Difference between revisions of "Greywater Wetland"

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Revision as of 18:35, 30 November 2021

Overview

Wetlands.jpg

Introduction

The Living Building Challenge imposes a rigorous set of standards for the most sustainable buildings in the world. Living Buildings are required to account for all 7 Petals of the Living Building Challenge: Place, Water, Energy, Health and Happiness, Materials, Equity, and Beauty. The Kendeda Building at Georgia Tech is in the process of certification by the Living Building Challenge, and is the first Living Building of its size and purpose. One of the main systems in the building is the greywater system which uses a constructed wetland to filter Greywater. Greywater wetland systems are still a relatively uncommon way for buildings to filter water from sinks, water fountains, showers, and other non-"black water" sources due to high cost, contamination risks, and the ease of putting greywater into the sewer system. However, if implemented correctly they can help clean greywater to acceptable standards for irrigation of non-edible plants and increase groundwater recharge. Our goal is to investigate the greywater system and test its overall filtration effectiveness.

System of Study

The greywater system filters greywater from the Kendeda Building, and releases the filtered water into groundwater reservoirs. Greywater from the Kendeda Building includes water from sinks, showers, and water fountains. The water flows from its source to a large cistern that is located in the back of the Kendeda Building, where it is temporarily stored. Water is then gradually pumped uphill to the constructed wetland that is located in the front of the Kendeda Building. The water finally moves through the wetland horizontally and is filtered using sediment, gravel, and local aquatic plants.

List of plants in the constructed wetland :

  1. Softstem Bulrush
  2. Pickerelweed
  3. Swamp Candle
  4. Cardinal Flower


Analogous Systems

Many areas utilize natural wetlands to help filter wastewater. Not only are wetlands used for filtration, many are home to a large biodiversity of plants and animals. Many water treatment wetlands also serve as wildlife sanctuaries. For example, the Arcata Marsh in Arcata, California. The Arcata Marsh was a wetland restoration project to reclaim lost marshland. This is an example of how wastewater can be used as a resource rather than a waste. It can be used to grow extremely biodiverse wetlands and restore ecosystems. While Kendeda's constructed wetland is a much smaller scale, the constructed wetland is making a miniature ecosystem on the building's perimeter.
Another similar system that is closer to Atlanta, Georgia is the Constructed Wetland Treatment System in Fort Deposit, Alabama. The system includes two separate constructed wetlands, side by side, that allows water to flow through them horizontally. The system was proven to meet water treatment standards, and it also promoted more biodiversity in the area.

Research

Hypothesis

Measurements of water quality from the start and end of the greywater system will decrease due to a variety of factors including possible evaporation and stagnation of water in the septic tank.

Purpose

Evaluate the effectiveness of the Kendeda Building’s Greywater filtration system by obtaining the following data from water at the inflow and outflow sample points.:

  • Depth/Volume in greywater tank and in constructed wetland
  • Dissolved oxygen (DO)
  • pH
  • Temperature
  • Conductivity
  • Chemical Composition

Observe temporal changes in the chemical composition of the water samples.
The Sample Pit.jpg


Methods

Ion Chromatography
This method is used to analyze concentrations of sulfates and chlorides
Colorimetry
This method uses color changes from the addition of a reagent to determine the concentration of species such as Nitrates, Nitrites, and Phosphates in water.
FAAS (Flame Atomic Absorption Spectroscopy)
This method is used to analyze the levels of Sodium, Magnesium, Calcium and Potassium in the system

Procedure

The following procedure will lay out how the sample taken from the input tank will be collected and analyzed in the lab.

1. The lid will be removed using a ratchet kit, being sure to not contaminate the bottom of the lid with other matter surrounding the tank opening. Then a 500 ml sample is removed from the septic tank using a "throw bucket."

Another option would be to hold up the lid without removing it completely and collect a sample using a throw bucket.

2. Immediately upon collecting the water sample, temperature, pH, TDS, and DO data will be collected directly from the bucket using pre-calibrated electrodes. This information will then be recorded.

3. A 30 mL syringe will be used to collect 4-(50 mL) aliquots from the throw bucket. In the end, there should be 2 test tubes containing 50 mL of water samples. The test tubes will be labeled as follows:

  • Filtered acidified
  • Filtered unacidified
The acidified samples will be acidified to pH 2.

