of chemical sanitizing agent during periodic
sanitization operations. The following maintenance program should be considered:
❖ Remove the cover or top access manway and chemically clean the interior of
the tank every 6 months.
❖ Conduct chemical sanitization of the entire ion removal and polishing system every six months using a 1% Peracetic Acid-Hydrogen Peroxide solution. (Sanitization
to be performed subsequent to RO membrane “rotation” discussed later in this
❖ Replace the hydrophobic vent filter
❖ Replace the tank cover or manway gasket every three years.
❖ Calibrate the multipoint level monitoring and control system annually.
❖ Replace tank piping/tubing fitting gaskets every two years.
❖ Replace hydrophobic vent filter housing
“bell-to-base” gasket every two years.
• RO Break Tank Repressurization Pump
The RO Break Tank Repressurization Pump
provides pressurized feed water to the downstream RO unit and recirculation capability
through the Ion Removal and Polishing Section
during chemical sanitization. The following
maintenance program should be considered:
❖Annual inspection of pump seals.
Replacement of seals as required or every
❖ Semiannual cleaning of pump motor fan
intake to remove dust and dirt.
❖ Semiannual tightening of pump feed
water and discharge connection clamps/
flange nuts, bolts or clamps
❖ Annual calibration of pump feed water
compound-type pressure gauge and pump
❖ Annual measurement of pump motor
❖ For single stage centrifugal pumps, inspection of pump impeller and casing.
• Reverse Osmosis System
The RO System provides removal of dissolved and ions impurities bacteria, bacterial
endotoxins, colloids, and organic material
with a molecular weight greater than about
150 Daltons. Gases such as oxygen that will
not chemically react with water and reactive
gases such as carbon dioxide that will react
with RO product water to produce ions are
not removed. In general, the conductivity of
RO product water (single pass) should be <
5 -10 µS/cm 25?C. The following maintenance program should be considered:
❖ Annual inspection of RO feed water
pump seals. Replacement of seals as required or every three years.
❖ Semiannual cleaning of RO feed water
pump motor fan intake to remove dust
❖ Semiannual tightening of RO feed water
pump feed water and discharge connection clamps/flange nuts, bolts or clamps
❖ Annual calibration of pressure, temperature, flow rate, and conductivity monitoring systems.
❖ Annual measurement of RO feed water
pump motor operating temperature.
❖ Semiannual replacement of RO membranes
with new or “spare” membranes that have
been cleaned, off site, by a service organization. RO membrane transfer/return should
be conducted using “Chain of Custody” with
unique serial number on each RO membrane. Off-site cleaning shall include pre
cleaning inspection and measurement with
documentation of product purity/flux, visual
inspection for degradation such as telescoping, three step cleaning (low pH, high pH,
and sanitization), final testing for ion rejec-tion/flux, treatment with an antimicrobial
agent, placement in a sealed plastic bag, and
packaged in a heavy weight cardboard box.
A copy of the “Chain of Custody” with pre
and post individual membrane cleaning data
shall be provided with shipping documents.
Individual membrane cleaning shall be conducted in “parallel configuration with other
membranes used for purification of properly
pretreated “Drinking Water”.
❖ Semiannual post RO membrane “loop”
components should be performed with
a 1% Peracetic Acid-Hydrogen Peroxide
solution subsequent to membrane replacement and rinse of preservative.
❖ Annual replacement of all RO membrane interconnector O-rings and end
❖ Replacement of RO membrane interconnectors every two years.
❖ Replacement of RO System feed water,
product water, and waste connections gaskets every two years.
❖ Replacement of RO membranes every
• Continuous Electrodeionization System
The Continuous Electrodeionization System
removes ions present in RO product water
such that the USP/EP “Stage 1” conductivity
limit for Purified Water can be achieved in
the downstream Storage, Ozonation, and
Distribution System. Product water from a
properly designed, maintained, and operated
continuous electrodeionization unit is generally < 0.1 µS/cm 25?C. Further, select continuous electrodeionization systems, in a recirculating or make-up mode will provide excellent
total viable bacteria control with product
water levels often < 1 cfu/100 ml (Membrane
Filtration of a 100 ml sample through a 0.45
micron filter disc, 120 hour incubation time period, 30-35?C incubation temperature, and either R2A or PCA culture media). The following
maintenance program should be considered:
❖ Monthly verification of ion concentrating
chambers, ion depleting chambers, and
waste pressure. Adjust pressure as required
per manufacturer’s recommendation.
❖ Biannual chemical sanitization as discussed earlier in this article or consistent
with continuous electrodeionization unit
manufacture’s recommendation if conflicting.
❖ Replacement of feed water (two), product
water, and waste fitting gaskets annually.
❖ Replacement of “plastic” feed water,
product water, and waste adapters every
❖Replacement of diaphragms in feed water and product water valves every two
❖ Calibration of pressure gauges, flow
meters, and conductivity instrumentation
❖ Replacement of continuous electrodeionization power panel cooling vent intake
❖ Replacement of continuous electrodeionization “stack” every 5 years.
• Post Continuous Electrodeionization
System Inline Ultraviolet Sanitization Unit
An inline ultraviolet sanitization unit (253.7
nanometer wave length) should be positioned
downstream of the continuous electrodeionization system and upstream of the final filtration system. Any bacteria present in product
water from the continuous electrodeionization
system would accumulate on the downstream
final membrane filtration system and replicate.
A biofilm could be established on the “dirty
side of the membrane filter with potential back
growth to the continuous electrodeionization.