Lync WQ-RS
SECTION 1: INTRODUCTION
L- OMM-005_A
•
2/23/2022
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Figure 1-1 RO Membrane
1.3. Pretreatment
The RO feed water must be pretreated in order to prevent membrane damage and/or fouling.
Table below shows the feed water chemistry requirements.
pH
6 to 9
Hardness (maximum)
Less than 1 grain per gallon as CaCO3 (Softened) or anti scale
chemical injection if not softened (contact your Lync representative)
Water Pressure
20
– 90 psi
Temperature
35 - 100°F (2 - 38°C)
Free Chlorine
None allowed
Iron (maximum)
0.1 ppm
Manganese
0.05 ppm
Oil and H
2
S
None Allowed
Turbidity
Less than 1.0 NTU
Silt Density Index (SDI)
Less than 5.0 SDI
Proper pretreatment is essential for reliable operation of any RO system. Pretreatment
requirements vary depending on the nature of the feed water. Pretreatment equipment is sold
separately. The most common forms of pretreatment are described below.
Media Filter
- Used to remove large suspended solids (sediment) from the feed water.
Backwashing the media removes the trapped particles. Backwash can be initiated by time or
differential pressure.
Water Softener
- Used to remove calcium and magnesium from the feed water in order to
prevent hardness scaling. The potential for hardness scaling is predicted by the Langelier
Saturation Index (LSI). The LSI should be zero or negative throughout the unit unless
approved antiscalants are used. Softening is the preferred method of controlling hardness scale.
Carbon Filter
- Used to remove chlorine and organics from the feed water. Free chlorine will
cause rapid irreversible damage to the membranes.
The residual free chlorine present in most municipal water supplies will damage the thin film
composite structure of the membranes used in this unit. Carbon filtration or sodium bisulfite
injection should be used to completely remove the free chlorine residual.
Chemical Injection
- Typically used to feed antiscalants, coagulant, or bisulfite into the feed
water or to adjust the feed water pH.
Feed Water
Product Water
Reject Water
