Because of the oxidation reactions that are taking place during the sterilization period some of the chlorine will be consumed but the amount of chlorine dosed will be enough to ensure that there will always be at least a 5 ppm residual at the end of the sterilization period.
The residual free chlorine and the majority of the organic molecules will be removed from the sterilized water prior to use by absorption on activated carbon.
The activated carbon will be housed in a pressure filter which is similar in construction and arrangement to the sand filter.
The activated carbon will be supported in the filter on a bed of graded gravel and the volume for carbon will be calculated to a give a contact time of five minutes with the water.
This contact time will be long enough to remove all the free chlorine from the water.
Activated carbon will also remove other organic molecules that remain in the water after the coagulation reaction or are formed as part o the sterilization reactions.
A five minute contact time may be enough to remove not only the free chlorine but also a majority of the taste and odor forming organic molecules.
Some residual organic compounds may however, remain in the water because the contact time with activated carbon necessary for their total removal will be longer than five minutes.
In general, the organic residual is expected to be below the detection threshold with only a short contact time.
Softdrinks Processing – Dechlorination of Water
