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Chemical Technology • January 2016
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WATER TREATMENT
opportunities for more sustainable use of water, including
treating used water to standards that enable it to be used
again. They are well positioned to rapidly adopt conserva-
tion measures, and the concentration of people in compact
settlements can reduce the cost of providing services such as
water supply and sanitation. Furthermore, cities can connect
with their hinterlands and support the protection of water
resources in their surrounding areas by actively engaging in
watershedmanagement or providing Payment for Ecosystem/
environmental Services (PES).
Challenges
Access to water supply and sanitation
Rapid urbanisation, increased industrialisation, and improv-
ing living standards generally combine to increase the over-
all demand for water in cities. By 2050, global water demand
is projected to increase by 55 %, mainly due to growing
demand frommanufacturing, thermal electricity generation
and domestic use, all of which mainly results from growing
urbanisation in developing countries (Organisation for Eco-
nomic Co-operation and Development – OECD) [1].
As easily available surfacewater and groundwater sources
have been depleted inmany urbanised areas, cities will have
to go further or dig deeper to access water, or will have to
depend on innovative solutions or more advanced technolo-
gies such as reverse osmosis for desalination, or reclaimed
water to meet their water demands.
Although the Millennium Development Goals (MDG) tar-
get on access to safe drinking water – as measured by the
proportion of population using an improved drinking water
source (Pro-poor policies in Kampala: www-wds.worldbank.
org/external/default/WDSContentServer/WDSP/IB/2014
/02/24/000442464_20140224140639/) – was met in
2010, the progress in urban areas has not been able to
keep up with the rapid pace of urbanisation. Between 1990
and 2012, the number of urban residents who did not have
access to an improved drinking water source decreased
by 1 percentage point. However, in absolute terms, the
number of people in urban areas without access to an im-
proved drinking water source increased from 111 million to
149 million [2], indicating that access to drinking water
is actually deteriorating where the most rapid urbanisa-
tion is outpacing public services. The situation is worse in
sub-Saharan Africa, where urbanisation is happening most
rapidly. In this region, the percentage of people who enjoyed
piped water on their premises, which is the preferred option
for urban areas, actually decreased from 42 % to 34 % [2].
This clearly indicates that access to ‘safe’ drinking water
sources continues to be a major problem in cities in the
developing world.
Similar to trends in drinking water, the number of urban
residents without access to improved sanitation increased by
40 %, from 541 to 754 million, between 1990 and 2012 [2].
Therefore, although sanitation coverage is generally higher
in urban areas, because of rapid urbanisation, increasing
numbers of urban residents, particularly the poor, are unable
Rocinha Favela, Brazil. (Photo Ahln)