Chemical Equilibrium in swimming pools

Chemical Equilibrium in swimming pools

Abstract

Swimming pools are constantly used by many people for events such as, sporting, recreational and normal activities in water. But it's keeping the water at a constant PH level that maintains a sterile environment that controls the growth of micro organisms, and helps prevent disease outbreak so that the users are kept happy, healthy and free of sickness. Having swimmer's use the pools and disturb the equilibrium due to sweat, oils etc combining with water, the use of chlorine or bromine is necessary to keep the pool up to health and safety regulation standards. The testing of the element bromine and analysis of properties and values, compared to that of chorine, may provide understanding on the physical and chemical backgrounds, and qualities behind both forms of sterilization.

It was found that the liberation of bromine from naturally occurring bromide produced a formation of bromamine and chloramine due to being in the presence of ammonia and nitrogenous matter found in bathing loads. Bromine shares the characteristic of chlorine combining with swimmer and wastes such as urine, sweat, body oil, etc thus forming the chemical compounds discussed above.

Through the investigation of the bactericidal effect of bromamine and chloramine, the action of the element bromine was regarded as having similar qualities to that of chlorine. But differences include bromamines having no troublesome side effects of eye complaints and smell around swimming pools. This is the chlorine chemicals interacting with human waste products such as oils, sweat etc. This then causes the formation of chloramines, which then produces the side effects mention previously.

Although when bromine combines with contaminants in the water and forms combined bromine (bromamines). The advantage of the bromine chemical is that this form, combined bromine, and is also an efficient sterilizer. This means that combined bromine can also eradicate bacteria. This is an advantage that distinguishes bromine from chlorine. While the same chemical reactions happen with chlorine, the combined form of chlorine (chloramines) is not nearly as effective a sanitizer.

Concluding that using bromine could make it more economical then chloride due to the similar and equal properties of sterilization and bromide rarely having the side effects of the formation of chloramines and the consequence of eye irritation and strong chemical smells.

Explanation of Chemistry involved

Investigation on bromide includes the outline of bactericidal effects, analytical chemistry involved and the reaction of free and combined bromine in nitrogenous matter and ammonia compared to that of chlorine in swimming pools.

During chlorination of seawater in pool it is found that the liberation (to set free) of bromine from naturally occurring bromide that is normally present to the extent of 70ppm (parts per million) causes the formation of bromamines and chloramines in the presence of ammonia and nitrogenous matter.

The formation of chloramines, combined bromine and bromamines in due to the chemical compounds formed by chlorine and bromine combining with swimmer wastes such as sweat, urine, body oil, etc. Chloramines are non-effective as a disinfectant and will cause eye and skin irritation,

Although when bromine combines with contaminants in the water and forms combined bromine (bromamines). The advantage of the bromine chemical is that this form, combined bromine, and is also an efficient sterilizer. This means that combined bromine can also eradicate bacteria. This is an advantage that distinguishes bromine from chlorine. While the same chemical reactions happen with chlorine, the combined form of chlorine (chloramines) is not nearly as effective a sanitizer.

Chemical behaviour of combined bromine includes, bromine in water hydrolyzes according to the equation Br2+H20 = HOBr+H++Br- for which the equilibrium is constant at 5.8x10-9. Further HOBr = H++OBr- according the pH and molecular bromine will form perbromides of formulas Br3- and Br5- with equilibrium constants 16.0 and 40.0 respectively. At pH levels and concentrations of bromine in pools, the main entitles involved are Hypobromous acid and hypobromite. Proportions depending on the pH level of the bathing load and also to a lesser extent the ionic strength of the solution. Hypobromous and hypobromite acid are strong oxidizing agents. The Hypobromous acid is the active form of bromine responsible for killing bacteria, algae and pathogenic organisms.

Hypobromous acid is an excellent sanitizer with a reduced dependence on pH as compared to hypochlorous acid (HOCl). HOBr is a weaker acid than HOCl and therefore does not dissociate as easily. What this means is that at a similar pH, there is more HOBr than HOCl as illustrated by the chart below. HOBr is more effective at killing microorganisms than OBr-. This reduced dependence on pH makes bromine an excellent choice for spa sanitation as the pH in spas tends to drift up due to the loss of carbonic acid with aeration.

Another aspect of bromine chemistry that makes it unique is the ability to regenerate the bromide ion. When hypobromous acid reacts with microorganisms or organics, it is “used up” and the bromide ion (Br-) is left.

Thus urea is oxidized with the formation of bromamines as intermediate products. Amino acids are also attacked to form initially N-Br compounds and finally keto-acids. Aromatic amino acids are also attacked in the nucleus with subsequent reaction of hypobromite and the amino nitrogen. Hypobromite may hydrolyse (get smaller) further to form bromate by the reaction 3.0Br- à BrO3- and this bromate may accumulate in water of swimming pools.

Chemical Reactions

Monobromamine is a strong oxidising agent due to the presence of the monobromammonium ion, which will tend to react by the release of a positively charged bromine atom.

NH3Br+ à NH3+Br+

Having strong oxidizing properties provides explanations for reaction of bromamine with dimethylamine to give N-bromodimethylamine and monobromamine.

Similarly to free and combined chlorine, bromine and its compounds give rise to currents in amperometric apparatus and this may be used for their detection and estimation.

Characteristics with chlorination reacting with water containing ammonia produces a reaction called break point. One characteristic of chlorination of water containing ammonia is the formation of the break point. Bromine exhibits similar behaviour. A breakpoint is reached where no ammonia or monochloramine is left in the solution and no free available chlorine is present. Adding chlorine to exceed the breakpoint is called breakpoint chlorination. The Break Point Chlorination - If the water to be chlorinated contains significant amounts of ammonia the amount of chlorine added will be sufficient only to form monochloramine. Further addition of chlorine may lead to formation of di-or tri-chloramines. But maintaining the chlorine to nitrogen ratio very low can prevent their formation.

Bromine has been found to exhibit a typical break point reaction, occurring exactly at an equivalence point to which the oxidization of ammonia is complete.

There are however differences between chlorine and bromine. Bromine does not appear to form in (aq) solutions and bromamines and bromine cannot co-exist other than momentarily at the pH of swimming pools.

Bactericidal Actions

Germicidal tests were conducted in tap water containing soil bacteria. Chlorine and bromine were tested and consequently, they found that at low concentrations of the free halogens bromine was a more efficient germicidal agent than chlorine. This was also produced when the investigation on spore forming bacteria was conducted on vegetables...

Question 1

Why does they use bromine and chlorine in swimming pools? Justify your answer and use chemical terms.

Question 2

What are the differences between the break point phenomena test conducted between Brook and Houghton and what did both of them find out?

 

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