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Introduction

Previously, there were only two ways to disinfect a spa with bromine. The first was to use tablets comprised of 1- bromo-3-chloro-5,5-dimethylhydantoin (BCDMH). The second was to employ a two-step system using sodium bromide and potassium monopersulfate (the active constituent in BioGuard Oxy-Sheen). Now there is a third,SpaGuard Brominating Concentrate - a unique, one-step granular product that simplifies the sanitation of spas and hot tubs. This Technical Information Bulletin explains what Brominating Concentrate is and how it can be used in spas.

Chemistry

In the traditional one-step system using bromine tablets, BCDMH dissociates in water, producing both hypobromous and hypochlorous acids:

 


In the two-step system employed primarily in the USA and Canada,(1) sodium bromide is added to a spa to create a bromide "bank". Potassium monopersulfate (KHSO5) is then added to the water as an oxidiser, spontaneously converting the bromide to hypobromous acid:

HSO5¯ + Br¯ + H+ HSO4¯ + HOBrHSO4¯ + HOBr

Brominating Concentrate takes a similar approach, but incorporates sodium bromide with the highly soluble sodium dichloroisocyanurate (dichlor) in place of monopersulfate in an easy-to-use one-pack product:


In all three systems, the hypobromous acid interacts with bacteria, algae and dissolved organic species to regenerate the bromide ion:

HOBr + Bacteria Br¯ + Dead Bacteria
HOBr + Algae Br¯ + Dead Algae
HOBr + Organics Br¯ + Oxidised Organics

Advantages

There are several important advantages in using this product instead of bromine tablets or other conventional spa sanitation methods :
1. Brominating Concentrate is extremely soluble, dissolving almost instantly in water without any cloudy residue.
2. Unlike bromine tablets or lithium hypochlorite, Brominating Concentrate has a neutral pH so there is less need to worry about the depletion of total alkalinity (TA), the adjustment of pH, the irritation of skin and eyes arising from pH fluctuations and the placement of feeders.
3. Brominating Concentrate is a granular product so it can be easily measured and hand-fed for both regular sanitation and routine shocking. No feeders are necessary.
4. Although Brominating Concentrate is a primary sanitiser, it can also be used as a shocking agent or a supplement to other sanitation products, like SpaGuard Bromine Tablets.

Application

For regular daily maintenance, 6 to 10 grams of Brominating Concentrate added to 1,000 litres should give a 2 - 4 ppm bromine residual. For initial start-up or excessive bather load, 6 to 10 grams per 1,000 litres should be added every 15 minutes to the circulating water until a residual of 2 - 4 ppm is maintained. Regular testing using DPD No. 1 tablets is required to determine the frequency of the treatment. For shocking, 25 grams of Brominating Concentrate per 1,000 litres is recommended. If bather load is heavy, shocking may be required daily, whilst moderate use will normally require a weekly shock treatment. Bathers should not re-enter the spa until the bromine residual falls below 6 ppm. 

As with any spa sanitiser, the water must be regularly tested and properly balanced for optimum water cleanliness and clarity. Regular draining and cleaning of the spa and filter system will allow the bromine to be more effective against bacteria, body wastes and other contaminants that can cloud the water and make it both unappealing and unsafe to bath in.

References

1. Diane S. Rennell (ed.), "Basic Pool and Spa Technology", 2nd edition, National Spa & Pool Institute, Alexandria VA, 1992, pp. 309-310.

The above information is supplied by Bio-Lab and represents its best interpretation of available technical information at the time of preparation. The sole purpose is to supply factual information to Bio-Lab customers. It is not to be taken out of context nor used as support for any other claim not made herein.