Combined Macromolecular Adsorption and Coagulation for Improvement of Membrane Separation in Water Treatment

  • Mohammed Al-Abri
  • Chedly Tizaoui
  • Nidal Hilal


Fouling is the biggest obstacle facing the operation of RO desalination plants. Seawater contains many foulants that foul RO membranes, such as suspended particles, natural organic matter (NOM), microorganisms, and heavy metals. Different processes such as coagulation, flocculation, acid treatment, pH adjustment, addition of anti-scalant, and media filtration have been used as conventional pretreatment. Nowadays, membrane systems are utilized for pretreatment because of their feasibility, process reliability, plant availability, modularity, relative insensitivity in case of raw water, and lower operating costs.

Natural organic matter and heavy metals are present in all water sources. They are of particular concern in desalination due to their toxicity and due to their effects on RO membrane fouling. Natural organic matter is a complex mixture of compounds formed from the breakdown of plant and animal material in the environment. Natural organic matter contains humic substances (HS) among other constituents. Heavy metals usually exist as free ions, but they also have a tendency of binding with HS. Consequently, heavy metals retention by ultrafiltration (UF) membranes is possible even though heavy metals have molecular sizes lower than the pore sizes of the membranes because of HS-metal complex formation.

In this study, P005F UF membrane retention of humic substances, Cu and Zn, and its fouling is investigated with and without the aid of poly diallydimethylammonium chloride (PDADMAC) and copolymer of dimethyl aminoethyl acrylate (CoAA) polyelectrolyte coagulants. The conditions studied are salinity level, humic substances (HS) concentration, heavy metals concentration, and polyelectrolyte’s type and concentration.


Humic Substance Heavy Metal Concentration Reverse Osmosis Natural Organic Matter Membrane Fouling 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



Permeate concentration (mg/l)


Bulk concentration (mg/l)


Wall concentration (mg/l)


Hydraulic membrane resistance (m−1)


Trans-membrane pressure (bar)


Pure water flux (L/m2.s1)


Permeate flux (L/m2.s)


Pure water flux after 30 min backwash (L/m2.s)


Mass transfer coefficient (L/m2.s)


Hydraulic diameter of the filtration channel (m)


Bulk diffusivity of solute (m2/s)


Gel layer resistance (m−1)


Gel concentration (mg/l)


Concentration polarization resistance (m−1)


Adsorption resistance (m−1)


Weak adsorption resistance (m−1)


Strong adsorption resistance (m−1)


Dynamic viscosity (kg/m/s) or (Pa.s)



The authors would like to thank the Middle East Desalination Research Center (MEDRC) for funding this work (project number 03-AS-02).


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Copyright information

© Springer Science+Business Media Dordrecht 2012

Authors and Affiliations

  1. 1.Petroleum and Chemical Engineering Department, College of EngineeringSultan Qaboos UniversityMuscatOman
  2. 2.Centre for Water Advanced Technologies and Environmental Research (CWATER), College of EngineeringSwansea UniversitySwanseaUK

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