Page 294 - ro membanes

Glossary
Aerobic Containing oxygen.
Ambient Surrounding of background.
Ambient seawater Seawater in the open ocean used for desalination.
Anaerobic Not containing oxygen.
Anthropogenic Caused by human activity.
Antiscalant A chemical added to the saline source water fed to a membrane system, e.g., RO membranes, which
inhibits or prevents precipitation of minerals on the membrane surface.
Aquifer A natural underground layer, often of sand or gravel, that contains water.
Backwash The process of solids’ removal from a filter media or membrane surface by applying air and/or clean
water in the opposing flow direction.
Bactericide A chemical capable of destroying bacteria.
Biocide A chemical used to inactivate microorganisms (e.g., chlorine).
Biofouling Presence and growth of microorganisms and their secretations on the membranes surface.
Biomass Organic matter of vegetable or animal origin.
Brackish water Water with a total dissolved solids concentration less than 15,000 mg/L.
Brine (concentrate) Water with high which is a product of the desalination process salinity, usually in excess of
2000 mg/L for brackish water and over 37,000 mg/L for seawater.
Brine seal Rubber or plastic device of special design, which is installed on the outerside of the membranes near their
feed side, which seals the space between the membrane elements and the pressure vessel to prevent the bypassing
of feed water/concentrate around the elements.
Coagulation Pretreatment process used in some desalination plants, which consists of addition of salts (e.g., ferric
chloride) to source water in order to improve suspended solids agglomeration and their more efficient removal by
further treatment, i.e., sedimentation or filtration.
Colloids Suspended solids with a diameter of less than 1 mm that cannot be removed by sedimentation alone. Colocation Location of a desalinated plant with an existing power generation facility with potential connection of
desalination plant intake and/or outfall to the cooling water discharge.
Concentrate See brine.
Concentrate management The handling and disposal or reuse of concentrated liquid generated by the desalination
system during the salt separation process.
Concentration polarization Phenomenon in which solutes form a dense, more concentrated layer next to the
membrane surface and restricts flow through the membrane.
Desalination A process that removes dissolved solids (salts) from saline source water.
Diffuser Offshore end portion of outfall, which consists of discharge ports configured to maximize the mixing of the
desalination plant discharge with the ambient receiving waters.
Dissolved air flotation (DAF) The removal of particulate matter by attaching the particles to rising air bubbles in a
specially designed flotation tank.
Double-pass or Two-pass RO system RO system that consists of two sets of RO trains configured in series, in which
permeate from the first set is processed through the second set of RO trains.
Dual work exchanger energy recovery (DWEER) An energy recovery device used in RO-desalination plants, which
represents an isobaric type pump for direct conversion of concentrate pressure into RO feed-water pressure via
piston.
Ecosystem A community of living organisms interacting with each other and with nonliving components of the
environment they inhabit.
Effective size The media grain diameter at which 10% of the media by weight is smaller than this diameter, as
determined by sieve analysis.
Feed water The influent water that is fed into a treatment process/system.
277