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Subject: Water purification

Water purification

From: Geoffrey I. Brown <geoffrey.i.brown>
Date: Friday, February 11, 1994
I recommend a deionization system for water purification.  The standard
set-up includes a pre-filter (10 Micron), two mixed resin beds or tanks
and a post-filter (5 Micron).  If needed, a turbidity filter and a
carbon filter can be added to trap sediment and organics, respectively.
A UV sterilizing cell can also be added if live microorganisms are a
problem.  These systems work well as they have virtually no down time.
When the first resin bed is exhausted, you call the vendor for a
replacement and work off the second bed.  These are usually systems
where you lease or even own some of the components but rent, on an
exchange basis, the resin beds.  The other filtration components get
replaced.  The virtue of De-I is that the process is very efficient at
removal of metallic ions, and these are often our biggest problems in
the water supply.

Reverse Osmosis can produce similar or even better quality of water than
De-Ionization, but the equipment is very expensive, the output is
relatively low, and if there is a problem with the critical RO membrane,
your system is down. Replacement of these membranes tends to be fairly
expensive but these systems do not usually use De-I resin beds exchanges
which also can be expensive.

Be careful to use only PVC, Stainless steel, or Tin-coated materials in
your water system.  I have seen very expensive installations that
terminate in common brass faucets, thereby negating all the water
treatment.  I recall that the LC had a problem many years back because
of a copper storage tank and copper piping!

The one other type of water treatment that is commonly seen is a still
that produces distilled water.  Stills remove organics well but are much
less effective on metal ions.  The cost of stills for adequate water
quantities is usually very high and their cost of operation is always
high because of their high energy use.

Geoffrey Brown
Kelsey Museum
University of Michigan

                  Conservation DistList Instance 7:59
                Distributed: Tuesday, February 15, 1994
                        Message Id: cdl-7-59-006
Received on Friday, 11 February, 1994

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