fairfolio
Saved Projects

Does the Surface Clarity of Plastic Bottles Affect Solar Water Disinfection as Measured by the Presence of E. coli?

CSEF · 2004 Microbiology

Kelli M. Muirheid · Kastner (George W.) Intermediate School, Fresno

Overview

Objectives/Goals Solar water disinfection (SODIS) is a method for improving the safety of drinking water in third world countries. 2-liter clear plastic bottles are filled with available water and then placed horizontally in the sun for six hours. Bacteria such as e coli are destroyed due to a combination of heat and UV rays. In actual application, bottles are reused multiple times. My objective is to determine whether SODIS is still successful if the recommended 'clear' bottles are scratched and more opaque in appearance. Methods/Materials Nine 2-liter soda bottles were scratched to three levels of opaqueness. Six bottles were left unscratched (3 were controls). An equal amount and concentration of e coli was added to each bottle. The bottles were sealed and placed horizontally in the sun (the control were left in darkness). Samples from each bottle were inoculated onto agar plates, incubated at 37 degrees for 24 hours, and then compared to the controls. Results All levels of scratching (light, medium, and heavy) allowed for the presence of e coli after sun exposure, with the Level 3 (scratchiest bottles) having the highest average number of escherichia coli colonies. Only the clear bottles showed no evidence of e coli growth. The e coli growth was highest for the controls. Conclusions/Discussion There is a direct relationship between the scratchiness of the sun-exposed clear plastic bottles and the presence of e coli. Based on my results, only unscratched clear bottles should be used for SODIS. Further research could possibly reveal whether longer UV exposure might minimize the affects of the bottle opaqueness, especially for the lightly scratched bottles.

Summary statement

My project tests one of the variables present when using the SODIS method to disinfect drinking water.

Help received

I received both the needed supplies and helpful advice from Mr.K. at the Biology Laboratory at Fresno State University. My father helped with digital pictures and my mother helped in coordinating appointments.

Competition history

  • CSEF 2004 Microbiology · Entry J1322

Resources

Related projects

Closest projects by meaning, across every fair and year in the corpus.

Browse more like this

Source: California Science & Engineering Fair public projects

Save projects to your library

Sign in with Google to keep track of projects you find interesting, organized into folders. An account also raises your daily allowance for “Has this been done?”, and lets you create a key for the MCP server with a much higher limit than anonymous use. Browsing stays public.

Continue with Google