Reverse Osmosis and Other Treatment Technologies - Global Drinking Water Management and Conservation - page 67

To summarize the cost of RO technology relative to the costs of other dominant
technologies used in freshwater production, we use Fig. 4.13 . This figure illustrates

the steadily decreasing real costs of RO desalination, as opposed to the volatile
changes in distillation costs, and the increasing costs of conventional water treat-
ment (non-desalination methods) from 1940 to 1985. It is shown that RO costs have
been rapidly falling over the past decades. In addition, brackish RO desalination
costs fell below the distillation costs in the 1970s, and could undercut the costs of
conventional water treatment.

4.5 Conclusion

The early US government support for R&D in desalination together with easy
access to the technology contributed to the long-lasting decrease in costs of desa-
lination. Due to the development of membrane technology and finally RO in the

early 1980s, desalination costs have fallen signi cantly and the forecast is a con-

tinued fall in costs over time in the near future. Based on this forecast, and the fact
that the costs of obtaining and treating water from conventional sources have been
increasing, we can expect that desalination costs will become competitive with
those of conventional water treatment processes and that RO and other membrane
methods will become competitive for freshwater production.
The technology that is the most economical of all the desalination methods is RO
technology (Mesa et al. 1996 ). Compared to other technologies, only distillation
can rival RO in seawater desalination, due to superior economies of scale and much
lower up-front investment costs. This, coupled with distillation

s maturity and
reputation for reliability (Winter et al. 2002 ), gave an early lead to distillation
plants. However, the new developments in RO manufacturing have now made it the
dominant method worldwide. RO plants are already replacing distillation plants all
over the world (Winter et al. 2002 ). RO has several advantages over other desa-
lination technologies including lower energy requirements, fewer problems with
corrosion, higher recovery rates for seawater, and less surface area for the same
amount of water production (Abulnour et al. 1983 ). The ability to produce potable
drinking water for signi

'

cantly less than $1.00 per m 3 (Mielke 1999 ) is by far its
greatest asset. In Singapore, the seawater RO plant, with a capacity to produce
136,000 m 3 /day, in operation since 2005, under a public-private scheme, is pro-
ducing desalted water at 0.78 US $/m 3 .
Desalination is shown to be the increasingly prefered method of freshwater
production and, especially as technical advancements of membrane processes
improve their costs and ef ciency, RO will continue to be the prefered choice for

countries moving into desalination (Winter et al. 2002 ). For this reason we have
chosen RO technology as the basis for the analysis of pricing and econometric
estimation of Ramsey Pricing, which follows in Chap. 5 .