Determining the Efficacy of a Constructed Wetland as a Water Quality Improvement Strategy in an Urban Environment Public

Styes, Karen Renee (2014)

Permanent URL: https://etd.library.emory.edu/concern/etds/8k71nh37b?locale=fr
Published

Abstract

The specific aim of this study is to provide empirical evidence determining the efficacy of constructed wetlands in the study site's urban setting as a method for addressing stormwater quality issues. It is hypothesized that the constructed wetlands will improve water quality by lowering total coliform, E.coli, and turbidity concentrations and perhaps lower levels of conductivity as well. This study was conducted in the wetlands and lake system in the City of Pine Lake, Georgia. A portion of Snapfinger Creek is diverted through the Eastern (upstream) wetlands. Water flows from the Eastern wetlands to the lake, whose overflow discharges via a drop outlet into a culvert. This culvert also receives stormwater from the southwestern portion of the city, which may contain intrusion from septic tanks and/or leaking sewer pipes. The culvert leads to the Western (downstream) wetlands. The water ultimately discharges into Snapfinger Creek approximately 1000 meters downstream of the initial diversion into the Eastern wetlands. The area of the drainage basin entering the Eastern wetland is approximately 2.7 square miles (7.0 square kilometers). Sample points were designated at 4 strategic locations in the system and collected during the summer months of June - August, 2013 and winter months of December, 2013 - January, 2014. The following parameters were collected and analyzed from each site: total coliform, E. coli, turbidity, conductivity, water temperature, air temperature, pH, and dissolved oxygen. Total coliform and E. coli concentrations were generally lower and less variable during the winter months. Dissolved oxygen was higher during the winter months, likely due to lower temperature. Statistical analysis of paired data was performed using SAS 9.3. Correlations were calculated by using paired t-Tests of difference between the samples and 2-sided p-values. The effluent from the constructed wetland was determined to be significantly lower than the influent for the following parameters: total coliform, E. coli, and conductivity. E. coli samples obtained within 48 hours of rain resulted in significantly higher concentrations when compared to those taken during periods of no rain within 48 hours. The hypothesis that constructed wetlands improve water quality is supported by the data collected by this study.

Table of Contents

Table of Contents Pages

ABSTRACT ............................................................................................................... 1

BACKGROUND and SIGNIFICANCE ............................................................................ 2

INTRODUCTION ........................................................................................................ 4

MATERIALS and METHODS ........................................................................................ 6

Study site ................................................................................................................ 6

Sample collection ..................................................................................................... 7

Sample processing ................................................................................................... 9

Quality control ....................................................................................................... 10

Statistical Analysis Methods .................................................................................... 10

RESULTS ............................................................................................................... 11

STATISTICAL ANALYSIS .......................................................................................... 13

Total Coliform ........................................................................................................ 13

E. coli .................................................................................................................... 14

pH ......................................................................................................................... 15

Conductivity ............................................................................................................15

DISCUSSION .......................................................................................................... 20

LIMITATIONS .......................................................................................................... 23

CONCLUSIONS ....................................................................................................... 24

REFERENCES .......................................................................................................... 25

FIGURES

Figure 1. Sample point locations ............................................................................... 6

Figure 2. Total Coliform - Eastern Wetland Site 1 / Site 2 (Influent/Effluent) .............. 13

Figure 3 Total Coliform Site 1 vs. Western Wetland Effluent (Site 4) .......................... 13

Figure 4 E. coli Eastern Wetland Site 1 / Site 2 (Influent/Effluent)................................14

Figure 5 E. coli Site 1 vs. Site 4 ................................................................................14

Figure 6 pH Eastern Wetland Influent (Site 1) vs. Western Wetland Effluent (Site 4) ... 15

Figure 7 Conductivity - Site 1 vs Site 2 ..................................................................... 15

Figure 8 E. coli (colonies/100 mL) / Rain (1/10 in.) Site 1.......................................... 16

Figure 9 E. coli (colonies/100 mL) / Rain (1/10 in.) Site 2 ......................................... 16

Figure 10 E. coli (colonies/100 mL) / Rain (1/10 in.) Site 3 ....................................... 17

Figure 11 E. coli (colonies/100 mL) / Rain (1/10 in.) Site 4 ........................................17

APPENDIX A - Sampling Results

Table 1: Site 1 - Eastern Wetland Influent Summer Data ........................................... 29

Table 2: Site 1 - Eastern Wetland Influent Winter Data .............................................. 29

Table 3: Site 2 - Eastern Wetland Effluent Summer Data ........................................... 30

Table 4: Site 2 - Eastern Wetland Effluent Winter Data .............................................. 30

Table 5: Site 3 - Lake Effluent Summer Data ............................................................ 30

Table 6: Site 3 - Lake Effluent Winter Data ................................................................ 31

Table 7: Site 4 - Western Wetland Influent Summer Data .......................................... 31

Table 8: Site 4 - Western Wetland Effluent Winter Data ............................................. 31

APPENDIX B - Statistical Analysis .............................................................................. 31

Table 10 .................................................................................................................. 32

APPENDIX C - SAS 9.3 Output ...................................................................................34

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