pH Solution Protects Membrane in Reverse Osmosis0 pages

Application Data Sheet
ADS 2000-06/rev.B
March 2011

Food and Beverage Industry

Innovative pH Solution Protects Membranes
in Reverse Osmosis Systems
RESULTS
• Optimize Water Purity
• Decrease Membrane Consumable Costs
• Asset Protection
• Water Use Optimization

BACKGROUND

SOLUTION

Reverse osmosis (RO) is a technique for removing
dissolved solids from filtered raw water. It is used in
a number of different applications. For Beverage
Producers, water purity for ingredient purposes is an
important start to producing quality, reproducible
branded products.

Critical to the measurement is the pH sensor. The
Model 3900 and 3900VP General Purpose pH
Sensors from Rosemount Analytical can accurately
monitor the pH of the water going into the RO unit.
The ACCUGLASS™ glass formulation resists cracking,
and the double junction prolongs the sensor’s life.
The sensor conveniently mounts via ¾" or 1" MNPT
process connections, and a water tight variopol (VP)
cable connection allows for quick sensor replacement.

Reverse osmosis works by pressurizing water and
forcing it through small, permeable membranes. The
water passes through the membranes, but the
dissolved solids are relatively impermeable and are
rejected, producing high purity water (see figure 1).

CHALLENGE
pH measurement plays an important role in the
membrane purification process for Beverage
Producers. Most beverages are slightly acidic while
raw pre-treated water tends to be slightly alkaline. In
addition, the membrane fibers are cellulose based
and degrade in alkaline conditions, which results in
lower membrane efficiency from precipitation.
Membranes can be regenerated through back-flushing
techniques; however, long term exposure to alkaline
conditions will eventually lead to membrane replacement at a significant expense.
Often, pH sensors are omitted from the Reverse
Osmosis Systems to minimize initial investment
expenditures. Integrating a pH measurement into the
local RO control system requires significant programming efforts as well as hardware expansions to
PLC’s and wiring personnel to bring the signals into
the controllers.

The Model 3900(VP) can be used with the Model
6081P Wireless Transmitter, which is WirelessHART®
7 compliant. The Model 6081P utilizes power optimized
electronics that extend the life expectancy of the
intrinsically safe power module. The WirelessHART 7
feature eliminates any cable runs from the pH transmitter to the control system. The Model 6081P is
automatically recognized on any compliant Gateway
such as a Model 1420 as long as the wireless network
ID and the network join key have been established
for the device. The 6081P also transmits important
diagnostic information on the sensor’s health that
may not be available with traditional PLC’s.