SNOWPURE, LLC, 2005-2018
VERSION 3.5 (XL+EXL)
–FEBRUARY 2018
PAGE 66
Appendix #4: XL/EXL Module Chemical Sanitization Procedure
The simplest and best technique for sanitizing traditional DI beds is to separate and
regenerate the resins. The conditions presented by the strong acid and base kill and
eliminate bacterial colonies.
EDI modules under applied voltage are constantly splitting water and generate locally
very high and very low pH. These pH extremes are believed to create a biostatic
environment within the EDI module, especially on the product side where it is critical.
A good study of this topic was published by Millipore in 1990. They found that a
weekly-sanitized RO-EDI system maintained low bacterial and endotoxin counts, and
that the EDI effluent was similar in counts to its influent. When the sanitization
regimen was stopped for three months, the concentrate stream did rise in counts, yet
the product stream did not. Their conclusion was that the critical product side of the
EDI module did indeed act as a biostat.
The best sanitization method, according to SnowPure, is to keep the unit operational.
In this mode, bacterial colonies should not grow, especially on the product side.
EDI Module Chemical Sanitization:
There is no ideal sanitization regime for EDI. Sanitizers consist of oxidizers, ions,
and/or organics. Organic sanitizers require long rinsing times to reduce TOC to
acceptable levels. Ionic sanitizers require a post-sanitization regeneration
procedure. Oxidizers can reduce the lifetime of the module via oxidation of resins
and membranes.
Periodic sanitization can be one of several methods. We recommend:
1.
Use of “hydrogen peroxide-stabilized peracetic acid” as used in current RO
systems, such as the use of Minncare
®
Cold Sterilant by Minntech
12
. Use the
low concentration of 0.1% Minncare
®
for 1 hour, ideally in recirculation, or
2. If any bacteria are pernicious or persistent, *carefully* use 1% Minncare
®
for 1
hour (repeated use will oxidize EDI resins), or
3.
Use of Avista Technologies RoCide™ DB-20
13,14
at 100 ppm (20%) for 1
hour, or
4. Use of 200 ppm RoCide DB-20 for 6 hours if any bacteria are pernicious or
persistent.
Other Sanitization Notes:
We know which chemicals prevent growth and should not harm DI systems.
However, all have some side effects and cautions.
12
See
13
Note: DB-20 is not approved for USP water.
14
Note: MSDS and technical brochure available at