Fresh water is treated to make it safe to drink. Soluble and insoluble

substances are removed during this treatment, and chlorine is added

to kill harmful microorganisms. State two reasons why samples of the

treated water are tested regularly.

Reasons:

To ensure the presence of residual chlorine. To detect or measure the amount of coliform bacteria.

Explanation:

Chlorination of drinking water is the last step of the water treatment process. It is a disinfection step that eliminates pathogens.

Free Chlorine

During chlorination, the amount of chlorine is strictly controlled to ensure that some residual or free chlorine is left after it has killed all microorganisms. This free chlorine makes sure that the water remains pathogen free in the entire water supply or until it is consumed. Drinking water is regularly tested to ensure the presence of this free chlorine. Its presence indicates that the water is safe to drink.

Coliform Bacteria

Supply water is also tested to measure coliform bacteria. Some coliforms cause diseases whereas others are harmless; but the presence of coliforms is a sign of potential contamination by other pathogenic bacteria.