4. After collected water samples, the lid will be replaced, making sure it is secure. Be care to NOT OVERTIGHTEN THE BOLTS.

5. The collected water samples will be taken back to the lab and bacteria will be filtered out.
Water Samples.png

6. If immediate analyses of the samples is not able to be done, the samples should be kept frozen until testing can be done.

Lab Procedures

  • Measuring Conductivity - EPA Method 120.1
  • Measuring Anions via Ion Chromatography - EPA Method 300.0
  • Measuring Nitrates/Nitrites via Spectrophotometry - EPA Method 352.1
  • Measuring Nitrates/Nitrites via Automated Spectrophotometry - EPA Method 353.2
  • Diazotization Method for Nitrate and Nitrite


Retention Rate Considerations
Flow Meter Calculations

  • Using the total volume of liquid, rain water data, and flow rate, we can easily calculate the retention time
  • We are collecting the rain data from a weather gage at the CRC
  • We are collecting the flow rate from a water gage connected to the septic tank
  • We are calculating the total volume of liquid using the total volume capacity of the tank and the height of the liquid within the tank


Potential Hazards

  • Danger in obtaining samples from open/exposed tank (fall hazards attributed to underground storage tank)
  • Exposure to pathogens while collecting water samples and testing in lab
  • Collecting samples in an active construction zone could entail construction related hazards
  • Exposure to Covid-19 (Spring 2019 - Spring 2021)
Will need constant supervision from the construction site manager
Will need hard hats, vests, and other protective equipment


Data and Graphs

Please note that due to the COVID-19 lockdown in the Spring semester, there is very little data or analysis for this period. Most of the analysis begins in the Fall of 2020 when we could begin collecting samples consistently.

Raw Data
Spring 2020 - Spring 2021


Temperature

Fall 2020:

The temperature patterns closely followed the air temperature. Overall, the temperature was found to be lower in the septic tank which could be explained by the water being stored in a dark tank underground. The temperature is highest in the gravel sample which is located in the direct sunlight.

Spring 2021:

The temperature readings followed similarly to those of the Fall. The change of temperature of all three sites followed the air temperature, with the lowest temperature being in the septic tank and the highest in the gravel wetlands.

pH

Fall 2020:

The pH is consistently below 7 for the three sampling sites. The pH is highest in the septic tank, where the highest reading was found to be 7.37 pH. The pH is lower in the constructed wetland and gravel samples, where rainwater enters the systems. Rainwater has a pH lower than tap water, at about 5.4 pH which explains the consistent lower readings.

Spring 2021:

pH measurements consistently around 7 for all the three sampling sites. All of the sampling sites had about the same pH throughout the semester, and the pH of the system slower increased. This could be due to a slight increase in use of the building toward the end of the semester.

Conductivity

Fall 2020:

Conductivity was consistently higher in the NE and NW corners of the wetland when compared with the SE and SW corners. This suggests there is greater chemical weathering in the northern side of the wetland. There is a spike in conductivity that coincides with the discovery of a change in the septic tank water from a clear color to a milky white color. This change was likely due to a dead animal breaching the tank and decomposing in the water.

Spring 2021:

Conductivity was relatively stable throughout the semester, with no significant changes. It was still higher in the NE and NW corners of the wetlands, and highest in the septic tank.

Dissolved Oxygen (DO)

Fall 2020:

Dissolved oxygen averaged between 2-5 mg/L throughout the semester in all three test sites (septic tank, wetland, gravel NW) but dropped to its lowest the same week as the spike in conductivity. This supports the conclusion that something organic was decomposing in the water. Decomposition of organic materials requires the consumption of DO, and explains the declining DO levels at the time the change in the septic tank water takes place.

Spring 2021:

Dissolved oxygen was higher this semester than in the Fall. However, it is difficult to draw conclusions from the cause of this due to fewer samples being taken and no clear and evident cause.

Oxidation-Reduction Potential

Fall 2020:

Oxidation-reduction potential (ORP) was typically highest in the gravel samples but was still relatively similar across the wetlands and gravel sample sites. This indicates very little change in dissolved elements such as oxygen across these sites. The septic tank had lower ORP values relative to the two other sample sites, and on October 14th, these values began to trend lower and lower for the remainder of the semester. This coincides with the qualitative observations pertaining to the color and smell of the septic water which we believed indicated that something had died in the tank. The ORP data supports this hypothesis because you would expect such measurements to plummet with decomposition.

