Grantee Research Project Results
Final Report: Ultra-Low-Cost Reusable Solar Disinfection Sensor
EPA Grant Number: SV839487Title: Ultra-Low-Cost Reusable Solar Disinfection Sensor
Investigators: Lacks, Daniel J , Tippareddy, Charit , Maatouk, Chris , Stanley, Sam , Kang, Lei , Lu, Elaine , MacDougall, Gordon , Augustine, Ashley , Sinha, Annika , Pfau, David , Datta, Sanjit , Al-Serhaid, Sarah , Lundgren, Katherine
Institution: Case Western Reserve University
EPA Project Officer: Page, Angela
Phase: II
Project Period: April 1, 2019 through March 31, 2021 (Extended to March 31, 2022)
Project Amount: $75,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2019) Recipients Lists
Research Category: P3 Awards , P3 Challenge Area - Safe and Sustainable Water Resources
Objective:
The goal of the Billion Bottle Project is to provide reliable, cost-effective, and user-friendly alternatives for water sanitation to those in need. Our organization has chosen the avenue of solar disinfection, or SODIS, to accomplish this aim. SODIS has been proven to be the most cost-effective water disinfection technique for households in the developing world. The concept seems simple – a user exposes contaminated water to direct sunlight, and in a matter of hours the ultraviolet radiation is able to inactivate a sufficient amount of bacteria to yield drinkable water. In practice, this concept is complicated by the fact that weather conditions, the clarity of the water sample, and a myriad other conditions can affect the degree of ultraviolet light penetration into the sample, varying the time of exposure required dramatically. This degree of uncertainty has prevented SODIS from being used as widely as one might expect from such an efficient method of sanitation.
Rather than determining the safety of water treated using SODIS based on the length of time exposed to sunlight, we have developed reusable, low-cost devices which measure the dose of UV light that a sample is exposed to. The application of our devices, the OSPRI and SANTE, is user friendly. The OSPRI is a device that can be submersed in the container of drinking water; it contains a UV-sensitive dye that can be calibrated to change colors once the sample has been sufficiently irradiated. Similarly, the SANTE uses the same technology but in sticker form, and is even more cost-effective than the OSPRI and can be affixed to the outside of the container. Both devices provide an unambiguous endpoint to notify the user that the water is drinkable – a color change from blue to white which corresponds to a dose of UV light, not the time of exposure. The devices can then be placed in a dark space and will revert to their blue color, making them totally reusable. Our aim was for a production cost of under $1 per unit of the OSPRI and to make it reusable up to a year, thereby creating a high-accuracy and ultra-low-cost device that can help provide clean drinking water to our users.
Summary/Accomplishments (Outputs/Outcomes):
- We have developed an indicator formulation that changes color from blue to white in response to ultraviolet light. It is able to do so for at least 30 cycles without color degradation, and at least 90 cycles despite color degradation. In testing of the liquid formulation, the UV dose required to produce a color change remains stable for at least 90 days. Figure 1. Left to Right 12/13/19 before first cycle, 1/13/20, 2/24, 3/22, 4/6, 6/22, 7/20, 8/24- approx. 90 cycles.
- We developed a 3D-printable design of our OSPRI housing and now have a US patent application pending on our device. The ability to 3D print the housing reduces costs and increases availability of the product.
- We have made significant efforts to prevent the color decay observed in our solid formulation after 30 days of cycling. We experimented with many modifications of our formulation, including modification of the constituent parts, modification of environmental factors such as temperature, modification of storage methods, and experimented with new color-changing dyes. We were not able to extend the color vibrancy significantly beyond two months despite these modifications, and this is an area for future research and development.
- Because our work involves testing the concentration of bacteria in water samples, we devoted significant time to identifying faster and more efficient methods of quantifying coliforms in water samples. We were able to successfully implement the EPA method 1604 in our laboratory to approximate E. coli concentrations in water samples. We compared this method to a commercially available product – ColiScan – to explore its ability to detect E. coli in water samples.
