOM, as described by the intraparticle pore diffusion
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tortuosity. Increased adsorption competition from 27 micropollutants other than MIB and WFN
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at environmentally relevant concentrations had little to no effect on MIB and WFN breakthrough
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behavior. Any competitive effect from background micropollutants became indiscernible at
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longer EBCTs.
1 ACS Paragon Plus Environment
Environmental Science & Technology
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INTRODUCTION
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Granular activated carbon (GAC) has potential for the control of organic micropollutants (MPs)
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that occur at sub to low µg/L concentrations in drinking water sources.1-3 However, adsorption
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by GAC is not selective for MPs as background dissolved organic matter (DOM), which is
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ubiquitous in all waters from either natural or anthropogenic sources, is also adsorbed. DOM
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covers a large range of molecular weights (MW), as it is comprised of humic substances (humic
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and fulvic acids) and non-humic substances, often termed natural organic matter, as well as
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anthropogenic components such as wastewater effluent organic matter, urban runoff, and
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agricultural runoff. Because of the high surface area in GAC micropores (dpore