Spring 2021:

Due to malfunctions with the probe, we are no longer taking ORP data from the samples.

Chloride

Fall 2020:

Chloride levels were lowest in the wetland water samples (below 50 ppm) and highest in the wetland gravel samples with numbers ranging from 0 to 200 ppm. This suggests that the main source of chloride in the wetland comes from the chemical weathering of the gravel. Since there is no weathering happening within the septic tank or in the outlet of the wetland, the chloride levels are much lower in those places than in the gravel.

Spring 2021:

The samples for Spring 2021 have not yet been analyzed for chloride.

Sulfate

Fall 2020:

Sulfate levels remain fairly consistent across every sample site until October 28th when there is a significant increase in Sulfate levels at the northwest gravel site. This is much later than when the anomalies in the septic tank were discovered, making it unlikely that this was attributable to those observations. This is likely the result of more resolved sulfate peaks using ion chromatography. Chloride levels in the gravel samples were unusually low on October 28th and beyond, potentially allowing for the sulfate signal to be better observed without the noise from a strong chloride signal.

Spring 2021:

The samples for Spring 2021 have not yet been analyzed for sulfate.

Nitrite and Nitrate

Fall 2020:

Nitrite and Nitrate ion concentrations have not yet been measured for every sampling site, but there is consistent data for the septic site from October to the end of the semester. There are variable levels of Nitrites and Nitrates for this period. The peaks in both of these species do not occur on the day that the anomalies in the septic tank (odd odor, yellowish color, flies, and worms) were first observed, and the levels are not high enough to indicate that there is something decomposing in the tank. We have not yet ruled out the possibility that an animal is decomposing in the septic tank, but the preliminary Nitrite and Nitrate data that we do have calls that theory into question.

Spring 2021:

Both Nitrate and Nitrite concentrations were consistently highest in the Septic Tank, persisting for extended periods of time. Conversely, concentrations in the wetlands tank and gravel samples rarely significantly exceeded the detection limit. Consequently, we believe that the wetlands is successfully filtering out Nitrates and Nitrates from septic tank effluent. Both analytes decrease in concentration over time in the septic tank, likely due to increased water flow from increased facilities use.

Phosphate

Fall 2020:

The samples for Fall 2020 have not yet been analyzed for phosphate.

Spring 2021: =

The samples for Spring 2021 have not yet been analyzed for phosphate.

Potassium & Magnesium

Fall 2020:

Both mafic and felsic rocks were considered to be present in the wetland gravel. The data suggests that the gravel is primarily felsic, as supported by the high levels of potassium in the gravel (between 0 and 200ppm) compared to the low levels of magnesium (between 0 and 5 ppm). Both potassium and magnesium were lowest in the wetland. Potassium was highest in the gravel (felsic) and magnesium was highest in the septic tank. Changes in magnesium levels in the septic tank align closely with the levels in both the gravel and the wetland. This suggests the magnesium is entering the wetland and gravel via the septic tank. The main source of magnesium can either be within the septic tank or primary effluent from Kendeda. Further analysis will be needed to determine the exact source of magnesium.

Spring 2021:

The samples for Spring 2021 have not yet been analyzed for potassium and magnesium.

Sodium

Fall 2020:

The septic tank had the highest sodium concentration across all of the sample sites. The wetlands tank and NW gravel sites generally had much lower concentrations but were fairly consistent and similar between themselves. This indicates that sodium ions are either collecting in the septic tank and failing to move downstream in the system or getting used by the biotic life in the wetlands. It is likely the latter hypothesis is true, indicating that the wetlands plants are able to effectively remove sodium ions from the system.

Spring 2021:

The samples for Spring 2021 have not yet been analyzed for sodium.

Calcium

Fall 2020:

Calcium ion concentrations were extremely high in the wetlands tank and low at the septic and gravel sites on September 16th. The most reasonable explanation for this anomalous data point is that rain from Hurricane Sally flushed weathered calcium from the gravel into the wetlands tank. However, even this seems unlikely since none of the other species, particularly the ions, follow this same pattern on September 16th. It is possible that this was simply an anomalous or outlier data point. After this point, calcium ion concentrations are similar and consistent across all three sample sites.

Spring 2021:

The samples for Spring 2021 have not yet been analyzed for calcium.

