School conservation & safety

Dave Roberts dmr at nhm.ac.uk
Fri Nov 25 04:40:32 EST 1994


Hello.

I have been approached by a local primary school (ages 4 - 11) on a
question of microbiological safety.  As part of their environmental 
and conservation work, they have built a wildlife area and have
installed two tanks, each about 3 cu m, to catch rainwater.  The tanks
were provided for free, which is why they are so large.  The school's
engineer has said that to avoid the risk of Legionella (and presumably
Acanthamoeba) the tanks will need to be cleaned out at regular
(twice yearly) intervals.  This mainenance cost is very high and the
school is unwilling to carry it.

My reaction is that if the inflowing water is run though a coarse
screen to remove leaves and such, then through a settling tank,
to deposit small particles, the water collecting in the storage tank
will have very little carbon and thus will not sludge-up very
quickly, so that the cleaning schedule can reduce to every 3 or 5
years.

Does anyone have any experience of the actual risks being run here?

Thanks,      Dave



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