Germicidal Properties of Copper / Silver or similar Agent
Idea
Copper and silver ions are germicidal (able to kill germs). Metal sheets made out of copper and silver could be used to make water safe for drinking. It is therefore necessary to determine the surface area of the metal to be used to treat a fixed amount of water as well as the time the water needs to be in contact with the metal surface.
Objective
To use copper and silver sheets to reduce pathogens in water.
Materials Required
Thin sheets of copper / silver of different sizes / surface areas, e.g. 8*8 cm and 0.5 mm thick.
1. Glass containers / stainless steel containers of 1 litre capacity.
2. Known culture of bacteria (bottle of contaminated water which turns black in H2S media)
3. Required number of H2S bottles as described in previous experiments or from commercial source.
4. Boiled water / commercial packaged or bottled water.
Methodology
Take boiled and cooled / commercial packaged or bottled water in a glass container and add a drop of known culture of H2S bacteria and suspend the metal sheets in it. Use acid treated metal also. At an interval of two hours, take the water sample to test for any living H2S bacteria. Observe how long it takes to kill the bacteria.
Interpretation
Determine the size of the metal required to make the given volume of water germ free, in a given time period (three variables-volume of water, surface area of Cu / Ag dipped, time).
Precaution
1. Note that bacterial load should be as low as possible after the observation time to conduct the experiment.
2. Dispose off the bottles as described earlier.
Source: Harness water resources for a better future - Activity Guide for the 13th National Children's Science Congress