School of Earth, Environmental, and Marine Sciences Faculty Publications and Presentations

Document Type


Publication Date



A potential environmental impact associated with horizontal directional drilling is the inadvertent return of bentonite-based drilling fluid to the surface via naturally occurring fractures or fissures. This study investigated a range of flocculants consisting of water-soluble linear polyacrylamides (PAMs) differing in charge (anionic, neutral, and cationic), biopolymer (chitosan) and gypsum for treating the bentonite suspension that might release with runoff or into stream water. Laboratory jar test were conducted with a 0.4 % (w/v) bentonite suspension having an average initial turbidity of 1,217 nephelometric turbidity units (NTU). None of the PAMs by themselves were effective in flocculating bentonite suspension (> 690 NTU), but adding gypsum in a combination with anionic PAM enhanced the flocculation reaction (< 120 NTU). The biopolymer performed better than the PAMs alone by lowering turbidity to 437 NTU. A simple, passive dosing system was tested in which bentonite-laden turbid water was pumped into a length of pipe with a jute lining treated with the chemical and passed through a geotextile dewatering bag. Both the biopolymer and the combination of gypsum and anionic PAM were effective, reducing turbidity by 86-95 % relative to influent bentonite suspension (1,188 NTU). These results suggest that simple, inexpensive flocculation systems can be deployed to reduce turbidity caused by bentonite spills.


Copyright © IJAER 2016, All right reserved.

Copyright of any article submitted to International Journal of Agriculture and Environmental Research (IJAER) will be retained by the author(s) under the Creative Commons license, which allows unrestricted use, distribution, and reproduction provided the original work is properly cited.

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

First Page


Last Page


Publication Title

International Journal of Agriculture and Environmental Research



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.