Treatment for Free Bromine/Bromate

Question:

I am the environmental manager for an anodizing/plating job shop. We have been using an iron based de-ox for aluminum for years and are looking to replace it with something that is less of a pain in the neck. One supplier has a sodium bromate/nitric acid de-ox. Their tech data sheet mentions using sodium bisulfite to destroy free bromine/bromate in the wastewater. Can you point me to any resources that deal with treatment of bromine/bromate? I need specifics about how to measure and control the treatment (pH, ORP, ion-specific, etc.) and any alternative treatment methods. Thanks for your help. G.L.

Answer:

One of my first questions to you is why do you need to pretreat for bromine/bromate?

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If you have an indirect discharge to a sewer, there is very likely no specific discharge limit. If you have a direct discharge to surface waters, while there is likely no specific discharge limit, these compounds could adversely impact biological toxicity testing.

Despite my efforts in reviewing accessible materials, as well as discussing this with several water treatment experts, I was unable to discover any specifics regarding your question. There is agreement that sodium bisulfite, a reducing agent, can remove the oxidizing characteristics of bromine and bromate, converting them to a bromide; however, we do not know of the specific chemical environment in which the reaction would rapidly occur. If a reader does know the conditions under which the reduction of bromine/bromate occurs, please respond.