Question

checkeing the bacterial contamination in drinking water by testing sulphide ion its project

Answer 1

Ans - The presence of pathogenic bacteria in drinking water is due to human or animal waste contaminating the water source. These can lead to various gastro-intestinal diseases such as typhoid, cholera. It is difficult & expensive to test for these disease causing bacteria routinely in a water source. Hence, the tests are carried out for the presence of indicator organisms, which are always present in faeces in large numbers.

Their presence shows that drinking water can also have pathogenic bacteria. One group of such indicator organisms are sulphide producing bacteria. These bacteria are present in faeces and their presence indicates that drinking water may have pathogens also.

The principle of this test is the reduction of the sulphate (which is a component of the growth medium) to sulphide by sulphide forming bacteria and the reaction of sulphide with iron to form iron sulphide, which is insoluble and black in colour. The formation of black colour is taken as an indication of bacterial contamination of drinking water.