Water purification

Winston Atkins <winston.atkins [at] duke__edu> writes

>Water Filtration for Conservation Lab
>
>Duke University Libraries is planning a new book and paper
>conservation lab and one of the issues we need to address with our
>architects is how to spec out the water filtration system. I'd
>appreciate advice from you all regarding:
>
>    *   merits of deionization vs reverse osmosis,
>
>    *   volume (gals/minute) to request for a large washing sink
>
>    *   degree of purity (see paragraph below--our architects'
>        consultants tell us that getting 3 megohms resistance will
>        be difficult; RO will give us 0.5 to 1.0 megohm resistance,
>        putting in DI beds will give us up around 18 megohm)
>
>    *   issues of cost (initial purchase and ongoing maintenance)
>
>    *   ease of maintenance

Here at the NC Museum of History I use a large (98 inch long by 60
inch wide, by 5 1/2 inch high) stainless steel standing wash table
in conjunction with deionized water.  The deionizing system consists
of a particulate filter, a 1.2 cubic foot purifying carbon tank for
removal of organic contaminants and two 1.2 cubic foot tanks with
polystyrene beads in them which produce 18 megaohm water. There is
an device between the first and second deionizing tanks which
indicates when the first tank's ability to deionize the water is
exhausted; a small light turns red when a salt bridge has formed
because of the presence of excess ions.  In fact I have never seen
this happen before the maintenance schedule dictated a switch out of
the first DI tank.  I would estimate that I use about 75-100 gallons
of DI H2O in a six month period--a very rough extrapolation based on
data from one of my treatment reports for a single large object.

Both carbon and first deionizing tanks are replaced every six months
at a cost of $115.00 for each (at which time the second tank is put
in position as the first).  Maintenance is very easy--I simply hand
the maintenance man a towel and ask him to clean up any small pools
of water that may be on the floor after he's switched everything
out. Previously, before my time here, the museum was using larger
tanks but they were easily able to downsize to smaller tanks when it
was realized that these would be adequate.  I don't currently have
in front of me information on (1994) installation costs but may be
able to track that down.

Our service contract is with Pure Water Solutions in Hillsborough
919-644-1290.  If you have not already contacted them, you may want
to in order to determine approximate (and current) installation and
maintenance costs based on what types of treatments you plan to
regularly perform.  Feel free to contact me if you would like to
come by and see the lab and the water system.

Anne Peranteau
Textile Conservator
North Carolina Museum of History
Raleigh, NC


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                  Conservation DistList Instance 21:6
                  Distributed: Saturday, May 26, 2007
                        Message Id: cdl-21-6-001
                                  ***