1. • IUPAC defines membrane fouling as “a
process resulting in loss of
performance of a membrane due to
the deposition of suspended or
dissolved substances on its
external surfaces, at its pore
openings or within pores”

2. • Fouling of membranes is the most important
problem in reverse osmosis desalination
• The process of formation of a deposited layer on
a membrane surface is called membrane fouling
and result in performance decline of the RO
system.
• Monitoring overall plant performance on a
regular basis is an essential step in recognizing
when membrane elements are becoming fouled.
Membrane Fouling

3. Adsorption :
• chemical affinity or interaction between solutes
and membrane material
• can happen at membrane surface or inside the
pores
• Adsorption is the gathering of gas, liquid, or
dissolved solids onto the surface of another
material
Mechanisms of Membrane Fouling

4. Adsorption

5. Plugging :
• Is caused by mechanical filtration in which particles
too large to pass through the feed-brine passage are
trapped in the device
• This problem should be most severe for a hollow
fiber device , because of the relative size of the feed-
brine flow channel
Mechanisms of Membrane Fouling

6. Plugging

7. Biofouling :
• Caused by bacterial adhesion and growth at
membrane surface
• Biofouling occur due to microbial attachment on
membrane surface followed by growth and
multiplication
• Biofouling is one of the most serious forms of
membrane fouling because once it forms; biofilm is
very difficult to remove
Mechanisms of Membrane Fouling

8. Biofouling

9. MEMBRANE FOULING
• Pretreatment system depends on feed water
quality
• During operation, the concentration of
suspended solids and dissolved ions increases
with a decreases volume of feed water
• The precipitated soluble salts from the
concentrate stream may form a scale on the
membrane surface and thus decrease water
permeability through the RO membranes

10. Membrane Fouling
• The process of forming a deposited layer on the
membrane surface is called membrane fouling.
• The consequence of membrane fouling is
reduction of permeate production rate and/or an
increase in salt passage across the membrane
with time
• Fouling may also cause increase in energy
consumption as trans-membrane pressure can
increase because of fouling

11. Membrane Fouling
• In addition fouling increase down time and may
shorten membrane life span.
• Fouling characterization is currently done
primarily by measuring the silt density index (SDI)
of feed water and monitoring the average
permeate flux of RO processes
• the SDI or related fouling indices have been
known not capable to catch all possible foulants
to RO membranes, and the average permeate flux
may fail to correctly reflect membrane fouling in
RO processes under certain circumstances.

12. FOULING & MEMBRANE PERFORMANCE
Depending on nature of the scale and foulant :
• Fouling processes will lead to decreased
membrane fluxes
• Increased pressures needs
• Increased permeate conductivity
• energy consumption increase

13. FOULING & MEMBRANE PERFORMANCE
• Membrane fouling will affect reverse osmosis
systems efficiency and result in increased
operational costs and energy consumption
• If membrane fouling is not effectively
controlled and the extent of fouling is so
severe that membrane cleaning fails to
reverse the decline in water production, plant
has to be shutdown and membrane
replacement has to be carried out.

14. CAUSE OF FOULING ON RO MEMBRANES
• Scaling
• Colloidal and particulate matter formation
• Dissolved organic substances
• Biological matter
• Metal Oxides

15. FACTORS AFFECTING MEMBRANE FOULING
Membrane fouling tendency depends mainly
on three major factors :
• Driving pressure
• Dimensions and physicochemical properties
of membrane channel
• Feed water characteristics