As a portable exchange business grows, new accounts may
include users of ultrapure water. (Ultrapure water generally refers to water
with a resistivity greater than 15 megohm.) These users may require
documentation and procedures that the dealer may not be accustomed to
providing. This article will describe some of the requirements that many high
tech customers may ask their supplier of ultrapure water to provide.
The portable exchange business is growing because end users
want to have a reliable supply of pure water without having to deal with
chemicals, regeneration waste, power demands and all the other requirements of
an in-house system. A portable exchange deionization (PEDI) dealer can deliver
deionized water to the end user, freeing the customer of the need to deal with
chemicals, regenerations, wastewater disposal and regulatory compliance. Those
liabilities now are transferred to the dealer.
Accountability and the ability to trace the components,
chemicals and procedures of portable exchange regenerations require careful
documentation and good housekeeping. In these days of computerization, it
should not present too great a burden to the PEDI dealer.
The need for this accountability can be explained by the
requirement to be able to find and correct past mistakes as well as establish
liabilities during upset conditions. A sobering example of this might be the
production of off-spec water at a hemodialysis clinic that leads to patient
deaths or illnesses. What happened to cause this? Where did the contaminants
come from, the raw water or from the PEDI tanks? Did the upset stem from a
material source or from a procedural error?
Another example could be PEDI tanks used for pharmaceutical
water production. USP specifications do not allow “added substances,”
and should these added substances (dissolved solids, organics or particles)
appear in the water, it is paramount to find where they came from, who is
responsible for their presence and how this episode can best be prevented in
the future.
A portable exchange regeneration plant can be a heavily
regulated business. There are federal, state and local regulations to stay in
compliance with. There will be additional rules to adhere to if the dealer is
providing regeneration services to tanks that are used for hemodialysis
(USFDA), pharmaceutical (USP) or electroplating operations (EPA).
Ion Exchange Resins
The PEDI operation may have segregated batches of resin. If
this is the case, it is relatively easy to keep track of new or old batches,
what tanks they end up in before being sent out to service, when they are
regenerated and what the quality history is. Record the purchase dates, the
type of resin that was purchased and include the proper documentation listed
below.
The PEDI plant must keep on hand Material Safety Data Sheets
(MSDS) of all the chemical components used in the plant including ion exchange
resins. If the plant is regenerating resins that are used for medical or
pharmaceutical applications, it also is important to have on hand Certificates
of Analysis (C/A) of each batch of resin that is provided by the resin
manufacturer.
The C/A is provided free or for a nominal fee from the resin
manufacturer depending on the degree of complexity required. Basically, it
states that the resin provided has been tested and meets the published
specifications of the resin. Most often, a standard C/A that lists the items in
the sidebar to the left is sufficient.
Activated Carbon
It is recommended to have granular activated carbon tanks
placed in front of the PEDI tanks when in service to remove chlorine or
chloramines and, in general, to protect the ion exchange resin from oxidation
and organics. The carbon can be purchased as standard or acid-washed grades
depending on the ultimate service requirement.
Granular activated carbon used for high purity customers
also may need to be supplied with C/A from the manufacturer. The C/A for carbon
typically lists the following.
• Lot
number.
• Percentage
of moisture.
• Iodine
number.
• Abrasion
number.
• Uniformity
coefficient.
• Screen
size distribution (percentage on standard U.S. mesh size screens).
Premium medical grades of acid-washed activated carbon are
available from select manufacturers. These carbons have been treated for the
ultimate in purity and are suitable for use in treating water for hemodialysis
and pharmaceutical processes. These carbons undergo additional certification
that can include an ash analysis to determine that any metals present are below
the acceptable limits. These metals usually are reported as mg/kg of carbon.
• Aluminum
• Arsenic
• Barium
• Silver
• Chromium
• Copper
• Lead
• Mercury
• Zinc
Chemicals
PEDI plants use hydrochloric acid or sulfuric acid to
regenerate the cation resin, sodium hydroxide to regenerate the anion resin and
sodium chloride to regenerate softeners or assist in the separation of the
mixed-bed components. Safety regulations require that an MSDS be kept on file
for any chemical used in the plant. The dealer also should request C/A from the
chemical supplier for any chemicals that come in contact with the resin.
• Hydrochloric
Acid
C/A should list
€ Percentage
of HCl.
€ Iron
in ppm.
€ Color,
APHA.
• Sulfuric Acid
C/A should list
€ Percentage
of H2SO4.
€ Iron
in ppm.
€ Manganese
in ppm.
€ Color,
APHA.
€ Nickel
in ppm.
• Sodium
Hydroxide
C/A should list
€ Total
alkalinity percentage as Na2O.
€ Total
alkalinity percentage as NaOH.
€ NaCl
in ppm.
€ Iron
in ppm.
• Sodium
Chloride
C/A should list
€ Percentage
of sodium chloride.
€ Percentage
of calcium and magnesium.
€ Percentage
of moisture (for rock salt).
€ Percentage
of water insolubles.
€ Percentage
of iron.
€ Appearance
(visual description).
€ Screen
analysis on U.S. mesh
(for rock salt).
Regeneration Information
The performance of the PEDI tanks in the field are
influenced by many factors, but the most important one to keep in mind is that
the better the regeneration performed on the resin, the better quality water
produced in the field. The success of the regeneration procedure itself depends
on many controllable factors in the regeneration plant.
The operator of the PEDI plant should be striving for
excellent, repeatable results. Therefore, standard procedures must be
developed, fine-tuned and committed to record as an easy-to-follow written procedure.
This procedure should be in the form of a checklist for the operator to follow.
Regeneration information should be maintained and recorded
into a log.
(See the sample log on this page.)
All of the procedures and documentation mentioned here should
be kept in a book (or books) that can be made available for any visiting
inspectors. The procedure book can include more details than just the raw data
and should explain which precautions are in place, which quality control
methods are used and what the course of action is in the event of an
unsuccessful regeneration. Committing this information to writing and
maintaining an up-to-date regeneration procedure book will greatly assist the
PEDI dealer in getting the plant approved by the regulatory authorities.
It may be a good idea for PEDI dealers to invite the
regulating entities (EPA, county sewer utility, FDA, etc.) to inspect the
regeneration plant to see that the proper procedures and laws are being
followed. This gesture of cooperation can go a long way to establishing a
mutually beneficial relationship between the PEDI plant and the watchdog
agencies. It is particularly timely to get the advice of the regulatory
agencies when entering a new market such as medical or hemodialysis.
The ion exchange resin is the heart of the PEDI operation.
Good record keeping will enable a trained operator to see the initial effects
of resin fouling or substandard regenerations. Test the resin regularly,
annually at the minimum. Contact your resin supplier to receive a regeneration
plant audit.
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