- Two pilot field tests in Brazil and Kenya demonstrated the appropriate color changes of our chemical formulations (in the form of SANTE prototypes) with direct sunlight in the six-hour time frame known to be effective for solar disinfection. Disinfection tests using local drinking water sources demonstrated more rapid disinfection than traditional SODIS guidelines, suggesting that use of OSPRI or SANTE has the potential to speed disinfection.
- However, our field testing results did demonstrate issues with condensation forming within our OSPRI containers making it difficult to observe color changes, indicating a need for slight modifications of the design. This is an area which will require further research and development.
- Unfortunately, our work has been significantly impacted due to the COVID-19 pandemic, and was largely halted for several months due to state-wide shelter-in-place policies. Even after resumption of work, access to lab space was limited to maintain social distancing and we had limited access to spaces such as the campus solar simulator. In addition to a halt in laboratory testing, our planned field testing in Uganda, Kenya, and Zambia has been postponed indefinitely due to restrictions on international travel. We have had significant difficulties recruiting new staff as well, which has slowed progress significantly.
Figure 2 In testing of the liquid formulation, the UV dose required to produce a color change remains stable for at least 90 days
Figure 3 An example of one of our experiments to change the dye used. When switching from methylene blue to neutral red, we actually found that methylene blue did a significantly better job of maintaining its vibrancy after cycling. This shows the effect of a single cycle when neutral red was used as the dye.
Figure 4 A representative sample from our field experiments in Kenya is demonstrated above. Additionally, the image on the lower left demonstrates the color of the sensor after exposure to UV light, with the image on the right demonstrating the color of the sensor after being allowed to revert to its blue color.
Figure 5 Petrifilm Plates showing E. coli count duing SODIS treament
Figure 6. Final color of the sensor after staying in the dark for 48hrs.
Conclusions:
Though several of our goals for the past year, particularly field testing, could not be accomplished due to the pandemic, we made progress towards finalizing our devices and facilitating future field testing. We have developed a formulation which is UV sensitive and can maintain its vibrancy for at least 30 days. We have also developed a 3D-printable model for housing of our formulation, which will make it significantly simpler to manufacture and increase its availability. A US patent application has been submitted for our device. Unfortunately, limited access to campus facilities such as the solar simulator and international travel restrictions have made it difficult to conduct experiments on our device in real-world conditions, and these are important next steps to undertake. Certain research and development questions remain, which are how to improve our device housing to reduce condensation build-up, and how to continue to improve the longevity of our formulation.
Our device currently consists of an easily manufactured formulation with 3D-printable housing, making it significantly cheaper than any other current methods of water sanitation save for solar disinfection without the use of a dosimeter. However, as mentioned above, without the use of a UV dosimeter, solar disinfection carries several variables which are difficult to control for. Regarding the technical effectiveness of our device, field testing demonstrated that use of the SANTE form of our device (sticker) resulted in a color change after approximately 6 hours, though E. coli concentrations were sufficiently low after only 3. This indicates that our formulation required a higher UV dosage than necessary to effectively eliminate coliforms. However, this is an issue which can easily be remedied by modification of the proportions of the formulation’s constituent parts. Future field testing will be required to identify the proper proportions of these constituent elements and optimize the UV dose necessary for color change. Therefore, our limited field data does suggest that our device has the potential to be a technically effective and highly affordable UV dosimeter for use in solar disinfection.
Journal Articles:
No journal articles submitted with this report: View all 7 publications for this projectSupplemental Keywords:
Ultraviolet dosimeter, WASH, diarrheal disease, sustainable water management, drinking water treatment, water purification, water filtration, solar water treatment, water disinfection, pathogen removal, SODISProgress and Final Reports:
Original AbstractP3 Phase I:
Ultra-Low-Cost Reusable Solar Disinfection Sensor | 2018 Progress Report | Final ReportThe 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.
Project Research Results
- 2020 Progress Report
- 2019 Progress Report
- Original Abstract
- P3 Phase I | 2018 Progress Report | Final Report