Living Building Science Fall 2021
Greywater Wetland Team
Molly Booker, Lucy Bricker, Donald Gee, Lacee Pinkelman,
Anna Redanz, Rebecca Siegel, Jacob Varner
Molly Booker: mbooker63@gatech.edu
Lucy Bricker: lbricker7@gatech.edu
Donald Gee: dgee3@gatech.edu
Lacee Pinkelman: lacee@gatech.edu
Contacts
References
The Greywater Wetland Team has been focusing on the continuous monitoring of phosphorus, nitrate/nitrite, and oxygen content of the Fulton County mandated Septic Tank in the Kendeda building on Georgia Tech's Campus.
In past semesters, this research has been primarily aimed at investigating whether or not the Septic Tank is an integral part of the greywater system within the Kendeda living building. This semester the project pivoted after we began observing low dissolved oxygen levels that were often less than one within the septic tank. This suspicion was prompted by the physical symptoms of the presence of iron bacteria such as an oil like sheen on top of the Septic Tank. We started measuring the iron concentration in order to test our hypothesis.
This holds significant to the end project goal in showing the significance of the Septic Tank in Kendeda and the potential it has for actually decreasing the water quality.
Abstract
The on-site analysis of water included measurements of the dissolved oxygen content present in the tanks. We operated under an SOP approved by EH&S. We collected data from two sampling sites一the Septic Tank and the Wetlands Tank.
For water sampling in both the Septic Tank and Wetlands Tank, we would collect one vial of water, roughly about 40 mL in total. This water was then filtered to remove all of the bacteria content to test for the concentrations of phosphate and ferrous iron.
To measure the dissolved oxygen content, a probe was inserted directly into the water inside the tanks until a stable reading was produced.
Spectrophotometric methods were used to test for both Phosphate and Ferrous Iron concentrations. We used the EPA Method 365.3 to test for phosphate concentrations and lab protocol from the School of Earth and Atmospheric Sciences at Georgia Tech to test for ferrous iron concentration.
Methodology
We plan to perform a 16s rRNA gene sequence to identify the bacteria that is growing and living in the Septic Tank. One of Dr. Kostas’ graduate students has agreed to help us run the test and we can complete this later in the semester. From here we will see what bacteria is present and determine if any of them are harmful. If so, we may need to treat the water to get rid of them.
We also would like to test what kinds of organic compounds are in the septic tank to investigate why/how microbes are growing in the tank from only greywater.
Future Direction
The project’s direction has changed and shifted throughout the semester. At first, we were mainly focusing on phosphorus and nitrogen levels in the Septic Tanks. Once we found iron in the tank, our team started to focus on the cause of the iron in the tank, and based on this research we concluded that both iron and iron bacteria are present in the Septic Tank. The next step is to perform a bacterial identification in order to confirm the presence of common iron bacteria.
We believe that the septic tank is promoting the growth of iron bacteria in the greywater system, and this supports our original hypothesis that the septic tank not beneficial to the greywater treatment. From our statistical analysis of the water quality indicators, it is also apparent that the septic tank either worsens or does not influence the water quality indicators of the system. Therefore, our findings suggest that the septic tank should not be required for greywater treatment for future living buildings.
Conclusions
As seen in past semesters, the nitrate and nitrite contents remained higher in the Septic Tank than the Wetlands Tank. The tank became anoxic around halfway through the semester, which motivated a switched from our routine oxygen testing to monitoring the iron content. The iron content increased steadily during this semester and caused a shift in our weekly monitoring procedures. This semester we also completed a long term data analysis where we compared the concentration of pollutants in the Septic Tank to the concentration of pollutants in the wetland. We looked at 13 water quality indicators* to compare the Septic Tank to the wetland using a test for homogeneity of variance. Seven of the indicators showed that there was no difference in quality between the two samples and the other six indicated that the water quality in the wetland was higher than that of the Septic Tank. The figures below show four key water quality measurements that have been tracked since September 2020: nitrites, nitrates, conductivity, and dissolved oxygen.
*Calcium, chloride, conductivity, dissolved oxygen, potassium, magnesium, sodium, nitrates, nitrites, oxidation reduction potential, pH, sulfates, and temperature
Results
Figure 1. Undiluted iron concentration in the Septic Tank verses the Wetlands Tank.
Figure 2. First sample day of the semester.
Chart 5. Iron Concentrations in the greywater wetland system over Fall 2021.
Background
The goal of this project is to characterize the greywater filtering system of the constructed wetland in front of the Kendeda Living Building. Greywater is relatively clean ‘waste’ water that generally comes from sinks or kitchens. It can be processed differently than blackwater (sewage) and either released into groundwater or reused.
We hypothesize that a holding tank, which we commonly refer to as the Septic Tank, is an unnecessary component by reducing the overall water quality in the system. The ultimate goal of this project is to perform a statistical analysis to show the negative impact that the Septic Tank has on the water quality, and ultimately suggest changes in the current greywater system guidelines for future living buildings.
Acknowledgements
A huge thank you to Professor Meg Grantham, Dr. Jennifer Leavey, and the other faculty advisors. A huge thanks, as well, to Steve Place for providing valuable information and resources throughout the semester, as well as to Dr. Kostas for providing guidance for all bacteria testing queries.
Anna Redanz: aredanz3@gatech.edu
Rebecca Siegel: becca.siegel@gatech.edu
Jacob Varner : jvarner8@gatech.edu
Chart 1. Nitrite Concentrations in Wetlands, Septic Tank and gravel between Fall 2020 and Spring 2021.
Chart 3. Conductivity in Wetlands, Septic Tank and gravel between Fall 2020 and Spring 2021.
Chart 2. Nitrate Concentrations in Wetlands, Septic Tank and gravel between Fall 2020 and Spring 2021.
Chart 4. Dissolved Oxygen in Wetlands, Septic Tank and gravel between Fall 2020 and Spring 2021.
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