Stormwater runoff from urban and agricultural watersheds carries nitrate, which is difficult to remove because it is highly soluble and thought to be relatively inert in abiotic processes such as ion exchange and sorption. Thus, current practice relies on denitrification to capture nitrate in stormwater treatment practices, requiring storage of captured stormwater, anaerobic conditions, and enough residence time for the bacteria to convert nitrate to nitrogen gas. The purpose of this research was to (1) quantify abiotic nitrate removal and removal capacity of two granular activated carbons (GACs), and (2) illustrate use of GACs in stormwater treatment practices. Batch and upflow column experiments found that two commercially available GACs captured nitrate abiotically, although competition between (bi)carbonate and nitrate limited removal of nitrate. Compared with removal of nitrate by denitrification, abiotic capture of nitrate during storm events requires less stormwater storage volume and less residence time to remove nitrate because it accumulates on the media as stormwater passes through the filter. This suggests that nitrate can be removed from stormwater with less storage and smaller treatment practices.
Bibliographical noteFunding Information:
The authors thank the Minnesota Pollution Control Agency for funding this research through its Federal Clean Water Act Section 319 grant program, project B43205 c.o. 1-3. The authors thank Greg Johnson the project manager for steering us through the reporting process. The authors thank Norit Americas and Carbon Resources, Inc. for donating the GAC media for these experiments. The authors also thank several undergraduate and graduate students for assisting with the experiments described herein: Anne Haws, Lanre Adekola, Elliot Spronk, Laina Breidenbach, and Ugonna Ojiaku. The authors also thank Professors Jian Peng (University of Saskatchewan) and Peter Weiss (Valparaiso University) for their helpful insight and advice. Finally, the authors thank Professor Paul Capel (University of Minnesota) for providing timely laboratory space to conduct the experiments while primary laboratory space was under renovation.
Copyright 2016, Mary Ann Liebert, Inc.
Copyright 2018 Elsevier B.V., All rights reserved.
- granular activated carbon
- urban runoff