Can Ultraviolet Light Purify?

Overview

Objectives/Goals The objective of this project is to see if ultraviolet light will reduce the bacterial count in a useable water source making it acceptable to drink. Methods/Materials A sample of clear water was obtained from the Kern River. A portion of it was poured in a clear plastic PET bottle and placed under a 100 watt ultraviolet light for disinfection. Samples were taken for bacterial culture at 24, 48, 72, and 96 hours. Controls of boiled Kern River water, Arrowhead bottled water, tap water, and untreated Kern River water were also taken. They were checked for bacterial growth at 24, 48, 72, and 96 hours. Results The results showed that it took 72 hours under the 100 watt ultraviolet light to decrease the amount of bacteria in the useable water source to an acceptable level and 96 hours to reduce it further. Conclusions/Discussion The bacterial count in the water source was reduced over seventy-two hours of exposure to the ultraviolet light. The amount of time required in the lab setting is prolonged due to the limits of the 100-watt ultraviolet light bulb and the limited heat that it produced. This shows that sun light would reduce the bacterial count in the useable water source at a faster rate because both the higher intensity ultraviolet light and the heat produced by the sun would increase the rate of bacterial death.

Competition history

• CSEF 2010 Microbiology · Entry J1701

Resources

• CSEF project summary ↗

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