2　Terms

2.0.1　Ultrafiltration

A membrane sieving and filtration technology，with filtration precision ranging between microfiltration and nanofiltration，normally 0.01μm-0.1μm.

2.0.2　Microfiltration

A membrane sieving and filtration technology，with filtration precision ranging between ordinary filtration and ultrafiltration，normally 0.1μm-1.0μm.

2.0.3　Nanofiltration

A separation process that the solvent on solution side penetrates through a macromolecule membrane under pressure to separate solvent from solution.It is a membrane separation process to remove multivalent ions，some monovalent ions and organic matters with minimum molecular weight of about 200-1000.

2.0.4　Reverse osmosis

A separation process that the solvent on solution side penetrates through a macromolecule membrane under pressure to separate solvent from solution.The reverse osmosis for seawater desalination is referred to as seawater reverse osmosis（SWRO）.

2.0.5　Flux

The amount of component penetrates through unit area of membrane in unit time.

2.0.6　Salt rejection ratio

The ability to remove salt from the inflow water，expressed as the percentage of the salt content difference between SWRO unit inflow water and product water to the salt content in inflow water.

2.0.7　Silt density index

The index representing the fine suspended solid content in water as calculated from the rate to clog the 0.45μm microfiltration membrane，referred to as SDI for abbreviation.

2.0.8　Fouling factor

The coefficient representing the performance degradation trend after the SWRO membrane is contaminated.

2.0.9　Energy recovery

The process to convert the pressure of SWRO brine to the pressure energy of inflow water，to reduce the energy consumption in reverse osmosis.

2.0.10　Device mixing ratio

The percentage of mixed brine to the water inflow quantity after mixing when the SWRO inflow water is mixed with the brine when flowing through the positive displacement energy recovery device.

2.0.11　Recovery ratio

Percentage of water output to total water inflow.

2.0.12　Producing water ratio

Percentage of net water output to water inflow after deducting the self-consumed water.

2.0.13　Gained output ratio（GOR）

Ratio of water output mass to heating steam mass（kg/kg）.

2.0.14　Flashing

The physical process that the preheated water enters a pressure reduction chamber and the steam is produced as the boiling point of water drops quickly.

2.0.15　Stage

A distilling and condensing unit to separate the feed water into fresh water and brine in a multistage seawater desalination unit；in the SWRO desalination unit，each unit formed by booster pump and membrane assembly through which the feed water flows is a stage.

2.0.16　Multistage flash distillation

The method to distill the water in seawater by stage by reducing pressure in steps after raw seawater is heated to a certain temperature，and to condense the produced steam to fresh water，referred to as MSF.According to the unit structure，the system can be divided into transversal pipe（short pipe），long pipe and vertical pipe types.According to different water feeding modes，they can be divided into brine recycle type（MSF-BR）and once-through type（MSF-OT）.

2.0.17　Heat recovery section

The stages cooled with circulating brine in an MSF-BR unit.

2.0.18　Heat reject section

The stages cooled with fresh seawater in an MSF-BR unit.

2.0.19　Top brine temperature

The maximum working temperature of brine in seawater distillation desalination equipment.It refers to the top brine temperature in the brine heater for multistage flash distillation process，and the top brine temperature in the first effect for low temperature multi-effect process.

2.0.20　Effect

A single evaporation and condensation water production unit at different temperatures in a multi-effect evaporator.The number of multiple effect water production equipment effects is referred to as the number of effects of multiple effect seawater distillation desalination equipment.

2.0.21　Multiple effect distillation

The method to produce fresh water from seawater by heating and evaporating seawater with a number of evaporating effects in series，where steam is condensed on one side of heat transfer tube to produce fresh water，and simultaneously released heat evaporates the seawater on the other side of the heat transfer tube to produce steam，which enters the subsequent effect as the heating source.

2.0.22　Low temperature multiple effect distillation

The multiple effect seawater desalination technology with top evaporation temperature of raw seawater normally below 70℃.A seawater desalination technology characterized by a number of horizontal tube falling film evaporators or vertical tube falling film evaporators connected in series and in a number of effect groups，and a certain amount of steam is fed to obtain distilled water equivalent to several times the amount of heating steam through multiple evaporation and condensation.

2.0.23　Thermal vapor compression

A process method to heat and pressurize low pressure（LP）vapor with high pressure（HP）vapor as power by mixing with LP vapor via spraying from Venturi nozzles.It is usually used in combination with low temperature multiple effect equipment，referred to in short as LT-MED-TVC or MED-TVC.

2.0.24　Mechanical vapor compression

A process method to heat and pressurize LP vapor with compressor.It is usually used in combination with low temperature multiple effect equipment，referred to in short as LT-MED-MVC or MED-MVC.

2.0.25　Noncondensable gases

Gas that is mixed with water vapor and cannot condensate in the condensation process of water vapor.

2.0.26　Condenser

The equipment designed to condensate secondary vapor at the end of a multiple effect distillation unit.

2.0.27　Product

Fresh waterproduced from the seawater desalination unit.