Swimming Pool Scene INDUSTRY NEWS
Acid Test Recommendations ) – or in leisure pools
When deciding on a pH correctant for your pool it is important to do a risk assessment in accordance with the Control of Substances Hazardous to Health regulations (COSHH). You need to think about the possible
The UK’s
authoritative guidance on swimming pools and spas
“Dedicated
solely to raising standards in swimming pool water treatment”
www.pwtag.org
Pool Water Treatment Advisory Group Email:
chair@pwtag.org ABOVE: Pwtag advises on ph correctants for swimming pools.
If you can’t prevent exposure, you need to control the risk of harm as much as is ’reasonably practicable’. This may involve issues of ventilation, PPE, management controls and human factors. The risk assessment should also consider maintenance, exposure monitoring, health surveillance, information and training. Now the choice. There’s nothing in it financially – taking into account prices, storage and safety measures.
CARBON DIOXIDE
It has advantages: easier and safer to handle; comes in bulk; no special protective equipment; can’t be accidentally mixed with sodium or calcium hypochlorite – no possibility of accidental production of chlorine gas. Also, due to its natural buffering action CO2
gives easier, slower control of pH. And
there is no secondary pollution introduced – chlorides (from hydrochloric acid) or sulphates (from sodium bisulphate). There are disadvantages: it asphyxites when released in confined areas; it is not suitable where the source water alkalinity
56 Swimming Pool Scene INDUSTRY NEWS
harms, how they can be reduced and whether avoided by using something else, or a safer version.
is over 150mg/l or calcium hardness over 300mg/l (both as CaCO3
and spas, where water features will drive it out of the water.
HYDROCHLORIC ACID It has advantages: less effect on alkalinity reduction than sulphuric acid or sodium bisulphate; adds less to total dissolved solids; safer than sulphuric acid; can come in bulk.
There are disadvantages: concentrations over
5 or 10% (up to 35%) are pungent and fuming; in general, irritating; the quantities required may present a storage problem; produces chlorine gas when mixed with hypochlorites.
SODIUM BISULPHATE It has advantages: less atmospheric corrosion than concentrated hydrochloric acid; no additional chlorides introduced; as a powder (rather than liquid) is thought to reduce mixing accidents
There are disadvantages: needs to be dissolved before use; produces chlorine gas when mixed with hypochlorites; can produce a sulphuric acid mist; irritates the skin and eyes; reduces alkalinity much more rapidly than hydrochloric acid; sulphate concentration has to be monitored to minimise attack on cementitious grout.
SULPHURIC ACID PWTAG has for some time been concerned about the use of concentrated sulphuric acid in pools. See PWTAG Technical note number 1 and Swimming Pool Water.
ABOVE: The new edition of Swimming Pool Water: treatment and quality standards for pools and spas is available now from
pwtag.org.uk.
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