Grantee Research Project Results
Final Report: Evaluation and Expansion of Solar Disinfection Method for Reclaimed Residential Greywater
EPA Grant Number: SU835726Title: Evaluation and Expansion of Solar Disinfection Method for Reclaimed Residential Greywater
Investigators: Phelps, Patricia , Staff, George , Boydston, Kelli , Drueke, Emma , Edgar, Christina , Farrar, Mariah , Gage, Stephanie , Gonzalez, Andrea , Hasan, Samer , Hixson, Michael , jaimes, Isabelle , Jeffries, Ben , Lankford, Caitlyn , Leatham, Katy , McGill, Michelle , Lilly, Kristine , Newcomb, Paul , Peterson, Miranda , Reynolds, Dylan , Savercool, Elizabeth , Schulze, Matthew , Searle, Marcus , Selvaggio, G.P. , Spangle, Chynna , Staton, Jered , Strickland, Kevin , Thompson, Thomas , Walden, Josh
Institution: Austin Community College
EPA Project Officer: Hahn, Intaek
Phase: I
Project Period: August 15, 2014 through August 14, 2015
Project Amount: $13,742
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2014) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Sustainable and Healthy Communities , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Objective:
The solar disinfection of greywater (SODIS), is a method that has been developed and proven as a means to produce potable water in a low-cost, effective, and nontoxic manner. Currently over 2 million people in 28 developing countries use the SODIS method for daily drinking water (Centers for Disease Control. 2012).
Issues of water scarcity affect every continent on the planet. More than 1.6 billion people live in areas suffering from water scarcity, and more than 500 million people are approaching this situation. This problem encompasses over one fourth of the world’s population (Figure 1). In the United States, the challenges http://bigislandnow.com/2014/01/16/ of water scarcity issues are being exacerbated by intense drought across the entire Southwest, including California, Texas and Oklahoma (USDM, U. S. 2015). Water shortage within the U.S. is not just an environmental concern when our current daily demand for water threatens the availability of this precious resource in the future. A crisis may soon emerge into other areas of the U.S. when local surface and groundwater sources can no longer support our increasing demand for water (GreenFacts. 2008). It is estimated that there will be a 50% shortfall of water supply for many counties in central Texas within the next two decades based on current water usage and demographics (USDM, U. S. 2015).
Figure 1
Figure 2. A woman using SODIS
In Phase I of this research project, the Austin Community College S-STEM research team has proposed that solar disinfection (SODIS) can be used in the United States as a way to recycle greywater in a residential setting. “Greywater is all reusable wastewater from residential […] bathroom sinks, bath tub shower drains, and clothes washing equipment drains” (EPA Region IX, 1998). Water can be recycled just like any other recycling medium such as aluminum, paper and plastic. Its process is aptly named greywater recycling. Recycled greywater can be used in many applications around the home and can provide safe irrigation water for lawns and gardens while also reducing the amount of water each home uses.
While the SODIS method is well established to produce drinking water without chemicals or energy by using recycled plastic bottles, the process is limited by the amount of water that can be treated at one time. The focus of Phase I was to explore different vessel configurations to increase the quantity of water produced, and lessen the time it takes to disinfect the water.
Summary/Accomplishments (Outputs/Outcomes):
Using a standardized laboratory greywater solution (synthetic greywater) that was capable of maintaining the viability of the E. coli, students ‘spiked’ synthetic greywater and divided it into two tubes: 1.) A solar UV (ultraviolet) transmitting tube and 2.) A darkened tube of the same material which allowed no penetration of light, as the control. This approach allowed students to evaluate the effectiveness of the solar disinfection prototype vessels and solar collectors. The use of a standardized laboratory greywater solution helped to ensure valid analysis of experimental results to compare the effectiveness of greywater disinfection between different experimental runs. The Biotechnology team also worked on culturing a strain of E. coli that is more resistant to the
chemicals normally found in greywater to simulate the type of E. coli bacteria that is more commonly found in a residential setting. This hardy strain of E. coli would serve to improve efficacy of solar disinfection prototype designs. A comprehensive report of findings and outputs regarding standardizing laboratory greywater, culture of a chemically resistant strain of E. coli and final testing procedures, protocols and analysis are further discussed in the project summary with supporting data and graphs.
Figure 3. ACC S-STEM student Joe Rodriguez.
The Design Optimization and Fabrication team was comprised of students with various disciplines of engineering, math, physics, and environmental majors. At the writing of this report the Design Optimization team has developed three prototypes for testing standardized (synthetic) greywater. A one-half-liter (0.5L) borosilicate glass tube with a high reflective parabolic trough was tested and yielded adequate disinfection, with a 4-log reduction (99.99%) of E. coli cell viability. A comparison study between borosilicate glass and UV transmissive acrylic was performed using a three liter Acryrite® tube and a three liter borosilicate glass tube with a 3-fold wider diameter. Again, test analysis demonstrated adequate disinfection with a 4-log reduction in E. coli cell viability and indicated a negligible difference in efficiency of disinfection between borosilicate glass and Acrylite® brand acrylic. In Phase I, design prototypes progressively expanded vessel size while focusing on modifying reflective accoutrement to decrease the time it takes to achieve disinfection.
Figure 4. ACC-S-STEM students perform
testing on solar disinfection prototypes.
ACC students hope to complete two additional experiments before the National Sustainable Expo in April. Experiment 4 will be a comparative study of solar collector design and the effect of reflective intensity of light based on the design of the solar collector in Prototype 1. Both the reflectivity of the material and the parabolic shape of the reflector will be compared. Experiment 5 will be an evaluation of the expansion of the test vessels and optimal solar collector design determined from Experiment 4. Students project that the new prototype designs will demonstrate a substantial increase in volume capacity of the disinfection vessel while significantly reducing disinfection time. Data, Findings, Outputs/Outcomes are detailed in the project summary with supporting photos of prototypes designs. SOP’s for the use of Prototype designs are published online and referenced at the end of this report.
Conclusions:
Austin Community College students have proven the concept of applying the SODIS solar disinfection approach towards the sanitation of greywater, as described in the project The Evaluation and Expansion of the Solar Disinfection Method of Reclaimed Residential Greywater. Solar disinfection of water can be achieved at larger volumes and at a more rapid disinfection rate than outlined by the SODIS method of disinfection used for drinking water. The use of solar disinfection can be very effective in the residential setting and has the potential to save the United State billions of gallons of water per year. Solar power, which is the energy source on which solar disinfection operates, is less energy-consuming in comparison to energy costs required to operate other disinfection systems such as ozonolysis. Solar disinfection can also reduce the need for toxic chemicals such as chlorine in residential greywater disinfection processes. This will lessen water disinfection byproducts from the environment.
Supplemental Keywords:
Water, physical and biological integrity of the systems, improvements in water purification and distribution, water conservation, sustainable water management, urban water planningThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.