15
they are not exactly equal, in most dis cus sions
ppm = mg/l.)
R.O. Membranes are rated by the amount of
dissolved solids that are rejected. This rating is
a ratio of the TDS in the feed water to the TDS
in the product water and is reported as
Percent
Rejection
. If the feed water contained 100 ppm
of TDS and the product water contained 10 ppm
of TDS, 90 ppm have been rejected and the
reject ratio is 90%.
Percent Rejection =
Feed TDS–Product TDS x 100%
Feed TDS
EXAMPLE: Feed water is 500 ppm TDS and the
product water is 75 ppm TDS.
Percent Rejection = 500 – 75 x 100%
500
Percent Rejection = 0.85 x 100% or 85%
B. Water Quantity
Water quantity is termed
Flux
or
Product Water
Rate
and is measured as the amount of water
pro duced in one day. It is reported as
Gallons
per Day
(gpd) or
Liters per Day
(lpd).
The fl ow of water to drain is the
Reject Water
Rate
and is measured as
Gallons per Day
(gpd)
or as
Milliliters per Minute
(ml/min).
Milliliters per minute x 0.38 = gallons per day
EXAMPLE: The drain fl ow will fi ll a graduated
cylinder to the 150 ml mark in one minute.
150 ml/min. x 0.38 = 57 gpd
If the container available measures ounces, use
the following conversion:
Ounces per minute x 11.2 = gallons per day
EXAMPLE: The product fl ow will fi ll 2½ ounces
in two min utes.
2.5 oz. ÷ 2 min. = 1.25 oz./min.
1.25 oz./min. x 11.2 = 14 gpd
The
Reject Ratio
is the amount of water
pro duced
compared to the amount of
water fl owing to drain.
Reject Ratio = Reject Rate_
Product Rate
EXAMPLE: The product rate is 14 gpd and the
reject rate is 56 gpd.
Reject Ratio = 56 ÷ 14
Reject Ratio = 4 or 4–to–1
The
Percent Recovery
is another way to
measure the amount of water produced as
compared to the amount actually used.
% Recovery = Product Rate x 100%
Feed Rate
NOTE: The total fl ow or feed water rate into the
system is the sum of the product fl ow and the
drain fl ow.
EXAMPLE: The product water rate is 14 gpd and
the drain water rate is 56 gpd
Feed Rate = 14 gpd + 56 gpd = 70 gpd
% Recovery = 14 gpd x 100%
70 gpd
% Recovery = 0.20 x 100% or 20%
C. Net Pressure Differential
Most R.O. Membranes are rated at a
standardized condition of 77°F (25°C) and
65 psig (450kPa) discharging to atmospheric
pressure.
Product water quality and quantity greatly
depend upon the
Net Pressure Differential
(Dp) across the R.O. Membrane. This pressure
dif fer en tial is a summation of the feed water
pressure at the Membrane, which tries to push
the water through, the pressure in the Holding
Tank, which tries to push the water backwards
and the osmotic pressure, which also tries to
push the water backwards.
The
Osmotic Pressure
is in proportion to the
OUT
IN
In-Line Activated
Carbon Post Filter
3/8" Blue
To
Dispensing
Faucet
3/8" Blue
IN–LINE ACTIVATED CARBON
POST FILTER ASSEMBLY
Figure 5
Summary of Contents for ECLIPSE WRO-35
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