AlternativeLEC2.pdf

Alternative Water Treatment

Membrane Technologies

Part 1

£ General Description

£ Taxonomy

£ Application

Membrane technology Î basic terms

Array Î Interconnected stages in series

Feed Î Input stream to the membrane array

Concentrate (reject, residual stream) Î Membrane

output stream that contains higher TDS than the feed

stream

Brine Î concentrate stream containingTDS >36000 ppm

Permeate (product) Î Mmebrane output stream that

contains lower TDs than the feed stream

Pressure vessel Î Single tube with several membrane

elelemnts in series

Stage (bank) - Parallel pressure vessels

Rejection Î Percentage solute concentration reduction of

the permeate stream relative to the feed stream

Membrane technology Î basic terms

Solute Î Dissolved solids in raw, feed, permeate and

concentrate streams;

Solvent Î Liquid , usually water, containing disssolved

solids;

Flux Î mass rate or volume rate of transfer through a

membrane surface;

Scaling Î precipitation of solid material from the feed

stream in a membrane element;

Fouling Î Deposition of solid material from the feed

stream in a membrane element

MTC Î Mass or volume unit transfer through a

membrane based on driving force

Membrane technology fundamentals

Separation of solid particles using low-size porous

media;

Driving force of the process : pressure difference

between both sides of membranes

Basic types of membranes (by construction):

Hollow fiber (mostly for desalination), less subject to

fouling ;

Spiral wound (mostly for water treatment)

Basic type of membranes by size of pores (also by size

of components rejected), please note that with decrease

of size of rejected components a transmembrane

presssure decreases (TP Î a pressure necessary to transport

fluid throgh the membrane)

Size ranges

of membrane processes and contaminants

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