Posted via email from good pool stuff

Posted via email from good pool stuff

The 850-acre L-shaped island belonged to “Joe” Carstairs, heiress of the Standard Oil fortune, and was visited by the Duke and Duchess of Windsor in the Forties. There are historic buildings (Great house, lighthouse, and church), rare flora and fauna and watersports and diving. But what makes it such a rare and valuable opportunity, according to Giles Gale of estate agency Savills, is the private paved airstrip. “It is unlikely that permission would be granted for the creation of a new airstrip these days,” he says.
 
It was bought in the Nineties by a family-owned Bahamian registered corporation, which has spent the past decade buying back plots of land that were sold off by the Carstairs family in the Seventies. The island is sold with outline planning consent to develop the land into a luxury private island resort, with commercially operated airstrip, marina, hotel and resort homes.

The new owner will have full control of the island and own 94 per cent of the land – although there may also be the possibility to purchase smaller parcels of land or the whole thing. “It would make a fantastic Necker-style private retreat but could also be a resort with residences. The key is accessibility – the island is a 50-minute flight from Florida and 10 minutes from Nassau,” says Gale.

Since appearing on the market privately last week, there has been a flurry of interest in Great Whale Cay, he says. “$80 million is actually quite cheap on an acre basis,” he says. Last year the 350-acre Bell Island, also in the Berry Islands, sold for $70 million.

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Pool smell is due, not to chlorine, but to chloramines, chemical compounds that build up in pool water when it is improperly treated.

Chloramines result from the combination of two ingredients:  (a) chlorine disinfectants and (b) perspiration, oils and urine that enter pools on the bodies of swimmers. Chlorine disinfectants are added to pool water to destroy germs that can give swimmers diarrhea, ear aches and athlete’s foot. Perspiration, oils and urine, however, are unwanted additions to pool water. By showering before entering the pool, and washing these substances from the skin, swimmers can help minimize pool smell.

The Chemistry of Pool Smell

When chlorine disinfectants are added to water, two chemicals are unleashed that destroy waterborne germs:  hypochlorous acid, HOCl, and hypochlorite ionchildren in pool, OCl-. A measure of the chlorine in these two chemicals is known as “free available chlorine” or FAC.  Pool operators manage the FAC level of pool water for the safety of swimmers. Their challenge comes from the fact that FAC is reduced when it reacts with perspiration, oils and urine from swimmers to form chloramines.

One way that chloramines are formed in pool water is by the reaction of hypochlorous acid with ammonia. Ammonia, NH3, is a component of sweat and urine. Its chemical structure is illustrated in the figure at the right.

There are three chemical reactions that can occur when hypochlorous acid reacts with ammonia, each involving the replacement of hydrogen ions with chlorine ions. When one of ammonia’s hydrogen ions is replaced with chlorine, monochloramine is formed:

HOCl  +  NH3   →   NH2Cl  +  H2O

Three hydrogen ions are found at the corners of the base of this pyramid-shaped molecule, with nitrogen at the top.

Replacing one more hydrogen ion with chlorine produces dichloramine,

HOCl  +  NH2Cl   →   NHCl2  +  H2O

Finally, it is possible to replace all three of ammonia’s hydrogen ions with chlorine to form trichloramine, also known as nitrogen trichloride:

HOCl  +  NHCl2   →   NCl3  +  H2O.

Monochloramine is sometimes intentionally added to water because it is actually a useful disinfectant. Drinking water, for example, is sometimes purified with monochloramine. Dichloramine and especially trichloramine are the chloramines most responsible for pool smell. By showering before entering the pool, swimmers can minimize the formation of these two chloramines.

Managing Chlorine in the Pool

As hypochlorous acid combines with ammonia to form chloramines, the FAC of pool water is reduced. Lowering the FAC reduces the ability of chlorine to destroy germs. The amount of chlorine that is “tied up” in chloramine compounds, and is therefore unavailable as free chlorine, is known as combined available chlorine (CAC).  The sum of FAC and CAC is the total chlorine (TC).

TC = FAC  +  CAC

The Association of Pool and Spa Professionals suggests FAC concentrations in pool water should remain in the range 1.0 – NC 4.0 parts per million for chlorine to work effectively (FAC should never fall below 1 part per million). CAC levels should be less than 0.2 parts per million.

Pool managers can use test kits to measure both FAC and TC. CAC is then simply calculated:

CAC = TC – FAC

Minimizing Pool Smell

Swimmers with reddened, irritated eyes have been known to complain that “there is too much chlorine in the pool”. In fact, however, when pool water is irritating, there is not enough chlorine in swimming pool water!

You may be surprised to learn that there is no odor to a well-managed pool. Chloramines, which produce pool smell, can be eliminated using chlorine. “Shock treatment” or “superchlorination” is the practice of adding extra chlorine to pools to destroy ammonia and the organic compounds that combine with chlorine to make chloramines. To effectively destroy chloramines through shock treatment, the pool water FAC concentration must be about ten times the CAC.

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