Experimental Modeling

One of our goals as a sub-team is to see how the greywater system at the Kendeda building can improve. One of the components of the greywater treatment system that our team has found to be an unnecessary addition to the greywater system is the septic tank, so our team is developing experimental models in which we can test the effects of the septic tank on greywater treatment. We set up three models that mimic the Kendeda greywater system, and we only make one slight change to each one. One model has the normal septic tank, one has a septic tank filled with gravel, and one does not have a septic tank but rather a tank that constantly stirs the water. The purpose of the last model is to simulate a system without a septic tank where water is only able to flow through pipes. Our hypothesis for this experiment is that the septic tank models will not have any beneficial effect on greywater treatment. We hope that the data collected through these models will confirm data gathered from the original Kendeda System.

Models.jpg


Sustainability

  • Plan to measure flow rate using meters rather than 'slug' test
    • Avoids potentially harmful chemicals
  • Sample Tube Reduction and Reuse
    • Reduced number of samples from 15 to 9 total tubes per week
    • Sample tubes will be reused every semester to avoid plastic waste


Outlook

The Greywater Wetland Sub-team project is split into two phases. The first phase of our project involves gathering background information about the greywater treatment system at Kendeda as well as conducting water sampling and analysis to test the water quality in the system. This phase began in the Spring 2019 semester and is ongoing. The second phase of the project involves the development of experimental models to test the impact of different septic systems on the Kendeda greywater reclamation system. This data is being collected to support a policy proposal to Fulton County suggesting the creation of regulations specific to greywater collection and treatment that do not require a septic tank. Currently, Fulton County treats greywater the same as blackwater, requiring the installation of an expensive and likely useless septic tank for greywater wetland reclamation systems like the one used at Kendeda.

Final Posters

Spring 2020 Poster

Fall 2020 Poster

Spring 2021 Poster

Annotated Bibliography

Arden, S, and X Ma. “Constructed Wetlands for Greywater Recycle and Reuse: A Review.” Science of the Total Environment, vol. 630, 2018, pp. 587–599.

This is a review of a case study done to see if constructed wetlands meet the microbiological standards for water reuse. They measured pathogens, E. Coli, BOD, and other metrics. From their study, they concluded that the constructed wetland is unable to meet standards on its own. However, the wetland combined with ultraviolet radiation and chlorination could meet standards for water reuse.

Carleton, J., Grizzard, T., Godrej, A., Post, H., Lampe, L., & Kenel, P. (2000). Performance of a Constructed Wetlands in Treating Urban Stormwater Runoff. Water Environment Research, 72(3), 295-304. Retrieved February 26, 2020, from www.jstor.org/stable/25045379

This study looked at the performance of constructed wetlands in northern Virginia of removing pollutants from stormwater runoff. More specifically, the study focused on stormwater runoff from a residential townhome complex. Researched collected data from 33 runoff events from April 1996 to May 1997, and results generally showed positive pollutant removal levels.

Cooper, R. (2008). Going Grey. Landscape Architecture Australia,(117), 75-77. Retrieved February 26, 2020, from www.jstor.org/stable/45142506

This is a brief but interesting report on how Australia is trying to use greywater for gardening. The report provides a short summary on what greywater is and what potential hazards could come from using it. By properly regulating its use, then residents would be able be less water intensive and use it in a much more efficient way.

Crites, R., Dombeck, G., Watson, R., & Williams, C. (1997). Removal of Metals and Ammonia in Constructed Wetlands. Water Environment Research, 69(2), 132-135. Retrieved February 26, 2020, from www.jstor.org/stable/25044854

This older paper from 1997 discusses how constructed wetlands have to potential to remove toxic metals and ammonia from the water. This experiment was conducted from July 1994 to December 1995, and researchers indicated significant removal of 13 metals, some of which include lead, copper, and zinc. The main vegetation used in this experiment was bulrush and some cattail.

Dixon, A. M., Butler, D., & Fewkes, A. (1999). Guidelines for Greywater Re-Use: Health Issues. Water and Environment Journal, 13(5), 322–326. doi: 10.1111/j.1747-6593.1999.tb01056.x

This 1999 paper reviews the possible threats that grey water reuse can pose. It reviews the risks and provides modified guidelines taking into consideration public health. The paper recommends that faecal coliform should be used as an indicator of microbe quality. One key observation from the paper is that residence time in the system should be kept at a minimum. Thus things like septic tanks can cause adverse health effects due to microbial proliferation.

