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EZ & Enhanced SDI Units
Applied Membranes now offers a
cost-effective, automatic SDI Monitoring System.
Complies
with ASTM D4189-95
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Monitoring the fouling
tendency of RO feedwater has long been a challenge. Usually fouling is not
noticed until the RO membranes need cleaning, resulting in expensive downtime
or, worse yet, membrane replacement.
Numerous methods have been
used to measure the fouling tendency of feed waters, including turbidity,
particle counting, and manual silt density index (SDI) testing. It
is difficult to correlate turbidity and particle counting to membrane fouling
since they do not directly measure the fouling or "plugging" nature of
the particles in suspension. Since the manual SDI test measures this
plugging tendency, it has proven useful in indicating fouling tendencies.
However, the manual SDI testing method is tedious and time-consuming.
The EZ SDI™
& Enhanced SDI automatically
and consistently monitor the silt density index of RO feed water.
Operators can quickly and regularly check the effectiveness of the RO
pretreatment system without bothering with labor-intensive manual tests.
It is easy to install,
easy to operate, and sells for a fraction of the cost of other automatic SDI
testing equipment.
| Operation |
| The EZ SDI™ &
Enhanced SDI are microprocessor
controlled and fully automatic. The monitors
are housed in a NEMA 4X
enclosure and are designed for permanent installation in industrial
environments. The filter holder allows the use of standard 25mm
test filters available from a number of suppliers. Replacing
the media is a two-minute process and the test is initiated with the
press of a button.
A blinking indicator notifies the operator of
completion of the test. The SDI results may then be read from the
LCD display. The display is equipped with an LED backlight making
it easy to see the results in any environment.
The test pressure is controlled with a
high-quality internal pressure regulator which can accommodate inlet
pressures above 100 psi. This allows the sample to be taken from
the high pressure side of the RO feed pump, thus eliminating
cumbersome and expensive sample boost pumps. The test pressure is
constantly displayed in the LCD and the EZ SDI & Enhanced SDI™ alarms and aborts the
test if the pressure falls outside of ASTM specifications.
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| Principle |
| The EZ SDI™
& Enhanced SDI use the same testing method as specified in ASTM D4189-95. This
standard method indicates the quantity of particulate matter in water
and is applicable to relatively low (<1.0 NTU) turbidity waters such
as well water, filtered water, or clarified effluent samples.
Since the size, shape, and nature of particulates may vary, this test
method is not an absolute measurement of the quantity of particulate in
a particular water source. Maximum SDI values of RO feed water are
commonly specified by RO membrane manufacturers, and demonstrating
adherence to these SDI specifications may be necessary to receive
guaranteed performance from the membrane supplier.
As specified in the ASTM method, the
EZ SDI™ & Enhanced SDI calculate
SDI at five-, ten-, and fifteen-minute
intervals. The monitor examines the temperature of the feed water
and displays the change in temperature during the test.
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| Unique Features |
| The
EZ SDI™ & Enhanced SDI incorporate a number of unique features which ensure reliable
operation and dependable results |
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- Continuous Sample
Flow -
The EZ SDI™ & Enhanced SDI are designed for permanent installation. In order
to prevent stagnant conditions in the sample line, the monitor
continuously allows a side stream of sample to flow through the
monitor up to the point where the sample enters the filter. A
specially designed orifice controls the rate of this side-stream
flow. The orientation of the flow control orifice also allows
air in the sample line to be separated from the sample before the
sample enters the filter holder.
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- Air Venting -
The unique design
of the filter holder allows air to be vented from the filter chamber
before the beginning of each test. This, together with precise
volume measurement, ensures that the repeatability of SDI values
from the EZ SDI™ & Enhanced SDI monitors far exceed that of the manual test.
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