Grantee Research Project Results
Final Report: Pasteurization Using a Lens and Solar Energy (PULSE) Method
EPA Grant Number: SU835346Title: Pasteurization Using a Lens and Solar Energy (PULSE) Method
Investigators: Tam, Kawai , Quach, Christopher , Ochoa, Estevan , Farag, Jason , Park, Jung , Matsumoto, Mark
Institution: University of California - Riverside
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 15, 2012 through August 14, 2013
Project Amount: $14,999
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2012) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Air Quality , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Objective:
The PULSE system uses solar energy and a Fresnel lens to pasteurize contaminated water. The PULSE method achieved a pasteurization rate of 2 liters per hour (2L/hr.) by using a Fresnel lens to focus sunlight onto a bottle of water until a pasteurization temperature of 60°C was reached. A water pasteurization indicator was used in the bottle to alert users that the water had reached the required temperature for proper pasteurization. This will ensure that the water is safe for consumption. A device was developed to incorporate the lens so that end users can safely and easily use the PULSE system.
Objective:
The main goal of the PULSE system is to develop a device to increase the rate of the pasteurization by using a Fresnel lens. This device will be compared with existing solar energy based treatments such as the solar disinfection (SODIS) method and solar cooker (Hot Plate) or heat tests to determine the effect of heat and ultraviolet (UV) disinfection on pasteurization.
Summary/Accomplishments (Outputs/Outcomes):
The outputs and outcomes focused on three components: design of the PULSE system, effectiveness of sunlight on pasteurization at various volumes and an economic assessment of the complete working system. Design of the PULSE system was dependent on the meteorological conditions of Riverside, CA which is at latitude 33° 57’ 11” N. During the PULSE tests, the daytime range of temperatures was from 60 to 90°F, with conditions ranging from cloudy to sunny. These temperatures and weather conditions were important in determining the optimum lens size required for strong sunlight concentration. Clear skies and hot temperatures were optimal conditions for our device, but even on cloudy days with low ambient temperatures, our device was still effective.
The main components required for the PULSE system are a 3’ x 2’ Fresnel lens, a stand, a Polyethylene Terephthalate (PET) bottle of water contaminated with Escherichia coli (Migula Castellani and Chalmers) (from here on referred to as E. coli) and relatively clear skies. The Fresnel lenses are commonplace in older projector style big screen television sets and are considered a waste stream material which can be obtained at a low cost. During initial testing, the Fresnel lens was held by an all-steel frame made from scrap metal pieces, but this was impractical because of welding requirements, potential corrosion issues and the potentially high cost of shipping due to the heavy weight. After careful design considerations, a second PULSE frame prototype was constructed using only PVC piping. The PVC was cheaper and lighter while still strong enough to support the lens. The PVC frame was coated in spray paint for UV protection and could be dismantled and reassembled with ease. This was used as the leading prototype for PULSE testing.
SODIS, PULSE and Hot Plate tests were conducted to determine the effects of pasteurization on volumes of contaminated water made of 1 mM potassium chloride (KCl) with an initial E. coli concentration of 107 cfu/mL. SODIS consisted of a clear PET bottle with contaminated water placed out in direct sunlight for a minimum of six hours. The hot plate tests involved using a hot plate to heat contaminated water in a beaker. The PULSE tests were similar to the SODIS tests but with concentrated solar energy focused onto the bottle by a Fresnel lens.
When testing all three methods, samples were taken initially and at specific time and/or temperature intervals. These samples were diluted and plated onto 3M Petrifilm E. coli coliform plates. The plates were incubated at 37°C, over a 16 to 24 hour period. The results were analyzed to determine the rate of bacterial inactivation. The ratio of the E. coli concentration at each time interval and the initial bacterial concentration (C/Co) were plotted as a function of time to determine the performance of the three treatment methods.
The PULSE and Hot Plate tests were the fastest at pasteurizing water, while the SODIS method was the slowest. Hot Plate tests demonstrated that heat was effective but still required at least 25 minutes and a temperature of 70°C to achieve pasteurization. From SODIS testing, it was determined that even after two hours, complete bacterial inactivation was not achieved. PULSE was proposed as an improvement upon the SODIS method and the results confirmed this hypothesis. The PULSE system was able to reach approximately 60°C and pasteurize a 500 mL bottle of E. coli contaminated water within 15 minutes.
From the success of the PULSE system, optimization tests were performed. To research the system’s effectiveness on common surface waters of developing nations, tests were performed using E. coli spiked water with a turbidity of 500 NTU. To further optimize the system, tests were conducted using bottles painted half-black and bottles placed halfway into soil. All of the optimization tests were very successful, resulting in similar or greater results than tests using only a clear PET bottle.
It was determined that temperature and UV had a synergistic relationship in inactivating bacteria. PULSE utilized both pathways and was concluded as the most efficient and sustainable water pasteurization method.
Conclusions:
The PULSE method increases the production of safe drinking water due to the lower pasteurization temperatures (60°C) and shorter periods of time (15 minutes) required to treat contaminated water. The PULSE method is an improvement on the solar cooker and SODIS methods due to the combined effects of heat and UV. Tests with high turbidity and on different background surfaces were also conducted and demonstrated that no significant reduction occurred in pasteurization ability. The recommended maximum turbidity level for the SODIS method is 30 NTU. However, the PULSE system was able to achieve proper pasteurization with a 500 NTU turbidity level. Unlike the SODIS method which requires the placement of bottles on a metal surface, the PULSE system does not need to be conducted on special background materials. It was shown that even on a dirt background the PULSE method will function properly. Therefore it is concluded that among all the conditions tested, the PULSE method is the best alternative for pasteurization.
Journal Articles:
No journal articles submitted with this report: View all 2 publications for this projectSupplemental Keywords:
Sustainable energy, renewable energy, emergency preparedness, boiling water, pathogen elimination, waterborne diseases, protozoa, virus, MS2, bacteriophage, continuous flow, PVC, education, heat transfer, insulation.Relevant Websites:
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https://sites.google.com/site/pulseucr/ Exit
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The 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.