Softdrinks Processing: Sterilization of Water

Softdrinks Processing: Sterilization of Water
Free chlorine will be used as the sterilization agent for the water prior to its use in the manufacture of the softdrinks. It is usual to use about 10 ppm of free chlorine for sterilization to ensure that the reaction will reach completion.

Free chlorine may be dosed as chlorine gas but it is usually prepared from sodium hypochlorite solution for safety reasons. In the case where ferrous iron salts are used as the coagulation chemical, free chlorine will be used to oxidize the ferrous salt to ferric salt.

It is usual in this case to dose more than 10 ppm free chlorine into the coagulation tank so the ferrous iron is fully oxidized to the ferric state and so that there is the required excess for sterilization. Where ferric iron is used as the flocculating chemical the residence time in coagulation tank can be included as part of the contact time necessary with free chlorine for sterilization.

In this case the chlorinated water storage tank can be smaller. Free chlorine will not be used as part of the coagulation reactions where aluminum sulphate is used as the flocculating chemical and will generally be dosed after the sand filter, though in some cases chlorine may be dosed into the clarifier to prevent bacterial growth.

Approximately 10 ppm of free chlorine will be dosed into water for sterilization. The reactions that take place will not only destroy bacteria that may be in the water and render it sterile but will also react with other organic molecules that may remain in the water after the clarification reactions.

The residual organics may wary from naturally occurring organic matter to simple organic compounds such as chlorophenols and trihalomethanes that could impart both taste and odor to the final carbonated product. The action of the free chlorine will break down these organic molecules.
Softdrinks Processing: Sterilization of Water