By adding 2% KI solution you can stop the reaction.

Mr. ashutosh, Thanks. But KI will not hamper in the further analysis??

You may consider using reducing agents such as sodium bisulfite, sodium thiosulfate, calcium thiosulfate, etc. This is, often, the most cost effective option. Other options will include using hydrogen peroxide or activated carbon. It is also dependent on your water quality objectives after chemical addition for ozone quenching.

The proposed and more frequenty used method is KI iodometric method. The KI further effect will be disminuished by the other compounds added. Inside the protocol is everything expained with details.

Of course, all this above is valid considering the ozone concentration is between 0.1 and 200 g/m3 of water.

Thanks Alexandros.