Classed as a category 2 CMR since November 2022, sodium bromide (NaBr) will, where possible, have to make way for new forms of treatment chains in industry. What are the risks involved? What alternatives are there? What are the consequences for industrial water treatment strategies?

 

Sodium bromide: reprotoxicity and environmental footprint

Since the 1970s, sodium bromide has played an important role in biocidal treatment chains: its addition enhances the effectiveness of chlorinated biocides in water that is too alkaline (pH>8). Now considered to be a 'suspected' reprotoxicant (CMR category 2), sodium bromide could rapidly become a 'proven' reprotoxicant (CMR category 1) under European harmonisation.

 

The consequence for manufacturers is that, as of today, they must launch a project to assess the possibilities of substitution, in order to comply with the obligations of the Labour Code common to the general obligations on hazardous chemical products. The aim is to protect their employees in the short, medium and long term.

 

More broadly, the replacement of sodium bromide needs to be considered from an environmental point of view: mainly found in Asia, the Middle East and America, the extraction, concentration and transport of bromine are highly polluting. And the long-term consequences of bromine discharges into ecosystems from which it was originally absent are unknown.

 

From sodium bromide to salt electrolysis and UV treatment

But there’s no need to panic about the CMR classification of sodium bromide! There are several alternatives for disinfecting water in industrial processes.

 

  • Salt electrolysis, or to be more precise, the on-site production of a fresh disinfectant solution obtained by electrolysis, using only water, salt and electricity. Synonymous with less transport (salt only) and no handling of chemicals by staff, the chlorinated disinfectant solution obtained by salt electrolysis is unclassified for health and the environment. But it's also ultra-efficient, because it doesn't contain any stabilisers - it's made to order according to the precise needs of the systems and injected immediately.
  • A mixed UV-C treatment, with hydrogen peroxide added under certain conditions, is also a possible alternative to the addition of sodium bromide. However, the space required for its implementation can be restrictive, depending on the industrial installations concerned.

 

Envisioning tomorrow's industrial water treatment strategies today

To comply with the CMR classification of sodium bromide, manufacturers can also review their treatment processes in a more comprehensive way. Certain pre-treatments can be used to limit the alkalinity of the water, thereby guaranteeing the biocidal effectiveness of chlorine solutions. This is the case, for example, with

  • pre-treatment by reverse osmosis;
  • acid decarbonation of the water.

 

In the longer term, sodium bromide, now classed as a CMR, could be the first in a long series of bromine-based substances, some of which are also widely used in industry.

 

So manufacturers need to start thinking now about how their treatment lines might evolve, and develop new water treatment strategies that are more respectful of both the environment and health, as part of a methodical risk analysis (MRA) that takes account of these potential future externalities.

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