What is a chlorine retention test?

[ziptron]

Hi All,

A new water main is being put into a subdivision and a chlorine retention test will be performed apparently. I cannot seem to find a good idea of what this test is all about. Can someone point me in the right direction so I can understand what will be performed?

Thanks in advance!

 

[ziptron]

The test may also be called the "residual chlorine test" but I am miss hearing it.

 

[bimr]

There is a disinfection procedure, AWWA C651 for new water mains. Attached is the basic procedure.

 

[ziptron]

Thank you for your link... this is similar to what I was finding but somehow I can't make sense of it.

It seems the concern is that the chlorine level will decrease over time. Why would the chlorine level decrease over time?

Corrosion of the water main? (in my case its copper)

 

[coloeng]

The purpose of chlorinating the new pipeline is to inactivate (kill) any bacteria that may be in the pipeline. That is why you typically see a high initial dose and then want to see it no less than 25 ppm at the end of the test. Organic matter that is in the pipeline (dirt, leaves, dead animals, etc.) will take up the chlorine and decrease it over time. That is why you want to see a minimum residual so that you know that all the chlorine that is going to be taken up has been. If the chlorine residual is less than the minimum residual, you may need to rechlorinate. Hope that makes sense.

 

[bimr]

When chlorine is added to water, a variety of chemical processes take place. The chlorine reacts with compounds in the water and with the water itself. Some of the results of these reactions (known as the chlorine residual) are able to kill microorganisms in the water.

Adequate disinfection is actually confirmed when two water samples taken twenty four apart indicate no bacterial contamination.

 

[ziptron]

Thanks to both Coloeng and Bimr!

I did some further research based on your comments and it all seems to make sense now.

Thanks again!