Remediation of groundwater contaminated with arsenic through enhanced natural attenuation: Batch and column studies

Saeedreza Hafeznezami; Amity G Zimmer-Faust; Dukwoo Jun; Megyn B Rugh; Heather L Haro; Austin Park; Jae Suh; Tina Najm; Matthew D Reynolds; James A Davis; Tarannom Parhizkar; Jennifer A Jay

doi:10.1016/j.watres.2017.06.029

Remediation of groundwater contaminated with arsenic through enhanced natural attenuation: Batch and column studies

Water Res. 2017 Oct 1:122:545-556. doi: 10.1016/j.watres.2017.06.029. Epub 2017 Jun 12.

Authors

Affiliations

¹ Department of Civil and Environmental Engineering, University of California, Los Angeles 5732 Boelter Hall, Box 951593, Los Angeles, CA 90095, USA. Electronic address: Saeedreza@ucla.edu.
² Department of Civil and Environmental Engineering, University of California, Los Angeles 5732 Boelter Hall, Box 951593, Los Angeles, CA 90095, USA.
³ Drumlin Environmental, LLC, 97 India Street, Portland, ME 04101, USA.
⁴ Earth Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
⁵ Department of Material Science and Engineering, University of California, Los Angeles, 410 Westwood Plaza, Los Angeles, CA 90095, USA.

PMID: 28628877
DOI: 10.1016/j.watres.2017.06.029

Abstract

Batch and column laboratory experiments were conducted on natural sediment and groundwater samples from a contaminated site in Maine, USA with the aim of lowering the dissolved arsenate [As(V)] concentrations through chemical enhancement of natural attenuation capacity. In batch factorial experiments, two levels of treatment for three parameters (pH, Ca, and Fe) were studied at different levels of phosphate to evaluate their impact on As(V) solubility. Results illustrated that lowering pH, adding Ca, and adding Fe significantly increased the sorption capacity of sediments. Overall, Fe amendment had the highest individual impact on As(V) levels. To provide further evidence for the positive impact of Ca on As(V) adsorption, isotherm experiments were conducted at three different levels of Ca concentrations. A consistent increase in adsorption capacity (26-37%) of sediments was observed with the addition of Ca. The observed favorable effect of Ca on As(V) adsorption is likely caused by an increase in the surface positive charges due to surface accumulation of Ca²⁺ ions. Column experiments were conducted by flowing contaminated groundwater with elevated pH, As(V), and phosphate through both uncontaminated and contaminated sediments. Potential in-situ remediation scenarios were simulated by adding a chemical amendment feed to the columns injecting Fe(II) or Ca as well as simultaneous pH adjustment. Results showed a temporary and limited decrease in As(V) concentrations under the Ca treatment (39-41%) and higher levels of attenuation in Fe(II) treated columns (50-91%) but only after a certain number of pore volumes (18-20). This study illustrates the importance of considering geochemical parameters including pH, redox potential, presence of competing ions, and sediment chemical and physical characteristics when considering enhancing the natural attenuation capacity of sediments to mitigate As contamination in natural systems.

Keywords: Arsenic; Column experiments; Groundwater; Natural attenuation; Remediation; Sorption.

MeSH terms

Adsorption
Arsenic
Groundwater*
Phosphates
Water Pollutants, Chemical*

Substances

Phosphates
Water Pollutants, Chemical
Arsenic