Chemistry project on checking the bacterial contamination in drinking water
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Bacterial contamination in water is tested by performing the Sulphide test.
Organic compounds that contain sulphur are usually present in water. When these are decomposed by the bacteria present in the water, Hydrogen sulphide is formed. This usually occurs under oxygen-deficient conditions.
Hydrogen sulphide is a weak acid which gets ionized to form Sulphide ions (S₂) and hydrosulphide ions (HS⁻). Even a concentration of less than 0.01 mg/L of sulphide ions makes them unfit for consumption or even for fish cultures.
A simple method to check the presence of sulphide ions is to fill the water to be tested in a bottle which has a H₂S strip. The bottle is kept in an incubator for 14 - 16 hours at 35°C. If the strip turns black, then it means that the water is contaminated and is not suitable for consumption. The black colour is due t the formation of Iron by reaction of the iron with the sulphide ions formed by sulphide-converting bacteria.
Organic compounds that contain sulphur are usually present in water. When these are decomposed by the bacteria present in the water, Hydrogen sulphide is formed. This usually occurs under oxygen-deficient conditions.
Hydrogen sulphide is a weak acid which gets ionized to form Sulphide ions (S₂) and hydrosulphide ions (HS⁻). Even a concentration of less than 0.01 mg/L of sulphide ions makes them unfit for consumption or even for fish cultures.
A simple method to check the presence of sulphide ions is to fill the water to be tested in a bottle which has a H₂S strip. The bottle is kept in an incubator for 14 - 16 hours at 35°C. If the strip turns black, then it means that the water is contaminated and is not suitable for consumption. The black colour is due t the formation of Iron by reaction of the iron with the sulphide ions formed by sulphide-converting bacteria.
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