Download Chlorine and bromine

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The elements chlorine and bromine in swimming pool
Chlorine
Chlorine is a poisonous element from the halogen group of chemicals. It has a very high
potential to cause death or injury when not handled properly. It is available mostly in compound
form in gaseous, liquid and solid forms. However, the chemical is in formulated compound
forms that are safe to use in swimming pools for disinfection purposes ("WATER
CHEMISTRY FOR
SWIMMING POOLS").
Using Chlorine for disinfection reasons is known as chlorination. It is currently the most
commonly used method of swimming pool sanitation. Introducing chlorine into the water forms
hypochlorite ions (OCl-) and hypochlorous acid (HOCl), whether introduced in liquid, gas or the
dry compound form.
Cl2 (aq) + 2H2 O to give HOCl(aq) + Cl-(aq) + H2O
Hypochlorous acid is the active ingredient that destroys harmful living organisms in the
water such as algae, fungi, bacteria, and viruses. It readily dissociates into hydrogen and
hypochlorite ions.
2H2O + HOCl(aq) to give H3O + (aq) + OCl- (aq)
The H3O+ ions bring the pH of the water into balance, while the OCl -and HOCl act on
the cell walls of the pathogens and other organic materials to destroy them (Puetz).
Disinfection happens in two ways as follows.
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The chlorine compound kills organisms that are pathogenic to users of the swimming
pool, in a sanitation process. Standardized chlorine is used to eliminate the different types of
harmful organisms which require different doses.
The second process is oxidation where the compound reacts with the suspended organic
materials in a process like burning to destroy the unwanted materials in the water ("WATER
CHEMISTRY FOR SWIMMING POOLS").
OCl- and HOCl are readily rendered unsterile on ultraviolet light into 2Cl-, 2HCl, and
O2. Other chemicals such as the cyanuric acid are used in combination to reduce the
photochemical decomposition of the free chloride ions.
Bromine
Bromine, also a halogen, is highly toxic and is available in liquid form in nature. It occurs
in stable compound formulated for pool treatment.
The bromine introduced into the water gets its activity ignited by the addition of an
oxidizer in a two-part sanitization system or in a one part system where the dispenser contains
both the bromine and the oxidizer which eroded through a feeder (Pool)
In the presence of an oxidizer in the swimming pool, bromine is activated to break down
into hypobromous acid (HOBR) and the hypobromite ions (OBr) responsible for the reactions
that destruct the organic forms in the water. The responses of the bromine introduced are in the
similar process just like the chlorine element. However, instead, it combines with the organic
impurities to form bromamides or combined bromines.
Br2+H20 to give HOBr+H'+BrThe HOBr further dissociates to result in H++OBr-
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The hypobromous acid in combination with the hypobromite oxides acts on the organic
matter in the pool killing pathogens in the process.
Chlorine and bromine
Chlorine more actively reacts in the swimming pool compared to bromine. However, its activity
does not continue for long after reacting with nitrogenous or ammonia compounds while
bromine will stay active as a sanitizer. Unlike Bromine, chlorine often requires shocking to
remove accumulating chloramines a process that uses more than a third of the average amount of
chlorine (Pool). Chloramines are smelly and irritating to the eyes. Building levels of bromamides
are still sanitizers, not smelly and not irritating.
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Works Cited
Pool, Charles L. "Swimming Bath Water Purification (2d ed.)." American Journal of Public
Health and the Nations Health, vol. 25, no. 4, 1935, pp. 510-510.
Puetz, John D. "The Care and Treatment of Swimming Pool Water." Swimming Pool Water
Cchemistry , Arch Chemicals, Inc., now a part of Lonza,
"WATER CHEMISTRY FOR SWIMMING POOLS." Welcome to Flasolar.com ... SOLAR IN
THE SUNSHINE STATE Information on Solar Pool Heating , Solar Water Heating and
Solar Energy, www.flasolar.com/pdf/water_chemistry_for_swimming_pools.htm.