Chapter 9: Glossary; Terms - Sea Recovery SRC Aqua Matic 700-1 Owner's Manual

9
Chapter
Glossary

Terms

Cascading Failure
A failure in a system of interconnected parts in which the failure of a part can trigger the failure of successive parts.
Boundary Layer
(Also known as Concentration Polarization.) When water permeates through the membrane, nearly all the salt is left
behind in the brine channel. In any dynamic hydraulic system, the fluid adjacent to the wall of the vessel is moving
relatively slow. Even though the main body of the stream is turbulent, a thin film adjacent to the wall (membrane) is
laminar. This thin film is called the boundary layer. At the boundary layer the salts are saturated and can readily adhere
to and pack into the RO membrane element surface if the Feed Water Flow is insufficient. For this reason, it is important
to maintain sufficient Feed Water flow, to prevent Concentration Polarization, through the RO membrane element.
Brine Velocity
The brine flow over the membrane surface is very important to both product water quality and quantity. At low flows,
concentration polarization occurs, causing the water quality to decline. In addition to inferior product water quality, low
brine flows can increase the precipitation of sparingly soluble salts which will foul the RO membrane element surface
(concentration polarization). If this occurs, the product water flux (production) will decline. The Feed Pump integrated
design provide a relatively smooth and continual flow of Feed Water across and through the RO membrane element.
Compaction
Some densification of the membrane structure may take place while operating at elevated pressures, above 1000 PSI.
The change is known as compaction and is accompanied by a reduction in the water permeation rate. When the RO
membrane element is subjected to elevated pressures beyond 1000 PSI the Product Water Channel becomes squeezed
which results in restriction and in turn product water recovery reduction.
Osmotic Pressure
The transfer of the water from one side of the membrane to the other will continue until the head (pressure) is great
enough to prevent any net transfer of the solvent (water) to the more concentrated (feed water) solution. At equilibrium,
the quantity of water passing in either direction is equal, and the head pressure is then defined as the "Osmotic Pressure"
of the solution having that particular concentration of dissolved solids.
Pressure
The operating pressure has a direct affect on product water quality and quantity. Both factors will increase as the system
pressure increases (higher quantity and higher quality within design limits). The system must be operated at the lowest
pressure required to achieve the designed product water flow rate. This parameter also minimizes compaction, which
proceeds at a faster rate at higher pressures as well as at higher temperatures. The System self adjusts its operating
pressure to maintain a precise amount of Product Water Flow. However in so doing, at low temperatures and or high
salinity feed water conditions the system will operate at higher than normal pressure in maintaining the specified amount
of product water flow. This is normal, to be expected, and is due to the design characteristics of the system.
Spiral-Wound Membrane
The spiral-wound membrane consists of multiple membrane envelopes each formed by enclosing a channelized product
water carrying material between two large flat membrane sheets. The membrane envelope is sealed on three edges
with a special adhesive and attached with the adhesive to a small diameter pipe. A polypropylene screen is used to form
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