- Samples of source water are taken prior to the treatment process on a daily basis.
- The samples are then placed in containers, such as petri dishes or pouches with numerous tiny capsules, along with “media,” a substance that acts like food for the bacteria.
- The samples are then left to incubate for approximately 24 hours.
- During this time, a bacterium can multiply from one to millions, making a colony that can be seen by the human eye in the culture plate.
The laboratory tests specifically for Coliform bacteria. Coliforms can be counted on a grid in the petri dish. E. Coli is grown in pouches with wells of medium. When placed under an ultraviolet light, the E. coli flouresces to a blue color indicating how many are present.
These tests are done before treatment and are indicators of the absence or presence of potential contamination in the water sample. All new water mains are tested for bacteria and must be free of all harmful bacteria before they are put into use.
The lime treatment process used by Des Moines Water Works kills 99.9 percent of bacteria and a chlorine additive eliminates anything that might be left, ensuring that your tap water is Water You Can Trust for Life.