Membrane and Desalination Technologies - TCE Moodle Website

530 J.P. Chen et al.
Table 12.2
Capital and operational costs of desalination processes
Nature of
technologies Technologies
Thermal
technologies
Membrane
technologies
Capital cost
(USD/m 3 /d)
Operational cost
(USD/m 3 )
MSF 1,200–3,000 0.7–1.5 (with waste heat)
MED 1,000–3,900 0.4–0.8 (with waste heat)
VC 1,000–1,300 0.5–1.2
RO 500–1,200 (brackish water) 0.2–1.2 (brackish water)
1,000–2,500 (seawater) 0.2–1.7 (seawater)
ED (EDR) 400–2,500 0.6–2.1
The cost for treating sea and brackish water by RO decreased by almost 50% from 1980 to
2005, because the cost of membrane materials dropped and prevention technologies of
membrane fouling were well developed. For example, desalination of seawater cost approximately
USD 1.5/m 3 production water in 1980, whereas the figure dropped to USD 0.8 in
2005. Over the last 50 years, the cost of freshwater production by MSF has decreased by an
average of 44% per decade (8).
Large-scale desalination projects are extremely expensive and often require some degree
of public financing. To build a 25-MGD plant, it costs 70–100 million USD. Thus, it becomes
more common that contractual arrangements of selling/purchase water between governments
and suppliers are made. The suppliers build and operate the plant. “Build, own, operate, and
transfer” and “build, operate, and transfer” are two typical arrangements. The first one
becomes more popular in developing countries, such as China.
Factors influencing selection of desalination technologies are many. The applicability of
desalination is very site specific. Site-specific conditions will also determine the type of
desalination technology selected (9). Financial issue is the first one to be solved. Both capital
investment and cost of daily operation are essential. As desalination requires high energy
input, energy requirement is an important issue. Selection of desalination process is highly
dependent upon source water characteristics; the quality and the quantity of product water
rely on them. Desalination plants should be close to the raw water source (e.g. sea) to obtain a
steady flow of raw water and to be able to discharge its byproducts easily. Limited land space
can be a major concern in the selection of desalination process. Desalination plants are
usually big and their accommodation could be a main cost factor that needs to be considered.
The plants that are built must have a large capacity in order to provide substantial amounts of
water. Environmental factors and waste disposal options are also important. Wastewater with
high salt content is produced. Handling the environmental problems is a great challenge and
principles of pollution prevention can be implemented. Finally, operational and maintenance
(O&M) issues must be considered. Training of operators is highly recommended.
Laws and regulations of federal, state, and local agencies play important roles in design
and operation of desalination projects. “Water Desalination Act of 1996,” “Pollution Prevention
Act of 1990,” and “Clean Water Act of 2002” regulate the projects at the federal level. In
addition, government policies have a great impact on costs of desalination.