Section 604.905  Carbon Dioxide Addition

a)         Unless carbon dioxide addition is provided in the form of a carbonic acid and water solution under pressure, recarbonation basin design must provide:

1)         a total detention time of 20 minutes; and

2)         a depth that will provide a diffuser submergence of not less than 7.5 feet nor greater submergence than recommended by the manufacturer.

b)         When liquid carbon dioxide is used, carbon dioxide must be prevented from entering the atmosphere within the plant from the recarbonation process. 

c)         Recarbonation tanks must be located outside or be sealed and vented to the outside with adequate seals and adequate purge flow of air.

d)         The recarbonation basin must be designed to allow for draining and sludge removal.