Don’t get your sleeves wet!
By Allen J Wilson of Studies In Work H&S Consultants
I think everyone in the industry is aware that (approx) 75% of dangerous pollution in a pool is in the top 150mm of water. This is because bathers are aerobic and needing for oxygen swim close to the surface. This pollution is then released unconstrained into this area from their orifices; eye, ears, nose, throats, anal and genitalia plus perspiration. A large percentage of this will be from the anal orifice (recent USA research suggests each bather will introduce on average a gram of faecal matter) and so if a bather is standing up they will contribute to the remaining 25% at different depths, dependant on their height and activity and of course the water depth.
If the hazard (def: something with the potential to cause harm) is in the top 150mm we must ensure that we have a defence to this problem in the same area.
The defence comprises of an active level of disinfectant, chlorine in one form or another in 98% of pools at a pH that will facilitate the control of these dangerous pathogens, i.e. 72.to 7.6.
So why oh why are we telling operators to take a sample from an ‘elbow’s depth’ when the threat is not at that depth, it is in the top 150mm. Nobody has ever been able to give me a logical answer to this and it is about time we started to question guidance instead of blithely accepting it as ‘tablets of stone’.
Bacteriological testing is a monthly requirement where 500mls of water is taken in a sterile container and analysed in a UKAS laboratory. This sample should be taken whilst the pool is in use and again I advocate that the sample should be taken from the ‘dangerous’ area; the top 150mm. If there are dangerous bacteria, coliforms and pseudomonas, this is where they are likely to be.
Don’t take it at the surface as the water is exposed to chlorine losses through UV degradation and also volatisation (a word I have just made up) by the bather. Take it about 100mm (4”) below the surface and if we have a decent chlorine level there in the most polluted area it is logical to assume we have it everywhere. The World health organisation in their recent publication stated that each bather will swallow on average 100mls of water and we know where they drink it from, yes the surface.
Coming soon: exploding the myths about TDS