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Document Type

Thesis - University Access Only

Award Date

2015

Degree Name

Master of Science (MS)

Department

Civil and Environmental Engineering

First Advisor

Guanghui Hua

Abstract

One of the major impacts that construction activity has on the environment is the disturbance of large quantities of soil, which, during storm events, are susceptible to erosion and transport into natural water systems. The U.S. Environmental Protection Agency is currently reviewing data in order to develop a more strict turbidity limit, one that will likely be difficult to comply with using current best management practices. One of the promising methods of being able to meet this limit is flocculation of suspended soil using organic polymers, such as polyacrylamide (PAM). The objective of this research was to study factors affecting the PAM flocculation process, to draw conclusions about the mechanisms involved, and to pave the way for future research with the goal of making PAM flocculation of construction site sediment an effective and accessible process. To accomplish this, synthetic stormwater runoff solutions were created using soil samples from South Dakota construction sites. These solutions were flocculated with a range of proprietary PAM products, under varying temperatures, using a jar test unit in order to determine the effects of polymer properties and temperature. In a second round of experimentation, one soil sample, polymer, and temperature were used, but other factors, such as mixing conditions, calcium concentrations, pH, and dissolved organic matter were varied. The first round of tests revealed that anionic PAMs have an optimal dose of ~1 mg/L in solution, after which turbidity increases again. It was also determined that higher charge density PAMs performed better at low doses, and PAMs with higher molecular weight performed better overall. Temperature had a significant effect, with cold temperatures hindering turbidity reduction. Flocculation between soil particles and PAM is a rapid process. The majority of turbidity was removed within 2 minutes of mixing and 2 minutes of settling. Increasing solution calcium concentration and lowering pH within the range of 5 to 9 also aided flocculation. Dissolved organic matter had no discernible effects. A number of the trends observed in this study could be applied in the field to help reduce turbidity in construction site runoff by PAMs.

Library of Congress Subject Headings

Stormwater infiltration -- South Dakota Construction industry -- Environmental aspects -- South Dakota Runoff -- South Dakota Polyacrylamide Turbidity Flocculation

Description

Includes bibliographical references (pages 63-65)

Format

application/pdf

Number of Pages

75

Publisher

South Dakota State University

Rights

In Copyright - Educational Use Permitted
http://rightsstatements.org/vocab/InC-EDU/1.0/

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