Membrane and Desalination Technologies - TCE Moodle Website

10 A.G. (Tony) Fane et al.
Table 1.2
Comparison between symmetric cellulose acetate (CA) membranes and polyamide
and polyurea composite membranes (adapted from ref. (21))
Advantages
Asymmetric CA membranes
l Chlorine-resistant
l Tolerant to oxidation
l Inexpensive
Disadvantages l Subject to hydrolysis
l Susceptible to biological attack
l Compaction at high pressures
l Narrow pH range (4.5–7.5)
l Lower upper temperature limits
( 35 C)
Pretreated
water
Highpressure
pump
Feed
control
valve
Polyamide and polyurea composite
membranes
l Higher water flux
l Higher salt and organic rejections
l Higher temperature and pH (4–11)
l Immune to biological attack and compaction
l Less chlorine-resistant
l Susceptible to oxidation
l More expensive
Bank of RO modules
Product
Concentrate Control
Valve
Concentrate
Fig. 1.7. Schematics of single-pass RO system (adapted from ref. (22)).
the presence of scale-formers, the flux of the membrane, the available pressure and the
desired flowrates. For a seawater system, the product recovery can be up to 50%.
The applications of RO technology for desalination and wastewater reclamation run
parallel to the development of the RO process. The world’s first commercial RO plant in
Coalinga, California, US, began operation in 1965 to produce pure water from brackish
groundwater at a capacity of up to 22.7 kL/day (6,000 gallon/day). A subsequent pilot plant
was constructed at La Jolla to extract fresh water from the sea (http://www.engineer.ucla.
edu/history/osmosis.html/). The first large RO plant with 18.9 MLD (5 MGD) of product
capacity to treat municipal wastewater, which was a part of the “Water Factory 21” in Orange
County, California, commenced operation in the late 1970s (23). By the end of 1990, the RO