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Is Bromate a Concern?

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NaH2O

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Jan 25, 2004
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I was reading an article from Reuters and it made me wonder about bromate in our tanks (for those that use ozone)

Here are a few quotes from the article:

The Coca-Cola Co said on Friday it had recalled its entire Dasani range of bottled water from the British market after levels of bromate, a potentially harmful chemical, were found to exceed legal standards.
"Bromate is a chemical that could cause an increased cancer risk as a result of long-term exposure, although there is no immediate risk to public health," the agency said in a statement.
British limits for bromate, a non-metallic salt, in bottled and tap waters are 10 parts per billion, a Coca-Cola spokesman said, and the Dasani samples had tested at between "borderline" (about 10) and 22 parts per billion. European tap water limits are 25 parts per billion.
Coca-Cola said the bromate was formed during the ozone gas purification process it used in Dasani manufacturing and bottling. To ensure that Dasani meets calcium levels required in all UK bottled water products, it adds calcium chloride, a derivative of bromide. But due to the amount of bromide in the water, the ozonization process caused bromate to form at unacceptable levels, Coca Cola said. Ozonization is a popular process in the bottled water industry, as the ozone gas bubbled through the water kills microorganisms, dissipates quickly and leaves no aftertaste, unlike chlorine treatment.
When we use ozone on our tanks, is the formation of bromate a concern?



For the whole article...here is a link:
http://www.reuters.com/newsArticle.jhtml?type=topNews&storyID=4607526
 

jks1

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Nov 29, 2003
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hmm nikki- not sure on this but think everything toxic with ozone would gas off as our tanks are not closed containers like a bottle. Great read though, like to see if anyone with more expertise chimes in
 

NaH2O

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Well, here is what I was able to discover so far (from a post I found by Boomer). The ozone reacts with Bromide to make oxygen and hypobromite. Hypobromite=bleach. Bromate is BrO3- and is formed when O3 reacts with Br- , but I'm not sure if it is the end product. Maybe it all has to do with concentrations? I'm also not sure how much Br- is present in synthetic salt mixes?

O3 + Br- ----> O2 + OBr-
 

Scooterman

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Gotta see this one, I've read a little about what Boomer posted, also a post from a salt company but maybe a little more info would be a good idea.:lol:
 

NaH2O

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Well, after a failed attempt to find more information....I PMed the big guns, which is Boomer, for some insight. He sent me some awesome information, and I wouldn't do it justice if I interpreted it, so I'll quote:
Bromate requires one further step of oxidaton. Hypobromite can react again with ozone if it is thermodynamically possible to produce Bromate, which is BrO3- (aq)

The level of bromate that may form in water depends on the concentration of bromide in the source water (60 mg / l in seawater, which is very high when comparied to tapwater), the amount of ozone contact time, and a variety of water chemistry factors including pH, organic material, hardness and alkalinity. Ozone reacts directly with the bromide ion to form hypobromite and oxygen.

O3 + Br - 1/2 O2 + OBr -

Two ozone molecules then react directly with the hypobromite to form bromate and oxygen. Alternatively, the hypobromite can react with multiple hydroxyl radicals created by the destruction of ozone.

2O3 (or OH*) + OBr - 1/2 2O2 + BrO3 -

Bromate can also be converted to Bromide ;

BrO3- (aq) + 5 Br- (aq) + 6 H+ (aq) 3 Br2 (aq) + 3 H2O (l)

In seawater with ozone the kinetics just doesn't do much, as there are other things being oxidized, not to mention Iodide @ < 1 mg / l, then there is the chloride ion @ 19,000 mg / l but very, very unfavorable kinetically. The reason behind GAC with ozone is mainly for Hypobromite, but it will also take out Bromate. Finally Bromate is also a function of pH, as pH increases there will be more Bromate.

Also

EFFECTS OF PH AND ALKALINITY ON OZONATION OF BROMIDE AND CHLORIDE IN SEAWATER

A series of laboratory experiments were performed in which unbuffered and buffered solutions of NaBr and NaCl were exhaustively ozonated. The production patterns and relative abundances of the products were compared in order to quantify the roles of pH, carbonate system and borate system in ozone reactions with these two halides in seawater. Concentrations of hypohalites in solutions where pH was buffered in the range 8.6-8.8 were consistently lower than those in the equivalent unbuffered solutions. Bromate production rates in unbuffered NaBr solution, NaBr solution buffered with 3 meq/L carbonate alkalinity, and that buffered with 3 meq/L borate alkalinity were, respectively, 1.30 mM/min, 1.58 ìM/min and 0.83 mM/min.
Our finding that, relative to carbonate alkalinity, borate alkalinity enhances the production of hypobromite while simultaneously depressing bromate formation, may have important consequences for seawater facilities such as aquaria and mariculture that use borate buffers. Hypobromite produced during ozonation in such systems is a desired secondary disinfectant, due to the very short half-life of dissolved ozone in seawater. The use of borate buffers may thus serve to enhance the potential for disinfection while simultaneously diminishing the unwanted bromate accumulation in these environments.
And last, but not least...

I might add that a DSB actually benefits from Bromate to a degree, so with or without GAC and no Ozone there is nothing to worry about. :D

Well, that's the story of Bromate. I don't know about any of you, but I did find this interesting.

THANK YOU BOOMER!!!
 
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