Membrane and Desalination Technologies - TCE Moodle Website

28 A.G. (Tony) Fane et al.
dropped more than 80% since the 1990s as a result of increased competition, better system
design, and lower manufacturing costs (123).
However, the application of MF/UF for NOM removal has been hindered due to serious
membrane fouling by NOM and organic aggregation in the presence of calcium (124, 125).
NOMs consist of a broad spectrum of molecular weights and size distributions, functional
groups and sub-structures, and have been shown to be the major foulant in the membrane
filtration of natural waters (126, 127). Substantial removal of NOM requires NF or low
pressure MF/UF coupled with coagulants or adsorbents such as powdered activated carbon
(PAC), which are the common practice in water and wastewater treatments (128–130).
Trace organics in surface or ground water, such as pesticides, herbicides, as well as tasteand-odor
causing materials, are not effectively removed by MF or UF processes because the
larger membrane pore size cannot retain the low molecular weight materials. Removal of
these hazardous contaminants from drinking water can be fulfilled by hybrid systems
combining either PAC adsorption or photocatalytic oxidation with membrane processes.
The trace organics are effectively separated from water by PAC (131, 132) or degraded by
oxidation using UV irradiation and TiO2 photocatalyst (133, 134). The fine PAC or TiO2
particles are efficiently retained by MF or UF membranes.
In many cases one membrane process is followed by another with the purpose of enhancing
the function of the other to meet goals ranging from disposal of wastewater to production of
drinking water from various sources. The application of MF or UF as a pretreatment for the
RO process is one example. This type of membrane application has been described in
Sect.3.1.2.
3.3. MBRs for Wastewater Treatments
MBR technology for wastewater treatment has experienced rapid development from the
early 1990s onwards. It has emerged as an effective solution to transform various wastewaters
into high quality effluents suitable for discharge or for reclamation by RO (135). Today, the
MBR market is predominated by submerged membrane modules with configurations of the
flat-sheet (or plate & frame) and hollow fibers, such as the Kubota Submerged Membrane
Unit, and GE-Zenon’s ZeeWeed 1 , ZenoGem 1 systems. The main suppliers of MBR systems
for wastewater treatment are Kubota (Japan), GE-Zenon (USA), Siemens-Memcor (USA)
and Mitsubishi Rayon (Japan). Other suppliers include Degremont (France), Wehrle Werk
(Germany), Hans Huber (Germany), Orelis Mitsui (Japan) and Koch (USA).
In Japan, since the first wastewater treatment plant with Kubota submerged MBR was
installed in 1990, there have been total 1,149 Kubota submerged membrane units applied in
wastewater treatment plants by 2003. The markets in South-East Asia and Japan are dominated
by the Kubota and Mitsubishi Royon. In the US, the first large-scale external MBR
system for treatment of industrial wastewater was constructed in 1991. Zenon Environmental
introduced the first ZenoGem 1 MBR process in the early 1990s. The first large-scale internal
MBR system for treatment of industrial wastewater was installed in 1998. The MBR market
in North America is currently dominated by Zenon. In Europe, The first pilot-scale submerged
MBR plant for municipal wastewater treatment was built at Kingston Seymour, UK