The Sterilization Effect of Solar Energy and Its Application

1. Purpose of the Study

Knowing that solar energy can disinfect water, I wanted to find out the minimum intensity and exposure time of ultraviolet (UV) light needed for effective sterilization. To better understand the efficiency of solar disinfection, I planned to conduct detailed experiments using UV rays at different wavelengths. Additionally, I’d like to explore ways to improve existing technologies, like the Solvatten system, to make them more effective if possible.

2. Research Details

A. Background

Ultraviolet (UV) light from the sun is harmful to the human body, but UV-C, with wavelengths between 100 and 280 nm, is the strongest form of UV radiation. However, it is completely absorbed by the ozone layer and does not reach the Earth's surface. UV-C, especially at 265 nm, has the highest sterilization effect because it destroys DNA. In comparison, UV-A and UV-B have significantly different sterilization times and effectiveness, making them less suitable for widespread use.

B. Method

Research 1: What wavelength of ultraviolet (UV) light is needed to have a sterilizing effect?

Research 2: How long must UV light be applied for effective sterilization?

Research 3: Does the sterilizing power of UV light differ depending on the type of container holding the contaminated water?

C. Procedures

Research 1: Shine UV-A, UV-B, and UV-C lamps on tap water, rainwater, and Han River water for 4 hours, and record the TDS (Total Dissolved Solids) levels.

Research 2: Shine a UV-C lamp on Han River water, measure and record the change in TDS levels every hour.

Research 3: Shine a UV-C lamp on contaminated water in different containers, and measure and record the change in TDS levels every hour.

3. Result

When UV-A, UV-B, and UV-C were applied to contaminated water, UV-C near 260 nm showed the highest sterilization effect. In the experiment examining the effect of exposure time on sterilization, water quality improved consistently from the beginning up to 4 hours.

Therefore, it was concluded that water can be sterilized by exposing it to UV-C light for 4 hours. Additionally, in an experiment comparing the sterilization power of UV light based on the type of container, brown glass bottles were found to have the best sterilization effect.

Based on these results, when designing a solar-powered water sterilizer using appropriate technology, it would be beneficial to use brown glass containers and equip the device with UV-C lamps to ensure sterilization for over 4 hours, regardless of weather conditions.