Optimizing the Solar Water Disinfection Method to Produce Potable Water from Ecologically-treated Wastewater Using Recycled Polyethylene Terephthalate Bottles

Open Access
- Author:
- Sheehan, M. William
- Area of Honors:
- Civil Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Rachel Alice Brennan, Thesis Supervisor
Patrick Reed, Thesis Honors Advisor - Keywords:
- solar water disinfection method (SODIS)
eco-machine
E. coli
total coliforms
ultraviolet-A rays - Abstract:
- According to the World Health Organization, more than two million people die of waterborne diseases every year, and 1.1 billion people lack a source of safe drinking water. Every day, 4,500 children die from diarrhea due to a water-borne contaminant (World Health Organization, 2000). The Solar Water Disinfection (SODIS) method is proven to remove pathogenic contamination from water. In an epidemiological study of a cholera outbreak in Kenya, an 88% reduction in diarrhea cases was observed among SODIS users (Conroy et al., 2001). In this method, reused, unscratched, two liter polyethylene terephthalate (PET) bottles are filled with water and then placed on their sides atop corrugated metal roofs in full sun for a minimum of six hours to deactivate pathogens using the ultraviolet-A (UVA) waves from the sun. The materials used in this method are accessible and economical, making SODIS a water treatment process capable of helping many people who live in developing nations. To date, an estimated 2.1 million people in 24 countries have benefited from SODIS (SODIS, 2012). However, the SODIS method is not effective when the influent turbidity is greater than 30 NTU. In the United States, the average turbidity value of domestic wastewater is approximately 60 NTU (Natural Resource Management and Environment Department, 1992), and drinking water turbidity must be less than or equal to 0.3 NTU in at least 95 percent of the samples in any month, never exceeding 1 NTU (US EPA, 2012). The objective of this project was to investigate the potential of sustainably transforming domestic wastewater into potable water, by combining an ecological wastewater treatment system (i.e., Eco-Machine) to reduce turbidity, with modifications of the SODIS method to optimize disinfection efficiency. A series of 20 oz. PET bottles were filled with Eco-Machine effluent and placed on four different backgrounds to determine the effects of UVA intensity and temperature on the SODIS method. The four backgrounds included corrugated metal (a common rooftop material in developing countries), blackened corrugated metal (to increase temperature), a mirror (to enhance UVA transmission), and gravel (control). The level of disinfection was quantified by sacrificing the bottles after a six hour period, and counting the number of E. coli and general coliforms. The broad outlook of this thesis is to refine the SODIS method and apply it for producing potable water from wastewater in developing nations at minimal cost.