Page 295 - ro membanes

278 GLOSSARY
Filtrate The purified water that is produced by the granular media or membrane filtration.
Filtration The removal of particulate matter in source water by passing through a granular medium such as sand
and/or anthracite of ultrafiltration or microfiltration membranes.
Flux The rate of water flow across a unit of membrane surface area expressed in liters per hour per square meter
(L/m2 h or Lmh).
Fouling The accumulation of contaminants on the membrane surface (e.g., MF, UF, NF, or RO membranes) resulting
in loss of performance.
Hardness Concentration of calcium and magnesium slats in water.
Hydraulic turbo booster (HTB) A energy recovery device, also known as turbocharger, used in RO-desalination plant
that consists of turbine and centrifugal pump connected on the same shaft.
Inert Matter that neither dissolves in water nor reacts chemically with water or other substances.
Injection zone Geological formation receiving desalination plant discharge via deep injection well.
Inorganic Description of all matter that does not originate from living organisms (animals, plants, bacteria, etc.), also
referred as mineral.
Intake The facility through which source water is collected to produce fresh water in desalination plant. Interstage design (ISD) An RO-membrane configuration design to achieve a more even flux distribution that
combines three different models of membranes with different permeability within the same vessel.
Ion An atom or group of atoms/molecules that has a positive charge (cation) or negative charge (anion) as a result of
having lost or gained electrons.
Langelier saturation index (LSI) A parameter indicating the tendency of a water solution to precipitate or dissolve
calcium carbonate.
Membrane A device, usually made of an organic polymer, that allows the passage of water and certain constituents,
but rejects others above a certain physical size or molecular weight.
Membrane element An individual membrane unit of standard size and performance.
Membrane system A complete system of membrane elements, pumps, piping, and other equipment that can treat
feed water and produce clean water (permeate).
Microfiltration Filtration through membranes of pore size between 0.1 and 0.5 mm.
Near-shore discharge Disposal on the desalination plant waste streams through structure (channel, pipe, weir, etc.)
located on the shore or within several hundred meters from the shore in the tidal zone.
Net driving pressure (NDP) See transmembrane pressure.
Offshore discharge Disposal of desalination plant waste streams via long outfall structure extending beyond the
tidal zone.
Open intake Intake collecting source water directly from the water column of surface water body.
Organic Description of matter that includes both natural and man-made molecules containing carbon and hydrogen;
all organisms living in water are made up of organic molecules.
Osmosis The naturally occurring transport of water or other solvent through a semipermeable membrane from a less
concentrated solution to a more concentrated solution.
Osmotic pressure A pressure applied on the surface of semipermeable membrane as a result of the naturally
occurring transport of water from the side of the membrane of lower salinity to the side of the membrane with
higher salinity.
Pelton wheel An energy recovery technology used in RO plants consisting of enclosed turbine in which concen-
trate is applied through a high-velocity nozzle onto spoon-shaped buckets located on the periphery of the
wheel.
Permeability The capacity of membrane material to transit flow, also named flux.
Permeate (sometimes called filtrate or product water) The purified water produced during membrane filtration. Pigging The practice of using pipeline inspection gauges or “pigs” to perform various maintenance operations on a
pipeline.
Pressure exchanger (PX) An energy recovery technology used in RO-desalination plants that consists of individual
fiberglass vessels connected to common feed and concentrate manifolds, each of which contains a ceramic rotor
with a number of cylinders, i.e., rotor chambers.
Pressure filtration Filtration aided by imposing pressure across an enclosed filter vessel.
Pressure vessel A housing containing membranes in a preset configuration that operates under pressure; for RO
systems, pressure vessels are plastic or metal tube-shaped devices that house 6e8 RO elements.