Re: Water purification questions

From: Chris Teichreb (
Date: Sat Sep 18 1999 - 20:36:42 PDT

Date: Sat, 18 Sep 1999 19:36:42 -0800
From: Chris Teichreb <>
Message-Id: <aabcdefg3273$foo@default>
Subject: Re: Water purification questions

Hi Paul,

>Can anyone comment based on knowledge gained from actual use or from
>literature on the folowing two points:
>1) Virkon S is the trade name for a bactericide, viricide and fungicide
>available in the UK.
> Assuming it's used as recommended by the suppliers is their any data
>on its safety?

        I'm not sure about the UK, but in Canada, manufacturers of
hazardous chemicals have safetly data sheets (WHIMIS, I believe is the name
of them). These give all the LD50's, what to do in case of spills,
dangerous reactions with other chemicals, proper storage techniques, etc.
I'm sure there's something similar in the UK, just phone or write the
suppliers and ask for it. In Canada, by law, they have to provide it.

>2) The above chemical is being used to destroy a deadly attack on
>orchids that is
> believed to have entered via stored rain water. Clearly a lot of us
>use rain water
> from storage. So is their a safe, reliable method fort purifying
>stored rainwater? I
> mentioned ultraviolet lights as used with aquarium water supplies
>but I've no
> experience with it nor with other purification processes. The need
>is to remove fungi,
> bacteria and potentially viruses too.

        UV purification is effective, although it may take a couple of runs
of the water under the lights depending on 1) depth of water (deeper water,
less UV penetration, more runs needed) 2) DOC content, or colour of the
water (water with brownish tinges to it is usually UV resistant, and will
need more power!) and 3) types and numbers of critters you want killed.
Some are more susceptible to UV than others, and some are extremely fast at
replicating, and are resistant in that way. Overall, I've heard positive
comments from UV sterilization. However, you do kill off the beneficial
bacteria as well as the harmful ones, and if you leave the water for any
amount of time in the open, it will become colonized again.

        Another suitable purification process is filtration. Essentially,
pass the water through a series of filters to get rid of the microbes. A
0.2um filter will work fine for getting rid of most bacteria and fungi,
however, to get rid of viruses will require a 0.02um filter.
Disadvantages: extremely expensive (the 0.02 filters especially, plus
they're slow), and water left out in the open will be colonized. Reverse
osmosis filtration or distilled dionized filtration systems will do all of
the above for you, except for the viruses.

        Final solution. Leave your rainwater, hope that you cp's are more
resilient than those fussy orchids ;-)!


Happy growing,


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