Liquid purification or separation – Processes – Chemical treatment
Patent
1990-12-07
1992-07-14
Silverman, Stanley S.
Liquid purification or separation
Processes
Chemical treatment
210756, 210760, 210764, C02F 176
Patent
active
051300338
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns improvements in or relating to the sanitation of swimming pool water The present invention is also suitable for the treatment of cooling water systems.
Chlorine has previously been used in the treatment of swimming pool water. In an aqueous medium, chlorine forms hypochlorite ions which are oxidizing agents and possess bactericidal power. However, whilst chlorine acts in a sanitizing manner in swimming pools, the hazards of such sanitizing are well-known to swimmers, spectators and maintenance staff, all of whom have to cope with its effects on health, equipment and the bathing environment. In particular, leisure pools are becoming more popular, and with increased agitation due to flumes, water canons, wave machines etc, the problems associated with the use of chlorine are increased. Released into the air by pool activity, chlorine creates a corrosive atmosphere. This unseen irritant can effect the performance of competitive swimmers, repel spectators and shorten the life of expensive air recirculation equipment.
It has also been proposed to utilise bromine for the sanitation of swimming pool water. In such situation bromine in an aqueous medium forms hypobromite ions which again are oxidizing agents and possesses bactericidal power. In fact bromine has a higher bactericidal power than that of chlorine. Furthermore, water treated by bromine does not have the unpleasant odour and does not irritate swimmers to the extent that has been found utilising chlorine treatment.
The use of bromine as a sanitizing agent for swimming pool water suffers from the drawbacks relative to difficulties in the handling of liquid bromine. Thus, problems exist in providing adequate space wherein containers of liquid bromine can be safely stored and handled. Moreover,unacceptable levels of sodium bromide are introduced into the water when liquid bromine is utilised.
U.K. Patent Specification No. 1327531 proposes a method for sanitizing water by utilising a bromide which is oxidized whilst in the water by means of hypochlorite ions. The quantity of hypochlorite ions introduced are regulated in response to a continuous measurement of the amount of active bromine in the treated water. Such patent specification also discloses the use of from 20 to 50 mg per liter of sodium bromide in solution.
In the U.K., the Department of the Environment have indicated that the concentration of sodium bromide should preferably not exceed 15 mg per litre in the pool water. It is believed that such figure could also well apply abroad. Thus, the levels specified in U.K. Patent Specification No. 1327531 are totally unacceptable to current stringent safety levels. In any event, without a test procedure for sodium bromide being available, the Department of the Environment would be extremely unlikely to grant a health and safety acceptance authorisation. Furthermore, we have discovered that the introduction of hypochlorite ions as indicated in such patent specification is based on an incorrect premise. It had previously been thought that as the concentration of bromine ions in the pool water decrease then more hypochlorite ions would be required to oxidise the bromide to produce more bromine ions. This was the situation believed to exist, since when the bromine had carried out its sanitizing action, then it was substantially reconverted back to bromide. It was assumed that bromide was lost only by draining and backwashing, i.e. loss of pool contents.
However, we have now discovered that in fact a substantial proportion of bromide is lost when the pool water is passed through filters for recirculation purposes. Thus, the previous premise in U.K. Patent Specification No. 1327531 that decreased levels of active bromine required increased levels of hypochlorite only was incorrect; rather such decrease in active bromine content also required addition of bromide to make up for losses. Thus, previously, hypochlorite ions would be pumped into the swimming pool water erroneously and in a short time a free chlorine atmosphere would ex
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Nessler Cynthia L.
Silverman Stanley S.
Total Pool Chemicals Ltd.
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