Mehrnaz: 

Interesting question, there are at least three ways that aeration could impact disinfected water.  The concentration of volatile and semi-volatile organic compounds would be reduced, aeration would also purge dissolved CO2 reducing the carbonate/ bicarbonate levels and likewise aeration could reduce the OCl--concentration by perturbing the equilibrium constants below.

OCl- Vapor pressure at 25 °C =  5,830 mm Hg

Henry's law constant = 1.17x10-2 atm-m3 /mol

The outcome will not be simple or easily predictable, however, because of the number of variables that would be changing simultaneously.

. Purging the organics will reduce the chlorine demand.

. Purging / adding CO2 could change pH +/_ 

. Aerationwill reduce concentration and/or change chlorine equilibrium constants

Thank you Steve,

Agree with the points you brought up; regarding OCl-, doesn't its level increase by aeration? (increasing pH will switch more to OCl- rather than HOCl?)

can we conclude that by post aeration of chlorinated water, we may have the same level of Cl residual but with low efficiency of disinfection in distribution system?

Dr. Sadrnourmohamadi could you provide a reference to a study reporting this.

Aeration after chlorination would purge THMs as they are semi volatile.

Hi Henrik,

some references available confirming THMs removal up to 99% (mainly chloroform): https://www.awwa.org/publications/journal-awwa/abstract/articleid/28962.aspx

there is another ongoing study being done by U of Toronto, Dr Hofmann research group, showing that aeration can cause chloroform removal up to 99% however those DBPs that are potentially the most toxic are among the least volatile and therefore aeration cannot do anything for them.

https://www.owwa.ca/wp-content/uploads/2014/06/4.-Concerns-with-Aeration-to-Remove-THMs-Extended-Abstract.pdf

Mehrnaz