Membrane and Desalination Technologies - TCE Moodle Website

588 J.P. Chen et al.
Table 13.3
Summary of fouling factors and methods to clean and control
Fouling factors Effects on RO
performances
Methods for cleaning and
controlling fouling
Scales: Precipitation of soluble salts Major loss of salt Clean with citric acid or EDTA-
(minerals), for example, CaCO3, CaSO4, rejection
based solution
MgCO3, MgSO4, BaSO4, SrSO4, SiO2, Moderate increase Clean silicate-based foulants
Fe(OH) 3
in differential with ammonium bifluoride
pressure
solutions
Slight to moderate flow
loss
Reduce recovery
Effects usually occur Adjust pH
in last stage or
element
Use antiscalant
Colloids: Agglomeration of suspended Significant increase in Clean with chelants or
matter on the membrane surface, for differential pressure detergents at high pH
example, clay or silt particles, often Moderate flow loss Clean silicate-based foulants
organic and inorganic constituents
with ammonium bifluoride
solutions
Moderate loss of
rejection
Improve prefiltration
Effects usually occur Increase feed flow
in first stage or
element
Reduce recovery
Organics: Attachment of organics, for Rapid and significant Difficult to clean
example, fats, oils, grease, hydrocarbon flow loss
compounds, synthetic coagulants, and Stable or moderate Prefiltrate with granular active
flocculants
increase in salt
rejection
carbon
Generally, no or slight High pH soaks effective for
increase in
differential pressure
some organic types
Biological: Formation of bio-growth on Rapid and major loss Clean with commercial
membrane surface, for example, sulfur of production detergents or EDTA-based
reducing bacteria, mycobacterium
solutions at high pH
Moderate but rapidly Add solution bisulfate;
increasing
chlorinate with or without
differential pressure
Slight to moderate
increase in passage
Effects occur slowly
activated carbon filtration