The MBR Book: Principles and Applications of Membrane

exploitation index (WEI), the values of which represent the annual mean total demand
for freshwater divided by the long-term average freshwater resource. It provides an
indication of how the total water demand puts pressure on the water resource.
Data from the year 2000 indicate that four European countries (Cyprus, Italy,
Malta and Spain) representing 18% of Europe’s population, were considered to be
water stressed. It is estimated that, in 1990, around 1.9 billion people lived in countries
which used more than 20% of their potential water resources. By 2025, the
total population living in such water-stressed countries is expected to increase to 5.1
billion, this figure rising further to 6.5 billion by 2085. On the other hand, climaterelated
water stress is expected to reduce in some countries, for example, the USA
and China, while in central America, the Middle East, southern Africa, North Africa,
large areas of Europe and the Indian subcontinent, climate change is expected to
adversely increase water stress by the 2020s. It is also predicted that 2.4 billion people
will live in areas of extreme water stress (defined as using more than 40% of their
available water resources) by 2025, 3.1 billion by 2050 and 3.6 billion by 2085; this
is compared with a total population of 454 million in 1990 (Met Office, 2006).
1.4.5 Greater confidence in MBR technology
A growing confidence in MBR technology is demonstrated by the exponential
increase in the cumulative MBR installed capacity (Fig. 1.7). As existing wastewater
treatment plants become due for retrofit and upgrade – normally relating to a
requirement for increased capacity and/or improved effluent water quality without
incurring a larger footprint – it is expected that opportunities for the application of
MBR technologies will increase, particularly in the USA. It is also evident that MBR
installations are increasing in size year on year; the largest installation is currently
50 megalitres/day (MLD) with larger installations being planned and some observers
stating that plants of 300–800 MLD are feasible (DiGiano et al., 2004).
With new factors coming into play, the MBR technology is now beginning to
mature such that the market is expected to grow substantially over the next decade.
Evidence suggests that MBRs will continue to penetrate further the effluent treatment
market, with the number of players in the global market increasing. Currently,
the market is dominated by the two leading companies Zenon and Kubota. Whilst
the domination of these two companies is likely to continue in the short to medium
term, the global demand for the technology is such that a broader range of products is
likely to be sustainable in the future (Chapter 4), in particular if individual products
are tailored towards niche market applications.
1.5 Historical perspective
1.5.1 The early days of the MBR: the roots of the Kubota and Zenon systems
Introduction 11
The first membrane bioreactors were developed commercially by Dorr-Oliver in the
late 1960s (Bemberis et al., 1971), with application to ship-board sewage treatment