EPA. (1993). Constructed Wetlands for Wastewater Treatment and Wildlife Habitat. Retrieved April 20, 2020. https://www.epa.gov/wetlands/constructed-wetlands-wastewater-treatment-and-wildlife-habitat-17-case-studies

This article discusses various constructed wetlands. Although it is a bit dated, it provides some good comparisons for our system.

Hernandez Leal, L., Temmink, H., Zeeman, G., & Buisman, C. J. N. (2010). Comparison of Three Systems for Biological Greywater Treatment (Vol. 2, pp. 155-169): Water.

This source analyzes the effectiveness of three separate greywater treatment methods: “aerobic treatment in a sequencing batch reactor, anaerobic treatment in an up-flow anaerobic blanket reactor and combined anaerobic-aerobic treatment”. They collected greywater from 32 homes, and transferred to a lab for treatment in lab-scale reactors. The study noted that aerobic greywater treatment proved more beneficial than anaerobic treatment, as it removed 90% COD and 97% anionic surfactants compared to only 51% COD removal and 24% anionic surfactant removal in anaerobic conditions.

Paulo, P. L., Begosso, L., Pansonato, N., Shrestha, R. R., & Boncz, M. A. (2009). Design and configuration criteria for wetland systems treating greywater. Water Science and Technology, 60(8), 2001–2007. doi: 10.2166/wst.2009.542

The goal of this research was to design a grey-water wetland for a household and then determine whether the criteria used for design was appropriate. The paper shows the strengths, weaknesses and potential for household grey-water wetlands using current criteria.

Ramprasad, C, et al. “Removal of Chemical and Microbial Contaminants from Greywater Using a Novel Constructed Wetland: GROW.” Ecological Engineering, vol. 106, no. PA, 2017, pp. 55–65.

GROW (Green Roof-Top Water Recycling System) located in southern India. This source has some good data on quantities we would like to measure such as pH, BOD, and others. An interesting note is that their system was more efficient, especially removing BOD, during summer months.

Ramprasad, C, and Ligy Philip. “Surfactants and Personal Care Products Removal in Pilot Scale Horizontal and Vertical Flow Constructed Wetlands While Treating Greywater.” Chemical Engineering Journal, vol. 284, 2016, pp. 458–468.

This is a study for how effective constructed wetlands are at removing pollutants from greywater. Interestingly, they concluded that vertical flow wetlands are marginally more effective than horizontal flow wetlands. The chemicals and procedures they used to analyze the water could be useful for our experiment.

Robinson, D. (1994). Tansley Review No. 73. The Responses of Plants to Non-Uniform Supplies of Nutrients. The New Phytologist, 127(4), 635-674.

This source analyzes plant response to a non-uniform nutrient supply. Since we believe that the constructed wetland is not receiving enough nutrients, this source will be helpful in predicting an understanding of the response of the wetland species to a lack of essential nutrients. The specific nutrients covered by this source include ammonium, nitrate, potassium, and phosphorus. Of these four nutrients, we will be testing the constructed wetland for three of them: nitrate, ammonium, and phosphate.

Winward, G. P., Avery, L. M., Frazer-Williams, R., Pidou, M., Jeffrey, P., Stephenson, T., & Jefferson, B. (2008). A study of the microbial quality of grey water and an evaluation of treatment technologies for reuse. Ecological Engineering, 32(2), 187–197. doi: 10.1016/j.ecoleng.2007.11.001

This source analyzes how microbes grow in different types of grey water wetlands. They compared the development of different pathogens in grey water wetland systems to development in traditional water treatment systems. The wetlands did not perform as well as traditional systems, but the most effective wetland was a vertical flow reed bed (VFBR).

Team Members

Name Major Years Present
Christina Lu Earth & Atmospheric Sciences January 2020 - March 2020
Donald Gee Civil Engineering January 2020 - March 2020
Jacob Varner Civil Engineering January 2020 - Present
Samantha Brewer Civil Engineering January 2020 - December 2020
Hailey Akins Chemistry August 2020 - Present
Lucy Bricker Environmental Engineering August 2020 - December 2020
Elijah Craig Environmental Engineering January 2021 - Present